Consider the following statements 1 An organism with a narrow tolerance range is said to be ldquo eu...........

Geography and Environment (HCS) Concept of Ecology

Consider the following statements:

1. An organism with a narrow tolerance range is said to be “eury” whereas, that with a wide tolerance range is said to be “steno”.

2. The tolerance ranges against all the abiotic factors comprise the organism’s niche.

3. An overwhelming majority of animals and nearly all plants cannot respond to the intolerant factors by homeostasis.

Which of the above statements are correct?

1 and 2 only

2 and 3 only

1 and 3 only

1, 2 and 3

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Explanation:

Tolerance range of species :

Just as species have geographic ranges, they also have tolerance ranges for the abiotic environmental conditions. In other words, they can tolerate (or survive within) a certain range of a particular factor, but cannot survive if there is too much or too little of the factor.
Each organism has an invariably de fi ned range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its niche.
An organism with a narrow tolerance range is said to be “steno” for that factor (e.g. stenothermal or stenohaline).
An organism with a wide tolerance range is said to be “eury” (e.g. eurythermal).
Organisms can be steno with respect to one factor and eury with respect to a different one. Centrarchids (bass and sunfish) are eurythermal but stenohaline; salmonids are just the opposite. These tolerance ranges are not independent.
An organism near the tolerance limits for one factor will probably be under stress, so its ability to tolerate other factors will be reduced.
The tolerance ranges for environmental factors partly define the organism’s niche. If salinity tolerance is graphed against temperature tolerance, a niche area is de fi ned.
Ideally then, the organism should try to maintain the constancy of its internal environment (a process called homeostasis) despite varying external environmental conditions that tend to upset its homeostasis. This constancy, for example, could be in terms of optimal temperature and osmotic concentration of body fl uids.