Basic Principles of Animal Form and Function

Chapter 40 A. P. Biology

Rick L. KnowlesLiberty Senior High School

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

function, physiology

Figure 40.1

• 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

Figure 40.2a–e

(a) Tuna

(b) Shark

(c) Penguin

(d) Dolphin

(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

• 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

Diffusion

(a) Single cell

• Multicellular organisms with a sac body plan– Have body walls that are only two cells thick, facilitating

diffusion of materials

Figure 40.3b

Mouth

Gastrovascularcavity

Diffusion

Diffusion

(b) Two cell layers

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External environment

Food CO2 O2Mouth

Animalbody

Respiratorysystem

Circulatorysystem

Nutrients

Excretorysystem

Digestivesystem

Heart

Blood

Cells

Interstitialfluid

Anus

Unabsorbedmatter (feces)

Metabolic wasteproducts (urine)

The lining of the small intestine, a diges-tive organ, is elaborated with fingerlikeprojections that expand the surface areafor nutrient absorption (cross-section, SEM).

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).

Inside a kidney is a mass of microscopic tubules that exhange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM).

0.5 cm

10 µm

50 µ

m

Figure 40.4

• 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

Bioenergetics

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

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• After the energetic needs of staying alive are met

– Any remaining molecules from food can be used in biosynthesis

Figure 40.7

Organic moleculesin food

Digestion andabsorption

Nutrient moleculesin body cells

Cellularrespiration

Biosynthesis:growth,

storage, andreproduction

Cellularwork

Heat

Energylost infeces

Energylost inurine

Heat

Heat

Externalenvironment

Animalbody

Heat

Carbonskeletons

ATP

• 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:

a. Most energy from cell respiration becomes heat, can use a calorimeter to measure heat loss .

b. Measure the amount of oxygen consumed or carbon dioxide produced.

c. 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).

Quantifying Energy Use

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• One way to measure metabolic rate

– Is to determine the amount of oxygen consumed or carbon dioxide produced by an organism

Figure 40.8a, b

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 O2

entering and the amount of O2 leaving therespirometer. This crab is on a treadmill, runningat a constant speed as measurements are made.

(a)

(b) Similarly, the metabolic rate of a manfitted with a breathing apparatus isbeing monitored while he works outon a stationary bike.

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)

• In general, ectotherms– Tolerate greater variation in internal temperature than

endotherms

Figure 40.12

River otter (endotherm)

Largemouth bass (ectotherm)

Ambient (environmental) temperature (°C)

Body

tem

pera

ture

(°C)

40

30

20

10

10 20 30 400

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).

• Activity Level– Minimum metabolic rate required by a nongrowing

endotherm at rest , with an empty stomach to power cell maintenance, breathing, and heartbeat – Basal Metabolic Rate (BMR).

BMR for Human Males = 1, 800 kcal/dayBMR for Human Females = 1,500 kcal/day– In an ectotherm, body temp. changes with env. temp.;

must determine metabolic rate of a resting, fasting, nonstressed ectotherm at a given temp. – Standard Metabolic Rate (SMR).

• Both endo- and ectotherms, max. metabolic rates (highest rated of ATP use) = peak activity.

Factors that Affect Metabolic Rate

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In general, an animal’s maximum possible metabolic rate is inversely related to the duration of the activity.

Figure 40.9

Max

imum

met

abol

ic r

ate

(kca

l/min

; log

sca

le)

500

100

50

10

5

1

0.5

0.1

A H

AH

A

AA

HH

H

A = 60-kg alligator

H = 60-kg human

1second

1minute

1hour

Time interval

1day

1week

Key

Existing intracellular ATP

ATP from glycolysis

ATP from aerobic respiration

Activity and Metabolic Rate

Endotherm Respiration Rate is 20 X an Ectotherm, causes less endurance

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

Annu

al e

nerg

y ex

pend

iture

(kca

l/yr

)

800,000

Basalmetabolicrate

Reproduction

Temperatureregulation costs

Growth

Activitycosts

60-kg female humanfrom temperate climate

Total annual energy expenditures (a)

340,000

4-kg male Adélie penguinfrom Antarctica (brooding)

4,000

0.025-kg female deer mousefrom temperateNorth America

8,000

4-kg female pythonfrom Australia

Ener

gy e

xpen

ditu

re p

er u

nit m

ass

(kca

l/kg

•day

)

438

Deer mouse

233

Adélie penguin

36.5

Human

5.5

Python

Energy expenditures per unit mass (kcal/kg•day)(b)

Advantages of EndothermyHigher 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.

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Modes of Heat Exchange

• Organisms exchange heat by four physical processes

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 aliquid 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.

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.

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.

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)

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Hair

Sweatpore

Muscle

Nerve

Sweatgland

Oil glandHair follicle

Blood vessels

Adipose tissue

Hypodermis

Dermis

Epidermis

• In mammals, the integumentary system

– Acts as insulating material

Figure 40.14

• 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

2. Circulatory Adaptations

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• Many marine mammals and birds

– Have arrangements of blood vessels called countercurrent heat exchangers that are important for reducing heat loss

In the flippers of a dolphin, each artery issurrounded by several veins in acountercurrent arrangement, allowingefficient heat exchange between arterialand venous blood.

Canadagoose

Artery Vein

35°C

Blood flow

Vein

Artery

30º

20º

10º

33°

27º

18º

9º

Pacific bottlenose dolphin

2

1

3

2

3

Arteries carrying warm blood down thelegs of a goose or the flippers of a dolphinare in close contact with veins conveyingcool blood in the opposite direction, backtoward the trunk of the body. Thisarrangement facilitates heat transferfrom arteries to veins (blackarrows) along the entire lengthof the blood vessels.

1

Near the end of the leg or flipper, wherearterial blood has been cooled to far below the animal’s core temperature, the artery can still transfer heat to the even colderblood of an adjacent vein. The venous bloodcontinues to absorb heat as it passes warmer and warmer arterial blood traveling in the opposite direction.

2

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 partsimmersed in cold water.

3

Figure 40.15

1 3

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• Some specialized bony fishes and sharks

– Also possess countercurrent heat exchangers

Figure 40.16a, b

21º25º 23º

27º

29º31º

Body cavity

Skin

Artery

Vein

Capillarynetwork withinmuscle

Dorsal aortaArtery andvein underthe skin

Heart

Bloodvesselsin gills

(a) Bluefin tuna. Unlike most fishes, the bluefin tuna maintainstemperatures in its main swimming muscles that are much higherthan the surrounding water (colors indicate swimming muscles cutin transverse section). These temperatures were recorded for a tunain 19°C water.

(b) Great white shark. Like the bluefin tuna, the great white sharkhas a countercurrent heat exchanger in its swimming muscles thatreduces the loss of metabolic heat. All bony fishes and sharks loseheat to the surrounding water when their blood passes through thegills. 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 gillsis conveyed via large arteries just under the skin, keeping cool bloodaway from the body core. As shown in the enlargement, smallarteries carrying cool blood inward from the large arteries under theskin are paralleled by small veins carrying warm blood outward fromthe inner body. This countercurrent flow retains heat in the muscles.

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

• Both endotherms and ectotherms– Use a variety of behavioral

responses to control body temperature (Ex. moving in and out of sun)

4. Behavioral Responses

• 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 – nonshivering thermogenesis (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.

• Many species of flying insects– Use shivering to warm up before taking flight

Figure 40.20

PREFLIGHT PREFLIGHTWARMUP

FLIGHT

Thorax

Abdomen

Tem

pera

ture

(°C)

Time from onset of warmup (min)

40

35

30

25

0 2 4

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.

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• 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 benecessary to stay active in winter

Actualmetabolism

Bodytemperature

Arousals

Outsidetemperature Burrow

temperature

June August October December February April

Tem

pera

ture

(°C

)M

etab

olic

rat

e(k

cal p

er d

ay)

200

100

0

35

30

25

20

15

10

5

0

-5

-10

-15

Figure 40.22

• 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.