4.2.2 classification Flashcards
what is taxonomy?
practise of biological classification which enables us to arrange species into groups based on their evolutionary origins and relationships
group organisms into taxa to make it easier to understand
different ranks within the classification
taxonomic rank in the system
domain
kingdom
phylum
class
order
family
genus
species
hierarchical classification system
the higher ranks contain more organisms with less similarity between them
the lower ranks contain fewer organisms with more similarity between them
what are the three different domains?
eukarya - eukaryotes
bacteria - prokaryotes
archaea - prokaryotes
what is eukarya?
the domain of all eukaryotes e.g. wolf
why do scientists classify organisms?
- To identify species – by using a clearly defined system of classification, the species an organism belongs to can be easily identified
- To predict characteristics – if several members in a group have a specific characteristic, it is likely that another species in the group will have the same characteristic
- To find evolutionary links – species in the same group probably share characteristics because they have evolved from a common ancestor
how to classify?
- Observable characteristics (gross and microscopic), biochemistry (DNA, proteins RNA)
- Separate organisms into three domains – archaea, bacteria and eukarya
- Move down the hierarchy there are more groups at each levels but fewer organisms in each group – these organisms become more similar and share more of the same characteristics
- Organisms are then classified as individual species – containing only one type of organism
what is a species?
a group of organisms that are able to reproduce to produce fertile offspring
binomial nomenclature
- Binomials are the scientific name given to individual specials. They consist of the organisms genus and species name in Latin e.g. Homo sapiens (must be italicised)
- This is useful for scientists as they allow for species to be universally identified
- Species are also given common names which differ between countries and translations as well as common overlaps
- The binomial nomenclature was developed by Linnaeus
- Scientific name consists of Genus + species e.g. Homo sapien
what are the 3 different domains?
eukarya - eukaryotes
bacteria - prokaryotes
archaea - prokaryotes
what is archaea?
- archaeal cells have no nucleus - prokaryotes
- unique lipids found in cell membrane
- no peptidoglycan in their cell walls
- ribosomal structure - similar to eukaryotes
- 70s ribosomes - RNA polymerase of different organisms contains between 8-10 proteins and is very similar to eukaryotic ribosome
- similar in size to bacteria
- DNA transcription is more similar to eukaryotes
what is bacteria?
- no nucleus - prokaryotic
- vary in size
- divide by binary fission
- 70s ribosomes - RNA polymerase contains 5 proteins
what is eukarya?
- 80s ribosomes - RNA polymerase (responsible for most mRNA transcription) contains 12 proteins
- have nuclei and membrane-bound organelles - eukaryotic
- vary in size
- divide by mitosis
- reproduce sexually or asexually
differences between archaea and bacteria
initially there was no archaea domain they were all classified as bacteria
differences include:
- membrane lipids
- ribosomal RNA
- cell wall composition
membrane lipids in archaea and bacteria
archaea - consist of branched hydrocarbon chains bonded to glycerol by ether linkages
bacteria - consist of unbranched hydrocarbon chains bonded to glycerol by ester linkages
ribosomal RNA in archaea and bacteria
both - 70S ribosomes
archaea - smaller subunit, base sequence of ribosomal RNA and primary structure of ribosome proteins are more similar to eukarya
composition of cell walls in archaea and bacteria
bacteria - cell walls with peptidoglycan
archaea - cell walls do not contain peptidoglycan
features of the domains: cell type
archaea: prokaryotic
eubacteria: prokaryotic
eukaryotes: eukaryotic
features of the domains: chromosomes
archaea: circular
eubacteria: circular
eukaryotes: linear chromosomes and circular mtDNA and cpDNA
features of the domains: cell membrane lipids
archaea: glycerol - ether lipids
eubacteria: glycerol - ester lipids
eukaryotes: glycerol - ester lipids
features of the domains: ribosomes
archaea: 70S ribosomes but small subunit
eubacteria: 70S ribosomes
eukaryotes: larger 80S in cytosol and 70S ribosomes in mitochondria and chloroplasts
features of the domains: cell walls
archaea: always present without peptidoglycan
eubacteria: always present with peptidoglycan
eukaryotes: sometimes present without peptidoglycan
features of the domains: histones
archaea: yes
eubacteria: no
eukaryotes: yes
features of the domains: introns
archaea: sometimes
eubacteria: rarely
eukaryotes: yes
what are the 5 kingdoms?
prokaryota
protoctista
fungi
plantae
animalia