Classification
Biology: Cambridge International GCSE Supplement, topic 1.2.1
Classification
Classification is the grouping of organisms by comparing their similarities and differences. This is normally done to reflect the evolutionary relatedness between different species.
Species
- Species is the smallest classification of organisms.
- A species is defined as a group of organisms that can reproduce to have fertile (able to reproduce) offspring (children).
- Humans (Homo sapiens) and emperor penguins (Aptenodytes forsteri) are examples of species.
Traditional classification
- Organisms were first classified according to similarities in morphology (structural features such as shape and pattern) and anatomy (internal structure such as organ layout).
- The Linnaean classification system is based on this.
New classification
- Technological advancements have led to new, more accurate classification systems.
- These systems are based on sequencing the DNA (genetic material) and proteins of organisms.
- More closely-related organisms have DNA with a more similar base (small units within DNA) sequence, and proteins with a more similar amino acid (units that make up proteins) sequence.
Binomial system
- Scientists name organisms using a binomial naming system.
- Each organism has a two-part scientific name.
- The first part is the genus name.
- The genus name starts with a capital letter.
- The second part is the species name.
- The species name starts with a lowercase letter.
- Scientific names are written in italics or underlined.
- This system allows scientists worldwide to identify organisms clearly.
Limitations
- Classification helps scientists identify and study organisms.
- It allows easier comparison between different species.
- It helps understand evolutionary relationships.
- Classification systems can change with new evidence.
- Some organisms do not fit neatly into one group.
- Similar features do not always mean close relationships.