lessonID
stringlengths 6
6
| lessonName
stringlengths 3
52
| ID
stringlengths 6
21
| content
stringlengths 10
6.57k
| media_type
stringclasses 2
values | path
stringlengths 28
76
⌀ |
|---|---|---|---|---|---|
L_0373 | echinoderms and invertebrate chordates | T_2023 | Chordates have three embryonic cell layers: endoderm, mesoderm, and ectoderm. They also have a segmented body with a complete coelom and bilateral symmetry. In addition, chordates have a complete digestive system, central nervous system, and circulatory system. | text | null |
L_0373 | echinoderms and invertebrate chordates | T_2024 | There are four traits that are unique to chordates and define Phylum Chordata. The four traits are a post-anal tail, dorsal hollow nerve cord, notochord, and pharyngeal slits. You can see the four traits in Figure 12.30. 1. The post-anal tail is at the end of the organism opposite the head. It extends beyond the anus. 2. The hollow nerve cord runs along the top (dorsal) side of the animal. (In nonchordate animals, the nerve cord is solid and runs along the bottom side.) 3. The notochord lies between the dorsal nerve cord and the digestive tract. It provides stiffness to counterbalance the pull of muscles. 4. The pharyngeal slits are located in the pharynx. The pharynx is the tube that joins the mouth to the digestive and respiratory tracts. In some chordates, all four of these defining traits last throughout life and have important functions. For example, in some chordates, pharyngeal slits are used to filter food out of water. In many chordates, however, including humans, all four traits are present only in the embryo. After that, some of the traits disappear or develop into other structures. For example, in humans, pharyngeal slits are present in the embryo but later develop into parts of the ear. | text | null |
L_0373 | echinoderms and invertebrate chordates | T_2025 | Living chordates are mainly vertebrates. In vertebrates, the notochord develops into a backbone, or vertebral column, after the embryonic stage. A small percentage of chordates are invertebrates. Their notochord never develops into a backbone. Invertebrate chordates include tunicates and lancelets. Both groups of animals are small and relatively primitive. They are probably similar to the earliest chordates that evolved more than 500 million years ago. | text | null |
L_0373 | echinoderms and invertebrate chordates | T_2026 | Tunicates are invertebrate chordates that lose some of the four defining chordate traits by adulthood. Tunicates are also called sea squirts. There are about 3000 living species of tunicates. All are ocean dwellers and live in shallow water. You can see examples of tunicates in Figure 12.31. As larvae, tunicates can swim freely to find food. As adults, tunicates lack a post-anal tail and notochord, and they can no longer swim. Instead, they remain in one place and are filter feeders. Tunicates can reproduce both sexually and asexually. The same adults produce sperm and eggs. However, fertilization always involves gametes from different parents. Asexual reproduction is by budding. | text | null |
L_0373 | echinoderms and invertebrate chordates | T_2027 | Lancelets are invertebrate chordates that retain all four defining chordate traits as adults. There are only about 25 species of living lancelets. Lancelets resemble tunicates in several ways. For example: lancelets live in shallow ocean water; lancelet larvae can swim to find food; and lancelet adults are filter feeders that can no longer swim. Adult lancelets spend most of their time buried in sand on the ocean floor. Lancelets reproduce sexually, with separate sexes producing sperm and eggs. | text | null |
L_0376 | amphibians | T_2047 | Amphibians are vertebrates that live part of the time in fresh water and part of the time on land. They were the first vertebrates to evolve four legs and colonize the land. They most likely evolved from lobe-finned fish. Modern amphibians include frogs, toads, salamanders, newts, and caecilians. They are ectotherms, so they have little control over their body temperature. This allows them to be active in warm weather, but they become sluggish when the temperature cools. | text | null |
L_0376 | amphibians | T_2048 | Amphibians have moist skin without scales. The skin is kept moist by mucus, which is secreted by mucous glands. In some species, the mucous glands also secrete toxins that make the animal poisonous to predators. The blue poison-dart frogs in Figure 13.12 are a good example. The toxin in their mucus is used by native people in South America to poison the tips of their hunting arrows. Amphibian skin contains keratin, a protein that is also found in the outer covering of most other four-legged vertebrates. The keratin in amphibians is not too tough to allow gases and water to pass through their skin. Most amphibians breathe with gills as larvae and with lungs as adults. However, extra oxygen is absorbed through the skin. | text | null |
L_0376 | amphibians | T_2049 | All amphibians have digestive, excretory, and reproductive systems. All three of these organ systems use a single body cavity, called the cloaca. Wastes enter the cloaca from the digestive and excretory systems. Gametes enter the cloaca from the reproductive system. A single external opening in the cloaca allows the wastes and gametes to exit the body. (Many other four legged vertebrates also have a cloaca.) Amphibians have relatively complex circulatory and nervous systems. They have sensory organs for smelling and tasting, as well as eyes and ears. Frogs also have a larynx, or voice box, that allows them to make sounds. The purpose of frog calls varies. Some calls are used to attract mates, some are used to scare off other frogs, and some are signals of distress.You can hear a collection of frog calls at this link: http://animaldiversity.ummz.umich.edu/co | text | null |
L_0376 | amphibians | T_2050 | Amphibians reproduce sexually. Fertilization may take place inside or outside the body. Amphibians are oviparous. Embryos develop in eggs outside the mothers body. | text | null |
L_0376 | amphibians | T_2051 | Amphibians do not produce amniotic eggs with waterproof membranes. Therefore, they must lay their eggs in water. The eggs are usually covered with a jelly-like substance that helps keep them moist and offers some projection from predators. You can see a mass of frog eggs in jelly in Figure 13.13. Amphibians generally lay large numbers of eggs. Often, many adults lay eggs in the same place at the same time. This helps ensure that the eggs will be fertilized. Once eggs are laid, amphibian parents typically provide no parental care. | text | null |
L_0376 | amphibians | T_2052 | Most amphibians go through a larval stage that is different from the adult form. In frogs, for example, the early larval stage resembles a fish, as you can see in Figure 13.14. Frogs at this stage of development are called tadpoles. Tadpoles live in the water. They lack legs and have a long tail that helps them swim. They also have gills, which absorb oxygen from the water. During metamorphosis, the tadpole changes to the form of an adult frog. It grows legs, loses its tail, and develops lungs. All of these changes prepare it to live on the land. In Figure 13.15, you can see how a frog larva looks as it changes to the adult form. | text | null |
L_0376 | amphibians | T_2052 | Most amphibians go through a larval stage that is different from the adult form. In frogs, for example, the early larval stage resembles a fish, as you can see in Figure 13.14. Frogs at this stage of development are called tadpoles. Tadpoles live in the water. They lack legs and have a long tail that helps them swim. They also have gills, which absorb oxygen from the water. During metamorphosis, the tadpole changes to the form of an adult frog. It grows legs, loses its tail, and develops lungs. All of these changes prepare it to live on the land. In Figure 13.15, you can see how a frog larva looks as it changes to the adult form. | text | null |
L_0376 | amphibians | T_2053 | There are only about 6200 known species of amphibians. They are placed in three orders: frogs, salamanders, and caecilians. Table 13.4 shows a picture of an amphibian in each order. It also provides additional information about the orders. Class Frogs Distinguishing Traits The frog order also includes toads. Unlike other amphibians, frogs and toads lack a tail by adulthood. Their back legs are also longer because they are specialized for jumping. Frogs can jump as far as 20 times their body length. Thats like you jumping more than the length of a basketball court! Example red-eyed tree frog Class Salamanders Caecilians Distinguishing Traits The salamander order also includes newts. Salamanders and newts keep their tails as adults. They have a long body with short legs. They are adapted for walking and swim- ming rather than jumping. Unlike other vertebrates, salamanders can regrow legs or other body parts if they are bitten off by a predator. The caecilian order is the amphib- ian order with the fewest species. Caecilians are closely related to salamanders. They have a long, worm-like body. They are the only amphibians without legs. Caecil- ians evolved from a four-legged an- cestor but lost their legs later in their evolution. As adults, they often bur- row into the soil. Thats one reason why Caecilians tend to be less well known than other amphibians. Example smooth newt microcaecilia | text | null |
L_0376 | amphibians | T_2054 | Amphibians live in freshwater and moist-soil habitats throughout the world. The only continent that lacks amphib- ians is Antarctica. Amphibians are especially common in temperate lakes and ponds and in tropical rainforests. | text | null |
L_0376 | amphibians | T_2055 | Amphibians are the prey of many other vertebrates, including birds, snakes, raccoons, and fish. Amphibians are also important predators. As larvae, they may eat water insects and algae. As adults, they typically eat invertebrates, including worms, snails, and insects. You can watch a frog catching an invertebrate in the slow-motion video at the following link. At its real speed, you would barely see it because it happens so quickly. MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0376 | amphibians | T_2056 | Why are so many amphibian species threatened by extinction, and why should you care? The second question is easy. Amphibians control pests, may be a source of new medicines, and help feed many other animals. The nature of amphibian skin may help explain why so many amphibian species are at risk. Their skin easily absorbs substances from the environment, such as pollutants in water or air. Therefore, they may suffer from poor environmental quality before other animals do. As such, they may provide an early-warning system of environmental damage. What can you do to help save amphibians? Protect the natural environment. For example, reduce your use of energy to curb greenhouse gases and global warming. Avoid the use of garden pesticides. Poisoned insects may be eaten by amphibians that are also harmed by the poison. Make a backyard habitat. A small pond surrounded by native vegetation provides a place for amphibians to live. Help raise awareness. Start a letter-writing campaign to politicians, asking them to support conservation activities for amphibians. For more ideas about what you can do to help save amphibians, check out this website: | text | null |
L_0377 | reptiles | T_2057 | Reptiles are ectothermic, four-legged vertebrates that produce amniotic eggs. The reptile class is one of the largest classes of vertebrates. Besides turtles, it includes crocodiles, alligators, lizards, and snakes. Although some turtles and other reptiles now live mainly in the water, reptiles evolved many adaptations for life on land. For an amusing overview of reptiles, watch this Bill Nye the Science Guy reptile video: MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0377 | reptiles | T_2058 | Reptiles were the first vertebrates to lay amniotic eggs. This freed them from returning to the water to reproduce. In addition to amniotic eggs, reptiles have several other adaptations for living on land. For example, reptile skin is covered with scales. You can see how the scales overlap and cover the snake in Figure 13.17. Reptile scales are made of very tough keratin. They help protect reptiles from injury as well as loss of water. Because of their tough scales, reptiles cant absorb oxygen through their skin as amphibians can. However, reptiles have more efficient lungs for breathing air. They also have various ways of moving air into and out of their lungs. For example, their chest muscles contract to push air out of the lungs. The muscles relax to allow air to rush into the lungs. Another muscle, called the diaphragm, which lies below the lungs, also helps move air into and out of the lungs. (Mammals also have a diaphragm for breathing air.) | text | null |
L_0377 | reptiles | T_2059 | Reptiles have a circulatory system with a heart that pumps blood. Reptiles also have a centralized nervous system with a brain. Their brain is relatively small, but the parts of the brain that control the senses and learning are larger than in amphibians. Reptiles have good senses of sight and smell. They use their tongue to smell scents. Thats what the blue-tongued lizard in Figure 13.18 is doing. Some reptiles also have a heat-sensing organ that helps them locate the warm bodies of prey animals such as birds and small mammals. | text | null |
L_0377 | reptiles | T_2059 | Reptiles have a circulatory system with a heart that pumps blood. Reptiles also have a centralized nervous system with a brain. Their brain is relatively small, but the parts of the brain that control the senses and learning are larger than in amphibians. Reptiles have good senses of sight and smell. They use their tongue to smell scents. Thats what the blue-tongued lizard in Figure 13.18 is doing. Some reptiles also have a heat-sensing organ that helps them locate the warm bodies of prey animals such as birds and small mammals. | text | null |
L_0377 | reptiles | T_2060 | Most reptiles have sexual reproduction with internal fertilization. Reptiles have a body cavity called a cloaca that is involved in reproduction. Sperm or eggs are released into an adult reptiles cloaca. Males have one or two penises that pass sperm from their cloaca to the eggs in the cloaca of a female, where fertilization takes place. In most reptile species, once fertilized the eggs leave the body through an opening in the cloaca. These reptiles are oviparous. Eggs develop and hatch outside the mothers body. Young reptiles, like the baby alligator in Figure 13.19, look like smaller versions of the adults. They dont have a larval stage as most amphibians do. Baby reptiles are able to move and search for food but are at high risk of predation. Adult reptiles rarely provide any care for their offspring once the eggs are laid. The only exceptions are female alligators and crocodiles. They defend their eggs and hatchlings from predators and help them reach the water. | text | null |
L_0377 | reptiles | T_2061 | There are over 8200 living species of reptiles. They are classified in four orders, called Crocodilia, Sphenodontia, Squamata, and Testudines. Table 13.4 shows a picture of a reptile in each order. It also provides additional information about the orders. For an online gallery of amazing photos of reptiles, go to this link: http://video MEDIA Click image to the left or use the URL below. URL: Class Crocodilia Distinguishing Traits Reptiles in the Crocodilia Order are called crocodilians. They include crocodiles, alligators, caimans, and gharils. They have four sprawling legs that allow them to run surpris- ingly fast. They have strong jaws and replace their teeth throughout life. Crocodilians have relatively complex brains and greater intelli- gence than other reptiles. Example crocodile Class Sphenodontia Distinguishing Traits The Sphenodontia Order includes only tuataras like the one in this photo. They resemble lizards but are the least specialized of all living reptiles. Their brain is similar to the amphibian brain. Example tuatara Squamata The Squamata order includes lizards and snakes. Lizards have four legs for running or climbing, and they can also swim. Many change their color when threatened. Snakes do not have legs, although they evolved from a four-legged ancestor. They have a very flexible jaw for swallowing large prey whole. Some inject poison into their prey through fangs. The Testudines Order includes tur- tles, tortoises, and terrapins. They have four legs for walking. They have a hard shell covering most of their body. lizard Testudines terrapin | text | null |
L_0377 | reptiles | T_2062 | Modern reptiles live in many different habitats. They can be found on every continent except Antarctica. | text | null |
L_0377 | reptiles | T_2063 | Many turtles are aquatic. They may live in the ocean or in fresh water. Other turtles are terrestrial and live on land. All lizards are terrestrial. Their habitats may range from deserts to rainforests. They may live in a range of places, from underground burrows to the tops of trees. Most snakes are terrestrial, but some are aquatic. Crocodilians live in and around swamps or bodies of water. The water may be fresh or salty, depending on the species of crocodilian. | text | null |
L_0377 | reptiles | T_2064 | All reptiles are heterotrophs, and the majority eats other animals. Heterotrophs that eat only or mainly animals are called carnivores. Large carnivorous reptiles such as crocodilians are the top predators in their ecosystems. They prey on large birds, fish, deer, turtles, and sometimes farm livestock. Their powerful jaws are strong enough to crush bones and turtle shells. Smaller carnivorous reptilesincluding tuataras, snakes, and many lizardsare lower-level predators. They prey on small animals such as insects, frogs, birds, and mice. Most terrestrial turtles eat plants. Heterotrophs that eat only or mainly plants are called herbivores. Herbivorous turtles graze on grasses, leaves, flowers, and fruits. Marine turtles and some lizards feed on both plants and animals. Heterotrophs that eat a variety of foods including both plants and animals are called omnivores. | text | null |
L_0378 | birds | T_2065 | Birds are four-limbed, endothermic vertebrates. The upper pair of limbs are wings that most birds use for flying. The lower pair of limbs are legs with feet that birds use for walking. Because birds walk on two legs, they are called bipedal. (Humans are bipedal too.) Birds also have feathers and beaks, and they produce amniotic eggs. Of all vertebrate classes, birds are the most numerous, even though they evolved most recently. Why have birds been so successful? The answer is flight. Being able to fly opened up a whole new world to birds: the world of the air above the land and water. Other than insects, virtually no other animals can inhabit the airy world. Flying is a sure-fire way to escape from all but the quickest nonflying predators. Flying also gives birds a good view for finding food and mates. | text | null |
L_0378 | birds | T_2066 | Wings and feathers are two adaptations for flight that evolved in birds. Both are clearly displayed in the flying gull in Figure 14.2. Wings evolved from the front limbs of a four-legged ancestor. The wings are controlled by large flight muscles in the chest. Feathers also help birds fly. They provide air resistance and lift. In addition, they provide insulation and serve other roles. | text | null |
L_0378 | birds | T_2067 | To keep their flight muscles well supplied with oxygen, birds evolved specialized respiratory and circulatory systems. Birds have special air sacs for storing extra air and pumping it into the lungs. They also have a relatively large heart and a rapid heart rate. These adaptations keep plenty of oxygenated blood circulating to the flight muscles. | text | null |
L_0378 | birds | T_2068 | Birds have relatively big brains for their body size. This is reflected in their high level of intelligence and complex behavior. Some birds, including crows, are more intelligent than many mammals. They are smart enough to use tools to solve problems. You can see this in the video below. However, the part of the brain that is most developed in birds is the part that controls flying. This is another adaptation for flight. MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0378 | birds | T_2069 | Birds reproduce sexually and have separates sexes. Fertilization occurs internally, so males and females must mate. Many bird species have special behaviors, such as unique songs or visual displays, for attracting mates. These special behaviors are called courtship. The white peacock in Figure 14.3 is putting on a stunning display of his amazing tail feathers to court a mate. | text | null |
L_0378 | birds | T_2070 | After mating and fertilization occur, eggs are laid, usually in a nest. Most birds build nests for their eggs and hatchlings, and each species has a certain way of doing it. You can see examples of different types of bird nests in Figure 14.4. Nests range from little more than a depression in the ground (killdeer) to elaborately built structures (weaver bird). You can see how skillful a weaver bird is at weaving its nest by watching this video: MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0378 | birds | T_2070 | After mating and fertilization occur, eggs are laid, usually in a nest. Most birds build nests for their eggs and hatchlings, and each species has a certain way of doing it. You can see examples of different types of bird nests in Figure 14.4. Nests range from little more than a depression in the ground (killdeer) to elaborately built structures (weaver bird). You can see how skillful a weaver bird is at weaving its nest by watching this video: MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0378 | birds | T_2071 | In most species, one or both parents take care of the eggs. They sit on the eggs to keep them warm until they hatch. This is called incubation. After the eggs hatch, the parents generally continue their care. They feed the hatchlings until they are big enough to feed on their own. This is usually at a younger age in ground-nesting birds such as ducks than in tree-nesting birds such as robins. | text | null |
L_0378 | birds | T_2072 | There are about 10,000 living species of birds. Almost all of them can fly. Very few birds are flightless. | text | null |
L_0378 | birds | T_2073 | Birds that can fly are classified in 29 orders. Birds in the different orders vary in their physical traits and how they behave. You can see seven of the most common orders of flying birds in Table 14.1. The majority of flying birds are perching birds, described in the last row of the table. There are more species in this order than in all other bird orders combined. Many perching birds are familiar songbirds such as the mockingbird. You can hear a mockingbirds amazing and complex song in this video: http://youtu.be/NNNX3f3_svo Order Landfowl: pheasants Description They are large in size; they spend most of their time on the ground; they usually have a thick neck and short, rounded wings; their flight tends to be brief and close to the ground. Example turkey Waterfowl: ducks, geese, swans They are large in size; they spend most of their time on the water sur- face; they have webbed feet and are good swimmers; most are strong flyers. ducks Shorebirds: puffins, gulls, plovers They range from small to large; most live near the water, and some are sea birds; they have webbed feet and are good swimmers; most are strong flyers. puffin Diurnal Raptors: hawks, falcons, eagles They range from small to large; they are active during the day and sleep during the night; they have a sharp, hooked beak and strong legs with clawed feet; they hunt by sight and have excellent vision. hawk Nocturnal Raptors: burrowing owls, barn owls, horned owls They range from small to large; they are active during the night and sleep during the day; they have a sharp, hooked beak and strong legs with clawed feet; they have large, forward-facing eyes; they have ex- cellent hearing and can hunt with their sense of hearing alone. burrowing owl turkeys, chickens, Order Parrots: cockatoos, parrots, para- keets Description They range from small to large; they are found in tropical regions; they have a strong, curved bill; they stand upright on strong legs with clawed feet; many are brightly col- ored; they are very intelligent. Example cockatoo Perching Birds: honeyeaters, spar- rows, crows They are small in size; they perch above the ground in trees and on buildings and wires; they have four toes for grasping a perch; many are songbirds. honeyeater | text | null |
L_0378 | birds | T_2074 | Some birds lost the ability to fly during their evolution. They include the ostrich, pictured above in Figure 14.1, as well as the kiwi, rhea, cassowary, and moa. All of these birds have long legs that are adapted for running. Penguins, like the one pictured in Figure 14.5, are also flightless, but they have a very different body shape. They are adapted for swimming instead of running. | text | null |
L_0378 | birds | T_2075 | Birds are endothermic. They can maintain a warm body temperature even in a cold climate. Therefore, they can live in a wider range of habitats than ectothermic vertebrates such as amphibians and reptiles. | text | null |
L_0378 | birds | T_2076 | Birds live and breed in most terrestrial habitats on Earth. They can be found on all seven continents, from the Arctic to Antarctica. However, the majority of bird species are native to tropical areas of the planet. | text | null |
L_0378 | birds | T_2077 | Birds may be specialists or generalists in terms of what they eat. Generalists are organisms that eat many different types of food. Birds that are generalists include the red-winged blackbird in Figure 14.6. It has a basic beak that can eat many different foods. Red-winged blackbirds are omnivores. They may eat a wide variety of seeds as well as insects and other small animals such as snails and frogs. Specialists are organisms that eat just one type of food. Birds that are specialists include ospreys, which eat only live fish. You can see an osprey in Figure 14.7. The ospreys feet are very well-adapted for catching fish. Its eyes are also well-adapted for seeing fish under the water. Its beak is well suited for gripping and ripping into fish flesh. Ospreys are so well-adapted to catching fish that they cant catch anything else! | text | null |
L_0379 | mammals | T_2078 | Mammals are endothermic vertebrates with four limbs. Examples of mammals include bats, whales, mice, and humans. Clearly, mammals are a very diverse group. Nonetheless, they share several traits that set them apart from other vertebrates. | text | null |
L_0379 | mammals | T_2079 | Two traits are used to define the mammal class. They are fur or hair and mammary glands in females. All mammals have fur or hair on their skin. It provides insulation and helps keep the body warm. It also can be used for sensing. For example, cats can feel with their whiskers. All female mammals have mammary glands. Mammary glands are glands that produce milk after the birth of offspring. Producing milk for offspring is called lactation. The colt in Figure 14.9 is getting milk from its mother. | text | null |
L_0379 | mammals | T_2079 | Two traits are used to define the mammal class. They are fur or hair and mammary glands in females. All mammals have fur or hair on their skin. It provides insulation and helps keep the body warm. It also can be used for sensing. For example, cats can feel with their whiskers. All female mammals have mammary glands. Mammary glands are glands that produce milk after the birth of offspring. Producing milk for offspring is called lactation. The colt in Figure 14.9 is getting milk from its mother. | text | null |
L_0379 | mammals | T_2080 | Most mammals share several other traits. These include: a large, complex brain and relatively great intelligence; ears with specialized structures that make them extremely good at hearing; four different types of teeth (reptiles have just one type), allowing them to eat a wide range of foods; tiny air sacs called alveoli (alveolus, singular) in the lungs for enhanced gas exchange; and glands in the skin that produce sweat, a salty fluid that helps cool down the body. | text | null |
L_0379 | mammals | T_2081 | Mammals are noted for the many ways they can move. Some mammals are well known for their speed. The fastest land animal is a mammal, the cheetah. It can race at speeds of up to 112 kilometers (70 miles) per hour. The limbs of most mammals are specialized for a particular way of moving. They may be specialized for running, jumping, climbing, flying, gliding, or swimming. The limbs of some mammals are even specialized for swinging through tree tops. You can see mammals with some of these specializations in Figure 14.10. | text | null |
L_0379 | mammals | T_2082 | Mammals have a variety of ways to keep their body temperature stable. | text | null |
L_0379 | mammals | T_2083 | Mammals stay warm in cool weather in two general ways. One way is by generating more heat. The other way is by conserving the heat that is generated. Mammals generate heat mainly by maintaining a high rate of metabolism. Compared with the cells of other animals, the cells of mammals have more mitochondria. Mitochondria are the cell organelles that generate energy. Mammals may also produce little bursts of heat by shivering. Shivering occurs when many muscles all contract slightly at the same time. The muscle contractions generate a small amount of heat. Mammals conserve heat with their hair or fur. It works like the layer of insulation in the walls of a house. It traps warm air next to the skin so it cant escape into the environment. Like the squirrel in Figure 14.11, most mammals can make their hair or fur stand up from the skin. This makes it a better insulator. Mammals also have a layer of insulating fat beneath their skin. Other vertebrates lack this layer of fat. | text | null |
L_0379 | mammals | T_2084 | In hot weather, mammals may need to lose excess body heat. One way they do this is by increasing blood flow to the body surface. The increased blood flow warms the skin, which gives off heat to the environment. Most mammals also sweat to lose excess heat. Sweating wets the skin. Evaporation of the sweat requires heat. The heat comes from the body and cools it down. Animals with fur, like the dogs in Figure 14.12, may pant instead of sweat to lose body heat. Water evaporates from the tongue and other moist surfaces of the mouth, using heat from the body. Watch this video to learn about some unique ways that elephants lose excess heat: MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0379 | mammals | T_2085 | Generating body heat to stay warm takes a lot of energy. Mammals are heterotrophs that get their energy by eating other organisms. Mammals eat a wide range of different foods. Except for leaf litter and wood, almost any kind of organic matter is consumed by some type of mammal. The organic matter typically comes from plants, other animals, or some mix of these sources. | text | null |
L_0379 | mammals | T_2086 | Many mammals are herbivores. Herbivores are heterotrophs that eat only or mainly plant foods (or algae). Depend- ing on the species of mammals, they may eat leaves, shoots, stems, roots, seeds, nuts, fruits, flowers, and/or grasses. Some mammals even eat conifer needles or tree bark. Mammals that are herbivores include rabbits, mice, sheep, zebras, deer, kangaroos, and monkeys. The manatee in Figure 14.13 is also a herbivorous mammal. It eats mainly kelp (seaweed). | text | null |
L_0379 | mammals | T_2086 | Many mammals are herbivores. Herbivores are heterotrophs that eat only or mainly plant foods (or algae). Depend- ing on the species of mammals, they may eat leaves, shoots, stems, roots, seeds, nuts, fruits, flowers, and/or grasses. Some mammals even eat conifer needles or tree bark. Mammals that are herbivores include rabbits, mice, sheep, zebras, deer, kangaroos, and monkeys. The manatee in Figure 14.13 is also a herbivorous mammal. It eats mainly kelp (seaweed). | text | null |
L_0379 | mammals | T_2087 | Some mammals are carnivores. Carnivores are heterotrophs that eat only or mainly animal foods. Depending on their species, carnivorous mammals may eat other mammals, birds, reptiles, amphibians, fish, mollusks, worms, and/or insects. Mammals that are carnivores include anteaters, whales, hyenas, wolves, and seals. The bat in Figure | text | null |
L_0379 | mammals | T_2088 | Some mammals are omnivores. Omnivores are heterotrophs that eat a mix of plant and animal foods. Mammals that are omnivores include bears, foxes, rats, pigs, and human beings. The chimpanzees in Figure 14.15 are also omnivorous mammals. In the wild, they eat mainly plant foods, but they supplement plants with birds, bird eggs, insects, small monkeys, and other small mammals. Their favorite and most common food, however, is fruit. Animals that eat mainly fruit are called frugivores. | text | null |
L_0379 | mammals | T_2089 | Mammals have separate sexes and reproduce sexually. They produce eggs or sperm and must mate in order for fertilization to occur. A few mammals are oviparous. They lay eggs, which later hatch. These mammals are called monotremes. Most mammals are viviparous and give birth to live young. These mammals are either placental mammals or marsupials. Placental mammals give birth to relatively large and well-developed fetuses. Marsupials give birth to smaller, less-developed embryos. In both placental and marsupial mammals, the young grow and develop inside the mothers body in an organ called the uterus. At birth, they pass through a tube-like organ called the birth canal, or vagina. | text | null |
L_0379 | mammals | T_2090 | Placental mammals get their name from the placenta. This is a spongy structure that develops during pregnancy only in placental mammals. You can see where a human placenta forms in Figure 14.16. The placenta sustains the fetus while it grows inside the mothers uterus. It consists of membranes and blood vessels from both mother and fetus. It allows substances to pass between the mothers blood and that of the fetus. The fetus gets oxygen and nutrients from the mother. It passes carbon dioxide and other wastes to the mother. The placenta permits a long period of fetal growth. As a result, the fetus can become relatively large and mature before birth. This increases its chances of survival. On the other hand, supporting a growing fetus may be difficult for the mother. She has to eat more while pregnant and may become less mobile as the fetus grows larger. Giving birth to a large infant is also risky. | text | null |
L_0379 | mammals | T_2091 | By giving birth to tiny embryos, marsupial mothers are at less risk. However, the tiny newborn marsupial may be less likely to survive than a newborn placental mammal. The marsupial embryo completes its growth and development outside the mothers body in a pouch. It gets milk by sucking on a nipple in the pouch. There are very few living species of marsupials. They include kangaroos, koalas, and opossums. You can see a baby koala peeking out of its mothers pouch in Figure 14.17. | text | null |
L_0379 | mammals | T_2092 | There are very few living species of monotremes, or egg-laying mammals. They include the echidna and platypus, both pictured in Figure 14.18. Monotremes are found only in Australia and the nearby island of New Guinea. Female monotremes lack a uterus and vagina. Instead, they have a cloaca with one external opening, like the cloaca of reptiles and birds. The opening is used to excrete wastes as well as lay eggs. The eggs of monotremes have a leathery shell, like the eggs of reptiles. Female monotremes have mammary glands but not nipples. They secrete milk to feed their young from a patch on their belly. This form of reproduction is least risky for the mother but most risky for the offspring. | text | null |
L_0379 | mammals | T_2092 | There are very few living species of monotremes, or egg-laying mammals. They include the echidna and platypus, both pictured in Figure 14.18. Monotremes are found only in Australia and the nearby island of New Guinea. Female monotremes lack a uterus and vagina. Instead, they have a cloaca with one external opening, like the cloaca of reptiles and birds. The opening is used to excrete wastes as well as lay eggs. The eggs of monotremes have a leathery shell, like the eggs of reptiles. Female monotremes have mammary glands but not nipples. They secrete milk to feed their young from a patch on their belly. This form of reproduction is least risky for the mother but most risky for the offspring. | text | null |
L_0379 | mammals | T_2093 | Mammals are a class in Phylum Chordata. Monotremes, marsupials, and placental mammals are subclasses of mammals. Almost all living mammals are placental mammals. Placental mammals, in turn, are divided into many orders. Some of the larger orders are described in Table 14.2. Order Insectivora Example mole Sample Trait small sharp teeth Chiroptera bat digits support membranous wings Order Carnivora Example coyote Sample Trait long pointed canine teeth Rodentia mouse incisor teeth grow continuously Lagomorpha rabbit chisel-like incisor teeth Artiodactyla deer even-toed hooves Cetacea whale paddle-like forelimbs Primates monkey five digits on hands and feet The orders in Table 14.2 are still widely used, but ideas about mammal classification are constantly changing. Traditional classifications are based on similarities and differences in physical traits. More recent classifications are based on similarities and differences in DNA. The latter are more useful for determining how mammals evolved. | text | null |
L_0380 | primates | T_2094 | A primate is a mammal in the Primate Order of placental mammals. In addition to human beings, this order consists of lemurs, tarsiers, monkeys, and apes. It includes mammals that range in size from the tiny mouse lemur, which weighs only 30 g (about an ounce), to the majestic gorilla, an ape that may weigh as much as 200 kg (440 lb). Both a mouse lemur and gorilla are pictured in Figure 14.19. | text | null |
L_0380 | primates | T_2095 | Primates are generally divided into prosimian and non-prosimian primates. Primates called prosimians are generally smaller. There are also far fewer of them. Prosimians include lemurs, such as the mouse lemur in Figure 14.19, and lorises. Prosimians are thought to be more similar to the earliest primates. All other primates are non-prosimian primates. They are placed in groups that include tarsiers, New World (Central and South America) monkeys, Old World (Africa and Asia) monkeys, apes, and humans. You can see examples of non-prosimian primates in Figure 14.20. | text | null |
L_0380 | primates | T_2095 | Primates are generally divided into prosimian and non-prosimian primates. Primates called prosimians are generally smaller. There are also far fewer of them. Prosimians include lemurs, such as the mouse lemur in Figure 14.19, and lorises. Prosimians are thought to be more similar to the earliest primates. All other primates are non-prosimian primates. They are placed in groups that include tarsiers, New World (Central and South America) monkeys, Old World (Africa and Asia) monkeys, apes, and humans. You can see examples of non-prosimian primates in Figure 14.20. | text | null |
L_0380 | primates | T_2096 | A number of traits set primates apart from other orders of placental mammals. Primates evolved from tree-living, or arboreal, ancestors. As a result, many primate traits are adaptations for life in the trees. Living in trees requires good grasping ability. Being able to judge distances is also important. Primates have five digits (fingers or toes) on each extremity. Unlike the hooves of horses or the paddles of whales, the digits of primates are relatively unspecialized. Therefore, they can be used to do a variety of tasks, including grasping branches and holding tools. Most primates have opposable thumbs. An opposable thumb can be brought into opposition with the other fingers of the same hand. This allows the hand to grasp and hold things. Primates usually rely more on the sense of vision rather than the sense of smell, which is the dominant sense in many other mammals. The importance of vision in primates is reflected by the bony socket that surrounds and protects the primate eye. Primates have widely spaced eyes in the same plane that give them stereoscopic (3-D) vision, needed for judging distances. Some primates, including humans, have also evolved color vision. Primates tend to have bigger brains for their body size than other mammals. This is reflected in their relatively high level of intelligence and their ability to learn new behaviors. Primates have slower rates of development than other mammals their size. They reach maturity later and have longer lifespans. Being dependent on adults for a long maturation period gives young primates plenty of time to learn from their elders. | text | null |
L_0380 | primates | T_2097 | Except for humans and a few other species, most modern primates still live in trees at least some of the time. They live primarily in tropical rain forests of Central and South America, Africa, and South Asia. Some primates, such as the gibbon in Figure 14.21, have long arms and curving fingers that allow them to swing from branch to branch high up in trees. This way of traveling is called brachiation. You can watch a gibbon brachiating in this amazing video: MEDIA Click image to the left or use the URL below. URL: Fruit is the preferred food for almost all primates except humans. However, most primate species are omnivorous and consume a variety of plant and animal foods. For example, they may eat leaves, seeds, bird eggs, insects, and other small animals. Chimpanzees may band together and hunt for animals to kill and eat. They may even sharpen sticks and use them as spears when they hunt. Watch this video to see the incredible teamwork of a group of chimpanzees hunting a monkey: . MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0381 | understanding animal behavior | T_2098 | Why do animals behave in the ways pictured in Figure 15.1? The specific answer depends on what the behavior is. Male flamingoes put on a noisy group show in order to attract females for mating. Frogs call out to attract mates or to warn other frogs to stay away from their territory. Baby ducks follow their mother to stay close to her for protection and survival. Male elephant seals fight to defend their hunting territory from each other. All of these behaviors have the purpose of promoting reproduction or survival. Like the animals pictured above, all animals have behaviors that help them achieve these basic ends. Behaviors that help animals reproduce or survive increase their fitness. Animals with greater fitness have a better chance of passing their genes to the next generation. If genes control behaviors that increase fitness, the behaviors become more common in the species. In other words, they evolve by natural selection. | text | null |
L_0381 | understanding animal behavior | T_2099 | All of the animal behaviors pictured in Figure 15.1 are ways that animals act without being taught to act in these ways. Such behaviors are called innate. An innate behavior is any behavior that occurs naturally in all the animals of a given species. An innate behavior is also called an instinct. The first time an animal performs an innate behavior, the animal does it well. The animal doesnt have to practice the behavior in order to get it right or to become better at doing it. Innate behaviors are also predictable. All members of a species perform an innate behavior in the same way. | text | null |
L_0381 | understanding animal behavior | T_2100 | There are many other examples of innate behaviors in animals. Even behaviors that seem complex and difficult may be innate. For example, honeybees perform dances in order to communicate about food sources. When a honeybee, like the one in Figure 15.2, finds a food source, it returns to its hive and does a dance, called the waggle dance. The way the bee moves during its dance tells other bees in the hive where to find the food. Honeybees can do the waggle dance without learning it from other bees, so it is an innate behavior. Watch this video to see the waggle dance and find out what it communicates: http://video.nationalgeographic.com/video/weirdest-bees-dance MEDIA Click image to the left or use the URL below. URL: Three other examples of innate behavior are pictured in Figure 15.3. If an animal were to perform such behaviors incorrectly, it might be less likely to survive or reproduce. Can you explain why each behavior pictured in the figure is important for reproduction or survival? | text | null |
L_0381 | understanding animal behavior | T_2100 | There are many other examples of innate behaviors in animals. Even behaviors that seem complex and difficult may be innate. For example, honeybees perform dances in order to communicate about food sources. When a honeybee, like the one in Figure 15.2, finds a food source, it returns to its hive and does a dance, called the waggle dance. The way the bee moves during its dance tells other bees in the hive where to find the food. Honeybees can do the waggle dance without learning it from other bees, so it is an innate behavior. Watch this video to see the waggle dance and find out what it communicates: http://video.nationalgeographic.com/video/weirdest-bees-dance MEDIA Click image to the left or use the URL below. URL: Three other examples of innate behavior are pictured in Figure 15.3. If an animal were to perform such behaviors incorrectly, it might be less likely to survive or reproduce. Can you explain why each behavior pictured in the figure is important for reproduction or survival? | text | null |
L_0381 | understanding animal behavior | T_2101 | Innate behaviors occur in all animals. However, the more intelligent a species is, the fewer innate behaviors it generally has. The human species is the most intelligent animal species, and it has very few innate behaviors. The only innate behaviors in humans are reflex behaviors. A reflex behavior is a simple response that always occurs when a certain stimulus is present. Human reflex behaviors occur mainly in babies. You may have seen a baby exhibit the grasp reflex shown in Figure this way from birth to about 6 months of age. Its easy to see why this might help a baby survive. Grabbing onto something could keep a baby from falling and being injured. | text | null |
L_0381 | understanding animal behavior | T_2102 | Other than infant reflexes, human behaviors are mainly learned rather than innate behaviors. Learned behavior is behavior that occurs only after experience or practice. Did you ever teach a dog to sit on command? Thats an example of a learned behavior. The dog wasnt born knowing that it should sit when it hears the word sit. The dog had to learn the behavior. Most animals are capable of learning, but animals that are more intelligent are better at learning and depend more on learned behaviors. The big advantage of learned behaviors over innate behaviors is that learned behaviors are flexible. They can be changed to suit changing conditions. Human beings depend on learned behaviors more than any other species. Think about some of the behaviors you have learned. They might include making a bed, riding a bicycle, using a computer, and playing a sport, to name just a few. You may have learned each of the behaviors in different ways. There are several different ways in which animals learn. They include habituation, observational learning, conditioning, learning through play, and insight learning. | text | null |
L_0381 | understanding animal behavior | T_2103 | One of the simplest ways of learning that occurs in just about all animals is habituation. Habituation means learning to get used to something after being exposed to it repeatedly. It usually involves getting used to something that is frightening or annoying but not dangerous. Look at the crows in Figure 15.5. They are no longer afraid of the scarecrow. They have gotten used to a human in this location and know that it wont hurt them. Habituation lets animals ignore things that wont harm them. It allows them to avoid wasting time and energy escaping from things that arent really dangerous. | text | null |
L_0381 | understanding animal behavior | T_2104 | Do you remember how you learned to tie your shoe laces? You may have watched and copied the behavior of your mom or an older sibling. Learning by watching and copying the behavior of someone else is called observational learning. Human children learn many behaviors this way. Other animals also learn through observational learning. For example, the wolves in Figure 15.6 learned how to hunt in a group by watching and copying the hunting behaviors of older wolves in their pack. | text | null |
L_0381 | understanding animal behavior | T_2104 | Do you remember how you learned to tie your shoe laces? You may have watched and copied the behavior of your mom or an older sibling. Learning by watching and copying the behavior of someone else is called observational learning. Human children learn many behaviors this way. Other animals also learn through observational learning. For example, the wolves in Figure 15.6 learned how to hunt in a group by watching and copying the hunting behaviors of older wolves in their pack. | text | null |
L_0381 | understanding animal behavior | T_2105 | Conditioning is a way of learning that involves a reward or punishment. If you ever trained a dog to obey a command, you probably gave the dog a tasty treat each time he performed the desired behavior. It may not have been very long before the dog would reliably follow the command in order to get the treat. This is an example of conditioning that involves a reward. Conditioning does not always involve a reward. It can involve a punishment instead. For example, a dog might be scolded each time she jumps up on the sofa. After repeated scolding, she may learn to stay off the sofa. Conditioning occurs in nature as well. Here are just two examples: Bees learn to find nectar in certain types of flowers because they have found nectar in those types of flowers before. In this case, the behavior is learned because it is rewarded with nectar. Many birds learn to avoid eating monarch butterflies, like the one pictured in Figure 15.7. Monarch butterflies taste bad and make birds sick. In this case, the behavior is learned because it is punished with a nasty taste and illness. | text | null |
L_0381 | understanding animal behavior | T_2106 | Many animals, especially mammals, spend a lot of time playing when they are young. Although playing is fun, its likely that animals play for other reasons as well. Learning behaviors that will be important in adulthood is one likely outcome of play. Bear cubs, like the two bear cubs in Figure 15.8, frequently play together. They often pretend to be fighting. By play fighting they may be learning skills such as fighting and hunting that they will need as adults. Other young animals may play in different ways. For example, young deer play by running and kicking up their hooves. This may help them learn how to escape from predators. Human children learn by playing as well. For example, playing games and sports may help them learn how to follow rules and work with others. | text | null |
L_0381 | understanding animal behavior | T_2107 | Insight learning is learning from past experiences and reasoning. It generally involves coming up with new ways to solve problems. Insight learning generally happens quickly. An animal has a sudden flash of insight. Insight learning requires relatively great intelligence. Human beings use insight learning more than any other species. They have used it to invent the wheel to land astronauts on the moon. Think about problems you have solved. You may have figured out how to solve a new type of math problem or how to get to the next level of a video game. If you relied on your past experiences and reasoning to do it, then you were using insight learning. One type of insight learning is making tools to solve problems. Scientists used to think that humans were the only animals intelligent enough to make tools. In recent decades, however, there have been many observations of other animal species using tools. They range from monkeys and chimpanzees to crows. You can see a monkey using a stone tool in Figure 15.9. She is using the stone to crack open the shells of marine invertebrates such as oysters. Chimpanzees have been observed using sticks to fish for termites in a termite mound. Crows have been seen bending wire to form a hook in order to pull food out of a tube. Behaviors such as these show that other species of animals besides humans can use their experience and reasoning to solve problems. They can learn through insight. | text | null |
L_0382 | types of animal behavior | T_2108 | Communication is any way that animals share information. Many animals live in social groups. For these animals, being able to communicate is essential. Communicating increases the ability of group members to cooperate and avoid conflict. Communication may help animals work together to find food and defend themselves from predators. It also helps them find mates and care for their offspring. In addition, communication helps adult animals teach the next generation learned behaviors. Therefore, communication generally improves the chances of animals surviving and reproducing. | text | null |
L_0382 | types of animal behavior | T_2109 | Different animal species use a range of senses for communicating. They may communicate using hearing, sight, or smell. Animals that communicate by making and hearing sounds include frogs, birds, and monkeys. Frogs call out to attract mates. Birds may use calls to warn other birds to stay away or to tell them to flock together. Monkeys use warning calls to tell other troop members that a predator is near. Animals may communicate by sight with gestures, body postures, or facial expressions. Look at the cat in Figure 15.11. Theres no mistaking the meaning of its arched back, standing hair, and exposed fangs. Its clearly saying stay away, or else! Bees communicate with a waggle dance. They use it to tell other bees where food is located. A wide range of animals communicate by releasing chemicals they can smell or detect in some other way. They include animals as different as ants and dogs. An ant, for example, releases chemicals to mark the trail to a food source. Other ants in the nest can detect the chemicals with their antennae and find the food. Look at the dog in Figure 15.12. Its marking its territory with a chemical that it releases in urine. It does this to keep other dogs out of its yard. | text | null |
L_0382 | types of animal behavior | T_2110 | Humans communicate with each other in a variety of ways. Chiefly, however, we use sound and sight to share information. The most important way that humans communicate is with language. Language is the use of symbols to communi- cate. In human languages, the symbols are words. Words may stand for things, people, actions, feelings, or ideas. By combining words in sentences, language can be used to express very complex thoughts. Another important way that humans communicate is with facial expressions. Look at the facial expressions of the girl in Figure 15.13. You can probably tell what emotion she is trying to convey with each expression. From left to right, she looks happy, sad, and angry. Humans also commonly use gestures and body postures to communicate. You might answer a question by shrugging your shoulders, which means I dont know. You might use a thumbs-up gesture when a friend scores a goal to mean Good job. Can you think of other gestures you commonly use to communicate with others? | text | null |
L_0382 | types of animal behavior | T_2110 | Humans communicate with each other in a variety of ways. Chiefly, however, we use sound and sight to share information. The most important way that humans communicate is with language. Language is the use of symbols to communi- cate. In human languages, the symbols are words. Words may stand for things, people, actions, feelings, or ideas. By combining words in sentences, language can be used to express very complex thoughts. Another important way that humans communicate is with facial expressions. Look at the facial expressions of the girl in Figure 15.13. You can probably tell what emotion she is trying to convey with each expression. From left to right, she looks happy, sad, and angry. Humans also commonly use gestures and body postures to communicate. You might answer a question by shrugging your shoulders, which means I dont know. You might use a thumbs-up gesture when a friend scores a goal to mean Good job. Can you think of other gestures you commonly use to communicate with others? | text | null |
L_0382 | types of animal behavior | T_2110 | Humans communicate with each other in a variety of ways. Chiefly, however, we use sound and sight to share information. The most important way that humans communicate is with language. Language is the use of symbols to communi- cate. In human languages, the symbols are words. Words may stand for things, people, actions, feelings, or ideas. By combining words in sentences, language can be used to express very complex thoughts. Another important way that humans communicate is with facial expressions. Look at the facial expressions of the girl in Figure 15.13. You can probably tell what emotion she is trying to convey with each expression. From left to right, she looks happy, sad, and angry. Humans also commonly use gestures and body postures to communicate. You might answer a question by shrugging your shoulders, which means I dont know. You might use a thumbs-up gesture when a friend scores a goal to mean Good job. Can you think of other gestures you commonly use to communicate with others? | text | null |
L_0382 | types of animal behavior | T_2111 | Without communication, animals would not be able to live together in groups. Animals that live in groups with other members of their species are called social animals. Social animals include many species of insects, birds, and mammals. Specific examples are ants, bees, crows, wolves, and human beings. | text | null |
L_0382 | types of animal behavior | T_2112 | Some species of animals are very social. In these species, members of the group depend completely on one another. Thats because different animals within the group have different jobs. Therefore, group members must work together for the good of all. Most species of bees and ants are highly social animals. Look at the honeybees in Figure 15.14. Honeybees live in colonies that may consist of thousands of individual bees. Generally, there are three types of adult bees in a colony: workers, a queen, and drones. Most of the adult bees in a colony are workers. They cooperate to build the hive, collect food, and care for the young. Each worker has a specific task to perform, depending on its age. Young worker bees clean the hive and feed the offspring. Older worker bees build the waxy honeycomb or guard the hive. The oldest worker bees leave the hive to find food. Each colony usually has one queen. Her only job is to lay eggs. The colony also has a relatively small number of male drones. Their only job is to mate with the queen. | text | null |
L_0382 | types of animal behavior | T_2113 | Bees and other social animals must cooperate to live together successfully. Cooperation means working together with others. Members of the group may cooperate by dividing up tasks, defending each other, and sharing food. The ants in Figure 15.15 are sharing food. One ant is transferring food directly from its mouth to the mouth of another colony member. Besides social insects, animals in many other species also cooperate. For example, in meerkat colonies, young female meerkats act as babysitters. They take care of the baby meerkats while their parents are out looking for food. | text | null |
L_0382 | types of animal behavior | T_2114 | Some of the most important behaviors in animals involve reproduction. They include behaviors to attract mates and behaviors for taking care of the young. | text | null |
L_0382 | types of animal behavior | T_2115 | Mating is the pairing of an adult male and an adult female for the purpose of reproduction. In many animal species, females choose the males they will mate with. For their part, males try to show females that they would be better mates than other males. To be chosen as mates, males may perform courtship behaviors. These are special behaviors that help attract a mate. Male courtship behaviors are meant to get the attention of females and show off a males traits. Different species of animals have different courtship behaviors. An example of courtship behavior in birds is shown in Figure 15.16. The bird in the picture is a male sharp-tailed grouse, and hes doing a courtship dance. Each year in the spring, as many as two dozen grouse males gather in a grassy area to perform their courtship dance. Female grouse watch the dance and then mate with the males that put on the best display. You can see a group of male grouse performing their courtship dance in this short video: . MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0382 | types of animal behavior | T_2116 | In most species of birds and mammals, one or both parents care for the young. This may include building a nest or other shelter. It may also include feeding the young and protecting them from predators. Caring for the young increases their chances of surviving. This, in turn, increases the parents fitness, so such behaviors evolve by natural selection. Emperor penguins make great sacrifices to take care of their young. After laying an egg, a penguin mother returns to the sea for two months to feed. Her mate stays behind to keep the egg warm. He balances the egg on top of his feet to keep it warm for the entire time the mother is away. During this time, he goes without food. To survive the cold, he huddles together with other males. If the chick hatches before the mother returns, the father feeds it with a high-protein, high-fat substance he produces just for this purpose. You can see an emperor penguin father feeding his chick in Figure 15.17. | text | null |
L_0382 | types of animal behavior | T_2116 | In most species of birds and mammals, one or both parents care for the young. This may include building a nest or other shelter. It may also include feeding the young and protecting them from predators. Caring for the young increases their chances of surviving. This, in turn, increases the parents fitness, so such behaviors evolve by natural selection. Emperor penguins make great sacrifices to take care of their young. After laying an egg, a penguin mother returns to the sea for two months to feed. Her mate stays behind to keep the egg warm. He balances the egg on top of his feet to keep it warm for the entire time the mother is away. During this time, he goes without food. To survive the cold, he huddles together with other males. If the chick hatches before the mother returns, the father feeds it with a high-protein, high-fat substance he produces just for this purpose. You can see an emperor penguin father feeding his chick in Figure 15.17. | text | null |
L_0382 | types of animal behavior | T_2117 | Some species of animals are territorial. This means that they defend an area that typically includes their nest and enough food for themselves and their offspring. Animals generally dont fight to defend their territory. Instead, they are more likely to put on a defensive display. For example, male gorillas may pound on their chest and thump the ground to warn other male gorillas to stay away from their territory. This gets the message across without physical conflict, which would be riskier and take more energy. You can see a male gorilla putting on a defensive display in this video: . MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0382 | types of animal behavior | T_2118 | Many animal behaviors occur in repeated cycles. Some cycles of behavior repeat each year. Other cycles of behavior repeat each day. | text | null |
L_0382 | types of animal behavior | T_2119 | Examples of behaviors with annual cycles include migration and hibernation. Both are innate behaviors. They are triggered by changes in the environment, such as the days growing shorter in the fall. Migration is the movement of animals from one place to another. Migration is most common in birds, fish, and insects. In the Northern Hemisphere, many species of birds, such as finches and swallows, travel south for the winter. They migrate to areas where it is warmer and where more food is available. They return north in the spring. Migrating animals generally follow the same route each year. They may be guided by the position of the sun, Earths magnetic field, or other clues in the environment. Hibernation is a state in which an animals body processes slow down and its body temperature falls. A hibernating animal uses less energy than usual. This helps it survive during a time of year when food is scarce. Hibernation may last for weeks or even months. Examples of animals that hibernate include some species of bats, squirrels, snakes, and insects (see Figure 15.18). | text | null |
L_0382 | types of animal behavior | T_2120 | Many animals go through daily cycles. Daily cycles of behavior are called circadian rhythms. For example, most animals go to sleep when the sun sets down and wake up when the sun rises. These animals are active during the day and called diurnal. Other animals go to sleep when the sun rises and wake up when the sun sets. These animals are active during the night and called nocturnal. Many owls, like the owls in Figure 15.19, are nocturnal. Like some other nocturnal animals, they have large eyes that are specially adapted for seeing when light levels are low. In many species, including the human species, circadian rhythms are controlled by a tiny structure called the biological clock. It is located in the hypothalamus, which is 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 biological clock, in turn, is controlled by changes in the amount of light entering the eyes. Thats why the biological clock causes changes that repeat every 24 hours. | text | null |
L_0388 | choosing healthy foods | T_2164 | MyPlate is a diagram that shows you how to balance foods at each meal. It represents the relative amounts of five food groups that you should put on your plate (and in your cup). You can see MyPlate in Figure 17.6. The five food groups in MyPlate are: 1. 2. 3. 4. 5. Grains, such as whole-grain bread, pasta, and cereal. Vegetables, such as spinach, broccoli, and carrots. Fruits, such as oranges, strawberries, and bananas. Dairy, such as milk, yogurt, and cheese. Protein, such as meat, fish, and beans Follow these guidelines for using MyPlate: Enjoy your food, but eat less. Avoid oversized portions. Make half your plate fruits and vegetables, including both green and yellow or orange vegetables. Make at least half your grains whole grains. Choose fat-free or low-fat milk. Avoid high-sodium foods. Drink water instead of sugary drinks. Youll notice that there is no food group on MyPlate for foods like ice cream, cookies, and potato chips. These foods have little nutritional value. They may also be high in fats, sugars, or salt. They should be eaten only sparingly if at all. | text | null |
L_0388 | choosing healthy foods | T_2165 | How do you know which foods contain whole grain and which are low in fat and sodium? Thats where food labels come in. In the U.S., packaged foods must be labeled with nutritional information. A nutrition facts label shows the main nutrients in one serving of the food. Packaged foods must also be labeled with their ingredients. An ingredient is a specific item that a food contains. | text | null |
L_0388 | choosing healthy foods | T_2166 | Look at the nutrition facts label in Figure 17.7. Instructions at the right of the label tell 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. For this food, 1 cup is a serving. The Calories in one serving are listed next. In this food, there are 250 Calories per serving. Next on the nutrition facts label, look for the percent daily values (% DV) of several nutrients. The percent daily value shows what percent of daily needs for a given nutrient that the food provides (based on a 2000- Calorie-per-day diet). A food is low in a nutrient if the %DV is 5% or less. This particular food is low in fiber, vitamin A, vitamin C, and iron. A food is high in a nutrient if the %DV is 20% or more. This food is high in sodium, potassium, and calcium. To learn more about nutrition facts labels and how to use them, watch this video: MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0388 | choosing healthy foods | T_2167 | The food label in Figure 17.8 represents a different food and includes the list of ingredients. The main ingredient is always listed first. The main ingredient is the ingredient that is present in the food in the greatest amount. As you go down the list, the ingredients are present in smaller and smaller amounts. Reading the ingredients lists on food labels can help you choose the healthiest foods. At the top of the list, look for ingredients such as whole grains, vegetables, fruits, and low-fat milk. Ingredients such as these are needed in the greatest amounts for balanced eating. Avoid foods that list fats, oils, sugar, or salt near the top of the list. For good health, you should avoid getting too much of these ingredients. Be aware that ingredients such as corn syrup are sugars. You should also use moderation when eating foods that contain ingredients such as white flour or white rice. These ingredients have been processed, and processing removes nutrients. The word enriched is a clue that an ingredient has been processed. Ingredients are enriched with added nutrients to replace those lost during processing. Even so, they are still likely to have fewer nutrients than unprocessed ingredients. | text | null |
L_0388 | choosing healthy foods | T_2168 | Physical activity is an important part of balanced eating. It helps you use up any extra Calories in the foods you eat. You should try to get at least an hour of exercise just about every day (see Figure 17.9). Exercise has many health benefits in addition to balancing the energy in food. For example, it strengthens the bones and muscles and may improve your mood. | text | null |
L_0388 | choosing healthy foods | T_2169 | What happens if you dont get enough exercise to balance the food you eat? Any unused energy in the food is stored as fat. 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 diagnosed in people who have a high percentage of body fat. A measure called Body Mass Index, or BMI, is often used to diagnose obesity. You can learn more about BMI by watching this video: MEDIA Click image to the left or use the URL below. URL: Obesity is associated with many health problems, including high blood pressure and diabetes. People that remain obese during their entire adulthood usually do not live as long as people that stay within a healthy weight range. The current generation of young people in the U.S. is the first generation in our history that may have a shorter life span than their parents because of obesity and the health problems associated with it. | text | null |
L_0388 | choosing healthy foods | T_2170 | You can avoid gaining too much weight and becoming obese. Choose healthy foods and balance the energy in food with exercise. To choose healthy foods, use MyPlate and nutrition facts labels. On food labels, pay attention to Calories as well as nutrients. Keep in mind that the average 1113 year old needs about 2000 Calories a day. To balance energy with exercise, aim to get about an hour of physical activity each day. You can use an online calculator like this one to find the number of Calories you use in a wide range of activities: | text | null |
L_0411 | communities | T_2375 | Predation is a relationship in which members of one species consume members of another species. The consuming species is called the predator. The species that is consumed is called the prey. In Figure 23.8, the wolves are predators, and the moose is their prey. | text | null |
L_0411 | communities | T_2376 | A predator-prey relationship tends to keep the populations of both species in balance. Look at the graph in Figure population also increases. As the number of predators increases, more prey are captured. This causes the prey population to decrease, followed by the predator population decreasing again. | text | null |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.