What two factors are used to define a species?

A species is often described as the largest category of organisms whereby two individuals with the respective sexes or combinations may bear fertile offspring, generally by race. They are also used for the definition of the species as a caryotype, DNA, morphology, comportament or environmental niche..

Explanation:

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the awnser is d i think

amber has allowed scientists to study dna that has been preserved over millions of years.