A certain species of trilobite is known to have lived 300 million years ago. If this index fossil was found in a rock layer containing other fossils, what could you infer about the other fossils a The rock layer killed the trilobite and the other fossils
b The other fossils are about 300 million years old
c The organisms that formed the other fossils are still living.
d The rock layer formed before the trilobite and other organisms

b The other fossils are about 300 million years old

Explanation:

From the description of the problem given, we can correctly conclude that the other fossils are about 300 million years old and even the rock layers formed around that period in time too.

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation:

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.