The Environment

The Environment This is made up of all the biotic (living) and abiotic (non-living) factors which affect the lives of organisms.

Abiotic Factors These are the non-living factors in the environment. Light Gravity Temperature Water Current Chemicals Touch Sound Pressure Wind Substrate Fire

Tolerance The environmental factors that can affect an organism, be they biotic or abiotic, do not remain constant. Abiotic factors such as temperature, wind and humidity can vary from day to day and from season to season. Other factors may change more slowly E.g. levels of predation and food supply.

Tolerance An organism that is living successfully in an area must be able to Tolerate any such changes. If it could not, it would have either died out or moved to a more suitable place. An organisms ability to survive variation in environmental conditions is called Tolerance. Tolerance varies between species.

Examples Trout eggs will develop at temperatures between 0ºC and 12ºC, while frogs’ eggs will tolerate a 0ºC to 30ºC range.

Tolerance Tolerance varies within species as well. E.g. Human tolerance to temperature. In winter some students appear to keep warm with only a cotton blouse, while others feel cold even with a jersey.

Acclimation It is possible for the tolerance or an organism to change, if, the conditions change slowly. This is called Acclimation. All organisms become acclimated to the seasons. Dogs, cattle and many other mammals grow a thicker coat of fur as winter approaches and cast it off with the onset of the following warm season.

Acclimation Many species of mammals and birds increase their tolerance of the cold by accumulating a fat layer beneath the skin which improves heat insulation.

Picture This……… You have 2 fish tanks, A and B Tank A Tank B

Picture This Everyday for a month or 2 you put a pinch of salt into Tank B, so it very gradually gets saltier. If you then shifted a fish from Tank B into the fresh water of Tank A, it would die. This is because the fish in Tank B have become acclimated to the saltier water – as it was done slowly.

Try This. Explain why athletes train at high altitudes?

Answer. At high altitudes, body would increase the production of red blood cells. If training at gradually higher altitudes over a training season, the athlete would have a larger number of red blood cells than the athlete who trained at sea level.

Biotic Factors These can be: Intraspecific (between members of the same species) Interspecific (between members of different species) WS – Inter and Intraspecific Competition