Animal Survival : Animal Survival Responding to the Environment Mr G Davidson
Animal Responses : Animal Responses Animals are continually being subjected to signs or signals coming from the environment around them.
Environmental signals are called STIMULI and animals will RESPOND to them in a variety of ways.
Animal Responses : Animal Responses The way in which an animal responds to stimuli from the environment makes up the animal’s behaviour.
This behaviour is important for an animal’s survival.
Choice Chamber : Choice Chamber
Regular events in the Environment : Regular events in the Environment Some environmental conditions vary regularly.
E.g. light during the day and dark at night.
The days are warm and long in summer and cold and short in winter.
Daily Changes : Daily Changes These changes occur every 24 hours.
The most obvious is light and dark.
Many animals have adapted their behaviour to being active and feeding during the day (DIURNAL animals) whereas others are active at night (NOCTURNAL animals).
Diurnal Animals : Diurnal Animals
Nocturnal Animals : Nocturnal Animals
Annual Changes : Annual Changes Over the period of a year there are seasonal changes.
During summer the number of daylight hours (daylength) is greater than in winter.
Tidal Changes : Tidal Changes Most seashore animals show some adaptations to the tidal movement.
Tidal movement occurs twice daily – i.e. 2 high tides and 2 low tides in 24 hours.
Annual Rhythm : Annual Rhythm Rhythmical behaviour occurs in response to regular changes in the environment.
Environmental stimuli like changing daylength, light and dark, etc. can set off certain responses in animals.
These stimuli are referred to as TRIGGER STIMULI.
Migration is an example of annual rhythmical behaviour brought about by changes in daylength.
Migration : Migration
Rhythmical Behaviour in Shore Crabs : Rhythmical Behaviour in Shore Crabs Daily tidal changes bring about a rhythmical behaviour pattern in many seashore animals.
The shore crab regulates its period of activity to coincide with the movement of the tide.
The shore crab is found in rock pools.
Shore Crab : Shore Crab
Rhythmical Behaviour in Shore Crabs : Rhythmical Behaviour in Shore Crabs It is a carnivore, feeding on other small seashore animals.
When shore crabs are observed in their natural habitat, they lie beneath rocks and seaweed and are inactive when the tide is out.
When the tide comes in they become active and start their feeding behaviour.
General Features of Rhythmical Behaviour : General Features of Rhythmical Behaviour Rhythmical behaviour patterns are REGULAR, i.e. once a day, once a year, etc..
In all cases the behaviour pattern is set off by a trigger stimulus.
If the trigger stimulus is removed and the animal placed in constant conditions then the true rhythmical behaviour pattern will carry on.
General Features of Rhythmical Behaviour : General Features of Rhythmical Behaviour For this to happen the animal must have some method of measuring time to let it start the behaviour pattern when it should.
This is seen with the shore crab.
When tidal movements were removed by keeping the crab in a tank in the lab, it still became active at the time of high tide.
Animals have a BIOLOGICAL CLOCK for measuring time.
Courtship and hibernation are 2 more examples of behaviour patterns which recur annually.
Biological Clock : Biological Clock
Courtship : Courtship This type of behaviour ensures that the male and female are both ready to produce sex cells at the same time.
This means that the eggs will have a greater chance of being fertilised.
The best time for animals to have young is during spring.
Courtship : Courtship
Courtship : Courtship Weather conditions are good and food is plentiful.
This means the young have a better chance of survival.
Courtship : Courtship Most birds produce their eggs soon after mating, and hatching occurs a few weeks later.
In contrast, red deer don’t have their young until 6 months after mating.
During experimental investigations, it was found that if animals were kept in constant environmental conditions in the lab, they would still show courting behaviour at the usual time of year.
Courtship : Courtship
Hibernation : Hibernation Mammals are warm blooded animals which means they have a constant body temperature greater than the surrounding air temperature.
When the air temperature is very low, e.g. during winter, the animal will lose energy very quickly.
To replace that energy the animals must eat an increased amount of food.
Hibernation : Hibernation
Hibernation : Hibernation During severe winter conditions, however, food is not readily available.
The more an animal moves around looking for food, the more energy it uses.
During severe winters the animal may die.
Hibernation : Hibernation To overcome this problem of energy loss and to increase the chance of survival during the winter, some animals hibernate.
The animal reduces its rate of using energy by stopping movement and reducing it’s body temperature.
Hibernation : Hibernation The animal goes into a type of “sleep”.
Hedgehogs and bats are examples of hibernating mammals.
Before they go into hibernation the animals must increase their feeding to build up reserves of food which can be used over the period of hibernation.
Hibernation : Hibernation
Biorhythms : Biorhythms Recurring behaviour patterns occur in humans.
These are called biorhythms.
Patterns that occur over a 24hour period are called CIRCADIAN RHYTHMS, and when they get disturbed on long distance air flights across time zones, this give rise to “Jet Lag”.