Conformer

Regulator

Negative feedback

Homeostasis

Hypothalamus

Effector

Thermoreceptor Vasodilation

Vasoconstriction

Endotherm Ectotherm

Key Area 2.5

Maintenance of metabolism during environmental change

– Surviving adverse conditions

– Avoiding adverse conditions

Surviving Adverse Conditions

We are learning to

• Identify the different ways organisms have of surviving adverse conditions.

I can

• Describe the processes of hibernation, torpor and aestivation.

• Explain how these mechanisms aid survival.

Surviving adverse conditions

• Cyclic changes in environments create conditions beyond the tolerable limits of most organisms metabolism.

• What mechanisms do organisms use to survive adverse conditions?

Staying put: Dormancy

• A reduction in metabolic rate prevents an organism expending excessive energy, this is achieved by dormancy

E.g. Staying cool in hot climate

Staying warm in a cool climate

Dormancy • Dormancy occurs when an organisms growth and

development are temporarily arrested

• Metabolic rate decreases to the minimum rate required to keep its cells alive

• Energy is therefore conserved and the plant/animal is able to survive a period of adverse conditions

Predictive dormancy • Predictive dormancy occurs before the arrival

of the adverse condition

E.g. Trees respond to decrease in photoperiod (day length) and lose their leaves before winter

• Winter buds are dormant until spring

• Increasing photoperiod reverses dormancy

Consequential dormancy • Consequential dormancy occurs after the

arrival of the adverse condition

• Common in regions of unpredictable climate

• Advantageous as organism can exploit available resources for longer

Task

Around the room are cards with organisms that go through a period of dormancy. Use the cards to answer the

questions on your worksheet

Questions 1. Which of the animals go into Torpor to conserve energy?

2. Which of the animals hibernate to conserve energy?

3. What physiological mechanisms occur during hibernation to allow for this to happen?

4. What is the difference between Torpor and Hibernation?

5. Hedgehogs also carry out aestivation, what is this?

6. Why might an organism wake from torpor?

7. Which animal can actually give birth and nurse its young during Torpor?

8. Which animal can stop its heart beating, breathing and cause its blood to form ice during hibernation?

9. What environmental conditions trigger hibernation and Torpor?

10.Which animal is the only ectotherm to go into hibernation?

Hibernation • Hibernation is a form of dormancy that allows

some animals (usually mammals) to survive adverse winter conditions

• Before hibernating animals consume extra food to store as fat

What type of dormancy do hibernating animals display?

Hibernation • During hibernation

• Metabolism decreases

• Temperature decreases

• Heart rate slows

• Breathing rate slows

• Minimum energy expended

• If temperature is too low, the hibernating animal will increase their metabolism to increase their temperature

Video clip

Aestivation • Aestivation is a form of dormancy that allows

some animals to survive excessive heat or drought in summer

• Snails retreat in their shells in a ‘safe place’ with their metabolism at a minimal rate until favourable conditions return

Aestivation • Also occurs in vertebrates

E.g. Tortoises, crocodiles and lungfish

Video clip

Daily torpor • An animals metabolic rate and activity are

greatly reduced as part of every 24 hour cycle

• Heart rate, breathing rate and temperature decrease

• Common in small birds and mammals

Small animals lose heat rapidly, why?

LARGE surface area to volume ratio.

Advantage of daily torpor

• Decreases energy consumption when hunting would be unsuccessful or leave the bird open to danger

• Hunt in evening and night when cooler

Video clip

Homework: ERQ

Write notes on:

(i) endotherms and ectotherms;

(ii) temperature regulation in mammals. (10)

Marking scheme

Endotherms and Ectotherms

1.endotherms can regulate/control/maintain their (body) temperature (physiologically) AND ectotherms cannot/ectotherms temperature is dependent on their environment/behaviour (1)

2.endotherms derive (most body) heat from respiration/metabolism/chemical reactions (1)

3.ectotherms derive/get (body) heat from surroundings/environment OR description of behaviour (1)

Max 2 (from 3)

Marking Scheme 4. temperature monitoring centre/thermoreceptors in hypothalamus

OR information about temperature detected/received by hypothalamus (1)

5. nerve message/communication/impulse sent to skin/effectors (1)

6. vasodilation/widening of blood vessels to skin in response to increased temperature OR vasoconstriction/narrowing of blood vessels to skin in response to decreased temperature (1)

7. More/less blood to skin/extremities OR less/more blood in body core (1)

8. increased/more OR decreased/less heat radiated from skin/extremities (1)

9. increased temperature/body too hot leads to (increase in) sweat production OR converse (1)

10. increase in heat loss due to evaporation of (water in) sweat OR converse (1)

11. Decrease in temperature causes hair erector muscles to raise/erect hair (1)

12. traps (warm) air OR forms insulating layer (1)

13. Decrease in temperature causes muscle contraction/shivering which generates heat/raises body temperature (1)

14. temperature regulation involves/is an example of negative feedback (1)

Max 8 (from 11)

Total 10