Taxonomy

Bio 250

History of Taxonomy• Taxonomy – the branch of biology which

names and groups organisms according to their characteristics

Aristotle

•First person to put organisms in groups. - Grouped animals into land, air or water dwellers.

•At first, Aristotle’s system seemed adequate.•When many new organisms were discovered, scientists began having problems. More groups were needed. Common names were different from place to place and caused confusion and did not describe the organism.

History of taxonomy cont.• Linnaeus created a new system of

grouping organisms.– Based on their morphology (structure)– Created 7 levels of classification– Also created a two-part naming

system called Binomial

Nomenclature.

Linnaeus

The 7 Levels of Classification

• Linnaeus devised seven levels of organization.

Kingdom: the largest group of living things.Phylum: The largest group within a kingdom.Class: The largest group within a phylum.Order: The largest group within a class.Family: Largest group in an order.Genus: Largest group in a family.Species: Smallest group of living things.

Wait.. What were those again?Kingdom

Phylum

Class

Order

Family

Genus

Species

No Looking!

Binomial Nomenclature

• The species name, also called the scientific name of an organism has two parts.– The Genus name– The species identifier– The Genus name is capitalized, the species

name is lower case and both are underlined or written in italics (typing only)

– Thus, our scientific name is written as such Homo sapiens or Homo sapiens.

The full scientific name of a species will contain the the names of each classification group the organism is in.

For Humans:Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Mammalia Order: Primata Family: Hominidae Genus: Homo species: sapiens

The Six Kindoms• All life on Earth has been divided into six

different kingdoms.• Kingdom Archaebacteria

– Unicellular prokaryotes– Cell membranes are different from other bacteria.– Many live in harsh environments.

• Kingdom Eubacteria:– Unicellular prokaryotes– These are the ones which affect you: tooth decay,

food poisoning, disease, create food products like yogurt.

The Six Kingdoms cont.• Kingdom Protista

– The catch-all Kingdom. If it’s eukaryotic and not a plant, animal or fungus, it’s in here.

– Mostly unicellular but do have some multicellular species.

– Some are plantlike and some are animalike.

The Six Kingdoms cont.• Kingdom Fungi

– Multicellular, eukaryotic, heterotrophic– Absorb nutrients – digest outside their body– Includes mushrooms, puffballs, rusts, smuts,

mildews, and molds

The Six Kingdoms cont.• Kingdom Plantae

– Multicellular, eukaryotic, autotrophic– Make their own food through photosynthesis– Include mosses, ferns, conifers, and flowering

plants

The Six Kingdoms cont.• Kingdom Animalia

– Eukaryotic, heterotrophic, multicellular– Can move around in their environment– Insects, mammals, reptiles, amphibians, fish,

birds, worms

The 3 Domain System• Scientists have added another classification

group ABOVE the level of Kingdom• Molecular biology has shown that all organisms

naturally fall into 3 large groups which are called Domains– Domain Bacteria

• Contains the Kingdom Eubacteria

– Domain Archae• Contains the Kingdom Archaebacteria

– Domain Eukarya• Contains all Kingdoms with Eukaryotic cells• Protista, Fungi, Plantae, Animalia

Taxonomy• Systematics – Organizes the diversity of

living things in the context of evolution.– Creates a Phylogenetic Tree – A family tree

which shows the evolutionary relationships thought to exist among groups of organisms.

• A phylogenetic tree represents a hypothesis.• Scientists use morphology (structure), patterns of

embryological development, similarity in DNA and proteins to construct phylogenetic trees.

So how do we put all these organisms into

groups?Today, scientists use either Systematics or

Cladistics to put organisms into groups

based upon specific traits.

Taxonomy cont.• Cladistics – uses certain features of organisms

called shared derived characters to establish evolutionary relationships.– Derived Characters – are features that apparently

evolved only within the group under consideration.– Ex: If you’re studying birds, a derived character may

be feathers.– Scientists believe that if a group shares a character

not shared with any other group, then they likely inherited it from a common ancestor.

– Cladogram – Ancestry diagram made by means of cladistics.