adaptation 13

Question 1

What is meant by adaptation?

Answer 1

Adaptation permits differential success (survival and reproduction) of individuals within a population due to their interaction with the environment

Question 2

How might an animal be adapted to live in the dessert?

Answer 2

1) Nocturnal activity (lower environmental
temperature)

2) Live in burrows (stable thermal
environment)

3) Relies on water in food and metabolically
produced water

4) Highly efficient kidneys to reabsorb water

5) Countercurrent system in nose conserves
water

6) No sweat glands

Question 3

Main types of animals living in caves?

How might they differ from epigeal animals?

Answer 3

Troglobites: spend their whole lives underground
e.g. Fish, salamanders, molluscs, worms, crustacea, arthropods

Trogloxenes: casual visitors which must exit the cave to eat e.g. Bats, Cave swallows, insects

Troglophiles: live equally well in caves or on the surface
e.g. Bats, insects

• Loss or reduction of pigmentation
• Loss of eye structures / reduced requirements for eyes
• Improved sensory systems – lateral line in fish, antennae in arthropods
• Alterations to circadian rhythms
• Lower metabolic rate

Question 4

Adaptations of cave dwelling Astyanax mexicanus?

Answer 4

Blind - Vision not required in dark caves
- reduction of metabolic cost during development

Enhanced lateral line - more hair cells -> more sensitive, detect vibrations

Low metabolic rate - survive in conditions with scarce food

• increased fat reserves also help combat starvation
• requite less oxygen

Reduced aggression

Question 5

What is homeostasis?

Answer 5

Homeostasis (Allostasis): the maintenance of a steady state or internal balance

A dynamic equilibrium between external factors that modify an animal’s internal environment and internal control mechanisms that oppose such changes

Question 6

Explain negative and positive feedback - give example

Answer 6

Negative feedback -> a change in a variable triggers a control mechanism to counteract further change in the same direction
- e.g. Homeostatic reaction to changes in temperature

Positive feedback -> change triggers mechanisms that amplify change rather than reversing it
- e.g. Opening of uterus during childbirth

Question 7

Which organ monitors temperature? What feedback loops does it use?

Answer 7

Hypothalamus -> uses negative feedback loops
- can increase temp when ill (fever)
-

Question 8

Why must body temp remain stable?

Answer 8

Metabolic reactions are catalysed by enzymes that work best in a narrow temperature and pH range

Higher temperatures can speed up metabolic reactions, but may damage the enzyme

Body temperature is therefore optimised to protect metabolic reactions

Question 9

Differences in body temp between endo and ectotherms?

Answer 9

Endotherms - Maintains internal temperature (regulators)
e.g. mammals, birds, some fish

Ectortherms - Internal temp. fluctuates with environment (conformers)
e.g. reptiles, amphibians, some fish

Question 10

Mechanisms that balance heat loss/gain?

Answer 10

The integumentary system (skin + appendages)
- sweat, erected hairs, blood vessels

Insulation
- layers of fat, wool, feathers

Circulatory adaptations

• vasoconstriction and vasodilation
• countercurrent heat exchange

Evaporative heat loss
- sweating, panting

• Behavioural responses
• basking in sun, seeking shade, body postures

Adjusting metabolism
- shivering, heat instead of ATP in mitochondria

Acclimatisation, migration and hibernation

• shedding hair, winter coats, changing active enzymes
• can be hyperphagic (eat more) to build up fat stores
• Estivation, dormancy in summer to avoid drying out

‘Physiological thermostats’

Question 11

Long-term deviations from homeostasis can lead to what?

Answer 11

Allostatic Load – accumulates when exposed to prolonged/chronic stress,

• Post Traumatic Stress Disorder and Depression