What would happen if biologists kept introducing hares into the environment to keep the hare population at a high and constant level And what would happen if biologists kept only the lynx population at a high and constant level

More food is available for predators.

Explanation:

If biologists kept introducing hares into the environment to keep the hare population at a high and constant level so there is more availability of food for the predator and so the population of predator increases. If there is no predator for the hare so it will increase in number and eliminate all the vegetation of the environment while on the other hand, if the biologists kept only the lynx population at a high and constant level so it decreases the population of hares because lynx feeds on hare.