Primary producers make their own food for example plants. As you go into the upper levels of the food chain the energy gets distributed to each level, but they lose some of their energy. Without primary producers alligators will not be able to obtain the energy they need for themselves to survive.
Because there was a mutation in the gazelle's genetic code. It will be nice for the gazelle to run faster, but since the gazelle was born with longer legs, we know it's just a random mutation. The gazelle's parents have little to do with it, and the nutrition of the food it eats after it's born is irrelevant to how long its legs are at birth.
<span>Molecular clocks use rates of mutation to measure
evolutionary time. Mutations add up at a fairly constant rate in the DNA of
species that evolved from a common ancestor. The more mutations that happened
in each lineage, the greater is the differences between these lineages.</span>
