week 10 - mammals Flashcards

Question

mammalian form: functional morphology STANCE ADAPTATION FLIGHT

Answer 1

- Pterosaurs: o Elongated metacarpal and phalange V (little finger) - Bats: o Elongated metacarpals and phalanges - Birds o Feathers are stiff so do not need to extend limb Support wing with phalanges

Answer 2

- Greatly reduced upper limb o Reduce drag - Flattened to form flipper - Simplified wrist - Extended phalanges - Digit reduction

Answer 3

PRIMATES - Thumb rotated so can touch tips of other digits - Results in power grip o Can trace back to adaptation of climbing in trees - Eventually allowed tool use Lots of these traits make us highly successful as humans Eyes at front * Better to judge distances * Jumping from tree to tree

Answer 4

Plantigrade: o Power/digger o No necessarily fast but need power in their feet o E.g. hedgehog Digitigrade: o Speed (hunting) o E.g. dog/cat o Balance need for speed and other functions Unguligrade: o Speed (escape) o E.g. deer

Answer 5

unguligrade - lower limb longer than upper limb (speed) digitigrade - kinda even Plantigrade - lower limb shorter than upper limb (power) - Difference in ratios (which limbs lengthen)

Answer 6

- Speed: tibia and fibula > femur - Power: tibia and fibula < femur

Answer 7

- Speed: extended

Answer 8

- Unguligrade: o fingertips (hooves) - Digitigrade o Finger (claws) - Plantigrade o Hand

Answer 9

- Perissodactyl: odd-toed - Artiodactyl: even-toes From this changes (from ancestors - reptiles) has allows lots of diversification Split in camel - To do with sand environment - Need a larger surface area

Answer 10

- Mammals have colonised and exploited areas not available to reptiles and amphibians - This is primarily due to physiological specialisations, particularly temp, regulations o Can live in cold environments because have internal temperature regulation

Answer 11

- Poikilothermy: o Body temp. varies e.g. in response to environmental change - Homeothermy: o Maintain a ‘constant ’body temp. o Humans

Answer 12

- Ectotherm: o Uses environmental heat sources to regulate body temp.  E.g. solar radiation, hot and cold surfaces - Endotherm o Generates heat internally through high metabolic rate to maintain a high body temp

Answer 13

- Generate large amounts of internal heat o 10x that of an equivalent reptile - Fur/hair which provides insulation to limit heat loss o Or heat gain in very hot conditions Expensive to maintain --> need to generate a lot of internal heat --> this requires lots of energy

Answer 14

- Controlled by system of temp. sensors and thermostat to regulate generation of heat - Body temp (Tb) typically maintained at 37degreesC “set point” - Regulation usually very tight (<1degreesC varitation) but can be relaxed o E.g. hibernation or malfunction (fever) negative feedback

Answer 15

- Maintaining constant body temp costs energy o All the reactions that need to take place - ‘cheapest’ when environmental temp is close to body temp (Tb) - Each species has a range of environmental temps. Over which it can maintain Tb at ‘low’ cost (thermal neutral zone TNZ) - When the environment goes above or below TNZ the cost of maintaining Tb goes up rapidly

Answer 16

heat generation heat loss to the environment

Answer 17

H over T = C x (Tb - Ta) T = rate of heat loss H = change in heat C = conductivity (Tb - Ta): difference between body and environment temps

Answer 18

- For most mammals Ta

Answer 19

- When large your SA/vol ratio falls o Mass specific conductance (C/Kg) reduced o In extreme cold large animals tend to do better o In cold areas average size is greater (Eg. More fur so can trap more air)  Bergmann’s Rule

Answer 20

o In cold areas average size is greater (Eg. More fur so can trap more air) e.g. largest moose at coldest altitudes

Answer 21

- Mammal hair has excellent insulation - Size advantageous because increased carrying capacity o Fox about minimum size for effective insulation - Polar bears in winter experience almost no heat loss: o Blubber, fine insulating hair, guard hair  Give off no detectable heat when sleeping

Answer 22

- So well insulated they easily overheat - Move slowly and rest often - Excess heat lost where fur is absent/blood vessels close to skin o Muzzle, nose, ears, inner things and shoulders) - Swim to cool down - Fur can moult

Answer 23

- Body temp relaxed o Reduced heat loss, reduced energy demand - Some level of control retained (brainstem) and many hibernators periodically ‘emerge’ (arousal) - Torpor is similar but dinural o Daily o E.g. colder nights o Not such a long time - Great to save energy - About not being able to eat enough to survive the cold - Burrow is warmer - Huge energy savings

Answer 24

- Extremities (limbs, feet, even skin) cannot be maintained at core temp - Therefore relax body temp. in extremities by using a counter-current this is very efficient e.g. sled dogs and reindeer

Answer 25

- Generates extra heat o Direct muscular heat production - Exercise supresses shivering so cannot do both - In small animals exercise is inefficicent because: o Shivering stops o Insulative capacity of pelt is disturbed o Peripheral circulation increased (blood to muscles) leading to increased heat loss

Answer 26

- Concentrated in strategic areas: o Neck o Thorax o Major blood vessels - Well vascularised to distribute heated blood o A lot of blood flow to it - An internal solution

Answer 27

- All this is very expensive (mammals eat 10x as much food as equivalent reptile) BUT allows: o Very high/continuous activity levels o Exploitation of tropic to poles o Current temps. “low” and this is hard for ectotherms o Mammals therefore are the most successful terrestrial vertebrate group A lot of this out for debate - Reproduction o Better adaption when in female (instead of a pouch) - Continuous activity levels (mammals can be in hot or cold) o Reptiles basking in heat and hibernate in cold - Evolution able to go in ways reptiles could not because of the different traits