Evolution Flashcards
What is evolution
The change over time in the proportion of individuals in a population differing in one or more inherited traits
The non-random changes in allele frequencies is a result of
Natural selection
Sexual selection
The random changes in allele frequencies is a result of
Genetic drift
What causes variation in traits
Mutations which are the source of new DNA sequences
Are mutations beneficial or harmful to an individual
Most are harmful/neutral but some can be beneficial
Describe the process of natural selection
Populations produce more offspring than the environment can support
Individuals with variations that are better suited to their environment survive longer and produce more offspring. These favourable alleles are passed on to their offspring through breeding. Therefore, there is an increase in the frequency of advantageous alleles and a decrease in the deleterious alleles.
What is sexual selection
The selection of alleles that increase the individual’s chances of mating and producing offspring
What is sexual dimorphism
The differences in form between males and females in the same species
What is male-male rivalry with regards to sexual selection
When males are large in size or have weaponry that increases access to females through conflict
What is female choice with regards to sexual selection
Females assessing the fitness of males
What is genetic drift
Chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
Does genetic drift have a larger impact on smaller populations or larger populations and why
Smaller populations since alleles are more likely to be lost from the gene pool
When does a population bottleneck occur
When a population size is reduced for at least one generation
Describe how founder effects occur
The isolation of a few members of a population.
Therefore, the gene pool of the new population is not representative of the original gene pool
Explain how and why a gene pool is altered by genetic drift
Certain alleles may be under/over-represented and therefore allele frequencies change
What happens to the rate of evolution when selection pressures are strong
Rate of evolution is rapid
What are selection pressures
The environmental factors that influence which individuals in a population pass on their alleles
Name 4 biotic factors
Competition
Predation
Parasitism
Disease
Name 5 abiotic factors
Changes in: Temperature Light Humidity pH Salinity
What does the Hardy-Weinberg principle state
In the absence of evolutionary influences, allele and genotype frequencies will remain constant over the generations
Name the 5 conditions for maintaining the HW principle
No natural selection Random mating No mutation Large population size No gene flow (through migration or emigration)
The formula for calculating allele and genotype frequencies in populations is
p2+2pq+q2=1
p=frequency of dominant allele
q=frequency of recessive allele
p2=frequency of homozygous dominant genotype
2pq= frequency of heterozygous genotype
q2= frequency of homozygous recessive genotype
What is fitness
A measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species
What is the formula for absolute fitness
Frequency of a particular genotype after selection/frequency of a particular genotype before selection
What is the formula for relative fitness
Number of surviving offspring per individual of a particular genotype/Number of surviving offspring per individual of the most successful genotype
What is co-evolution
The process by which two or more species evolve in response to selection pressures imposed by each-other
What does a change in the traits of one species do to the other species during co-evolution
The change in traits acts as a selection pressure on the other species
What is symbiosis
co-evolved intimate relationships between members of two different species
What is mutualism
When both organisms in the interaction are interdependent on each other for resources or other services (+/+)
What is commensalism
When only one of the organism benefits (+/0)
What is the Red Queen Hypothesis
In a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species. Therefore, species in these relationships nee to adapt to avoid extinction.
What is parasitism
When a parasite gains nutrients and energy at the cost of the host
