Question

Which one or more of the following phenomena make(s) small populations vulnerable to extinction?

• A. Inbreeding depression
• B. Demographic stochasticity
• C. Intraguild predation
• D. Continuous population growth

Hint:

Focus on mechanisms that get worse specifically as population size shrinks, not general predator-competitor interactions or population growth.

Answer 1

The Correct Option is A, B

Conservation biologists have a fairly specific list of reasons why small populations are especially fragile, and this question is testing whether you can tell those genuine small-population risks apart from general ecological interactions or from a factor that actually reduces risk. Let's take the options one at a time.

1. Inbreeding depression: With fewer individuals to choose mates from, related individuals end up breeding with each other more often. This increases the odds that harmful recessive traits show up in offspring, reducing their survival and reproduction, which is a well known danger specific to small populations.
2. Demographic stochasticity: This is just random chance acting on individual life events, like who happens to die or what sex the offspring happen to be in a given year. In a big population these random swings cancel out, but in a small population an unlucky run of events can tip the group toward collapse, so this is also a genuine small-population risk.
3. Intraguild predation: This describes one competing species eating another, which is a general ecological interaction that can happen in populations of any size. It is not a phenomenon that specifically targets or worsens with small population size, so it does not belong in this list.
4. Continuous population growth: A population that is steadily growing is becoming less vulnerable, not more, since larger numbers give more of a buffer against random loss. This option describes the opposite of a risk factor.

Only inbreeding depression and demographic stochasticity are recognised mechanisms that specifically threaten small populations more than large ones.

Let's summarize:

• Small populations lose genetic diversity fast, causing inbreeding depression.
• Small populations cannot buffer random demographic swings the way large ones can, which is demographic stochasticity.

So the correct options are (A) and (B).