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4.1.4Topic 4 · Biodiversity and Natural Resources

Ecological Niches and Adaptations — Edexcel A Level Biology A (SNAB) 9BI0 Revision Notes & Topical Questions

5 min read 9 parts Lesson 6 of 22 1 quiz

📚 Edexcel A Level Biology A (SNAB) 9BI0 Hub / Topical Revision
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4.1.4 Ecological Niches and Adaptations — Edexcel A Level Biology A (SNAB) 9BI0 notes: Define niche, explain competitive exclusion and describe anatomical, physiological and behavioural adaptations with examples.The niche of a species is the role it plays in its community: where …

  • fundamental niche
  • realised niche
  • Anatomical (structural)
  • Exam-style question 1
  • Exam-style question 2
  • Exam-style question 3

Section 1 of 9Habitat and niche

The niche of a species is the role it plays in its community: where it lives, what it eats, what eats it, when it is active and how it interacts with its abiotic environment.

Every species has a unique niche.
Fundamental niche
The fundamental niche is the full range of conditions in which it could survive in the absence of competitors; the realised niche is the narrower range it actually occupies,
  • because of competition and predation.

The competitive exclusion principle states that two species with the same niche cannot coexist indefinitely in the same place: one will outcompete the other.

Habitat and niche
Species that coexist have niches that differ, for example by feeding at different heights or times, which is called niche differentiation.
An example is the grey squirrel replacing the native red squirrel in much of Britain, where the two have very similar niches.

Section 2 of 9Adaptation

An adaptation is a feature that increases an organism's chance of survival and reproduction in its environment. Adaptations arise by natural selection over many generations and are of three types:

Anatomical (structural)
Anatomical (structural) physical features of the body,
  • such as the thick blubber and small surface area to volume ratio of a seal,
  • or the long root system of marram grass.
Physiological
Physiological processes inside the body,
  • such as the production of antifreeze proteins by Arctic fish, the production of venom,
  • or the ability of the kidneys of a desert mammal to produce concentrated urine.
Behavioural
Behavioural the way the organism acts, such as hibernation, migration, courtship displays and burrowing in the heat of the day.

Section 3 of 9Examples of adaptation to extreme environments

OrganismAdaptationAdvantage
Marram grass (dunes)Rolled leaves, sunken stomata, hairs and thick waxy cuticleTraps humid air and reduces water loss by transpiration
CactusSucculent stem, spines for leaves, deep and wide rootsStores water and reduces its loss and herbivory
Polar bearThick fur, blubber, large body, small earsReduced heat loss; low surface area to volume ratio
Kangaroo ratConcentrated urine, nocturnal burrowingConserves water and avoids heat
Hydrophyte, e.g. water lilyAir spaces in tissue, stomata on upper surfaceBuoyancy and gas exchange

Section 4 of 9Convergent evolution and analogous features

Unrelated organisms exposed to similar environments may evolve similar features.

Convergent evolution and analogous features
Sharks and dolphins have streamlined bodies and dorsal fins, although one is a fish and the other a mammal.
Such similarity of function without shared ancestry is convergent evolution, and the structures are called analogous.
Homologous structures, such as the pentadactyl limb of mammals, have the same basic structure but different functions, reflecting a common ancestor.

Section 5 of 9Adaptation and natural selection

Adaptations come about by natural selectionwithin a population there is variation in a feature, caused by mutations.

Adaptation and natural selection
Those individuals with alleles that give an advantage in the environment survive and reproduce more successfully and pass the alleles on,
  • so the frequency of those alleles rises over generations.
Adaptation is therefore a result of change in a population, not of an individual 'trying' to adapt.
A good description of any adaptation includes three parts: the feature, how it works and the way it improves survival or reproduction.

Section 6 of 9Exam focus and links

Questions on adaptations nearly always give an organism in an unusual environment and ask you to explain features.

Exam focus and links
Use the pattern: feature, function, benefit.
For example, a thick layer of blubber (feature) insulates and stores energy (function),
  • reducing heat loss and so energy needed for respiration to keep warm (benefit).
Remember the link to surface area to volume ratio: animals in cold environments tend to be larger with shorter appendages (Bergmann's and Allen's rules),
  • while those in hot environments have large ears or long limbs to lose heat.

You may be asked to link adaptation to natural selection and to speciation: populations that become isolated in different environments develop different adaptations and may eventually become separate species. Link also to the conservation of species, as loss of a habitat removes the niches that a species depends upon, and to ecosystem stability, where a diverse set of niches means a more complex food web.

Practise by choosing any organism you know and writing one anatomical, one physiological and one behavioural adaptation for it, each with a stated benefit.

Section 7 of 9Exam-style questions

  1. Explain how marram grass is adapted to living on sand dunes. [4]4 marks

  2. Two species of bird feed on the same insects in the same trees and one disappears. Explain this in terms of niche. [3]3 marks

  3. Distinguish between physiological and behavioural adaptations, giving an example of each. [4]4 marks

Section 8 of 9Key terms

TermMeaning
NicheThe role of a species in its community, including its habitat, food and interactions.
Competitive exclusionThe principle that two species with identical niches cannot coexist.
AdaptationAn inherited feature that increases fitness in an environment.
Convergent evolutionEvolution of similar features in unrelated groups due to similar selection pressures.
XerophyteA plant adapted to dry conditions.
HydrophyteA plant adapted to living in water.

Section 9 of 9Exam technique

1
Defining niche as the same as habitat. Niche includes role, feeding and interactions.
2
Saying that individuals adapt during their lives. Populations evolve through selection.
3
Listing a feature without explaining how it helps survival.
4
Calling convergent features homologous; they are analogous.
5
Saying competition always leads to extinction; niche differentiation often allows coexistence.

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