How does reproductive or geographic isolation affect speciation?
With these forms of isolating mechanism in place, two populations (for say) cannot interbreed creating discreet offspring. Over time, as the two populations become more different in terms of their genetics (by mutation, natural selection or gene flow affecting allele frequencies), they will become more different from each other as there is no gene flow between the two populations. The differences will amount to a stage where the two populations are so different that they are considered two completely distinct species.

Describe fossil evidence for macroevolution (big changes in evolution).
Fossil evidence provides skeletal characteristics of animals in a particular time. Differences and similarities can be drawn from many fossils and be compared within an ancestral tree. These differences between species suggest evolution and the similarities provide assurance of relations between species. [NB: I cannot explain this well, sorry]

Describe different types of evidence for evolution (use the following words in the answer: DNA, embryos, fossils).
[I'll be brief] DNA gives conclusive evidence of evolution.
Embryos show evidence of life being derived from a super-ancestor. Many different species show similar embryos, indicating that life originated from a super-ancestor and are not different due to evolution.