Lecture 18

Question 1

4 postulates of evolution by natural selection

Answer 1

Individuals within species are variable
Some of the variations are passed on to offspring
In most generations, more offspring are produced than can survive.
Survival and reproduction are not random: individuals with the highest reproductive success are those with the most favourable variations

Question 2

What does natural selection produce?

Answer 2

descent with modification

Question 3

What do fittest genotype do?

Answer 3

vary from population to population

Question 4

What does divergence of populations lead to?

Answer 4

speciation

Question 5

What is Neo-darwinian evolution

Answer 5

modern synthesis between mendel and darwin

Question 6

What happens in haploid species?

Answer 6

genotype = phenotype = individual

Question 7

What happens in diploid species?

Answer 7

genetic combinations are disrupted

during meiosis

Question 8

How does selection influence allele frequency?

Answer 8

Selection operates on alleles in relation to their average contribution to their own transmission through their action on the individuals that carry them

Question 9

Describe genotype-phenotype selection

Answer 9

Selection will operate to remove less fit variants, or

increase variants with greater fitness

Question 10

What does selection do for genotype-phenotype selection?

Answer 10

removes less fit variants or increase variants with greater fitness

Question 11

Recessive alleles

Answer 11

rare and present in heterozygotes and tend to persist

Question 12

Dominant alleles

Answer 12

always expressed so frequent, selection against them will remove recessive alleles

Question 13

What does mu stand for?

Answer 13

rate of mutation - frequency of rare recessive alleles in population

Question 14

Genetic drift

Answer 14

strongly affects rare alleles, change difference in transition of alleles leading to fluctuations in allele frequency, drift has greater influence on rate alleles than selection, gift is primary mechanisms for increasing rare recessives, responsible for changing frequencies of neutral mutation

Question 15

Founder effect

Answer 15

drift in small populations can produced biased allele frequencies

Question 16

What can frequency dependent selection do?

Answer 16

select for rare alleles

Question 17

What is fluctuating selection?

Answer 17

unstable, changeable environments selection favour opposing phenotypes/alleles over short timescales

Question 18

Fitness

Answer 18

Reproductive success of a genotype relative to the optimum genotype - survivorship and fecundity

Question 19

What is the equation for W

Answer 19

1-s

Question 20

What is S?

Answer 20

selection coefficient

Question 21

What does S do?

Answer 21

determines how fast allele frequencies change, when s is high allele frequencies change quickly

Question 22

Adaptive landscape

Answer 22

natural selection move a population towards peaks of hill
as the environmentalt changes, the adaptive peaks shift and populations follow a never-ending evolutionary journey
Y= fitness, x = allele

Question 23

Modes of selection on quantitative traits

Answer 23

Stabilising - intermediate variants are selected for, reduces variance of a trait - most common mode e.g. birth weight
Directional - individuals at one extreme are selected for, shifts the mean value of a trait - changing environments
Disruptive - individuals at both extremes leading to bimodal distribution - sympatric specification

Question 24

Sexual selection and sociobiology

Answer 24

Competition for mates(increases reproductive success), differences in investment of males and females

Question 25

Kin selection

Answer 25

changes in gene freq across generations driven by interactions between related individuals

Question 26

Coefficient of relatedness

Answer 26

r = (1/2)^n n= connection removed from self

Question 27

Hamiltons rule

Answer 27

Cost of not reproducing/ benefit of helping kin reproduce < relatedness
rB> C
r= relatedness to recipient of altruistic act defined as probability that a gene is picked randomly from each locus is identical by descent
B = additional reproductive benefit gained by recipient of the altruistic act
C = reproductive cost to the individual of performing the act

Question 28

Speciation

Answer 28

allopatric or sympatirc
species - group of organisms capable of interbreeding and producing fertile offspring
Reinforced by pre-mating isolation (behavioural choices)
post-zygotic isolation (hybrid inviability or sterility)