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Species and taxonomy

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Question 9

The diagram shows two different methods of classifying three bear species: the brown bear (Ursus arctos), the polar bear (Ursus maritimus), and the American black bear (Ursus americanus).

  • Classification A is based on physical and observable structural characteristics.
  • Classification B is based on comparisons of genetic and molecular characteristics.

All three species belong to the family Ursidae.

Phylogenetic trees comparing classifications of three bear species. Classification A based on structural characteristics shows Ursus arctos and Ursus americanus on a sister branch, sharing a more recent common ancestor than with Ursus maritimus. Classification B based on genetic characteristics shows Ursus arctos and Ursus maritimus on a sister branch, sharing a more recent common ancestor than with Ursus americanus.

1.

What do these classifications suggest about the evolutionary relationships between these species of bear?

[2]
2.

Identify the five missing taxa (1 to 5) in order for the classification below:

    1. [Blank] | Eukaryote
    1. [Blank] | Animal
    1. [Blank] | Chordata
    1. [Blank] | Mammalia
    1. [Blank] | Carnivora
  • Family | Ursidae
[5]
3.

There is an ongoing scientific discussion about the classification of the polar bear. Some taxonomists classify it as Thalarctos maritimus, while others classify it as Ursus maritimus. State the name of the taxon about which these scientists disagree.

[1]
4.

State three comparisons of genetic diversity that scientists use to generate Classification B.

[3]

Species and taxonomy Questions

  1. A Level
  2. /Biology
  3. /Species and taxonomy

Practise AQA A Level Biology Species and taxonomy with exam-style questions for A Level Biology. 12 questions, matched to the AQA A Level Biology (7402) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.

Question bank