Phase change is the change in state. i.e. water to steam or ice to water
Structurally, plant and animal cells are very similar because they are both eukaryotic cells. They both contain membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, golgi apparatus, lysosomes, and peroxisomes. Both also contain similar membranes, cytosol, and cytoskeletal elements.
The change in the environment affected how the organism would evolve to be so that it could survive. the term for that is survival of the fittest, and only the fittest would be able to survive the conditions of its surrounding environment. hope this answered your question. :)
