Astudent wanted to know the most effective way to grow bacteria in a lab. he conducted a descriptive investigation instead of an experimental investigation. what is a limitation of his investigation? a descriptive investigation cannot show a cause-and-effect relationship between bacteria growth and possible factors affecting growth. a descriptive investigation is always more expensive than an experimental investigation. a descriptive investigation usually does not involve much data collection to support a hypothesis. a descriptive investigation provides little prior knowledge or background information about bacteria growth.

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: