During embryonic development, cells
increase
in number and become more
generalized.

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

The united states uses which source of energy to produce almost 40 percent of its electricity

Who discovered tuberculosis bacteria?