TheIB Biology | Year 2 (Senior) · Natural Selection · part 2/8
Natural Selection: Fitness in 8 Min (6 Marks)
Biotic and abiotic selection pressures, what fitness really means, and why only heritable traits can evolve, with finches, peppered moths and bacteria as examples. Includes a six mark exam-style question solved step by step. Part 2 of 8 on IB Biology D4.1 Natural selection, for SL and HL.
In this lesson
- 0:00 The question
- 0:12 Selection pressures
- 1:13 Fitness
- 2:20 Heritable traits
- 3:12 Practice: five steps
- 4:52 What earns the mark
- 5:31 Exam question solved
- 6:14 Recap
- 6:37 Next Tuesday
Answers to the practice questions at the end of the video
- Any two of: high temperature, low temperature, drought (lack of water) [2].
- How well an individual survives and reproduces in its environment [1].
- Darker skin from the sun is an acquired trait [1]; it does not change the DNA (alleles) in the gametes, so it is not passed to offspring [1].
Questions are original, in the style of the exam; marks are estimates.
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