Natural Selection- Natural Selection Flashcards
(16 cards)
What is natural selection, and how does it contribute to the evolution of a population? (2)
Natural selection is a process where organisms that are better adapted to their environment are more likely to survive, reproduce, and pass on their advantageous traits to the next generation.
Over time, these traits become more common in the population, leading to evolution as the genetic makeup of the population changes.
Define phenotype and phenotypic variation. Provide an example. (2)
A phenotype is an observable trait of an organism, such as its physical appearance or behavior.
Phenotypic variation refers to the differences in these traits within a population. An example is the variation in human hair color, such as blonde, brown, and red hair.
Explain how the peppered moth example illustrates natural selection. (3)
In the peppered moth example, initially, light-colored moths were more common because they blended in with the light-colored lichen on trees.
However, after the Industrial Revolution, soot darkened the trees, and dark-colored moths had better camouflage and a higher chance of surviving and reproducing.
This led to an increase in the frequency of the dark-colored phenotype in industrialized areas, demonstrating natural selection in response to environmental changes.
Describe Darwin’s theory of natural selection. What are the core principles? (4)
Darwin’s theory of natural selection proposes that species evolve over time through a process of differential reproductive success. The core principles include:
Competition for limited resources or predation leads to survival of some individuals.
The environment determines which phenotypes are favorable.
Individuals with advantageous phenotypes are more likely to survive and reproduce, passing on their traits to future generations.
How does natural selection act on variation in a population?
Natural selection acts on existing variation in a population by favoring individuals with phenotypes that provide a survival or reproductive advantage in a specific environment. Over time, this leads to an increase in the frequency of beneficial traits and a decrease in harmful or less advantageous traits.
What is directional selection, and how does it work? Provide an example. (2)
Directional selection occurs when one extreme of a phenotype range is favored, causing a shift in the population’s traits toward that extreme.
An example is the case of the peppered moth, where darker moths were favored in polluted environments because they blended into soot-darkened trees, while lighter moths became more visible to predators.
Explain stabilizing selection and give an example.
Stabilizing selection favors individuals with intermediate phenotypes and selects against extreme traits. For example, in a population of birds with varying beak sizes, if the environment has an abundance of medium-sized seeds, birds with medium-sized beaks are more likely to survive and reproduce, while birds with very small or very large beaks are less likely to survive.
How does stabilizing selection affect genetic diversity?
Stabilizing selection tends to reduce genetic diversity because it favors individuals with traits closer to the population’s average and eliminates extreme phenotypes. Over time, this leads to a population with less variation in the selected trait.
What is disruptive selection, and how does it differ from stabilizing selection? (2)
Disruptive selection occurs when individuals at both extremes of a phenotypic range are favored over individuals with intermediate phenotypes.
This contrasts with stabilizing selection, which favors the intermediate phenotype and selects against extremes.
How can disruptive selection lead to speciation? (2)
Disruptive selection can lead to speciation by promoting the development of two distinct phenotypic groups within a population.
If these groups become reproductively isolated over time due to ecological or behavioral differences, they may diverge enough genetically to become separate species.
Describe an example of directional selection in nature. (2)
An example of directional selection is the evolution of antibiotic resistance in bacteria. When exposed to antibiotics, bacteria with mutations that confer resistance to the drug are more likely to survive and reproduce.
Over time, the population shifts toward a higher frequency of resistant bacteria.
How does the environment influence which phenotypes are favored by natural selection? (2)
The environment determines which phenotypes are advantageous based on the specific challenges or resources available.
For example, in an environment with a lot of predators, individuals with camouflage traits may have a better chance of surviving, while in an environment with limited food, individuals that can find and use resources efficiently may have higher fitness.
What role does genetic variation play in natural selection? (3)
Genetic variation is crucial for natural selection because it provides the raw material for evolution.
Without genetic variation, there would be no different traits for selection to act upon.
The greater the genetic variation, the more likely it is that some individuals will have advantageous traits that increase their fitness in a given environment.
What is differential reproductive success, and how does it relate to natural selection? (2)
Differential reproductive success refers to the idea that individuals with traits that provide an advantage in survival and reproduction are more likely to reproduce and pass on those traits to the next generation.
Over time, this process leads to the increase of advantageous traits in the population, a key component of natural selection.
How does natural selection lead to adaptation? (2)
Natural selection leads to adaptation by favoring individuals with traits that increase their chances of survival and reproduction in a specific environment.
These beneficial traits become more common in the population over time, leading to better adaptation to the environment.
How does the case of giraffes with long necks illustrate natural selection? (3)
The case of giraffes with long necks illustrates natural selection through the idea that giraffes with longer necks can reach food high in trees that shorter-necked giraffes cannot access.
As a result, the long-necked giraffes have higher fitness and are more likely to survive and reproduce, passing on the long-neck trait to their offspring.
Over time, the population becomes dominated by long-necked giraffes.
