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4.4.3Unit 4: Energy, Environment, Microbiology and Immunity

Biodiversity and Endemism — IAL Edexcel Linear Revision Notes & Topical Questions

5 min read 4 parts Lesson 23 of 28 Unit quiz

📚 IAL Edexcel Linear Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
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Part 1 of 4Three Levels

Biodiversity is the variety of genes, species and habitats within a region.

Ecosystem diversity
  • Ecosystem diversity The range of different habitats in an area;
    • a coral reef has many microhabitats and so high diversity, a sandy desert has few.
Species diversity
  • Species diversity Takes into account both the number of species and how abundant each is, so rare species add less than abundant ones.
Species richness
  • Species richness The number of different species in an ecosystem;
    • a tropical rainforest is described as species-rich.
Genetic diversity
  • Genetic diversity The variety of alleles and genes within the genome of a species, measured as how many genes have more than one allele.

Part 2 of 4Why Diversity Matters

Why Diversity Matters
Resilience
  • Resilience Ecosystems with high diversity can resist environmental change better than those with few species.
Example
  • Example Forests dominated by one or two tree species can collapse if a pathogen targets the dominant tree.
Genetic variety
  • Genetic variety Alleles help populations adapt to new predators, pathogens, competitors or changes in temperature and rainfall.
Small populations
  • Small populations Isolated small populations inbreed, so more individuals are homozygous and recessive genetic diseases become more common.

Part 3 of 4Endemism

Some species have very restricted ranges.

1
An endemic species occurs naturally in only one particular area of the world and nowhere else.
2
An example is the pygmy three-toed sloth, which is found only on a small island off the coast of Panama.
3
Endemic species are especially at risk because a single local threat can remove the whole species.
4
Protecting such places therefore has a large effect on global biodiversity.

Part 4 of 4Exam Checklist & Tips

4.4.3 – Key Points for the Exam

  • Biodiversity The variety of genes, species and habitats in a region.
  • Species richness The number of species present in a community.
  • Genetic diversity The variety of alleles within a species or population.
  • Endemic Found naturally in only one geographic area.

Common Mistakes

  • Equating species richness with species diversity, when diversity also includes how evenly the individuals are distributed.
  • Saying genetic diversity is the number of genes, when it is the variety of alleles of the genes.
  • Claiming high diversity always means more species of animals, forgetting habitat and genetic levels.
  • Stating that endemic species are common because they live in one place;
    • their small range makes them vulnerable.

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