A scientist is trying to isolate a penicillin-resistant His- bacterial mutant from a mixed population. To isolate penicillin-resistant mutants, the scientist must inoculate the parent population on plates containing ; this approach is selection.

Penicillin, direct

Explanation:

this scientist has to inoculate the parent population using plates that contains penicillin in them. we call this approach the direct selection.

In the direct selection, bacteria is grown on a material that has penicillin in it. the goal is to find mutants that have resistance to penicillin. only these resistant ones would grow and then a direct identification would be done.

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:

sand 60

clay 10

silt 30

sandy loam should be dominated by the sand. as the amount of sand increased, the amount of slit needed to anchor the plants' roots to the sand will also be increased. even though the amount is very little, 10% part of clay is still necessary for proper oxidation.