1. The population number of a keystone species begins to decline. It declines so that the population is only 10% of its original size. How will this affect the biodiversity of the area?

A. Due to the decline in the current keystone species, another organism will take its place and become a new keystone species; therefore, biodiversity will remain unchanged.

B. The decline of the keystone species will affect the entire ecosystem. If the population of the keystone species shrinks, then the biodiversity of the area decreases.

C. When a keystone species' numbers decrease, only the producer level in the ecosystem will decline, so biodiversity will decrease, but only slightly.

D. Keystone species are usually at the top of the food chain; if their numbers decline, the levels below them will change.

The decline of a keystone species can have a significant impact on the biodiversity of an area. Keystone species play critical roles in maintaining the structure and function of an ecosystem. They have a disproportionate effect on their environment relative to their abundance.

When the population of a keystone species declines to only 10% of its original size, it can disrupt the balance of the ecosystem, leading to a decrease in biodiversity. The interactions between the keystone species and other organisms in the area can be disrupted, causing ripple effects throughout the food web.

For example, if a keystone species is a predator, its decline could lead to an increase in the population of its prey species, which may then outcompete other organisms and reduce their abundance. This can lead to a loss of species and a decrease in overall biodiversity.

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