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