Unit 2 - Evolution Flashcards
What is evolution?
Evolution is the change over time in the
proportion of individuals in a population
differing in one or more inherited traits
What are examples of non-random processes of evolution?
natural selection and sexual selection,
What are examples of random processes of evolution?
genetic drift
What does natural selection act on?
genetic variation in
populations
What are mutations?
Variation in traits arises as a result of mutation. Mutation is the original source of new sequences of DNA. These new sequences can be novel alleles.
What can mutations be?
Most mutations are harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual.
What happens during natural selection?
-Populations produce more offspring than the
environment can support
-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.
What is sexual selection?
Sexual selection is the non-random process
involving the selection of alleles that increase
the individual’s chances of mating and
producing offspring
What can sexual selection many lead to?
Sexual Dimorphism
What determines sexual selection?
Sexual selection can be due to male-male
rivalry and female choice
What is male-male rivalry
Male-male rivalry: large size or weaponry
increases access to females through conflict.
What is female choice?
Female choice involves females assessing
the fitness of males.
What is genetic drift?
Genetic drift occurs when chance events
cause unpredictable fluctuations in allele
frequencies from one generation to the next
When is genetic drift more present?
Genetic drift is more important in small
populations, as alleles are more likely to be
lost from the gene pool
What is the population bottlenecks?
Population bottlenecks occur when a
population size is reduced for at least one
generation.
What is the founder effect?
Founder effects occur through the isolation of
a few members of a population from a larger
population.
In the founder effect what does the gene pool represent?
The gene pool of the new
population is not representative of that in the
original gene pool.
Why is the gene-pool altered by genetic drift?
certain alleles may be underrepresented or over-represented and allele frequencies change
What does it mean if the 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.
What are examples of selection pressures?
They can be biotic: competition, predation,
disease, parasitism; or abiotic: changes in
temperature, light, humidity, pH, salinity.
What does the Hardy-Weinberg principle state?
The Hardy-Weinberg (HW) 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
and no gene flow (through migration, in or
out).
What can the HW principle used to determine?
The HW principle can be used to determine
whether a change in allele frequency is
occurring in a population over time
What is the HW equation?
p^2 + 2pq + q^2 = 1
What does it mean if there is a change in the HW principle?
Changes suggest evolution is occurring
What is fitness?
Fitness is an indication of an individual’s
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?
It refers to the contribution made to the gene
pool of the next generation by individual
genotypes
What it Absolute fitness?
Absolute fitness is the ratio between the frequency of individuals of a particular genotype after selection, to those before selection
What is the equation for absolute fitness?
frequency of a particular genotype after selection/ frequency of a particular genotype before selection
What does it mean if the absolute fitness is 1?
If the absolute fitness is 1, then the frequency
of that genotype is stable
What does it mean if the absolute fitness is greater than 1?
A value greater than 1 conveys an increase in the frequency
of that genotype
What does it mean if the absolute fitness is less than 1?
and a value less than 1 conveys a in the decrease frequency
of that genotype
What is the 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
What is the equation of 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?
Co-evolution is the process by which two or
more species evolve in response to selection
pressures imposed by each other
In Co-evolution what happens when there is a change in traits?
A change in the traits of one species acts as
a selection pressure on the other species
What does Symbiosis mean?
: co-evolved intimate relationships
between members of two different species
What can be the impacts of symbiotic relationships?
positive (+), negative (-) or neutral (0) for the
individuals involved
What is Mutualism?
both organisms in the interaction
are interdependent on each other for
resources or other services. As both
organisms gain from the relationship, the
interaction is (+/+).
What is commensalism?
only one of the organisms
benefits (+/0).
What is 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 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
What does the Red Queen Hypothesis mean?
This means that species in these
relationships must adapt to avoid extinction
