Two disinfectants were tested for their effectiveness against a strain of bacteria. Disinfectant A had a clear circle with 3 mm diameter.
Disinfectant B had a clear circle with 6 mm diameter.
Calculate the difference in the bacteria-free area between disinfectant A and
disinfectant B.
e:
6.8 mm2
4.7 mm2
9.4 mm2
21.2 mm2

is 84.78 mm^2

Explanation:

we will first find out their areas, the area to be found is of a circle R^2

for the first one,

R=radius

pi=3.14

so,=3.14*(3mm*)^2

=28.26mm^2

for the second one

=3.14*(6mm*)^2

=113.04mm^2

their differences are equal to 113.04 - 28.26

=84.78 mm^2

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:

b - the respond is innate and varies over time.

good luck!