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IB Biology | Year 2 (Senior) · Natural Selection · part 1/8

Natural Selection Explained (6-Mark Question)

Natural Selection Explained (6-Mark Question)

IB Biology D4.1, natural selection: how natural selection works (part 1 of 8, for SL and HL). What natural selection is, where variation comes from (mutation, meiosis and fertilization), and why overproduction of offspring leads to competition. Includes a six mark exam-style question solved step by step. Part 1 of 8 on IB Biology D4.1 Natural selection.

In this lesson

  1. 0:00 Intro
  2. 0:16 Exam question
  3. 0:45 Warm-up
  4. 1:17 Natural selection and evolution
  5. 2:28 Sources of variation
  6. 3:30 Overproduction and competition
  7. 4:33 Practice: explain
  8. 5:41 What earns the mark
  9. 6:12 Exam question solved
  10. 6:55 Recap
Answers to the practice questions at the end of the video
  1. Mutation produces new alleles [1]; sexual reproduction (meiosis and fertilization) produces new combinations of existing alleles [1].
  2. Intraspecific competition.
  3. The fish produce more offspring than the environment can support [1]; resources such as food are limited, so the offspring compete and many die [1].

Questions are original, in the style of the exam; marks are estimates.

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