AQA · GCSE · Combined Science

Course version: 8464 · Version from Sept 2018

Classification of living organisms: Evolutionary trees are a method used by scientists to show how they believe organisms are related. They use current classification data for living organisms and fossil data for extinct organisms.

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Q: Is this Classification of living organisms: Evolutionary trees are a method used by scientists to show how they believe organisms are related. They use current classification data for living organisms and fossil data for extinct organisms. guide aligned to the AQA specification?

Yes. This guide is linked to the Classification of living organisms: Evolutionary trees are a method used by scientists to show how they believe organisms are related. They use current classification data for living organisms and fossil data for extinct organisms. topic in the AQA GCSE specification.

Evolutionary trees are branching diagrams that represent scientists' best current ideas about how organisms are related through common ancestors.

3 key terms

Study notes

From the checked teaching notes for this specification point.

The idea

Evolutionary trees are branching diagrams that represent scientists' best current ideas about how organisms are related through common ancestors. Each branching point suggests a point where lineages diverged, and the tips usually represent present-day species or groups. To build these trees, scientists combine evidence: classification data from living organisms, such as physical features, DNA base sequences and biochemical similarities, plus fossil data from extinct organisms, including their age and structure. Fossils can show when particular body forms appeared, while molecular data can reveal how closely living species are related. Because new evidence may emerge, evolutionary trees are revised over time rather than being fixed.

What earns the marks

Evolutionary trees show proposed relationships and common ancestry between organisms.
Branching points represent divergence from a shared ancestor.
Current classification data from living organisms, including DNA and physical features, is used.
Fossil data from extinct organisms provides evidence about past life and timing.
Trees are based on scientific evidence and may be modified when new data is found.
The tips of a tree often represent existing species or groups, while internal branches represent ancestral lineages.

Common mistakes and how to put them right

Treating an evolutionary tree as a family tree of individuals.
Put it right: It shows relationships between species or larger groups over evolutionary time.
Assuming the tree is proven fact and never changes.
Put it right: It is a model based on current evidence and can be revised.
Thinking fossils are the only evidence used.
Put it right: Classification data from living organisms, especially DNA, is also essential.

Exam tips

State clearly that evolutionary trees show relationships and common ancestry.
Name both types of evidence: classification data for living organisms and fossil data for extinct ones.
Use terms such as common ancestor and branching when describing what the diagram shows.

Try the lesson

The start of the Classification of living organisms: Evolutionary trees are a method used by scientists to show how they believe organisms are related. They use current classification data for living organisms and fossil data for extinct organisms. lesson, made from checked teaching notes for this specification point.

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What is an evolutionary tree used by scientists to show?

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A top-down flowchart. A single node labelled Evidence splits into two nodes: Classification data for living organisms and Fossil data for extinct organisms. Both of these lead into a node labelled Evolutionary tree. From the Evolutionary tree node, three nodes branch out: Branching points: divergence from a shared ancestor; Tips: existing species or groups; and Revised when new evidence is found. — It shows how classification data from living organisms and fossil data from extinct organisms are combined to build an evolutionary tree, whose branching points and tips represent relationships and which may be revised as new evidence emerges.

Key words

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Evolutionary trees

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Evidence for classification

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Scientific models and their revision

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See every definition

Evolutionary trees: A method used by scientists to show how they believe organisms are related.
Evidence for classification: Current classification data for living organisms and fossil data for extinct organisms are used to build evolutionary trees.
Scientific models and their revision: Evolutionary trees are revised over time rather than being fixed because new evidence may emerge.

Label the diagram

Some boxes have lost their names. Pick the right name for each number.

The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. A single node labelled Evidence splits into two nodes: Classification data for living organisms and Fossil data for extinct organisms. Both of these lead into a node labelled Evolutionary tree. From the Evolutionary tree node, three nodes branch out: Branching points: divergence from a shared ancestor; Tips: existing species or groups; and Revised when new evidence is found.

1Box 1
2Box 2
3Box 3

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Study notes

The idea

What earns the marks

Common mistakes and how to put them right

Exam tips

Try the lesson

Have a go first

See it

Key words

Label the diagram

Test your understanding of Classification of living organisms: Evolutionary trees are a method used by scientists to show how they believe organisms are related. They use current classification data for living organisms and fossil data for extinct organisms.

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