Ch 40 animal form function
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Ch 40 – Animal Form & Function. Form & function. Evolution of Animal size & shape Constrained by physical forces Convergent evolution i.e. fusiform shape for aquatic animals. Seal. Penguin. Exchange with Environment. Mouth. Gastrovascular cavity.

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Ch 40 – Animal Form & Function

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Ch 40 animal form function

Ch 40 – Animal Form & Function

Form function

Form & function

  • Evolution of Animal size & shape

    • Constrained by physical forces

    • Convergent evolution

      • i.e. fusiform shape for aquatic animals



Exchange with environment

Exchange with Environment




  • All cells need access to aqueous environment

  • Why?

  • How do surface area & volume relate to exchange of materials?




0.1 mm

1 mm

(a) Single cell

(b) Two layers of cells

Ch 40 animal form function

  • More complex animals – have highly folded internal surfaces for maximum exchange


Advantages of a complex body:


Sensory organs

Better able to deal with environmental changes

Gas exchange alveoli

Gas Exchange & Alveoli

Nutrition microvilli

Nutrition/ Microvilli

Excretion nephron


Circulation heart


Organization of body plan

Organization of body plan

  • Cells  Tissues  Organs  Organ systems

  • What coordinates & controls the systems?

Feedback control helps maintain a stable environment

Feedback control helps maintain a stable environment

  • regulator – animal that uses internal mechanisms to control internal environment

  • conformer – animal that allows internal environment to change in response to external variable



  • -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

  • For a given variable, fluctuations above or below a set point serve as a stimulus

  • - sensor detects & triggers response

Negative feedback

Negative feedback –

  • Control that reduces the original stimulus; maintains homeostasis by returning to “normal range”

Positive feedback

Positive feedback

  • Control mechanism that amplifies the stimulus (is not used for maintenance of homeostasis)

Alterations in homeostasis

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

  • Homeostasis can adjust to changes in external environment, a process called acclimatization

Thermoregulation an example of homeostasis

Thermoregulation: an example of homeostasis

  • the process by which animals maintain an internal temperature within a tolerable range

Endothermy and ectothermy

Endothermy and Ectothermy

  • Endothermic animals generate heat by metabolism; birds and mammals are endotherms, some insects

  • (have more stable temperature in a changing environment)

  • Ectothermic animals gain heat from external sources; ectotherms include most invertebrates, fishes, amphibians, and nonavianreptiles

  • (tolerate larger range of temperatures)

Balancing heat gain heat loss

Balancing heat gain & heat loss

  • Organisms exchange heat by four physical processes:

Adaptations for heat regulation

Adaptations for heat regulation

  • Insulation

  • - major thermoregulatory adaptation in mammals and birds

  • Skin, feathers, fur, and blubber reduce heat flow between an animal and its environment

  • The integumentary system is frequently involved in regulation

  • - skin, hair, nails

Circulatory adaptations

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

  • Vasodilation - blood flow in the skin increases, facilitating heat loss

  • Vasoconstriction - blood flow in the skin decreases, lowering heat loss

Circulatory adaptations1

Circulatory adaptations

Countercurrent heat exchange – in many birds & mammals, also sharks, dolphins

  • Warm blood from arteries is used to warm blood in adjacent veins

  • allows for transfer of heat to colder blood coming from extremities

Circulatory adaptations2

Circulatory adaptations

  • Evaporative heat loss –

  • water absorbs heat when it evaporates, so heat is carried away from surface by water vapor

  • Adaptations: sweat glands, birds with pouch with blood vessels in mouth

Behavioral responses

Behavioral responses

  • move to warmer or cooler area

  • move closer together

  • Some insects have specific postures for thermoregulation

Adjusting metabolic heat production

Adjusting metabolic heat production

  • Thermogenesis:

  • - adjustment of metabolic heat production to maintain body temperature

  • - increased by muscle activity such as moving or shivering

  • - Nonshiveringthermogenesis takes place when hormones cause mitochondria to increase their metabolic activity (heat vs. ATP)

  • - Some ectotherms can also shiver to increase body temperature

Acclimatization in thermoregulation

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

Ch 40 animal form function

  • Thermoregulation is controlled by a region of the brain called the hypothalamus

  • The hypothalamus triggers heat loss or heat generating mechanisms

  • Fever is the result of a change to the set point for a biological thermostat – helps fight infection.



  • - the overall flow and transformation of energy in an animal

  • - determines how much food an animal needs and it relates to an animal’s size, activity, and environment

  • Ectotherms use less energy than endotherms

Ch 40 animal form function

Metabolic rate is the amount of energy an animal uses in a unit of time

How can metabolic rate be measured?

Ch 40 animal form function

Influences on metabolic rate

Size – rate is proportional to body mass, smaller animals have higher metabolic rate per gram than larger animals

Activity metabolic rate

Activity & 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

  • Endotherms – high energy strategy, can have intense, long-duration activity

  • Ectotherms – low energy strategy,usually incapable of intense activity over long periods

Energy budgets

Energy budgets

Reproduction – high energy cost

strategies: seasonal reproduction,

life history strategy – i.e. diapause (in insects)

Torpor energy conservation

Torpor & Energy conservation

  • Torpor – physiological state of decreased activity -small mammals & birds – daily torpor (i.e. bats feed at night, torpor in day)

  • Hibernation – body’s thermostat is turned down in winter, due to cold & food scarcity (seasonal response)

  • Estivation – summer torpor – due to high temp & scarce water supplies

Ch 40 animal form function

  • bear hibernation


  • Thermoregulation in animals (4:08)


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