When did the silurian period occur?

a) before the neogene era.
b) during the hadean eon.
c) during the mesozoic era.
d) after the permian era.


i know the letter d is wrong.

Where do the respiratory and circulatory systems meet? a. in the heart b. in the muscles c. in the lungs d. in the brain

How are mutations continually being generated in a population (what are some of the causes of mutatuions? ) explain

Which statement best describes the relationship between an allele and a gene? question 1 a. an allele is a variation of a gene that can be expressed as a phenotype. b. an allele is the part of a gene that attaches to messenger rna molecules. c. an allele is a segment of a dna molecule that controls replication of a gene.