Selective Breeding (Edexcel IGCSE Biology)

Selective breeding in plants involves the intentional breeding of plants with desirable traits to produce offspring with enhanced characteristics.

Plants are selectively bred for various characteristics including:

• Disease resistance in food crops

• Increased crop yield

• Tolerance to weather conditions such as drought or frost

• Improved taste and nutritional quality of fruits

• The development of large or unique flowers

By selectively breeding plants with desired characteristics over successive generations, breeders can create new variant crops that address specific agricultural challenges and meet consumer demands. This enhances food security and improves agricultural sustainability.

Selective breeding can lead to inbreeding, which occurs when closely related individuals are bred together to perpetuate desired traits.

Inbreeding reduces the genetic diversity within a population, resulting in an increased risk of inheriting harmful genetic defects.

Additionally, the reduced genetic variation makes organisms more susceptible to new diseases, as there are fewer chances of possessing resistance alleles within the population.

Inbreeding in plants leads to a reduction in genetic diversity within populations by limiting the number of alleles, or different versions of genes, present in the population.

When closely related individuals are repeatedly bred together the genetic variation decreases, resulting in a higher frequency of homozygous genotypes and a loss of heterozygosity. This increases the risk of genetic defects and susceptibility to diseases.

Selective breeding, also known as artificial selection, involves the intentional mating of animals with desirable traits to produce offspring that inherit those characteristics. Through careful selection and breeding of animals over successive generations, breeders aim to develop new breeds or strains that reliably exhibit the desired characteristics.

By selecting and breeding animals that exhibit specific characteristics, breeders can amplify the desired traits within a population over multiple generations and create distinct breeds with uniform traits.

Animals are selectively bred for various characteristics, including:

• High milk or meat production in livestock such as cows, goats, and sheep.

• Large egg-laying capacity in chickens.

• Docile temperament in domestic dogs.

• High-quality wool in sheep.

• Specific physical features or performance abilities in horses.

Maintaining genetic diversity in selectively bred animal populations is crucial for :

• Resilience to disease.

• Good health.

• Adaptability of breeds over time.

• Natural selection occurs naturally, whereas selective breeding only occurs with human action.

• Natural selection causes populations to become better adapted to survive in their environment, whereas selective breeding causes populations to have traits that benefit humans.

• Natural selection takes a long time, whereas selective breeding only takes a few generations.