2.5 Metabolism and Adverse Conditions Flashcards
In some environments extremes of temperatures can result in what?
in a lack of food and drought
How do they cope with these fluctuations?
to cope with these fluctuations which can be cyclic or unpredictable, organisms have adaptations to survive them or to avoid them
What is dormancy?
(surviving adverse conditions)
to allow survival during a period when the energy costs required for normal metabolic activity would be too high, the metabolic rate can be reduced
this can be achieved by a period of dormancy
dormancy is part of an organisms lifecycle and can be predictive or consequential
What is predictive dormancy?
predictive dormancy is when an organism becomes dormant before the onset of adverse conditions and is usually genetically determined
it is typical of predictable seasonal environments where the temperature and photoperiod can be used as environmental triggers
what is photo period?
number of daylight hours
what is consequential dormancy?
when an organism becomes dormant after the onset of adverse conditions
it is a typical response of organisms living in unpredictable environments
What is leaf loss?
some plants lose their leaves and enter a period of dormancy (inactivity) when the climatic conditions are not suitable for growth e.g. during cold winters or summer drought
What is seed dormancy?
the seeds of some plant species display periods of dormancy when they fail to germinate even under ideal conditions
ideal conditions - Water Oxygen Warmth
This can be due to the presence of chemical inhibitors which prevent the growth of the embryo plant or to the presence of an impermeable seed coat which forms a physical barrier to the uptake of water
What does hibernation allow animals to do?
to survive cold winter conditions and involves the lowering of body temperature, heart and breathing rates and oxygen consumption. This lowers metabolic rate at a time when food is limited
What happens before hibernating?
a mammal eats extra food and stores it as fat.
the fat is used up as an energy source during hibernation
Why do homeostatic mechanisms remain active during hibernation?
homeostatic mechanisms remain active during hibernation - maintaining a lower body temperature to prevent freezing
What does decreasing photoperiod act as?
trigger for hibernation
What is daily torpor?
some animals undergo short periods on a daily basis when their body temperature, heart and breathing rates and oxygen consumption are lowered
Benefit of daily torpor?
conserves energy between feeding or may occur at night when temperature falls
Daily torpor is common in what animals?
this type of behaviour adaptation is typical in small animals with high metabolic rate e.g. humming bird
Explain Daily torpor in humming birds?
humming birds have an extremely high metabolic rate with a heart rate that can exceed 1200 beats per minute. Their energy consumption is so great that humming birds use daily torpor to conserve energy in tropical conditions
What is aestivation?
aestivation is a form of dormancy that allows some animals to survive in periods of high temperature or drought in summer when food or water may become scarce.
What does aestivation typically involve?
involves burrowing into the ground where moisture levels are higher and temperatures are lower than on the surface
Why does aestivation require less energy than hibernation?
to maintain a minimum body temperature and so the animal does not require a large store of body fat
e.g. snails, earthworms, lizards and some tropical butterflies
Example of aestivation: Water holding frog?
the water holding frog buries itself in sandy ground in a secreted, water tight, mucus cocoon during periods of hot dry weather and remains in this state until the arrival of rain and conditions improve
Example of aestivation: Lungfish?
lungfish is an example of a species showing aestivation which allows them to survive without water for up to 3 years. They have lungs as well as gills allowing them to breathe air. When its lake dries up the fish burrows into the mud, secreting mucus covering its entire body. The mucus dries up to from a sac holding the moisture in even when the mud dries completely. The lungfish stays moist and breathes through a mucus tube.
TOPTIP
In predictive dormancy the organism enters dormancy before the adverse conditions begin
In consequential dormancy the organism enters dormancy after the adverse conditions begin
When does migration usually take place?
migration is a relatively long distance movement of individuals which usually take place on a season basis
What does migration enable animals to do?
to avoid metabolic adversity brought about by lack of food and low temperatures or predation by expending energy to relocate to a more suitable environment
