If a population reaches its critical population density, this could happen:

weaker offspring
population crash
inbreeding
all of the above

Population crash is a sudden decrease in the number of people found in a given area as a result of shortage or the lack of environmental resources necessary for reproduction, survival and growth of the population. It is also known as a die back. The answer to your question is A. population crash.

Dthe lipid is most likely

I’m not exactly sure what your trying to ask, but if it’s how an organelle is similar to a body system or a part a nucleus is like a in function. but i don’t fully understand what you’re trying to ask