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.
Specimens can also be compared with field guides and with type specimens and reference collections in museums and herbaria.When organisms look alike, or only part of an organism is available (such as a larva, a hair or a leaf fragment), DNA or protein sequences can be compared with those of known species. This can show that organisms that look identical are separate cryptic species.If an organism does not match any known species, it may be a new species. Before it is accepted, the taxonomist must:
• describe its features in detail and compare it with close relatives, using morphological and often DNA evidence
• give it a new binomial name
• deposit a type specimen in a museum collection
• publish the description in a peer-reviewed scientific journal, so that other experts can check the evidence and conclusions.This process means new species are validated by the scientific community, not by one scientist alone.
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.
Specimens can also be compared with field guides and with type specimens and reference collections in museums and herbaria.When organisms look alike, or only part of an organism is available (such as a larva, a hair or a leaf fragment), DNA or protein sequences can be compared with those of known species. This can show that organisms that look identical are separate cryptic species.If an organism does not match any known species, it may be a new species. Before it is accepted, the taxonomist must:• describe its features in detail and compare it with close relatives, using morphological and often DNA evidence
• give it a new binomial name
• deposit a type specimen in a museum collection
• publish the description in a peer-reviewed scientific journal, so that other experts can check the evidence and conclusions.This process means new species are validated by the scientific community, not by one scientist alone.