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The Impact of Population Increase

The importance and measurement of species biodiversity

  • 3 things to know
  • Components 01, 02 and 03

Overview

Recall questions on species biodiversity, richness and evenness, calculating and comparing Simpson's Diversity Index, why diverse ecosystems are stable, ecosystem services, keystone species, and the economic, medical, agricultural, aesthetic and scientific reasons for conserving biodiversity.

What you need to know

Answer each one before you reveal it.

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Evaluation

Why does the loss of species biodiversity matter to people?

Key term

Define species biodiversity.

Key term

Distinguish between species richness and species evenness.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define species biodiversity.

    Model answer

    Species biodiversity is the number of different species present in a community together with the relative abundance of each.

  2. 2

    Distinguish between species richness and species evenness.

    Model answer

    Species richness is simply the number of species present, whereas evenness describes how equally the individuals are shared between those species.

  3. 3

    Why is species richness on its own a poor measure of biodiversity?

    Model answer

    Two communities can contain the same number of species, but one dominated by a single species is far less diverse than one in which all are equally abundant.

  4. 4

    What do the symbols n and N represent in Simpson's Diversity Index?

    Model answer

    The symbol n is the number of individuals of one particular species and N is the total number of individuals of all species in the sample.

  5. 5

    What range of values can Simpson's Diversity Index take, and what does a high value mean?

    Model answer

    It takes values between 0 and 1, and a value close to 1 indicates a highly diverse community.

  6. 6

    A sample of 30 organisms contains three species with 10 individuals each. Using D = 1 − Σ(n/N)², calculate the index.

    Model answer

    The index is 0.67.

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