Because evolution itself is a very slow process. Having said that, the chance of having a continuum of various animals would mean that evolution would have progressed very fast. Because evolution is slow, different species establish themselves for different ecological niches and environments, this enables them to become better through time at a certain environment which then leads to eventual diversification in the number of species.
Because migration and and other seasonal movements can affect the possibility of finding a mate, stresses, that could affect offspring survival(can vary with season), and also availability of thing that are available for the offspring.
Physical change as no new substance is created
Answer: Tissue
Explanation:
A tissue is an ensemble of <u>similar cells and their extracellular matrix (structure) </u>from the same origin that together carry out a specific function.