Phylogeny

Question 1

Forces that drive allele frequency change

Answer 1

Migration and gene flow
genetic drift
non-random mating

Question 2

Migration and gene flow

Answer 2

-Movement of genes as a result of movement of populations to different regions
-Genetic differences reduced and genetic variation is increased due to interbreeding
-over time, it substantially aleter gene freqeuncy

Question 3

E.Migration

Answer 3

B allele of ABO blood group present in a low gradient from east to west due to migration of Mongols over Europe

Question 4

Genetic Drift

Answer 4

-Chance alone can vause fluctuations in allele frequency
-Includes Founder effect and genetic bottleneck
-Surviving alleles are random and not due to genetic advantage

Question 5

Founder effect

Answer 5

-Small migration of people with a specific allele that populate an area to create a large population all containing same allele
-Genes carried by all memebers of pop derived fro same founders

Question 6

Genetic Bottleneck

Answer 6

Large population undergoes drastic but temporary reduction in numbers
-Genetic diversity reduced even after pop recovers
-Usually a catastrophic event occurs

Question 7

Non-random mating

Answer 7

Alters genotype freqeuncy (hetero vs homo) but not allele frequency
-Selection for or against certain traits has the potential to affect overall allele frequencies but does not itself directly change allele frequencies

Question 8

Positive assortative mating

Answer 8

Similar genotypes more likely to mate than dissimilar ones
-part of non-random mating

Question 9

Negative assortative mating

Answer 9

Dissimilar genotypes more likely to mate

Question 10

Inbreeding

Answer 10

Mating between closely-related individuals, such as relatives
-Selects for homozygous phenotype

Question 11

species

Answer 11

A group of actually or potentially interbreeding organisms that is reproductively isolated in nature from all other such groups
-Members are able to interbreed and produce viable offspring

Question 12

Speciation

Answer 12

Transforms the parental species into another species or divides a single species into two or more seperate species

Question 13

Speciation event requirements

Answer 13

Changes in morphology, physiology and adaptions to ecological niches may occur but are not neccessary for itto occur

Question 14

genetic divergence

Answer 14

Different allele frequencies or alleles in gene pools reflective of forces such as natural selection, mutation and genetic drift
-When gene flow is absent/reduced- population can diverge to the point that members of one population are no longer able to successfully interbreed with members of the other.

Question 15

Reproductive Isolating mechanisms

Answer 15

Prezygotic mechanisms
Postzygotic mechanisms

Question 16

Prezygotic mechanisms

Answer 16

-Prevents fertilisation and zygote formation
-Geographic or ecological
-Seasonal or temporal
-Behavioural
-Mechanical
-Physiological

Question 17

Geographic or ecological

Answer 17

The pop lives in the same regions but occupy different habitats

Question 18

Seasonal or temporal

Answer 18

Pop live in the same regions but are sexually mature at different times

Question 19

Behavioural

Answer 19

Only in Animals
The pop are isolated by different and incompatible behaviour before mating

Question 20

Mechanical

Answer 20

Cross-fertilization is prevented or restricted by differences in reproductive structures ( genitalia in animals, flowers in plants)

Question 21

Physiological

Answer 21

Gametes fail to survive in alien reproductive tracts
sperm cant survive in female

Question 22

Postzygotic isolating mechanisms

Answer 22

Fertilisation takes place and hybrid zygotes are formed but these are nonviable or give rise to weak or sterile hybrids
-Hybrid nonviability or weakness
-Developmental hybrid sterility
-Segregational hybrid sterility

Question 23

Developmental hybrid sterility

Answer 23

Hybrids are sterile because gonads develop abnormally or meiosis breaks down before completion

Question 24

Segregational hybrid sterility

Answer 24

Hybrids are sterile because of abnormal segregation into gametes of whole chromosomes, chromosome segments, or combinations of genes

Question 25

Rate of macroevolution

Answer 25

Average time is 100 000 to 10 000 000 years -Rapid selection in shorter time spans observed in fish in East African laeks like marine salmon and palm trees in isolated islands

Question 26

Phylogeny

Answer 26

-Genetic differences or similarities among present-day species used to reconstruct evolutionary histories -Branches represent relationships among lineages over time length if branch represents length of time between speciation events -Branch nodes: when a species split into two or more species -Node: common ancestor of species diverging from node -Tips of branches: Species alive today or those that ended in extinction

Question 27

Monophyletic group

Answer 27

Ancestral species and all of its descendants

Question 28

Sources of phylogeny tree creation

Answer 28

Differences in the morphology of living organisms fossils molecular sequences of DNA protein RNA NB: only one source can create on tree

Question 29

Constructing of phylogeny trees from DNA

Answer 29

1.DNA sequences representing either a gene or genome of a large number of different species must be acquired 2.Sequences are aligned with each other so relative parts of sequence can be compared to see if they are the same or different. Software can be used to maximise the number of aligned base pairs by inserting gaps as needed. Closely related species will have fewer differences and more distantly related species would have acquired more DNA differences due to longer time elapsed. 3.DNA differences used to construct a phylogenetic tree, beginning with most closely related species and working back to those less closely related

Question 30

Molecular clock

Answer 30

Measure rate of evolutionary change Use rate of change of amino acid or nucleotide sequences to estimate divergence from common ancestor can only be used if they are linear over certain time scales Time and dates added to clock using independent evidence such as the fossil record

Question 31

Origins of Human Genome

Answer 31

Homo sapiens arose 300 000 years ago from earlier species of Homo sapiens migrated out of Africa between 50 000 and 70 000 years ago Other homo species occupied parts of Europe and Asia Genomes from Neanderthals and humans are 99.7% identical

Question 32

Interbreeding of human populations

Answer 32

neanderthals disappeared 40 000 years ago and coexisted with humans for 30 000 years 2% of all human DNA is made of Neanderthal DNA Almost 20% of Nenderthal genome present in non-African population Neanderthal are not direct ancestors as we interbrd with them Since different populations have different amounts of N DNA, it gives additional evidence that we did not evolve from them Denisovans are another type of homo that are more closely related to sapiens than N and were found in Siberia, 44-54 thousand years ago it entered our DNA Denisovan DNA mainly found in high quanitities in island nations like Fuji and Australians

Question 33

% of Denisovan DNA

Answer 33

Modern humans have 5-6% DNA from Melanesian islanders, derived from Denisovans