(7) the stability and sustainability of our environment depend most heavily on
a) the predators of various ecosystem
b)the decisions and actions of humans
c)the weather
d)the number of individuals in each population

If you have too few individuals, then the population is not stable meaning it collapses and the species dies off (due to members not able to reproduce at the proper rate/amount).

If you have too many individuals, then the resources are over-consumed and it's not a sustainable model. In other words, there are too many individuals and there isn't enough food, water, etc.

The key is to have a balance so you don't go too low or too high with the population.

"griffith's experiment discovering the "transforming principle" in pneumococcus bacteria. griffith's experiment, reported in 1928 by frederick griffith, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation." - griffith's experiment.