Biology (Unit 1): Tolerance, Niche & Adaptation

What is a tolerance range?

the range of an abiotic factor within which an organism can survive

What are the three zones of a tolerance range?

the optimal zone, the stressful zones, and the zones of intolerance

What happens to an organism in its optimal zone?

it is most abundant and reproduces well

What happens to an organism in a stressful zone?

it can survive but struggles and reproduces poorly

What happens in the zone of intolerance?

the organism cannot survive there

Why is an organism most abundant in its optimal zone?

conditions there best suit its survival and reproduction

What is an organism's range?

the geographic area where it lives

Give a few things that can limit an organism's range?

abiotic barriers like mountains or rivers, and biotic factors like food or competition

What is a niche?

an organism's role and the full set of conditions and resources it needs to live

Why is a niche more than just a habitat?

a niche includes the abiotic conditions and biotic interactions an organism needs, not only where it lives

What is a fundamental niche?

the full range of conditions where an organism could live, based on its tolerances

What is a realised niche?

the smaller range where an organism actually lives once other species are involved

What causes a fundamental niche to shrink into a realised niche?

biotic factors like competition and predation

Can an organism's niche change during its life?

yes, it can shift as the organism grows or changes stage

Give an example of a niche changing with life stage?

a caterpillar eats leaves while the adult butterfly drinks nectar

What is a specialist species?

a species with a narrow niche and a small tolerance range

What is a generalist species?

a species with a broad niche and a wide tolerance range

What is the difference between a specialist and a generalist?

a specialist needs specific conditions, while a generalist copes with a wide variety

Which type of species is more vulnerable to environmental change, and why?

a specialist, because a change to one of its narrow requirements can be catastrophic

Give an example of a generalist species?

an animal like a fox that lives in many habitats and eats varied food

How do abiotic factors affect where an organism can live?

each organism needs certain conditions, so abiotic factors set the limits of its range

Why might reef-building corals only live in warm, shallow, sunlit water?

they have a narrow tolerance and need stable warm conditions, making them specialists