Ch 40 – Animal Form & Function

Form & functionEvolution of Animal

size & shape

Constrained by physical forces

Convergent evolutioni.e. fusiform shape

for aquatic animals

Seal

Penguin

Exchange with EnvironmentAll cells need access to aqueous environmentWhy? How do surface area & volume relate to exchange of materials?

Exchange

0.1 mm1 mm

Exchange

Exchange

Gastrovascularcavity

Mouth

(b) Two layers of cells(a) Single cell

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

Advantages of a complex body:ProtectionSensory organsBetter able to deal with environmental changes

Villi

Gas Exchange & Alveoli

Nutrition/ Microvilli

http://www.youtube.com/watch?v=AJ1wKsmBPvA

Excretion/Nephron

http://www.youtube.com/watch?v=glu0dzK4dbU

Circulation/Heart

Organization of body plan

Cells Tissues Organs Organ systems

What coordinates & controls the systems?

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

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

Positive feedback

Control mechanism that amplifies the stimulus (is not used for maintenance of 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 homeostasisthe 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, some insects(have more stable temperature in a changing environment)

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

(tolerate larger range of temperatures)

Balancing heat gain & heat lossOrganisms exchange heat by four physical processes:

Adaptations for heat regulationInsulation

- major thermoregulatory adaptation in mammals and birdsSkin, 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

Regulation of blood flow near the body surface significantly affects thermoregulationMany endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skinVasodilation - blood flow in the skin increases, facilitating heat lossVasoconstriction - blood flow in the skin decreases, lowering heat loss

Circulatory adaptations

Warm blood from arteries is used to warm blood in adjacent veinsallows for transfer of heat to colder blood coming from extremities

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

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

move to warmer or cooler area

move closer together

Some insects have specific postures for thermoregulation

Adjusting metabolic heat productionThermogenesis:- adjustment of metabolic heat production to maintain

body temperature- increased by muscle activity such as moving or

shivering- Nonshivering thermogenesis 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 ThermoregulationBirds 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

Thermoregulation is controlled by a region of the brain called the hypothalamusThe hypothalamus triggers heat loss or heat generating mechanismsFever is the result of a change to the set point for a biological thermostat – helps fight infection.

Bioenergetics

- 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

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

How can metabolic rate be measured?

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

Influences on metabolic rate

Activity & metabolic rate

Activity greatly affects metabolic rate for endotherms and ectothermsIn 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

Reproduction – high energy coststrategies: seasonal reproduction, life history strategy – i.e. diapause (in insects)

Torpor & Energy conservationTorpor – 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

bear hibernationhttp://animal.discovery.com/tv-shows/animal-planet-presents/videos/natural-world-bear-hibernation.htm

Thermoregulation in animals (4:08)http://www.youtube.com/watch?v=NJEBfl_LKno