Survival strategies that maintain metabolism when conditions are adverse, including dormancy (predictive and consequential), hibernation, aestivation and daily torpor, and migration as a way of avoiding unfavourable conditions, together with how migration is studied.

What this key area is asking

The SQA wants you to describe how organisms survive when conditions are too harsh for normal metabolism, distinguish predictive from consequential dormancy, describe hibernation, aestivation and daily torpor, and explain migration as a way of avoiding unfavourable conditions, including how migratory behaviour is studied.

Dormancy

Predictive dormancy is an advantage in habitats where harsh conditions arrive reliably each year, because the organism can prepare in advance. Consequential dormancy suits less predictable environments, where the organism reacts only once conditions actually worsen.

Hibernation, aestivation and torpor

These are forms of reduced metabolism that help animals survive when conditions are too harsh for normal activity. By lowering the metabolic rate, the animal greatly reduces its energy demand, so it can survive on stored body reserves:

• Hibernation lowers metabolic rate and body temperature to survive cold winters with little food, for example in hedgehogs and ground squirrels.
• Aestivation lowers metabolic rate to survive hot, dry conditions such as a summer drought, for example in some snails and lungfish.
• Daily torpor is a short period of greatly reduced metabolism, common in small animals with high metabolic rates (such as some birds and bats) during the part of the day when they are inactive, which saves a large amount of energy.

Migration

Unlike dormancy, which lowers metabolism in place, migration is a strategy of moving away from the problem altogether. Migratory behaviour can be innate (genetically inherited) or learned (developed through experience), and often it is a combination of both. Scientists study migration using methods such as:

• Ringing (banding), attaching a marked ring to an animal so it can be identified if recaptured.
• Satellite tracking with small transmitters that record an animal's route in detail.

These techniques reveal where animals go and help distinguish innate from learned behaviour.

Examples in context

Example 1. Arctic tern migration. The Arctic tern makes one of the longest migrations of any animal, travelling from its Arctic breeding grounds to the Antarctic and back each year. By moving between the two polar summers, it avoids the harsh polar winters and always finds long daylight hours and plenty of food. Satellite tracking of individual terns has revealed their exact routes, confirming round trips of tens of thousands of kilometres and showing how migration lets an animal escape adverse conditions entirely.

Example 2. Hibernating ground squirrels. Ground squirrels enter predictive hibernation as day length shortens in autumn, dropping their body temperature close to freezing and slowing their heart rate dramatically. This greatly reduced metabolism lets them survive the winter on fat stored during the summer. The example shows predictive dormancy and hibernation working together as a survival strategy in a reliably seasonal habitat.

Try this

Q1. State the difference between predictive and consequential dormancy. [2 marks]

• Cue. Predictive begins before conditions deteriorate (triggered by a cue); consequential begins after conditions have worsened.

Q2. Give one method used to study the migration routes of birds. [1 mark]

• Cue. Ringing (banding) or satellite tracking.