A Level CIE Biology: 18 Classification, Biodiversity & Conservation

species (biological species concept)

a group or organisms with similar morphological and physiological features that able to breed together and produce fertile offspring

biological species concept

reliant on determining whether inbreeding produces fertile offspring - difficult and time consuming to determine in practice. other discriminating factors that scientists can use to group similar orgs together

morphological species concept

• scientists described by physical features and group together orgs that share many physical features that distinguish them from other species.

ecological species concept

• when there’s a population of similar orgs living in same area at the same time, they can be described as an ecological species

taxonomy

practice of biological classification involving placing orgs into series of categories/taxa to make it easier to see evolutionary relationshisp between orgs.

domain

highest rank of hierarchical classification

cell types (major) role in classification of orgs into the 3 domains

• prok cells easily distinguishable in that they lack a nucleus

• euk cells have compartmentalised structures, w at least their genetic material segregated from rest of cell in a nucleus

• prok are divided into 2 separate groups based on molecular analysis of rna genes proving cell type insufficient classification

3 domains:

• archaea (prok)

• bacteria (prok)

• eukarya (euk)

archaea features 9

• single-celled/unicellular orgs

• sometimes extremophile prokaryotes (live in extreme environments but not all)

• no nucleus

• not bacteria bc: 3

  • unique lipids in membranes of cells

  • no peptidoglycan in cell walls

  • ribosomal structure (particularly that of small subunit) more similar to euk ribosome than bac

• similar size range

• dna transcription similar to euk

• e.g. haloboacterium salinarium (dead sea)

bacteria features 5

• single-celled/unicellular

• prok no nucleus

• vary in size over wide range (smallest are bigger than alrgest known viruses and largest smaller than singlecelled euk

• divide by binary fission

• e.g. streptococcus pneumoniae

eukarya features

• orgs w euk cells w nuclei and memb-bound organelles placed in this domain

• vary massively in size from single-celled orgs several micrometres across to large multicellular orgs many metres in size e.g. blue whales

• euk cells diivde by mitosis

• euks can reprod sexually or asexually

• e.g. canis lupus

3 main diffs between archaea and bacteria

• membrane lipids

• ribosomal rna

• cell wall composition

membrane lipid differences 3

• archaras are completely unique, memb lipids consist of brancched hydrocarbon chains bonded to glycerol by ether linkages

• memb lipids of bacteria unbranched hydrocarbon chains bonded to glycerol by ester linkages

• not in bacterial or euk cells

ribosomal rna differences 4

• both archaea and bacteria posses 70s ribosomes

• 70s ribs in archaea possess a smaller subunit similar to subunit in euk rib than sub in bac

  • base sequences of ribosomal rna in archae more similar to rRNA of eukarya

  • prim structure of ribosome proteins in archae more sim to ribosome proteins in eukarya than bacteria

composition of cell walls differences

• bacteria always peptidoglycan

• archaea always cell walls but not peptidoglycan

archaea: cell type, chromosome, cell memb lip, ribosome, cell walls, histones, introns

• prok

• circular

• glycerol - ether lipids

• 70s ribs but small subunit more similar to euk ribs

• always present w/o peptidoglycan

• yes

• sometimes

bacteria: cell type, chromosome, cell memb lip, ribosome, cell walls, histones, introns

• prok

• circ

• glycerol - ester lipids

• 70s ribs

• always present w peptidoglycan

• no

• rarely

euk: cell type, chromosome, cell memb lip, ribosome, cell walls, histones, introns

• euk

• linear chromosomes + circular mtDNA and cpDNA

• glycerol - ester lipids

• large 80s ribosomes in cytosol and 70s ribosomes in mitoch and chloro

• sometimes present w/o peptidoglycan

• yes

• yes

hierarchical classification system of organisms

used to organise and group similar organisms together so that evolutionary relationships between orgs more easily understood

7 taxonomic ranks (domain highest, species lowest)

• similar species grouped in genus

• similar genuses grouped in family

• similar fams grouped in order

• similar orders grouped into class

• similar classes grouped into phylum

• similar phyla can be grouped into kingdom

• similar kingdoms can be grouped into domain

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