2.2 Evolution Flashcards
(31 cards)
What is evolution?
The change over time in proportion of individuals in a population differing in one or more inherited traits
What occurs during evolution?
Changes in allele frequency through the non-random processes of natural selection and sexual selection, and the random process of genetic drift
What does natural selection act on?
Genetic variation in populations
What is mutation?
The original source of new sequences of DNA, these new sequences can be novel alleles. Most mutations are harmful or neutral but some can be benefitial
What results in selection pressures?
Populations produce more offspring than the environment can support
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 individuals chances of mating and producing offspring
What does sexual selection lead to?
Sexual dimorphism
What is sexual dimorphism?
Two sexes of the same species exhibit different characteristics
What can sexual selection be due to?
Male-male rivalry and female choice
What is male-male rivalry?
Large size or weaponry increases access to females through conflict e.g. male deer use antlers
What is female choice?
Females assess the fitness of males, this may cause males to attempt to attract females through displays
What is genetic drift?
Occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next, it is more important in small populations as alleles are more likely to be lost from the gene pool
What can cause genetic drift?
Bottleneck and founder effects
What is the bottleneck effect?
Population bottlenecks occur when a population size is reduced for at least one generation. This reduces population can have lower genetic diversity
What is the founder effect?
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 may gene pools be altered due to genetic drift?
Certain alleles may be under-represented or over-represented and allele frequencies change
What happens when selection pressures are strong?
The rate of evolution is rapid, these selection pressures are the environmental factors that influence which individuals in a population pass on their alleles
What can selection pressures be?
Biotic or abiotic
What is the Hardy-Weinberg Principle?
States that in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations
What are the conditions for maintaining the HW equilibrium?
No natural selection, random mating, no mutation, large population size, no gene flow
What is the HW principle used to determine?
Whether a change in allele frequency is occurring in a population over time, changes suggest evolution is occuring
What is fitness?
An indication of an individuals ability to be successful at surviving and reproducing
What is absolute fitness?
The ratio between the frequency of individuals of a particular genotype after selection and those before selection
= after/before
