Evolution Flashcards
What is evolution?
the change over time in the proportion of individuals in a population differing in one or more inherited traits
Why is there a change in allele frequencies during evolution?
changes in allele frequency occur through the non-random processes of natural selection and sexual selection, and the random process of genetic drift
What is genetic variation?
Variation in traits arises as a result of mutation. Mutation is the original source of new sequences of DNA. These new sequences can be novel alleles. Most mutations are harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual.
How does variation affect individuals?
Individuals with variations that are better suited to their environment tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation
What does selection result in?
The non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles.
What is sexual selection?
the non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring. It may lead to sexual dimorphism
What is male-male rivalry?
large size or weaponry increases access to females through conflict. Female choice involves females assessing the fitness of males.
What does genetic drift occur?
when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Genetic drift is more important in small populations, as alleles are more likely to be lost from the gene pool.
What is the importance of bottleneck and founder effects on genetic drift?
Population bottlenecks occur when a population size is reduced for at least one generation. Founder effects occur through the isolation of a few members of a population from a larger population. The gene pool of the new population is not representative of that in the original gene pool.
How is the gene pool altered?
by genetic drift because certain alleles may be underrepresented or over-represented and allele frequencies change
What are selection pressures?
the environmental factors that influence which individuals in a population pass on their alleles. They can be biotic: competition, predation, disease, parasitism; or abiotic: changes in temperature, light, humidity, pH, salinity.
What is the Hardy-Weinberg principle?
In the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations.
p^2+2pq+q^2=1
What are the conditions for maintaining the HW equilibrium and what do changes indicate?
no natural selection, random mating, no mutation, large population size and no gene flow (through migration, in or out). Evolution is occurring.
What is fitness?
an indication of an individual’s ability to be successful at surviving and reproducing. Fitness is a measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species.
What does fitness refer to?
the contribution made to the gene pool of the next generation by individual genotypes Fitness can be defined in absolute or relative terms
