Bio Review Notes

Bio Review Notes #67
ORGANIC DIVERSITY AND ITS CLASSIFICATION Performance Objectives:

After completing this lesson, students will be able to:

Describe how evolution results in organic diversity

Describe how biologists classify species into taxonomic groups

Describe some of the modern methods used to construct family trees and classifications

Biological diversity is expressed by arranging organisms into kingdoms, phyla, classes, orders, families, genera, and species. These groups reflect evolutionary history and common ancestry as much as possible. Evolutionary relationships responsible for these arrangements are often depicted in family trees.

Binomial nomenclature: Each species has a two-word name. The first word (capitalized) is the name of the genus; the second (lower case) is the name of the species. Example: Homo sapiens.

The Linnaean system: Uses binomial nomenclature throughout. Species are grouped into genera and genera into higher groups. Any one of these groups, at any level, is called a taxon (plural, taxa). The complete Linnaean hierarchy (ranking) of groups is as follows:
Kingdom (the most inclusive group)
Phylum (plural, phyla, sometimes called a "division" in plants)
Class
Order
Family
Genus (plural, genera)
Species (same spelling in both singular and plural)
(Mnemonic: "King Philip Came Over For Good Soup")
Extra ranks are added to this hierarchy as needed, such as subphylum (just below phylum) or superfamily (just below family).
Example: Humans belong to the Kingdom Animalia, Phylum Chordata, subphylum Vertebrata, class Mammalia, order Primates, family Hominidae, genus Homo, species Homo sapiens.

Evolutionary (phylogenetic) classification: Biological classification reflects the results of a branching evolutionary process. Insofar as possible, classifications should be genealogical. Each taxon should ideally represent one branch of the evolutionary tree, with the smaller included taxa representing its sub-branches.

Three domains and six kingdoms: Most biologists now arrange organisms into three domains containing six kingdoms:

Domain Archaea contains only the Kingdom Archaebacteria, a group of oxygen-intolerant procaryotes with RNA sequences different from those of all other organisms.
Domain Bacteria (or Eubacteria) contains only a single kingdom of the same name, including the majority of procaryotes.
Domain Eucarya contains four kingdoms of eucaryotes:
1. Kingdom Protista: Simple eucaryotes, generally one-celled, containing neither tissues nor embryos
2. Kingdom Mycota: Fungi, with cell walls but no plastids.
3. Kingdom Plantae: Plants, containing plastids and chlorophyll.
4. Kingdom Animalia: Multicellular animals, developing from blastulas.

Index Syllabus

rev. Aug. 2011