The event that gave rise to algae was the uptake of cyanobacteria that became chloroplasts. This process of engulfing microbes that then become parts of the eukaryotic cell is known as .

Endosymbiosis

Explanation:

Endosymbiosis is a theory developed to explain the origin of eukaryotic cells from a prokaryotic origin. Organelles of the eukaryotic cells such as mitochondria and chloroplast were thought to have developed from this process.

According to this theory, a proto-eukaryote eats up or engulf a proto-mitochondrion or protochloroplast (in form of microbes) to become eukaryotic organelles such as mitochondrion and chloroplast respectively.

B. Genetic Drift.

Explanation:

This is also called a small population because it is where a group of people are together instead of a large group.

This results in a loss of genetic variation because since there is only a small group of people, not a lot of people can have kids resulting in genetic variation.