Environment and Plant Evolution
What the exam tests
This domain links environmental factors and pollution with plant adaptations, ecological succession, and evolutionary change. It also tests evidence for evolution and major transitions in plant evolution.
Core rules and concepts
- Lichens are sensitive to sulfur dioxide and are used as pollution indicators.
- Greenhouse gases include carbon dioxide, methane, nitrous oxide, and water vapour; they trap outgoing infrared radiation.
- Ozone depletion is caused mainly by chlorofluorocarbons; ozone in the stratosphere shields against ultraviolet radiation.
- Eutrophication results from excess nutrients, especially nitrogen and phosphorus, causing algal blooms and oxygen depletion.
- Succession moves from pioneer species to a climax community; primary succession starts on bare substrate.
- Xerophytes reduce water loss through thick cuticle, sunken stomata, and succulence; hydrophytes have air spaces and reduced cuticle.
- Evolution evidence includes fossils, homologous structures, embryology, and molecular comparisons.
Worked example
Lichens disappear from a forest near a coal-fired plant. What does this indicate? Lichens are highly sensitive to sulfur dioxide, so their absence suggests SO2 pollution. The reasoning uses a known indicator response, not a general guess about air quality.
Traps that cost marks
Natural selection acts on phenotypes, not directly on genotypes. Do not credit Lamarckian inheritance of acquired traits. Ozone depletion and global warming are different problems with different causes. A climax community is not permanently unchanging.