This is an organ of digestion. It continues the process of mechanical digestion; it secretes gastric juices that continue the process of chemical digestion started in the mouth.

it has one origin of replication, but it proceeds in two directions - d)

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:

after a the power stroke, adp is released, but the cross-bridge formed is still in place. atp then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.