Adaptive FeaturesCambridge IGCSE Biology: Revision notes
Section 1
What Is an Adaptive Feature?
An adaptive feature is an inherited feature that helps an organism to survive and reproduce in its environment. In exam questions you may be given information or a description of an unfamiliar species and asked to identify and explain its adaptive features — for each feature, link it clearly to a specific survival or reproductive advantage in that organism's environment.
Always explain HOW a feature helps, not just WHAT the feature is — e.g. 'thick waxy cuticle reduces water loss by evaporation', not just 'it has a thick cuticle'.
Section 2
How Are Plants Adapted to Dry or Wet Environments?
Xerophytes are plants adapted to survive in dry environments. Typical adaptive features include:
- A thick, waxy cuticle to reduce water loss by evaporation
- Reduced leaf surface area (e.g. spines instead of broad leaves) to reduce transpiration
- Sunken stomata (in pits) to trap moist air and reduce water loss
- Extensive root systems to maximise water uptake from the soil
Hydrophytes are plants adapted to living in water or waterlogged environments. Typical adaptive features include:
- Large air spaces in stems and leaves, providing buoyancy and aiding gas exchange
- Thin cuticles, since water loss is not a problem in an aquatic environment
- Flexible stems and leaves that can move with water currents without breaking
A cactus is a xerophyte: its spines (reduced leaves) minimise water loss and its thick stem stores water.
Section 3
How Do Adaptive Features Arise in a Population?
Adaptation is the process, resulting from natural selection, by which populations become more suited to their environment over many generations. Individuals with adaptive features that make them better suited to their environment are more likely to survive and reproduce, passing those features on to the next generation. Over many generations, this increases the frequency of useful adaptive features within the population.
Must Know
- An adaptive feature is an inherited feature that helps survival and reproduction in a given environment
- Always explain how a feature gives an advantage, not just describe it
- Xerophytes (dry environments): thick cuticle, reduced leaf area, sunken stomata, extensive roots
- Hydrophytes (wet environments): large air spaces, thin cuticle, flexible stems
- Adaptation is a long-term population-level process driven by natural selection over many generations
That's the notes covered.
Carry on to the next subtopic.