CIE IGCSE Biology

Revision Notes

18.3 Adaptive Features

Adaptations

  • An adaptive feature is an inherited feature that helps an organism to survive and reproduce in its environment
  • You should be able to interpret images or other information about a species in order to describe its adaptive features, for example:

 

Adaptive features 1, CIE IGCSE Biology

A typical question here might be to explain how the leaf area and distribution and density of stomata help different species of plant survive in their different habitats

Extended Only

Adaptations & Fitness

  • Adaptive features are the inherited functional features of an organism that increase its fitness
  • Fitness is the probability of an organism surviving and reproducing in the environment in which it is found
Extended Only

Hydrophytes & Xerophytes

Hydrophytes

  • Plants adapted to live in extremely wet conditions
  • Common adaptations include:
    • Large air spaces in their leaves to keep them close to the surface of the water where there is more light for photosynthesis
    • Small roots as they can also extract nutrients from the surrounding water through their tissues
    • Stomata usually open all the time and mainly found on the upper epidermis of the leaf where they can exchange gases much more easily with the air

 

Hydrophyte adaptations, IGCSE & GCSE Biology revision notesHydrophytes are adapted to live in wet conditions such as ponds

 

Xerophytes

  • Plant adapted to live in extremely dry conditions
  • Common adaptations include:
    • Thick waxy cuticle – the cuticle cuts down water loss in two ways: it acts as a barrier to evaporation and also the shiny surface reflects heat and so lowers temperature
    • Sunken stomata: stomata may be sunk in pits in the epidermis; moist air trapped here lengthens the diffusion pathway and reduces evaporation rate
    • Leaf rolled with stomata inside and an inner surface covered in hairs – traps moist air and prevents air movement across stomata which reduces transpiration
    • Small leaves: many xerophytic plants have small, needle-shaped leaves which reduce the surface area and therefore the evaporating surface
    • Extensive shallow roots allowing for the quick absorption of large quantities of water when it rains
    • Thickened leaves or stems which contain cells that store water

 

Xerophyte adaptations, IGCSE & GCSE Biology revision notesXerophytes are adapted to live in extremely dry conditions such as deserts

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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