According to HowStuffWorks, some types of algae reproduce asexually through the division of one cell into two or even more new cells that are genetically similar to the original parent cell. Other types of algae engage in sexual multi-cellular reproductive cycles to procreate.
There are both single-celled and multicellular types of algae. As HowStuffWorks points out, in some types of single-celled algae, asexual reproduction occurs, which causes all genetic information to come from a single-parent cell, which it shares with the newly formed daughter cell. Asexual reproduction occurs by means of fission, in which a cell divides into two more cells. In other types of single-celled algae, the method of reproduction is sexual.
In multi-cellular algae, reproduction is done in both ways. Generally, one generation of algae will reproduce asexually, and the next will reproduce sexually. This is possible through the use of cells called spores and traditional gametes or sex cells, according to How Stuff Works.
Algae are a class of organisms that do not have roots, stems or leaves, but they usually have chlorophyll. HowStuffWorks explains that algae are capable of performing the process of photosynthesis, which is necessary to manufacture their own food and energy from light sources.