What causes the differences in physical characteristics like hair color among people?
different versions of genes
variations in DNA length
different numbers of chromosomes
variations in cell nucleus size

How did the research presented in the article affect scientists' understanding of the evolution of eukaryotes

The phylogenetic tree illustrates the relationship between humans and our closest living relatives. the tree was based on biochemical comparisons, including dna and amino acid sequences. according to the biomolecular data, we could infer that a) the four organisms do not have a common ancestor. b) humans are more closely related to chimps than any other apes. c) chimps are more closely related to gorillas than they are to humans. eliminate d) there is no evidence if any relationship between the four branches on the tree.

Pl as time goes by and water goes through the water cycle again and again, the amount of water on earth: increases decreases ostays the same goes up and down