Asequence of nucleotides found in the dna of this chromosome codes for a specific protein or trait. this segment of dna is known as a(n) a) allele. b) codon. c) gene. d) nucleotide.

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.

Study the picture of the ocean. which is the best example of an organism’s niche shown in the picture? a. the environment contains several of the same species of coral. b. the shallow area of the ocean meets the needs of the coral and the fish. c. the ocean has fish and coral that live in the same area. d. the coral take in food from the water and provide shelter for the fish.

Mulitple choice which of the following is a function of the nucleus? a. stores dna b. stores sugars c. builds proteins d. packages proteins