ORGANIZING BIODIVERSITY

A SPECIES How do we define a species? A reproductive population that occupies a specific niche (plays a role) in nature Individuals within a species share DNA with other individuals within that species, but not outside of it Usually look similar, but not always

SAME SPECIES? Eastern MeadowlarkWestern Meadowlark

SAME SPECIES? Chihuahua Tiny dog Great Dane St Bernard

HOW ARE THESE ANIMALS RELATED? Horse Donkey Mule (and chicken)

A species is a “reproductive community” (?) – a bunch of living things - that occupy a specific niche in nature. They share DNA with each other (i.e. “interbreed”) and not other species. Some species show such a wide range of phenotypic variations that it is not initially obvious that they share a common gene pool. Mules are sterile and cannot reproduce. They are therefore not considered a species – they are hybrids.

Systematics Systematics is the branch of biology that deals with classifying living things, both current and prehistoric. There are three components: Taxonomy –describing and naming new taxonomic groups Classification – organizing information about organisms by arranging them into a hierarchical system Phylogenetics – determining the evolutionary history and relationships among the various forms of life through time. Relationships among organisms are expressed through diagrams known as cladograms.

THE EVOLUTION OF THE BIOLOGICAL CLASSIFICATION SYSTEM

ARISTOTLE ( BCE) created the first widely used classifications system by dividing all organisms into two groups; plants and animals.

Carolus Linnaeus ( ) developed the hierarchical categorization system: Kingdom Phylum Class –Order Family Genus Species grouped organisms based on their resemblance to other life forms

Linnaeus Developed the binomial nomenclature system of naming organisms, that is still in use today The first word of the 2-word name is the Genus name The second word is the species name Eg. Homo sapiens (genus is capitalized, species is not)

Anton van Leeuwenhoek ( ) Invented the light microscope led to the discovery of a great number of single-celled organisms. – Kindgom Protista.

Electron microscope --mid 1900’s Led to the discovery of two different types of cells; prokaryotes (bacteria) and the eukaryotes(plants, animals, fungi, protists) five kingdom system 1959: Plants Animals Fungi Protists Monerans (Bacteria)

Carl Woese (1970s) Analysis of the base sequence of ribosomal RNA in various bacteria led him to suggest that bacteria be subdivided into two distinct groups, the eubacteria and archaebacteria At first, a six kingdom system was suggested: Kingdom Monera was split into 2 – Kingdom Eubacteria (true bacteria) and Kingdom Archaebacteria

What was the difference that caused the split? BacteriaArchaea Antibiotics kill themNot killed by antibiotics HeterotrophsAutotrophs One kind of RNASeveral kinds of RNA Differences in what cell walls are made of

In 1990, Woese proposed the now widely accepted, three domain scheme of classification consisting of:

Domain Archaea (ancient bacteria – think “archaic”) consists of anaerobic bacteria that live in extreme environments such as high temperature or extreme salinity (salty), acidic environments, or produce methane gas They are all unicellular prokaryotes Domain Bacteria – “true” bacteria including E.coli, Lactobacillus bulgaris, S. aureus (MRSA) – these are different from Archaea in that their cell walls contain different proteins. Unicellular, prokaryotes

What about the Kingdoms for the bacteria domains? Conflicting information online: The original bacteria kingdom, Kingdom Monera, is no longer really a kingdom Domain Archaea – Kingdom Archaea Domain Bacteria – Kingdom Bacteria/Eubacteria Kingdom names are no longer being used in either domain m

Eukarya Domain Eukarya – most advanced – contain eukaryotic cells having nuclei and organelles such as mitochondria and chloroplasts

Traditional classification was based on similarities in morphology (structures) among species The fossil record, homologous structures, and embryology determined relationships between organisms Current classifications use knowledge of evolutionary relationships. This method is called cladistics – it uses cladograms (branching diagrams based on ancestral traits)

Phylogenetic trees are also used… netic_tree.svg