Evolution Flashcards
What is evolution?
Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited genes.
State the two non- random process involved in evolution.
Natural and sexual selection.
State a random process of evolution.
Genetic drift
What is the original source of new sequences of DNA?
Mutation
What is selection?
Selection results 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?
Sexual selection is the non-random process involving the selection of alleles that increase the individuals chances of mating and producing offspring.
What is sexual dimorphism?
When sexual selection leads to a difference in from between male and female individuals.
State the two parts that sexual selection is due to.
Male-male rivalry
Female choice
What is involved in male-male rivalry?
Large size or weaponry that increase access to females through success in conflict.
What does female choice involve?
Involves females assessing the fitness of males.
What are selection pressures?
The environmental factors that influence which individuals in a population pass on their alleles.
State the two types of selection pressures and give examples of each.
- biotic, examples include; competition, predation, disease and parasitism
- abiotic, examples include; temperature, light, humidity, pH and salinity
When selection pressures are strong, what is the rate of evolution?
Rapid
What does the Hardy- Weinberg Principle state?
In the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations.
State the Hardy-Weinberg equation.
P^2 + 2pq + q^2 = 1
What does the p^2 in the Hardy-Weinberg equation mean?
The frequency of homologous dominant genotypes.
What does 2pq in the Hardy-Weinberg equation mean?
The frequency of heterozygous genotype.
What does q^2 in the Hardy-Weinberg equation mean.
The frequency of homozygous recessive genotype.
When is genetic drift more common?
In smaller populations. (Alleles are more likely to be lost from the gene pool)
Explain an example of genetic drift.
The population bottleneck effect is an example of genetic drift that can occur when a population size is reduced for at least one generation.
How is the gene pool altered?
By genetic drift because certain alleles may be under-represented or over-represented, and so allele frequencies change.
Explain what is meant by fitness.
Fitness is 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 is meant by absolute fitness?
Absolute fitness is the ratio between the frequency of individuals of a particular genotype after selection, to those before selection.
What does an absolute fitness of 1 indicate.
The frequency of that genotype is stable.
Explain what is meant by relative fitness.
Relative fitness is the ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype.
What is co-evolution?
Co-evolution is the process by which two or more species evolve in response to selection pressures imposed by each other. A change in the traits of one species acts as a selection pressure on the other species.
Explain what is meant by symbiosis.
Symbiosis is a co-evolved intimate relationship between members of two different species.
Explain what mutualism is.
Mutualism is a symbiotic relationship in which the species in the interaction are interdependent on each other for resources or other services and since both species gain, the interaction is (+/+).
Explain what commensalism is.
Commensalism is a symbiotic relationship in which only one of the species substantially benefits and, for the other, the relationship is neither substantially positive or negative, so is neutral (+/0).
Explain what parasitism is.
Parasitism is a symbiotic relationship in which the parasite species benefit in terms of energy or nutrients while the host species is harmed by the loss of these resources (+/-).
What does the Red Queen Hypothesis State?
That in a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species, which must adapt to avoid extinction.
