UNIT 2 - KA2 Flashcards
Evolution
Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits
What two types of changes occur during evolution
- Non random
- Random
How do changes in allele frequency occur during evolution
During evolution, changes in allele frequency occur through the non random processes of natural selection and sexual selection and the random process of genetic drift
What does natural selection act on
Natural selection acts on genetic variation in populations
What does variation in traits arise as a result of
Variation in traits arises as a result of mutation
What is the original source of new sequences of DNA
Mutation is the original source of new sequences of DNA
What can new DNA sequences be
These new sequences can be novel alleles
What are most mutations.. can they be beneficial?
Most mutations are harmful or neutral but in rare cases they may be beneficial to the fitness of an individual
How much offspring do populations produce
Populations produce more offspring than the environment can support
What can individuals with variations that are better suited to the environment do
Individuals with variations that are better suited to their environment tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation.
What does selection result in
Selection results in the non random increase in the frequency of advantageous alleles and the non- random decrease in the frequency of deleterious alleles
Sexual selection
Sexual selection is the non - random process involving the selection of alleles that increases the individuals chances of mating and producing offspring
What can sexual selection lead to
Sexual selection may lead to sexual dimorphism
What can sexual selection be due to
Sexual selection can be due to male-male rivalry amd female choice
Male-male rivalry
Large size or weaponry increases access to females through conflict
Female choice
Female choice involves females assessing the fitness of males
When does genetic drift occur
Genetic drift occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
Why is genetic drift more important in small populations
Genetic drift is more important in small populations, as alleles are more likely to be lost from the gene pool
When do population bottlenecks occur
Population bottlenecks occur when a population size is reduced for at least one generation
When does founder effects occur
Founder effects occur through the isolation of a few members of a population from a larger population
What is the effect of founder effects on gene pool
The gene pool of the new population is not representative of that in the original gene pool
Why are gene pools altered by genetic drift
A gene pool is altered by genetic drift because certain alleles may be under represented or over represented and allele frequencies change
What is the rate of evolution when selection pressures are strong
Where selection pressures are strong the rate of evolution can be rapid
What are selection pressures
Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles
Biotic selection pressures
- competition
- predation
- disease
- Parasitism
Abiotic selection pressures
- changes in temperature
- light
- humidity
- pH
- salinity
What is fitness an indication of
Fitness is an indication of an individuals ability to be successful at surviving and reproducing.
What is fitness a measure of
Fitness is a measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species
What does fitness refer to in terms of gene pool
It refers to the contribution made to the gene pool of the next generation by individual genotypes
How can fitness be defined
Fitness can be defined in absolute or relative terms
What is absolute fitness
Absolute fitness is the ratio between the frequency of individuals of a particular genotype after selection to those before selection
Formula for absolute fitness
Frequency of a particular genotype after selection / frequency of a particular genotype before selection
What happens if the absolute fitness is 1
It the absolute fitness is 1, then the frequency of the genotype is stable
What does a value greater than one convey
A value greater than 1 conveys an increase in the genotype
What does a value less than 1 convey
A value less than 1 conveys a decrease in the genotype
What is 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
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
Co evolution
Co evolution is the process by which two or more species evolve in response to selection pressures imposed by each other
What is the effect of a change in the traits of one species to others
A Change in the traits of one species acts as a selection pressure on the other species
Where is co evolution frequently seen
Co evolution is frequently seen in pairs of species that have symbiotic interactions
Symbiosis
Co evolved intimate relationships between members of two different species
What is the impact of co-evolved relationships
The impacts of these relationships can be positive (+) negative (-) or neutral (0) for the individuals involved
Mutualism
Both organisms in the interaction are interdependent on eachother for resources or other services. As both organisms gain from the relationship the interaction is (+/+)
Commensalism
Only one of the organisms benefits (+/0)
Parasitism
The parasite benefits in terms of energy or nutrients and the host is harmed as the result of the loss of these resources (+/-)
What are mutualism commensalism and parasitism
Types of symbiotic interactions
What does the red queen hypothesis state
The red queen hypothesis states that in a co-evolutionary relationship change in the traits of one species can act as a selection pressure on the other species
How must red queen hypothesis species adapt
This means that species in these relationships must adapt to avoid extinction
