Question 1

What is the difference between species richness and species evenness?

Accepted Answer

Species richness is simply the number of different species in a community, while species evenness measures how evenly the individuals are distributed among those species. For example, a forest with 10 species but 90% of individuals belonging to one species has low evenness. Simpson's Index of Diversity accounts for both richness and evenness, giving a more complete picture of biodiversity.

Question 2

How do you calculate Simpson's Index of Diversity?

Accepted Answer

Simpson's Index (D) is calculated using the formula D = 1 - Σ(n/N)², where n is the number of individuals of a particular species, and N is the total number of individuals of all species. First, for each species, calculate (n/N)², then sum these values, and finally subtract from 1. The result ranges from 0 (no diversity) to nearly 1 (high diversity). For example, if you have 10 individuals of species A and 10 of species B, N=20, (10/20)² = 0.25 for each, sum = 0.5, D = 0.5.

Question 3

Why is genetic diversity important for a species?

Accepted Answer

Genetic diversity allows a population to adapt to changing environments. With higher genetic variation, some individuals may possess traits that help them survive new diseases, climate shifts, or other pressures. Low genetic diversity, as seen in cheetahs or some crop plants, makes a species more vulnerable to extinction because a single disease or environmental change can wipe out the entire population.

Question 4

What are the main threats to biodiversity?

Accepted Answer

The main threats include habitat loss (e.g., deforestation, urbanisation), overexploitation (e.g., overfishing, poaching), pollution (e.g., pesticides, plastic waste), invasive species that outcompete native species, and climate change altering habitats. These threats often interact, making conservation complex. For example, climate change can exacerbate habitat loss by shifting suitable ranges.

Question 5

How does natural selection lead to evolution?

Accepted Answer

Natural selection acts on existing genetic variation within a population. Individuals with traits better suited to their environment are more likely to survive and reproduce, passing on those advantageous alleles. Over many generations, the frequency of these alleles increases, leading to changes in the population's characteristics. This gradual change in allele frequencies is evolution. For example, antibiotic resistance in bacteria evolves because resistant bacteria survive treatment and reproduce.

Question 6

What is the difference between in situ and ex situ conservation?

Accepted Answer

In situ conservation protects species in their natural habitats, such as national parks or marine reserves. It maintains ecosystem processes and allows species to continue evolving. Ex situ conservation involves protecting species outside their natural habitat, like in zoos, seed banks, or botanical gardens. It is useful for critically endangered species but can be costly and may not preserve natural behaviours. Both approaches are often used together in integrated conservation strategies.

Topic 4: Biodiversity and Natural Resources

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