BRAINCAKEIdentifying a Species
To identify an organism, biologists first compare its features with known species. In the field this is often done with a dichotomous key. A dichotomous key is a series of questions, each offering two choices, that leads step by step to the name of the organism.
Worked example:
1. Legs present? Yes: go to 2. No: go to 3.
2. Six legs: insect. Eight legs: arachnid.
3. Body in rings (segments): earthworm. Body not segmented: slug.
An animal with eight legs follows 1 → 2 and is identified as an arachnid.
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Key terms in this lesson
- type specimen
- A preserved reference specimen of a species, kept in a museum, against which other specimens are compared and identified.
More in Classification
- Morphological Concept of Species
- Biological Concept of Species
- Other Species Models
- Limitations of Species Models
- DNA Barcode
- DNA Analysis and Proteomics
- New Evolutionary Models
- Biochemical Relationships
All 19 lessons in Classification · All Edexcel AS-level Biology topics