Multiple things cause the migration of people.
Economic issues arise:
People run out of jobs and opportunities
(BIGGEST REASON)
Cultural reasons:
Forced intentional migration had occurred in the past on accounts of slavery and political instability
Safety:
More popular reason now is because of war or fights with other countries, the people want to keep their family safe so they move them or move with them
Hope this helped
Answer:
the animals
Explanation:
the difference between animal life in the Mesozoic Era and the early Cenozoic Era is that in the Mesozoic Era the reptiles were dominate and in the Cenozoic Era the mammals were dominate.
The heart is an organ (rather than a tissue) because it has an important (and complex) function. Tissues don't have nearly as many things in it as the heart does.
Hope this helps! :)
They transport amino acids
