Biodiversity

a summary for A Level Biology

Classification of the domestic cat

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Carnivora

Family Felidae

Family Felidae

Genus Felis

Species Felis catus, the domestic cat

Classification of the domestic cat

The five kingdom system

• Until the mid-twentieth century all living organisms were classified in either the Animal Kingdom or the Plant Kingdom

• This led to numerous inconsistencies and absurdities (e.g. bacteria classified as ‘plants’)

• Since the 1960s most biologists have recognised five kingdoms: Prokaryota (Monera), Protoctista, Fungi, Plantae and Animalia

Kingdom Prokaryota (Monera)• All prokaryotic unicells: cells may form groups or

chains, but there is little or no differentiation between them

• Include the bacteria, the cyanobacteria and the archaea:

Nostoc

Sulfolobus

Kingdom Prokaryota (Monera)

• Genetically the bacteria are more different from the archaea than from animals or plants: some biologists propose a three-domain classification, with the Archaea, the Bacteria and the Eukarya having equal ‘domain’ status

The three-domain system

The Prokaryota would comprise two of the domains …the Protoctista contains a wide range of eukaryotes …

with the Plantae, Animalia and Fungi three relatively similar groups.

Kingdom Protoctista

• As we saw in the previous slide, the Protoctista contains a wide range of very diverse organisms

• All are eukaryotic; most are unicellular, and those that are multicellular (e.g. brown or red seaweeds) show very limited cellular differentiation

Kingdom Protoctista

• ‘Animal-like’ Protoctists are often called Protozoa :

Paramecium, a ciliate protozoan

Euglena, a flagellate protozoan

Amoeba, a rhizopod protozoan

Kingdom Protoctista

• ‘Plant-like’ Protoctists are often called Algae :

Chlorella, a ‘green alga’

Assorted phytoplankton

Assorted dinoflagellates

Kingdom Fungi• Fungi are eukaryotic heterotrophic organisms

with cell walls containing chitin and other polysaccharides as well as cellulose

• Typically a fungus consists of a mycelium composed of cylindrical hyphae, which may be multinucleate

• Nutrition is always heterotrophic, either saprobiontic or parasitic

• Reproduction is by production of sexual or asexual spores

Kingdom FungiFalse-colour scanning electron micrograph of Penicillium

Green: hyphae, making up the mycelium

Orange: spore-bearing hyphae (conidiophores)

Blue: asexual spores (conidia)

Kingdom FungiHigher fungi often produce their spores in organised structures called fruiting bodies: these include mushrooms, toadstools, brackets, puffballs etc

Death cap, Amanita phalloides

Shaggy ink cap, Coprinus comatus

Giant puffball, Lycoperdon gigantica

Kingdom Plantae

• Multicellular photoautotrophic eukaryotes• Cell walls contain cellulose• Some cells at least contain chloroplasts

(except in some plant parasites like broomrape or dodder, which have lost them)

Kingdom Animalia

• Multicellular heterototrophic eukaryotes• Cells without cell walls• Usually motile, at least at some stage in the life

cycle• Nutrition is characteristically holozoic• All except sponges show nervous coordination