Topic 5.2: Natural Selection Flashcards
General idea of the theory of natural selection
Survival of the fittest
Key components of natural selection (ICE AGE)
a) Inherited variation
b) Competition
c) Environmental selection
d) Adaptations
e) Genotype frequency changes
f) Evolution occurs
What would happen if all organisms had an identical genotype?
None would be favored more than other
No natural selection
Mechanisms by which genetic variation between individuals in a species occur (3)
a) Mutation
b) Meiosis
c) Sexual reproduction
How does mutation contribute to genetic variation?
New alleles are produced by a change in the nucleotide sequence of a gene
How does meiosis contribute to genetic variation?
New combinations of alleles are produced via crossing over + independent assortment
How does sexual reproduction contribute to genetic variation?
The genetic combination from two distinct sources creates new gene combinations
How does competition occur?
As species produce more offspring than the environment can support, there’s struggle for survival
Definition of adaptations
Features that make an individual suited to its environment (Do not develop during a single lifetime)
What happens when there is competition?
Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring.
What is the implication that biological adaptations have a genetic basis?
They may be passed to offspring when the parents reproduce.
What change does natural selection generate in a population’s allele frequency? (2)
a) Increases the frequency of features that make individuals better adapted
b) Decreases the frequency of other characteristics leading to changes within the species
How does adaptive radiation occur? (2)
a) It occurs when members of a single species occupy a variety of distinct niches with different environmental conditions
b) Members evolve different morphological features to the different selection pressures.
How is natural selection reflection in finches of the Galapagos Island?
They have specialized beak shapes depending on their primary source of nutrition
How does antibiotic resistance occur? (3)
a) A mutation in a single bacterium makes it more resistant to antibiotics.
b) Antibiotics kills susceptible strains, letting the resistant strains proliferate
c) A bacterial population with no resistance to an antibiotic may develop into a bacterial population with some resistance via plasmid transfer.
