1. principles of classification

BIODIVERSITY

• a measure of the variety of organisms and their genetic differences

• earths biodiversity is reducing rapidly due to human activity

WHY CLASSIFY

• due to years of evolution, there’s huge variety

• an internationally recognised way of referring to a particular organism and identifying groups of organisms is required

• organisms are put into classification systems bases on similarities and differences which makes ancestral relationships clear

TAXONOMY

• science of describing, classifying and naming living things

• from time of Aristotle, people have put organisms based on their appearance (morphology)

• often use analogous features-ones which look similar or have the same function but not of the same biological origin

• valid classification system must be based on careful observation and use of homologous structures- ones which show common ancestry

• 18th century- Swedish botanist Carolus Linnaeus developed 1st classification system

• his principles and basic naming system still used today but more modern technology added

TAXONOMY- POINTS OF CLASSIFICATION

• CELL TYPE- either prokaryotic or eukaryotic

• CELL WALL STRUCTURE- material the wall is made of can be used to separate into groups (either cellulose, chitin or peptidoglycan)

• NO. OF CELLS- unicellular or multicellular

• MODE OF NUTRITION- autotrophic (make their own food by photosynthesis) or heterotrophic (consumes to get food)

  → heterotrophs can be classed as saprophytic (consumes dead or waste matter) and parasitic (nutrition at the expense of a host)

TAXONOMY- DOMAINS

• archaea

• bacteria

• eukaryota

TAXONOMY- ARCHAEA DOMAIN

• only 1 kingdom- archaebacteria (ancient bacteria thought to be related to eukaryotic cells)

• thought to be found in only extreme environments but they’re increasing being found everywhere- particularly soil

• cells walls- no peptidoglycan

• unicellular

• autotroph or heterotroph

• usually reproduce asexually

• e.g. halophiles

TAXONOMY- BACTERIA DOMAIN

• one kingdom- eubacteria (true bacteria and cyanobacteria)

• some can be pathogenic but many are useful in the digestive systems of organisms and in recycling nutrients

• cells walls- peptidoglycan

• unicellular

• autotroph or heterotroph

• usually reproduce asexually

• e.g. E. coli

TAXONOMY- EUKARYOTA DOMAIN

• 4 kingdoms- protista, fungi, plantae and animalia

TAXONOMY- PROTISTA

• very diverse group of microorganisms

• cell walls- cellulose (some have chloroplasts)

• unicellular or multicellular

• autotroph or heterotroph

• usually reproduce asexually

• e.g. amoeba

TAXONOMY- FUNGI

• cell walls- chitin

• most multicellular, some unicellular

• heterotroph- most saprophytic, some parasitic

• reproduce both asexually and sexually

• e.g. mushrooms

TAXONOMY- PLANTAE

• cell walls- cellulose (have chloroplasts)

• multicellular

• autotroph (using chlorophyll)

• reproduce both asexually and sexually

• e.g. mosses

TAXONOMY- ANIMALIA

• no cell walls or chloroplasts

• multicellular

• heterotrophs that move their bodies around during at least 1 stage of their life cycle

• mainly reproduce sexually, but come can reproduce asexually (parthenogenesis)

• e.g. invertebrates (insects) and vertebrates (mammals)

TAXONOMIC GROUPS

• kingdom

• phylum

• class

• order

• family

• genus

• species

• each group within the hierarchy is known as taxon

LINNAEUS

• over 200 years ago

• devised a universal system from naming organisms

• based on latin names

• binomial system

• generic (genus) name and specific (species) name

BINOMIAL NAMES

• use italics

• Genus- capital letter

• species- lower case

GENUS

• genus is a group of species that share common features

• have many similarities but different species as they have enough different features to tell them apart