What mistakes do students make with Species and taxonomy?

Describing a phylogenetic system as grouping organisms that look alike, which is the definition of a system based on observable characteristics. Assuming that convergent features, such as the streamlined body of a fish and of a dolphin, show close relatedness. Reading a tree from left to right and calling the right-hand taxon the most advanced or most evolved.

What are the exam tips for Species and taxonomy in Biology AQA A-Level?

In a justify question about a phylogenetic data set, write at least one point for and one point against, because a balanced answer is more likely to access all the available marks. Quote the named taxa and the figures from the diagram rather than writing 'the earlier group' and 'the later group'. Learn the distinction in one sentence: a phylogenetic system groups by ancestry, and the evidence for ancestry is sequence data.

AQA · A-Level · Biology

Course version: 7402 · Version from Sept 2016

A phylogenetic classification system attempts to arrange species into…

Full specification wording

Species and taxonomy: A phylogenetic classification system attempts to arrange species into groups based on their evolutionary origins and relationships.

A phylogenetic classification groups species by evolutionary history: organisms are placed together because they share a common ancestor.

Checked against the AQA 7402 specification (opens in a new tab) on 19 September 2026.

Point 4 of 9
2 key terms

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

State that groups are based on evolutionary origins and common ancestry rather than on similarity of appearance.
State that the more recently two species shared a common ancestor, the more closely related they are.
When reading a phylogenetic diagram, identify the most recent common ancestor shared by specific taxa to determine relatedness.
Identify a piece of data that does not fit a suggested trend, such as a taxon with an unexpected value compared to its close relatives.
Name the comparison of DNA base sequences, mRNA, or amino acid sequences as the evidence used to place groups.

Common mistakes and how to put them right

Describing a phylogenetic system as grouping organisms that look alike, which is the definition of a system based on observable characteristics.
Assuming that convergent features, such as the streamlined body of a fish and of a dolphin, show close relatedness.
Reading a tree from left to right and calling the right-hand taxon the most advanced or most evolved.
In a 'do the data support this?' question, giving only supporting points and losing the marks reserved for evidence against.
Saying one living species evolved from another living species rather than from a shared common ancestor.

Exam tips

In a justify question about a phylogenetic data set, write at least one point for and one point against, because a balanced answer is more likely to access all the available marks.
Quote the named taxa and the figures from the diagram rather than writing 'the earlier group' and 'the later group'.
Learn the distinction in one sentence: a phylogenetic system groups by ancestry, and the evidence for ancestry is sequence data.

Try the lesson

The start of the Species and taxonomy: A phylogenetic classification system attempts to arrange species into groups based on their evolutionary origins and relationships. lesson, made from checked teaching notes for this specification point.

Have a go first

What does a phylogenetic classification system use to arrange species into groups?

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Listen

A phylogenetic classification groups species by evolutionary history: organisms are placed together because they share a common ancestor. The more recently they shared that ancestor, the more closely related they are and the smaller the group they share. This differs from grouping by appearance alone, because similar features can evolve independently in unrelated organisms exposed to similar conditions. Phylogeny is usually drawn as a branching tree in which every branch point (node) is a common ancestor and the branches show the order in which lineages separated. Reading such a diagram is a key skill: relatedness is read from the position of the branch points, not from how close two names happen to sit on the page. Living taxa at the tips of the branches cannot be described as having evolved more or less recently than one another. A strong answer earns marks for these points. State that groups are based on evolutionary origins and common ancestry rather than on similarity of appearance. State that the more recently two species shared a common ancestor, the more closely related they are. When reading a phylogenetic diagram, identify the most recent common ancestor shared by specific taxa to determine relatedness. Identify a piece of data that does not fit a suggested trend, such as a taxon with an unexpected value compared to its close relatives. Exam tip: In a justify question about a phylogenetic data set, write at least one point for and one point against, because a balanced answer is more likely to access all the available marks.

See it

A flowchart starting from a box labelled 'Phylogenetic classification', which branches into two boxes: 'Groups based on evolutionary origins and relationships' and 'Not grouped by similarity of appearance'. The first of these leads to 'Common ancestry', which splits into 'More recently shared common ancestor means more closely related' and 'Phylogenetic tree: branch points are common ancestors'. The tree box then leads to two boxes: 'Relatedness read from position of branch points' and 'Living taxa at branch tips cannot be described as evolving more or less recently than one another'. The 'Not grouped by similarity of appearance' box leads to 'Similar features can evolve independently in unrelated organisms'. — It shows how a phylogenetic classification groups species by common ancestry rather than appearance, and how a branching tree is read.

Key words

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convergent similarity

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branching diagrams

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See every definition

convergent similarity: Similar features that can evolve independently in unrelated organisms exposed to similar conditions, so they do not show close relatedness.
branching diagrams: A tree in which every branch point is a common ancestor and the branches show the order in which lineages separated.

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 flowchart starting from a box labelled 'Phylogenetic classification', which branches into two boxes: 'Groups based on evolutionary origins and relationships' and 'Not grouped by similarity of appearance'. The first of these leads to 'Common ancestry', which splits into 'More recently shared common ancestor means more closely related' and 'Phylogenetic tree: branch points are common ancestors'. The tree box then leads to two boxes: 'Relatedness read from position of branch points' and 'Living taxa at branch tips cannot be described as evolving more or less recently than one another'. The 'Not grouped by similarity of appearance' box leads to 'Similar features can evolve independently in unrelated organisms'.

1Box 1
2Box 2
3Box 3

0 of 3 labelled

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