Vertical stratification means?

Stratification in the field of ecology refers to the vertical layering of a habitat; the arrangement of vegetation in layers. ... strata) of vegetation largely according to the different heights to which their plants grow. The individual layers are inhabited by different animal and plant communities (stratozones).

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explanation:

the fossil record extends back to a dog-like ancestor some 55 million years ago, which gave rise to the first horse-like species 55 to 42 million years ago in the genus eohippus.