2.2 evolution Flashcards
Evolution definition
The gradual change in the characteristics of a species over generations caused by natural selection, sexual selection and genetic drift.
Genetic drift definition
The random change in the frequency of alleles in a population.
Where is genetic drift significant
In small populations where alleles can be lost easily.
Natural selection
The non random increase in the frequency of advantageous alleles which will increase the chance of survival and the non random decrease in the decrease of deleterious alleles which cause harm to an organism.
Source of new alleles in a population
Mutation
Hardy Weinberg formula
P2+ 2pq +q2 =1
p+q =1
P value hardy Weinberg
Frequency of dominant allele
q value hardy Weinberg
Frequency of recessive allele
P2 value hardy Weinberg
Frequency of dominant homozygous genotype
Q2 value hardy Weinberg
Frequency of recessive homozygous genotype
2pq value hardy Weinberg
Frequency of dominant heterozygous genotype
P2 + 2pq
Frequency of dominant phenotype.
How can a mutation effect the fitness of an individual
Mutations can cause new alleles to appear in a species which can increase the chance of an individual surfing and reproducing or decrease the chance of an organism surviving and reproducing.
Factors affecting rate of evolution
Mutation rate
Generation time
Metabolic rate
Gene transfer
Mutation rate effect on evolution
The species will have more random and spontaneous changes in their genetic information resulting in more advantageous new alleles appearing in the species, evolution will occur faster.
Generation time effect on evolution
Faster generation time means faster genetic drift and natural selection, meaning there is a greater change in the species faster, meaning evolution will occur faster.
Metabolic rate effect on evolution
Higher metabolic rate means smaller body size and higher temperature - which has been found to produce higher mutation rate.
Gene transfer effect on metabolic rate
Horizontal gene transfer can allow for advantageous genetic traits to be passed on immediately to organisms of the same generation.
Vertical sexual gene transfer can be used to increase variation and increase the rate of evolution.
Fitness definition
The measure of how effective a particular genotype is at leaving offspring in the next generation relative to other genotypes.
Why is natural selection non random
Because the organisms with the highest fitness will survive and reproduce passing on their genes, whereas other organisms will die off.
Sexual selection definition
A form of natural selection, where the non random increase in an allele in the next generation is determined through the selection of mating partners.
Sexual dimorphism
Where there is a distinct physical difference in males and females in a species.
How does sexual selection occur
male - male rivalry for a female, the males will compete for the female.
The female will assess the fitness of the male.
Characteristics such as increased size and weaponry can increase access to mates.
Genetic drift process
A bottleneck effect will decrease the population size and genetic variation.
The surviving population will reproduce together with their limited genetic variation.
The species will make a recovery with limited genetic variation.
Selection pressure
A factor resulting in natural selection
Absolute fitness
The ratio of frequency of a particular genotype between different generations.
Relative fitness
The ratio of frequency of a particular genotype compared with the most succesful genotype
Absolute fitness formula
Absolute fitness = frequency after selection / frequency before selection.
Relative fitness formula
Number of offspring per individual of one genotype
/ number of offspring per individuals of most successful genotype.
Relative fitness =1
Means the genotypes you are looking at is the most successful genotype.
Relative fitness >1
Impossible
Relative fitness <1
The genotype is not the most successful genotype in the species.
Absolute fitness of >1
The frequency of the allele in the species is increasing (increasing fitness)
Absolute fitness <1
The frequency of the allele in the species is decreasing (decreasing fitness)
Absolute fitness =1
The frequency of alleles in the species in remaining constant
(Constant fitness )
Symbiosis
Where two different species interact and have a relationship with each other.
Parasitism
A symbiotic relationship between a host organism which is an organism which is detrimentally affected by the relationship, and an organism which benefits from the relationship by gaining energy or nutrients.
Mutualism
A symbiotic relation between two organisms which both benefit from the relationship.
Commensalism
A symbiotic relationships where one organism benefits and the other organism has no positive or negative effect.
Co evolution definition
Where two different species that interact closely and undergo a change in their characteristics due to selection pressures imposed on each other.
Red queen hypothesis
Red queen theory occurs between parasite and host.
A parasite will mutate to become better adapted to exploiting its host.
This will allow the high fitness mutant to survive and pass on its genes to the next generation.
This will increase selection pressure of parasite burden in hosts.
Then when advantageous alleles arise in the host through mutation these organisms will survive and pass on their genes.
This will allow the next generation to become better adapted to the parasites adaptation.
Causing evolutionary arms race.
