Evolution

Question 1

What occurs during evolution ?

Answer 1

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

Question 1

What is evolution ?

Answer 1

Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits

Question 2

What does natural selection act on ?

Answer 2

Natural selection acts on genetic variation in populations

Question 3

Where does variation in traits arise from ?

Answer 3

-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.

-Most mutations are harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual.

Question 4

What is natural selection ?

Answer 4

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

Deletrious = an allele which reduces an organisms fitness (so organism gets deleted)

Question 5

What is sexual selection ?

Answer 5

Sexual selection is the non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring

Sexual selection may lead to sexual dimorphism (Males typically being larger than females)

Question 6

What can sexual selection be due to ?

Answer 6

Sexual selection can be due to male-male rivalry and female choice

Male-male rivalry: large size or weaponry increases access to females through conflict.

Female choice involves females assessing the fitness of males.

Question 7

What is genetic drift ?

Answer 7

-Genetic drift occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next

-Genetic drift is more important in small populations, as alleles are more likely to be lost from the gene pool

-A gene pool is altered by genetic drift because certain alleles may be under-represented or over-represented and allele frequencies change

-Two important processes can have an effect on genetic drift; the bottleneck and founder effects.

Question 8

What is the bottleneck effect ?

Answer 8

Population bottlenecks occur when a population size is reduced for at least one generation (like by a forest fire or natural disasters)

Question 9

What are Founder effects ?

Answer 9

Founder effects 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.

Question 10

What are selection pressures and their effects on the rate evolution ?

Answer 10

-Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles.

-Where selection pressures are strong, the rate of evolution can be rapid

-They can be biotic: competition, predation, disease, parasitism; or abiotic: changes in temperature, light, humidity, pH, salinity.

Question 11

What does the Hardy-Weinberg (HW) principle state ?

Answer 11

-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

The conditions for maintaining the HW equilibrium are:
-No natural selection
-No mutation
-No gene flow (through migration, in or out).
-Large population size
-Random mating

Question 12

What can the HW principle be used to determine and calculate ?

Answer 12

-Can be used to calculate allele, genotype and phenotype frequencies in populations.
-The HW principle can be used to determine whether a change in allele frequency is occurring in a population over time, changes suggest evolution is occurring

p^2 + 2pq + q^2 = 1

Where,
p = frequency of dominant allele
q = frequency of recessive allele
p^2 = frequency of homozygous dominant genotype
q^2 = frequency of homozygous recessive genotype
2pq = frequency of heterozygous genotype
p+q = 1

Question 13

What factors can increase the rate of evolution ?

Answer 13

1) Selection pressures (biotic and abiotic)
2) Shorter generation time (time to complete one generation)
3) Sexual reproduction (increases variation and selection)
4)Horizontal gene transfers
5) Higher mutation rate

Question 14

How does selection affect allele frequencies

Answer 14

Selection results in the non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles (deleterious like gets deleted)

(Natural and sexual selection)

Question 15

What is fitness ?

Answer 15

-Fitness is an indication of an individual’s ability to be successful at surviving and reproducing

-Fitness is a measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species.

-It refers to the contribution made to the gene pool of the next generation by individual genotypes

Question 16

In what terms can fitness be defined ?

Answer 16

Fitness can be defined in absolute or relative terms

Question 17

What is absolute fitness ?

Answer 17

-Absolute fitness is the ratio between the frequency of individuals of a particular genotype after selection, to those before selection

-If the absolute fitness is 1, then the frequency of that genotype is stable. A value greater than 1 conveys an increase in the genotype and a value less than 1 conveys a decrease.

frequency of a particular genotype before selection

Question 18

What is relative fitness ?

Answer 18

-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

             number of surviving offspring per individual of a particular genotype  -------------------------------------------------------------------------------------------------------------------------------------------
       number of surviving offspring per individual of the most successful genotype

Question 19

What is co-evolution ?

Answer 19

-Co-evolution is the process by which two or more species evolve in response to selection pressures imposed by each other

-A change in the traits of one species acts as a selection pressure on the other species

Question 20

Where is co-evolution frequently seen ?

Answer 20

-Co-evolution is frequently seen in pairs of species that have symbiotic interactions

-Symbiosis: co-evolved intimate relationships between members of two different species.

-The impacts of these relationships can be positive (+), negative (-) or neutral (0) for the individuals involved

-Mutualism, commensalism, and parasitism are types of symbiotic interactions

Question 21

What are the types of symbiotic interactions ?

Answer 21

Mutualism, commensalism, and parasitism are types of symbiotic interactions

-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 (+/+).

-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 (+/-).

Question 22

What is the Red Queen Hypothesis and its implications ?

Answer 22

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

This means that species in these relationships must adapt to avoid extinction

(Sexual reproduction increases varitation)

Question 23

What does selection result in ?

Answer 23

Selection results in the non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles.