1. THINK ABOUT IT –From tiny insects that dine on our blood, to bison that feed on prairie grasses, to giant blue whales that feed on plankton, all animals are heterotrophs that obtain nutrients and energy from food. –In fact, adaptations for different styles of feeding are a large part of what makes animals so interesting.

2. Obtaining Food –How do animals obtain food?

3. Obtaining Food – How do animals obtain food? –Filter Feeders –Detrivores –Herbivores –Carnivores –Omnivores

4. Obtaining Food – As the old saying goes, you are what you eat. –For animals, we can rephrase that as “how you look and act depends on what and how you eat.” –The converse is also true: What and how you eat depends on how you look and act.

5. Filter Feeders – Most filter feeders catch algae and small animals by using modified gills or other structures as nets that filter food items out of water. –Many invertebrate filter feeders are small or colonial organisms, like worms and barnacles that spend their adult lives in a single spot. –Many vertebrate filter feeders such as whale sharks and blue whales, on the other hand, are huge, and feed while swimming.

6. Detritivores – Detritivores feed on detritus, often obtaining extra nutrients from the bacteria, algae, and other microorganisms that grow on and around it. –Detritus is made up of decaying bits of plant and animal material. –From earthworms on land to a wide range of aquatic worms and crustaceans like the cleaner shrimp, detritivores are essential components of many ecosystems.

7. Carnivores – Carnivores eat other animals. –Mammalian carnivores, such as wolves or orcas, use teeth, claws, and speed or stealthy hunting tactics to bring down prey. –Some carnivorous invertebrates, such as cnidarians, paralyze prey with poison-tipped darts, while some spiders immobilize their victims with venomous fangs.

8. Herbivores – Herbivores eat plants or parts of plants in terrestrial and aquatic habitats. –Some herbivores, such as locusts and cattle, eat leaves, which don’t have much nutritional content, are difficult to digest, and can contain poisons or hard particles that wear down teeth. –Other herbivores, including birds and many mammals, specialize in eating seeds or fruits, which are often filled with energy-rich compounds.

9. Nutritional Symbionts –Many animals rely upon symbiosis for their nutritional needs. –Symbiosis is the dependency of one species on another. – –Symbionts are the organisms involved in a symbiosis.

10. Parasitic Symbionts – Parasites live within or on a host organism, where they feed on tissues or on blood and other body fluids. –Some parasites cause serious diseases in humans, livestock, and crop plants. –Parasitic flatworms and roundworms afflict millions of people, particularly in the tropics.

11. Mutualistic Symbionts –In mutualistic relationships, both participants benefit. –Reef-building corals depend on symbiotic algae that live within their tissues for most of their energy. The algae, in turn, gain nutrition from the corals’ wastes and protection from algae eaters. –Animals that eat wood or plant leaves rely on microbial symbionts in their guts to digest cellulose.

12. Processing Food –How does digestion occur in animals?

13. Processing Food – How does digestion occur in animals? – Some invertebrates break down food primarily by intracellular digestion, but many animals use extracellular digestion to break down food.

14. Intracellular Digestion –The simplest animals, such as sponges, digest food inside specialized cells that pass nutrients to other cells by diffusion. –This digestive process is known as intracellular digestion.

15. Extracellular Digestion –Most more-complex animals rely on extracellular digestion. –Extracellular digestion is the process in which food is broken down outside cells in a digestive system and is then absorbed.

16. Gastrovascular Cavities – Some animals have an interior body space whose tissues carry out digestive and circulatory functions. –Some invertebrates, such as cnidarians, have a gastrovascular cavity with a single opening through which they both ingest food and expel wastes.

17. Gastrovascular Cavities –Some cells lining the gastrovascular cavity secrete enzymes and absorb digested food. –Other cells surround food particles and digest them in vacuoles. –Nutrients are then transported to cells throughout the body.

18. Digestive Tracts – Many invertebrates and all vertebrates, such as birds, digest food in a tube called a digestive tract, which has two openings. –Food moves in one direction, entering the body through the mouth. –Wastes leave through the anus.

19. Digestive Tracts – One-way digestive tracts often have specialized structures, such as a stomach and intestines, that perform different tasks as food passes through them. –In some animals, the mouth secretes digestive enzymes that start the chemical digestion of food. –Mechanical digestion may occur as specialized mouthparts or a muscular organ called a gizzard breaks food into small pieces.

20. Digestive Tracts – Chemical digestion begins or continues in a stomach that secretes digestive enzymes. –Chemical breakdown continues in the intestines, sometimes aided by secretions from other organs such as a liver or pancreas. –Intestines also absorb the nutrients released by digestion.

21. Solid Waste Disposal – No matter how efficiently an animal breaks down food and extracts nutrients, some indigestible material will always be left. –These solid wastes, or feces, are expelled through the single digestive opening, or anus.

22. Specializations for Different Diets –How are mouthparts adapted for different diets?

23. Specializations for Different Diets – How are mouthparts adapted for different diets? –Carnivores typically have sharp mouthparts or other structures that can capture food, hold it, and “slice and dice” it into small pieces. –Herbivores typically have mouthparts adapted to rasping or grinding.

24. Specialized Mouthparts –Carnivores and leaf-eating herbivores usually have very different mouthparts –Dental Formulae. – Humans - 2123

25. Eating Meat – sharp teeth that grab, tear, and slice food like knives and scissors would. The jaw bones and muscles of carnivores are adapted for up-and-down movements that chop meat into small pieces. - Dental formula 3131

26. Eating Plant Leaves – To digest leaf tissues, herbivores usually need to tear plant cell walls and expose their contents. –Many herbivorous invertebrates have mouthparts that grind and pulverize leaf tissues. –Dental Formula – 3003

27. Eating Plant Leaves – Herbivorous mammals, such as horses, have front teeth and muscular lips adapted to grabbing and pulling leaves, and flattened molars that grind leaves to a pulp. –The jaw bones and muscles of mammalian herbivores are also adapted for side-to-side “grinding” movements.

28. Specialized Digestive Tracts – Carnivorous invertebrates and vertebrates typically have short digestive tracts that produce fast-acting, meat-digesting enzymes. –These enzymes can digest most cell types found in animal tissues.

29. Specialized Digestive Tracts – No animal produces digestive enzymes that can break down the cellulose in plant tissue. –However, some herbivores have very long intestines or specialized pouches in their digestive tracts that harbor microbial symbionts that digest cellulose. –Cattle, for example, have a pouchlike extension of their stomach called a rumen (plural: rumina), in which symbiotic bacteria digest cellulose. –Animals with rumina, or ruminants, regurgitate food that has been partially digested in the rumen, chew it again, and reswallow it. This process is called “chewing the cud.”

30. THINK ABOUT IT –All animal tissues require oxygen for respiration and produce carbon dioxide as a waste product. For that reason, all animals must obtain oxygen from their environment and release carbon dioxide. How are different respiratory systems adapted to their different functions? RESPIRATION

31. Gaseous Exchange – What characteristics do the respiratory structures of all animals share?

32. Gaseous Exchange Characteristics –Respiratory structures provide a large surface area of moist, selectively permeable membrane. – Respiratory structures maintain a difference in the relative concentrations of oxygen and carbon dioxide on either side of the respiratory membrane, promoting diffusion.

33. Gas Exchange –Living cells can not actively pump oxygen or carbon dioxide across membranes. Yet, in order to breathe, all animals must exchange oxygen and carbon dioxide with their surroundings. –Animals have evolved respiratory structures that promote the movement of these gases in the required directions by passive diffusion.

34. Gas Diffusion and Membranes –Substances diffuse from an area of higher concentration to an area of lower concentration. –Gases diffuse most efficiently across a thin, moist membrane that is permeable to those gases. –The larger the surface area of that membrane, the more diffusion can take place.

35. Respiratory Surfaces of Aquatic Animals – How do aquatic animals breathe?

36. Respiratory Surfaces of Aquatic Animals – How do aquatic animals breathe? – Many aquatic invertebrates and most aquatic chordates other than reptiles and mammals exchange gases through gills. – Aquatic reptiles and aquatic mammals, such as whales, breathe with lungs and must hold their breath underwater.

37. Respiratory Surfaces of Aquatic Animals – Some aquatic invertebrates, such as cnidarians and some flatworms, are relatively small and have thin-walled bodies whose outer surfaces are always wet. –These animals rely on diffusion of oxygen and carbon dioxide through their outer body covering. –A few aquatic chordates, including lancelets, some amphibians, and even some sea snakes, rely on gas exchange by diffusion across body surfaces.

38. Respiratory Surfaces - Aquatic Animals –Many aquatic invertebrates and most aquatic chordates exchange gases through gills. –Gills are feathery structures that expose a large surface area of thin, selectively permeable membrane to water. –Inside gill membranes is a network of tiny, thin-walled blood vessels called capillaries.

39. –Many animals actively pump water over their gills as blood flows through inside. –As water passes over the gills, gas exchange is completed within the gill capillaries. Respiratory Surfaces - Aquatic Animals

40. –Aquatic reptiles and aquatic mammals, such as whales, breathe with lungs and must hold their breath underwater. –Lungs are organs that exchange oxygen and carbon dioxide between blood and air. Respiratory Surfaces - Aquatic Animals

41. Respiratory Surfaces of Terrestrial Animals What respiratory structures enable land animals to breathe?

42. – Respiratory structures in terrestrial invertebrates include skin, mantle cavities, book lungs, and tracheal tubes. –But all terrestrial vertebrates—reptiles, birds, mammals, and the land stages of most amphibians—breathe with lungs. Respiratory Surfaces of Terrestrial Animals

43. Respiratory Surfaces in Land Invertebrates Terrestrial invertebrates have a wide variety of respiratory structures. –Some land invertebrates, such as earthworms, that live in moist environments can respire across their skin, as long as it stays moist. –In other invertebrates, such as land snails, respiration is accomplished by the mantle cavity, which is lined with moist tissue and blood vessels.

44. Respiratory Surfaces in Land Invertebrates Spiders respire using organs called book lungs, which are made of parallel, sheetlike layers of thin tissues containing blood vessels.

45. –Most insects respire using a system of tracheal tubes that extends throughout the body. –Air enters and leaves the system through openings in the body surface called spiracles. Respiratory Surfaces in Land Invertebrates

46. Lung Structure in Vertebrates –Although lung structure in terrestrial vertebrates varies, the processes of inhaling and exhaling are similar.

47. Lung Structure in Vertebrates –Inhaling brings oxygen-rich air through the trachea, or airway, into the lungs. –Inside the lungs, oxygen diffuses into the blood through lung capillaries. –At the same time, carbon dioxide diffuses out of capillaries into the lungs. –Oxygen-poor air is then exhaled.

48. Amphibian, Reptilian, and Mammalian Lungs –The internal surface area of lungs increases from amphibians to reptiles to mammals.

49. Amphibian, Reptilian, and Mammalian Lungs –A typical amphibian lung is little more than a sac with ridges.

50. Amphibian, Reptilian, and Mammalian Lungs –Reptilian lungs are divided into chambers that increase the surface area for gas exchange.

51. Amphibian, Reptilian, and Mammalian Lungs –Mammalian lungs branch extensively and are filled with bubblelike structures called alveoli.

52. Amphibian, Reptilian, and Mammalian Lungs –Alveoli provide an enormous surface area for gas exchange, and enable mammals to take in the large amounts of oxygen required by their high metabolic rates.

53. Bird Lungs – In birds, the lungs are structured so that air flows mostly in only one direction, so no stale air gets trapped in the system. –Gas exchange surfaces are continuously in contact with fresh air. –This highly efficient gaseous exchange helps birds obtain the oxygen they need to power their flight muscles at high altitudes for long periods of time.

55. CIRCULATION

56. THINK ABOUT IT –How do energy and nutrients get to your body cells? –How does oxygen from your lungs get to your brain and the rest of your body? –How do carbon dioxide and wastes generated within your body get eliminated?

58. Hearts –Many animals move blood through their bodies using one or more hearts. –A heart is a hollow, muscular organ that pumps blood around the body. –A heart can be part of either an open or a closed circulatory system.

59. Open and Closed Circulatory Systems – How do open and closed circulatory systems compare?

60. Open and Closed Circulatory Systems In an open circulatory system, blood is only partially contained within a system of blood vessels as it travels through the body. In a closed circulatory system, blood circulates entirely within blood vessels that extend throughout the body.

61. Open Circulatory Systems –In an open circulatory system, blood is only partially contained within a system of blood vessels as it travels through the body. –Arthropods and most mollusks have open circulatory systems.

62. Open Circulatory Systems –One or more hearts or heartlike organs pump blood through vessels that empty into a system of sinuses, or spongy cavities, where blood comes into direct contact with body tissues. –Blood then collects in another set of sinuses and makes its way back to the heart.

63. –In a closed circulatory system, blood circulates entirely within blood vessels that extend throughout the body. –Many larger, more active invertebrates, including annelids and some mollusks, and all vertebrates have closed circulatory systems. –A heart or heartlike organ forces blood through vessels. Closed Circulatory Systems

64. –Nutrients and oxygen reach body tissues by diffusing across thin walls of capillaries, the smallest blood vessels. –Blood that is completely contained within blood vessels can be pumped under higher pressure and circulated more efficiently than can blood in an open system.

65. Single- and Double-Loop Circulation – How do the patterns of circulation in vertebrates compare?

66. Single- and Double-Loop Circulation –How do the patterns of circulation in vertebrates compare? –Most vertebrates with gills have a single- loop circulatory system with a single pump that forces blood around the body in one direction. – Most vertebrates that use lungs for respiration have a double-loop, two-pump circulatory system.

67. Single-Loop Circulation –Most vertebrates with gills have a single-loop circulatory system with a single pump that forces blood around the body in one direction. –In fishes, for example, the heart consists of two chambers: an atrium and a ventricle.

68. Single-Loop Circulation –The atrium receives blood from the body. –The ventricle then pumps blood out of the heart and to the gills. –Oxygen-rich blood travels from the gills to the rest of the body. Oxygen-poor blood then returns to the atrium.

69. Double-Loop Circulation –Most vertebrates that use lungs for respiration have a double-loop, two-pump circulatory system. –The first loop of the circulatory system is powered by one side of the heart and forces oxygen-poor blood from the heart to the lungs.

70. Double-Loop Circulation –The first loop, powered by one side of the heart, forces oxygen-poor blood from the heart to the lungs. –After the blood picks up oxygen and drops off carbon dioxide in the lungs, it returns to the heart. –The other side of the heart pumps oxygen-rich blood through the second circulatory loop to the rest of the body.

71. Mammalian Heart-Chamber Evolution – Amphibian hearts usually have three chambers: two atria and one ventricle. –The left atrium receives oxygen-rich blood from the lungs. –The right atrium receives oxygen-poor blood from the body. –Both atria empty into the ventricle. –Some mixing of oxygen-rich and oxygen-poor blood does occur, but the internal structure of the ventricle directs blood flow so that most oxygen- poor blood goes to the lungs and most oxygen-rich blood goes to the rest of the body.

72. Amphibian Circulatory System

73. Mammalian Heart- Chamber Evolution –Reptilian hearts, like that of this crocodile, typically have three chambers: two atria and one ventricle. –Most reptiles have a partial partition in their ventricle, resulting in less mixing of oxygen-rich and oxygen-poor blood than there is in amphibian hearts.

74. Reptilian Circulation

75. Mammalian Heart- Chamber Evolution –Four-chambered hearts like those in modern mammals are actually two separate pumps working next to one another. –During chordate evolution, partitions evolved that divided the original two chambers into four, transforming one pump into two parallel pumps. –The partitions also separated oxygen-rich blood from oxygen- poor blood.

76. EXCRETION

77. THINK ABOUT IT –In addition to carbon dioxide and indigestible material, animals generate other wastes that are released into body fluids and that must be eliminated from the body. –What are these wastes and how do animals get rid of them?

78. The Ammonia Problem –How do animals manage toxic nitrogenous waste?

79. The Ammonia Problem –How do animals manage toxic nitrogenous waste? – Animals either eliminate ammonia from the body quickly or convert it into other nitrogenous compounds that are less toxic.

80. The Ammonia Problem –The breakdown of proteins by cells releases a nitrogen-containing, or nitrogenous, waste: ammonia. –Ammonia is poisonous. Even moderate concentrations of ammonia can kill most cells.

81. The Ammonia Problem –The elimination of metabolic wastes, such as ammonia, is called excretion. –Some small animals that live in wet environments, such as some flatworms, rid their bodies of ammonia by allowing it to diffuse out of their body fluids across their skin. –Most larger animals have excretory systems that process ammonia and eliminate it from the body.

82. Storing Nitrogenous Wastes –Animals that cannot dispose of ammonia continuously, as it is produced, have evolved ways to store nitrogenous wastes until they can be eliminated.

83. Storing Nitrogenous Wastes –In most cases, ammonia itself cannot be stored in body fluids because it is too toxic. –Insects, reptiles, and birds convert ammonia into a sticky white compound called uric acid, which is much less toxic than ammonia and is also less soluble in water.

84. Storing Nitrogenous Wastes –Mammals and some amphibians convert ammonia to a different nitrogenous compound—urea. –Urea is less toxic than ammonia, but unlike uric acid, it is highly soluble in water.

85. Maintaining Water Balance –Excretory systems are extremely important in maintaining the proper balance of water in blood and body tissues. –In some cases, excretory systems eliminate excess water along with nitrogenous wastes. –In other cases, excretory systems must eliminate nitrogenous wastes while conserving water. –Many animals use kidneys to separate wastes and excess water from blood to form a fluid called urine.

86. Maintaining Water Balance –Kidneys separate water from waste products. –Kidney cells pump ions from salt to create osmotic gradients. –Water then “follows” those ions passively by osmosis. –Kidneys, however, usually cannot excrete excess salt.

87. Excretion in Aquatic Animals – How do aquatic animals eliminate wastes?

88. Excretion in Aquatic Animals –How do aquatic animals eliminate wastes? – In general, aquatic animals can allow ammonia to diffuse out of their bodies into surrounding water, which dilutes the ammonia and carries it away.

89. Freshwater Animals –Many freshwater invertebrates lose ammonia to their environment by simple diffusion across their skin. –Many freshwater fishes and amphibians eliminate ammonia by diffusion across the same gill membranes they use for respiration.

90. Freshwater Animals –The situation is more complex for some freshwater invertebrates and most freshwater fishes. –The bodies of freshwater animals, such as fishes, contain a higher concentration of salt than the water they live in.

91. Freshwater Animals –Water moves into their bodies by osmosis, mostly across the gills. –Salt diffuses out. –If they didn’t excrete water, they’d look like water balloons with eyes!

92. Freshwater Animals –Freshwater fish excrete water through kidneys that produce lots of watery urine. –They don't drink, and they actively pump salt in across their gills.

93. Freshwater Animals –To help maintain water balance, flatworms have specialized cells called flame cells that remove excess water from body fluids. –The excess water travels through excretory tubules and leaves through pores in the skin.

94. Saltwater Animals –Marine invertebrates and vertebrates typically release ammonia by diffusion across their body surfaces or gill membranes. –Many marine invertebrates have body fluids with water concentrations similar to that of the seawater around them. For that reason, these animals have less of a problem with water balance than do freshwater invertebrates.

95. Saltwater Animals –The bodies of some saltwater animals, such as fishes, contain a lower concentration of salt than the water they live in.

96. Saltwater Animals –Saltwater fish lose water through osmosis, and salt diffuses in. –If they didn’t conserve water and eliminate salt, they’d shrivel up like dead leaves.

97. Saltwater Animals –Saltwater fish conserve water by producing very little concentrated urine. –They drink, and they actively pump salt out across their gills.

98. Excretion in Terrestrial Animals – How do land animals remove wastes while conserving water?

99. Excretion in Terrestrial Animals – How do land animals remove wastes while conserving water? – Some terrestrial invertebrates, including annelids and mollusks, produce urine in nephridia. –Other terrestrial invertebrates, such as insects and arachnids, convert ammonia into uric acid. –Mammals and land amphibians convert ammonia into urea, which is excreted in urine. –In most reptiles and birds, ammonia is converted into uric acid.

100. Excretion in Terrestrial Animals –In dry environments, land animals can lose large amounts of water from respiratory membranes that must be kept moist. –In addition, they must eliminate nitrogenous wastes in ways that require disposing of water—even though they may not be able to drink water.

101. Terrestrial Invertebrates –Some terrestrial invertebrates, including annelids and mollusks, produce urine in nephridia. –Nephridia are tubelike excretory structures that filter body fluid. –Body fluid enters the nephridia through openings called nephrostomes and becomes more concentrated as it moves along the tubes. –Urine leaves the body through excretory pores.

102. Terrestrial Invertebrates – Other terrestrial invertebrates, such as insects and arachnids, convert ammonia into uric acid. –Uric acid is absorbed from body fluids by structures called Malpighian tubules, which concentrate the wastes and add them to digestive wastes traveling through the gut. –As water is absorbed from these wastes, they form crystals that form a thick paste, which leaves the body through the anus. –This paste contains little water, so this process minimizes water loss.

103. Terrestrial Vertebrates –Reptiles and birds convert ammonia into uric acid, which is passed through ducts into a cavity that also receives digestive wastes from the gut. –The walls of this cavity absorb water from the wastes, causing the uric acid to separate out as a thick, milky-white paste recognized as “bird droppings.”

104. Terrestrial Vertebrates –In mammals and land amphibians, ammonia is converted into urea, which is excreted in urine by the kidneys.

105. Adaptations to Extreme Environments –The way kidneys operate results in some limitations. –Most vertebrate kidneys cannot excrete concentrated salt. That’s why most vertebrates cannot survive by drinking seawater. All that extra salt would overwhelm the kidneys, and the animal would die of dehydration.

106. Adaptations to Extreme Environments –Some marine reptiles and birds have evolved special adaptations to rid themselves of excess salt. –The petrel, which hunts for fish in the ocean, has special glands in its nostrils that separate salt from the water it swallows and excrete the salt as a thick, sticky fluid.

107. Adaptations to Extreme Environments –The kidneys of kangaroo rats, which live in the desert, produce urine that is 25 times more concentrated than their blood! –In addition, their intestines are so good at absorbing water that their feces are almost dry.