Explain the biological basis for assigning all human populations to a single species. can you think of a scenario by which a second human species could originate in the future?

Molecular biology (DNA sampling) is the best proof.

Explanation:

An study published in the journal of science found that 99.9% of humans are quite similar. The  scientific team analysed DNA from 1,056 people from 52 populations in Africa, Eurasia (Europe, the Middle East, Central and South Asia), East Asia, Oceania and the Americas.

The phenotype ( visible appearance) results from a very small proportion of  differences in genetic traits, hence the concept "race" is more a cultural concept than a biological concept.

telophase and anaphase

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.