Which of the following best describes the net primary productivity of an ecosystem? Net primary productivity is the amount of energy captured by producers through photosynthesis over time.
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Net primary productivity is the amount of energy lost by producers through respiration over time.
Net primary productivity is the amount of energy lost through respiration by producers subtracted from the gross primary productivity of an ecosystem.
Net primary productivity is the amount of energy lost through respiration by producers added to the gross primary productivity of an ecosystem.

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: