Lesson-1-Selective-Breeding

Lesson 1: Selective Breeding / Artificial Selection

• Presenter: Mr. Jonathan L. Cabatbat

What is Selective Breeding?

• Selective breeding is the process of breeding plants and animals to enhance particular traits.

• Synonymous with artificial selection.

Artificial Selection

• This selection process is termed "artificial" due to significant human influence on the traits that change in a population or species.

Differentiating Domestication and Selective Breeding

• Domestication:

  • Involves genetic changes at the population level through artificial selection.

  • Accentuates traits desired by humans.

• Taming:

  • Refers to animals becoming accustomed to human presence, without genetic changes.

  • Distinct from domestication.

Historical Context of Selective Breeding

• Charles Darwin detailed selective breeding's impacts in his book, "On The Origin of Species."

• Discussed the selective breeding and domestication of animals like pigeons, dogs, and cattle.

• Used selective breeding to support the theory of natural selection.

Selective Breeding vs. Natural Selection

• Main difference: Human involvement.

• In natural selection, the survival of organisms with certain traits enhances their reproductive abilities (survival of the fittest).

• In selective breeding, humans control and favor specific traits.

Mechanism of Selective Breeding

• Characteristics are determined by gene variants passed from generation to generation.

• Gene Variants:

  • Differences in gene sequences, e.g., single nucleotide polymorphisms (SNPs).

Examples in Selective Breeding

• Offspring inherit traits from parents; e.g., children of tall parents may also be tall due to gene inheritance.

• Selectively breed tall parents to pass on "tall" gene variants.

• Repeated selective breeding amplifies desired traits over generations.

Types of Selective Breeding

1. Inbreeding:

• Breeding between closely related individuals.

2. Linebreeding:

• A form of inbreeding involving more distant relatives, e.g., cousins.

• Reduces purebred risk and health issues associated with close inbreeding.

3. Self Pollination:

• Pollination from the same flower or another on the same plant.

• Produces offspring with shuffling genes, not genetically identical.

• Allows for inbreeding practices in plants for uniform offspring.

4. Cross Breeding:

• Breeding two organisms of different species for desirable traits.

• Example: Labradoodle combines traits of Poodles and Labrador Retrievers.

Advantages of Selective Breeding

• Establishes and maintains stable traits for advantageous qualities.

• Enhances disease resistance, strength, calmness, etc.

Disadvantages of Selective Breeding

• Risks of reduced genetic diversity leading to inbreeding depression.

• Issues can arise from breeding for specific traits which neglect others, e.g., roosters bred for size can't perform essential mating behaviors.

Examples of Selective Breeding

• Carrots cultivated in various colors.

• Variegated maize (Indian corn).

• Charolais cattle produce leaner beef varieties.

• Size variant breeds like Chihuahuas and Great Danes.

Process of Selective Breeding

1. Identify desired characteristics.

2. Choose parents exhibiting these traits.

3. Select and breed the best offspring from these parents.

4. Continuously repeat the process.

Reasons for Selective Breeding

• Primarily in animal husbandry for agriculture.

Benefits of Selective Breeding

• Increases food production, pest resistance, and overall health in domesticated species.

• Examples: cows that produce more milk, chickens that lay larger eggs.

• Contributes to better service animals and enhanced agriculture over time.

Additional Disadvantages of Selective Breeding

• Loss of genetic diversity and potential gene loss.

• Animal discomfort from extreme breeding practices, e.g., cows with large udders and heavy chickens that struggle to stand.

• Risk of health complications from inbreeding practices.