Question

Which scenario would most likely result in the extinction of one or more species?

The water temperature of a pond decreases slightly, and the members of the pond populations adapt to the change.
The conditions are abnormally dry for one season in a desert, resulting in the deaths of a few members of a snake population.
A predatory fish is introduced into a lake, resulting in a dramatic decrease in the populations of smaller fish.
A new plant species begins growing in a forest, resulting in a new food resource for many animal populations.

Answer 1

A predatory fish is introduced into a lake, resulting in a dramatic decrease in the populations of smaller fish.

Reason: introducing a new predator (an invasive species) can drive prey species to very low numbers or extinction because they lack evolved defenses and there may be no natural checks on the predator.