Classification (Cambridge (CIE) A Level Biology): Flashcards
Exam code: 9700
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State the three species concepts used to define a species.
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State the three species concepts used to define a species.
The biological species concept
The morphological species concept
The ecological species concept
Define a species using the biological species concept.
A group of organisms with similar morphology and physiology that can interbreed to produce fertile offspring, and are reproductively isolated from other species.
Define the morphological species concept.
Organisms are classified as the same species based on their shared physical features (observable morphology and anatomy).
Define the ecological species concept.
A species is defined by the ecological niche it occupies — the role it plays in its environment.
Give one limitation of the biological species concept.
It cannot be applied to organisms that reproduce asexually, or to species known only from fossils (they cannot be tested for interbreeding).
Why can the biological species concept not be used to classify bacteria?
Bacteria reproduce asexually, so the test of interbreeding to produce fertile offspring cannot be applied.
The species concept groups organisms that can interbreed to produce fertile offspring.
The biological species concept groups organisms that can interbreed to produce fertile offspring.
Name the three domains into which all organisms are classified.
Archaea
Bacteria
Eukarya
Define the term domain.
The highest (broadest) rank in the taxonomic hierarchy, above kingdom.
The three-domain classification is based on differences in RNA.
The three-domain classification is based on differences in ribosomal RNA.
Which two domains are made up of prokaryotes?
Archaea and Bacteria are both prokaryotes.
State three features that differ between Archaea and Bacteria.
Membrane lipids
Ribosomal RNA
Composition of the cell walls
How do the cell walls of Bacteria and Archaea differ?
Bacterial cell walls contain peptidoglycan.
Archaeal cell walls do not contain peptidoglycan.
True or False?
Archaea and Bacteria have identical membrane lipids.
False.
Their membrane lipids differ — this is one of the key features used to separate the two domains.
List the taxonomic hierarchy of the Eukarya domain, from broadest to most specific.
Kingdom → Phylum → Class → Order → Family → Genus → Species
Define a taxon.
A group of organisms at any level within the classification hierarchy (e.g. a family or a genus).
Which is the broader taxon: a family or a genus?
A family is broader — it contains one or more genera.
In the taxonomic hierarchy, the rank immediately below family is the .
In the taxonomic hierarchy, the rank immediately below family is the genus.
The smallest and most specific taxon in the hierarchy is the .
The smallest and most specific taxon in the hierarchy is the species.
Which domain contains all organisms whose cells have a nucleus and membrane-bound organelles?
The Eukarya domain.
True or False?
A single genus may contain more than one species.
True.
A genus groups together one or more closely related species.
Outline the characteristic features of the kingdom Protoctista.
Eukaryotic; mostly single-celled (or simple multicellular).
A diverse group of organisms that do not fit into Fungi, Plantae or Animalia; some are autotrophic, some heterotrophic.
Outline the characteristic features of the kingdom Fungi.
Eukaryotic; cell walls made of chitin.
Heterotrophic (saprotrophic — absorb nutrients); may be single-celled (yeast) or made of thread-like hyphae; store food as glycogen; reproduce by spores.
Outline the characteristic features of the kingdom Plantae.
Eukaryotic and multicellular; cell walls made of cellulose.
Autotrophic — contain chlorophyll and photosynthesise; store food as starch.
Outline the characteristic features of the kingdom Animalia.
Eukaryotic and multicellular; cells have no cell wall.
Heterotrophic; store carbohydrate as glycogen; usually show nervous coordination.
The cell walls of organisms in the kingdom Fungi are made of .
The cell walls of organisms in the kingdom Fungi are made of chitin.
Organisms in the kingdom Plantae store their food reserves as .
Organisms in the kingdom Plantae store their food reserves as starch.
Which kingdom contains eukaryotes that do not fit into Fungi, Plantae or Animalia?
The Protoctista.
On which two features are viruses classified?
The type of nucleic acid — DNA or RNA
Whether the nucleic acid is single-stranded or double-stranded
State the four categories of viral nucleic acid.
Single-stranded DNA
Double-stranded DNA
Single-stranded RNA
Double-stranded RNA
Define a virus.
An acellular, non-living infectious particle consisting of a nucleic acid core (DNA or RNA) surrounded by a protein coat (capsid).
Why are viruses not placed in any of the three domains?
They are acellular (not made of cells) and non-living, so they do not fit the cellular classification system.
Viruses are classified according to the type and strandedness of their acid.
Viruses are classified according to the type and strandedness of their nucleic acid.
True or False?
All viruses contain DNA.
False.
A virus contains either DNA or RNA — never both — and this may be single- or double-stranded.
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