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18.2Variation and Selection

Adaptive features — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 15 parts Lesson 2 of 3 1 quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision
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Lesson summary

18.2 Adaptive features — IGCSE BIOLOGY notes: Define adaptive features and describe the adaptations of animals, hydrophytes and xerophytes.Adaptive feature = an inherited feature that helps an organism to survive and reproduce in its environment.Fitness — organisms with adaptive …

  • Identification
  • Desert animals
  • Large air spaces in leaves
  • Small roots
  • Thick waxy cuticle
  • Sunken stomata

Part 1 of 6Adaptive features

Adaptive features
Adaptive feature
Adaptive feature an inherited feature that helps an organism to survive and reproduce in its environment.
Fitness
  • Fitness organisms with adaptive features are more likely to survive and pass on their alleles.
Identification
  • Identification adaptations can be described from images or data, for example a fennec fox with large ears, pale fur and furry feet.

Part 2 of 6Interpreting data on adaptation

Desert animals
  • Desert animals a gerbil makes urine much more concentrated than humans, beavers or dolphins.
Benefit
  • Benefit it loses little water when excreting urea, which conserves water where it is hard to replace.
Method
  • Method compare the feature with other species and link it to the environment.

Part 3 of 6Adaptations of hydrophytes

1Hydrophyte
Hydrophyte a plant adapted to live in extremely wet conditions, such as ponds.
2Large air spaces in leaves
  • Large air spaces in leaves give flotation and keep leaves near the surface where there is more light.
3Small roots
  • Small roots nutrients can be absorbed from the surrounding water through the tissues.
4Stomata
  • Stomata usually open all the time and mainly on the upper epidermis, for easy gas exchange with air.

Part 4 of 6Adaptations of xerophytes

Adaptations of xerophytes
Xerophyte
Xerophyte a plant adapted to live in extremely dry conditions, such as deserts.
Thick waxy cuticle
  • Thick waxy cuticle acts as a barrier to evaporation and its shiny surface reflects heat.
Sunken stomata
  • Sunken stomata moist air trapped in pits lengthens the diffusion pathway and reduces evaporation.
Rolled leaf with hairs
  • Rolled leaf with hairs traps moist air and stops air movement across the stomata, reducing transpiration.
Small needle-shaped leaves
  • Small needle-shaped leaves reduce the evaporating surface area.
Roots
  • Roots extensive and shallow to absorb rain quickly, or deep to reach water tables.
Thickened leaves or stems
  • Thickened leaves or stems contain cells that store water.

Part 5 of 6Hydrophytes and xerophytes compared

FeatureHydrophyteXerophyte
HabitatVery wetVery dry
LeavesLarge, floating, air spacesSmall, rolled or thick
StomataOpen, on upper surfaceSunken in pits
RootsSmallExtensive shallow or deep
Main problemLight and gas exchangeWater loss

Part 6 of 6More from the specification

1
Adaptive alleles and genetic variation
  • Adaptive alleles and genetic variation advantageous mutations in functional genes cause physiological adaptations that provide a means to survive harsh environments.
2
Definition of an Adaptive Feature
  • An adaptive feature is an inherited structural, physiological,
    • or behavioural characteristic that enhances an organism's survival probability and reproductive fitness in its natural habitat.
3
Xerophytic Adaptations in Desert Flora
  • Xerophytes exhibit sunken stomata, thick waxy cuticles, curled leaves,
    • and extensive root networks to retard transpiration and withstand prolonged subterranean moisture deficits.
4
Hydrophytic Adaptations in Aquatic Plants
  • Hydrophytes possess abundant internal aerenchyma tissue for buoyancy and internal gas diffusion, poorly developed xylem vessels,
    • and stomata restricted exclusively to the upper leaf epidermis.
5
Development
  • The changes as an organism becomes more complex and mature.
6
Natural selection
  • Survival and reproduction of the best-adapted individuals.
7
Selective breeding
  • Humans choosing which individuals breed.
8
Phenotypic variation
  • Differences in phenotype between organisms of the same species.
9
Artificial selection
  • Selective breeding of organisms with desirable traits by humans.
10
Continuous variation
  • A range of phenotypes between two extremes.
11
Discontinuous variation
  • A limited number of distinct phenotypes with no intermediates.
12
Blood group
  • A phenotype set by alleles I-A, I-B and I-O.
13
Variation
  • Differences between individuals of the same species.
14
Mutation
  • A random change in genetic material.

Key terms

TermMeaning
Adaptive featureAn inherited feature that helps an organism survive and reproduce.
HydrophyteA plant adapted to very wet conditions.
XerophyteA plant adapted to very dry conditions.
CuticleA waxy layer on the leaf surface.
TranspirationLoss of water vapour from leaves.
StomataPores in the leaf for gas exchange.

Avoid these mistakes

1
Saying adaptations are acquired during life — adaptive features are inherited.
2
Saying individuals change to suit the environment — populations adapt over generations.
3
Giving a feature without its function — state how it helps survival.
4
Saying xerophytes have large leaves — they usually have small or rolled leaves.

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