Artificial Selection
Natural Selection and Adaptive Evolution
In natural settings, adaptive evolution takes place by natural selection, a process in which differences in t…
When you look at a population of animals you may notice some variations or differences between individuals of the same species. Perhaps some are larger than others or there are differences in their coloration. These variations serve as the basis for natural selection where beneficial traits in a population that positively affect survival and reproduction will be preserved. For example, animals that can more easily camouflage with their environment evade predators and pass on their genes more often than those that do not. This camouflage coloration is a phenotype, defined as the visual expression of a trait. A genotype refers to the set of genes responsible for a phenotype. Therefore, due to natural selection certain genotypes are maintained over time, while less favorable variations disappear and this drives the evolution of populations.
We humans have studied this process and taken advantage of naturally occurring variations to purposely evolve plants and animals to farm or keep as companions. This process is known as artificial selection, the propagation and domestication of plants and animals for favorable traits. Let's look at dogs for example. Thousands of years ago, humans started selectively breeding pairs of wolves for traits like docility, protection and hunting prowess along with appearance. We continued this selective breeding over countless generations and this has culminated in scores of modern dog breeds, including the Great Dane and Chihuahua, which in turn are both very different in appearance and character to their ancestor, the wolf.
We have also implemented artificial selection in plants. Brassica oleracea was once a large, leafy plant, but it has been artificially selected in different ways to produce many common vegetables we eat today, including kale, cabbage, cauliflower and even kohlrabi. Another species in the same family, Brassica napus, is commonly known as the oilseed rape plant because of the abundant oil sequestered in its seeds, which are excellent for cooking or fuel production.
In this lab, you will artificially select traits from individual oil seed rape plants to produce two lines displaying different levels of a trait, hairiness.
When you look at a population of animals you may notice some variations or differences between individuals of the same species. Perhaps some are larger than others or there are differences in their coloration. These variations serve as the basis for natural selection where beneficial traits in a population that positively affect survival and reproduction will be preserved. For example, animals that can more easily camouflage with their environment evade predators and pass on their genes more often than those that do not. This camouflage coloration is a phenotype, defined as the visual expression of a trait. A genotype refers to the set of genes responsible for a phenotype. Therefore, due to natural selection certain genotypes are maintained over time, while less favorable variations disappear and this drives the evolution of populations.
We humans have studied this process and taken advantage of naturally occurring variations to purposely evolve plants and animals to farm or keep as companions. This process is known as artificial selection, the propagation and domestication of plants and animals for favorable traits. Let's look at dogs for example. Thousands of years ago, humans started selectively breeding pairs of wolves for traits like docility, protection and hunting prowess along with appearance. We continued this selective breeding over countless generations and this has culminated in scores of modern dog breeds, including the Great Dane and Chihuahua, which in turn are both very different in appearance and character to their ancestor, the wolf.
We have also implemented artificial selection in plants. Brassica oleracea was once a large, leafy plant, but it has been artificially selected in different ways to produce many common vegetables we eat today, including kale, cabbage, cauliflower and even kohlrabi. Another species in the same family, Brassica napus, is commonly known as the oilseed rape plant because of the abundant oil sequestered in its seeds, which are excellent for cooking or fuel production.
In this lab, you will artificially select traits from individual oil seed rape plants to produce two lines displaying different levels of a trait, hairiness.
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Q1: What is the difference between phenotype and genotype?
A phenotype is the visual expression of a trait, such as an animal's coloration or size. A genotype refers to the set of genes responsible for producing that phenotype. Both are shaped by natural selection, where beneficial genotypes are maintained over time while less favorable variations disappear, driving population evolution.
Q2: How does artificial selection differ from natural selection?
Natural selection occurs when beneficial traits improve survival and reproduction in nature. Artificial selection, also called selective breeding, is when humans deliberately choose which organisms breed to produce the next generation. Humans cause selection by propagating plants and animals with favorable traits, allowing rapid evolution over many generations.
Q3: What role does genetic variation play in evolution?
Genetic variation provides the raw material for both natural and artificial selection. Without variation in traits within a population, selection cannot act because there are no differences to select upon. Populations containing diverse phenotypes allow selection to preserve beneficial traits and drive evolutionary change across generations.
Q4: How has artificial selection changed dogs from their wolf ancestors?
Thousands of years ago, humans selectively bred wolves for traits like docility, protection, hunting ability, and appearance. Over countless generations, this artificial selection produced modern dog breeds such as Great Danes and Chihuahuas, which differ dramatically in appearance and character from their wolf ancestors, demonstrating rapid evolutionary change.
Q5: What vegetables come from artificial selection of Brassica oleracea?
Brassica oleracea, originally a large leafy plant, has been artificially selected to produce numerous common vegetables including kale, cabbage, cauliflower, and kohlrabi. This demonstrates how artificial selection visualization plants data analysis reveals the remarkable diversity humans can create from a single species through selective breeding over hundreds of years.
Q6: Why is Brassica napus valuable for artificial selection studies?
Brassica napus, commonly known as oilseed rape, has been artificially selected for abundant oil in its seeds, which is excellent for cooking and fuel production. Its subspecies, Wisconsin Fast Plants, has an extremely short one-month life cycle, making it ideal for research and education to observe artificial selection effects across multiple generations quickly.
Q7: How do camouflage traits demonstrate natural selection in populations?
Animals with coloration that camouflages them in their environment evade predators more effectively and reproduce more often than those without camouflage. This camouflage phenotype is preserved through natural selection because the underlying genotypes that produce it are passed on more frequently, gradually increasing the trait's prevalence in the population.