Explain why a change to the green-leaf population caused the wee-bug population to change in size?

If there are fewer births than deaths, then the size of the population will decrease. Organisms in consumer populations get energy storage molecules from eating organisms in resource populations. The more energy storage molecules available to a population, the more the organisms in that population can reproduce.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.