Evolution

Question 1

What is natural selection?

Answer 1

best adapted organisms survive and pass on their traits to their offspring

Question 2

What are Darwins assumptions

Answer 2

1. individuals within species are variable
2. some variations are passed onto offspring
3. in most generations, more offspring are produced that can survive
4. survival and reproduction are not random - survival of fittest

Question 3

What is evolution?

Answer 3

survival of the fittest
occurs because of changes in allele frequencies
fittest genotypes vary between populations
divergence of populations leads to speciation

Question 4

what is the modern synthesis of evolution?

Answer 4

considered in terms of changes in allele and gene frequencies over time, and the average action of selection on genotypes

Question 5

when does selection act on alleles?

Answer 5

in relation to their average contribution to their action on the individuals that carry them

acts on levels of individuals
transmission of alleles important

Question 6

When does selection operate?

Answer 6

to remove less fit variants, or increase variants with greater fitness

artificial selection
- humans affected genotypes of dogs & can remove and select for different phenotypes

Question 7

what is invasion of rare mutants?

Answer 7

new alleles are constantly created
dominant allele are always expressed, selection against will remove excess alleles

Question 8

What is genetic drift?

Answer 8

chance difference in transmission of alleles, leading to fluctuations in allele frequency
greater influence than selection
increases rare recessive alleles

Question 9

What is a genetic bottleneck?

Answer 9

random allele is lost
founder effect
significant as reduction of population
completely random and small surviving population

Question 10

what is balancing selection?

Answer 10

how variation is maintained in a population
selection both for and against

Question 11

what is frequency dependent selection?

Answer 11

Rare alleles producing unusual phenotypes may be predated on less than those with the main allele
Alleles can become common and predators learn their patterns

Question 12

what is fluctuating selection?

Answer 12

also select for rare alleles
unstable and changeable
may favour opposing phenotypes over short timescales

Question 13

what is fitness?

Answer 13

Used to measure reproductive success, described as the ability to both survive and reproduce and is equal to average contribution of the gene pool of the next generation that is made by an average individual of the specified genotype of phenotype.

Question 14

what ate the methods for measuring fitness?

Answer 14

1. relative survival of genotypes within a generation
2. changes in gene frequencies between generations
   deviations from hardy-weinburg ratios

Question 15

what is fitness equation?

Answer 15

W = 1 -s
w is fitness
s is selection

Question 16

selection determines how fast allele frequencies change

Answer 16

when s is high, allele frequencies change rapidly

Question 17

selection example

Answer 17

peppered moths
mark release recapture experiments and found dark forms adapted to survive in industrial revolution

Question 18

mark release recapture technique

Answer 18

tested how well survived in different environments
recapture allows to see survival rate
assume optimal survivorship
ca then calculate selection coeffecient

Question 19

what is an adaptive landscape?

Answer 19

natural selection tends to move populations towards peaks of hills

never ending evolutionary journey
visualise relationship between genotypes and phenotypes

Question 20

what is stabilising selection?

Answer 20

stabilises a population
intermediate variants are selected for
most common

Question 21

what is directional selection?

Answer 21

individuals at one extreme are selected for
shift

Question 22

what is disruptive selection?

Answer 22

individuals at both extremes are selected for
bimodal distribution

Question 23

what is sexual selection?

Answer 23

competition for mates
maximises reproductive success
even at potential cost to survival
extreme case of natural selection

Question 24

what does kin selection refer to?

Answer 24

changes in gene frequency across generation driven by interactions between related individuals

Natural selection of genes that tend to cause the individuals bearing them to be altruistic to close relatives
helping your relatives, even at a cost to yourself, you may be promoting the success and transmission of genes that you share in common

Question 25

what is the coefficient of relatedness?

Answer 25

parent transmits 50% of genetic information to offspring
100% relatedness to self
50% to each parent
every time take step back in relation, halves

Question 26

what is Hamiltons rule?

Answer 26

fitness as the number of an individuals allele in the next generation
notion of inclusive fitness

Question 27

what leads to relatedness?

Answer 27

cost of not producing / benefit of helping kin reproduce
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Question 28

Hamiltons rule equation

Answer 28

rB<C

r= probability gene picked randomly is identical by descent
B= additional reproductive benefit
C= reproductive cost to individual

promotes passing of genes from one generation to the next

Question 29

what is phylogenetic?

Answer 29

estimating relatedness between species based on sequence data
relatedness between species

Question 30

how do you read phylogenic tree?

Answer 30

distance between nodes important for relationships
nodes are flexible and individual taxon can move around the tree

Question 31

what can phylogenetic be used to do?

Answer 31

use molecular genetics to infer relatedness
homologous genes to create a tree

Question 32

what are paralogous genes?

Answer 32

arise through duplications in the genome
different genes created

Question 33

what are orthologous genes?

Answer 33

genes that have split when new species have been formed
want orthologous as have the same function

Question 34

What is a species?

Answer 34

a group of organisms capable of interbreeding to produce fertile offspring
occur at node in phlyogenetic trees

Question 35

what’s allopatric speciation?

Answer 35

different places leading to speciation
separate by location

Question 36

what’s sympatric speciation?

Answer 36

same geographical location but have managed to diverge

Question 37

what is speciation reinforced by?

Answer 37

pre-mating isolation:
behavioural choices, spatial constraints

post-zygotic isolation:
availability, hybrid sterility