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L_0607 | muscles and exercise | T_3192 | Anaerobic exercises comprise brief periods of physical exertion and high-intensity, strength-training activities. Anaerobic exercises cause muscles to get bigger and stronger. Anaerobic exercises use a resistance against which the muscle has to work to lift or push away. The resistance can be a weight or a persons own body weight (Figure | text | null |
L_0607 | muscles and exercise | T_3193 | Aerobic exercises are exercises in which a low to moderate level of exertion can be sustained over long periods. These are exercises that cause your heart to beat faster and allow your muscles to use oxygen to contract. If you exercise aerobically, overtime, your muscles will not get easily tired, and you will use oxygen more efficiently. Aerobic exercise (Figure 1.2) also helps improve cardiac muscle. | text | null |
L_0607 | muscles and exercise | T_3194 | Sometimes muscles and tendons get injured when a person starts doing an activity before they have warmed up properly. A warm up is a slow increase in the intensity of a physical activity that prepares muscles for an activity. Warming up increases the blood flow to the muscles and increases the heart rate. Warmed-up muscles and tendons are less likely to get injured. For example, before running or playing soccer, a person might jog slowly to warm muscles and increase their heart rate. Even elite athletes need to warm up (Figure 1.3). When you dont do a proper warm-up, several types of injuries can occur. A strain happens when muscle or tendons tear. Strains are also known as "pulled muscles." Another common injury is tendinitis, the irritation of the tendons. Strains and tendinitis are usually treated with rest, cold compresses, and stretching exercises that a physical therapist designs for each patient. Injuries can also be prevented by proper rest and recovery. If you do not get enough rest, your body will become injured and will not react well to exercise, or improve. You can also rest by doing a different activity. For example, if you run, you can rest your running muscles and joints by swimming. Warming up before the game helps the players avoid injuries. Some warm-ups may include stretching exercises. | text | null |
L_0608 | muscles bones and movement | T_3195 | When skeletal muscles contract, bones move. But how do muscles make your bones move? A voluntary muscles usually works across a joint. It is attached to both the bones on either side of the joint by strong cords called tendons. A tendon is a tough band of connective tissue that connects a muscle to a bone. Tendons are similar to ligaments, except that ligaments join bones to each other. Muscles move the body by contracting against the skeleton. When muscles contract, they get shorter. By contracting, muscles pull on bones and allow the body to move. Muscles can only contract. They cannot actively extend, though they can move or relax back into the non-contracted neutral position. Therefore, to move bones in opposite directions, pairs of muscles must work in opposition. Each muscle in the pair works against the other to move bones at the joints of the body. The muscle that contracts to cause a joint to bend is called the flexor. The muscle that contracts to cause the joint to straighten is called the extensor. When one muscle is contracted, the other muscle from the pair is always elongated. For example, the biceps and triceps muscles work together to allow you to bend and straighten your elbow. When you want to bend your elbow, your biceps muscle contracts (Figure 1.1), and, at the same time, the triceps muscle relaxes. The biceps is the flexor, and the triceps is the extensor of your elbow joint. Other muscles that work together are the quadriceps and hamstrings used to bend and straighten the knee, and the pectorals and trapezius used to move the arms and shoulders forward and backward. During daily routines we do not use muscles equally. For example, we use our biceps more than our triceps due to lifting against gravity. | text | null |
L_0608 | muscles bones and movement | T_3196 | Smooth muscles and cardiac muscles are not attached to bone. Recall that these types of muscles are under involuntary control. Smooth muscle is responsible for the contractility of hollow organs, such as blood vessels, the gastrointestinal tract, the bladder, or the uterus. Like skeletal muscles, smooth muscle fibers do contract together, causing the muscle to shorten. Smooth muscles have numerous functions, including the following. The smooth muscle in the uterus helps a woman to push out her baby. In the bladder, smooth muscle helps to push out urine. Smooth muscles move food through the digestive tract. In arteries, smooth muscle movements maintain the arteries diameter. Smooth muscle regulates air flow in lungs. Smooth muscle in the lungs helps the airways to expand and contract as necessary. Smooth muscles in arteries and veins are largely responsible for regulation of blood pressure. Cardiac muscle also contracts and gets shorter. This muscle is found only in the heart. The sudden burst of contraction forces blood throughout your body. When the cardiac muscle relaxes, the heart fills with blood. This rhythmic contraction must continue for your whole life, luckily the heart muscle never gets tired. If your heart beats 75 times a minute, how many times does it beat in an hour? A day? A year? 85 years? | text | null |
L_0609 | mutations | T_3197 | The process of DNA replication is not always 100% accurate. Sometimes the wrong base is inserted in the new strand of DNA. This wrong base could become permanent. A permanent change in the sequence of DNA is known as a mutation. Small changes in the DNA sequence are usually point mutations, which is a change in a single nucleotide. Once DNA has a mutation, that mutation will be copied each time the DNA replicates. After cell division, each resulting cell will carry the mutation. A mutation may have no effect. However, sometimes a mutation can cause a protein to be made incorrectly. A defect in the protein can affect how well the protein works, or whether it works at all. Usually the loss of a protein function is detrimental to the organism. In rare circumstances, though, the mutation can be beneficial. Mutations are a mechanism for how species evolve. For example, suppose a mutation in an animals DNA causes the loss of an enzyme that makes a dark pigment in the animals skin. If the population of animals has moved to a light colored environment, the animals with the mutant gene would have a lighter skin color and be better camouflaged. So in this case, the mutation is beneficial. | text | null |
L_0609 | mutations | T_3198 | If a single base is deleted (called a deletion, which is also a point mutation), there can be huge effects on the organism, because this may cause a frameshift mutation. Remember that the bases in the mRNA are read in groups of three by the tRNA. If the reading frame is off by even one base, the resulting sequence will consist of an entirely different set of codons. The reading of an mRNA is like reading three-letter words of a sentence. Imagine the sentence: The big dog ate the red cat. If you take out the second letter from "big," the frame will be shifted so now it will read: The bgd oga tet her edc at. One single deletion makes the whole sentence impossible to read. A point mutation that adds a base (known as an insertion) would also result in a frameshift. | text | null |
L_0609 | mutations | T_3199 | Mutations may also occur in chromosomes ( Figure 1.1). These mutations are going to be fairly large mutations, possible affecting many genes. Possible types of mutations in chromosomes include: 1. Deletion: When a segment of DNA is lost, so there is a missing segment in the chromosome. These usually result in many genes missing from the chromosome. 2. Duplication: When a segment of DNA is repeated, creating a longer chromosome. These usually result in multiple copies of genes in the chromosome. 3. Inversion: When a segment of DNA is flipped and then reattached to the same chromosome. 4. Insertion: When a segment of DNA from one chromosome is added to another, unrelated chromosome. 5. Translocation: When two segments from different chromosomes change positions. | text | null |
L_0609 | mutations | T_3200 | Many mutations are not caused by errors in replication. Mutations can happen spontaneously, and they can be caused by mutagens in the environment. Some chemicals, such as those found in tobacco smoke, can be mutagens. Sometimes mutagens can also cause cancer. Tobacco smoke, for example, is often linked to lung cancer. | text | null |
L_0610 | nails and hair | T_3201 | Along with the skin, the integumentary system includes the nails and hair. Both the nails and hair contain the tough protein, keratin. The keratin forms fibers, which makes your nails and hair tough and strong. Keratin is similar in toughness to chitin, the carbohydrate found in the exoskeleton of arthropods. | text | null |
L_0610 | nails and hair | T_3202 | Nails are similar to claws in other animals. They cover the tips of fingers and toes. Fingernails and toenails both grow from nail beds. As the nail grows, more cells are added at the nail bed. Older cells get pushed away from the nail bed and the nail grows longer. There are no nerve endings in the nail. Otherwise cutting your nails would hurt a lot! Nails act as protective plates over the fingertips and toes. Fingernails also help in sensing the environment. The area under your nail has many nerve endings. These nerve endings allow you to receive more information about objects you touch. The Guinness Book of World Records began tracking record fingernail lengths in 1955. At that time the record was 1 foot 10.75 inches long. The current record-holder for men is from India, with a record of 20 feet 2.25 inches for all nails on his left hand, the longest being his thumbnail at 4 feet 9.6 inches. The record for women is held by an American woman. The record is 28 feet (850 cm) for all nails of both hands, with the longest nail on her right thumb at 2 feet 11 inches. Since adult nails grow at about 3 mm a month (1/10 of an inch), how long would it take to grow such long nails? | text | null |
L_0610 | nails and hair | T_3203 | Hair is one of the defining characteristics of mammals. In fact, mammals are the only animals to have hair. Hair sticks out from the epidermis, but it grows from the dermis ( Figure 1.1). Hair grows from inside the hair follicle. New cells grow in the bottom part of the hair, called the bulb. Older cells get pushed up, and the hair grows longer. The cells that make up the hair strand are dead and filled with the rope-like protein keratin. Hair, hair follicle, and oil glands. The oil, called sebum, helps to prevent water loss from the skin. The sebaceous gland secretes sebum, which waterproofs the skin and hair. In humans, hair grows everywhere on the body except the soles of the feet and the palms of the hands, the lips, and the eyelids (except for eyelashes). Hair grows at a rate of about half an inch (1.25 cm) each month, or about 6 inches (15 cm) a year. Hair, especially on the head, helps to keep the body warm. The air traps a layer of warm air near the skin and acts like a warm blanket. Hair can also act as a filter. Nose hair helps to trap particles in the air that may otherwise travel to the lungs. Eyelashes shield eyes from dust and sunlight. Eyebrows stop salty sweat and rain from flowing into the eye. The worlds longest documented hair, according to Guinness World Records, belongs to Xie Qiuping of China at just under 18 feet 6 inches (5.627 m) when measured on May 8, 2004. She had been growing her hair since 1973 when she was 13 years old. | text | null |
L_0613 | nervous system | T_3210 | Michelle was riding her scooter when she hit a hole in the street and started to lose control. She thought she would fall, but, in the blink of an eye, she shifted her weight and kept her balance. Her heart was pounding, but at least she didnt get hurt. How was she able to react so quickly? Michelle can thank her nervous system for that ( Figure 1.1). The nervous system, together with the endocrine system, controls all the other organ systems. The nervous system sends one type of signal around the body, and the endocrine system sends another type of signal around the body. The endocrine system makes and releases chemical messenger molecules, or hormones, which tell other body parts that a change or a reaction is necessary. So what type of signal does the nervous system send? Controlling muscles and maintaining balance are just two of the roles of the nervous system. The nervous system also lets you: Sense your surroundings with your eyes and other sense organs. Sense the environment inside of your body, including temperature. Control your internal body systems and keep them in balance. Staying balanced when riding a scooter requires control over the bodys muscles. The nervous system controls the muscles and maintains balance. Prepare your body to fight or flee in an emergency. Use language, think, learn, and remember. The nervous system works by sending and receiving electrical signals. The main organs of the nervous system are the brain and the spinal cord. The signals are carried by nerves in the body, similar to the wires that carry electricity all over a house. The signals travel from all over the body to the spinal cord and up to the brain, as well as moving in the other direction. For example, when Michelle started to fall off her scooter, her nervous system sensed that she was losing her balance. It responded by sending messages from her brain to muscles in her body. Some muscles tightened while others relaxed. Maybe these actions moved her hips or her arms. The nervous system, working together with the muscular and skeletal systems, allowed Michelle to react to the situation. As a result, Michelles body became balanced again. The messages released by the nervous system traveled through nerves. Just like the electricity that travels through wires, nerve quickly carry the electrical messages around the body. Think about how quickly all this happens. It has to be really fast, otherwise Michelle would not have been able to react. What would happen if a car pulled out unexpectedly in front of Michelle? A signal would have to go from her eyes to her brain and then to her muscles. What allows the nervous system to react so fast. It starts with the special cell of the nervous system, the neuron. | text | null |
L_0614 | non infectious reproductive system disorders | T_3211 | Many disorders of the reproductive system are not sexually transmitted infections. They are not caused by pathogens, so they dont spread from person to person. They develop for other reasons. The disorders are different between males and females. In both genders, the disorders could cause a little discomfort, or they could cause death. | text | null |
L_0614 | non infectious reproductive system disorders | T_3212 | Most common disorders of the male reproductive system involve the testes. For example, injuries to the testes are very common. In teenagers, injuries to the testes most often occur while playing sports. An injury such as a strike or kick to the testes can be very painful. It may also cause bruising and swelling. Such injuries do not usually last very long. Another disorder of the testes is cancer. Cancer of the testes is most common in males aged 15 to 35. It occurs when cells in the testes grow out of control. The cells form a lump called a tumor. If found early, cancer of the testes usually can be easily cured with surgery. | text | null |
L_0614 | non infectious reproductive system disorders | T_3213 | Disorders of the female reproductive system may affect the vagina, uterus, or ovaries. They may also affect the breasts. One of the most common disorders is vaginitis. This is redness and itching of the vagina. It may be due to irritation by soap or bubble bath. Another possible cause of vaginitis is a yeast infection. Yeast normally grow in the vagina. A yeast infection happens when the yeast multiply too fast and cause symptoms. A yeast infection can be treated with medication. Bubble baths may be fun, but for women and girls they can cause irritation to the vagina. A common disorder of the ovaries is an ovarian cyst. A cyst is a sac filled with fluid or other material. An ovarian cyst is usually harmless, but it may cause pain. Most cysts slowly disappear and do not need treatment. Very large or painful cysts can be removed with surgery. Many teen girls have painful menstrual periods. They typically have cramping in the lower abdomen. Generally, this is nothing to worry about. Taking a warm bath or using a heating pad often helps. Exercise can help as well. A pain reliever like ibuprofen may also work. If the pain is severe, a doctor can prescribe stronger medicine to relieve the pain. The most common type of cancer in females is breast cancer. The cancer causes the cells of the breast to grow out of control and form a tumor. Breast cancer is rare in teens. It becomes more common as women get older. If breast cancer is found early, it usually can be cured with surgery. | text | null |
L_0616 | nonrenewable resources | T_3217 | A nonrenewable resource is a natural resource that is consumed or used up faster than it can be made by nature. Two main types of nonrenewable resources are fossil fuels and nuclear power. Fossil fuels, such as petroleum, coal, and natural gas, formed from plant and animal remains over periods from 50 to 350 million years ago. They took millions of years to form. Humans have been consuming fossil fuels for less than 200 years, yet remaining reserves of oil can supply our needs only until around the year 2055. Natural gas can only supply us until around 2085. Coal will last longer, until around the year 2250. That is why it is so important to develop alternate forms of energy, especially for our cars. Today, electric cars are becoming more and more common. Considering the year 2055 is not that far away, what would happen if we ran out of gasoline? Alternative use of energy, especially in transportation, must become a standard feature of all cars and trucks and planes by the middle of the century. Nuclear power is the use of nuclear energy ( nuclear fission) to create energy inside of a nuclear reactor ( Figure uranium fuel supplies, which will last to about the year 2100 (or longer) at current rates of use. However, new technologies could make some uranium fuel reserves more useful. Population growth, especially in developing countries, should make people think about how fast they are consuming resources. Governments around the world should seriously consider these issues. Developing nations will also increase demands on natural resources as they build more factories ( Figure 1.2). Improvements in technology, conservation of resources, and controls in population growth could all help to decrease the demand on natural resources. Aerial photo of the Bruce Nuclear Gener- ating Station near Kincardine, Ontario. Per capita energy consumption (2003) shows the unequal distribution of wealth, technology, and energy use. | text | null |
L_0616 | nonrenewable resources | T_3217 | A nonrenewable resource is a natural resource that is consumed or used up faster than it can be made by nature. Two main types of nonrenewable resources are fossil fuels and nuclear power. Fossil fuels, such as petroleum, coal, and natural gas, formed from plant and animal remains over periods from 50 to 350 million years ago. They took millions of years to form. Humans have been consuming fossil fuels for less than 200 years, yet remaining reserves of oil can supply our needs only until around the year 2055. Natural gas can only supply us until around 2085. Coal will last longer, until around the year 2250. That is why it is so important to develop alternate forms of energy, especially for our cars. Today, electric cars are becoming more and more common. Considering the year 2055 is not that far away, what would happen if we ran out of gasoline? Alternative use of energy, especially in transportation, must become a standard feature of all cars and trucks and planes by the middle of the century. Nuclear power is the use of nuclear energy ( nuclear fission) to create energy inside of a nuclear reactor ( Figure uranium fuel supplies, which will last to about the year 2100 (or longer) at current rates of use. However, new technologies could make some uranium fuel reserves more useful. Population growth, especially in developing countries, should make people think about how fast they are consuming resources. Governments around the world should seriously consider these issues. Developing nations will also increase demands on natural resources as they build more factories ( Figure 1.2). Improvements in technology, conservation of resources, and controls in population growth could all help to decrease the demand on natural resources. Aerial photo of the Bruce Nuclear Gener- ating Station near Kincardine, Ontario. Per capita energy consumption (2003) shows the unequal distribution of wealth, technology, and energy use. | text | null |
L_0619 | organic compounds | T_3223 | The main chemical components of living organisms are known as organic compounds. Organic compounds are molecules built around the element carbon (C). Living things are made up of very large molecules. These large molecules are called macromolecules because macro means large; they are made by smaller molecules bonding together. Our body gets these smaller molecules, the "building blocks" or monomers, of organic molecules from the food we eat. Which organic molecules do you recognize from the list below? The four main types of macromolecules found in living organisms, shown in Table 1.1, are: 1. 2. 3. 4. Proteins. Carbohydrates. Lipids. Nucleic Acids. Proteins C, H, O, N, S Enzymes, muscle fibers, antibodies Elements Examples Monomer building molecule) (small block Amino acids Carbohydrates C, H, O Sugar, glucose, starch, glycogen, cellulose Monosaccharides (simple sugars) Lipids C, H, O, P Fats, oils, waxes, steroids, phospho- lipids in membranes Often include fatty acids Nucleic Acids C, H, O, P, N DNA, RNA, ATP Nucleotides | text | null |
L_0619 | organic compounds | T_3224 | Carbohydrates are sugars, or long chains of sugars. An important role of carbohydrates is to store energy. Glucose ( Figure 1.1) is an important simple sugar molecule with the chemical formula C6 H12 O6 . Simple sugars are known as monosaccharides. Carbohydrates also include long chains of connected sugar molecules. These long chains often consist of hundreds or thousands of monosaccharides bonded together to form polysaccharides. Plants store sugar in polysaccharides called starch. Animals store sugar in polysaccharides called glycogen. You get the carbohydrates you need for energy from eating carbohydrate-rich foods, including fruits and vegetables, as well as grains, such as bread, rice, or corn. A molecule of glucose, a type of carbohy- drate. | text | null |
L_0619 | organic compounds | T_3225 | Proteins are molecules that have many different functions in living things. All proteins are made of monomers called amino acids ( Figure 1.2) that connect together like beads on a necklace ( Figure 1.3). There are only 20 common amino acids needed to build proteins. These amino acids form in thousands of different combinations, making about 100,000 or more unique proteins in humans. Proteins can differ in both the number and order of amino acids. It is the number and order of amino acids that determines the shape of the protein, and it is the shape (structure) of the protein that determines the unique function of the protein. Small proteins have just a few hundred amino acids. The largest proteins have more than 25,000 amino acids. This model shows the general structure of all amino acids. Only the side chain, R, varies from one amino acid to another. KEY: H = hydrogen, N = nitrogen, C = carbon, O = oxygen, R = variable side chain. Many important molecules in your body are proteins. Examples include enzymes, antibodies, and muscle fiber. Enzymes are a type of protein that speed up chemical reactions. They are known as "biological catalysts." For example, your stomach would not be able to break down food if it did not have special enzymes to speed up the rate of digestion. Antibodies that protect you against disease are proteins. Muscle fiber is mostly protein ( Figure 1.4). Muscle fibers are made mostly of protein. Its important for you and other animals to eat food with protein, because we cannot make certain amino acids on our own. You can get proteins from plant sources, such as beans, and from animal sources, like milk or meat. When you eat food with protein, your body breaks the proteins down into individual amino acids and uses them to build new proteins. You really are what you eat! | text | null |
L_0619 | organic compounds | T_3225 | Proteins are molecules that have many different functions in living things. All proteins are made of monomers called amino acids ( Figure 1.2) that connect together like beads on a necklace ( Figure 1.3). There are only 20 common amino acids needed to build proteins. These amino acids form in thousands of different combinations, making about 100,000 or more unique proteins in humans. Proteins can differ in both the number and order of amino acids. It is the number and order of amino acids that determines the shape of the protein, and it is the shape (structure) of the protein that determines the unique function of the protein. Small proteins have just a few hundred amino acids. The largest proteins have more than 25,000 amino acids. This model shows the general structure of all amino acids. Only the side chain, R, varies from one amino acid to another. KEY: H = hydrogen, N = nitrogen, C = carbon, O = oxygen, R = variable side chain. Many important molecules in your body are proteins. Examples include enzymes, antibodies, and muscle fiber. Enzymes are a type of protein that speed up chemical reactions. They are known as "biological catalysts." For example, your stomach would not be able to break down food if it did not have special enzymes to speed up the rate of digestion. Antibodies that protect you against disease are proteins. Muscle fiber is mostly protein ( Figure 1.4). Muscle fibers are made mostly of protein. Its important for you and other animals to eat food with protein, because we cannot make certain amino acids on our own. You can get proteins from plant sources, such as beans, and from animal sources, like milk or meat. When you eat food with protein, your body breaks the proteins down into individual amino acids and uses them to build new proteins. You really are what you eat! | text | null |
L_0619 | organic compounds | T_3225 | Proteins are molecules that have many different functions in living things. All proteins are made of monomers called amino acids ( Figure 1.2) that connect together like beads on a necklace ( Figure 1.3). There are only 20 common amino acids needed to build proteins. These amino acids form in thousands of different combinations, making about 100,000 or more unique proteins in humans. Proteins can differ in both the number and order of amino acids. It is the number and order of amino acids that determines the shape of the protein, and it is the shape (structure) of the protein that determines the unique function of the protein. Small proteins have just a few hundred amino acids. The largest proteins have more than 25,000 amino acids. This model shows the general structure of all amino acids. Only the side chain, R, varies from one amino acid to another. KEY: H = hydrogen, N = nitrogen, C = carbon, O = oxygen, R = variable side chain. Many important molecules in your body are proteins. Examples include enzymes, antibodies, and muscle fiber. Enzymes are a type of protein that speed up chemical reactions. They are known as "biological catalysts." For example, your stomach would not be able to break down food if it did not have special enzymes to speed up the rate of digestion. Antibodies that protect you against disease are proteins. Muscle fiber is mostly protein ( Figure 1.4). Muscle fibers are made mostly of protein. Its important for you and other animals to eat food with protein, because we cannot make certain amino acids on our own. You can get proteins from plant sources, such as beans, and from animal sources, like milk or meat. When you eat food with protein, your body breaks the proteins down into individual amino acids and uses them to build new proteins. You really are what you eat! | text | null |
L_0619 | organic compounds | T_3226 | Have you ever tried to put oil in water? They dont mix. Oil is a type of lipid. Lipids are molecules such as fats, oils, and waxes. The most common lipids in your diet are probably fats and oils. Fats are solid at room temperature, whereas oils are fluid. Animals use fats for long-term energy storage and to keep warm. Plants use oils for long- term energy storage. When preparing food, we often use animal fats, such as butter, or plant oils, such as olive oil or canola oil. There are many more type of lipids that are important to life. One of the most important are the phospholipids that make up the protective outer membrane of all cells ( Figure 1.5). These lipid membranes are impermeable to most water soluble compounds. | text | null |
L_0619 | organic compounds | T_3227 | Nucleic acids are long chains of nucleotides. Nucleotides are made of a sugar, a nitrogen-containing base, and a phosphate group. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two main nucleic acids. DNA is a double-stranded nucleic acid. DNA is the molecule that stores our genetic information ( Figure 1.6). The single- stranded RNA is involved in making proteins. ATP (adenosine triphosphate), known as the "energy currency" of the cell, is also a nucleic acid. | text | null |
L_0621 | organization of the human body | T_3232 | Cells are grouped together to carry out specific functions. A group of cells that work together form a tissue. Your body has four main types of tissues, as do the bodies of other animals. These tissues make up all structures and contents of your body. An example of each tissue type is pictured in the Figure 1.1. Your body has four main types of tissue: nervous tissue, epithelial tissue, connective tissue, and muscle tissue. They are found throughout your body. 1. Epithelial tissue is made up of layers of tightly packed cells that line the surfaces of the body. Examples of epithelial tissue include the skin, the lining of the mouth and nose, and the lining of the digestive system. 2. Connective tissue is made up of many different types of cells that are all involved in supporting and binding other tissues of the body. Examples include tendon, cartilage, and bone. Blood is also classified as a specialized connective tissue. 3. Muscle tissue is made up of bands of cells that contract and allow movement. 4. Nervous tissue is made up of nerve cells that sense stimuli and transmit signals. Nervous tissue is found in nerves, the spinal cord, and the brain. | text | null |
L_0621 | organization of the human body | T_3233 | A single tissue alone cannot do all the jobs that are needed to keep you alive and healthy. Two or more tissues working together can do a lot more. An organ is a structure made of two or more tissues that work together. The heart ( Figure 1.2) is made up of the four types of tissues. The four different tissue types work to- gether in the heart as they do in the other organs. | text | null |
L_0621 | organization of the human body | T_3234 | Your heart pumps blood around your body. But how does your heart get blood to and from every cell in your body? Your heart is connected to blood vessels such as veins and arteries. Organs that work together form an organ system. Together, your heart, blood, and blood vessels form your cardiovascular system. What other organ systems can you think of? | text | null |
L_0621 | organization of the human body | T_3235 | Your bodys 12 organ systems are shown below ( Table 1.1). Your organ systems do not work alone in your body. They must all be able to work together. For example, one of the most important functions of organ systems is to provide cells with oxygen and nutrients and to remove toxic waste products such as carbon dioxide. A number of organ systems, including the cardiovascular and respiratory systems, all work together to do this. Organ System Cardiovascular Major Tissues and Organs Heart; blood vessels; blood Lymphatic Lymph nodes; lymph vessels Digestive Esophagus; stomach; small intes- tine; large intestine Pituitary gland, hypothalamus; adrenal glands; ovaries; testes Endocrine Function Transports oxygen, hormones, and nutrients to the body cells. Moves wastes and carbon dioxide away from cells. Defend against infection and dis- ease, moves lymph between tissues and the blood stream. Digests foods and absorbs nutrients, minerals, vitamins, and water. Produces hormones that communi- cate between cells. Organ System Integumentary Major Tissues and Organs Skin, hair, nails Muscular Cardiac (heart) muscle; skeletal muscle; smooth muscle; tendons Brain, spinal cord; nerves Nervous Reproductive Respiratory Female: uterus; vagina; fallopian tubes; ovaries Male: penis; testes; seminal vesi- cles Trachea, larynx, pharynx, lungs Skeletal Bones, cartilage; ligaments Urinary Kidneys; urinary bladder Immune Bone marrow; spleen; white blood cells Function Provides protection from injury and water loss, physical defense against infection by microorganisms, and temperature control. Involved in movement and heat pro- duction. Collects, transfers, and processes information. Produces gametes (sex cells) and sex hormones. Brings air to sites where gas ex- change can occur between the blood and cells (around body) or blood and air (lungs). Supports and protects soft tissues of body; produces blood cells; stores minerals. Removes extra water, salts, and waste products from blood and body; controls pH; controls water and salt balance. Defends against diseases. | text | null |
L_0623 | origins of life | T_3241 | There is good evidence that life has probably existed on Earth for most of Earths history. Fossils of blue-green algae found in Australia are the oldest fossils of life forms on Earth. They are at least 3.5 billion years old ( Figure 1.1). | text | null |
L_0623 | origins of life | T_3242 | How did life begin? In order to answer this question, scientists need to know what kinds of materials were available at that time. We know that the ingredients for life were present at the beginning of Earths history. Scientists believe early Earth did not contain oxygen gas (photosynthesis had yet to evolve), but did contain other gases, including: nitrogen gas, carbon dioxide, carbon monoxide, water vapor, hydrogen sulfide. Some of the oldest fossils on Earth were found along the coast of Australia, similar to the area shown here. Where did these ingredients come from? Some chemicals were in water and volcanic gases ( Figure 1.2). Other chemicals would have come from meteorites in space. Energy to drive chemical reactions was provided by volcanic eruptions and lightning. Today, we have evidence that life on Earth came from random reactions between chem- ical compounds, which formed molecules, or groups of atoms bonded together. Small molecules, such as those present in the early atmosphere, can provide the components (including the elements C, H, N, O and S) to make larger molecules. These early molecules further reacted and eventually formed even larger molecules and organic compounds, such as amino acids (which combine to form proteins), and nucleotides (which form nucleic acids - RNA or DNA). These organic molecules eventually came together in the right combinations to form basic cells. The components that were necessary for the formation of the first cells are still being studied. How long did it take to develop the first life forms? As much as 1 billion years. Many scientists still study the origin of the first life forms because there are many questions left unanswered, such as, "Did proteins or nucleic acids develop first?" or "What exactly were early Earths atmospheric conditions like?" There is a lot of work still left to answer these and similar questions. Some clues to the origins of life on Earth come from studying the early life forms that developed in hot springs, such as the Grand Prismatic Spring at Yellowstone National Park. This spring is approxi- mately 250 feet deep and 300 feet wide. | text | null |
L_0623 | origins of life | T_3242 | How did life begin? In order to answer this question, scientists need to know what kinds of materials were available at that time. We know that the ingredients for life were present at the beginning of Earths history. Scientists believe early Earth did not contain oxygen gas (photosynthesis had yet to evolve), but did contain other gases, including: nitrogen gas, carbon dioxide, carbon monoxide, water vapor, hydrogen sulfide. Some of the oldest fossils on Earth were found along the coast of Australia, similar to the area shown here. Where did these ingredients come from? Some chemicals were in water and volcanic gases ( Figure 1.2). Other chemicals would have come from meteorites in space. Energy to drive chemical reactions was provided by volcanic eruptions and lightning. Today, we have evidence that life on Earth came from random reactions between chem- ical compounds, which formed molecules, or groups of atoms bonded together. Small molecules, such as those present in the early atmosphere, can provide the components (including the elements C, H, N, O and S) to make larger molecules. These early molecules further reacted and eventually formed even larger molecules and organic compounds, such as amino acids (which combine to form proteins), and nucleotides (which form nucleic acids - RNA or DNA). These organic molecules eventually came together in the right combinations to form basic cells. The components that were necessary for the formation of the first cells are still being studied. How long did it take to develop the first life forms? As much as 1 billion years. Many scientists still study the origin of the first life forms because there are many questions left unanswered, such as, "Did proteins or nucleic acids develop first?" or "What exactly were early Earths atmospheric conditions like?" There is a lot of work still left to answer these and similar questions. Some clues to the origins of life on Earth come from studying the early life forms that developed in hot springs, such as the Grand Prismatic Spring at Yellowstone National Park. This spring is approxi- mately 250 feet deep and 300 feet wide. | text | null |
L_0624 | outdoor air pollution | T_3243 | Air is all around us. Air is essential for life. Sometimes, humans can pollute the air. For example, releasing smoke and dust from factories and cars can cause air pollution. Air pollution is due to chemical substances and particles released into the air mainly by human actions. This pollution affects entire ecosystems around the world. Pollution can also cause many human health problems, and it can also cause death. Air pollution can be found both outdoors and indoors. Outdoor air pollution is made of chemical particles. When smoke or other pollutants enter the air, the particles found in the pollution mix with the air. Air is polluted when it contains many large toxic particles. Outdoor air pollution changes the natural characteristics of the atmosphere. Primary pollutants are added directly to the atmosphere. Fires add primary pollutants to the air. Particles released from the fire directly enter the air and cause pollution ( Figure 1.1). Burning of fossil fuels such as oil and coal is a major source of primary pollutants ( Figure Secondary pollutants are formed when primary pollutants interact with sunlight, air, or each other. They do not directly cause pollution. However, when they interact with other parts of the air, they do cause pollution. For example, ozone is created when some pollutants interact with sunlight. High levels of ozone in the atmosphere can cause problems for humans. Wildfires, either natural or human-caused, release particles into the air, one of the many causes of air pollution. A major source of air pollution is the burn- ing of fossil fuels from factories, power plants, and motor vehicles. | text | null |
L_0624 | outdoor air pollution | T_3243 | Air is all around us. Air is essential for life. Sometimes, humans can pollute the air. For example, releasing smoke and dust from factories and cars can cause air pollution. Air pollution is due to chemical substances and particles released into the air mainly by human actions. This pollution affects entire ecosystems around the world. Pollution can also cause many human health problems, and it can also cause death. Air pollution can be found both outdoors and indoors. Outdoor air pollution is made of chemical particles. When smoke or other pollutants enter the air, the particles found in the pollution mix with the air. Air is polluted when it contains many large toxic particles. Outdoor air pollution changes the natural characteristics of the atmosphere. Primary pollutants are added directly to the atmosphere. Fires add primary pollutants to the air. Particles released from the fire directly enter the air and cause pollution ( Figure 1.1). Burning of fossil fuels such as oil and coal is a major source of primary pollutants ( Figure Secondary pollutants are formed when primary pollutants interact with sunlight, air, or each other. They do not directly cause pollution. However, when they interact with other parts of the air, they do cause pollution. For example, ozone is created when some pollutants interact with sunlight. High levels of ozone in the atmosphere can cause problems for humans. Wildfires, either natural or human-caused, release particles into the air, one of the many causes of air pollution. A major source of air pollution is the burn- ing of fossil fuels from factories, power plants, and motor vehicles. | text | null |
L_0624 | outdoor air pollution | T_3244 | Most air pollutants can be traced to the burning of fossil fuels. Fossil fuels are burned during many processes, including in power plants to create electricity, in factories to make machinery run, in power stoves and furnaces for heating, and in waste facilities. Perhaps one of the biggest uses of fossil fuels is in transportation. Fossil fuels are used in cars, trains, and planes. Air pollution can also be caused by agriculture, such as cattle ranching and the use of fertilizers and pesticides. Other sources of air pollution include the production of plastics, refrigerants, and aerosols, in nuclear power and defense, from landfills and mining, and from biological warfare. | text | null |
L_0624 | outdoor air pollution | T_3245 | One result of air pollution is acid rain. Acid rain is precipitation with a low (acidic) pH. This rain can be very destructive to wildlife. When acid rain falls in forests, freshwater habitats, or soils, it can kill insects and aquatic life. It causes this damage because of its very low pH. Sulfur oxides and nitrogen oxides in the air both cause acid rain to form ( Figure 1.3). Sulfur oxides are chemicals that are released from coal-fired power plants. Nitrogen oxides are released from motor vehicle exhaust. A forest in the Jizera Mountains of the Czech Republic shows effects caused by acid rain. What do you observe? | text | null |
L_0624 | outdoor air pollution | T_3246 | Pollutants also affect the atmosphere through their contribution to global warming. Global warming is an increase in the Earths temperature. It is thought to be caused mostly by the increase of greenhouse gases like carbon dioxide. Greenhouse gases can be released by factories that burn fossil fuels. Over the past 20 years, burning fossil fuels has produced about three-quarters of the carbon dioxide from human activity. The rest of the carbon dioxide in the atmosphere is there because of deforestation, or cutting down trees ( Figure 1.4). Trees absorb carbon dioxide during cellular respiration, so when trees are cut down, they cannot remove carbon dioxide from the air. This increase in global temperature will cause the sea level to rise. It is also expected to produce an increase in extreme weather events and change the amount of precipitation. Global warming may also cause food shortages and species extinction. | text | null |
L_0626 | pathogens | T_3250 | Has this ever happened to you? A student sitting next to you in class has a cold. The other student is coughing and sneezing, but you feel fine. Two days later, you come down with a cold, too. Diseases like colds are contagious. Contagious diseases are also called infectious diseases. An infectious disease is a disease that spreads from person to person. Infectious diseases are caused by pathogens. A pathogen is a living thing or virus that causes disease. Pathogens are commonly called germs. They can travel from one person to another. | text | null |
L_0626 | pathogens | T_3251 | Living things that cause human diseases include bacteria, fungi, and protozoa. Most infectious diseases caused by these organisms can be cured with medicines. For example, medicines called antibiotics can cure most diseases caused by bacteria. Bacteria are one-celled organisms without a nucleus. Although most bacteria are harmless, some cause diseases. Worldwide, the most common disease caused by bacteria is tuberculosis (TB). TB is a serious disease of the lungs. Another common disease caused by bacteria is strep throat. You may have had strep throat yourself. Bacteria that cause strep throat are shown below ( Figure 1.1). Some types of pneumonia and many cases of illnesses from food are also caused by bacteria. The structures that look like strings of beads are bacteria. They belong to the genus Streptococcus. Bacteria of this genus cause diseases such as strep throat and pneumonia. They are shown here 900 times bigger than their actual size. Fungi are simple eukaryotic organisms that consist of one or more cells. They include mushrooms and yeasts. Human diseases caused by fungi include ringworm and athletes foot. Both are skin diseases that are not usually serious. A ringworm infection is pictured below ( Figure 1.2). A more serious fungus disease is histoplasmosis. It is a lung infection. Though fungal infections can be annoying, they are rarely as serious or deadly as bacterial or viral infections. Ringworm isnt a worm at all. Its a disease caused by a fungus. The fungus causes a ring-shaped rash on the skin, like the one shown here. Protozoa are one-celled organisms with a nucleus, making them eukaryotic organisms. They cause diseases such as malaria. Malaria is a serious disease that is common in warm climates. The protozoa infect people when they are bit by a mosquito. More than a million people die of malaria each year. Other protozoa cause diarrhea. An example is Giardia lamblia ( Figure 1.3). Viruses are nonliving collections of protein and DNA that must reproduce inside of living cells. Viruses cause many common diseases. For example, viruses cause colds and the flu. Cold sores are caused by the virus Herpes simplex This picture shows a one-celled organism called Giardia lamblia. It is a protozoan that causes diarrhea. ( Figure 1.4). Antibiotics do not affect viruses, because antibiotics only kill bacteria. But medicines called antiviral drugs can treat many diseases caused by viruses. Keep in mind that viruses are nonliving, so can they be killed? | text | null |
L_0626 | pathogens | T_3251 | Living things that cause human diseases include bacteria, fungi, and protozoa. Most infectious diseases caused by these organisms can be cured with medicines. For example, medicines called antibiotics can cure most diseases caused by bacteria. Bacteria are one-celled organisms without a nucleus. Although most bacteria are harmless, some cause diseases. Worldwide, the most common disease caused by bacteria is tuberculosis (TB). TB is a serious disease of the lungs. Another common disease caused by bacteria is strep throat. You may have had strep throat yourself. Bacteria that cause strep throat are shown below ( Figure 1.1). Some types of pneumonia and many cases of illnesses from food are also caused by bacteria. The structures that look like strings of beads are bacteria. They belong to the genus Streptococcus. Bacteria of this genus cause diseases such as strep throat and pneumonia. They are shown here 900 times bigger than their actual size. Fungi are simple eukaryotic organisms that consist of one or more cells. They include mushrooms and yeasts. Human diseases caused by fungi include ringworm and athletes foot. Both are skin diseases that are not usually serious. A ringworm infection is pictured below ( Figure 1.2). A more serious fungus disease is histoplasmosis. It is a lung infection. Though fungal infections can be annoying, they are rarely as serious or deadly as bacterial or viral infections. Ringworm isnt a worm at all. Its a disease caused by a fungus. The fungus causes a ring-shaped rash on the skin, like the one shown here. Protozoa are one-celled organisms with a nucleus, making them eukaryotic organisms. They cause diseases such as malaria. Malaria is a serious disease that is common in warm climates. The protozoa infect people when they are bit by a mosquito. More than a million people die of malaria each year. Other protozoa cause diarrhea. An example is Giardia lamblia ( Figure 1.3). Viruses are nonliving collections of protein and DNA that must reproduce inside of living cells. Viruses cause many common diseases. For example, viruses cause colds and the flu. Cold sores are caused by the virus Herpes simplex This picture shows a one-celled organism called Giardia lamblia. It is a protozoan that causes diarrhea. ( Figure 1.4). Antibiotics do not affect viruses, because antibiotics only kill bacteria. But medicines called antiviral drugs can treat many diseases caused by viruses. Keep in mind that viruses are nonliving, so can they be killed? | text | null |
L_0626 | pathogens | T_3251 | Living things that cause human diseases include bacteria, fungi, and protozoa. Most infectious diseases caused by these organisms can be cured with medicines. For example, medicines called antibiotics can cure most diseases caused by bacteria. Bacteria are one-celled organisms without a nucleus. Although most bacteria are harmless, some cause diseases. Worldwide, the most common disease caused by bacteria is tuberculosis (TB). TB is a serious disease of the lungs. Another common disease caused by bacteria is strep throat. You may have had strep throat yourself. Bacteria that cause strep throat are shown below ( Figure 1.1). Some types of pneumonia and many cases of illnesses from food are also caused by bacteria. The structures that look like strings of beads are bacteria. They belong to the genus Streptococcus. Bacteria of this genus cause diseases such as strep throat and pneumonia. They are shown here 900 times bigger than their actual size. Fungi are simple eukaryotic organisms that consist of one or more cells. They include mushrooms and yeasts. Human diseases caused by fungi include ringworm and athletes foot. Both are skin diseases that are not usually serious. A ringworm infection is pictured below ( Figure 1.2). A more serious fungus disease is histoplasmosis. It is a lung infection. Though fungal infections can be annoying, they are rarely as serious or deadly as bacterial or viral infections. Ringworm isnt a worm at all. Its a disease caused by a fungus. The fungus causes a ring-shaped rash on the skin, like the one shown here. Protozoa are one-celled organisms with a nucleus, making them eukaryotic organisms. They cause diseases such as malaria. Malaria is a serious disease that is common in warm climates. The protozoa infect people when they are bit by a mosquito. More than a million people die of malaria each year. Other protozoa cause diarrhea. An example is Giardia lamblia ( Figure 1.3). Viruses are nonliving collections of protein and DNA that must reproduce inside of living cells. Viruses cause many common diseases. For example, viruses cause colds and the flu. Cold sores are caused by the virus Herpes simplex This picture shows a one-celled organism called Giardia lamblia. It is a protozoan that causes diarrhea. ( Figure 1.4). Antibiotics do not affect viruses, because antibiotics only kill bacteria. But medicines called antiviral drugs can treat many diseases caused by viruses. Keep in mind that viruses are nonliving, so can they be killed? | text | null |
L_0626 | pathogens | T_3251 | Living things that cause human diseases include bacteria, fungi, and protozoa. Most infectious diseases caused by these organisms can be cured with medicines. For example, medicines called antibiotics can cure most diseases caused by bacteria. Bacteria are one-celled organisms without a nucleus. Although most bacteria are harmless, some cause diseases. Worldwide, the most common disease caused by bacteria is tuberculosis (TB). TB is a serious disease of the lungs. Another common disease caused by bacteria is strep throat. You may have had strep throat yourself. Bacteria that cause strep throat are shown below ( Figure 1.1). Some types of pneumonia and many cases of illnesses from food are also caused by bacteria. The structures that look like strings of beads are bacteria. They belong to the genus Streptococcus. Bacteria of this genus cause diseases such as strep throat and pneumonia. They are shown here 900 times bigger than their actual size. Fungi are simple eukaryotic organisms that consist of one or more cells. They include mushrooms and yeasts. Human diseases caused by fungi include ringworm and athletes foot. Both are skin diseases that are not usually serious. A ringworm infection is pictured below ( Figure 1.2). A more serious fungus disease is histoplasmosis. It is a lung infection. Though fungal infections can be annoying, they are rarely as serious or deadly as bacterial or viral infections. Ringworm isnt a worm at all. Its a disease caused by a fungus. The fungus causes a ring-shaped rash on the skin, like the one shown here. Protozoa are one-celled organisms with a nucleus, making them eukaryotic organisms. They cause diseases such as malaria. Malaria is a serious disease that is common in warm climates. The protozoa infect people when they are bit by a mosquito. More than a million people die of malaria each year. Other protozoa cause diarrhea. An example is Giardia lamblia ( Figure 1.3). Viruses are nonliving collections of protein and DNA that must reproduce inside of living cells. Viruses cause many common diseases. For example, viruses cause colds and the flu. Cold sores are caused by the virus Herpes simplex This picture shows a one-celled organism called Giardia lamblia. It is a protozoan that causes diarrhea. ( Figure 1.4). Antibiotics do not affect viruses, because antibiotics only kill bacteria. But medicines called antiviral drugs can treat many diseases caused by viruses. Keep in mind that viruses are nonliving, so can they be killed? | text | null |
L_0626 | pathogens | T_3252 | Different pathogens spread in different ways. Some pathogens spread through food. They cause food borne illnesses, which are discussed in a previous concept. Some pathogens spread through water. Giardia lamblia is one example. Water can be boiled to kill Giardia and most other pathogens. Several pathogens spread through sexual contact. HIV is one example, which is discussed in the next concept. Other pathogens that spread through sexual contact are discussed in a separate concept. Many pathogens that cause respiratory diseases spread by droplets in the air. Droplets are released when a person sneezes or coughs. Thousands of tiny droplets are released when a person sneezes ( Figure 1.5). Each droplet can contain thousands of pathogens. Viruses that cause colds and the flu can spread in this way. You may get sick if you breathe in the pathogens. As this picture shows, thousands of tiny droplets are released into the air when a person sneezes. Each droplet may carry thousands of pathogens. You cant normally see the droplets from a sneeze because they are so small. However, you can breathe them in, along with any pathogens they carry. This is how many diseases of the respiratory system are spread. | text | null |
L_0626 | pathogens | T_3253 | Other pathogens spread when they get on objects or surfaces. A fungus may spread in this way. For example, you can pick up the fungus that causes athletes foot by wearing shoes that an infected person has worn. You can also pick up this fungus from the floor of a public shower or other damp areas. After acne, athletes foot is the most common skin disease in the United States. Therefore, the chance of coming in contact with the fungus in one of these ways is fairly high. Bacteria that cause the skin disease impetigo, which causes blisters, can spread when people share towels or clothes. The bacteria can also spread through direct skin contact in sports like wrestling. | text | null |
L_0626 | pathogens | T_3254 | Still other pathogens are spread by vectors. A vector is an organism that carries pathogens from one person or animal to another. Most vectors are insects, such as ticks and mosquitoes. These insects tend to transfer protozoan or viral parasites. When an insect bites an infected person or animal, it picks up the pathogen. Then the pathogen travels to the next person or animal it bites. Ticks carry the bacteria that cause Lyme disease. Mosquitoes ( Figure serious symptoms may develop. Other diseases spread by mosquitoes include Dengue Fever and Yellow Fever. The first case of West Nile virus in North America occurred in 1999. Within just a few years, the virus had spread throughout most of the United States. Birds as well as humans can be infected with the virus. Birds often fly long distances. This is one reason why West Nile virus spread so quickly. | text | null |
L_0627 | pedigree analysis | T_3255 | A pedigree is a chart that shows the inheritance of a trait over several generations. A pedigree is commonly created for families, and it outlines the inheritance patterns of genetic disorders and traits. A pedigree can help predict the probability that offspring will inherit a genetic disorder. Pictured below is a pedigree displaying recessive inheritance of a disorder through three generations ( Figure 1.1). From studying a pedigree, scientists can determine the following: If the trait is sex-linked (on the X or Y chromosome) or autosomal (on a chromosome that does not determine sex). If the trait is inherited in a dominant or recessive fashion. Sometimes pedigrees can also help determine whether individuals with the trait are heterozygous (two different alleles) or homozygous (two of the same allele). Some points to keep in mind when analyzing a pedigree are: 1. With autosomal recessive inheritance, all affected individuals will be homozygous recessive. 2. With dominant inheritance, all affected individuals will have at least one dominant allele. They will be either homozygous dominant or heterozygous. 3. With sex-linked inheritance, more males (XY) than females (XX) usually have the trait. Sex-linked inheritance is usually recessive. | text | null |
L_0628 | peripheral nervous system | T_3256 | There are other nerves in your body that are not found in the brain or spinal cord. The peripheral nervous system (PNS) ( Figure 1.1) contains all the nerves in the body that are found outside of the central nervous system. They include nerves of the hands, arms, feet, legs, and trunk. They also include nerves of the scalp, neck, and face. Nerves that send and receive messages to the internal organs are also part of the peripheral nervous system. The peripheral nervous system is divided into two parts, the sensory division and the motor division. How these divisions of the peripheral nervous system are related to the rest of the nervous system is shown below ( Figure 1.2). Refer to the figure as you read more about the peripheral nervous system in the text that follows. | text | null |
L_0628 | peripheral nervous system | T_3257 | The sensory division carries messages from sense organs and internal organs to the central nervous system. Human beings have several senses. They include sight, hearing, balance, touch, taste, and smell. We have special sense organs for each of these senses. What is the sense organ for sight? For hearing? Sensory neurons in each sense organ receive stimuli, or messages from the environment that cause a response in the body. For example, sensory neurons in the eyes send messages to the brain about light. Sensory neurons in the skin send messages to the brain about touch. Our sense organs recognize sensations, but they dont tell us what we are sensing. For example, when you breathe in chemicals given off by baking cookies, your nose does not tell you that you are smelling cookies. Thats your brains job. The sense organs send messages about sights, smells, and other stimuli to the brain ( Figure 1.3). The brain then reads the messages and tells you what they mean. A certain area of the brain receives and interprets information from each sense organ. For example, information from the nose is received and interpreted by the temporal lobe of the cerebrum. Which senses would be stimulated by these raspberries? | text | null |
L_0628 | peripheral nervous system | T_3257 | The sensory division carries messages from sense organs and internal organs to the central nervous system. Human beings have several senses. They include sight, hearing, balance, touch, taste, and smell. We have special sense organs for each of these senses. What is the sense organ for sight? For hearing? Sensory neurons in each sense organ receive stimuli, or messages from the environment that cause a response in the body. For example, sensory neurons in the eyes send messages to the brain about light. Sensory neurons in the skin send messages to the brain about touch. Our sense organs recognize sensations, but they dont tell us what we are sensing. For example, when you breathe in chemicals given off by baking cookies, your nose does not tell you that you are smelling cookies. Thats your brains job. The sense organs send messages about sights, smells, and other stimuli to the brain ( Figure 1.3). The brain then reads the messages and tells you what they mean. A certain area of the brain receives and interprets information from each sense organ. For example, information from the nose is received and interpreted by the temporal lobe of the cerebrum. Which senses would be stimulated by these raspberries? | text | null |
L_0628 | peripheral nervous system | T_3258 | The motor division of the peripheral system carries messages from the central nervous system to internal organs and muscles. The motor division is also divided into two parts ( Figure 1.2), the somatic nervous system and the autonomic nervous system. The somatic nervous system carries messages that control body movements. It is responsible for activities that are under your control, such as waving your hand or kicking a ball. The girl pictured below ( Figure 1.4) is using her somatic nervous system to control the muscles needed to play the violin. Her brain sends messages to motor neurons that move her hands so she can play. Without the messages from her brain, she would not be able to move her hands and play the violin. The autonomic nervous system carries nerve impulses to internal organs. It controls activities that are not under your control, such as sweating and digesting food. The autonomic nervous system has two parts: 1. The sympathetic division controls internal organs and glands during emergencies. It prepares the body for fight or flight ( Figure 1.5). For example, it increases the heart rate and the flow of blood to the legs, so you can run away from danger. 2. The parasympathetic division controls internal organs and glands during the rest of the time. It controls processes like digestion, heartbeat, and breathing when there is not an emergency. Have you ever become frightened and felt your heart start pounding? How does this happen? The answer is your autonomic nervous system. The sympathetic division prepared you to deal with a possible emergency by increasing | text | null |
L_0628 | peripheral nervous system | T_3258 | The motor division of the peripheral system carries messages from the central nervous system to internal organs and muscles. The motor division is also divided into two parts ( Figure 1.2), the somatic nervous system and the autonomic nervous system. The somatic nervous system carries messages that control body movements. It is responsible for activities that are under your control, such as waving your hand or kicking a ball. The girl pictured below ( Figure 1.4) is using her somatic nervous system to control the muscles needed to play the violin. Her brain sends messages to motor neurons that move her hands so she can play. Without the messages from her brain, she would not be able to move her hands and play the violin. The autonomic nervous system carries nerve impulses to internal organs. It controls activities that are not under your control, such as sweating and digesting food. The autonomic nervous system has two parts: 1. The sympathetic division controls internal organs and glands during emergencies. It prepares the body for fight or flight ( Figure 1.5). For example, it increases the heart rate and the flow of blood to the legs, so you can run away from danger. 2. The parasympathetic division controls internal organs and glands during the rest of the time. It controls processes like digestion, heartbeat, and breathing when there is not an emergency. Have you ever become frightened and felt your heart start pounding? How does this happen? The answer is your autonomic nervous system. The sympathetic division prepared you to deal with a possible emergency by increasing | text | null |
L_0629 | photosynthesis | T_3259 | If a plant gets hungry, it cannot walk to a local restaurant and buy a slice of pizza. So, how does a plant get the food it needs to survive? Plants are producers, which means they are able to make, or produce, their own food. They also produce the "food" for other organisms. Plants are also autotrophs. Autotrophs are the organisms that collect the energy from the sun and turn it into organic compounds. Using the energy from the sun, they produce complex organic compounds from simple inorganic molecules. So once again, how does a plant get the food it needs to survive? Through photosynthesis. Photosynthesis is the process plants use to make their own food from the suns energy, carbon dioxide, and water. During photosynthesis, carbon dioxide and water combine with solar energy to create glucose, a carbohydrate (C6 H12 O6 ), and oxygen. The process can be summarized as: in the presence of sunlight, carbon dioxide + water glucose + oxygen. Glucose, the main product of photosynthesis, is a sugar that acts as the "food" source for plants. The glucose is then converted into usable chemical energy, ATP, during cellular respiration. The oxygen formed during photosynthesis, which is necessary for animal life, is essentially a waste product of the photosynthesis process. Actually, almost all organisms obtain their energy from photosynthetic organisms. For example, if a bird eats a caterpillar, then the bird gets the energy that the caterpillar gets from the plants it eats. So the bird indirectly gets energy that began with the glucose formed through photosynthesis. Therefore, the process of photosynthesis is central to sustaining life on Earth. In eukaryotic organisms, photosynthesis occurs in chloroplasts. Only cells with chloroplastsplant cells and algal (protist) cellscan perform photosynthesis. Animal cells and fungal cells do not have chloroplasts and, therefore, cannot photosynthesize. That is why these organisms, as well as the non- photosynthetic protists, rely on other organisms to obtain their energy. These organisms are heterotrophs. The Photosynthesis Song explaining photosynthesis, can be heard at Click image to the left or use the URL below. URL: | text | null |
L_0629 | photosynthesis | T_3260 | Why do leaves change color each fall? This MIT video demonstrates an experiment about the different pigments in leaves. See the video at . Click image to the left or use the URL below. URL: | text | null |
L_0637 | polygenic traits | T_3277 | Another exception to Mendels rules is polygenic inheritance, which occurs when a trait is controlled by more than one gene. This means that each dominant allele "adds" to the expression of the next dominant allele. Usually, traits are polygenic when there is wide variation in the trait. For example, humans can be many different sizes. Height is a polygenic trait, controlled by at least three genes with six alleles. If you are dominant for all of the alleles for height, then you will be very tall. There is also a wide range of skin color across people. Skin color is also a polygenic trait, as are hair and eye color. Polygenic inheritance often results in a bell shaped curve when you analyze the population ( Figure 1.1). That means that most people fall in the middle of the phenotypic range, such as average height, while very few people are at the extremes, such as very tall or very short. At one end of the curve will be individuals who are recessive for all the alleles (for example, aabbcc); at the other end will be individuals who are dominant for all the alleles (for example, AABBCC). Through the middle of the curve will be individuals who have a combination of dominant and recessive alleles (for example, AaBbCc or AaBBcc). | text | null |
L_0638 | population growth patterns | T_3278 | What does population growth mean? You can probably guess that it means the number of individuals in a population is increasing. The population growth rate tells you how quickly a population is increasing or decreasing. What determines the population growth rate for a particular population? | text | null |
L_0638 | population growth patterns | T_3279 | Population growth rate depends on birth rates and death rates, as well as migration. First, we will consider the effects of birth and death rates. You can predict the growth rate by using this simple equation: growth rate = birth rate death rate. If the birth rate is larger than the death rate, then the population grows. If the death rate is larger than the birth rate, what will happen to the population? The population size will decrease. If the birth and death rates are equal, then the population size will not change. Factors that affect population growth are: 1. 2. 3. 4. 5. 6. Age of organisms at first reproduction. How often an organism reproduces. The number of offspring of an organism. The presence or absence of parental care. How long an organism is able to reproduce. The death rate of offspring. For an ecosystem to be stable, populations in that system must be healthy, and that usually means reproducing as much as their environment allows. Do organisms reproduce yearly or every few years? Do organisms reproduce for much of their life, or just part of their life? Do organisms produce many offspring at once, or just a few, or even just one? Do many newborn organisms die, or do the majority survive? All these factors play a role in the growth of a population. Organisms can use different strategies to increase their reproduction rate. Altricial organisms are helpless at birth, and their parents give them a lot of care. This care is often seen in bird species. ( Figure 1.1). Altricial birds are usually born blind and without feathers. Compared to precocial organisms, altricial organisms have a longer period of development before they reach maturity. Precocial organisms, such as the geese shown below, can take care of themselves at birth and do not require help from their parents ( Figure 1.1). In order to reproduce as much as possible, altricial and precocial organisms must use very different strategies. (left) A hummingbird nest with young il- lustrates an altricial reproductive strategy, with a few small eggs, helpless young, and intensive parental care. (right) The Canada goose shows a precocial repro- ductive strategy. It lays a large number of large eggs, producing well-developed young. | text | null |
L_0638 | population growth patterns | T_3280 | Migration is the movement of individual organisms into, or out of, a population. Migration affects population growth rate. There are two types of migration: 1. Immigration is the movement of individuals into a population from other areas. This increases the population size and growth rate. 2. Emigration is the movement of individuals out of a population. This decreases the population size and growth rate. The earlier growth rate equation can be modified to account for migration: growth rate = (birth rate + immigration rate) (death rate + emigration rate). One type of migration that you are probably familiar with is the migration of birds. Maybe you have heard that birds fly south for the winter. In the fall, birds fly thousands of miles to the south where it is warmer. In the spring, they return to their homes. ( Figure 1.2). Monarch butterflies also migrate from Mexico to the northern U.S. in the summer and back to Mexico in the winter. These types of migrations move entire populations from one location to another. A flock of barnacle geese fly in formation during the autumn migration. | text | null |
L_0638 | population growth patterns | T_3281 | Population growth can be described with two models, based on the size of the population and necessary resources. These two types of growth are known as exponential growth and logistic growth. If a population is given unlimited amounts of resources, such as food and water, land if needed, moisture, oxygen, and other environmental factors, it will grow exponentially. Exponential growth occurs as a population grows larger, dramatically increasing the growth rate. This is shown as a "J-shaped" curve below ( Figure 1.3). You can see that the population grows slowly at first, but as time passes, growth occurs more and more rapidly. Growth of populations according to ex- ponential (or J-curve) growth model (left) and logistic (or S-curve) growth model (right). Time is plotted on the x-axis, and population size is plotted on the y-axis. In nature, organisms do not usually have ideal environments with unlimited food. In nature, there are limits. Sometimes, there will be plenty of food. Sometimes, a fire will wipe out all of the available nutrients. Sometimes a predator will kill many individuals in a population. How do you think these limits affect the way organisms grow? | text | null |
L_0640 | pregnancy and childbirth | T_3283 | While a woman is pregnant, the developing baby may be called an embryo or a fetus. Do these mean the same thing? No, in the very early stages the developing baby is called an embryo, while in the later stages it is called a fetus. When the ball of cells first implants into the uterus, it is called an embryo. The embryo stage lasts until the end of the 8th week after fertilization. After that point until birth, the developing baby is called a fetus. | text | null |
L_0640 | pregnancy and childbirth | T_3284 | During the embryo stage, the baby grows in size. 3rd week after fertilization: Cells of different types start to develop. Cells that will form muscles and skin, for example, start to develop at this time. 4th week after fertilization: Body organs begin to form. 8th week after fertilization: All the major organs have started to develop. Pictured below are some of the changes that take place during the 4th and 8th weeks ( Figure 1.1). Look closely at the two embryos in the figure. Do you think that the older embryo looks more human? Notice that it has arms and legs and lacks a tail. The face has also started to form, and it is much bigger. Embryonic Development (Weeks 48). Most organs develop in the embryo during weeks four through eight. (Note: the drawings of the embryos are not to scale.) | text | null |
L_0640 | pregnancy and childbirth | T_3285 | There are also many changes that take place after the embryo becomes a fetus. Some of the differences between them are obvious. For example, the fetus has ears and eyelids. Its fingers and toes are also fully formed. The fetus even has fingernails and toenails. In addition, the reproductive organs have developed to make the baby a male or female. The brain and lungs are also developing quickly. The fetus has started to move around inside the uterus. This is usually when the mother first feels the fetus moving. By the 28th week, the fetus is starting to look much more like a baby. Eyelashes and eyebrows are present. Hair has started to grow on the head. The body of the fetus is also starting to fill out as muscles and bones develop. Babies born after the 28th week are usually able to survive. However, they need help breathing because their lungs are not yet fully mature. A baby should not be delivered prior to this time, unless absolutely necessary. A baby born prior to week 28 will need considerable medical intervention to survive. During the last several weeks of the fetal period, all of the organs become mature. The most obvious change, however, is an increase in body size. The fetus rapidly puts on body fat and gains weight during the last couple of months. By the end of the 38th week, all of the organs are working, and the fetus is ready to be born. This is when birth normally occurs. A baby born before this time is considered premature. | text | null |
L_0640 | pregnancy and childbirth | T_3286 | During pregnancy, other structures also develop inside the mothers uterus. They are the amniotic sac, placenta, and umbilical cord ( Figure 1.2). Surrounding the fetus is the fluid-filled amniotic sac. The placenta and umbilical cord are also shown here. They provide a connection between the mothers and fetuss blood for the transfer of nutrients and gases. The amniotic sac is a membrane that surrounds the fetus. It is filled with water and dissolved substances, known as amniotic fluid. Imagine placing a small plastic toy inside a balloon and then filling the balloon with water. The toy would be cushioned and protected by the water. It would also be able to move freely inside the balloon. The amniotic sac and its fluid are like a water-filled balloon. They cushion and protect the fetus. They also let the fetus move freely inside the uterus. The placenta is a spongy mass of blood vessels. Some of the vessels come from the mother. Some come from the fetus. The placenta is attached to the inside of the mothers uterus. The fetus is connected to the placenta by a tube called the umbilical cord. The cord contains two arteries and a vein. Substances pass back and forth between the mothers and fetuss blood through the placenta and cord. Oxygen and nutrients pass from the mother to the fetus. Carbon dioxide passes from the fetus to the mother. It is important for the mother to eat plenty of nutritious foods during pregnancy. She must take in enough nutrients for the fetus as well as for herself. She needs extra calories, proteins, and lipids. She also needs more vitamins and minerals. In addition to eating well, the mother must avoid substances that could harm the embryo or fetus. These include alcohol, illegal drugs, and some medicines. It is especially important for her to avoid these substances during the first eight weeks after fertilization. This is when all the major organs are forming. Exposure to harmful substances during this time could damage the developing body systems. | text | null |
L_0640 | pregnancy and childbirth | T_3287 | During childbirth, a baby passes from the uterus, through the vagina, and out of the mothers body. Childbirth usually starts when the amniotic sac breaks. Then, the muscles of the uterus start contracting. The contractions get stronger and closer together. They may go on for hours. Eventually, the contractions squeeze the baby out of the uterus. Once the baby enters the vagina, the mother starts pushing. She soon pushes the baby through the vagina and out of her body. As soon as the baby is born, the umbilical cord is cut. After the cord is cut, the baby can no longer get rid of carbon dioxide through the cord and placenta. As a result, carbon dioxide builds up in the babys blood. This triggers the baby to start breathing. The amniotic sac and placenta pass through the vagina and out of the body shortly after the birth of the baby. | text | null |
L_0641 | preserving water sources | T_3288 | It might seem like there is plenty of water on Earth, but thats not really the case. Water is a limited resource. That means that it is used faster than it is replaced. Theoretically, at some point in time, the supply of fresh water could run out. Though this is unlikely, it is possible. But it is a significant issue in parts of the world with large populations. As these populations continue to grow, the supply of water becomes an increasingly important issue. Even though we have lots of water in our oceans, we cannot use that water whenever we want. It takes special equipment, such as a desalination plant, and a lot of energy (and money) to convert salt water into fresh water. Of all the water on Earth, only about 1% can be used for drinking water. Almost all of the rest of the water is either salt water in the ocean or ice in glaciers and ice caps. As a result, there are water shortages many places in the world. Since we have such a limited supply of water, it is important to preserve our water supplies. Therefore, steps have been taken to prevent water pollution. Technologies have also been developed to conserve water and prevent water pollution. Sub-Saharan African countries have the most vulnerable water supplies. Some scientists believe of a potential future crisis in both Asia and Africa from pollution and depletion of natural water resources. Many countries in the Middle East are at an extreme risk of water shortages. Diminished water supplies could increase the risk of both internal conflicts or wars between countries. | text | null |
L_0641 | preserving water sources | T_3289 | In the U.S., concern over water pollution has resulted in many federal laws. Some of these laws go all the way back to the 1800s! The laws prohibit the disposal of any waste into the nations rivers, lakes, streams, and other bodies of water, unless a person first has a permit. Growing concern for controlling water pollutants led to the enactment of the Clean Water Act in 1972. The Clean Water Act set water quality standards. It also limits the pollution that can enter the waterways. Other countries are also actively preventing water pollution and purifying water ( Figure 1.1). A water purification station in France. Contaminants are removed to make clean water. | text | null |
L_0641 | preserving water sources | T_3290 | Fresh water is also preserved by purifying wastewater. Wastewater is water that has been used for cleaning, washing, flushing, or manufacturing. It includes the water that goes down your shower drain and that is flushed down your toilet. Instead of dumping wastewater directly into rivers, wastewater can be purified at a water treatment plant ( Figure 1.2). When wastewater is recycled, waterborne diseases caused by pathogens in sewage can be prevented. What are some ways you can save water in your own house? | text | null |
L_0642 | preventing infectious diseases | T_3291 | Infectious diseases are diseases that spread from person to person. They are caused by pathogens such as bacteria, viruses or fungi. What can you do to avoid infectious diseases? Eating right and getting plenty of sleep are a good start. These habits will help keep your immune system healthy. With a healthy immune system, you will be able to fight off many pathogens. The next best way is to avoid pathogens. Though this is difficult, there are steps you can take to limit your exposure to pathogens. Here are the ten best ways to prevent the spread of infectious diseases. 1. Wash your hands frequently. 2. Dont share personal items. 3. Cover your mouth when you cough or sneeze. 4. 5. 6. 7. 8. 9. 10. Get vaccinated. Use safe cooking practices. Be a smart traveler. Practice safe sex. Dont pick your nose (or your mouth or eyes either). Exercise caution with animals. Watch the news, and be aware of disease outbreaks. | text | null |
L_0642 | preventing infectious diseases | T_3292 | You can also take steps to avoid pathogens in the first place. The best way to avoid pathogens is to wash your hands often. You should wash your hands after using the bathroom or handling raw meat or fish. You should also wash your hands before eating or preparing food. In addition, you should also wash the food that your eat, and the utensils and countertop where food is prepared. In addition, you should wash your hands after being around sick people. The correct way to wash your hands is demonstrated below ( Figure 1.1). If soap and water arent available, use some hand sanitizer. The best way to prevent diseases spread by vectors is to avoid contact with the vectors. Recall that a vector is an organism that carries pathogens from one person or animal to another. For example, ticks and mosquitoes are vectors, so you should wear long sleeves and long pants when appropriate to avoid tick and mosquito bites. Using insect repellent can also reduce your risk of insect bites. Many infectious diseases can be prevented with vaccinations. Immunization can drastically reduce your chances of contracting many diseases. You will read more about vaccinations in another concept. Vaccinations can help prevent measles, mumps, chicken pox, and several other diseases. If you do develop an infectious disease, try to avoid infecting others. Stay home from school until you are well. Also, take steps to keep your germs to yourself. Cover your mouth and nose with a tissue when you sneeze or cough, Watching the news will allow you to make informed decisions. If an outbreak of bad beef due to a bacterial infection is in the news, dont buy beef for a while. If tomatoes are making people sick, dont eat tomatoes until the outbreak is over. If a place has an unhealthy water supply, boil the water or drink bottled water. Local news can tell you of restaurants to avoid due to unhealthy conditions. And so on. | text | null |
L_0643 | preventing noninfectious diseases | T_3293 | Noninfectious diseases cant be passed from one person to another. Instead, these types of diseases are caused by factors such as the environment, genetics, and lifestyle. Examples of inherited noninfectious conditions include cystic fibrosis and Down syndrome. If youre born with these conditions, you must learn how to manage the symptoms. Examples of conditions caused by environmental or lifestyle factors include heart disease and skin cancer. We cant change our genetic codes, but there are plenty of ways to prevent other noninfectious diseases. For example, cutting down on exposure to cigarette smoke and the suns rays will prevent certain types of cancer. It is a fact that most chronic noninfectious diseases can be prevented. The chronic noninfectious diseases that cause the most deaths in many developed countries are largely preventable. These diseases are heart disease, stroke, diabetes and cancer, and though they do have some genetic components, they also have many lifestyle components. For example, some cancers have genetic risks, but people at high risk for cancers can have screening examinations to catch them early or sometimes can take other steps to prevent the cancers. Heart disease, stroke and diabetes are mostly linked to lifestyle choices, even when family history puts a person at higher risk for the diseases. Most allergies can be prevented by avoiding the substances that cause them. For example, you can avoid pollens by staying indoors as much as possible. You can learn to recognize plants like poison ivy and not touch them. A good way to remember how to avoid poison ivy is "leaves of three, let it be." Some people receive allergy shots to help prevent allergic reactions. The shots contain tiny amounts of allergens, which are the substances that cause an allergic reaction. After many months or years of shots, the immune system gets used to the allergens and no longer responds to them. Type 1 diabetes and other autoimmune diseases cannot be prevented. But choosing a healthy lifestyle can help prevent type 2 diabetes. Getting plenty of exercise, avoiding high-fat foods, and staying at a healthy weight can reduce the risk of developing this type of diabetes. This is especially important for people who have family members with the disease. Making these healthy lifestyle choices can also help prevent some types of cancer. In addition, you can lower the risk of cancer by avoiding carcinogens, which are substances that cause cancer. For example, you can reduce your risk of lung cancer by not smoking. You can reduce your risk of skin cancer by using sunscreen. How to choose a sunscreen that offers the most protection is explained below ( Figure 1.1). Some people think that tanning beds are a safe way to get a tan. This is a myth. Tanning beds expose the skin to UV radiation. Any exposure to UV radiation increases the risk of skin cancer. It doesnt matter whether the radiation comes from tanning lamps or the sun. Overall, people in many developed countries are contributing to higher rates of noninfectious diseases (heart disease, stroke, diabetes and cancer) by taking advantage of technology and social environments that encourage a less active lifestyle, and also encourages faster and cheaper meals. For example, many children now spend more time on their computer or watching TV then playing outdoors. The "faster and cheaper" meals are usually less healthy than other meals. Even though many people are living longer, they can choose to live more healthily by adopting regular exercise routines and healthy eating habits. When you choose a sunscreen, select one with an SPF (sun protection factor) of 30 or higher. Also, choose a sunscreen that protects against both UVB and UVA radiation. | text | null |
L_0645 | process of cellular respiration | T_3298 | Cellular respiration is the process of extracting energy in the form of ATP from the glucose in the food you eat. How does cellular respiration happen inside of the cell? Cellular respiration is a three step process. Briefly: 1. In stage one, glucose is broken down in the cytoplasm of the cell in a process called glycolysis. 2. In stage two, the pyruvate molecules are transported into the mitochondria. The mitochondria are the organelles known as the energy "powerhouses" of the cells (Figure 1.1). In the mitochondria, the pyruvate, which have been converted into a 2-carbon molecule, enter the Krebs cycle. Notice that mitochondria have an inner membrane with many folds, called cristae. These cristae greatly increase the membrane surface area where many of the cellular respiration reactions take place. 3. In stage three, the energy in the energy carriers enters an electron transport chain. During this step, this energy is used to produce ATP. Oxygen is needed to help the process of turning glucose into ATP. The initial step releases just two molecules of ATP for each glucose. The later steps release much more ATP. Most of the reactions of cellular respira- tion are carried out in the mitochondria. | text | null |
L_0645 | process of cellular respiration | T_3299 | What goes into the cell? Oxygen and glucose are both reactants of cellular respiration. Oxygen enters the body when an organism breathes. Glucose enters the body when an organism eats. | text | null |
L_0645 | process of cellular respiration | T_3300 | What does the cell produce? The products of cellular respiration are carbon dioxide and water. Carbon dioxide is transported from your mitochondria out of your cell, to your red blood cells, and back to your lungs to be exhaled. ATP is generated in the process. When one molecule of glucose is broken down, it can be converted to a net total of 36 or 38 molecules of ATP. This only occurs in the presence of oxygen. | text | null |
L_0645 | process of cellular respiration | T_3301 | The overall chemical reaction for cellular respiration is one molecule of glucose (C6 H12 O6 ) and six molecules of oxygen (O2 ) yields six molecules of carbon dioxide (CO2 ) and six molecules of water (H2 O). Using chemical symbols the equation is represented as follows: C6 H12 O6 + 6O2 6CO2 + 6H2 O ATP is generated during the process. Though this equation may not seem that complicated, cellular respiration is a series of chemical reactions divided into three stages: glycolysis, the Krebs cycle, and the electron transport chain. | text | null |
L_0645 | process of cellular respiration | T_3302 | Stage one of cellular respiration is glycolysis. Glycolysis is the splitting, or lysis of glucose. Glycolysis converts the 6-carbon glucose into two 3-carbon pyruvate molecules. This process occurs in the cytoplasm of the cell, and it occurs in the presence or absence of oxygen. During glycolysis a small amount of NADH is made as are four ATP. Two ATP are used during this process, leaving a net gain of two ATP from glycolysis. The NADH temporarily holds energy, which will be used in stage three. | text | null |
L_0645 | process of cellular respiration | T_3303 | In the presence of oxygen, under aerobic conditions, pyruvate enters the mitochondria to proceed into the Krebs cycle. The second stage of cellular respiration is the transfer of the energy in pyruvate, which is the energy initially in glucose, into two energy carriers, NADH and FADH2 . A small amount of ATP is also made during this process. This process occurs in a continuous cycle, named after its discover, Hans Krebs. The Krebs cycle uses a 2-carbon molecule (acetyl-CoA) derived from pyruvate and produces carbon dioxide. | text | null |
L_0645 | process of cellular respiration | T_3304 | Stage three of cellular respiration is the use of NADH and FADH2 to generate ATP. This occurs in two parts. First, the NADH and FADH2 enter an electron transport chain, where their energy is used to pump, by active transport, protons (H+ ) into the intermembrane space of mitochondria. This establishes a proton gradient across the inner membrane. These protons then flow down their concentration gradient, moving back into the matrix by facilitated diffusion. During this process, ATP is made by adding inorganic phosphate to ADP. Most of the ATP produced during cellular respiration is made during this stage. For each glucose that starts cellular respiration, in the presence of oxygen (aerobic conditions), 36-38 ATP are generated. Without oxygen, under anaerobic conditions, much less (only two!) ATP are produced. | text | null |
L_0646 | processes of breathing | T_3305 | Breathing is only part of the process of bringing oxygen to where it is needed in the body. After oxygen enters the lungs, what happens? 1. The oxygen enters the bloodstream from the alveoli, tiny sacs in the lungs where gas exchange takes place ( Figure 1.1). The transfer of oxygen into the blood is through simple diffusion. 2. The oxygen-rich blood returns to the heart. 3. Oxygen-rich blood is then pumped through the aorta, the large artery that receives blood directly from the heart. 4. From the aorta, oxygen-rich blood travels to the smaller arteries and, finally, to the capillaries, the smallest type of blood vessel. 5. The oxygen molecules move, by diffusion, out of the capillaries and into the body cells. 6. While oxygen moves from the capillaries and into body cells, carbon dioxide moves from the cells into the capillaries. Gas exchange is the movement of oxygen into the blood and carbon dioxide out of the blood. 7. Carbon dioxide is brought, through the blood, back to the heart and then to the lungs. Then it is released into the air during exhalation. Why is oxygen needed by each cell in your body? To make ATP, the usable form of cellular energy. Oxygen is needed in the final stage of cellular respiration, which is the process of converting glucose into ATP. This process is much more efficient in the presence of oxygen. Without oxygen, much less ATP is produced. As ATP is needed for the cells to function properly, every cell in your body needs oxygen. Getting that oxygen begins with inhaling. The oxygen moves into your blood, where it travels to every cell in your body. | text | null |
L_0647 | producers | T_3306 | Energy is the ability to do work. In organisms, this work can be physical work, like walking or jumping, or it can be the work used to carry out the chemical processes in their cells. Every biochemical reaction that occurs in an organisms cells needs energy. All organisms need a constant supply of energy to stay alive. Some organisms can get the energy directly from the sun. Other organisms get their energy from other organisms. Through predator-prey relationships, the energy of one organism is passed on to another. Energy is constantly flowing through a community. With just a few exceptions, all life on Earth depends on the suns energy for survival. The energy of the sun is first captured by producers ( Figure 1.1), organisms that can make their own food. Many producers make their own food through the process of photosynthesis. The "food" the producers make is the sugar, glucose. Producers make food for the rest of the ecosystem. As energy is not recycled, energy must consistently be captured by producers. This energy is then passed on to the organisms that eat the producers, and then to the organisms that eat those organisms, and so on. Recall that the only required ingredients needed for photosynthesis are sunlight, carbon dioxide (CO2 ), and wa- ter (H2 O). From these simple inorganic ingredients, photosynthetic organisms produce the carbohydrate glucose (C6 H12 O6 ), and other complex organic compounds. Essentially, these producers are changing the energy from the sunlight into a usable form of energy. They are also making the oxygen that we breathe. Oxygen is a waste product of photosynthesis. The survival of every ecosystem is dependent on the producers. Without producers capturing the energy from the sun and turning it into glucose, an ecosystem could not exist. On land, plants are the dominant producers. Phytoplankton, tiny photosynthetic organisms, are the most common producers in the oceans and lakes. Algae, which is the green layer you might see floating on a pond, are an example of phytoplankton. There are also bacteria that use chemical processes to produce food. They get their energy from sources other than the sun, but they are still called producers. This process is known as chemosynthesis, and is common in ecosystems without sunlight, such as certain marine ecosystems. Producers include (a) plants, (b) algae, and (c) diatoms. | text | null |
L_0652 | puberty and adolescence | T_3317 | Puberty is the stage of life when a child becomes sexually mature. Puberty lasts from about 12 to 18 years of age in boys and from about 10 to 16 years of age in girls. The age when puberty begins is different from one child to another. Children that begin puberty much earlier or later than their peers may feel self-conscious. They may also worry that something is wrong with them. Usually, an early or late puberty is perfectly normal. In boys, puberty begins when the pituitary gland tells the testes to secrete testosterone. Testosterone causes the following to happen: 1. 2. 3. 4. The penis and testes grow. The testes start making sperm. Pubic and facial hair grow. The shoulders broaden, and the voice becomes deeper. In girls, puberty begins when the pituitary gland tells the ovaries to secrete estrogen. Estrogen causes the following to happen: 1. 2. 3. 4. 5. The uterus and ovaries grow. The ovaries start releasing eggs. The menstrual cycle begins. Pubic hair grows. The hips widen, and the breasts develop. Boys and girls are close to the same height during childhood. In both boys and girls, growth in height and weight is very fast during puberty. But boys grow faster than girls during puberty. Their period of fast growth also lasts longer. By the end of puberty, boys are an average of 10 centimeters (4 inches) taller than girls. | text | null |
L_0652 | puberty and adolescence | T_3318 | Adolescence is the period of life between the start of puberty and the beginning of adulthood. Adolescence includes the physical changes of puberty. It also includes many other changes, including significant mental, emotional, and social changes. During adolescence: Teenagers develop new thinking abilities. For example, they can think about abstract ideas, such as freedom. They are also better at thinking logically. They are usually better at solving problems as well. Teenagers try to establish a sense of who they are as individuals. They may try to become more independent from their parents. Most teens also have emotional ups and downs. This is partly due to changing hormone levels. Teenagers usually spend much more time with peers than with family members. | text | null |
L_0654 | recombinant dna | T_3320 | Recombinant DNA is the combination of DNA from two different sources. For example, it is possible to place a human gene into bacterial DNA. Recombinant DNA technology is useful in gene cloning and in identifying the function of a gene. Recombinant DNA technology can also be used to produce useful proteins, such as insulin. To treat diabetes, many people need insulin. Previously, insulin had been taken from animals. Through recombinant DNA technology, bacteria were created that carry the human gene which codes for the production of insulin. These bacteria become tiny factories that produce this protein. Recombinant DNA technology helps create insulin so it can be used by humans. Recombinant DNA technology is used in gene cloning. A clone is an exact genetic copy. Genes are cloned for many reasons, including use in medicine and in agriculture. Below are the steps used to copy, or clone, a gene: 1. A gene or piece of DNA is put in a vector, or carrier molecule, producing a recombinant DNA molecule. 2. The vector is placed into a host cell, such as a bacterium. 3. The gene is copied (or cloned) inside of the bacterium. As the bacterial DNA is copied, so is the vector DNA. As the bacteria divide, the recombinant DNA molecules are divided between the new cells. Over a 12- to 24-hour period, millions of copies of the cloned DNA are made. 4. The cloned DNA can produce a protein (like insulin) that can be used in medicine or in research. | text | null |
L_0654 | recombinant dna | T_3321 | Bacteria have small rings of DNA in the cytoplasm, called plasmids ( Figure 1.1). A plasmid is not part of the bacterial chromosome, but an additional pieced of DNA. When putting foreign DNA into a bacterium, the plasmids are often used as a vector. Viruses can also be used as vectors. The manipulation of the plasmid DNA, and then the insertion of the recombinant plasmid into a bacterium, is an invaluable tool in scientific research. This image shows a drawing of a plasmid. The plasmid has two large segments and one small segment depicted. The two large segments (green and blue) indicate antibiotic resistances usually used in a screening procedure. The antibiotic resis- tance segments ensure only bacteria with the plasmid will grow. The small segment (red) indicates an origin of replication. The origin of replication is where DNA replication starts, copying the plasmid. | text | null |
L_0655 | reduce reuse and recycle | T_3322 | Why conserve resources? During your lifetime, it is possible that the world may run out of some nonrenewable resources, especially as the population passes 8 then 9 billion people. So it is necessary to try to make these resources last as long as possible. You may have heard people say, "Reduce, Reuse, Recycle." You may know that this is the slogan of the campaign to conserve resources. But what do each one of those words truly mean? | text | null |
L_0655 | reduce reuse and recycle | T_3323 | What exactly does it mean to reduce? Reducing means decreasing the amount of waste we create. That could also mean cutting down on use of natural resources. In addition, many ways to reduce also result in saving money. Minimizing of waste may be difficult to achieve for individuals and households, but here are some starting points that you can include in your daily routine to reduce the use of resources: Turn lights off when not using them. Turn the television off when no one is watching. Replace burned out bulbs with ones that are more energy-efficient ( Figure 1.1). Reduce water use by turning off faucets when not using water. Use low-flow shower heads, which save on water and use less energy. Use low-flush and composting toilets. Put kitchen and garden waste into a compost pile. In the summer, change filters on your air conditioner and use as little air conditioning as possible. The use of air conditioning uses a lot of energy. In winter, make sure your furnace is working properly and make sure there is enough insulation on windows and doors. Mend broken or worn items instead of buying new ones. When you go shopping for items, buy quantities you know you will use without waste. Walk or bicycle instead of using an automobile, in order to save on fuel usage and costs, and to cut down on pollution. When buying a new vehicle, check into hybrid, semi-hybrid, or electric models to cut down on gas usage and air pollution. These fluorescent light bulbs are much more energy efficient than standard light bulbs. | text | null |
L_0655 | reduce reuse and recycle | T_3324 | Lets now look at what we can reuse. Reusing includes using the same item again for the same function and also using an item again for a new function. Reuse can have both economic and environmental benefits. New packaging regulations are helping society to move towards these goals. Water is a resource that can be reused for numerous purposes. You may not drink used water, but it is quite useful for other purposes. Some ways of reusing resources include: Use reusable bags when shopping. Use gray water. Water that has been used for laundry, for example, can be used to water the garden or flush toilets. At the town level, purified sewage water can be used for fountains, watering public parks or golf courses, fire fighting, and irrigating crops. Rain can be caught in rain barrels and used to water your garden. What are some other ways to reuse resources? | text | null |
L_0655 | reduce reuse and recycle | T_3325 | Now we move on to recycle. Sometimes it may be difficult to understand the differences between reusing and recycling. Recycling involves processing used materials in order to make them suitable for other uses. That usually means taking a used item, breaking it down, and reusing the pieces. Even though recycling requires extra energy, it does often make use of items which are broken, worn out, or cannot be reused. The things that are commonly recycled include: Batteries. Biodegradable waste. Electronics. Iron and steel. Aluminum ( Figure 1.2). Glass. Paper. Plastic. Textiles, such as clothing. Timber. Tires. Each type of recyclable requires a different recycling technique. Here are some things you can do to recycle in your home, school, or community: Laws can also be created to make sure people and companies reduce, reuse, and recycle. Individuals can vote for leaders who stand for sustainable ecological practices. They can also tell their leaders to make wise use of natural resources. You can also influence companies. If you and your family only buy from companies and restaurants that support recycling or eco-friendly packaging, then other companies will also change to be more environmentally friendly. | text | null |
L_0656 | renewable resources and alternative energy sources | T_3326 | A resource is renewable if it is remade by natural processes at the same rate that humans use it up. Sunlight and wind are renewable resources because they will not be used up ( Figure 1.1). The rising and falling of ocean tides is another example of a resource in unlimited supply. A sustainable resource is a resource that is used in a way that meets the needs of the present without keeping future generations from meeting their needs. People can sustainably harvest wood, cork, and bamboo. Farmers can also grow crops sustainably by not planting the same crop in their soil year after year. Planting the same crop each year can remove nutrients from the soil. This means that wood, cork, bamboo, and crops can be sustainable resources. | text | null |
L_0656 | renewable resources and alternative energy sources | T_3327 | A nonrenewable resource is one that cannot be replaced as easily as it is consumed. Fossil fuels are an example of nonrenewable resources. They take millions of years to form naturally, and so they cannot be replaced as fast as they are consumed. To take the place of fossil fuel use, alternative energy resources are being developed. These alternative energy sources often utilize renewable resources. The following are examples of sustainable alternative energy resources: Solar power, which uses solar cells to turn sunlight into electricity ( Figure 1.2). The electricity can be used to power anything that uses normal coal-generated electricity. Wind power, which uses windmills to transform wind energy into electricity. It is used for less than 1% of the worlds energy needs. But wind energy is growing fast. Every year, 30% more wind energy is used to create electricity. Hydropower ( Figure 1.3), which uses the energy of moving water to turn turbines (similar to windmills) or water wheels, that create electricity. This form of energy produces no waste or pollution. It is a renewable resource. Geothermal power, which uses the natural flow of heat from the Earths core to produce steam. This steam is used to turn turbines which create electricity. Biomass is the mass of biological organisms. It is usually used to describe the amount of organic matter in a trophic level of an ecosystem. Biomass production involves using organic matter ("biomass") from plants to create electricity. Using corn to make ethanol fuel is an example of biomass generated energy. Biomass is generally renewable. Tides in the ocean can also turn a turbine to create electricity. This energy can then be stored until needed ( Figure 1.4). Dam of the tidal power plant in the Rance River, Bretagne, France | text | null |
L_0656 | renewable resources and alternative energy sources | T_3327 | A nonrenewable resource is one that cannot be replaced as easily as it is consumed. Fossil fuels are an example of nonrenewable resources. They take millions of years to form naturally, and so they cannot be replaced as fast as they are consumed. To take the place of fossil fuel use, alternative energy resources are being developed. These alternative energy sources often utilize renewable resources. The following are examples of sustainable alternative energy resources: Solar power, which uses solar cells to turn sunlight into electricity ( Figure 1.2). The electricity can be used to power anything that uses normal coal-generated electricity. Wind power, which uses windmills to transform wind energy into electricity. It is used for less than 1% of the worlds energy needs. But wind energy is growing fast. Every year, 30% more wind energy is used to create electricity. Hydropower ( Figure 1.3), which uses the energy of moving water to turn turbines (similar to windmills) or water wheels, that create electricity. This form of energy produces no waste or pollution. It is a renewable resource. Geothermal power, which uses the natural flow of heat from the Earths core to produce steam. This steam is used to turn turbines which create electricity. Biomass is the mass of biological organisms. It is usually used to describe the amount of organic matter in a trophic level of an ecosystem. Biomass production involves using organic matter ("biomass") from plants to create electricity. Using corn to make ethanol fuel is an example of biomass generated energy. Biomass is generally renewable. Tides in the ocean can also turn a turbine to create electricity. This energy can then be stored until needed ( Figure 1.4). Dam of the tidal power plant in the Rance River, Bretagne, France | text | null |
L_0656 | renewable resources and alternative energy sources | T_3327 | A nonrenewable resource is one that cannot be replaced as easily as it is consumed. Fossil fuels are an example of nonrenewable resources. They take millions of years to form naturally, and so they cannot be replaced as fast as they are consumed. To take the place of fossil fuel use, alternative energy resources are being developed. These alternative energy sources often utilize renewable resources. The following are examples of sustainable alternative energy resources: Solar power, which uses solar cells to turn sunlight into electricity ( Figure 1.2). The electricity can be used to power anything that uses normal coal-generated electricity. Wind power, which uses windmills to transform wind energy into electricity. It is used for less than 1% of the worlds energy needs. But wind energy is growing fast. Every year, 30% more wind energy is used to create electricity. Hydropower ( Figure 1.3), which uses the energy of moving water to turn turbines (similar to windmills) or water wheels, that create electricity. This form of energy produces no waste or pollution. It is a renewable resource. Geothermal power, which uses the natural flow of heat from the Earths core to produce steam. This steam is used to turn turbines which create electricity. Biomass is the mass of biological organisms. It is usually used to describe the amount of organic matter in a trophic level of an ecosystem. Biomass production involves using organic matter ("biomass") from plants to create electricity. Using corn to make ethanol fuel is an example of biomass generated energy. Biomass is generally renewable. Tides in the ocean can also turn a turbine to create electricity. This energy can then be stored until needed ( Figure 1.4). Dam of the tidal power plant in the Rance River, Bretagne, France | text | null |
L_0656 | renewable resources and alternative energy sources | T_3327 | A nonrenewable resource is one that cannot be replaced as easily as it is consumed. Fossil fuels are an example of nonrenewable resources. They take millions of years to form naturally, and so they cannot be replaced as fast as they are consumed. To take the place of fossil fuel use, alternative energy resources are being developed. These alternative energy sources often utilize renewable resources. The following are examples of sustainable alternative energy resources: Solar power, which uses solar cells to turn sunlight into electricity ( Figure 1.2). The electricity can be used to power anything that uses normal coal-generated electricity. Wind power, which uses windmills to transform wind energy into electricity. It is used for less than 1% of the worlds energy needs. But wind energy is growing fast. Every year, 30% more wind energy is used to create electricity. Hydropower ( Figure 1.3), which uses the energy of moving water to turn turbines (similar to windmills) or water wheels, that create electricity. This form of energy produces no waste or pollution. It is a renewable resource. Geothermal power, which uses the natural flow of heat from the Earths core to produce steam. This steam is used to turn turbines which create electricity. Biomass is the mass of biological organisms. It is usually used to describe the amount of organic matter in a trophic level of an ecosystem. Biomass production involves using organic matter ("biomass") from plants to create electricity. Using corn to make ethanol fuel is an example of biomass generated energy. Biomass is generally renewable. Tides in the ocean can also turn a turbine to create electricity. This energy can then be stored until needed ( Figure 1.4). Dam of the tidal power plant in the Rance River, Bretagne, France | text | null |
L_0656 | renewable resources and alternative energy sources | T_3328 | Scientists at the Massachusetts of Technology are turning trash into coal, which can readily be used to heat homes and cook food in developing countries. This coal burns cleaner than that from fossil fuels. It also save a tremendous amount of energy. See http://youtu.be/GzhFgEYiVyY?list=PLzMhsCgGKd1hoofiKuifwy6qRXZs7NG6a for more information. Click image to the left or use the URL below. URL: | text | null |
L_0659 | reproductive system health | T_3336 | As was discussed in previous concepts, both infectious and noninfectious diseases of the reproductive system can be very serious. But there are ways to keep your reproductive system healthy. What can you do to keep your reproductive system healthy? You can start by making the right choices for overall good health. To be as healthy as you can be, you should: Eat a balanced diet that is high in fiber and low in fat. Drink plenty of water. Get regular exercise. Maintain a healthy weight. Get enough sleep. Avoid using tobacco, alcohol, or other drugs. Manage stress in healthy ways. Keeping your genitals clean is also very important. A daily shower or bath is all that it takes. Females do not need to use special feminine hygiene products. In fact, using them may do more harm than good because they can irritate the vagina or other reproductive structures. You should also avoid other behaviors that can put you at risk. Do not get into contact with another persons blood or other body fluids. For example, never get a tattoo or piercing unless you are sure that the needles have not been used before. This is one of the most important ways to prevent an STI. Of course, the only way to be fully protected against STIs is to refrain from sexual activity. If you are a boy, you should always wear a protective cup when you play contact sports. Contact sports include football, boxing, and hockey. Wearing a cup will help protect the testes from injury. You should also do a monthly self-exam to check for cancer of the testes. If you are a girl and use tampons, be sure to change them every four to six hours. Leaving tampons in for too long can put you at risk of toxic shock syndrome. This is a serious condition. Signs and symptoms of toxic shock syndrome develop suddenly, and the disease can be fatal. The disease involves fever, shock, and problems with the function of several body organs. Girls should also get in the habit of doing a monthly self-exam to check for breast cancer. Although breast cancer is rare in teens, its a good idea to start doing the exam when you are young. It will help you get to know what is normal for you. | text | null |
L_0661 | respiration | T_3340 | Most of the time, you breathe without thinking about it. Breathing is mostly an involuntary action that is controlled by a part of your brain that also controls your heart beat. If you swim, do yoga, or sing, you know you can control your breathing, however. Taking air into the body through the nose and mouth is called inhalation. Pushing air out of the body through the nose or mouth is called exhalation. The woman pictured below is exhaling before she surfaces from the pool water (Figure 1.1). How do lungs allow air in? Air moves into and out of the lungs by the movement of muscles. The most important muscle in the process of breathing is the diaphragm, a sheet of muscle that spreads across the bottom of the rib cage. The diaphragm and rib muscles contract and relax to move air into and out of the lungs. During inhalation, the diaphragm contracts and moves downward. The rib muscles contract and cause the ribs to move outward. This causes the chest volume to increase. Because the chest volume is larger, the air pressure inside the lungs is lower than the air pressure outside. This difference in air pressures causes air to be sucked into the lungs. When the diaphragm and rib muscles relax, air is pushed out of the lungs. Exhalation is similar to letting the air out of a balloon. How does the inhaled oxygen get into the bloodstream? The exchange of gasses between the lungs and the blood happens in tiny sacs called alveoli. The walls of the alveoli are very thin and allow gases to pass though them. The alveoli are lined with capillaries (Figure 1.2). Oxygen moves from the alveoli to the blood in the capillaries that surround the alveoli. At the same time, carbon dioxide moves in the opposite direction, from capillary blood to the alveoli. The gases move by simple diffusion, passing from an area of high concentration to an area of low concentration. For example, initially there is more oxygen in the alveoli than in the blood, so oxygen moves by diffusion from the alveoli into the blood. | text | null |
L_0661 | respiration | T_3340 | Most of the time, you breathe without thinking about it. Breathing is mostly an involuntary action that is controlled by a part of your brain that also controls your heart beat. If you swim, do yoga, or sing, you know you can control your breathing, however. Taking air into the body through the nose and mouth is called inhalation. Pushing air out of the body through the nose or mouth is called exhalation. The woman pictured below is exhaling before she surfaces from the pool water (Figure 1.1). How do lungs allow air in? Air moves into and out of the lungs by the movement of muscles. The most important muscle in the process of breathing is the diaphragm, a sheet of muscle that spreads across the bottom of the rib cage. The diaphragm and rib muscles contract and relax to move air into and out of the lungs. During inhalation, the diaphragm contracts and moves downward. The rib muscles contract and cause the ribs to move outward. This causes the chest volume to increase. Because the chest volume is larger, the air pressure inside the lungs is lower than the air pressure outside. This difference in air pressures causes air to be sucked into the lungs. When the diaphragm and rib muscles relax, air is pushed out of the lungs. Exhalation is similar to letting the air out of a balloon. How does the inhaled oxygen get into the bloodstream? The exchange of gasses between the lungs and the blood happens in tiny sacs called alveoli. The walls of the alveoli are very thin and allow gases to pass though them. The alveoli are lined with capillaries (Figure 1.2). Oxygen moves from the alveoli to the blood in the capillaries that surround the alveoli. At the same time, carbon dioxide moves in the opposite direction, from capillary blood to the alveoli. The gases move by simple diffusion, passing from an area of high concentration to an area of low concentration. For example, initially there is more oxygen in the alveoli than in the blood, so oxygen moves by diffusion from the alveoli into the blood. | text | null |
L_0661 | respiration | T_3341 | The process of getting oxygen into the body and releasing carbon dioxide is called respiration. Sometimes breathing is called respiration, but there is much more to respiration than just breathing. Breathing is only the movement of oxygen into the body and carbon dioxide out of the body. The process of respiration also includes the exchange of oxygen and carbon dioxide between the blood and the cells of the body. | text | null |
L_0662 | respiratory system diseases | T_3342 | Respiratory diseases are diseases of the lungs, bronchial tubes, trachea, nose, and throat ( Figure 1.1). These diseases can range from a mild cold to a severe case of pneumonia. Respiratory diseases are common. Many are easily treated, while others may cause severe illness or death. Some respiratory diseases are caused by bacteria or viruses, while others are caused by environmental pollutants, such as tobacco smoke. Some diseases are genetic and, therefore, are inherited. This boy is suffering from whooping cough (also known as pertussis), which gets its name from the loud whooping sound that is made when the person inhales during a coughing fit. | text | null |
L_0662 | respiratory system diseases | T_3343 | Bronchitis is an inflammation of the bronchi, the air passages that conduct air into the lungs. The bronchi become red and swollen with infection. Acute bronchitis is usually caused by viruses or bacteria, and may last several days or weeks. It is characterized by a cough that produces phlegm, or mucus. Symptoms include shortness of breath and wheezing. Acute bronchitis is usually treated with antibiotics. | text | null |
L_0662 | respiratory system diseases | T_3344 | Asthma is a chronic illness in which the bronchioles, the tiny branches into which the bronchi are divided, become inflamed and narrow ( Figure 1.2). The muscles around the bronchioles contract, which narrows the airways. Large amounts of mucus are also made by the cells in the lungs. People with asthma have difficulty breathing. Their chests feel tight, and they wheeze. Asthma can be caused by different things, such as allergies. Asthma can also be caused by cold air, warm air, moist air, exercise, or stress. The most common asthma triggers are illnesses, like the common cold. Asthma is not contagious and cannot be passed on to other people. Children and adolescents who have asthma can still lead active lives if they control their asthma. Asthma can be controlled by taking medication and by avoiding contact with environmental triggers for asthma, like smoking. | text | null |
L_0662 | respiratory system diseases | T_3345 | Pneumonia is an illness that occurs when the alveoli, the tiny sacs in the lungs where gas exchange takes place, become inflamed and filled with fluid. When a person has pneumonia, gas exchange cannot occur properly across the alveoli. Pneumonia can be caused by many things. Infection by bacteria, viruses, fungi, or parasites can cause pneumonia. An injury caused by chemicals or a physical injury to the lungs can also cause pneumonia. Symptoms of pneumonia include cough, chest pain, fever, and difficulty breathing. Treatment depends on the cause of pneumonia. Bacterial pneumonia is treated with antibiotics. Pneumonia is a common illness that affects people in all age groups. It is a leading cause of death among the elderly and people who are chronically and terminally ill. | text | null |
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