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Genes, Evolution and Development > Evolution > Flashcards

Evolution Flashcards

1
Q

What 4 scientists are associated with the discovery of evolution?

A

Duffon, Cuvier, Lamarck and Darwin

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2
Q

what are the 3 conditions of evolution by natural selection?

A
  • heritable characters
  • characters show variation between individuals
  • differential fitness (survival allowing for reproduction)
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3
Q

Define evolution

A

genetic change over time (change in allele frequencies) in a population

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4
Q

is all evolution caused by natural selection?

A

no

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5
Q

What do you call species dividing and changing?

A

speciation

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6
Q

what force consistently produces adaptations?

A

natural selection

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7
Q

what are the 5 pieces of evidence for evolution?

A
  • fossils
  • imperfection
  • bio-geography
  • molecular genetics
  • natural selection in action
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8
Q

what defines geological periods?

A

mass extinctions e.g. dinosaurs by asteroid

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9
Q

How can fossils of trilobites show evolution?

A

they became extinct around 250 million years ago. Fossils of these creatures show clear signs of evolutionary change in the species over 3 million years (relatively quick in evolutionary terms)

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10
Q

Give an example of unintelligent design?

A

the appendix in humans

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11
Q

Give an example of natural selection in action..

A

peppered moths in the industrial revolution

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12
Q

What’s the sole carrier of genetic material?

A

DNA

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13
Q

What is meant by the DNA code being universal?

A

it has the same cellular machinery for decoding and copying genetic information

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14
Q

What can looking at DNA of different organisms show?

A

a common ancestor

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15
Q

What are molecular clocks?

A

a technique that pairs species compared for the same protein coding

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16
Q

what’s molecular phylogenetics?

A

looking at molecules and the genes that code for them

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17
Q

What has molecular phylogenetics supported?

A

morphological data (anatomy/physiology)

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18
Q

What is neutral theory?

A

the idea that genetic code is redundant (some mutations in genetic code won’t change the amino acid chain therefore won’t change any phenotypes)

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19
Q

Give 2 definitions of life..

A

any 2 from

  • the flow of matter, energy and information
  • where homeostasis occurs
  • localised negative entropy (order as opposed to disorder)
  • MRSGREN
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20
Q

How old is earth?

A

4 billion years old

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21
Q

How was the earth created?

A

bombardment bringing water and destruction

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22
Q

How was the young sun different?

A

higher UV levels- more UV on the earth’s surface

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23
Q

When did life first appear?

A

3.8 billion years ago

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24
Q

What’s the most likely way life first appeared?

A

In the deep sea at alkaline hydrothermal units where alkaline and acidic water meet, allowing the protons giving energy to fuel the first replicating molecules from these proton gradients

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25
Q

What did the first sources of life use as genetic material?

A

RNA

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26
Q

Draw a flow-chart showing how life’s form changed

A

complex molecules from random chemistry –> RNA –> Proteins –> DNA

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27
Q

when did amino acids first start being incorporated into life?

A

after the RNA world

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28
Q

what is LUCA

A

Last Universal Common Ancestor

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29
Q

What’s more fragile DNA or RNA?

A

RNA

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30
Q

why did cells first form?

A

DNA needed protection as it’s fragile

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31
Q

What is normally needed for life to exsist? (4)

A
  • cool temperatures
  • water
  • gravity
  • protection from radiation
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32
Q

When did the great oxidation event occur on earth?

A

around 2.5 billion years ago

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33
Q

What’s the theory of the cause of the great oxidation event?

A

the first prokaryotes were producing methane and cyanobacteria were producing oxygen, which the methanogenic bacteria were consuming. some event caused a mass death of methogenic bacteria and oxygen producing bacteria dominate

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34
Q

What are the main cellular features of eukaryotes? (4)

A
  • nucleus
  • mitochondria
  • choroplast (in plants)
  • golgi bodies
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35
Q

What do eukaryotes have that prokaryotes don’t?

A

membrane-bound organelles

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36
Q

What’s bigger pro or eukaryotes?

A

Eukaryotes

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37
Q

are some eukaryotes multicellular?

A

yes

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38
Q

when did eukaryogenesis happen? How many times?

A

26 billion years ago. once

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39
Q

How did eukaryogenesis probably occur?

A

an archaebacterium engulfing heterotrophic eubacteria (eubacteria eventually became mitochondria)

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40
Q

Are mitochondria a product of natural selection?

A

no (they appeared as a chance event)

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41
Q

What’s the Cambrian explosion?

A

The sudden appearance of several fossils from the same time period

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42
Q

Give an example of animals that came from the cambrian era..

A

arthropods, chordates and worms

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43
Q

Why did the cambrian explosion happen?

A

A physiological change in organisms led to dissolved oxygen levels allowing for an active lifestyle. Geographical change with new seas and new niches. There was a geochemical change when sea levels changed allowing an abundance of trace metals to make exoskeletons

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44
Q

How long ago were the dinosaurs wiped out?

A

66 million years

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45
Q

what did the disappearance of the dinosaurs allow?

A

other large reptiles, mammals and birds had ecological space to evole

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46
Q

how long do ecosystems generally take to recover from mass extinction?

A

20 million years

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47
Q

define a species..

A

A population of reproducing organisms that is isolated from other populations

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48
Q

Why is the definition of a species not all-encompassing?

A

it doesn’t work for prokaryotes and eukaryotes that don’t strictly reproduce sexually. It also can’t be used when looking at fossils of extinct species or for bacteria/archaea

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49
Q

simply, what is allopatric speciation?

A

speciation due to Geographical isolation (allo- other, patric- homeland)

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50
Q

what’s the typical mode of speciation?

A

allopatric

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51
Q

What’s directional selection?

A

where the population gradually changes due to a selection pressure to favour a single ‘extreme’ phenotype

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52
Q

What’s distruptive selection?

A

where the 2 extreme (most different/ opposite) phenotypes are favoured over the intermediate one

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53
Q

What’s stabilizing selection?

A

where the intermediate/’middle’ phenotype is favoured over the either ‘extreme’ phenotypes

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54
Q

What’s genetic drift?

A

where the variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce

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55
Q

why is genetic drift unlikely to happen in large, randomly mating populations?

A

they have low chances of large fluctuations and more of each allele

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56
Q

What are founder effects/ bottlenecks?

A

when there’s reduced genetic diversity due to a population being descended from a small number of colonising ancestors

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57
Q

what is sympatric speciation?

A

speciation which occurs when the new and old species are living in the same geographical location (sym-same, patra- homeland)

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58
Q

what clearly shows sympatric speciation

A

plants can show polyploid speciation

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59
Q

what’s the mean time for speciation to occur?

A

5 million years

60
Q

why is isolation key for speciation?

A

it prevents gene flow between the populations

61
Q

what are prezygotic barriers?

A

a mechanism that prevents reproduction pre-mating

62
Q

give 2 examples of prezygotic barriers?

A

2 from:

  • different habitat locations
  • temporal isolation (breeding/mating at different times)
  • behavioural isolation e.g. differences in mating/courtship behaviour
63
Q

What are postzygotic barriers?

A

a mechanism that prevents reproduction after or during mating

64
Q

give 2 examples of postzygotic barriers..

A

any 2 from:

  • mechanical isolation (physically cannot mate)
  • genetic isolation- gametes don’t ‘work’ together
  • infertile hybrids
65
Q

What’s microevolution?

A

changes in the gene pool of an organism over time

66
Q

what’s a gene pool?

A

all the alleles of all the genes in the individuals of a population

67
Q

What’s macroevolution?

A

evolution of a grand scale

68
Q

what 2 factors are required for evolution by natural selection?

A

1) differential reproductive success

2) differences between organisms

69
Q

What was darwin’s main issue?

A

he came up with the theory of evolution, however he did not have a mechanism for it

70
Q

who first began to give explanations of how genes pass from one generation to the next (inheritence)?

A

gregor mendel

71
Q

what is the study of microevolution called?

A

population genetics

72
Q

What 5 things can population genetics tell us?

A

1) how human pathogens are evolving e.g. bacteria which are antibiotic resistant like MRSA
2) How humans have evolved in response to pathogens
3) how much genetic diversity is present in a population
4) genetic structure of a population
5) response of population to change e.g. climate change

73
Q

How does population genetics study gene pools?

A

by looking at a gene locus model (it’s impractical to study a whole population)

74
Q

How does one measure the allele frequency and genotype frequency?

A

number of one type of allele/ total number of alleles (double the number of organisms if the organism is diploid)

75
Q

what’s the equation for when allele frequencies reach an equilibrium?- what do the symbols stand for?

A

p2+2pq+q2=1- The Hardy- Weinberg equation
p2- RR homozygotes
2pq- Rr heterozygotes
q2- rr homozygotes

76
Q

If an equilibrium is reached in alleles, it will stay the same if which 5 factors exist?

A
  • population size is large
  • mating is random
  • no migration from other populations
  • no selection
  • no mutation
77
Q

What 4 factors change allele frequency?

A
  • genetic drift (in small populations)
  • non- random mating
  • migration
  • selection
78
Q

What’s neutral theory?

A

many alleles are selectively neutral and their frequencies will fluctuate randomly over time

79
Q

What’s selection theory?

A

the idea that the selection of combinations of traits in an organism trade-off between quantity and quality of offspring

80
Q

How many base pairs do humans have?

A

3x10^9

81
Q

what percent of all the human base pairs code for proteins?

A

3

82
Q

what percent of our base pairs are regulatory genes?

A

10%

83
Q

what percent of our base pairs are remnants of transposons?

A

45

84
Q

what are transposons?

A

parts of DNA which move around, may be remnants from a viral infection

85
Q

what percent of our base pairs are ‘junk’?

A

85

86
Q

what is ‘junk’ DNA?

A

DNA which if deleted would have no effect on fitness

87
Q

how much do humans differ in DNA from eachother?

A

by 0.1% (trivial amount- could relate to altruism)- most these differences are in junk DNA

88
Q

what percent of our DNA is from retroviruses?

A

8

89
Q

are we still evolving?

A

yes

90
Q

give one piece of evidence that shows humans are still evolving..

A

1 of:

  • a study of 50 tibetans who live at 4000m altitude (where there’s 40% less oxygen), who have lived there for 2750 years were compared with Han chinese people who live there too but migrated more recently. scientists found that the gene EPAS1 (that controls blood cell production) is mutated in 87% of the tibetans but only 9% of han chinese.
  • genetic difference found in bajau people who dive for long periods while holding their breath. this genetic difference allows them to hold their breath longer
91
Q

where’s the largest genetic variation in humans seen?

A

africa

92
Q

what happens to genetic variation as you get further away from Africa?

A

it reduces

93
Q

why does genetic variation reduce the further from africa you go?

A

as humans migrated, the gene pools reduced as smaller groups were travelling far away

94
Q

In how many waves did humans leave africa?

A

2

95
Q

when were the 2 waves of humans leaving africa?

A

the first was 100,000 years ago the second was 60,000 years ago

96
Q

what happened during the first wave of humans leaving africa?

A

they migrated to china, however died out as they have no living descendants

97
Q

what happened during the second wave of humans leaving africa?

A

they succeeded in colonising the rest of the world

98
Q

what was found when looking at 6 genomes from all over the world?

A

there was a bottleneck 70,000 years ago where the entirety of the human population was composed of 12000 individuals who we all descend from

99
Q

why did the bottleneck 70,000 years ago happen?

A

may be due to climate change

100
Q

at what sort of rate did humans travel out of africa?

A

around 1km per year (very gradually)

101
Q

How were neanderthals physically different?- give 3

A

any 3 from:

  • more prominent brow
  • larger teeth
  • shorter
  • broader
  • physically stronger
102
Q

where did neanderthals live?

A

in large areas around the world

103
Q

when did homosapiens overlap with neanderthals?

A

5000 years ago

104
Q

are neanderthals our direct ancestors?

A

No- our cousins

105
Q

were neanderthals intelligent?

A

more so than previously though

106
Q

where did the last group of neanderthals live?

A

Gibraltar

107
Q

what was found found when the neanderthal genome was sequenced in 2010?

A

non-african homosapiens interbred with neanderthals, therefore by the biological definition of species, we’re not a different species
around 3% of homosapien non-african DNA is neanderthal

108
Q

How were denisovans discovered?

A

In 2011 from teeth that weren’t ours or neanderthal- more artefacts of them have been found since

109
Q

did homosapiens mate with denisovans?

A

yes

110
Q

are we or neanderthals more closely related to denisovans?

A

neanderthals

111
Q

how do denisovans and tibetans link?

A

the EPAS1 genes tibetans living at high altitude have is beleieved to be from denisovans

112
Q

were denisovans and neanderthals mating?

A

yes- hybrids were found

113
Q

what’s different about homosapiens to other human species?

A
  • we have a history of art e.g. cave wall art
  • we invented many tools
  • there’s a correlation between humans arriving in different areas worldwide and species of megafauna (large animals) becoming extinct
114
Q

define fitness.

A

the relative probability of survival and reproduction of a given genotype

115
Q

is fitness easy to calculate precisely?

A

no

116
Q

what affects survival and reproduction?

A

environmental conditions (which change in time and space e.g. dinosaurs fit until meteor strike)

117
Q

can fitness come down to a single allele?

A

no

118
Q

how is the sickle cell allele driven survival?

A

those who are heterozygous for the disease aren’t affected by malaria- making this advantgeous in parts of africa but not europe or america (unfit alleles are sometimes preserved)

119
Q

what is evolution?

A

change in allele frequency

120
Q

are phenotypes and genotypes always directly linked? why?

A

no. because environmental factors can affect phenotypes

121
Q

are species selected?

A

no, individuals within the species are

122
Q

What’s Runaway sexual selection?

A

The idea that certain traits (usually in males) are preferable to females e.g. large peacock tails, to the point where the genes for these are passed down, as the trait increases reproduction likelihood e.g. the peacock tail size increases

123
Q

Why can runaway sexual selection only exist up to a point?

A

because eventually the trait change can be maladaptive e.g. large peacock tail means more likely to be killed by predators

124
Q

What are most social insects (sexually)?

A

sterile- only the queen reproduces

125
Q

What affects who will be the queen in social insects?

A

environmental factors

126
Q

How do insects act?

A

Altruistically

127
Q

What did Bill Hamilton study?

A

Altruistic species

128
Q

What’s Hamilton’s rule?

A

The evolutionary strategy that favours the reproductive success of the organisms relatives/species, even at the cost of the organisms own survival/reproduction

129
Q

Is there likely to be a gene for altruism?

A

no

130
Q

What could Hamilton’s rule explain about humans?

A

the widespread prevalence of altruism in the human world

131
Q

where are the Galapagos islands?

A

approx. 1000km from the coast of Ecuador

132
Q

What separates the Galapagos islands from S.America?

A

deep water

133
Q

The fact that deep water separates the Galapagos islands and S.America means that…

A

terrestrial species on the islands won’t have many relatives nearby, neighbouring islands will have a few close relatives
there’s very little gene flow between the islands and mainland

134
Q

When did charles darwin explore the galapagos islands?

A

1835

135
Q

What’s an endemic species?

A

A species only found in one habitat e.g. galapagos finches are endemic to these islands

136
Q

what did Darwin notice about the galapagos finches?

A

the shape of the bill (beak) of each species was adapted to its particular ecology

137
Q

what did peter and rosemary grant do?

A

studied the galapagos finches for the past 30 years

138
Q

What was the first stage of evolution of the eye?

A

an isolated photoreceptor allows an animal to monitor the intensity of ambient light

139
Q

what was the second stage of evolution of the eye?

A

animals can tell where the light is coming from- photoreceptors gain a shield giving the owner a pixel sense of the world (allows animal to move towards or away from light source)

140
Q

What was the third stage of evolution of the eye?

A

shielded photoreceptors cluster in groups, each pointing in a slightly different direction, allows the integration of different information, at this point photoreceptors become eyes

141
Q

what was the fourth stage of evolution of the eye?

A

lenses are added to allow focusing of the light- vision becomes sharp and detailed

142
Q

what did Ernst Mayr claim about the origins of eyes?

A

they had 40-65 independent origins

143
Q

what did walter gehring argue about the evolution of the eye? and why?

A

that they evolved just once- after he discovered that the same master gene (pax6) controls eye development in virtually every creature with eyes

144
Q

who was right about eyes mayr or gehring?

A

both partially

145
Q

what are eyes all made up of?

A
  • opsins
  • lenses
  • retinas
  • bundled nerve fibres
146
Q

sympatric speciation that involves a hybrid between 2 related species is known as?

A

an allopolyploid

Genes, Evolution and Development (3 decks)

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