Biological Classification & Endosymbiosis

Vocabulary flashcards covering key terms on biological classification, plasmids, organelle DNA, and the endosymbiotic theory.

Three-Domain System

Modern classification that divides all cellular life into Bacteria, Archaea, and Eukarya.

Proposed “In-Between Life” Domain

A suggested fourth grouping (often referring to acellular entities such as viruses) that does not fit neatly into the three-domain system.

Domain (Taxonomy)

The highest taxonomic rank, positioned above kingdom in biological classification.

Biological Classification

The process of organizing organisms into hierarchical groups based on shared traits; visible traits make classifying macroscopic life (e.g., humans vs. fish) straightforward.

Plasmid

A small, circular, self-replicating DNA molecule commonly found in bacteria and certain organelles.

Circular DNA

DNA that forms a closed loop; characteristic of bacterial chromosomes, plasmids, mitochondria, and chloroplasts.

Mitochondrion

ATP-producing eukaryotic organelle that contains its own circular DNA resembling bacterial plasmids.

Chloroplast

Plant organelle that performs photosynthesis and possesses independently replicating circular DNA.

Autonomous Replication

The ability of a DNA molecule to replicate without depending on the host cell’s chromosomal DNA replication machinery.

Endosymbiotic Theory

The idea that mitochondria and chloroplasts originated as free-living bacteria engulfed by ancestral eukaryotic cells, trading ATP or photosynthesis for a protected habitat.