Animal Form and Function Ch 40 Animal Form and Function

Diverse Forms, Common Challenges Anatomy is the study of the biological form of an organism Physiology is the study of biological functions an organism performs The comparative study of animals reveals that form and function are closely related.

Animal form and function are correlated at all levels of organization Evolution of Animal Size and Shape Different body plans have arisen during the course of evolution but these variations fall within certain bounds Physical laws constrain strength, diffusion, movement, and heat exchange Ex. As animals increase in size, their skeletons must be proportionately larger to support their mass Evolutionary convergence reflects different species’ adaptations to a similar environmental challenge

Example: Seal, Penguin, Tuna Water is 1000x denser than air and also more viscous. Any bump on animal may cause drag and slow them down. Natural selection often results in similar adaptations when diverse organisms face the same environmental challenges (convergent evolution)

Exchange with the Environment An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings (may limit body plan) Animal cells must have access to aqueous medium (substances dissolved diffuse and are transported across the cells’ plasma membranes) Interstitial fluid

Exchange with the Environment A single-celled protist living in water has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm Two celled sacs and flat shape maximize exposure to surrounding medium (facilitate diffusion)

Mouth Gastrovascular cavity Diffusion Diffusion Diffusion Single cell Two cell layers

Exchange with the Environment Complex body plans have highly folded internal membrane to maximize surface area.

External environment CO2 Food O2 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 Nutrients Circulatory system 10 µm 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). Anus Inside a kidney is a mass of microscopic tubules that exchange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM). Unabsorbed matter (feces) Metabolic waste products (urine)

Benefits of complex body plans over simple ones External skeleton protects against predators Sensory organs can provide detailed information about animal’s surroundings Internal digestive organs can break food down gradually controlling release of stored energy Specialized filtration systems can adjust the composition of the internal fluid that baths animal cells helps maintain stable environment in a changeable external environment Despite the challenges of exchange with the environment, complex body plans have distinct benefits over simple ones. Complex body plan is especially advantageous for land animals where the environment is highly variable.

Hierarchical Organization of Body Plans Most animals are composed of specialized cells organized into tissues that have different functions Tissues make up organs, which together make up organ systems Some organs, such as the pancreas, belong to more than one organ system Pancreas – digestive system and endocrine system

Table 40.1 Organ Systems in Mammals 12

Exploring Structure and Function in Animal Tissues Different tissues have different structures that are suited to their functions Tissues are classified into four main categories: epithelial, connective, muscle, and nervous

Epithelial Tissues Sheets of cells Cover outside of body and line organs and cavities. Closely packed (tight junctions) Barrier Polar: apical faces out, basal faces in.

Epithelial Tissue Stratified squamous epithelium Pseudostratified Figure 40.5aa Epithelial Tissue Stratified squamous epithelium The arrangement of epithelial cells may be simple (single cell layer), stratified (multiple tiers of cells), or pseudostratified (a single layer of cells of varying length) Pseudostratified columnar epithelium Cuboidal epithelium Simple columnar epithelium Simple squamous epithelium 15

Connective Tissues Sparse cells scattered throughout extracellular matrix. Holds tissues and organs in place. Matrix + Fibroblasts + macrophages Fibroblasts: secrete fiber proteins Macrophages: phagocytosis.

Connective Tissue Loose connective tissue Blood Cartilage Figure 40.5ba Connective Tissue Loose connective tissue Blood Collagenous fiber Plasma White blood cells 120 m 55 m Elastic fiber Cartilage Red blood cells Fibrous connective tissue Chondrocytes 100 m Figure 40.5 Exploring: Structure and Function in Animal Tissues 30 m Chondroitin sulfate Nuclei Bone Adipose tissue Central canal Fat droplets 700 m 150 m Osteon 17

Muscle Tissues Responsible for movement Consist of filaments (actin and myosin) Three types: Skeletal (voluntary) Smooth (involuntary) Cardiac (interconnected to relay signals)

Muscle Tissue Skeletal muscle Smooth muscle Cardiac muscle Nuclei Figure 40.5ca Muscle Tissue Skeletal muscle Nuclei Muscle fiber Sarcomere 100 m Smooth muscle Cardiac muscle Skeletal muscle, or striated muscle, is responsible for voluntary movement Smooth muscle is responsible for involuntary body activities Cardiac muscle is responsible for contraction of the heart Nucleus Muscle fibers 25 m Nucleus Intercalated disk 50 m 19

Nervous Tissue Neurons Glia Glia Neuron: Dendrites Cell body Axons of Figure 40.5da Nervous Tissue Neurons Glia Glia 15 m Neuron: Dendrites Cell body Axons of neurons Axon Blood vessel 40 m Neurons, or nerve cells, that transmit nerve impulses Glial cells, or glia, that help nourish, insulate, and replenish neurons (Fluorescent LM) (Confocal LM) 20

Nervous Tissue Receipt, processing, and transmission of info Neurons + Glia Neurons: transmit nerve impulses Glia: support cells

Coordination and Control Animal tissues, organs, organ systems must act in concert together. Coordinating activity across an animals body in this way requires communication (BIG IDEA!) between different body locations.

Two major systems for coordinating and controlling responses to stimuli Endocrine (good for gradual changes such as growth, direction, etc.) Releases hormones via the blood stream Only certain cells are responsive to each hormone Hormones tale second to act but can have long-lasting effects Nervous (good for rapid responses to environment) Use cellular circuits involving electrical and chemical signals to send information to specific locations. The information conveyed depends on a signal’s pathway, not the type of signal Nerve signal transmission is very fast Nerve impulses can be received by neurons, muscle cells, endocrine cells, and exocrine cells

Response limited to cells that have the receptor for that signal. Figure 40.6 Response limited to cells that have the receptor for that signal. Figure 40.6 Signaling in the endocrine and nervous systems Conveys information along a pathway. 24

Feedback control maintains the internal environment in many animals Animals manage their internal environment by regulating or conforming to the external environment

Regulating and Conforming 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 Animals may regulate some environmental variables while conforming to others

Figure 40.7 Figure 40.7 The relationship between body and environmental temperatures in an aquatic temperature regulator and an aquatic temperature conformer. 27

Homeostasis Organisms use homeostasis to maintain a “steady state” or internal balance regardless of external environment In humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level

Mechanisms of Homeostasis Mechanisms of homeostasis moderate changes in the internal environment For a given variable, fluctuations above or below a set point serve as a stimulus; these are detected by a sensor and trigger a response. (The response returns the variable to the set point.) Find videos of negative feedback animation

Figure 40.8 Figure 40.8 A nonliving example of temperature regulation: control of room temperature. 30

Feedback Control in Homeostasis The dynamic equilibrium of homeostasis is maintained by negative feedback, which helps to return a variable to a normal range Most homeostatic control systems function by negative feedback, where buildup of the end product shuts the system off Positive feedback amplifies a stimulus and does not usually contribute to homeostasis in animals (does not reverse the change but drives a process towards completion, i.e. childbirth/uterus contractions)

Alterations in Homeostasis Set points and normal ranges can change with age or show cyclic variation In animals and plants, a circadian rhythm governs physiological changes that occur roughly every 24 hours

Figure 40.9 Human circadian rhythm. 33

Figure 40.9 Human circadian rhythm. 34

Homeostasis can adjust to changes in external environment, a process called acclimatization Acclimatization is a temporary change during an animal’s lifetime, not be confused with adaptation. Ex. Elk moves us into mountains from sea level. Less oxygen. Breathing deepens. More CO2 lost through exhalation therefore raising pH above norm. Over days kidney function excretes more alkaline urine. Blood returns to normal pH. Acclimatization is a temporary change during an animal’s lifetime, show not be confused with adaptation.

40.3: Homeostatic processes for thermoregulation involve form, function, and behavior Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range

Endothermy and Ectothermy Endothermic animals generate heat by metabolism; birds and mammals are endotherms Ectothermic animals gain heat from external sources; ectotherms include most invertebrates, fishes, amphibians, and nonavian reptiles

Endothermy is more energetically expensive than ectothermy In general, ectotherms tolerate greater variation in internal temperature, while endotherms are active at a greater range of external temperatures Endothermy is more energetically expensive than ectothermy Ecototherms need less food than endotherms of equivalent size – an advantage if food supplies are limited 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

Figure 40.10 Endothermy and ectothermy. 39

Variation in Body Temperature The body temperature of a poi kilo therm varies with its environment The body temperature of a homeotherm is relatively constant The relationship between heat source and body temperature is not fixed (that is, not all poikilotherms are ectotherms)

Balancing Heat Loss and Gain Organisms exchange heat by four physical processes: radiation, evaporation, convection, and conduction

Five adaptations help animals thermoregulate: Heat regulation in mammals often involves the integumentary system: skin, hair, and nails Five adaptations help animals thermoregulate: Insulation Circulatory adaptations Cooling by evaporative heat loss Behavioral responses Adjusting metabolic heat production

Insulation Insulation is a major thermoregulatory adaptation in mammals and birds Skin, feathers, fur, and blubber reduce heat flow between an animal and its environment Insulation is especially important in marine mammals such as whales and walruses

Circulatory Adaptations Regulation of blood flow near the body surface significantly affects thermoregulation Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin In vasodilation, blood flow in the skin increases, facilitating heat loss In vasoconstriction, blood flow in the skin decreases, lowering heat loss

The arrangement of blood vessels in many marine mammals and birds allows for countercurrent exchange Countercurrent heat exchangers transfer heat between fluids flowing in opposite directions and reduce heat loss Arteries and veins flow in opposite directions. As warm blood moves from the body core in arteries, it transfers hear to the colder blood returning from the extremities in the veins.

Figure 40.12 Countercurrent heat exchangers. Heat transfer is facilitated between the warm artery and the cool vein. This allows the animal to minimize heat loss. As the blood in the veins approaches the center of the body, it is almost as warm as the core. 46

Cooling by Evaporative Heat Loss Many types of animals lose heat through evaporation of water from their skin Panting increases the cooling effect in birds and many mammals Sweating or bathing moistens the skin, helping to cool an animal down

Behavioral Responses Both endotherms and ectotherms use behavioral responses to control body temperature Some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat

Both endotherms and ectotherms use behavioral responses to control body temperature Some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat Figure 40.13 Thermoregulatory behavior in a dragonfly.

Adjusting Metabolic Heat Production Thermogenesis is the adjustment of metabolic heat production to maintain body temperature Increased by muscle activity (moving or shivering) Nonshivering thermogenesis takes place when hormones cause mitochondria to increase their metabolic activity (can produce heat instead of ATP)

Results: The python’s oxygen consumption increased when the temperature of the chamber decreased. Her oxygen consumption also increased with the rate of muscle contraction. Figure 40.14 Inquiry: How does a Burmese python generate heat while incubating eggs? Figure 40.14 Conclusion: Because oxygen consumption, which generates heat through cellular respiration, increased linearly with the rate of muscle contraction, the researchers concluded that the muscle contractions, a form of shivering, were the source of the Burmese python’s elevated body temperature. 51

Hawkmoth uses a shivering-like mechanism for preflight warm up. Figure 40.15 Figure 40.15 Preflight warm-up in the hawkmoth. Uses a shivering-like mechanism for preflight warm up Hawkmoth uses a shivering-like mechanism for preflight warm up. 52

Acclimatization in Thermoregulation Birds and mammals can vary their insulation to acclimatize to seasonal temperature changes When temperatures are subzero, some ectotherms produce “antifreeze” compounds to prevent ice formation in their cells

Physiological Thermostats and Fever Thermoregulation is controlled by a region of the brain called the hypothalamus Group of nerve cells within hypothalamus functions as a thermostat. The hypothalamus triggers heat loss or heat generating mechanisms Fever is the result of a change to the set point for a biological thermostat Hypothalmus, the brain region that also control circadian clock.

Figure 40.16 Figure 40.16 The thermostatic function of the hypothalamus in human thermoregulation. 55

Concept 40.4: Energy requirements are related to animal size, activity, and environment Bioenergetics is the overall flow and transformation of energy in an animal It determines how much food an animal needs and it relates to an animals size, activity, and environment

Energy Allocation and Use 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 Biosynthesis includes body growth and repair, synthesis of storage material such as fat, and production of gametes

Figure 40.17 Bioenergetics of an animal: an overview. 58

Quantifying Energy Use Metabolic rate is the amount of energy an animal uses in a unit of time Metabolic rate can be determined by An animal’s heat loss The amount of oxygen consumed or carbon dioxide produced

Figure 40.18 Figure 40.18 Measuring the rate of oxygen consumption by a swimming shark. 60

Minimum Metabolic Rate and Thermoregulation Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a “comfortable” temperature Standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest at a specific temperature Both rates assume a nongrowing, fasting, and nonstressed animal Ectotherms have much lower metabolic rates than endotherms of a comparable size

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

Size and Metabolic Rate Metabolic rate is proportional to body mass to the power of three quarters (m3/4) Smaller animals have higher metabolic rates per gram than larger animals The higher metabolic rate of smaller animals leads to a higher oxygen delivery rate, breathing rate, heart rate, and greater (relative) blood volume, compared with a larger animal

Figure 40.19 The relationship of metabolic rate to body size. 64

Figure 40.19 The relationship of metabolic rate to body size. Figure 40.19a Figure 40.19 The relationship of metabolic rate to body size. 65

Figure 40.19 The relationship of metabolic rate to body size. Figure 40.19b Figure 40.19 The relationship of metabolic rate to body size. 66

Activity and Metabolic Rate Activity greatly affects metabolic rate for endotherms and ectotherms In general, the maximum metabolic rate an animal can sustain is inversely related to the duration of the activity

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, thermoregulation, growth, and reproduction

Figure 40.20 Energy budgets for four animals. 69

Figure 40.20 Energy budgets for four animals. Figure 40.20a Figure 40.20 Energy budgets for four animals. 70

Figure 40.20 Energy budgets for four animals. Figure 40.20b Figure 40.20 Energy budgets for four animals. 71

Torpor and Energy Conservation Torpor is a physiological state in which activity is low and metabolism decreases Torpor enables animals to save energy while avoiding difficult and dangerous conditions Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity Small mammals an birds exhibit a daily torpor that seems to be adapted to feeding patterns. EX. Some bats feed at night and go into torpor in daylight Chickadees and hummingbirds feed during the day and often go into torpor on cold nights. The body temp of chickadees drops as much as 10 degrees Celcius (18F) at night. Hummingbirds can fall 25C (45F) or more.

Figure 40.21 Figure 40.21 Inquiry: What happens to the circadian clock during hibernation? 73

Summer torpor, called estivation, enables animals to survive long periods of high temperatures and scarce water Daily torpor is exhibited by many small mammals and birds and seems adapted to feeding patterns

Figure 40.UN01 Summary figure, Concept 40.2 75

Figure 40.UN02 Figure 40.UN02 Appendix A: answer to Test Your Understanding, question 8 76

Animations and Videos Bozeman – Thermoregulation Bozeman - Anatomy and Physiology Bozeman - Organ Systems Chapter Quiz Questions – 1 Chapter Quiz Questions – 2