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L_0446 | animal behaviors | T_2706 | Barking, purring, and playing are just some of the ways in which dogs and cats behave. These are examples of animal behaviors. Animal behavior is any way that animals act, either alone or with other animals. | text | null |
L_0446 | animal behaviors | T_2707 | Can you think of examples of animal behaviors? What about insects and birds? How do they behave? Pictured below are just some of the ways in which these, and other animals act ( Figure 1.1). Look at the pictures and read about the behaviors. Think about why the animal is behaving that way. These pictures show examples of animal behaviors. Why do the animals behave these ways? | text | null |
L_0446 | animal behaviors | T_2708 | Why do animals behave the way they do? The answer to this question depends on what the behavior is. A cat chases a mouse to catch it. A mother dog nurses her puppies to feed them. All of these behaviors have the same purpose: getting or providing food. All animals need food for energy. They need energy to move around. In fact, they need energy just to stay alive. Energy allows all the processes inside cells to occur. Baby animals also need energy to grow and develop. Birds and wasps build nests to have a safe place to store their eggs and raise their young. Many other animals build nests for the same reason. Animals protect their young in other ways, as well. For example, a mother dog not only nurses her puppies. She also washes them with her tongue and protects them from strange people or other animals. All of these behaviors help the young survive and grow up to be adults. Rabbits run away from foxes and other predators to stay alive. Their speed is their best defense. Lizards sun themselves on rocks to get warm because they cannot produce their own body heat. When they are warmer, they can move faster and be more alert. This helps them escape from predators and also find food. All of these animal behaviors are important. They help the animals get food for energy, make sure their young survive, or ensure that they, themselves, survive. Behaviors that help animals or their young survive, increase the animals fitness. Animals with higher fitness have a better chance of passing their genes on to the next generation. If genes control behaviors that increase fitness, the behaviors become more common in the species. This occurs through the process of evolution by natural selection. | text | null |
L_0447 | animal communication | T_2709 | What does the word "communication" make you think of? Talking on a cell phone? Texting? Writing? Those are just a few of the ways in which human beings communicate. Most other animals also communicate. Communication is any way in which animals share information, and they do this in many different ways. Do all animals talk to each other? Probably not, but many do communicate. Like human beings, many other animals live together in groups. Some insects, including ants and bees, are well known for living in groups. In order for animals to live together in groups, they must be able to communicate with each other. Animal communication, like most other animal behaviors, increases the ability to survive and have offspring. This is known as fitness. Communication increases fitness by helping animals find food, defend themselves from predators, mate, and care for offspring. | text | null |
L_0447 | animal communication | T_2710 | Some animals communicate with sound. Most birds communicate this way. Birds use different calls to warn other birds of danger, or to tell them to flock together. Many other animals also use sound to communicate. For example, monkeys use warning cries to tell other monkeys in their troop that a predator is near. Frogs croak to attract female frogs as mates. Gibbons use calls to tell other gibbons to stay away from their area. | text | null |
L_0447 | animal communication | T_2711 | Another way some animals communicate is with sight. By moving in certain ways or by making faces, they show other animals what they mean. Most primates communicate in this way. For example, a male chimpanzee may raise his arms and stare at another male chimpanzee. This warns the other chimpanzee to keep his distance. The chimpanzee pictured below may look like he is smiling, but he is really showing fear ( Figure 1.1). He is communicating to other chimpanzees that he will not challenge them. Look at the peacock pictured below ( Figure 1.2). Why is he raising his beautiful tail feathers? He is also communicating. He is showing females of his species that he would be a good mate. This peacock is using his tail feathers to communicate. What is he "saying"? | text | null |
L_0447 | animal communication | T_2711 | Another way some animals communicate is with sight. By moving in certain ways or by making faces, they show other animals what they mean. Most primates communicate in this way. For example, a male chimpanzee may raise his arms and stare at another male chimpanzee. This warns the other chimpanzee to keep his distance. The chimpanzee pictured below may look like he is smiling, but he is really showing fear ( Figure 1.1). He is communicating to other chimpanzees that he will not challenge them. Look at the peacock pictured below ( Figure 1.2). Why is he raising his beautiful tail feathers? He is also communicating. He is showing females of his species that he would be a good mate. This peacock is using his tail feathers to communicate. What is he "saying"? | text | null |
L_0447 | animal communication | T_2712 | Some animals communicate with scent. They release chemicals that other animals of their species can smell or detect in some other way. Ants release many different chemicals. Other ants detect the chemicals with their antennae. This explains how ants are able to work together. The different chemicals that ants produce have different meanings. Some of the chemicals signal to all of the ants in a group to come together. Other chemicals warn of danger. Still other chemicals mark trails to food sources. When an ant finds food, it marks the trail back to the nest by leaving behind a chemical on the ground. Other ants follow the chemical trail to the food. Many other animals also use chemicals to communicate. You have probably seen male dogs raise their leg to urinate on a fire hydrant or other object. Did you know that the dogs were communicating? They mark their area with a chemical in their urine. Other dogs can smell the chemical. The scent of the chemical tells other dogs to stay away. | text | null |
L_0447 | animal communication | T_2713 | Like other animals, humans communicate with one another. They mainly use sound and sight to share information. The most important way in which humans communicate is with language. Language is the use of symbols to communicate. In human languages, the symbols are words. They stand for many different things. Words stand for things, people, actions, feelings, or ideas. Think of several common words. What does each word stand for? Another important way in which humans communicate is with facial expressions. Look at the face of the young child pictured below ( Figure 1.3). Can you tell from her face how she is feeling? Humans also use gestures to communicate. What are people communicating when they shrug their shoulders? When they shake their head? These are just a few examples of the ways in which humans share information without using words. What does this girls face say about how she is feeling? | text | null |
L_0448 | animal like protists | T_2714 | Animal-like protists are called protozoa. Protozoa are single-celled eukaryotes that share some traits with animals. Like animals, they can move, and they are heterotrophs. That means they eat things outside of themselves instead of producing their own food. Animal-like protists are very small, measuring only about 0.010.5mm. Animal-like protists include the flagellates, ciliates, and the sporozoans. | text | null |
L_0448 | animal like protists | T_2715 | There are many different types of animal-like protists. They are different because they move in different ways. Flagellates have long flagella, or tails. Flagella rotate in a propeller-like fashion, pushing the protist through its environment ( Figure 1.1). An example of a flagellate is Trypanosoma, which causes African sleeping sickness. Other protists have what are called transient pseudopodia, which are like temporary feet. The cell surface extends out to form feet-like structures that propel the cell forward. An example of a protist with pseudopodia is the amoeba. The ciliates are protists that move by using cilia. Cilia are thin, very small tail-like projections that extend outward from the cell body. Cilia beat back and forth, moving the protist along. Paramecium has cilia that propel it. The sporozoans are protists that produce spores, such as the toxoplasma. These protists do not move at all. The spores develop into new protists. These flagellates all cause diseases in humans. A video of the animal-like amoeba can be viewed at: http://commons.wikimedia.org/wiki/File:Amoeba_engulfing_ | text | null |
L_0450 | arachnids | T_2721 | Arachnids are a class of joint-legged invertebrates in the subphylum Chelicerata. They live mainly on land but are also found in fresh water and in all marine environments, except for the open ocean. There are over 100,000 named species, including many species of spiders, scorpions, daddy-long-legs, ticks, and mites ( Figure 1.1). There may be up to 600,000 species in total, including unknown ones. | text | null |
L_0450 | arachnids | T_2722 | Arachnids have the following characteristics: 1. Four pairs of legs (eight total). You can tell the difference between an arachnid and an insect because insects have three pairs of legs (six total). 2. Arachnids also have two additional pairs of appendages. The first pair, the chelicerae, serve in feeding and defense. The next pair, the pedipalps, help the organisms feed, move, and reproduce. (left) A daddy-long-legs spider. (right) Various diseases are caused by bacteria that are spread to humans by arachnids, like the tick shown here. 3. 4. 5. 6. 7. 8. 9. Arachnids do not have antennae or wings. The arachnid body is organized into the cephalothorax, a fusion of the head and thorax, and the abdomen. To adapt to living on land, arachnids have internal breathing systems, like a trachea or a book lung. Arachnids are mostly carnivorous, feeding on the pre-digested bodies of insects and other small animals. Several groups are venomous. They release the venom from specialized glands to kill prey or enemies. Several mites are parasitic, and some of those are carriers of disease. Arachnids usually lay eggs, which hatch into immature arachnids that are similar to adults. Scorpions, however, give birth to live young. | text | null |
L_0450 | arachnids | T_2723 | The arachnids are divided into eleven subgroups. Below are the four most familiar subgroups, with a description of each ( Table 1.1). Subgroup Representative Organisms Approximate Number of Species Characteristics Subgroup Araneae Representative Organisms Spiders Approximate Number of Species 40,000 Characteristics Found all over the world, ranging from tropics to the Arctic, some in extreme environments. All produce silk, which is used for trapping insects in webs, aiding in climbing, producing egg sacs, and wrapping prey. Nearly all spiders inject venom to protect themselves or to kill prey. Only about 200 species have bites that can be harmful to humans. Subgroup Opiliones Representative Organisms Daddy-long-legs Approximate Number of Species 6,300 Characteristics Known for extremely long walking legs. No silk nor poison glands. Many are omnivores, eating small insects, plant material, and fungi. Some are scavengers, eating decaying animal and other matter. Mostly nocturnal (come out at night) and colored in hues of brown. A number of diurnal (come out during the day) species have vivid patterns of yellow, green, and black. Subgroup Scorpiones Representative Organisms Scorpions Approximate Number of Species 2,000 Characteristics Characterized by a tail with six segments, the last bearing a pair of venom glands and a venom-injecting barb. Predators of small arthropods and insects. They use pincers to catch prey. Then they either crush it or inject it with a fast-acting venom, which is used to kill or paralyze the prey. Only a few species are harmful to humans. Nocturnal; during the day, they find shelter in holes or under rocks. Unlike the majority of arachnids, scorpions produce live young. The young are carried about on the mothers back until they have molted at least once. They reach an age of between four to 25 years. Subgroup Acarina Representative Organisms Mites and ticks Approximate Number of Species 30,000 Characteristics Most are small (no more than 1.0 mm in length), but some ticks, and one species of mite, may grow to be 10-20 mm in length. Live in nearly ev- ery habitat, includ- ing aquatic and ter- restrial. Many are parasitic, affecting both in- vertebrates and ver- tebrates. They may transmit diseases to humans and other mammals. Those that feed on plants may damage crops. | text | null |
L_0452 | arthropods | T_2727 | How often do you think you see an arthropod? Well, have you ever looked up close at an ant? A spider? A fly? A moth? With over a million described species (and many more yet to be described) in the phylum containing arthro- pods, chances are, you encounter one of these organisms every day, without even leaving your house. Arthropods are a very diverse group of animals. In fact, they are the biggest group of animals on the planet, with upwards of 5 million distinct species. | text | null |
L_0452 | arthropods | T_2728 | Arthropods belong to the phylum Arthropoda, which means jointed feet, and includes four living subphyla. Chelicerata, which includes spiders ( Figure 1.1), mites, and scorpions. In these animals, the first pair of appendages are often modified as fangs or pincers, and are used to manipulate food. Spiders have eight legs. Myriapoda, which includes centipedes and millipedes. All of these animals live on land, and can have anywhere from ten to nearly 200 pairs of appendages. Hexapoda, which includes the insects. These animals dominate the land. All hexapods have three pairs (six appendages) of walking appendages. Crustacea, which includes lobsters, crabs, barnacles, crayfish, and shrimp. These animals dominate the ocean, and usually have a set of anterior appendages that are modified as mandibles, which function in grasping, biting, and chewing food. Spiders are one type of arthropod. | text | null |
L_0452 | arthropods | T_2729 | Characteristics of arthropods include: 1. A segmented body ( Figure 1.2) with a head, a thorax, and abdomen segments. 2. Appendages on at least one segment. They can be used for feeding, sensory reception, defense, and locomo- tion. In addition to legs, antennas and mouth parts are considered modified appendages. 3. A nervous system. 4. A hard exoskeleton made of chitin, which gives them physical protection and resistance to drying out. In order to grow, arthropods shed this outer covering in a process called molting. 5. An open circulatory system with hemolymph, a blood-like fluid. A series of hearts move the hemolymph into the body cavity where it comes in direct contact with the tissues. Hemolymph is involved with oxygen distribution. 6. A complete digestive system with a mouth and an anus. 7. Aquatic arthropods use gills to exchange gases. These gills have a large surface area in contact with the water, so they can absorb more oxygen. 8. Land-living arthropods have internal surfaces that help exchange gasses. Insects and most other terrestrial species have a tracheal system, where air sacs lead into the body from pores in the exoskeleton. These pores cover a large part of their external body surface. Others use book lungs, gills modified for breathing air, as seen in species like the coconut crab. Some areas of the legs of soldier crabs are covered with an oxygen absorbing skin. Land crabs sometimes have two different structures: one used for breathing underwater, and another used to absorb oxygen from the air. | text | null |
L_0461 | basic and applied science | T_2759 | Science can be "basic" or "applied." The goal of basic science is to understand how things workwhether it is a single cell, an organism made of trillions of cells, or a whole ecosystem. Scientists working on basic science questions are simply looking to increase human knowledge of nature and the world around us. The knowledge obtained through the study of the subspecialties of the life sciences is mostly basic science. Basic science is the source of most scientific theories. For example, a scientist that tries to figure out how the body makes cholesterol, or what causes a particular disease, is performing basic science. This is also known as basic research. Additional examples of basic research would be investigating how glucose is turned into cellular energy or determining how elevated blood glucose levels can be harmful. The study of the cell (cell biology), the study of inheritance (genetics), the study of molecules (molecular biology), the study of microorganisms and viruses (microbiology and virology), the study of tissues and organs (physiology) are all types of basic research, and have all generated lots of information that is applied to humans and human health. Applied science is using scientific discoveries, such as those from basic research, to solve practical problems. For example, medicine, and all that is known about how to treat patients, is applied science based on basic research ( Figure 1.1). A doctor administering a drug to lower a persons cholesterol is an example of applied science. Applied science also creates new technologies based on basic science. For example, designing windmills to capture wind energy is applied science ( Figure 1.2). This technology relies, however, on basic science. Studies of wind patterns and bird migration routes help determine the best placement for the windmills. Surgeons operating on a person, an example of applied science. Windmills capturing energy, an example of applied science. | text | null |
L_0461 | basic and applied science | T_2759 | Science can be "basic" or "applied." The goal of basic science is to understand how things workwhether it is a single cell, an organism made of trillions of cells, or a whole ecosystem. Scientists working on basic science questions are simply looking to increase human knowledge of nature and the world around us. The knowledge obtained through the study of the subspecialties of the life sciences is mostly basic science. Basic science is the source of most scientific theories. For example, a scientist that tries to figure out how the body makes cholesterol, or what causes a particular disease, is performing basic science. This is also known as basic research. Additional examples of basic research would be investigating how glucose is turned into cellular energy or determining how elevated blood glucose levels can be harmful. The study of the cell (cell biology), the study of inheritance (genetics), the study of molecules (molecular biology), the study of microorganisms and viruses (microbiology and virology), the study of tissues and organs (physiology) are all types of basic research, and have all generated lots of information that is applied to humans and human health. Applied science is using scientific discoveries, such as those from basic research, to solve practical problems. For example, medicine, and all that is known about how to treat patients, is applied science based on basic research ( Figure 1.1). A doctor administering a drug to lower a persons cholesterol is an example of applied science. Applied science also creates new technologies based on basic science. For example, designing windmills to capture wind energy is applied science ( Figure 1.2). This technology relies, however, on basic science. Studies of wind patterns and bird migration routes help determine the best placement for the windmills. Surgeons operating on a person, an example of applied science. Windmills capturing energy, an example of applied science. | text | null |
L_0462 | biotechnology in agriculture | T_2760 | Energy must constantly flow through an ecosystem for the system to remain stable. What exactly does this mean? Essentially, it means that organisms must eat other organisms. Food chains ( Figure 1.1) show the eating patterns in an ecosystem. Food energy flows from one organism to another. Arrows are used to show the feeding relationship between the animals. The arrow points from the organism being eaten to the organism that eats it. For example, an arrow from a plant to a grasshopper shows that the grasshopper eats the leaves. Energy and nutrients are moving from the plant to the grasshopper. Next, a bird might prey on the grasshopper, a snake may eat the bird, and then an owl might eat the snake. The food chain would be: plant grasshopper bird snake owl. A food chain cannot continue to go on and on. For example the food chain could not be: plant grasshopper spider frog lizard fox hawk. Food chains only have 4 or 5 total levels. Therefore, a chain has only 3 or 4 levels for energy transfer. This food chain includes producers and consumers. How could you add decom- posers to the food chain? In an ocean ecosystem, one possible food chain might look like this: phytoplankton krill fish shark. The producers are always at the beginning of the food chain, bringing energy into the ecosystem. Through photosynthesis, the producers create their own food in the form of glucose, but also create the food for the other organisms in the ecosystem. The herbivores come next, then the carnivores. When these consumers eat other organisms, they use the glucose in those organisms for energy. In this example, phytoplankton are eaten by krill, which are tiny, shrimp-like animals. The krill are eaten by fish, which are then eaten by sharks. Could decomposers be added to a food chain? Each organism can eat and be eaten by many different types of organisms, so simple food chains are rare in nature. There are also many different species of fish and sharks. So a food chain cannot end with a shark; it must end with a distinct species of shark. A food chain does not contain the general category of "fish," it will contain specific species of fish. In ecosystems, there are many food chains. Since feeding relationships are so complicated, we can combine food chains together to create a more accurate flow of energy within an ecosystem. A food web ( Figure 1.2) shows the feeding relationships between many organisms in an ecosystem. If you expand our original example of a food chain, you could add deer that eat clover and foxes that hunt chipmunks. A food web shows many more arrows, but still shows the flow of energy. A complete food web may show hundreds of different feeding relationships. | text | null |
L_0463 | bird reproduction | T_2761 | How do birds reproduce? We know that chickens lay eggs. But how do they do that? It all starts with behavior aimed at attracting a mate. In birds, this will involve a type of display, usually performed by the male. Some displays are very elaborate and may include dancing, aerial flights, or wing or tail drumming. Most male birds also sing a type of song to attract females. If they are successful at attracting a female, it will lead to breeding. Birds reproduce by internal fertilization, during which the egg is fertilized inside the female. Like reptiles, birds have cloaca, or a single exit and entrance for sperm, eggs, and waste. The male brings his sperm to the female cloaca. The sperm fertilizes the egg. Then the hard-shelled egg develops within the female. The hard-shelled eggs have a fluid-filled amnion, a thin membrane forming a closed sac around the embryo. Eggs are usually laid in a nest. | text | null |
L_0463 | bird reproduction | T_2762 | Why do you think eggs come in so many different colors? Birds that make nests in the open have camouflaged eggs ( Figure 1.1). This gives the eggs protection against predation. Some species, like ground-nesting nightjars, have pale eggs, but the birds camouflage the eggs with their feathers. To protect their young, different species of birds make different nests. Birds of all types, from hummingbirds to ostriches, make nests. Many can be elaborate, shaped like cups, domes, plates, mounds, or burrows. However, some birds, like the common guillemot, do not use nests. Instead, they lay their eggs on bare cliffs. Emperor penguins do not have a nest at all; they sit on eggs to keep them warm before they hatch, a process called incubation. How else might a bird help protect its young from predators? Most species locate their nests in areas that are hidden, in order to avoid predators. Large birds, or those that nest in groups, may build nests in the open, since they are more capable of defending their young. Nest and eggs of the common moorhen, showing camouflaged eggs. | text | null |
L_0463 | bird reproduction | T_2763 | In birds, 90% to 95% of species are monogamous, meaning the male and female remain together for breeding for a few years or until one mate dies. Birds of all types, from parrots to eagles and falcons, are monogamous. Usually, the parents take turns incubating the eggs. Birds usually incubate their eggs after the last one has been laid. In polygamous species, where there is more than one mate, one parent does all of the incubating. The wild turkey is an example of a polygamous bird. The length and type of parental care varies widely amongst different species of birds. At one extreme, in a group of birds called the magapodes (which are chicken-like birds), parental care ends at hatching. In this case, the newly- hatched chick digs itself out of the nest mound without parental help and can take care of itself right away. These birds are called precocial. Other precocial birds include the domestic chicken and many species of ducks and geese. At the other extreme, many seabirds care for their young for extended periods of time. For example, the chicks of the Great Frigatebird receive intensive parental care for six months, or until they are ready to fly, and then take an additional 14 months of being fed by the parents ( Figure 1.2). These birds are the opposite of precocial birds and are called altricial. In most animals, male parental care is rare. But it is very common in birds. Often both parents share tasks such as defense of territory and nest site, incubation, and the feeding of chicks. Since birds often take great care of their young, some birds have evolved a behavior called brood parasitism. This happens when a bird leaves her eggs in another birds nest. The host bird often accepts and raises the parasite birds eggs. Great Frigatebird adults are known to care for their young for up to 20 months after hatching, the longest in a bird species. Here, a young bird is begging for food. | text | null |
L_0464 | birds | T_2764 | How many different types of birds can you think of? Robins, ostriches, hummingbirds, chickens, and eagles. All of these are birds, but they are very different from one another. There is an amazingly wide variety of birds. Like amphibians, reptiles, mammals, and fish, birds are vertebrates. What does that mean? It means they have a backbone. Almost all birds have forelimbs modified as wings, but not all birds can fly. In some birds, the wings have evolved into other structures. Birds are in the class Aves. All birds have the following key features: they are endothermic (warm-blooded), have two legs, and lay eggs. Birds range in size from the tiny two-inch bee hummingbird to the nine-foot ostrich ( Figure 1.1). With approxi- mately 10,000 living species, birds are the most numerous vertebrates with four limbs. They live in diverse habitats around the globe, from the Arctic to the Antarctic. The ostrich can reach a height of nine feet! Pictured here is an ostrich with her young in the Negev Desert, southern Israel. | text | null |
L_0464 | birds | T_2765 | The digestive system of birds is unique, with a gizzard that contains swallowed stones for grinding food. Birds do not have teeth. What do you think the stones do? They help them digest their food. Defining characteristics of modern birds also include: Feathers. High metabolism. A four-chambered heart. A beak with no teeth. A lightweight but strong skeleton. Production of hard-shelled eggs. Which of the above traits do you think might be of importance to flight? | text | null |
L_0464 | birds | T_2766 | In comparing birds with other vertebrates, what do you think distinguishes them the most? In most birds, flight is the obvious difference. Birds have adapted their body plan for flight: Their skeleton is especially lightweight, with large, air-filled spaces connecting to their respiratory system. Their neck bones are flexible. Birds that fly have a bony ridge along the breastbone that the flight muscles attach to ( Figure 1.2). This allows them to remain stable in the air as they fly. Birds also have wings that function as an aerofoil. The surface of the aerofoil is curved to help the bird control and use the air currents to fly. Aerofoils are also found on the wings of airplanes. A bony ridge along the breastbone (green) allows birds to remain stable as they fly. What other traits do you think might be important for flight? Feathers help because theyre more lightweight than scales or fur. A birds wing shape and size will determine how a species flies. For example, many birds have powered flight at certain times, requiring the flapping of their wings, while at other times they soar, using up less energy ( Figure 1.3). One birds flight. A flightless cormorant can no longer fly, but it uses its wings for swimming. | text | null |
L_0464 | birds | T_2766 | In comparing birds with other vertebrates, what do you think distinguishes them the most? In most birds, flight is the obvious difference. Birds have adapted their body plan for flight: Their skeleton is especially lightweight, with large, air-filled spaces connecting to their respiratory system. Their neck bones are flexible. Birds that fly have a bony ridge along the breastbone that the flight muscles attach to ( Figure 1.2). This allows them to remain stable in the air as they fly. Birds also have wings that function as an aerofoil. The surface of the aerofoil is curved to help the bird control and use the air currents to fly. Aerofoils are also found on the wings of airplanes. A bony ridge along the breastbone (green) allows birds to remain stable as they fly. What other traits do you think might be important for flight? Feathers help because theyre more lightweight than scales or fur. A birds wing shape and size will determine how a species flies. For example, many birds have powered flight at certain times, requiring the flapping of their wings, while at other times they soar, using up less energy ( Figure 1.3). One birds flight. A flightless cormorant can no longer fly, but it uses its wings for swimming. | text | null |
L_0464 | birds | T_2766 | In comparing birds with other vertebrates, what do you think distinguishes them the most? In most birds, flight is the obvious difference. Birds have adapted their body plan for flight: Their skeleton is especially lightweight, with large, air-filled spaces connecting to their respiratory system. Their neck bones are flexible. Birds that fly have a bony ridge along the breastbone that the flight muscles attach to ( Figure 1.2). This allows them to remain stable in the air as they fly. Birds also have wings that function as an aerofoil. The surface of the aerofoil is curved to help the bird control and use the air currents to fly. Aerofoils are also found on the wings of airplanes. A bony ridge along the breastbone (green) allows birds to remain stable as they fly. What other traits do you think might be important for flight? Feathers help because theyre more lightweight than scales or fur. A birds wing shape and size will determine how a species flies. For example, many birds have powered flight at certain times, requiring the flapping of their wings, while at other times they soar, using up less energy ( Figure 1.3). One birds flight. A flightless cormorant can no longer fly, but it uses its wings for swimming. | text | null |
L_0466 | blood pressure | T_2772 | The health of your whole body depends on the good health of your cardiovascular system. One measure of the health of your cardiovascular system is blood pressure. Blood pressure occurs when circulating blood puts pressure on the walls of blood vessels. Since blood pressure is primarily caused by the beating of your heart, the walls of the arteries move in a rhythmic fashion. Blood in arteries is under the greatest amount of pressure. The pressure of the circulating blood slowly decreases as blood moves from the arteries and into the smaller blood vessels. Blood in veins is not under much pressure. | text | null |
L_0466 | blood pressure | T_2773 | Blood pressure is read as two numbers. The first number is the systolic pressure. The systolic pressure is the pressure on the blood vessels when the heart beats. This is the time when there is the highest pressure in the arteries. The diastolic pressure, which is the second number, is when your blood pressure is lowest, when the heart is resting between beats. Healthy ranges for blood pressure are: Systolic: less than 120 Diastolic: less than 80 Blood pressure is written as systolic/diastolic. For example, a reading of 120/80 is said as "one twenty over eighty." These measures of blood pressure can change with each heartbeat and over the course of the day. Pressure varies with exercise, emotions, sleep, stress, nutrition, drugs, or disease. Studies have shown that people whose systolic pressure is around 115, rather than 120, have fewer health problems. Clinical trials have shown that people who have blood pressures at the low end of these ranges have much better long term cardiovascular health. Blood pressure is measured with a sphygmomanometer ( Figure 1.1). A digital sphygmomanometer is made of an inflatable cuff and a pressure meter to measure blood pressure. This reading shows a blood pressure of 126/70. Hypertension, which is also called "high blood pressure," occurs when a persons blood pressure is always high. Hypertension is said to be present when a persons systolic blood pressure is always 140 or higher, and/or if the persons diastolic blood pressure is always 90 or higher. Having hypertension increases a persons chance for developing heart disease, having a stroke, or suffering from other serious cardiovascular diseases. Hypertension often does not have any symptoms, so a person may not know that he or she has high blood pressure. For this reason, hypertension is often called the "silent killer." Treatments for hypertension include diet changes, exercise, and medication. Foods thought to lower blood pressure include skim milk, spinach, beans, bananas and dark chocolate. Some health conditions, as well as a persons lifestyle and genetic background, can put someone at a higher risk for developing high blood pressure. As a person cannot alter their genetic background, lifestyle changes may be necessary to reduce the chance of developing high blood pressure. These changes include getting enough exercise, limiting the amount of sodium (salt) in the diet, not being overweight, not drinking alcohol to excess, and not smoking. Low blood pressure is not usually a concern, as long as there are no problems associated with the low pressure. Symptoms associated with low blood pressure include dizziness or lightheadedness, fainting, dehydration and unusual thirst, lack of concentration, blurred vision, nausea, and fatigue. | text | null |
L_0482 | centipedes and millipedes | T_2819 | Centipedes and millipedes belong to the subphylum Myriapoda, which contains 13,000 species. They all live on land, which makes sense as all those legs are more adapted to a terrestrial lifestyle, as opposed to an aquatic lifestyle. The Myriapoda are divided among four classes: (1) Chilopoda (centipedes), (2) Diplopoda (millipedes), (3) Sym- phyla (symphylans), and (4) Pauropoda (pauropods). They range from having over 750 legs to having fewer than ten legs. They have a single pair of antennae and simple eyes. | text | null |
L_0482 | centipedes and millipedes | T_2820 | Myriapoda are mostly found in moist forests, where they help to break down decaying plant material. A few live in grasslands, semi-arid habitats, or even deserts. Most myriapods are decomposers, with the majority herbivores breaking down decaying plant material, but centipedes are nighttime predators. Centipedes roam around looking for small animals to bite and eat; their prey includes insects, spiders, and other small invertebrates. If the centipede is large enough, it will even attack small vertebrates, like lizards. Although not generally considered dangerous to humans, many from this group can cause temporary blistering and discoloration of the skin. | text | null |
L_0482 | centipedes and millipedes | T_2821 | Centipedes ("hundred feet") ( Figure 1.1) are fast, predatory carnivores, and venomous. There are around 3,300 described species, ranging from one tiny species (less than half an inch in length) to one giant species (the Peruvian giant yellow-leg centipede or Amazonian giant centipede), which may grow larger than 12 inches. This giant centipede has been known to attack, kill and eat much larger animals, including tarantulas. Centipedes have one pair of legs per body segment, with the first pair of legs behind the head modified into a pair of fangs containing a poison gland. Many centipedes also guard their eggs and young by curling around them. Centipede. | text | null |
L_0482 | centipedes and millipedes | T_2822 | Most millipedes are slower than centipedes and feed on leaf litter and loose organic material. They can be distin- guished from centipedes by looking at the number of legs per body segment. Millipedes have two pairs of legs per body segment, while centipedes have a single pair of legs per body segment. Millipedes protect their eggs from predators by using a nest of hard soil. Millipedes are not poisonous. They lack the pair of fangs containing a poison gland that centipedes have. | text | null |
L_0482 | centipedes and millipedes | T_2823 | The third class, Symphyla, contains 200 species. Symphylans resemble centipedes but are smaller and translucent. These arthropods have an elongated body, with three pairs of thoracic legs and about nine pairs of abdominal legs, giving this class 12 pairs total. Many spend their lives in soil feeding on plant roots, but some do live in trees. | text | null |
L_0482 | centipedes and millipedes | T_2824 | The pauropods are typically 0.5-2.0 mm long and live on all continents except Antarctica. They are usually found in soil, leaf litter, or other moist places. They feed on fungi and decaying organic matter, and are essentially harmless. Adult pauropods have 11 or 12 body segments and 9-11 pairs of legs. They also possess unique forked antennae and a distinctive pattern of movement characterized by rapid burst of movement and frequent abrupt changes in direction. Over 700 species have been described, and they are believed to be closely related to millipedes. | text | null |
L_0486 | choosing healthy foods | T_2838 | Foods such as whole grain breads, fresh fruits, and fish provide nutrients you need for good health. But different foods give you different types of nutrients. You also need different amounts of each nutrient. How can you choose the right mix of foods to get the proper balance of nutrients? Three tools can help you choose foods wisely: MyPyramid, MyPlate, and food labels. | text | null |
L_0486 | choosing healthy foods | T_2839 | MyPyramid ( Figure 1.1) is a diagram that shows how much you should eat each day of foods from six different food groups. It recommends the amount of nutrients you need based on your age, your gender, and your level of activity. The six food groups in MyPyramid are: Grains, such as bread, rice, pasta, and cereal. Vegetables, such as spinach, broccoli, carrots, and sweet potatoes. Fruits, such as oranges, apples, bananas, and strawberries. Oils, such as vegetable oil, canola oil, olive oil, and peanut oil. Dairy, such as milk, yogurt, cottage cheese, and other cheeses. Meat and beans, such as chicken, fish, soybeans, and kidney beans. MyPyramid can help you choose foods wisely for good health. Each colored band represents a different food group. The key shows which food group each color represents. Which colored band of MyPyramid is widest? Which food group does it represent? In MyPyramid, each food group is represented by a band of a different color. For example, grains are represented by an orange band, and vegetables are represented by a green band. The wider the band, the more foods you should choose from that food group each day. The orange band in MyPyramid is the widest band. This means that you should choose more foods from the grain group than from any other single food group. The green, blue, and red bands are also relatively wide. Therefore, you should choose plenty of foods from the vegetable, dairy, and fruit groups as well. You should choose the fewest foods from the food group with the narrowest band. Which band is narrowest? Which food group does it represent? Are you wondering where foods like ice cream, cookies, and potato chips fit into MyPyramid? The white tip of MyPyramid represents foods such as these. These are foods that should be eaten only in very small amounts and not very often. Such foods contain very few nutrients and are called nutrient-poor. Instead, they are high in fats, sugars, and sodium, which are nutrients that you should limit in a healthy eating plan. Ice cream, cookies, and potato chips are also high in calories. Eating too much of them may lead to unhealthy weight gain. | text | null |
L_0486 | choosing healthy foods | T_2840 | Make at least half your daily grain choices whole grains. Examples of whole grains are whole wheat bread, whole wheat pasta, and brown rice. Choose a variety of different vegetables each day. Be sure to include both dark green vegetables, such as spinach and broccoli, and orange vegetables, such as carrots and sweet potatoes. Choose a variety of different fruits each day. Select mainly fresh fruits rather than canned fruits, and whole fruits instead of fruit juices. When choosing oils, choose unsaturated oils, such as olive oil, canola oil, or vegetable oil. Choose low-fat or fat-free milk and other dairy products. For example, select fat-free yogurt and low-fat cheese. For meats, choose fish, chicken, and lean cuts of beef. Also, be sure to include beans, nuts, and seeds. | text | null |
L_0486 | choosing healthy foods | T_2841 | In June 2011, the United States Department of Agriculture replaced My Pyramid with MyPlate. MyPlate depicts the relative daily portions of various food groups ( Figure 1.2). See for more information. MyPlate is a visual guideline for balanced eating, replacing MyPyramid in 2011. The following guidelines accompany MyPlate: 1. Balancing Calories Enjoy your food, but eat less. Avoid oversized portions. 2. Foods to Increase Make half your plate fruits and vegetables. Make at least half your grains whole grains. Switch to fat-free or low-fat (1%) milk. 3. Foods to Reduce | text | null |
L_0486 | choosing healthy foods | T_2842 | In the United States and other nations, packaged foods are required by law to have nutrition facts labels. A nutrition facts label ( Figure 1.3) shows the nutrients in a food. Packaged foods are also required to list their ingredients. The information listed at the right of the label tells you what to look for. At the top of the label, look for the serving size. The serving size tells you how much of the food you should eat to get the nutrients listed on the label. A cup of food from the label pictured below is a serving. The calories in one serving are listed next. In this food, there are 250 calories per serving. Reading nutrition facts labels can help you choose healthy foods. Look at the nutrition facts label shown here. Do you think this food is a good choice for a healthy eating plan? Why or why not? Next on the nutrition facts label, look for the percent daily values (% DV) of nutrients. Remember the following tips when reading a food label: A food is low in a nutrient if the percent daily value of the nutrient is 5% or less. The healthiest foods are low in nutrients such as fats and sodium. A food is high in a nutrient if the percent daily value of the nutrient is 20% or more. The healthiest foods are high in nutrients such as fiber and proteins. | text | null |
L_0486 | choosing healthy foods | T_2843 | Look at MyPyramid ( Figure 1.1). Note the person walking up the side of the pyramid. This shows that exercise is important for balanced eating. Exercise helps you use any extra energy in the foods you eat. The more active you are, the more energy you use. You should try to get at least an hour of physical activity just about every day. Pictured below are some activities that can help you use extra energy ( Figure 1.4). | text | null |
L_0486 | choosing healthy foods | T_2844 | Any unused energy in food is stored in the body as fat. This is true whether the extra energy comes from carbohy- drates, proteins, or lipids. What happens if you take in more energy than you use, day after day? You will store more and more fat and become overweight. Eventually, you may become obese. Obesity is having a very high percentage of body fat. Obese people are at least 20 percent heavier than their healthy weight range. The excess body fat of obesity is linked to many diseases. Obese people often have serious health problems, such as diabetes, high blood pressure, and high cholesterol. They are also more likely to develop arthritis and some types of cancer. People who remain obese during their entire adulthood usually do not live as long as people who stay within a healthy weight range. The current generation of children and teens is the first generation in our history that may have a shorter life than their parents. The reason is their high rate of obesity and the health problems associated with obesity. You can avoid gaining weight and becoming obese. The choice is yours. Choose healthy foods by using MyPyramid and reading food labels. Then get plenty of exercise to balance the energy in the foods you eat. | text | null |
L_0487 | chordates | T_2845 | Did you know that fish, amphibians, reptiles, birds, and mammals are all related? They are all chordates. Chordates are a group of animals that includes vertebrates, as well as several closely related invertebrates. Chordates (phylum Chordata) are named after a feature they all share, a notochord. A notochord is a hollow nerve cord along the back. | text | null |
L_0487 | chordates | T_2846 | Chordates are defined by a set of four characteristics that are shared by these animals at some point during their development. In some chordates, all four traits are present in the adult animal and serve important functions. However, in many chordates, including humans, some traits are present only during the embryonic stage. After that, these traits may disappear. All chordates have four main traits ( Figure 1.1): 1. Post-anal tail: The tail is opposite the head and extends past the anus. 2. Dorsal hollow nerve cord: "Dorsal" means that the nerve cord runs along the top of the animal. In some animals, the nerve cord develops into the brain and spinal cord. 3. Notochord: The notochord lies below the nerve cord. It is a rigid structure where muscles attach. 4. Pharyngeal slits: Pharyngeal slits are used to filter out food from water by some simple chordates. In most chordates, however, they are only present during the embryonic stages and serve no apparent purpose. Body Plan of a Typical Chordate. The body plan of a chordate includes a post- anal tail, notochord, dorsal hollow nerve cord, and pharyngeal slits. | text | null |
L_0487 | chordates | T_2847 | The chordates are divided into nine classes. Five of the classes are the fish, amphibians, reptiles, birds, and mammals. There are actually five classes of marine chordates (for example, sharks are cartilaginous fish which are distinct from bony fish), and these will be discussed in additional concepts. The chordate phylum is broken down into three subphyla: 1. Urochordata: The tunicates, pictured in the introduction, make up this group. The urochordates are sessile (non-moving) marine animals with sack-like bodies and tubes for water movement. Urochordates have a notochord and nerve cord only during the larval stage. 2. Cephalochordata: Cephalochordates include the lancelets ( Figure 1.2), fish-like marine animals often found half-buried in the sand. Cephalochordates have a notochord and nerve cord but no backbone. 3. Vertebrata: Humans and other mammals, along with fish, amphibians, reptiles, and birds, fall in this category. In vertebrates, the notochord is typically smaller and surrounded by a backbone. The lancelet, an example of a chordate, is found in shallow ocean waters. | text | null |
L_0491 | cnidarians | T_2856 | Cnidarians, in the phylum Cnidaria, include organisms such as the jellyfish, corals, and sea anemones. These animals are found in shallow ocean water. You might know that these animals can give you a painful sting if you step on them. Thats because cnidarians have stinging cells known as nematocysts. Cnidarians use nematocysts to catch their food. When touched, the nematocysts release a thread of poison that can be used to paralyze prey. Cnidarians are among the simplest of the so-called "higher" organisms, but are also among the most beautiful. | text | null |
L_0491 | cnidarians | T_2857 | The body plan of cnidarians is unique because these organisms show radial symmetry, making these animals very different from those that evolved before them. Radial symmetry means that they have a circular body plan, and any cut through the center of the animal leaves two equal halves. The cnidarians have two basic body forms: 1. Polyp: The polyp is a cup-shaped body with the mouth facing upward, such as a sea anemone and coral. 2. Medusa: The medusa is a bell-shaped body with the mouth and tentacles facing downward, such as a jellyfish. Unlike the sponges which evolved prior to cnidarians, the cnidarians are made up of true tissues. The inside of a cnidarian is called the gastrovascular cavity, a large space that helps the organism digest and move nutrients around the body. The cnidarians also have nerve tissue organized into a net-like structure, known as a nerve-net, with connected nerve cells dispersed throughout the body. Cnidarians do not have true organs, however. Reproduction is by asexual budding (polyps) or sexual formation of gametes (medusae, some polyps). The result of sexual reproduction is a larva, which can swim on its own. | text | null |
L_0491 | cnidarians | T_2858 | Some types of cnidarians are also known to form colonies. Two examples are described below. 1. The Portuguese Man o War ( Figure 1.1) looks like a single organism but is actually a colony of polyps. One polyp is filled with air to help the colony float, while several feeding polyps hang below with tentacles. The tentacles are full of nematocysts. The Portuguese Man o War is known to cause extremely painful stings to swimmers and surfers who accidentally brush up against it in the water. 2. Coral reefs ( Figure below) look like big rocks, but they are actually alive. They are built from cnidarians called corals. The corals are sessile (non-moving) polyps that can use their tentacles to feed on ocean creatures that pass by. Their skeletons are made up of calcium carbonate, which is also known as limestone. Over long periods of time, their skeletons build on each other to produce large structures known as coral reefs. Coral reefs are important habitats for many different types of ocean life. Corals are colonial cnidarians. | text | null |
L_0492 | competition | T_2859 | Recall that ecology is the study of how living organisms interact with each other and with their environment. But how do organisms interact with each other? Organisms interact with each other through various mechanisms, one of which is competition. Competition occurs when organisms strive for limited resources. Competition can be for food, water, light, or space. This interaction can be between organisms of the same species (intraspecific) or between organisms of different species (interspecific). Intraspecific competition happens when members of the same species compete for the same resources. For example, two trees may grow close together and compete for light. One may out-compete the other by growing taller to get more available light. As members of the same species are usually genetically different, they have different characteristics, and in this example, one tree grows taller than the other. The organism that is better adapted to that environment is better able to survive. The other organism may not survive. In this example, it is the taller tree that is better adapted to the environment. Interspecific competition happens when individuals of different species strive for a limited resource in the same area. Since any two species have different traits, one species will be able to out-compete the other. One species will be better adapted to its environment, and essentially "win" the competition. The other species will have lower reproductive success and lower population growth, resulting in a lower survival rate. For example, cheetahs and lions feed on similar prey. If prey is limited, then lions may catch more prey than cheetahs. This will force the cheetahs to either leave the area or suffer a decrease in population. Looking at different types of competition, ecologists developed the competitive exclusion principle. The principle states that species less suited to compete for resources will either adapt, move from the area, or die out. In order for two species within the same area to coexist, they may adapt by developing different specializations. This is known as character displacement. An example of character displacement is when different birds adapt to eating different types of food. They can develop different types of bills, like Darwins Finches ( Figure 1.1). Therefore, competition for resources within and between species plays an important role in evolution through natural selection. An example of character displacement, showing different types of bill for eating different types of foods, in Darwins or Galapagos Finches. | text | null |
L_0495 | consumers and decomposers | T_2866 | Recall that producers make their own food through photosynthesis. But many organisms are not producers and cannot make their own food. So how do these organisms obtain their energy? They must get their energy from other organisms. They must eat other organisms, or obtain their energy from these organisms some other way. The organisms that obtain their energy from other organisms are called consumers. All animals are consumers, and they eat other organisms. Fungi and many protists and bacteria are also consumers. But, whereas animals eat other organisms, fungi, protists, and bacteria "consume" organisms through different methods. The consumers can be placed into different groups, depending on what they consume. Herbivores are animals that eat producers to get energy. For example, rabbits and deer are herbivores that eat plants. The caterpillar pictured below ( Figure 1.1) is a herbivore. Animals that eat phytoplankton in aquatic environments are also herbivores. Carnivores feed on animals, either herbivores or other carnivores. Snakes that eat mice are carnivores. Hawks that eat snakes are also carnivores ( Figure 1.1). Omnivores eat both producers and consumers. Most people are omnivores, since they eat fruits, vegetables, and grains from plants, and also meat and dairy products from animals. Dogs, bears, and raccoons are also omnivores. Examples of consumers are caterpillars (herbivores) and hawks (carnivore). | text | null |
L_0495 | consumers and decomposers | T_2867 | Decomposers ( Figure 1.2) get nutrients and energy by breaking down dead organisms and animal wastes. Through this process, decomposers release nutrients, such as carbon and nitrogen, back into the environment. These nutrients are recycled back into the ecosystem so that the producers can use them. They are passed to other organisms when they are eaten or consumed. Many of these nutrients are recycled back into the soil, so they can be taken up by the roots of plants. The stability of an ecosystem depends on the actions of the decomposers. Examples of decomposers include mushrooms on a decaying log. Bacteria in the soil are also decomposers. Imagine what would happen if there were no decomposers. Wastes and the remains of dead organisms would pile up and the nutrients within the waste and dead organisms would not be released back into the ecosystem. Producers would not have enough nutrients. The carbon and nitrogen necessary to build organic compounds, and then cells, allowing an organism to grow, would be insufficient. Other nutrients necessary for an organism to function properly would also not be sufficient. Essentially, many organisms could not exist. Examples of decomposers are (a) bacte- ria and (b) fungi. | text | null |
L_0496 | control of insects | T_2868 | Though insects can be very important, some are also considered pests. Common insect pests include: 1. 2. 3. 4. Parasitic insects, such as mosquitoes, lice, and bed bugs. Insects that transmit diseases, including mosquitoes and flies. Insects that damage structures, such as termites ( Figure 1.1). Insects that destroy crops, including locusts and weevils. Many scientists who study insects are involved in various forms of pest control. Most utilize insect-killing chemicals, but more and more rely on other methods. Ways to control insect pests are described below. | text | null |
L_0496 | control of insects | T_2869 | Biological control of pests in farming is a method of controlling pests by using other insects (or other natural predators of the pests). Biological control of insects relies on predation and parasitism. Insect predators, such as ladybugs and lacewings, consume a large number of other insects during their lifetime. If you add ladybugs to your farm or garden, they will help keep insect pests, such as aphids, under control. Aphids are among the most destructive insect pests on cultivated plants in temperate regions, so any control of these pests is beneficial. Ladybugs also consume mites, scale insects and small caterpillars. The larvae of many hoverfly species also feed upon aphids, with one larva consuming up to fifty aphids a day, which is about 1,000 in its lifetime. They also eat fruit tree spider mites and small caterpillars. Dragonflies are important predators of mosquitoes, and can be used to control this pest. Parasitic insects include insects such as wasps and flies that lay their eggs on or in the body of an insect host, which is then used as a food for developing larvae. The host is ultimately killed. Caterpillars also tend to be one likely target of parasitic wasps. | text | null |
L_0496 | control of insects | T_2870 | Chemical control of pests involves the use of insecticides. Insecticides, which are also known as pesticides, are most often used to kill insects. Insecticides are chemicals that kill insects. The U.S. spends $9 billion each year on pesticides. Disadvantages to using pesticides include human, fish, and honeybee poisonings, and the contamination of meat and dairy products. When choosing to use an insecticide, there are numerous points to consider. Negative effects of the pesticide should try to be minimized. Important questions to consider include the following. What is the chemicals success against the target pest? Will the insecticide provide the desired level of control of the pest? If the answer is no, other methods of control should be considered. Does the chemical have an impact on natural enemies of the pest? In large scale efforts to rid areas of mosquitoes, the insecticide used also killed the dragonfly. This effort removed a natural predator of the mosquito. This may be an unacceptable negative effect of using the insecticide. How susceptible is the crop to insect damage? If the crop is not heavily damaged, only minor pest control may be needed. This may affect the amount or type of insecticide used. How toxic is the chemical to the environment and humans? Some older insecticides are extremely poisonous. Keep in mind that users of these poisons have a community responsibility to minimize the contamination of the surrounding environment, as well as keeping animals, surrounding crops and humans safe. Does using the pesticide result in the development of resistance? If so, this can make additional use of the pesticide less effective. As the resistance will be passed to future generations of the insect (which is natural selection in action), this could be considered a negative side-effect of pesticide use. | text | null |
L_0497 | crustaceans | T_2871 | Crustaceans are a large group of arthropods, consisting of almost 52,000 species. The majority of crustaceans are aquatic. Some live in the ocean, while others live in fresh water. A few groups have adapted to living on land, such as land crabs, hermit crabs, and woodlice ( Figure 1.1). Crustaceans are among the most successful animals, and can be considered the dominant aquatic animals. Though small, crustaceans are numerous enough to be the main source of energy for large ocean mammals. They are found as much in the oceans as insects are on land. | text | null |
L_0497 | crustaceans | T_2872 | Six classes of crustaceans are generally recognized ( Table 1.1). Class Branchiopoda Characteristics Mostly small, freshwater animals that feed on plankton and detritus. Examples Brine shrimp Class Remipedia Cephalocarida Maxillopoda Ostracoda Malacostraca Characteristics A small class of blind organisms found in deep caves connected to salt water. Small crustaceans, with an eye- less head covered by a horseshoe- shaped shield; has two pairs of an- tennae and two pairs of jaws. Mostly small, with a small abdomen, and generally no appendages. Small animals with bivalve shells. The largest class, with the largest and most familiar animals. This class has the greatest diversity of body forms. Examples Nectiopoda Horseshoe shrimp Barnacles, copepods Seed shrimp Crabs, lobsters, woodlice shrimp, krill, A terrestrial arthropod, a species of woodlice. | text | null |
L_0497 | crustaceans | T_2873 | Remember that crustaceans are an arthropod subphylum, and that arthropod means "jointed feet." As expected, the majority of crustaceans can move. A few groups are parasitic and live attached to their hosts. Adult barnacles ( Figure 1.2) cannot move, so they attach themselves headfirst to a rock or log. | text | null |
L_0497 | crustaceans | T_2874 | Characteristics of crustaceans include: 1. An exoskeleton that may be bound together, such as in the carapace, the thick back shield seen in many crustaceans that often forms a protective space for the gills. 2. A main body cavity with an expanded circulatory system. Blood is pumped by a heart located near the back. 3. A digestive system consisting of a straight tube that has a gastric mill for grinding food and a pair of digestive glands that absorb food. 4. Structures that function like kidneys to remove wastes. These are located near the antennae. 5. A brain that exists in the form of ganglia, or connections between nerve cells. 6. Crustaceans periodically shed the outer skeleton, grow rapidly for a short time, and then form another hard skeleton. They cannot grow underneath their outer exoskeleton. They are very vulnerable during this time, as they lack their hard shell. | text | null |
L_0497 | crustaceans | T_2875 | Most crustaceans have separate sexes, so they reproduce sexually using eggs and sperm. Many land crustaceans, such as the Christmas Island red crab, mate every season and return to the sea to release the eggs. Others, such as woodlice, lay their eggs on land when the environment is damp. In some crustaceans, the females keep the eggs until they hatch into free-swimming larvae. | text | null |
L_0498 | cyclic behavior of animals | T_2876 | Many animal behaviors change in a regular way. They go through cycles. Some cycles of behavior repeat each year. Other cycles of behavior repeat every day. | text | null |
L_0498 | cyclic behavior of animals | T_2877 | An example of a behavior with a yearly cycle is hibernation. Hibernation is a state in which an animals body processes are slower than usual, and its body temperature falls. An animal uses less energy than usual during hibernation. This helps the animal survive during a time of year when food is scarce. Hibernation may last for weeks or months. Animals that hibernate include species of bats, squirrels, and snakes. Most people think that bears hibernate. In fact, bears do not go into true hibernation. In the winter, they go into a deep sleep. However, their body processes do not slow down very much. Their body temperature also remains about the same as usual. Bears can be awakened easily from their winter sleep. Another example of a behavior with a yearly cycle is migration. Migration is the movement of animals from one place to another. Migration is an innate behavior that is triggered by changes in the environment. For example, animals may migrate when the days get shorter in the fall. Migration is most common in birds, fish, and insects. In the Northern Hemisphere, many species of birds, including robins and geese, travel south for the winter. They migrate to areas where it is warmer and where there is more food. They return north in the spring. A flock of migrating geese is pictured below ( Figure 1.1). These geese are flying south for the win- ter. Flocks of geese migrate in V-shaped formations. Some animals migrate very long distances. The map shown below shows the migration route of a species of hawk called Swainsons hawk ( Figure 1.2). About how many miles do the hawks travel from start to finish? Are you surprised that birds migrate that far? Some species of birds migrate even farther. Whales also are known to migrate thousands of miles each year to take advantage of warmer waters in the winter months. The great migration of millions of zebra, wildebeest and other antelope in East Africa also occurs yearly. Each year around 1.5 million wildebeest and 300,000 zebra (along with other antelope) go in search of food and water, traveling a distance of around 1800 miles. Birds and other migrating animals follow the same routes each year. How do they know where to go? It depends on the species. Some animals follow landmarks, such as rivers or coastlines. Other animals are guided by the position of the sun, the usual direction of the wind, or other clues in the environment. | text | null |
L_0498 | cyclic behavior of animals | T_2878 | Many animal behaviors change at certain times of day, day after day. For example, most animals go to sleep when the sun sets and wake up when the sun rises. Animals that are active during the daytime are called diurnal. Some animals do the opposite. They sleep all day and are active during the night. These animals are called nocturnal. Examples of nocturnal animals include bats, foxes, possums, skunks and coyotes. Many mammals (including humans), insects, reptiles and birds are diurnal. Animals may eat and drink at certain times of day as well. Humans have daily cycles of behavior, too. Most people start to get sleepy after dark and have a hard time sleeping when it is light outside. Daily cycles of behavior are called circadian rhythms. In many species, including humans, circadian rhythms are controlled by a tiny structure called the biological clock. This structure is located in a gland at the base of the brain. The biological clock sends signals to the body. The signals cause regular changes in behavior and body processes. The amount of light entering the eyes helps control the biological clock. The clock causes changes that repeat every 24 hours. The migration route of Swainsons hawk starts in North America and ends in South America. Scientists learned their mi- gration route by attaching tiny tracking devices to the birds. The birds were then tracked by satellite. On the migra- tion south, the hawks travel almost 5,000 miles from start to finish. | text | null |
L_0503 | diversity of birds | T_2897 | Turkey, hummingbird, penguin, parrot, owl and eagle. These are just some of the many different types of birds. If you just think about the birds in this list, the differences are striking. About 10,000 bird species belong to 29 different orders within the class Aves. They live and breed on all seven continents. The tropics are home to the greatest biodiversity of birds. The diversity among birds is striking. Birds can vary greatly in size and color. Some fly, some swim, some just walk or run. Some are savage carnivores, others are gentle herbivores. Some are low on the food chain, others are at the top. Birds live in a variety of different habitats. Birds that live in different habitats will encounter different foods and different predators. Birds can be carnivores (feeding on other animals), herbivores (feeding on plants), or generalists (feeding on a variety of foods). The lifestyle of the bird can affect what it looks like. For example, can you think of some examples of beaks that are adapted to the type of food a bird eats? Carnivorous birds include hawks, falcons, eagles, osprey, vultures and owls. Herbivorous birds include the goose, cockatoo and parrot. The American Crow is an example of a generalist. In addition, a specialist is a bird (or other animal) that is specially adapted to eat a certain food. An example of a specialist is a hummingbird, whose long, thin beak is excellent for reaching into flowers for nectar, but not very good for eating other foods. Waterfowl are birds that live on the water. These include ducks, geese, swans, and pelicans, to name a few. Landfowl are ground-feeding birds such as chickens and turkeys. Penguins are a group of flightless birds adapted for life in the water with flippers. Diurnal raptors are birds of prey that hunt during the day. These include falcons, eagles and hawks. Nocturnal raptors hunt during the night. These include various types of owls. Parrots are brightly colored and very intelligent. They are found in the tropics and include cockatoos, parrots, and parakeets. | text | null |
L_0503 | diversity of birds | T_2898 | The size and shape of the beak is related to the food the bird eats and can vary greatly among different birds. Parrots have down-curved, hooked bills, which are well-adapted for cracking seeds and nuts ( Figure 1.1). Hummingbirds, on the other hand, have long, thin, pointed bills, which are adapted for getting the nectar out of flowers ( Figure 1.1). Hawks, eagles, falcons and owls have a sharp, hooked beak. (left) The down-curved, hooked bill of a scarlet macaw, a large colorful parrot. (right) A long, thin and pointed bill of the hummingbird. | text | null |
L_0503 | diversity of birds | T_2899 | Bird feet can also vary greatly among different birds. Some birds, such as gulls and terns and other waterfowl, have webbed feet used for swimming or floating ( Figure 1.2). Other birds, such as herons, gallinules, and rails, have four long spreading toes, which are adapted for walking delicately in the wetlands ( Figure 1.2). You can predict how the beaks and feet of birds will look depending on where they live and what type of food they eat. Flightless birds also have long legs that are adapted for running. Flightless birds include the ostrich and kiwi. Raptors have clawed feet. They also have strong legs. Hawks, eagles and falcons also have excellent vision and they hunt by sight. Owls, with excellent hearing, can hunt by that sense alone. See Wild African Vulture Birds Scavage Bones of Dead Animals at (left) The webbed feet of a great black- backed gull. (right) The long spreading toes of an American purple gallinule. Click image to the left or use the URL below. URL: | text | null |
L_0508 | ecosystems | T_2912 | Ecology is the study of ecosystems. That is, ecology is the study of how living organisms interact with each other and with the nonliving part of their environment. An ecosystem consists of all the nonliving factors and living organisms interacting in the same habitat. Recall that living organisms are biotic factors. The biotic factors of an ecosystem include all the populations in a habitat, such as all the species of plants, animals, and fungi, as well as all the micro-organisms. Also recall that the nonliving factors are called abiotic factors. Abiotic factors include temperature, water, soil, and air. You can find an ecosystem in a large body of fresh water or in a small aquarium. You can find an ecosystem in a large thriving forest or in a small piece of dead wood. Examples of ecosystems are as diverse as the rainforest, the savanna, the tundra, or the desert ( Figure 1.1). The differences in the abiotic factors, such as differences in temperature, rainfall, and soil quality, found in these areas greatly contribute to the differences seen in these ecosystems. Ecosystems can include well known sites, such as the Great Barrier Reef off the coast of Australia and the Greater Yellowstone Ecosystem of Yellowstone National Park, which actually includes a few different ecosystems, some with geothermal features, such as Old Faithful geyser. Desert Botanical Gardens in Phoenix, Ari- zona. Ecosystems need energy. Many ecosystems get their energy in the form of sunlight, which enters the ecosystem through photosynthesis. This energy then flows through the ecosystem, passed from producers to consumers. Plants are producers in many ecosystems. Energy flows from plants to the herbivores that eat the plants, and then to carnivores that eat the herbivores. The flow of energy depicts interactions of organisms within an ecosystem. Matter is also recycled in ecosystems. Biogeochemical cycles recycle nutrients, like carbon and nitrogen, so they are always available. These nutrients are used over and over again by organisms. Water is also continuously recycled. The flow of energy and the recycling of nutrients and water are examples of the interactions between organisms and the interactions between the biotic and abiotic factors of an ecosystem. | text | null |
L_0520 | fields in the life sciences | T_2934 | The life sciences are the study of living organisms. They deal with every aspect of living organisms, from the biology of cells, to the biology of individual organisms, to how these organisms interact with other organisms and their environment. The life sciences are so complex that most scientists focus on just one or two subspecialties. If you want to study insects, what would you be called? An entomologist. If you want to study the tiny things that give us the flu, then you need to enter the field of virology, the study of viruses. If you want to study the nervous system, which life science field is right for you ( Table 1.1, Table 1.2, and Table 1.3)? Field Botany Zoology Marine biology Focus Plants Animals Organisms living in oceans Field Freshwater biology Microbiology Bacteriology Virology Entomology Taxonomy Focus Organisms living in and around freshwater lakes, streams, rivers, ponds, etc. Microorganisms Bacteria Viruses Insects The classification of organisms | text | null |
L_0520 | fields in the life sciences | T_2935 | Field Cell biology Anatomy Morphology Physiology Immunology Neuroscience Developmental biology and embryology Genetics Biochemistry Molecular biology Epidemiology Evolution Focus Cells and their structures/functions Structures of animals Form and structure of living organisms Physical and chemical functions of tissues and organs Mechanisms inside organisms that protect them from disease and infection The nervous system Growth and development of plants and animals Genetic makeup of living organisms and heredity Chemistry of living organisms Nucleic acids and proteins How diseases arise and spread The changing of species over time Field Ecology Biogeography Population biology Focus How various organisms interact with their environ- ments Distribution of living organisms The biodiversity, evolution, and environmental biology of populations of organisms During the study of the life sciences, you will study cell biology, genetics, molecular biology, botany, microbi- ology, zoology, evolution, ecology, and physiology. Cell biology is the study of cellular structure and function ( Figure 1.1). Genetics is the study of heredity, which is the passing of traits (and genes) from one generation to the next. Molecular biology is the study of molecules, such as DNA and proteins. Ecologists study ecosystems, which are made of both living and nonliving parts of the environment. A botanist may work in a botanical garden, where plant life can be studied. What will you study with the other subspecialties? This illustration shows a virus among red blood cells. Which fields study red blood cells and viruses? (Keep in mind that viruses are actually much smaller than cells.) Other life science subspecialties include biogeography, which is the study of where organisms live and at what abundance. | text | null |
L_0520 | fields in the life sciences | T_2935 | Field Cell biology Anatomy Morphology Physiology Immunology Neuroscience Developmental biology and embryology Genetics Biochemistry Molecular biology Epidemiology Evolution Focus Cells and their structures/functions Structures of animals Form and structure of living organisms Physical and chemical functions of tissues and organs Mechanisms inside organisms that protect them from disease and infection The nervous system Growth and development of plants and animals Genetic makeup of living organisms and heredity Chemistry of living organisms Nucleic acids and proteins How diseases arise and spread The changing of species over time Field Ecology Biogeography Population biology Focus How various organisms interact with their environ- ments Distribution of living organisms The biodiversity, evolution, and environmental biology of populations of organisms During the study of the life sciences, you will study cell biology, genetics, molecular biology, botany, microbi- ology, zoology, evolution, ecology, and physiology. Cell biology is the study of cellular structure and function ( Figure 1.1). Genetics is the study of heredity, which is the passing of traits (and genes) from one generation to the next. Molecular biology is the study of molecules, such as DNA and proteins. Ecologists study ecosystems, which are made of both living and nonliving parts of the environment. A botanist may work in a botanical garden, where plant life can be studied. What will you study with the other subspecialties? This illustration shows a virus among red blood cells. Which fields study red blood cells and viruses? (Keep in mind that viruses are actually much smaller than cells.) Other life science subspecialties include biogeography, which is the study of where organisms live and at what abundance. | text | null |
L_0524 | food webs | T_2946 | Energy must constantly flow through an ecosystem for the system to remain stable. What exactly does this mean? Essentially, it means that organisms must eat other organisms. Food chains ( Figure 1.1) show the eating patterns in an ecosystem. Food energy flows from one organism to another. Arrows are used to show the feeding relationship between the animals. The arrow points from the organism being eaten to the organism that eats it. For example, an arrow from a plant to a grasshopper shows that the grasshopper eats the leaves. Energy and nutrients are moving from the plant to the grasshopper. Next, a bird might prey on the grasshopper, a snake may eat the bird, and then an owl might eat the snake. The food chain would be: plant grasshopper bird snake owl. A food chain cannot continue to go on and on. For example the food chain could not be: plant grasshopper spider frog lizard fox hawk. Food chains only have 4 or 5 total levels. Therefore, a chain has only 3 or 4 levels for energy transfer. This food chain includes producers and consumers. How could you add decom- posers to the food chain? In an ocean ecosystem, one possible food chain might look like this: phytoplankton krill fish shark. The producers are always at the beginning of the food chain, bringing energy into the ecosystem. Through photosynthesis, the producers create their own food in the form of glucose, but also create the food for the other organisms in the ecosystem. The herbivores come next, then the carnivores. When these consumers eat other organisms, they use the glucose in those organisms for energy. In this example, phytoplankton are eaten by krill, which are tiny, shrimp-like animals. The krill are eaten by fish, which are then eaten by sharks. Could decomposers be added to a food chain? Each organism can eat and be eaten by many different types of organisms, so simple food chains are rare in nature. There are also many different species of fish and sharks. So a food chain cannot end with a shark; it must end with a distinct species of shark. A food chain does not contain the general category of "fish," it will contain specific species of fish. In ecosystems, there are many food chains. Since feeding relationships are so complicated, we can combine food chains together to create a more accurate flow of energy within an ecosystem. A food web ( Figure 1.2) shows the feeding relationships between many organisms in an ecosystem. If you expand our original example of a food chain, you could add deer that eat clover and foxes that hunt chipmunks. A food web shows many more arrows, but still shows the flow of energy. A complete food web may show hundreds of different feeding relationships. For more information on food chains, see A Million Sharks at . | text | null |
L_0526 | frogs and toads | T_2949 | Frogs and toads are amphibians in the order Anura. In terms of classification, there is actually not a big difference between frogs and toads. Frogs often have long legs that are good for hopping, skin that is smooth and moist, and special pads on their toes that help them climb. Toads are more heavyset with shorter legs, and usually have drier skin, often with warty-looking bumps. Frogs are more likely to live in or near water than toads. Frogs are found in many areas of the world, from the tropics to subarctic regions, but most species are found in tropical rainforests. Consisting of more than 5,000 species (about 88% of amphibian species are frogs), they are among the most diverse groups of vertebrates. Frogs range in size from less than 0.5 inches in species in Brazil and Cuba to the over 1-foot (33 cm) long goliath frog of Cameroon, which can weigh up to 7 pounds. That is 1-foot from the nose to the back of the body, not including the length of the legs. Even the largest frogs are significantly smaller than common reptiles. | text | null |
L_0526 | frogs and toads | T_2950 | Adult frogs are characterized by long hind legs, a short body, webbed finger-like parts, and the lack of a tail. They also have a three-chambered heart, as do all tetrapods except birds and mammals. Most frogs live part of the time in water and part of the time on land. They move easily on land by jumping or climbing. To become great jumpers, frogs evolved long hind legs and long ankle bones. They also have a short backbone with only ten vertebrae. Frog and toad skin hangs loosely on the body, and skin texture can be smooth, warty, or folded. Frogs and toads dont have fur, feathers, or scales on their skin. Instead, they have a moist and permeable skin layer covered with mucous glands. Their special skin allows them to breathe through their skin in addition to using their lungs. They are vulnerable to water loss through the skin in dry conditions, which is why they need to live near water or in moist environments. The thin layer of mucous keeps the skin moist. In order to live on land and in water, frogs have three eyelid membranes: one is see-through to protect the eyes underwater, and the two other ones let them see on land. Frogs also have a tympanum, which acts like a simple ear. They are found on each side of the head. In some species, the tympanum is covered by skin. A tree frog. Notice the powerful muscles in the limbs and the coverings around the eyes. | text | null |
L_0526 | frogs and toads | T_2951 | Frogs typically lay their eggs in puddles, ponds, or lakes. Their larvae, or tadpoles, have gills, a tail, but no legs, and need to live in water. If fact, they are quite similar to a fish. Tadpoles develop into adult frogs in water ( Figure You may hear males "ribbiting," producing a mating call used to attract females to the bodies of water best for mating and breeding. Frog calls can occur during the day or night. Each frog species has a different call that is used to attract mates and warn off rivals. When a female picks a male whose call she likes, the male grabs her and squeezes across her back and around her abdomen. This causes the female to release her eggs. The male then fertilizes the eggs and, in some species, also guards them. | text | null |
L_0526 | frogs and toads | T_2952 | Adult frogs are meat-eaters and eat mostly insects, spiders, slugs and worms. Larger species will eat mice, birds, and even other small reptiles and amphibians. Frogs do not have teeth on their lower jaw, so they usually swallow their food whole. Some frogs have teeth on the upper jaw that are used to hold the prey in place. Frogs and toads are responsible for keeping a large part of the worlds insect population under control. They catch these insects using their long tongue. The frog tongue is about a third the length of the frogs body, though they can Frogs develop from tadpoles, which de- velop from eggs. Notice the formation of the two powerful back legs used for jumping. grow even longer. They can easily reach 12 inches long in an adult frog. Frogs tongues are attached to the front of their mouths rather than at the back like humans. They release a sticky substance at the precise moment of impact with their food. When a frog catches an insect it throws its sticky tongue out of its mouth and wraps it around its prey. The frogs tongue then snaps back and throws the food down its throat. This happens about as fast as a blink of your eyes. | text | null |
L_0527 | fungi | T_2953 | Ever notice blue-green mold growing on a loaf of bread? Do you like your pizza with mushrooms? Has a physician ever prescribed an antibiotic for you? If so, then you have encountered fungi. Fungi are organisms that belong to the Kingdom Fungi ( Figure 1.1). Our environment needs fungi. Fungi help decompose matter to release nutrients and make nutritious food for other organisms. Fungi are all around us and are useful in many ways. These many different kinds of organisms demonstrate the huge diversity within the Kingdom Fungi. | text | null |
L_0527 | fungi | T_2954 | If you had to guess, would you say a fungus is a plant or an animal? Scientists used to debate about which kingdom to place fungi in. Finally they decided that fungi were plants. But they were wrong. Now, scientists know that fungi are not plants at all. Fungi are very different from plants. The main difference between plants and fungi is how they obtain energy. Plants are autotrophs, meaning that they make their own "food" using the energy from sunlight. Fungi are heterotrophs, which means that they obtain their "food" from outside of themselves. In other words, they must "eat" their food like animals do. But they dont really eat. Instead, they absorb their nutrients. Yeasts, molds, and mushrooms are all different kinds of fungi. There may be as many as 1.5 million species of fungi ( Figure 1.2). You can easily see bread mold and mushrooms without a microscope, but most fungi you cannot see. Fungi are either too small to be seen without a microscope, or they live where you cannot see them easilydeep in the soil, under decaying logs, or inside plants or animals. Some fungi even live in, or on top of, other fungi. | text | null |
L_0527 | fungi | T_2955 | Fungi can grow fast because they are such good eaters. Fungi have lots of surface area, and this large surface area eats or absorbs. Surface area is how much exposed area an organism has, compared to their overall volume. Most of a mushrooms surface area is actually underground. If you see a mushroom in your yard, that is just a small part of a larger fungus growing underground. These are the steps involved in fungi "eating": 1. Fungi squirt special enzymes into their environment. 2. The enzymes help digest large organic molecules, similar to cutting up your food before you eat. 3. Cells of the fungi then absorb the broken-down nutrients. | text | null |
L_0528 | fungi classification | T_2956 | Scientists used to think that fungi were members of the plant kingdom. They thought this because fungi had several similarities to plants. For example: Fungi and plants have similar structures. Plants and fungi live in the same kinds of habitats, such as growing in soil. Plants and fungi cells both have a cell wall, which animals do not have. | text | null |
L_0528 | fungi classification | T_2957 | However, there are a number of characteristics that make fungi different from plants: 1. Fungi cannot make their own food like plants can, since they do not have chloroplasts and cannot carry out photosynthesis. Fungi are more like animals because they are heterotrophs, as opposed to autotrophs, like plants, that make their own food. Fungi have to obtain their food, nutrients and glucose, from outside sources. 2. The cell walls in many species of fungi contain chitin. Chitin is tough carbohydrate found in the shells of animals such as beetles and lobsters. The cell wall of a plant is made of cellulose, not chitin. 3. Unlike many plants, most fungi do not have structures, such as xylem and phloem, that transfer water and nutrients. | text | null |
L_0528 | fungi classification | T_2958 | The Kingdom Fungi can be broken down into several phyla. Each phyla has some unique traits. And even within the same phyla there are many differences among the fungi. Various types of fungi are pictured below ( Table 1.1). Notice how different each of these organisms are from one another. Type of Fungi Molds Examples Penicillium Mushrooms Morels, shiitake, cremini, oyster Single-celled yeasts Bakers yeast | text | null |
L_0529 | fungi reproduction | T_2959 | Different fungi reproduce in different ways. Many fungi reproduce both sexually and asexually. However, some reproduce only sexually and some only asexually. Asexual reproduction involves just one parent and sexual repro- duction involves two parents. | text | null |
L_0529 | fungi reproduction | T_2960 | Through asexual reproduction, new organisms are produced that are genetically identical to the parent. That is, they have exactly the same DNA. Fungi reproduce asexually through three methods: 1. Spores: Spores are formed by the fungi and released to create new fungi. This is the powdery substance released by puffballs. Spores are haploid reproductive cells found in some bacteria, plants, algae, fungi, and protozoa. Theoretically, spores can reproduce asexually to produce countless offspring. Obviously this does not happen. If it did, the world would be covered by genetically identical fungi. 2. Budding: The fungus grows a new part of its body, which eventually breaks off. The broken-off piece becomes a new organism ( Figure 1.1). 3. Fragmentation: In this method, a piece of the mycelium, the body of the fungus, splits off. The resulting fragment can eventually produce a new colony of fungi. Asexual reproduction is faster and produces more fungi than sexual reproduction. This form of reproduction is controlled by many different factors. Outside conditions, such as the availability of food, determine when a fungus undergoes asexual reproduction. | text | null |
L_0529 | fungi reproduction | T_2961 | Almost all fungi can reproduce sexually. But why reproduce sexually when asexual reproduction is much quicker? Sexual reproduction brings together traits from the two parents. This increases the genetic diversity of the species. In plants and animals, sexual reproduction occurs when sperm and egg from two parents join to make a new individual. In fungi, however, two haploid hyphae meet together and their nuclei fuse. Instead of calling a hyphae male or female, they have different mating types, such as (+) and (-) ( Figure 1.2). The common mushroom, a fruiting body, results after sexual reproduction when two hyphae, one (+) and one (-), mate, forming a mycelium with sporangia. No- tice, when the sporangia burst, the spores are released from the fruiting body. | text | null |
L_0534 | gymnosperms | T_2971 | Gymnosperms have seeds, but they do not produce fruit. Instead, the seeds of gymnosperms are usually found in cones. There are four phyla of gymnosperms: 1. Conifers 2. Cycads 3. Ginkgoes 4. Gnetophytes | text | null |
L_0534 | gymnosperms | T_2972 | Conifers, members of the phylum Coniferophyta, are probably the gymnosperms that are most familiar to you. Conifers include trees such as pines, firs, spruces, cedars, and the coastal redwood trees in California, which are the tallest living vascular plants. Conifers have their reproductive structures in cones, but they are not the only plants to have that trait ( Figure 1.1). Conifer pollen cones are usually very small, while the seed cones are larger. Pollen contains gametophytes that produce the male gamete of seed plants. The pollen, which is a powder-like substance, is carried by the wind to fertilize the seed cones that contain the female gamete ( Figure 1.2). Conifers have many uses. They are important sources of lumber and are also used to make paper. Resins, the sticky substance you might see oozing out of a wound on a pine tree, are collected from conifers to make a variety of products, such as the solvent turpentine and the rosin used by musicians and baseball players. The sticky rosin improves the pitchers hold on the ball or increases the friction between the bow and the strings to help create music from a violin or other stringed instrument. | text | null |
L_0534 | gymnosperms | T_2973 | Cycads, in the phylum Cycadophyta, are also gymnosperms. They have large, finely-divided leaves and grow as short shrubs and trees in tropical regions. Like conifers, they produce cones, but the seed cones and pollen cones are always on separate plants ( Figure 1.3). One type of cycad, the Sago Palm, is a popular landscape plant. During the Age of the Dinosaurs (about 65 to 200 million years ago), cycads were the dominant plants. So you can imagine dinosaurs grazing on cycad seeds and roaming through cycad forests. The end of a pine tree branch bears the male cones that produce the pollen. Cycads bear their pollen and seeds in cones on separate plants. | text | null |
L_0534 | gymnosperms | T_2973 | Cycads, in the phylum Cycadophyta, are also gymnosperms. They have large, finely-divided leaves and grow as short shrubs and trees in tropical regions. Like conifers, they produce cones, but the seed cones and pollen cones are always on separate plants ( Figure 1.3). One type of cycad, the Sago Palm, is a popular landscape plant. During the Age of the Dinosaurs (about 65 to 200 million years ago), cycads were the dominant plants. So you can imagine dinosaurs grazing on cycad seeds and roaming through cycad forests. The end of a pine tree branch bears the male cones that produce the pollen. Cycads bear their pollen and seeds in cones on separate plants. | text | null |
L_0534 | gymnosperms | T_2974 | Ginkgoes, in the phylum Ginkgophyta, are unique because they are the only species left in the phylum. Many other species in the fossil record have gone extinct ( Figure 1.4). The ginkgo tree is sometimes called a "living fossil" because it is the last species from its phylum. One reason the ginkgo tree may have survived is because it was often grown around Buddhist temples, especially in China. The ginkgo tree is also a popular landscape tree today in American cities because it can live in polluted areas better than most plants. Ginkgoes, like cycads, has separate female and male plants. The male trees are usually preferred for landscaping because the seeds produced by the female plants smell terrible when they ripen. Ginkgo trees are gymnosperms with broad leaves. | text | null |
L_0534 | gymnosperms | T_2975 | Gnetophytes, in the phylum Gnetophyta, are a very small and unusual group of plants. Ephedra is an important member of this group, since this desert shrub produces the ephedrine used to treat asthma and other conditions. Welwitschia produces extremely long leaves and is found in the deserts of southwestern Africa ( Figure 1.5). Overall, there are about 70 different species in this diverse phylum. One type of gnetophyte is Welwitschia. | text | null |
L_0535 | habitat and niche | T_2977 | Each organism plays a particular role in its ecosystem. A niche is the role a species plays in the ecosystem. In other words, a niche is how an organism makes a living. A niche will include the organisms role in the flow of energy through the ecosystem. This involves how the organism gets its energy, which usually has to do with what an organism eats, and how the organism passes that energy through the ecosystem, which has to do with what eats the organism. An organisms niche also includes how the organism interacts with other organisms, and its role in recycling nutrients. Once a niche is left vacant, other organisms can fill that position. For example when the Tarpan, a small wild horse found mainly in southern Russia, became extinct in the early 1900s, its niche was filled by a small horse breed, the Konik ( Figure 1.1). Often this occurs as a new species evolves to occupy the vacant niche. A species niche must be specific to that species; no two species can fill the same niche. They can have very similar niches, which can overlap, but there must be distinct differences between any two niches. If two species do fill the same niche, they will compete for all necessary resources. One species will out compete the other, forcing the other species to adapt or risk extinction. This is known as competitive exclusion. When plants and animals are introduced, either intentionally or by accident, into a new environment, they can occupy the existing niches of native organisms. Sometimes new species out-compete native species, and the native species may go extinct. They can then become a serious pest. For example, kudzu, a Japanese vine, was planted in the southeastern United States in the 1870s to help control soil loss. Kudzu had no natural predators, so it was able to out-compete native species of vine and take over their niches ( Figure 1.2). | text | null |
L_0535 | habitat and niche | T_2978 | The habitat is the physical area where a species lives. Many factors are used to describe a habitat. The average amount of sunlight received each day, the range of annual temperatures, and average yearly rainfall can all describe a habitat. These and other abiotic factors will affect the kind of traits an organism must have in order to survive there. The temperature, the amount of rainfall, the type of soil and other abiotic factors all have a significant role in determining the plants that invade an area. The plants then determine the animals that come to eat the plants, and so on. A habitat should not be confused with an ecosystem: the habitat is the actual place of the ecosystem, whereas the ecosystem includes both the biotic and abiotic factors in the habitat. Habitat destruction means what it sounds likean organisms habitat is destroyed. Habitat destruction can cause a population to decrease. If bad enough, it can also cause species to go extinct. Clearing large areas of land for housing developments or businesses can cause habitat destruction. Poor fire management, pest and weed invasion, and storm damage can also destroy habitats. National parks, nature reserves, and other protected areas all preserve habitats. Santa Cruz Island off the California coast has diverse habitats including a coastline with steep cliffs, coves, gigantic caves, and sandy beaches. | text | null |
L_0535 | habitat and niche | T_2978 | The habitat is the physical area where a species lives. Many factors are used to describe a habitat. The average amount of sunlight received each day, the range of annual temperatures, and average yearly rainfall can all describe a habitat. These and other abiotic factors will affect the kind of traits an organism must have in order to survive there. The temperature, the amount of rainfall, the type of soil and other abiotic factors all have a significant role in determining the plants that invade an area. The plants then determine the animals that come to eat the plants, and so on. A habitat should not be confused with an ecosystem: the habitat is the actual place of the ecosystem, whereas the ecosystem includes both the biotic and abiotic factors in the habitat. Habitat destruction means what it sounds likean organisms habitat is destroyed. Habitat destruction can cause a population to decrease. If bad enough, it can also cause species to go extinct. Clearing large areas of land for housing developments or businesses can cause habitat destruction. Poor fire management, pest and weed invasion, and storm damage can also destroy habitats. National parks, nature reserves, and other protected areas all preserve habitats. Santa Cruz Island off the California coast has diverse habitats including a coastline with steep cliffs, coves, gigantic caves, and sandy beaches. | text | null |
L_0536 | habitat destruction | T_2979 | From a human point of view, a habitat is where you live, go to school, and go to have fun. Your habitat can be altered, and you can easily adapt. Most people live in a few different places and go to a number of different schools throughout their life. But a plant or animal may not be able to adapt to a changed habitat. A habitat is the natural home or environment of an organism. Humans often destroy the habitats of other organisms. Habitat destruction can cause the extinction of species. Extinction is the complete disappearance of a species. Once a species is extinct, it can never recover. Some ways humans cause habitat destruction are by clearing land and by introducing non-native species of plants and animals. | text | null |
L_0536 | habitat destruction | T_2980 | Clearing land for agriculture and development is a major cause of habitat destruction. Within the past 100 years, the amount of total land used for agriculture has almost doubled. Land used for grazing cattle has more than doubled. Agriculture alone has cost the United States half of its wetlands ( Figure 1.1) and almost all of its tallgrass prairies. Native prairie ecosystems, with their thick fertile soils, deep-rooted grasses, diversity of colorful flowers, burrowing prairie dogs, and herds of bison and other animals, have virtually disappeared ( Figure 1.3). Wetlands such as this one in Cape May, New Jersey, filter water and protect coastal lands from storms and floods. The Flint Hills contain some of the largest remnants of tallgrass prairie habitat remaining in North America. | text | null |
L_0536 | habitat destruction | T_2980 | Clearing land for agriculture and development is a major cause of habitat destruction. Within the past 100 years, the amount of total land used for agriculture has almost doubled. Land used for grazing cattle has more than doubled. Agriculture alone has cost the United States half of its wetlands ( Figure 1.1) and almost all of its tallgrass prairies. Native prairie ecosystems, with their thick fertile soils, deep-rooted grasses, diversity of colorful flowers, burrowing prairie dogs, and herds of bison and other animals, have virtually disappeared ( Figure 1.3). Wetlands such as this one in Cape May, New Jersey, filter water and protect coastal lands from storms and floods. The Flint Hills contain some of the largest remnants of tallgrass prairie habitat remaining in North America. | text | null |
L_0536 | habitat destruction | T_2981 | Other habitats that are being rapidly destroyed are forests, especially tropical rainforests. The largest cause of deforestation today is slash-and-burn agriculture (shown in the opening image). This means that when people want to turn a forest into a farm, they cut down all of the trees and then burn the remainder of the forest. This technique is used by over 200 million people in tropical forests throughout the world. As a consequence of slash-and-burn agriculture, nutrients are quickly lost from the soil. This often results in people abandoning the land within a few years. Then the top soil erodes and desertification can follow. Desertification Herds of bison also made up part of the tallgrass prairie community. turns forest into a desert, where it is difficult for plants to grow. Half of the Earths mature tropical forests are gone. At current rates of deforestation, all tropical forests will be gone by the year 2090. | text | null |
L_0536 | habitat destruction | T_2982 | One of the main causes of extinction is introduction of exotic species into an environment. These exotic and new species can also be called invasive species or non-native species. These non-native species, being new to an area, may not have natural predators in the new habitat, which allows their populations to easily adapt and grow. Invasive species out-compete the native species for resources. Sometimes invasive species are so successful at living in a certain habitat that the native species go extinct ( Figure 1.4). Recently, cargo ships have transported zebra mussels, spiny waterfleas, and ruffe (a freshwater fish) into the Great Lakes ( Figure 1.5). These invasive species are better at hunting for food. They have caused some of the native species to go extinct. Invasive species can disrupt food chains, carry disease, prey on native species directly, and out-compete native species for limited resources, like food. All of these effects can lead to extinction of the native species. | text | null |
L_0536 | habitat destruction | T_2983 | Other causes of habitat destruction include poor fire management, overfishing, mining ( Figure 1.6), pollution, and storm damage. All of these can cause irreversible changes to a habitat and ecosystem. | text | null |
L_0536 | habitat destruction | T_2984 | A habitat that is quickly being destroyed is the wetland. By the 1980s, over 80% of all wetlands in parts of the U.S. were destroyed. In Europe, many wetland species have gone extinct. For example, many bogs in Scotland have been lost because of human development. Another example of species loss due to habitat destruction happened on Madagascars central highland plateau. From 1970 to 2000, slash-and-burn agriculture destroyed about 10% of the countrys total native plants. The area turned into a wasteland. Soil from erosion entered the waterways. Much of the river ecosystems of several large rivers were also destroyed. Several fish species are almost extinct. Also, some coral reef formations in the Indian Ocean are completely lost. | text | null |
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