IGCSE Biology 0610
1.2 Concept and uses of classification systems
- Organisms can be classified into groups by the features that they share
- A species is a group of organisms that can reproduce to produce fertile offspring
- The binomial system of naming species is an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species
Example: The scientific name of a lion is Panthera leo. The genus is Panthera and the species is leo
Dichotomous Keys
These are keys that are used to identify living things
Dichotomous means dividing into two
They can be either branching keys or numbered keys
They can have either questions or statements that are answered with “yes” or “no”
To use dichotomous keys, start at the beginning and answer “yes” or “no” to the first question/statement. This will take you to the next question or to an identification. Keep on answering the questions until you have reached an identification.
If you are tasked with constructing a dichotomous key, do NOT use size as a feature as size is relative
- Classification systems aim to reflect evolutionary relationships
- Sequences of bases in DNA are used as a means of classification
- Groups of organisms which share a more recent ancestor (are more closely related) have base sequences in DNA that are more similar than those that share only a distant ancestor