Basic Principles of Animal Form and Function

Basic Principles of Animal Form and Function Chapter 40 P. Biology Rick L. Knowles Liberty Senior High School

Figure 40.1 • The comparative study of animals • Reveals that form and function are closely correlated • Natural selection can fit structure, anatomy, to function, physiology

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 certain limits on the range of animal forms Could they ever exist?

Convergent Evolution • Reflects different species’ independent adaptation to a similar environmental challenge (a) Tuna (b) Shark (c) Penguin (d) Dolphin Figure 40.2a–e (e) Seal

Exchange with the Environment • An animal’s size and shape • Have a direct effect on how the animal exchanges energy and materials with its surroundings • Exchange with the environment occurs as substances dissolved in the aqueous medium • Diffuse and are transported across the cells’ plasma membranes

Diffusion (a) Single cell • A single-celled protist living in water • Has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm Figure 40.3a

Multicellular organisms with a sac body plan • Have body walls that are only two cells thick, facilitating diffusion of materials Mouth Gastrovascular cavity Diffusion Diffusion (b) Two cell layers Figure 40.3b

External environment Food CO2 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 Interstitial fluid Digestive system 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 exhange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM). Anus Unabsorbed matter (feces) Metabolic waste products (urine) Figure 40.4

Bioenergetics • The flow of energy through an animal, its bioenergetics • Ultimately limits the animal’s behavior, growth, and reproduction • Determines how much food it needs • Studying an animal’s bioenergetics • Tells us a great deal about the animal’s adaptations

Energy Sources and Allocation • Animals harvest chemical energy • From the food they eat • Once food has been digested, the energy-containing molecules • Are usually used to make ATP, which powers cellular work

After the energetic needs of staying alive are met • Any remaining molecules from food can be used in biosynthesis 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 Figure 40.7 Heat

Quantifying Energy Use • An animal’s metabolic rate • Sum of all the energy-requiring biochemical reactions occurring over a given time. • Measured in calories (cal) or kilocalories (kcal). • 1.0 kcal = 1, 000 cal. • 1.0 Calorie (capital C) = 1 kcal = 1, 000 calories • Can be measured in a variety of ways: • Most energy from cell respiration becomes heat, can use a calorimeter to measure heat loss . • Measure the amount of oxygen consumed or carbon dioxide produced. • Rate of food consumption and energy content of food (4- 5 kcal/g of protein and carb and 9 kcal/g fat), but not all the energy in food is usable (feces and urine).

(a) This photograph shows a ghost crab in arespirometer. Temperature is held constant in thechamber, with air of known O2 concentration flow-ing through. The crab’s metabolic rate is calculatedfrom the difference between the amount of O2entering and the amount of O2 leaving therespirometer. This crab is on a treadmill, runningat a constant speed as measurements are made. (b) Similarly, the metabolic rate of a manfitted with a breathing apparatus isbeing monitored while he works outon a stationary bike. Figure 40.8a, b • One way to measure metabolic rate • Is to determine the amount of oxygen consumed or carbon dioxide produced by an organism

Bioenergetic Strategies • An animal’s metabolic rate is related to its bioenergetic strategy. • The type of strategy dictates rate of metabolism. • There are TWO basic types

Endothermy • Animal bodies are warmed mostly by heat generated from metabolism. • Maintain a narrow range of body temp. • High energy strategy for long-duration activity over a wide range of environmental temps. • Requires more daily calories. • Ex. Most birds and mammals

Ectothermy • Animal bodies gain body heat mostly from external sources. • Requires less energy. • Lower metabolic rates. • Ex. Most fish, amphibians, reptiles

Ectotherm vs. Endotherm • Ectotherms regulate body temp. through behavior – basking or hiding in burrows – to regulate body temp. • Some ectotherms have a narrow range of body temps. – marine fish in waters that don’t vary much. • Some endotherms experience wide variation in body temps. – sloth has +/- 10 °C • Not mutually exclusive – endothermic birds may sun themselves to warm up or digest food. • Homeothermic (stable) vs. Poikilothermic (variable)

40 River otter (endotherm) 30 Body temperature (°C) 20 Largemouth bass (ectotherm) 10 0 10 20 30 40 Ambient (environmental) temperature (°C) • In general, ectotherms • Tolerate greater variation in internal temperature than endotherms Figure 40.12

Factors that Affect Metabolic Rate • Ectothermic vs. Endothermic • Body Size • Metabolic rate is inversely related to mass. 1.0 g of mouse requires 20 X calories than 1.0 g of elephant. • Higher metabolic rate of smaller animals means higher 02 demand (cellular respiration rate), higher breathing rate, heart rate (pulse), and it must eat more food per unit body mass. • Why? Higher S. A to Vol. ratio; greater loss of heat in smaller animals (endothermic).

Factors that Affect Metabolic Rate • Activity Level • Minimum metabolic rate required by a nongrowingendotherm at rest , with an empty stomach to power cell maintenance, breathing, and heartbeat – Basal Metabolic Rate (BMR). BMR for Human Males = 1, 800 kcal/day BMR for Human Females = 1,500 kcal/day • In an ectotherm, body temp. changes with env. temp.; must determine metabolic rate of a resting, fasting, nonstressedectotherm at a given temp. – Standard Metabolic Rate (SMR). • Both endo- and ectotherms, max. metabolic rates (highest rated of ATP use) = peak activity.

500 A = 60-kg alligator A H 100 H A H = 60-kg human 50 H Maximum metabolic rate (kcal/min; log scale) 10 H H 5 A 1 A A 0.5 0.1 1 minute 1 second 1 hour 1 day 1 week Time interval Key Existing intracellular ATP ATP from glycolysis ATP from aerobic respiration Activity and Metabolic Rate In general, an animal’s maximum possible metabolic rate is inversely related to the duration of the activity. Endotherm Respiration Rate is 20 X an Ectotherm, causes less endurance Figure 40.9

Other Factors Affecting Metabolic Rate • Age • Gender • Size • Body and Environmental Temps. • Quality/Quantity of Food • Activity Level • Oxygen Availability/Delivery Efficiency • Hormones • Time of Day (nocturnal vs. diurnal animals)

Energy Budgets • Different species use energy in food in different ways, depending on environment, size, behavior, and endo vs. ectothermy. • Some animals have determinant growth – maximum size and stop growing at maturity. Ex. most mammals and birds. Use less energy for growth as adults. • Other species have indeterminant growth – continue to grow throughout their life as long as nutrition and temp are appropriate. Ex. fish, reptiles. Use some energy for growth as adults.

Endotherms Ectotherm Reproduction 800,000 Temperature regulation costs Basal metabolic rate Growth 340,000 Activity costs Annual energy expenditure (kcal/yr) 8,000 4,000 0.025-kg female deer mouse from temperate North America 4-kg male Adélie penguin from Antarctica (brooding) 60-kg female human from temperate climate 4-kg female python from Australia (a) Total annual energy expenditures 438 Human 233 Energy expenditure per unit mass (kcal/kg•day) Python Deer mouse Adélie penguin 36.5 5.5 Energy expenditures per unit mass (kcal/kg•day) (b)

Advantages of Endothermy Higher BMRs to generate heat require: • More efficient circulatory and respiratory systems  allows for endurance activities; higher levels of aerobic metabolism (few ectotherms migrate). • Wide range of habitats (arctic, etc.). • Have mechanisms of cooling (sweating, panting, etc.) that allow them to tolerate extremes in temps. better. • Disadvantages: Must consume more calories/day.

Radiation is the emission of electromagnetic waves by all objects warmer than absolute zero. Radiation can transfer heat between objects that are not in direct contact, as when a lizard absorbs heat radiating from the sun. Evaporation is the removal of heat from the surface of a liquid that is losing some of its molecules as gas. Evaporation of water from a lizard’s moist surfaces that are exposed to the environment has a strong cooling effect. Conduction is the direct transfer of thermal motion (heat) between molecules of objects in direct contact with each other, as when a lizard sits on a hot rock. Convection is the transfer of heat by the movement of air or liquid past a surface, as when a breeze contributes to heat loss from a lizard’s dry skin, or blood moves heat from the body core to the extremities. Modes of Heat Exchange • Organisms exchange heat by four physical processes Figure 40.13

Balancing Heat Loss and Gain • Thermoregulation – requires the management of the heat budget (heat loss = heat gain). • All endotherms and some ectotherms can thermoregulate. • Five Categories of Adaptation for this:

1. Insulation • Insulation, which is a major thermoregulatory adaptation in mammals and birds • Reduces the flow of heat between an animal and its environment • May include feathers, fur, or blubber (extra adipose)

In mammals, the integumentary system • Acts as insulating material Hair Epidermis Sweat pore Muscle Dermis Nerve Sweat gland Hypodermis Adipose tissue Blood vessels Oil gland Figure 40.14 Hair follicle

2. Circulatory Adaptations • Many endotherms and some ectotherms • Can alter the amount of blood flowing between the body core and the skin • In vasodilation: • Increase in diameter of superficial blood vessels, triggered by nerve impulses that relax the smooth muscles. • Blood flow in the skin increases, facilitating heat loss • In vasoconstriction: • Decrease in diameter of superficial blood vessels. • Blood flow in the skin decreases, lowering heat loss

Pacific bottlenose dolphin Arteries carrying warm blood down the legs of a goose or the flippers of a dolphin are in close contact with veins conveying cool blood in the opposite direction, back toward the trunk of the body. This arrangement facilitates heat transfer from arteries to veins (black arrows) along the entire length of the blood vessels. 1 Canada goose Blood flow 1 Artery Vein Vein Near the end of the leg or flipper, where arterial blood has been cooled to far below the animal’s core temperature, the artery can still transfer heat to the even colder blood of an adjacent vein. The venous blood continues to absorb heat as it passes warmer and warmer arterial blood traveling in the opposite direction. 2 Artery 3 35°C 33° 3 30º 27º 20º 18º 2 10º 9º In the flippers of a dolphin, each artery is surrounded by several veins in a countercurrent arrangement, allowing efficient heat exchange between arterial and venous blood. As the venous blood approaches the center of the body, it is almost as warm as the body core, minimizing the heat lost as a result of supplying blood to body parts immersed in cold water. 2 3 • Many marine mammals and birds • Have arrangements of blood vessels called countercurrent heat exchangers that are important for reducing heat loss 3 1 Figure 40.15

21º 23º 25º 27º 29º 31º Body cavity Skin Artery Vein Blood vessels in gills Capillary network within muscle Heart Artery and vein under the skin Dorsal aorta • Some specialized bony fishes and sharks • Also possess countercurrent heat exchangers (a)Bluefin tuna. Unlike most fishes, the bluefin tuna maintains temperatures in its main swimming muscles that are much higher than the surrounding water (colors indicate swimming muscles cut in transverse section). These temperatures were recorded for a tuna in 19°C water. (b) Great white shark. Like the bluefin tuna, the great white shark has a countercurrent heat exchanger in its swimming muscles that reduces the loss of metabolic heat. All bony fishes and sharks lose heat to the surrounding water when their blood passes through the gills. However, endothermic sharks have a small dorsal aorta, and as a result, relatively little cold blood from the gills goes directly to the core of the body. Instead, most of the blood leaving the gills is conveyed via large arteries just under the skin, keeping cool blood away from the body core. As shown in the enlargement, small arteries carrying cool blood inward from the large arteries under the skin are paralleled by small veins carrying warm blood outward from the inner body. This countercurrent flow retains heat in the muscles. Figure 40.16a, b

Fig. 40.16

Many endothermic insects • Have countercurrent heat exchangers that help maintain a high temperature in the thorax – where flight muscles are located. Figure 40.17

3. Cooling by Evaporative Heat Loss • Many types of mammals and birds: • Lose heat through the evaporation of water in sweat. • Use panting to cool their bodies (floor of the mouth of birds is rich in capillaries for heat loss when they pant). • Water is 50 -100X more efficient at transferring heat than air. Fig. 40.18

4. Behavioral Responses • Both endotherms and ectotherms • Use a variety of behavioral responses to control body temperature (Ex. moving in and out of sun) • Some terrestrial invertebrates • Have certain postures that enable them to minimize or maximize their absorption of heat from the sun Figure 40.19

5. Adjusting Metabolic Heat Production • Since endotherms are often warmer than surroundings, must counteract heat loss. • May shiver (involuntary muscle contraction) to warm themselves. • Some mammals use hormones to cause mitochondria to increase activity and produce heat rather than ATP – nonshiveringthermogenesis (NST). • Hibernating mammals and human babies have brown fat –used to rapidly produce heat. (brown due to rich blood supply). • Some reptiles – female pythons – coil around eggs and shiver to warm eggs.

PREFLIGHT WARMUP PREFLIGHT FLIGHT 40 Thorax 35 Temperature (°C) 30 Abdomen 25 0 2 4 Time from onset of warmup (min) • Many species of flying insects • Use shivering to warm up before taking flight Figure 40.20

Fig. 40.21

Adjustment to Temp. Changes at Cellular Level • If mammals cells in vitro are grown at higher temperature, there is an increase in heat-shock proteins – stabilize proteins from being denatured. • Cells may produce enzymes with different optimum temp. functions. • Some arctic species of fish and amphibians produce cryoprotectants –prevent ice formation inside tissues and cells.

Torpor and Energy Conservation • Torpor: • Is an adaptation that enables animals to save energy while avoiding difficult and dangerous conditions. • Is a physiological state in which activity is low and metabolism decreases.

Hibernation is long-term torpor • That is an adaptation to winter cold and food scarcity during which the animal’s body temperature declines Additional metabolism that would be necessary to stay active in winter 200 Actual metabolism 100 Figure 40.22 Metabolic rate (kcal per day) 0 Arousals 35 Body temperature 30 25 20 Temperature (°C) 15 10 5 0 Outside temperature Burrow temperature -5 -10 -15 June August October December February April

Estivation, or summer torpor: • Enables animals to survive long periods of high temperatures and scarce water supplies • Many reptiles estivate in the summer months. • Daily torpor: • Is exhibited by many small mammals and birds and seems to be adapted to their feeding patterns. • Many nocturnal animals (bats and shrews) feed at night and then go into torpor during daylight hours.

Basic Principles of Animal Form and Function