17.4 Selection (Cambridge (CIE) O Level Biology): Flashcards
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- FrontNatural Selection
Define natural selection.
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Define natural selection.
The process by which individuals with advantageous characteristics are more likely to survive and reproduce, passing on their alleles.
Who first put forward the theory of natural selection?
Charles Darwin.
By what other name is natural selection known?
Survival of the fittest.
Individuals with characteristics that are in their environment are more likely to survive and reproduce.
Individuals with characteristics that are advantageous in their environment are more likely to survive and reproduce.
Why is there competition between individuals in a population?
Because more offspring are produced than the environment can support.
What is passed on to offspring during natural selection?
The alleles that code for advantageous characteristics.
Over many generations, the allele for an advantageous characteristic becomes more in the population.
Over many generations, the allele for an advantageous characteristic becomes more common in the population.
True or False?
Natural selection can cause an individual to evolve within its lifetime.
False.
Natural selection acts only on inherited features, so populations evolve over several generations.
True or False?
The genetic variation that leads to natural selection occurs by chance.
True.
Variation arises by chance, never in response to the environment.
What are the original sources of the genetic variation in a population?
Mutation and meiosis.
Give one commonly used example of natural selection.
The evolution of body colour in the peppered moth (or snail shell colour).
During natural selection, is it genes or alleles that are passed on?
Alleles.
Define antibiotic resistance.
The ability of bacteria to survive exposure to an antibiotic that would normally kill them.
What does MRSA stand for?
Methicillin-resistant *Staphylococcus aureus*.
The allele that gives bacteria antibiotic resistance arises due to a random .
The allele that gives bacteria antibiotic resistance arises due to a random mutation.
Why can antibiotic resistance develop very quickly in bacteria?
Because bacteria have short generation times and reproduce rapidly.
Which bacteria are more likely to survive when exposed to an antibiotic?
Those with the allele for antibiotic resistance.
Surviving resistant bacteria the allele for resistance on to their offspring.
Surviving resistant bacteria pass the allele for resistance on to their offspring.
True or False?
The development of antibiotic resistance is an example of natural selection.
True.
Resistant bacteria survive, reproduce and pass on the resistance allele.
True or False?
Bacteria become resistant because they choose to change in response to the antibiotic.
False.
Resistance arises by random mutation before the antibiotic is present.
What happens to the number of resistant bacteria over many generations?
It increases.
What must exist in a bacterial population before selection for resistance can occur?
Variation – some bacteria must already carry the resistance allele.
Why do non-resistant bacteria die when exposed to the antibiotic?
They lack the resistance allele.
How quickly can a resistant bacterial population develop?
In as little as a few hours, if the bacteria are reproducing quickly.
Define artificial selection.
The breeding of organisms by humans to develop varieties with desirable characteristics.
By what other name is artificial selection known?
Selective breeding.
Who selects the desirable characteristics in artificial selection?
Humans.
In artificial selection, individuals with characteristics are chosen to breed.
In artificial selection, individuals with desirable characteristics are chosen to breed.
What is the first step of selective breeding?
Selecting the individuals with the desired characteristics.
Why is the process of selective breeding repeated over many generations?
Until all offspring show the desired characteristics.
True or False?
Artificial selection is carried out by the environment.
False.
Artificial selection is carried out by humans; the environment selects features in natural selection.
True or False?
Selective breeding uses the principles of natural selection.
True.
Humans select the features, rather than the environment.
Selective breeding has produced many important varieties of plants and animals.
Selective breeding has produced many economically important varieties of plants and animals.
Give one example of an animal variety produced by selective breeding.
The many recognisable dog breeds.
What is the main difference between natural and artificial selection?
In natural selection the environment selects advantageous features; in artificial selection humans select desirable features.
After selecting parents with the desired characteristics, what is the next step?
Cross-breed the selected individuals together.
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