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Chapter 40

Chapter 40. Basic Principles of Animal Form and Function. Overview: Diverse Forms, Common Challenges. Animals inhabit almost every part of the biosphere All animals face a similar set of problems, including how to nourish themselves

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Chapter 40

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  1. Chapter 40 Basic Principles of Animal Form and Function

  2. Overview: Diverse Forms, Common Challenges • Animals inhabit almost every part of the biosphere • All animals face a similar set of problems, including how to nourish themselves • The comparative study of animals reveals that form and function are closely correlated

  3. Anatomy is the study of the structure of an organism • Physiology is the study of the functions an organism performs

  4. Concept 40.1: Physical laws and the environment constrain animal size and shape • Physical laws and the need to exchange materials with the environment place limits on the range of animal forms

  5. Physical Laws and Animal Form • The ability to perform certain actions depends on an animal’s shape and size • Evolutionary convergence reflects different species’ adaptations to a similar environmental challenge Video: Shark Eating Seal Video: Galápagos Sea Lion

  6. LE 40-2 Tuna Shark Penguin Dolphin Seal

  7. Exchange with the Environment • An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings • Exchange occurs as substances dissolved in the aqueous medium diffuse and are transported across the cells’ plasma membranes

  8. A single-celled protist living in water has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm Video: Hydra Eating Daphnia

  9. LE 40-3 Mouth Gastrovascular cavity Diffusion Diffusion Diffusion Two cell layers Single cell

  10. Multicellular organisms with a sac body plan have body walls that are only two cells thick, facilitating diffusion of materials

  11. More complex organisms have highly folded internal surfaces for exchanging materials

  12. LE 40-4 External environment CO2 O2 Food Mouth Animal body Respiratory system Blood 50 µm 0.5 cm A microscopic view of the lung reveals that it is much more spongelike than balloonlike. This construction provides an expansive wet surface for gas exchange with the environment (SEM). Cells Heart Circulatory system 10 µm Nutrients Digestive system Interstitial fluid Excretory system The lining of the small intestine, a digestive organ, is elaborated with fingerlike projections that expand the surface area for nutrient absorption (cross-section, SEM). Inside a kidney is a mass of microscopic tubules that exchange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM). Anus Metabolic waste products (urine) Unabsorbed matter (feces)

  13. Concept 40.2: Animal form and function are correlated at all levels of organization • Most animals are composed of specialized cells organized into tissues that have different functions • Tissues make up organs, which together make up organ systems

  14. Tissue Structure and Function • Different tissues have different structures that are suited to their functions • Tissues are classified into four main categories: epithelial, connective, muscle, and nervous

  15. LE 40-5_1 EPITHELIAL TISSUE Columnar epithelia, which have cells with relatively large cytoplasmic volumes, are often located where secretion or active absorption of substances is an important function. Simple columnar epithelium Stratified columnar epithelium Pseudostratified ciliated columnar epithelium Cuboidal epithelia Stratified squamous epithelia Simple squamous epithelia Basement membrane 40 µm

  16. LE 40-5_2 CONNECTIVE TISSUE 120 µm Chondrocytes Collagenous fiber Loose connective tissue Chondroitin sulfate Elastic fiber 100 µm Cartilage Fibrous connective tissue Adipose tissue Fat droplets Nuclei 150 µm 30 µm Blood Central canal Red blood cells Bone White blood cell Plasma Osteon 700 µm 55 µm

  17. LE 40-5_3 MUSCLE TISSUE 100 µm Multiple nuclei Skeletal muscle Muscle fiber Sarcomere Cardiac muscle 50 µm Intercalated disk Nucleus Nucleus Smooth muscle Muscle fibers 25 µm NERVOUS TISSUE Neuron Process Cell body Nucleus 50 µm

  18. Epithelial Tissue • Epithelial tissue covers the outside of the body and lines the organs and cavities within the body • It contains cells that are closely joined

  19. Connective Tissue • Connective tissue mainly binds and supports other tissues • It contains sparsely packed cells scattered throughout an extracellular matrix

  20. Muscle Tissue • Muscle tissue consists of long cells called muscle fibers, which contract in response to nerve signals • It is divided in the vertebrate body into three types: skeletal, cardiac, and smooth

  21. Nervous Tissue • Nervous tissue senses stimuli and transmits signals throughout the animal

  22. Organs and Organ Systems • In all but the simplest animals, tissues are organized into organs • In some organs, the tissues are arranged in layers

  23. LE 40-6 Lumen of stomach Mucosa: an epithelial layer that lines the lumen Submucosa: a matrix of connective tissue that contains blood vessels and nerves Muscularis: consists mainly of smooth muscle tissue Serosa: a thin layer of connective and epithelial tissue external to the muscularis 0.2 mm

  24. Organ systems carry out the major body functions of most animals

  25. Concept 40.3: Animals use the chemical energy in food to sustain form and function • All organisms require chemical energy for growth, repair, physiological processes, regulation, and reproduction

  26. Bioenergetics • Bioenergetics, the flow of energy through an animal, limits behavior, growth, and reproduction • It determines how much food an animal needs • Studying bioenergetics tells us much about an animal’s adaptations

  27. Energy Sources and Allocation • Animals harvest chemical energy from food • Energy-containing molecules from food are usually used to make ATP, which powers cellular work • After the needs of staying alive are met, remaining food molecules can be used in biosynthesis

  28. LE 40-7 Organic molecules in food External environment Animal body Digestion and absorption Heat Energy lost in feces Nutrient molecules in body cells Energy lost in urine Cellular respiration Carbon skeletons Heat ATP Biosynthesis: growth, storage, and reproduction Cellular work Heat Heat

  29. Quantifying Energy Use • Metabolic rate is the amount of energy an animal uses in a unit of time • One way to measure it is to determine the amount of oxygen consumed or carbon dioxide produced

  30. LE 40-8 This photograph shows a ghost crab in a respirometer. Temperature is held constant in the chamber, with air of known O2 concentration flowing through. The crab’s metabolic rate is calculated from the difference between the amount of O2 entering and the amount of O2 leaving the respirometer. This crab is on a treadmill, running at a constant speed as measurements are made. Similarly, the metabolic rate of a man fitted with a breathing apparatus is being monitored while he exercises on a stationary bike.

  31. Bioenergetic Strategies • An animal’s metabolic rate is closely related to its bioenergetic strategy • Birds and mammals are mainly endothermic: Their bodies are warmed mostly by heat generated by metabolism • Endotherms typically have higher metabolic rates

  32. Amphibians and reptiles other than birds are ectothermic: They gain their heat mostly from external sources • Ectotherms generally have lower metabolic rates

  33. Influences on Metabolic Rate • Metabolic rates are affected by many factors besides whether an animal is an endotherm or ectotherm • Two of these factors are size and activity

  34. Size and Metabolic Rate • Metabolic rate per gram is inversely related to body size among similar animals • Researchers continue to search for the causes of this relationship

  35. Activity and Metabolic Rate • The basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest • The standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest • Activity greatly affects metabolic rate • In general, maximum metabolic rate is inversely related to the duration of the activity

  36. LE 40-9 500 A = 60-kg alligator A H 100 H A A = 60-kg human 50 H 10 Maximum metabolic rate (kcal/min; log scale) H H 5 A 1 A A 0.5 0.1 1 second 1 day 1 week 1 minute 1 hour Time interval Key Existing intracellular ATP ATP from glycolysis ATP from aerobic respiration

  37. Energy Budgets • Different species use energy and materials in food in different ways, depending on their environment • Use of energy is partitioned to BMR (or SMR), activity, homeostasis, growth, and reproduction

  38. LE 40-10 Endotherms Ectotherm 800,000 Reproduction Temperature regulation Basal (standard) metabolism Growth Activity Annual energy expenditure (kcal/yr) 340,000 8,000 4,000 60-kg female human from temperate climate 4-kg male Adélie penguin from Antarctica (brooding) 0.025-kg female deer mouse from temperate North America 4-kg female python from Australia Total annual energy expenditures. The slices of the pie charts indicate energy expenditures for various functions. 438 Human Energy expenditure per unit mass (kcal/kg•day) 233 Python Deer mouse Adélie penguin 36.5 5.5 Energy expenditures per unit mass (kcal/kg•day). Comparing the daily energy expenditures per kg of body weight for the four animals reinforces two important concepts of bioenergetics. First, a small animal, such as a mouse, has a much greater energy demand per kg than does a large animal of the same taxonomic class, such as a human (both mammals). Second, note again that an ectotherm, such as a python, requires much less energy per kg than does an endotherm of equivalent size, such as a penguin.

  39. Concept 40.4: Animals regulate their internal environment within relatively narrow limits • The internal environment of vertebrates is called the interstitial fluid and is very different from the external environment • Homeostasis is a balance between external changes and the animal’s internal control mechanisms that oppose the changes

  40. Regulating and Conforming • Regulating and conforming are two extremes in how animals cope with environmental fluctuations • A regulator uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation • A conformer allows its internal condition to vary with certain external changes

  41. Mechanisms of Homeostasis • Mechanisms of homeostasis moderate changes in the internal environment • A homeostatic control system has three functional components: a receptor, a control center, and an effector Animation: Negative Feedback Animation: Positive Feedback

  42. LE 40-11 Response No heat produced Heater turned off Room temperature decreases Set point Too hot Set point Set point Too cold Control center: thermostat Room temperature increases Heater turned on Response Heat produced

  43. Most homeostatic control systems function by negative feedback, where buildup of the end product shuts the system off • In positive feedback, a change in a variable triggers mechanisms that amplify rather than reverse the change

  44. Concept 40.5: Thermoregulation contributes to homeostasis and involves anatomy, physiology, and behavior • Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range

  45. Ectotherms and Endotherms • Ectotherms include most invertebrates, fishes, amphibians, and non-bird reptiles • Endotherms include birds and mammals • In general, ectotherms tolerate greater variation in internal temperature than endotherms

  46. LE 40-12 40 River otter (endotherm) 30 Body temperature (°C) 20 Largemouth bass (ectotherm) 10 0 10 20 40 30 Ambient (environmental) temperature (°C)

  47. Endothermy is more energetically expensive than ectothermy • It buffers the animal’s internal temperatures against external fluctuations • It also enables the animal to maintain a high level of aerobic metabolism

  48. Modes of Heat Exchange • Organisms exchange heat by four physical processes: conduction, convection, radiation, and evaporation

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