Question 22M.2.SL.TZ2.7b
| Date | May 2022 | Marks available | [Maximum mark: 7] | Reference code | 22M.2.SL.TZ2.7b |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Explain | Question number | b | Adapted from | N/A |
The growing human population has an increasing demand for energy derived from crop plants. At the same time, increasing droughts that are part of climate change make it difficult to grow crops in some parts of the world.
Explain how natural selection can cause traits such as drought resistance to develop in wild plants.
[7]
- (natural selection occurs if) there is variation in degree of drought resistance among members of a population/same species;
- variation is caused by mutations (when changes occur in the DNA/nucleic bases/chromosomes);
- variation during meiosis occurs (with separation of chromosomes);
- variation occurs during sexual reproduction (as different alleles combine);
- some variations make some plants more drought-resistant;
- example of variations: deeper roots/more storage tissue for water/thicker cuticles/less opening of stomata/other verifiable variations;
- these variations let some survive and reproduce better/have more offspring
OR
(these variations) confer selective advantage; - these variations/characteristics are passed onto offspring which survive better;
- natural selection increases the frequency of these characteristics;
- eventually leads to changes/evolution in the species / more drought-resistant plants;
The inclusion of ‘drought resistance’ in the stem of the question should have been a suggestion to include it, but many answers were far to general with a vague attempt to explain Natural Selection in general without explaining how the initial variation in the population came about. There were quite a few ‘Lamarckian’ answers with claims of individuals adapting to cope with the change. The average for this question was only 2.8, putting it as one of the most poorly answered.
