Ch 40 – Animal Form & Function

Evolution of Animal size & shape Constrained by physical forces Convergent evolution i.e. fusiform shape for aquatic animals Seal Penguin

All cells need access to aqueous environment Why? How do surface area & volume relate to exchange of materials? Exchange 0.1 mm 1 mm Exchange Gastrovascular cavity 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: Protection Sensory organs Better able to deal with environmental changes Villi

Cells  Tissues  Organs  Organ systems What coordinates & controls the systems?

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

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

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

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

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)

Organisms exchange heat by four physical processes:

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

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

Warm blood from arteries is used to warm blood in adjacent veins allows for transfer of heat to colder blood coming from extremities Countercurrent heat exchange – in many birds & mammals, also sharks, dolphins

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

move to warmer or cooler area move closer together Some insects have specific postures for thermoregulation

Thermogenesis: - 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

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

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

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 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

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

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

bear hibernation planet-presents/videos/natural-world-bear- hibernation.htm Thermoregulation in animals (4:08)