9700 · 18.1
Classification flashcards
Revision flashcards for Cambridge 9700 Classification (syllabus 18.1). Flip, recall, then mark a real past-paper question.
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What are the seven main taxonomic ranks in the Linnaean system, from broadest to most specific?
Kingdom, Phylum, Class, Order, Family, Genus, Species. A useful mnemonic is: King Philip Came Over For Good Soup.
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What is the binomial system of nomenclature?
A universal system that gives each species a unique, two-part Latin name. It consists of the Genus (capitalised) followed by the species (lowercase), with both parts written in italics (e.g., *Homo sapiens*).
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What is the biological species concept?
It defines a species as a group of similar organisms that can interbreed in nature to produce living, fertile offspring.
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State one major limitation of the biological species concept.
It cannot be applied to organisms that reproduce asexually (like bacteria), are known only from fossils (extinct), or in cases where distinct species can hybridise.
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What is morphology, and how is it used in classification?
Morphology is the study of the form and structure of organisms. Traditionally, it was the primary method for classification, grouping organisms based on similarities in their observable physical features.
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Why can relying solely on morphology for classification be misleading?
Because of convergent evolution, where unrelated species independently evolve similar features (analogous structures) in response to similar environmental pressures, which does not reflect a close evolutionary relationship.
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What two types of molecular evidence are most commonly used in modern phylogenetics?
1. DNA base sequences (from nuclear or mitochondrial DNA). 2. Amino acid sequences of proteins (e.g., cytochrome c).
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What is the principle behind using molecular evidence for classification?
The principle is that closely related species have more similar DNA and protein sequences because they share a more recent common ancestor. The number of differences can be used to estimate evolutionary distance.