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