Biodiversity refers to the diversity of living organisms. Botany, rather than strictly plant biology, includes the study of many different groups of organisms. This section begins by discussing the organization (classification) and naming (taxonomy) of these groups based on their evolutionary history and genetic relatedness. The following chapters explore the wealth of diversity, beginning with the unicellular prokaryotes and acellular viruses. The other chapters cover eukaryotic groups that are often distinguished based on life cycles, morphology, nutritional mode, and cellular composition.
Fungi, officially classified in the same group as plants until 1969, are heterotrophic eukaryotes more closely related to animals. Other heterotrophic organisms once thought to be fungi, including the slime molds and water molds, are discussed in the Protists chapter. Protists include an unrelated assemblage of eukaryotes that simply don't fit in as plants, fungi, or animals. Some of these lineages engulfed photosynthetic organisms and gained chloroplasts. These include the brown algae and diatoms from one engulfing event, and the red algae and green aglae from another.
The red and green algae share their ancestors with land plants. These terrestrial, multicellular organisms can be divided into four major groups based on important evolutionary adaptations: bryophytes, seedless vascular plants, gymnosperms, and angiosperms. The angiosperms are the most diverse and most recent lineage, containing nearly 90% of all plant species. Unlike other plants, angiosperms make flowers and fruits.
Content by Maria Morrow, CC BY-NC