7.2.1 Populations

Key Terms

• Gene Pool: The total number of alleles present within a population.
• Allelic Frequency: The proportion of a specific allele within the gene pool, expressed as a decimal or percentage.

Population Size & Dynamics

The size of a population depends on a balance between factors that increase and decrease its size:

• Birth rate and immigration increase the population.
• Death rate and emigration decrease the population.

Environmental Influence

Populations are influenced by abiotic (non-living) and biotic (living) factors:

• Abiotic factors include temperature, water availability, and light intensity.
• Biotic factors include predation, competition, and disease.

Adaptations in Populations

Organisms in a population may adapt to their environment over time due to natural selection, which leads to changes in allelic frequency.

Example: In a population exposed to a new predator, individuals with favourable alleles (e.g., camouflage) are more likely to survive, reproduce, and pass on their alleles, increasing their frequency in the gene pool.