Describe selective breeding with reference to: (a) selection by humans of individuals with desirable features (b) crossing these individuals to produce the next generation (c) selection of offspring showing the desirable features
Describe selective breeding with reference to: (a) selection by humans of individuals with desirable features (b) crossing these individuals to produce the next generation (c) selection of offspring showing the desirable features
Answer
Selective breeding, also known as artificial selection, is a process in which humans intentionally choose specific individuals with desirable traits to reproduce, thereby influencing the genetic makeup of future generations. This practice has been used for thousands of years in agriculture, animal husbandry, and horticulture to enhance particular characteristics in plants and animals.
(a) Selection by Humans of Individuals with Desirable Features
In selective breeding, humans identify and select individuals that exhibit traits considered valuable or desirable. These traits can include:
- Agricultural Traits: In crops, desirable features might include larger fruit size, higher yield, disease resistance, or drought tolerance. For example, farmers may select corn plants that produce larger ears or have a higher resistance to pests.
- Animal Traits: In livestock, desirable features can include faster growth rates, better meat quality, increased milk production, or specific behavioral traits. For instance, dairy farmers may select cows that produce more milk or have a calm temperament.
This selection process is based on observable characteristics and can involve various methods such as visual assessments, performance testing, and genetic analysis.
(b) Crossing These Individuals to Produce the Next Generation
Once individuals with desirable features are selected, they are bred together to produce the next generation. This crossing can occur in several ways:
- Controlled Mating: In many cases, breeders will control the mating process to ensure that only selected individuals breed. This can involve artificial insemination or selective pairing based on genetic compatibility.
- Hybridization: Breeders may also cross different breeds or varieties to combine desirable traits from both parents. For example, crossing two different strains of tomatoes might result in offspring that have improved flavor and disease resistance.
The goal of this step is to create offspring that inherit the desired traits from their parents.
(c) Selection of Offspring Showing the Desirable Features
After the new generation is produced, breeders evaluate the offspring for the presence of the desirable traits. This evaluation involves:
- Phenotypic Assessment: Breeders assess physical characteristics (phenotypes) such as size, shape, color, and overall health. For example, in livestock breeding, farmers might look for calves that exhibit strong growth and good conformation.
- Performance Testing: In some cases, offspring may be tested for performance traits such as growth rate or yield before selection. For instance, in crop breeding, plants might be evaluated for their yield under specific environmental conditions.
Once the best-performing individuals are identified—those that exhibit the desired features—they are selected for further breeding. This cycle of selection continues over multiple generations to reinforce and enhance the desired traits within the population.
Sourav
