Triple Science Only - Other theories about evolution (Darwin vs. Lamarck)
Laura Armstrong & Joe Wolfensohn
Teachers
Recall Questions
This topic requires prior knowledge of variation, inheritance, and the process of natural selection.
Who is credited with the theory of evolution by natural selection?
Charles Darwin.
What is variation in a species?
Variation is the difference in characteristics between individuals of the same species.
What is natural selection?
The best adapted individuals in a population are most likely to survive and reproduce.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains other theories about evolution, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
Darwin’s Theory of Evolution (Recap)
Darwin proposed that:
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Individuals in a species vary genetically.
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Those better suited to the environment survive and reproduce – this is natural selection.
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These favourable traits are inherited by the next generation.
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Over a long time (many generations) the adaptation becomes more common in the population.
His theory was published in On the Origin of Species (1859) and faced controversy for several reasons:
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It challenged religious beliefs (e.g. creation by God).
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There was insufficient evidence at the time, such as the fossil record.
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The mechanism of inheritance (genes / DNA) was not yet understood.
Jean-Baptiste Lamarck’s Theory
Lamarck proposed a different theory of evolution before Darwin. It was based on two main ideas:
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Use and Disuse
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He believed that if an organism used a characteristic a lot during its lifetime, it would become more developed.
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For example, giraffes stretching their necks would lead to longer necks.
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Inheritance of Acquired Characteristics
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Lamarck suggested these acquired characteristics could be passed on to offspring.
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E.g. a giraffe that stretched its neck would have babies with longer necks.
Why Lamarck’s Theory Is Rejected Today:
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We now know that acquired characteristics are not passed on genetically.
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Changes in an organism during its lifetime do not affect its DNA.
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Modern genetics supports Darwin’s theory, not Lamarck’s.
Key Terms
- Natural selection - The process where organisms better adapted to their environment survive and reproduce.
- Acquired characteristic - A trait developed during an organism’s lifetime (not inherited).
- Lamarckism - The discredited theory that acquired traits can be inherited.
- Inheritance - The process by which genetic information is passed from parents to offspring.
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Exam Tip
- Make sure you can explain clearly why Lamarck’s theory is incorrect and how Darwin’s theory was eventually supported by genetic evidence and evidence from the fossil record.
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Practice Question
Explain one difference between Lamarck’s theory of evolution and Darwin’s theory. (2 marks)
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Lamarck believed that changes which occurred during an organism’s life could be inherited.
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Darwin believed that only inherited characteristics caused by genetic variation could be passed on.
More Practice
Try to answer the practice question from the TikTok video on your own, then watch the video to see how well you did!