Genetic Diversity

What is genetic diversity?

Genetic diversity: the total number of genetically controlled characteristics that appear in the phenotype of a species.

What is the gene pool?

Gene pool: the complete set of alleles carried by all the individuals in a population.

• Basically the sum of all genetic variation in a population, including all possible alleles present (not just the genes).

What is a genome, and how does it differ from a gene pool?

Genome: all the genetic information (base pairs) found in one complete set of an organism's genetic material (all the genes).

• The genome belongs to an individual, while the gene pool is within a population.

What are the levels of ecological organisation in genetic diversity?

1. Individual.

2. Species.

3. Population.

4. Community.

5. Ecosystem.

What is an individual, in ecological organisation?

Individual: a single living organism of a particular species.

What is a species, in ecological organisation?

Species: a group of organisms that share similar characteristics and are capable of interbreeding to produce fertile offspring.

What is a population, in ecological organisation?

Population: members of one species living in one region at a particular time.

What is a community, in ecological organisation?

Community: all the different populations of different species interacting and living together in the same area at the same time.

What is an ecosystem, in ecological organisation?

Ecosystem: a community of interacting organisms (biotic factors) together with the non-living (abiotic) components of their environment, and the interactions between them.

What is the level of biodiversity, species diversity?

The variety of different kinds of organisms living in a particular habitat or region. Example: all the different plant species in the Australian Desert.

What is genetic diversity, as a level of biodiversity, and why is it important?

Genetic diversity: The variety of genes or the number of different genes inherited.

• A species with high genetic diversity has a large gene pool.

• High genetic diversity is important as it increases the chances of the species surviving through environmental changes.

• Example: Siberian tiger

How does genetic diversity in a population relate to tolerance and optimum range?

• All organisms need to stay in their tolerance range in order to survive

• Genetic diversity in a population ensures that individual organisms have diversity in their tolerance range

• Means individuals of the species may be able to survive in changing environmental conditions

How does the tolerance range differ to the optimum range? How does genetic diversity in a population relate to this?

• Tolerance range: the range of conditions in which an organism can survive.

• Optimum range: the range of conditions within the tolerance range in which an organism carries out life processes (e.g. living, hunting, mating, raising offspring) at an optimal level.

Genetic diversity in a population ensures that individual organisms have diversity in their tolerance range

How does gene pool size relate to genetic diversity?

• A large gene pool = high genetic diversity; a small gene pool = low genetic diversity.

• High genetic diversity means individuals within a species have more variation in their tolerance ranges, increasing the chances of surviving changing environmental conditions.

• Low genetic diversity makes a population more susceptible to environmental changes, since there's less variation for natural selection to act on.

Does population size determine genetic diversity?

• Population size doesn't automatically determine genetic diversity.

• A large population can still have low genetic diversity, especially if it started from a small number of genetically similar organisms (the founder effect).

Why are small populations particularly at risk of low genetic diversity?

• Fewer individuals to contribute different alleles to the gene pool.

• Inbreeding becomes more likely, which reduces genetic diversity over generations.

• Low genetic diversity in a population increases vulnerability to disease, environmental change, and reduces long-term survival prospects of the species (e.g. Siberian tiger, cheetah).

What is inbreeding and how does it decrease genetic diversity?

• Inbreeding: members of the same family or close relatives breeding only amongst themselves.

• Reduces the variety of alleles passed into the gene pool over generations

• Results in a population more vulnerable to disease and environmental change

What are the advantages of genetic diversity?

• Ensures that individual organisms have diversity in their tolerance range.

• Means individuals of the species may be able to survive in changing environmental conditions.

• Large gene pool = high genetic diversity.

What are the implications of low genetic diversity?

• A large population can have low genetic diversity, especially if the population was started with a small number of genetically similar organisms (founder effect).

• Can also occur due to inbreeding, which reduces genetic diversity over time.

• Low genetic diversity can result in a population being susceptible to environmental changes. Small gene pool = low genetic diversity.