Why is excretion necessary to maintain homeostasis?

How many copies of each chromosomes should be present in each of the 4 final haploid versions of gamete?

A(n) is a molecule influences the way that a molecule reacts.

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled