5.3 Classification of Biodiversity

Binomial Nomenclature

According to the binomial system, every organism has a two-part scientific name:

* Genus is written first and is capitalised (e.g. *Homo*).
* Species follows in lower case (e.g. *Homo sapiens*).

Domains of Life

All living organisms are classified into one of **three domains:**

* **Eukarya** (all __eukaryotic__ organisms).
* **Archaea** (__prokaryotic__ extremophiles).
* **Eubacteria** (common pathogenic __bacteria__).

Taxonomy

Science of **classifying organisms** based on shared **characteristics** (or taxa).

* More taxa shared = more closely related organisms

Natural Classification

**Grouping** organisms according to **common ancestry** rather than by common characteristics.

* This allows for species to be **identified by their evolutionary pathways** and enables the prediction of traits within a group

Disadvantage of natural classification

Taxonomists may need to **reclassify groups** if new phylogenetic evidence emerges.

Dichotomous Keys

Involves **sequentially dividing organisms** into __two categories__ until every organism is individually identified.

Phylum

Taxonomic rank below kingdom (and above class)

Plant phyla

* Bryophyte: mosses
* Filicinophyte: Leaves with hairs
* Coniferophyte: Pine cones
* Angiosperms: Fruits, flowers

Animal phyla

* Porifera: Sponge
* Cnidaria: Jellyfish
* Platyhelminthes: Any worm
* Annelids: Tapeworm/store worm
* Molluscs: Molluscs
* Arthropods: Any insect, scorpions
* Chordates: **All vertebrate classes**