Why do some animals in the taiga experience a seasonal color change?

Assume that a student is given two different models of bacteria, with one model consisting of big bacteria and the other consisting of small bacteria. how can the student demonstate the theory of endosymbiosis using the models

Which event would lead to primary succession of a forest?

About how many years does it take for one cycle of surface water to become deep water and then surface water again in the oceans? 101001,000