What is what ? how it could be define?

Which feature of a human community is similar to a niche in a biological community

Why were the results whit just water so much different than the trials with the detergent ?

Fossils of ancestors of the modern horses show a small 4-toed almost dog-like browsing animal named eohippus over time the horses got larger lost toes and changed to a grazing diet what is the best explanation of why this change occurred