The time periods of the Paleozoic and Mesozoic are subdivided into early, middle, and late unlike in the Cenozoic because the number of fossils discovered outnumbers the quantity needed to subdivide the periods based on the presence of organisms.
<span>Early, middle and late time are geological times. Time periods were subdivided because of the major evolutionary events in the fossil record during the Paleozoic and Mesozoic era. </span>
Under Mesozoic:
<span>· </span>Cretaceous
<span>· </span>Jurassic and
<span>· </span>Triassic
Uner Paleozoic:
<span>· </span>Permian
<span>· </span>Carboniferous
<span>· </span>Devonian
<span>· </span>Silurian
<span>· </span>Ordovician and
<span>· </span>Cambrian
<span>While in Cenozoic we have the tertiary or mammals diversity only.</span>
Answer:
Over time, many species gradually adapted to a more oxygen-rich enviroment, allowing them to survive in shallow water and on land.
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