Selective Breeding

Selective Breeding

High School

​

Learning Objectives

• Define the terms artificial selection and selective breeding.

• Explain the main differences between inbreeding and hybridization.

• Explain how selective breeding produces organisms with desired traits.

• Compare and contrast artificial selection with natural selection.

Key Vocabulary

​

Selective Breeding

Humans intentionally breed organisms with specific desired traits to produce those same traits in their offspring.

​

Artificial Selection

Humans select and breed organisms with desirable traits to pass them on to the next generation.

​

Inbreeding

Mating two closely related organisms to maintain or strengthen desired traits within the same family line.

​

Hybridization

Breeding two different organisms to combine the most desirable traits from both parents in their offspring.

​

​

Comparing Artificial and Natural Selection

Artificial Selection

• Humans identify desirable traits in organisms to ensure future generations also have these specific traits.

• The most common form is selective breeding, where humans choose which organisms get to reproduce.

• The main driving force that determines which traits are passed on is human interference.

Natural Selection

• Organisms with traits that are better suited to their environment are more likely to survive.

• These surviving organisms get to reproduce and pass on their advantageous traits to their offspring.

• The main driving force that determines which traits are passed on is environmental pressure.

Multiple Choice

What is the primary factor that distinguishes artificial selection from natural selection?

• The speed at which traits change in a population.

• The types of organisms that are affected.

• The involvement of human interference in choosing traits.

• The environment in which the organisms live.

​

​

Methods of Selective Breeding

Inbreeding

• ​This breeding method involves the mating of two organisms that are very closely related to each other.

• ​​Its main purpose is to preserve and intensify specific desirable traits within a pure lineage.

• ​However, this method can also increase the chances of offspring inheriting any kind of genetic defects.

Hybridization

• ​This method involves crossing two organisms that have different traits to produce a hybrid.

• ​​The goal is to combine the best characteristics of both of the parents in the offspring.

• ​This breeding technique is also known to increase the genetic variation within a certain population.

Multiple Choice

A dog breeder mates two fast dogs from the same litter to produce even faster puppies. Which method of selective breeding is this?

• Natural Selection

• Inbreeding

• Hybridization

• Genetic Mutation

​

Common Misconceptions About Selective Breeding

Misconception	Correction
Selective breeding is the same as natural selection.	Breeding is human-driven; natural selection is driven by environmental pressures.
Inbreeding only produces negative results and defects.	It also helps preserve and magnify desirable traits.
Any two organisms can be bred for the best traits.	Hybridization works between closely related or same species.
Selective breeding creates entirely new traits from scratch.	It works with existing genes, making traits more common.

Multiple Choice

How does selective breeding serve as evidence for the theory of evolution?

• By creating entirely new genes that did not previously exist in the population.

• By demonstrating how targeted breeding can cause significant variation in a species in a relatively short time.

• By showing that traits are fixed and cannot be changed over time.

• By proving that all species share an identical common ancestor from the start.

Multiple Choice

A farmer wants to produce apples that are both large and resistant to a common fungus. What would be the most effective first step using the principles of selective breeding?

• To identify and cross-breed an existing large apple variety with an existing fungus-resistant apple variety.

• To find a new species of fruit that is large and fungus-resistant.

• To use inbreeding on the largest apples to make them even larger.

• To expose the apple trees to the fungus and hope for a random mutation.

Multiple Choice

A cat breeder has been inbreeding a line of cats for their unique fluffy tails. However, she notices that with each new generation, more kittens are born with a dangerous heart defect. What is the most likely cause of this unintended outcome?

• The cats have simply adapted to a new environment where a strong heart is not needed.

• The process of hybridization is introducing weaker genes from an outside source.

• Natural selection is favoring cats with heart defects in the breeding facility.

• The process of inbreeding is increasing the frequency of a harmful recessive allele that is genetically linked to the fluffy tail trait.

Multiple Choice

Imagine you are tasked with developing a new breed of sheep that has both extremely soft wool and a high tolerance for cold weather. How could you strategically use both hybridization and inbreeding to achieve this goal over several generations?

• First, use hybridization to cross a soft-wooled breed with a cold-tolerant breed. Then, use inbreeding on the offspring that show both desired traits to stabilize the new breed.

• Let a herd of soft-wooled sheep live in a cold environment and allow natural selection to create the new breed over time.

• Continuously cross different breeds of sheep randomly until the desired combination of traits appears by chance.

• Only use inbreeding with a single, cold-tolerant sheep to try and create soft wool.

​

Summary

• Selective breeding is artificial selection guided by humans to get desired traits.

• It differs from natural selection, which is guided by environmental pressures.

• Its two main methods, inbreeding and hybridization, enhance genetic traits.

• This process improves organisms such as crops, farm animals, and pets.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4