Chapter 17 Artificial Selection, Speciation and evolutionary relationships
Artificial Selection
1. What artificial selection is
2. Problems caused by inbreeding
3. How outbreeding can maintain genetic diversity
Artificial selection
Artificial selection, also called selective breeding, is when humans breed organisms selectively for
specific genetic traits and determine which individuals reproduce. It changes allele frequencies by
favouring certain traits that then become more common over time.
How artificial selection works
Artificial selection uses the same principles as natural selection but, instead of the environment,
humans choose the desired traits and the individuals that reproduce, leading to species that are
beneficial to humans in some manner.
The process of artificial selection:
1. Select a population that displays variation.
2. Select individuals with desired traits, like high milk production in female cattle and male
cattle with female relatives with high milk yields.
3. Selectively breed individuals together that display these desired traits.
4. Grow and test the offspring for the desired traits.
5. Repeat the selection process across many generations.
This produces a population of individuals that all show certain desired characteristics and that can
be further inbred to produce offspring with these characteristics.
For example, in plants, rice and wheat can be artificially selected to improve the following:
To produce many different varieties of rice and wheat.
To produce wheat grains that are rich in gluten.
To produce varieties that have resistance to diseases like those caused by fungal infection.
Problems caused by inbreeding and the benefits of outbreeding
Although artificial selection can preserve desirable traits, it can also decrease genetic diversity due
to inbreeding. The negative effects of this can be overcome with some degree of outbreeding.
, Inbreeding Outbreeding
The mating of closely related
The process of breeding unrelated or
Definition individuals, often a part of
distantly related individuals
artificial selection
Effect on genetic
Decreases genetic diversity Increases genetic diversity
diversity
Increases heterozygosity, protecting
Effect on
Reduces heterozygosity against harmful conditions caused by
heterozygosity
homozygous recessive genotypes
Increases homozygosity,
Effect on Decreases homozygosity, reducing the
leading to the expression of
homozygosity expression of harmful recessive alleles
harmful recessive alleles
Inbreeding depression - the
Hybrid vigour - the increased ability to
What it can lead to loss of ability to survive and
survive and grow well
grow well
Effect on fitness Reduces fitness and
Increases fitness and adaptability
and adaptability adaptability
Maize plants with inbreeding Hybrid vigour in maize plants makes
Example in maize depression become them healthier, grow taller, and
progressively smaller produce higher yields
A balance of inbreeding and outbreeding can preserve desirable traits like crop uniformity for easier
harvesting and selling, while still maintaining heterozygosity for better health and yield.
Artificial Selection
1. What artificial selection is
2. Problems caused by inbreeding
3. How outbreeding can maintain genetic diversity
Artificial selection
Artificial selection, also called selective breeding, is when humans breed organisms selectively for
specific genetic traits and determine which individuals reproduce. It changes allele frequencies by
favouring certain traits that then become more common over time.
How artificial selection works
Artificial selection uses the same principles as natural selection but, instead of the environment,
humans choose the desired traits and the individuals that reproduce, leading to species that are
beneficial to humans in some manner.
The process of artificial selection:
1. Select a population that displays variation.
2. Select individuals with desired traits, like high milk production in female cattle and male
cattle with female relatives with high milk yields.
3. Selectively breed individuals together that display these desired traits.
4. Grow and test the offspring for the desired traits.
5. Repeat the selection process across many generations.
This produces a population of individuals that all show certain desired characteristics and that can
be further inbred to produce offspring with these characteristics.
For example, in plants, rice and wheat can be artificially selected to improve the following:
To produce many different varieties of rice and wheat.
To produce wheat grains that are rich in gluten.
To produce varieties that have resistance to diseases like those caused by fungal infection.
Problems caused by inbreeding and the benefits of outbreeding
Although artificial selection can preserve desirable traits, it can also decrease genetic diversity due
to inbreeding. The negative effects of this can be overcome with some degree of outbreeding.
, Inbreeding Outbreeding
The mating of closely related
The process of breeding unrelated or
Definition individuals, often a part of
distantly related individuals
artificial selection
Effect on genetic
Decreases genetic diversity Increases genetic diversity
diversity
Increases heterozygosity, protecting
Effect on
Reduces heterozygosity against harmful conditions caused by
heterozygosity
homozygous recessive genotypes
Increases homozygosity,
Effect on Decreases homozygosity, reducing the
leading to the expression of
homozygosity expression of harmful recessive alleles
harmful recessive alleles
Inbreeding depression - the
Hybrid vigour - the increased ability to
What it can lead to loss of ability to survive and
survive and grow well
grow well
Effect on fitness Reduces fitness and
Increases fitness and adaptability
and adaptability adaptability
Maize plants with inbreeding Hybrid vigour in maize plants makes
Example in maize depression become them healthier, grow taller, and
progressively smaller produce higher yields
A balance of inbreeding and outbreeding can preserve desirable traits like crop uniformity for easier
harvesting and selling, while still maintaining heterozygosity for better health and yield.
