The original source of genetic variation that serves as the raw material for evolution is
(a) mutation
(b) genetic drift
(c) gene flow
(d) sexual recombination
(e) random fertilization

Environmental differences within ecosystems are generally caused by

Which set of characteristics best describes sedimentary rock? a) largest type of rock, made of organic matter, hardest type of rock b) often contains layers, forms near sources of water, contains fossils c) least abundant type of rock, made of other rocks, made mostly of minerals d) most abundant type in earth's crust, made of magma/lava, contains no fossils

One of the reasons that stars are so large is because