Based on their number of valence electrons, which group of elements will gain two electrons by bonding with other atoms?

a. o, s, se, te, po

b. be, mg, ca, sr, ba

c. n, p, as, sb, bi

d. f, cl, br, i, at

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.

Apopulation of rabbits live in a local forest. some had a mutation for a large body and long legs. the graph below shows the number of both the mutant and the normal rabbits over 5 generations. which of the following statements is true for this scenario? question 7 options: the rabbits with the mutation were more successful with restricted food than the normal rabbits. both sets of rabbits were equally successful with the restricted food source. i the normal rabbits were more successful with restricted food than the rabbits with the mutation. the graph does not let us know which rabbit was more successful.

True or false: (a) the strings of little red dots represent carbohydrates. (b) the model is called a bilayer because there are two main types of molecules present, lipids and proteins. (c) the many black lines represent amino acid tails. (d) this model shows membrane transport. (e) the blue ovals are hydrophobic. (f) the blue ovals represent phospholipid heads.