Natural Selection & Artificial Selection (College Board AP® Biology): Flashcards
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- FrontNatural Selection
Define natural selection.
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Define natural selection.
Natural selection is the main mechanism that drives evolution, in which individuals with favorable phenotypes are more likely to survive and reproduce, passing on their alleles to the next generation.
Define evolutionary fitness.
Evolutionary fitness is a measure of an organism's reproductive success — its ability to survive and pass on its alleles to the next generation.
What are the main steps in evolution by natural selection?
Phenotypic variation exists between individuals in a population
Competition for limited resources leads to differing rates of survival
Individuals with favorable phenotypes are more likely to survive and reproduce
The alleles for favorable phenotypes are passed on to the next generation
These beneficial alleles become more frequent in the population over time
In natural selection, for limited resources leads to differing rates of survival between individuals.
In natural selection, competition for limited resources leads to differing rates of survival between individuals.
True or False?
Environmental change causes an immediate change in the features of organisms.
False.
Natural selection acts on existing phenotypic variation in a population, and change occurs over several generations rather than immediately.
True or False?
Although natural selection acts on individuals, it is populations that evolve as a whole over time.
True.
Selective pressures act on individual organisms, but evolutionary change is seen in the population across generations.
How do biotic and abiotic factors affect the evolution of a population?
They influence the rate and direction of evolution.
Biotic factors include predators and competition
Abiotic factors include temperature and water availability
Because these factors can fluctuate, different genetic variations can be selected in each generation.
How does the peppered moth illustrate natural selection?
During the industrial revolution, pollution darkened tree bark. Dark moths were better camouflaged and survived predation more successfully, so the frequency of the dark allele increased in the population over time.
Define phenotypic variation.
Phenotypic variation is the differences in observable traits between individuals in a population, which arise from genetic differences — for example, new alleles introduced by mutation.
Why is greater variation an advantage for a population?
Populations with greater variation can better adapt to changing environments, because natural selection has a wider range of phenotypes to act on.
Variation in the number and types of within cells can give populations a greater ability to survive and reproduce in different environments.
Variation in the number and types of molecules within cells can give populations a greater ability to survive and reproduce in different environments.
How does DDT resistance in insects increase fitness?
When DDT is present, insects without resistance are killed, while those with a resistance mutation survive and reproduce. The resistance allele increases in frequency, so over time the population becomes predominantly DDT-resistant.
Why can the sickle cell allele increase fitness in malaria-prevalent areas?
Individuals carrying one sickle cell allele (heterozygotes) resist malaria more effectively. They are more likely to survive and reproduce, which increases the frequency of the sickle cell allele in the population.
How can shifting flowering times due to global climate change decrease fitness?
Earlier or later blooming can disrupt plant-pollinator synchronization, so plants may flower when their pollinators are not present. Reduced pollination lowers seed production, decreasing reproductive success and raising extinction risk.
Define artificial selection.
Artificial selection is the process in which humans choose individuals with desirable traits and breed them together, so that the frequency of those traits increases in a species over many generations.
Define selective breeding.
Selective breeding is another name for artificial selection, in which humans deliberately choose which individuals reproduce in order to affect the variation in a species.
Outline the steps involved in artificial selection.
Individuals with desirable traits are chosen
These individuals are bred together
Offspring with the desirable traits are chosen and bred together
This is repeated over many generations
In artificial selection, who determines which individuals reproduce?
Humans determine which individuals reproduce, choosing those with desirable traits.
Artificial selection is repeated over many until the frequency of the desired characteristic increases.
Artificial selection is repeated over many generations until the frequency of the desired characteristic increases.
selection allows humans to affect the variation present in other species.
Artificial selection allows humans to affect the variation present in other species.
Give three examples of traits produced in species through artificial selection.
Increased milk yield in cattle
Faster racehorses
Disease-resistant crops
True or False?
Artificial selection can be used to combine several desirable traits into a single individual.
True.
Humans can select over many generations to bring together multiple desired traits, e.g. breeding crops that have high yield, disease resistance and the ability to grow in poor soil.
True or False?
In artificial selection, individuals to be bred together are chosen at random.
False.
Individuals are chosen because they show desirable traits, not at random; only those with the wanted characteristics are bred together.
Why must artificial selection be carried out over many generations?
Because it takes repeated selection and breeding for the frequency of the desired characteristic to gradually increase within the species.
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