Unit 2 KA2 Flashcards
Evolution
Change over time in the proportion of individuals in a population differing in one or more inherited traits
What occurs during evolution and how?
Changes in allele frequency through:
- Non random processes - sexual selection and natural selection
- Random process - genetic drift
Natural Selection
Acts on genetic variation in populations which arise from mutation
Mutation
Original source of new sequences of DNA
New sequences - novel alleles
Harmful or neutral
Rare to be beneficial
Selection
Non-random increase in the frequency of advantages alleles and the non-random decrease in the frequency of deleterious alleles
Sexual Selection
Non-random process involving selection of alleles that increase individuals chance of mating and producing offspring
What can sexual selection lead to?
Sexual dimorphism
What is sexual selection due to?
Male-male rivalry (large size or weaponry increases access to females through conflict)
Female choice (assessing the fitness of males)
Genetic Drift
Occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
Where is genetic drift more important?
Small populations
Population bottlenecks
Occurs when a population size is reduced for at least one generation
Founder effects
Occur through isolation of a few members of a population from a larger population. Gene pool of the new population is not representative of that in the original gene pool.
Why is a gene pool altered by genetic drift?
Certain alleles may be underrepresented or overrepresented and allele frequencies change
Selection pressures
Environmental factors that influence which indiciels in a population pass on their alleles
Types of selection pressures
Biotic: competition, predation, disease, paratism
Abiotic: changes in temperature, light, humidity, pH, salinity
Hardy-Weinberg Principle
States that in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations
Conditions for maintaining HW equilibrium
No natural selection
Random mating
No mutation
Large population size
No gene flow
HW principle use
Used to determine whether a change in allele frequency is occurring in a population over time
Fitness
Indication of an individuals ability to be successful at surviving and reproducing
Measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species
Absolute fitness
Frequency of a particular genotype after selection/Frequency of a particular genotype before selection
Relative fitness
Number of surviving offspring per individual of a particular genotype/Number of surviving offspring per individual of the most successful genotype
Co-evolution
Process by which two or more species evolve in response to selection pressures imposed by each other
Mutualism
Both organism in the interaction are interdependent in each other (+/+)
Commensalism
Only one organism benefits (+/0)
Paratism
Parasite benefits and host is harmed (+/-)
Red Queen Hypothesis
In a coevolutionary relationship change in the traits of one species can act as a selection pressure on the other species
