Oxygen first entered earth's atmosphere when one-celled organisms resembling modern cyanobacteria began to carry out the process of

a fossilization
b evolution
c photosynthesis
d erosion

It has been said that veterinarians are the world's best doctors, since their patients cannot tell them what is wrong. what are some of the differences between human and animal medicine? what are the advantages and disadvantages of each?

Many farmers prefer cattle without horns because it is safer for their herds. the allele for no horns (n) is dominant to the allele for the presence of horns (n). a farmer mates a male with horns to a heterozygous female without horns. what is the chance that the offspring will have horns?

At which point is crust neither created nor destroyed? island chain mid-ocean ridge divergent boundary transform boundary