The carrying capacity of a habitat is reached when the population growth begins to

1. Analyze the question The question asks what happens to population growth when a habitat reaches its carrying capacity.

2. Explain the concept Carrying capacity (K) is the maximum population size that an environment can support indefinitely, given its food, water, space, and other resources.

A population growing in a limited environment follows a logistic (S-shaped) growth curve:

• Lag phase: growth is slow at first.
• Exponential (log) phase: growth is rapid because resources are plentiful.
• Deceleration phase: growth slows as resources become limited and competition increases.
• Stationary/plateau phase: the population levels off at carrying capacity. Birth rate roughly equals death rate, so the population size stays steady.

3. Work through the options

• A. Increase slowly: This happens during the deceleration phase, before K is reached. It is not the answer.
• B. Increase exponentially: This happens early on, when resources are abundant. It is the opposite of what happens at K.
• C. Slow down: Growth slows as the population approaches carrying capacity. However, the question asks what happens when it is reached, and at that point growth has stopped rather than merely slowed.
• D. Remain steady: At carrying capacity the population levels off, with births balancing deaths (and immigration balancing emigration). This is correct.

4. Answer The correct option is D. remain steady.

Note: Option C is the tempting distractor, because growth does slow down on the way to K. The key wording is "is reached," which means the curve has flattened into the plateau.

5. Exam tip Picture the S-shaped curve: the carrying capacity is the flat line at the top. Flat means steady. Whenever you see "carrying capacity reached," think "plateau, birth rate = death rate."