BIOLOGICAL CLASSIFICATION

The purpose of biological classification is to

1) Have a system of naming organisms that is accepted around the world.

2) Predict how living things are related to one another.

History of classification

1) Aristotle: ~ 350 BC. Divided living things into two kingdoms: “animals” (things that move) and “plants” (things that don’t move.

He further divided plants into three categories:

a) Herbs: small tender plants

b) Shrubs: medium plants with many woody trunks

c) Trees: large plants with one large trunk

Aristotle also placed animals into three categories:

a) Flying animals (birds, bugs, bats)

b) Swimming animals (fish, shellfish)

c) Crawling animals (land animals)

What are some problems with Aristotle’s system?

1735: Karl Linné devised a naming system of binomial nomenclature. Every organism received a first name and a last name. Most of these came from Greek or Latin.

First name: the genus (plural is genera)

A genus is a group of very similar organisms.

Last name is species. Two organisms are of the same species if

They can mate and produce a fertile offspring.

Example: The scientific name of a dog is

Canis familiaris. This includes all breeds of domestic dogs. A wolf is Canis lupus. Same genus, different species.

The scientific name is always underlined or written in italics. The genus is always capitalized, the species is never capitalized.

Linné further grouped all living organisms into smaller categories:

The categories go from general (Kingdom) to specific (species).

Kingdom: Today is based on

1) cell type and

2) nutritionAnimal: many cells, eating

Plant: many cells, makes own food

Fungus: many cells, absorbs nutrients

Protist: one cell with nucleus

Bacteria: one cell, no nucleus

Classification continues as follows:

Kingdom: animals

Phylum: Vertebrates (animals with backbones)

Class: Mammals (vertebrates that nurse young)

Order: Carnivore (mammals that eat meat)

Family: Felidae (cats)

Genus: Panthera (large cats that don’t purr)

Species: onca

The scientific name of this organism is Panthera onca

(jaguar)

An effective classification system will allow scientists to determine if organisms are related and if so, to what degree.