Biodiversity

Laura Armstrong & Joe Wolfensohn

Teachers

Laura Armstrong Joe Wolfensohn

Recall Questions

This topic requires prior knowledge of biodiversity from GCSE and genetic diversity. You can test your knowledge on these below.

What is biodiversity?

Biodiversity is the variety of living organisms in an ecosystem. It includes species diversity, genetic diversity, and habitat diversity.

What is habitat diversity?

The variety of different habitats in an area/ ecosystem.

How does genetic diversity arise between members of the same species?

Via mutations, crossing over and independent assortment during meiosis, and random fertilisation of gametes.

Topic Explainer Video

Check out this @JoeDoesBiology video that explains biodiversity or read the full notes below. Once you've gone through the whole note, try out the practice questions!

What is Biodiversity?

Biodiversity is the variety of life within a particular ecosystem. It is essential for the stability of ecosystems and contributes to resilience against environmental changes.

Biodiversity can be considered at three different levels:

Species Diversity

  • The variety of species within a habitat.
  • Measured using species richness (number of different species) and species evenness (the abundance of each species).

Genetic Diversity

  • The variety of genes and alleles within a species.
  • Higher genetic diversity allows for greater adaptation to environmental changes.

Habitat Diversity

  • The variety of different habitats within an ecosystem.
  • A greater variety of habitats means greater species diversity.

Measuring Biodiversity

Biodiversity is measured using species richness and species evenness.

  • Species Richness: The number of different species in a given area.

  • Species Evenness: The relative abundance of individuals within each species.

  • The greater the number of species in an area and the more evenly distributed the organisms of each species are, the greater the species diversity.

  • Some habitats may have a large number of different species, and therefore a high species richness, but may have very low numbers of some species. In this case, the species diversity would not be high as the ecosystem is dominated by a small number of species.

Biodiversity can be measured by using diversity indices.

  • Index of Diversity (D): A numerical value that quantifies biodiversity using the formula:

Where:

  • N = Total number of organisms of all species

  • n = Number of individuals of each species

Higher values of D indicate greater biodiversity.

Factors Affecting Biodiversity

Human Activities

  • Deforestation.
  • Pollution.
  • Agriculture (monoculture reduces biodiversity as well as increased use of pesticides and herbicides).
  • Climate change.

Conservation Efforts

  • In situ conservation (protecting species in their natural habitat, e.g., national parks).
  • Ex situ conservation (protecting species outside their natural habitat, e.g., zoos, seed banks).
  • Legislation (laws protecting species and habitats).

Importance of Maintaining Biodiversity

Maintaining biodiversity is crucial for the health and stability of ecosystems. There are several reasons why it is important, categorised into moral/ethical, economic, ecological, and aesthetic reasons.

Moral / Ethical Reasons

  • Every species has intrinsic value, and humans have a responsibility to protect them.
  • Many species are endangered due to human activities, making conservation a moral duty.
  • Future generations should have the right to experience diverse ecosystems.

Economic Reasons

  • Ecosystem services such as pollination by bees are essential for agriculture.
  • Biodiversity supports industries such as fishing, forestry, and medicine.
  • Many medicines are derived from plants and animals, and undiscovered species could hold new medical treatments.
  • Tourism and ecotourism provide income for many countries, especially those with rainforests, coral reefs, and wildlife reserves.

Ecological Reasons

  • Biodiversity ensures ecosystem stability by making food chains and nutrient cycles more resilient.
  • A loss of species can lead to imbalances – e.g., the loss of predators can cause prey populations to increase uncontrollably.

Aesthetic Reasons

  • Biodiversity makes landscapes and ecosystems more visually appealing.
  • Natural environments contribute to mental well-being and stress reduction.
  • Many people enjoy nature through hiking, birdwatching, and photography, which depends on biodiversity.
  • Biodiversity inspires art, literature, and culture worldwide.

Biodiversity is not just about saving species; it is essential for the economy, ecosystem stability, and human well-being. Efforts to conserve biodiversity ensure a sustainable future for both the planet and future generations.

Key Terms 

  • Biodiversity: The variety of living organisms in an ecosystem.
  • Species Diversity: The number of different species and their relative abundance.
  • Genetic Diversity: The variety of alleles within a species.
  • Habitat Diversity: The number of different habitats in an ecosystem.
  • Species Richness: The number of different species in an area.
  • Species Evenness: The relative abundance of individuals within each species.
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Exam Tip

You will be provided with the formula for the index of diversity in your exam. You do not need to memorise it but you should be able to use it correctly.

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Scientists Studied two different forests:

  • Forest A: 15 species of trees with varying population sizes.
  • Forest B: 15 species of trees, but one species dominates.

(a) Explain why Forest A has a higher biodiversity of insects than Forest B. (3 marks)

(b) Describe one method scientists could use to estimate plant species diversity in an area. (3 marks)

(a)

  • Forest A has higher species evenness / Forest B has lower species evenness.
  • Forest A therefore has a greater variety of different habitats.
  • Forest A has a greater variety of different food sources.

(b)

  • Scientists use quadrats placed at random to collect data.
  • They use a large number of quadrats (if a number is given it must be 10 or more).
  • They record species richness (the number of different species) and species evenness (the abundance of each species).

Practice Question 1

Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!

Practice Question 2

If you want to try out another one, check this video out and see how you do!