1.2 Concept and uses of classification systems

Objective: State that organisms can be classified into groups by the features that they share.

Classification is the process of grouping organisms together based on their similarities and differences. This helps us understand the relationships between different species and organize the vast diversity of life on Earth. Organisms can be classified into groups based on shared characteristics, such as physical features, genetic makeup, or evolutionary history.

Why is classification important?

Classification provides a system for organizing and identifying organisms. This is crucial for:

• Understanding the evolutionary relationships between organisms.
• Communicating about organisms clearly, using a universal naming system.
• Predicting characteristics of organisms based on their classification.
• Studying the distribution of organisms in different environments.

How are organisms classified?

Organisms are classified using a hierarchical system, meaning they are grouped into progressively smaller and more specific categories. The main levels of classification are:

1. Domain
2. Kingdom
3. Phylum
4. Class
5. Order
6. Family
7. Genus
8. Species

This system is often remembered using the mnemonic "Dear King Philip Came Over For Good Spaghetti".

Examples of Classification

Consider the classification of animals:

Level	Example
Domain	Eukarya
Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Primates
Family	Hominidae
Genus	Homo
Species	Homo sapiens

This shows how a human is classified, starting from the broad domain Eukarya and becoming increasingly specific to the species Homo sapiens.

Features used in classification

Scientists use various features to classify organisms. These features can include:

• External features: These are visible characteristics like body shape, color, and the presence of features like wings or fins.
• Internal features: These are characteristics found inside the organism, such as the type of tissues, organs, and systems.
• Genetic features: This involves comparing the DNA or other genetic material of different organisms to determine their relatedness.
• Embryological features: Comparing the development of embryos can reveal evolutionary relationships.

By comparing these features, scientists can determine how closely related different organisms are and group them together into appropriate categories.

Suggested diagram: A simple classification hierarchy