Selective breeding

What is selective breeding?

• Selective breeding (artificial selection) is when humans choose specific organisms with desirable traits to breed.

• Over generations, this enhances certain traits in a species.

What are the steps in selective breeding?

1⃣ Choose parents with the desired characteristics.
2⃣ Breed them together.
3⃣ Select the best offspring with the desired traits.
4⃣ Repeat the process for multiple generations until the trait is prevalent.

How do farmers use selective breeding?

• Increases crop yield – Wheat plants with larger grains are bred.

• Disease resistance – Crops that are naturally resistant to pests are selected.

• Better meat production – Chickens that grow faster are bred for farming.

How is selective breeding used in livestock?

• Cows bred for higher milk production.

• Chickens bred to lay more eggs.

• Sheep with softer wool.

• Dogs bred for specific traits (e.g., guide dogs for temperament, greyhounds for speed).

What are the benefits of selective breeding?

✅ Higher yields – More food production.
✅ Better quality products – Improved milk, meat, or fruit.
✅ Disease resistance – Reduces crop failure.
✅ Desirable traits – Animals with better temperament or appearance.

What are the risks of selective breeding?

❌ Reduces genetic variation – Leads to inbreeding.
❌ Increases risk of genetic disorders due to reduced gene pool – Health problems in purebred animals.
❌ Less resistance to new diseases – If a disease affects one, it may kill many.
❌ Ethical concerns – Some breeds suffer from health issues (e.g., pugs with breathing problems).

What is inbreeding, and why is it a problem?

• Inbreeding happens when closely related individuals breed.

• Reduces genetic diversity, leading to:
  ✅ Higher risk of genetic disorders (e.g., hip dysplasia in dogs).
  ✅ Lower ability to adapt to environmental changes.
  ✅ Increased susceptibility to diseases.

How does selective breeding compare to genetic engineering?

	Selective Breeding	Genetic Engineering
Method	Chooses existing traits	Directly alters DNA
Speed	Takes generations	Can be done quickly
Precision	Less precise	More precise
New Traits?	No new traits, only enhances existing ones	Can introduce entirely new traits

Example: Golden Rice (genetically engineered for vitamin A) vs. Drought-resistant wheat (selectively

Why do some people oppose selective breeding?

• Animal welfare – Some breeds have serious health issues (e.g., bulldogs with breathing problems).

• Loss of genetic diversity – Reduced variation can harm ecosystems.

• Overuse of resources – Breeding only high-yield crops can deplete soil nutrients.

natural selection vs artificial selection

Feature	Natural Selection 🌿	Artificial Selection (Selective Breeding) 🧬

Definition

The process where organisms with beneficial traits survive and reproduce.

The process where humans select organisms with desirable traits to breed.

Speed

Slow process – Takes many generations for significant change.

Faster process – Humans can enhance traits in a few generations.

Genetic Diversity

Maintains genetic variation, which is important for species survival.

Reduces genetic variation, which can lead to inbreeding and health issues.

Adaptation

Produces better-adapted organisms for survival in the wild.

Produces organisms suited to human needs, not necessarily survival.

Outcome

Leads to evolution over time and can result in new species.

Leads to improved traits but does not create new species.

one is determined by nature and one is determined by humans