The tundra is a cold, ice-covered region on earth. recently there has been an increase in the number of plants growing there. this new plant growth is most likely due to
a) an effort by the local people to plant trees.
b) global warming, resulting in warmer temperatures on earth.
c) more people going to the area for recreation and vacations.
d) animals leaving the tundra for warmer regions with less snow cover.

B) global warming, resulting in warmer temperatures on Earth.

Explanation:

Tundra is the coldest biome of the world. It exhibit very low temperature range and treeless plain with snow precipitation. The global warming is the phenomena which is related with rise in global temperature due to abundance of greenhouse gases into the atmosphere. These gases are released into the atmosphere by burning of fossil fuels, industrial gaseous release and deforestation. These gases traps the heat energy from sunlight making the atmospheric temperature warm. As a result of global warming the ice caps and snow bearing areas of the tundra biome will deplete. The melting of the ice will provide proper unfrozen soil for the growth of plants. Hence, new plants will increase in numbers due to global warming.

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:

a- multicellular

b-eukaryotic

c-no cell wall

d-heterotrophic

e-autotrophic