Identifying & Classifying

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Learning Intentions

By the end of this topic, you should be able to:

Describe what identifying and classifying mean in science and explain how they help organise information.
Apply classification systems and use tools such as dichotomous keys to identify and group objects or organisms.
Explain why identifying and classifying are important for scientific understanding and communication, including perspectives from te ao Māori.
Evaluate the advantages and limitations of classification systems, and recognise how these systems can change as new discoveries are made.

Glossary

Key terms and definitions.

category: A group of items or organisms that share similar characteristics or features.

characteristic: A feature or quality that can be used to describe or identify something.

classifying: The process of sorting or grouping things based on shared characteristics to make them easier to study and understand.

criteria: The rules or standards used to decide how things are grouped or identified.

dichotomous key: A tool that helps identify organisms or objects by answering a series of questions that lead to the correct name or group.

identifying: The process of recognising and naming something based on its observed characteristics.

observing: Using the senses or tools to carefully notice and record details about objects, organisms, or events.

whakapapa: The concept that all living and non-living things are connected through ancestry and relationships.

What is identifying and classifying?

Turning ideas and thoughts into scientific knowledge involves a process called investigating. Identifying and classifying are important ways that scientists investigate and learn about the world around them.

Identifying means recognising and naming something based on its features or characteristics. For example, you might identify a tree as a kauri by noticing its smooth bark and large, flat leaves.
Classifying means sorting or grouping things that share similar features into categories. This helps to organise information and make complex systems easier to understand. For example, a biologist might classify animals into groups such as mammals, birds, reptiles, fish, and amphibians.

To classify correctly, scientists use criteria — clear rules or characteristics that define how things should be grouped. These criteria might include physical traits, chemical properties, genetic makeup, or even behaviour. Scientists often use keys, such as dichotomous keys, to help them decide which group an organism or object belongs to.

How do we investigate by identifying and classifying?

When scientists carry out an investigation using identifying and classifying, they are often trying to find patterns or relationships between things. The process usually involves several steps: observation, listing features, grouping, naming or identifying, and refining.

Example: Identifying and classifying leaves

If you are investigating leaves from different plants, you might group them by shape, edge pattern, or leaf arrangement. Once grouped, they can identify which species they belong to using a plant identification key.

Scientists in many fields use similar approaches. Astronomers classify stars by brightness and temperature. Chemists classify elements in the Periodic Table by their atomic number and properties. Geologists classify rocks by how they form. In all cases, classification helps reveal patterns and relationships that might not be obvious at first glance.

Example: Chemistry

Organising elements into the Periodic table.

Example: Biology

Classifying animals into groups like mammals, birds, reptiles etc.

Example: Earth Science

Classifying rocks as igneous, sedimentary or metamorphic.

Example: Astronomy

Sorting stars by brightness and colour.

How have classification systems changed over time?

Scientific classification systems are not fixed — they evolve as new discoveries are made.

Early scientists once divided all living things into just two kingdoms: plants and animals. However, as microscopes improved, scientists discovered micro-organisms that didn’t fit neatly into either category. This led to the creation of new groups and eventually to the five-kingdom system, which includes Monera, Protista, Fungi, Plantae, and Animalia.

Today, even that system is being refined as scientists study DNA. Genetic evidence has revealed that some groups thought to be similar are actually very different. This has led to the development of the three-domain system (Bacteria, Archaea, and Eukarya).

Changing classification systems show how science is a process of ongoing discovery. When criteria are changed, new groupings may emerge — sometimes leading to brand new understandings of how life or matter is organised.

Why is identifying and classifying important?

Identifying and classifying are essential because they bring order to the complexity of the natural world. By sorting and naming things, scientists can better understand how they relate to one another. For example:

In biology, classification helps scientists understand how species are related through evolution.
In chemistry, the classification of elements helps predict their behaviour in reactions.
In astronomy, classifying stars and galaxies helps scientists understand the structure and age of the universe.

Classification also allows scientists to communicate clearly. A scientist in New Zealand and another in Japan can both understand what “Homo sapiens” means because scientific names and systems are shared worldwide.

From a te ao Māori perspective, identifying and classifying can also be understood through whakapapa — the idea that all living and non-living things are connected through ancestry and relationships. This provides another way of grouping and understanding the world that values relationships, connections, and balance.

What are the advantages and limitations of identifying and classifying?

Like all scientific methods, identifying and classifying have both strengths and weaknesses.

Advantages

Identifying and classifying have many advantages:

Helps to organise large amounts of information into meaningful systems.
Reveals relationships and patterns between different things.
Makes communication and research more precise and consistent.
Can lead to new discoveries when patterns don’t fit existing systems.

Limitations

However, there are also some limitations:

Classifications are based on current knowledge — they may change as new discoveries are made.
Some things don’t fit neatly into one category, especially when features overlap.
The system chosen depends on the criteria used; changing the criteria can change the results.
Cultural perspectives may classify things differently, meaning there isn’t always one “right” way to group or name things.

More on Identifying & Classifying

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