7 Complete the following crossword puzzle. 2 4 5 6 8 9 Across 1 This type of mutrient is the main source of energy 7. digests fat into fatty The enzyme acids and glycerol. 2. are used to make enzymes. 8. contains glands that secrete The gastric juice. 3. The nutrient mostly found in food such as meat, is needed for cell 9. Digestion ends in the small 4. speed up chemical reactions, Down 1. Before the body can make use of large, complex molecules of food, they have to undergo 5. The is also known as the gullet. 6. prevent the body from losing too much heat. Human Digestive System 41

answer; //the above statement is (false);

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: