AQA · GCSE · Biology

    Course version: 8461 · Version from Sept 2018

    There is further evidence in the fossil record and the knowledge of how…

    Full specification wording

    Evidence for evolution: There is further evidence in the fossil record and the knowledge of how resistance to antibiotics evolves in bacteria.

    Two strong sources of evidence support evolution.

    Checked against the AQA 8461 specification (opens in a new tab) on .

    • Point 4 of 4
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Two strong sources of evidence support evolution. The fossil record shows organisms from the past, often different from living species, and the sequence of fossils in rock layers shows change over time. Antibiotic resistance in bacteria shows evolution happening quickly: random mutations produce some bacteria that are resistant, and when an antibiotic is used, these bacteria survive and reproduce while others die. The proportion of resistant bacteria increases, so the population evolves. Together, fossils show long-term change and antibiotic resistance shows natural selection in action, making the theory of evolution by natural selection well supported.

    What earns the marks

    • Fossils are preserved remains or traces of past organisms, and the fossil record shows that species have changed over time.
    • Older rock layers generally contain simpler or different organisms, while newer layers contain more recent forms, showing a sequence of change.
    • Antibiotic resistance evolves when random mutations produce resistant bacteria, and the antibiotic selects these bacteria by killing susceptible ones.
    • Resistant bacteria survive and reproduce, so the proportion of resistant bacteria in the population increases over generations.

    Common mistakes and how to put them right

    • Thinking that antibiotics cause mutations.

      Put it right: That mutations occur randomly and the antibiotic selects resistant bacteria.

    • Believing that resistance develops in a single bacterium during treatment.

      Put it right: That the population changes over generations as resistant bacteria reproduce.

    • Assuming the fossil record is complete.

      Put it right: That it is incomplete because many organisms do not fossilise or are not yet found.

    Exam tips

    • When explaining antibiotic resistance, state clearly that the antibiotic is the selection pressure.
    • Use the fossil record to describe change over time, and antibiotic resistance to describe natural selection in action.
    • Make the link to evolution explicit in your final sentence, for example by stating that the evidence supports the theory of evolution by natural selection.

    Try the lesson

    The start of the Evidence for evolution: There is further evidence in the fossil record and the knowledge of how resistance to antibiotics evolves in bacteria. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which of the following can scientists learn by studying the fossil record?

    Listen

    Two strong sources of evidence support evolution. The fossil record shows organisms from the past, often different from living species, and the sequence of fossils in rock layers shows change over time. Antibiotic resistance in bacteria shows evolution happening quickly: random mutations produce some bacteria that are resistant, and when an antibiotic is used, these bacteria survive and reproduce while others die. The proportion of resistant bacteria increases, so the population evolves. Together, fossils show long-term change and antibiotic resistance shows natural selection in action, making the theory of evolution by natural selection well supported. A strong answer earns marks for these points. Fossils are preserved remains or traces of past organisms, and the fossil record shows that species have changed over time. Older rock layers generally contain simpler or different organisms, while newer layers contain more recent forms, showing a sequence of change. Antibiotic resistance evolves when random mutations produce resistant bacteria, and the antibiotic selects these bacteria by killing susceptible ones. Resistant bacteria survive and reproduce, so the proportion of resistant bacteria in the population increases over generations. A common slip: Thinking that antibiotics cause mutations. Instead, that mutations occur randomly and the antibiotic selects resistant bacteria. Exam tip: When explaining antibiotic resistance, state clearly that the antibiotic is the selection pressure.

    See it

    A top-down flowchart. The first box says random mutations produce some resistant bacteria, and an arrow leads to a box saying antibiotic used. From that box two arrows branch out: one leads to a box saying the antibiotic kills susceptible bacteria, and the other leads to a box saying resistant bacteria survive. An arrow from resistant bacteria survive leads to a box saying resistant bacteria reproduce, then to a box saying the proportion of resistant bacteria increases over generations, then to a box saying the population evolves, and finally to a box saying this supports the theory of evolution by natural selection.
    It shows how random mutations and antibiotic selection lead to a rise in resistant bacteria and so to evolution by natural selection.

    Key words

    Say what each word means before you turn the card.

    Fossil record

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    Antibiotic resistance

    Try answering aloud or in your head before turning the card.

    Natural selection

    Try answering aloud or in your head before turning the card.

    Evidence for evolution

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    See every definition
    Fossil record
    Preserved remains or traces of past organisms, showing that species have changed over time and giving a sequence of change through rock layers.
    Antibiotic resistance
    Evolves when random mutations produce resistant bacteria, and the antibiotic selects these by killing susceptible ones, so the proportion of resistant bacteria increases over generations.
    Natural selection
    Shown in action by antibiotic resistance, because resistant bacteria survive and reproduce while others die, so the population changes over generations.
    Evidence for evolution
    Fossils show long-term change and antibiotic resistance shows natural selection in action, so the theory of evolution by natural selection is well supported.

    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. The first box says random mutations produce some resistant bacteria, and an arrow leads to a box saying antibiotic used. From that box two arrows branch out: one leads to a box saying the antibiotic kills susceptible bacteria, and the other leads to a box saying resistant bacteria survive. An arrow from resistant bacteria survive leads to a box saying resistant bacteria reproduce, then to a box saying the proportion of resistant bacteria increases over generations, then to a box saying the population evolves, and finally to a box saying this supports the theory of evolution by natural selection.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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