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the science of naming and grouping organisms by their evolutionary relationship

Carolus Linnaeus

1730—Swedish botanist developed binomial nomenclature—a classification system that organized species into a hierarchy, or ranking.

Bionomial Nomenclature

in binomial nomenclature, each species is assigned a two-part scientific name


Large groups that living and fossil species are grouped into. They have biological meaning.

Dichotomus Key

used to identify organisms—consists of a period of statements or questions that describe alternative possible characteristics of an organism—sometimes describe either the presence or absence of a characteristic or structure


the study of how living and extinct organisms are related to one another


a group of species that includes a single common ancestor and all descendants of the ancestor—living and extinct

Monophyletic Group

must include all species that are descended from a common ancestor, and cannot include any species that are not descended from that common ancestor


shows how species and higher taxa are related to one another by showing how evolutionary lines, or lineages, evolved and branched off from common ancestors over time.

Derived Character

a trait that arose in the most recent common ancestor of a particular lineage and was passed along to its descendants.

Six-Kingdom Classification

1. Eubacteria
2. Archaebacteria
3. Protista
4. Fungi
5. Plantae
6. Animalia


a larger, more inclusive category than a kingdom, 3 domains

Domain Bacteria

- Unicellular and prokaryotic, corresponds to the kingdom Eubacteria
- Their cells have thick, rigid walls, that surround a cell membrane and contain a substance known as peptidoglycan
- These bacteria are ecologically diverse, ranging from free-living soil organisms to deadly parasites. Some photosynthesize, some need oxygen to survive, while others are killed by oxygen

Domain Archaea

- Archaea corresponds to the kingdom Archaebacteria
- Unicellular, and prokaryotic, and they live in some extreme environments—in volcanic hot springs, brine pools, and black organic mud totally devoid of oxygen
- Their cell walls lack peptidoglycan, and their cell membranes contain unusual lipids that are not found in any other organism

Domain Eukarya

- Consists of all organisms that have a nucleus
- It comprises the four remaining kingdoms of the six-kingdom system: Protista, Fungi, Plantae, and Animalia


has long been viewed by biologists as a "catchall" group of eukaryotes that could not be classified as fungi, plants, or animals. Recent molecular studies and cladistic analyses have shown that the eukaryotes formerly known as Protista do not form a single clade. Current cladistic analysis divides these organisms into at least five clades. Most protists are unicellular, but one group, the brown algae, is multicellular. Some protists are photosynthetic, while others are heterotrophic. Some display characters that resemble those of fungi, plants, or animals


Heterotrophs with cell walls containing chitin. Most fungi feed on dead of decaying organic matter. The secrete digestive enzymes into their food source, which break the food down into smaller molecules. The fungi then absorb these smaller molecules into their bodies. Mushrooms and other recognizable fungi are multicellular. Some fungi are unicellular—yeasts


multicellular, have cell walls that contain cellulose, and are autotrophic. Able to carry on photosynthesis using chlorophyll, plants are nonmotile—they cannot move from place to place. The plant kingdom includes the green algae along with mosses, ferns, cone-bearing plants, and flowering plants


Members of the kingdom Animalia are multicellular and heterotrophic. Animal cells do not have cell walls. Most animals can move about, at least for some part of their life cycle. There is incredible diversity within the animal kingdom, and many species of animals exist in nearly every part of the planet

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