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cyanobacteria

serve as a food source for other organisms
are used for medicinal purposes
produce oxygen
perform nitrogen fixation
cause disease

serve as a food source for other organisms

are used for medicinal purposes

produce oxygen

perform nitrogen fixation

cause disease

Explanation:

Serve as a food source for other organisms: The cyanobacteria serves as a food for marine organisms like zooplanktons and fishes.

Are used for medicinal purposes: The cyanobacteria are used for the purpose of medicine these produced biologically active materials such as antiviral, antifungal, antibacterial and anticancer activities.

Produce oxygen: The cyanobacteria produces oxygen by the process of photosynthesis.

Perform nitrogen fixation: The Cyanobacteria produces nitrogen form that is absorbed by the plants. It converts the atmospheric nitrogen into the ammonia absorbed by the plants.

Cause disease: The cyanobacteria produces cytotoxin which is responsible for neurodegenerative diseases like Parkinson's disease, and  Alzheimer's disease.

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: