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BIO 1210 > Evolution > Flashcards

Evolution Flashcards

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1
Q

Approximately when did the planet form?

A

~4.6 bya

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2
Q

What were the initial conditions of the planet?

A

Much hotter
No oxygen
Lots of UV, lightning, volcanoes and meteorites
No life

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3
Q

What is the 4 step hypothesis of how life evolved?

A
  1. Organic monomers were synthesized abiotically
  2. polymers formed abiotically
    - ex. proteins, nucleic acids
  3. molecules were packaged into protocells
  4. molecules formed that made inheritance possible
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4
Q

Where would the energy have come from to abiotically synthesize organic molecules when life began to form?

A

UV and lightning

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5
Q

How could some organic molecules have arrived on Earth?

A

On meteorites

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6
Q

Which element, that was abundant on Earth pre-life, has been recently found to catalyze metabolic reactions?

A

Ferrous iron

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7
Q

Define protocells

A

Droplets of fluid with membranes that maintained internal chemistry different from their surroundings

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8
Q

T or F: protocells could form abiotically and divide and grow?

A

True

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9
Q

What is an example of a molecule that made inheritance possible?

A

Self-replicating RNA molecules

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10
Q

What was likely the first hereditary material? Why?

A

RNA because it is simpler than DNA and easier to form abiotically

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11
Q

What enzymes formed when RNA was formed?

A

Ribozymes (RNA enzymes)

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12
Q

Overtime, what became the universal genetic material instead of RNA? Why?

A

DNA because it is more stable and can be more accurately copied

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13
Q

What is the general timeline for evolution of life on Earth?

A
  1. 3.5 bya: Prokaryotes (stromatolites)
  2. ~3.9 bya: Single cells may have evolved earlier
  3. ~2.7 bya: Photosynthetic prokaryotes
  4. 2.1 bya: single-celled eukaryotes
  5. 1.2 bya: multicellular eukaryotes
  6. 1 bya: prokaryotes colonized land
  7. ~500 mya: larger life forms colonized land
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14
Q

How long ago did prokaryotes evolve? What is the evidence that supports this?

A

at least 3.5 bya

Earliest evidence is fossilized stromatolites

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15
Q

What are stromatolites?

A

Layered rocks formed by prokaryotes that are likely the first form of life to evolve

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16
Q

How long ago may single cells have evolved? Why is there less evidence for this?

A

~3.9 bya

Less evidence because they’re simpler than prokaryotes and may not have fossilized well

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17
Q

How long ago did photosynthetic prokaryotes evolve?

A

~2.7 bya

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18
Q

What atmospheric change did the evolution of photosynthetic prokaryotes cause?

A

An increase in atmospheric oxygen

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19
Q

How long ago did single-celled eukaryotes evolve?

A

2.1 bya

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20
Q

What atmospheric change did the evolution of single-celled eukaryotes cause?

A

A more rapid increase in oxygen levels

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21
Q

How long ago did multicellular eukaryotes evolve?

A

At least 1.2 bya

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22
Q

How long ago did prokaryotes colonize land?

A

Over 1 bya

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23
Q

How long ago did larger life forms colonize land?

A

~500 mya

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24
Q

How did Darwin define evolution?

A

As descent with modification

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25
Q

What is the current definition of evolution?

A

A change in the genetic composition of a population from generation to generation

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26
Q

Define Darwinism

A

the hypothesis of natural selection proposed by Darwin

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27
Q

T or F: Darwin’s hypothesis of natural selection is now an accepted theory

A

True

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28
Q

What was the accepted paradigm during Darwin’s time for species?

A

That species had a fixed form (ie, they do not evolve over time)

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29
Q

What field of science did Georges Cuvier develop?

A

Palaeontology (study of fossils)

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30
Q

What were Cuvier’s 2 biggest discoveries?

A

He found that the older the layer of rock, the greater the differences between fossils and current life forms

That species appeared and disappeared in different layers of rock

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31
Q

What was Cuvier’s proposal for why species appeared and disappeared in rock layers?

A

This was due to local catastrophes rather than that species change over time (he rejected evolution)

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32
Q

What field of science did Charles Lyell study?

A

Geology

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33
Q

What did Lyell propose?

A

That the mechanisms of change are constant over time and that geological processes always operate at the same rate

over time, small changes can add up to a substantial change (ex. a river carving a canyon)

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34
Q

Who was Lyell’s work based on?

A

James Hutton, another geologist

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35
Q

What 2 things did Darwin reason from Lyell and Hutton’s work?

A
  1. the earth was much older than a few thousand years (as was previously thought)
  2. a slow and similar process (to geological processes) might change life forms
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36
Q

What did Jean-Baptiste Lamarck study?

A

Compared living species with fossil forms

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37
Q

What 2 things did Lamarck find in his studies?

A

He found several lines of descent where fossils led to living species

Organisms’ environmental suitability can be explained by gradual evolutionary change

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38
Q

What was Lamarck’s proposed hypothesis of evolution?

A

Body parts that were used became larger and stronger and those unused deteriorated

And that organisms could pass on these modifications to their offspring

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39
Q

What is Lamarckism?

A

Organisms can pass on their individual modifications to their offspring

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40
Q

What is wrong with Lamarck’s conclusions?

A

Frequently used body parts will not become larger or stronger during an individual’s life time

and the hypothesis of evolution is wrong at the organismal level

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41
Q

What did Charles Darwin do on his voyage around South America on the Beagle?

A

Observed and collected thousands of organisms

Noted that organisms were always well suited to their environment

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42
Q

What did Darwin discover about the Andes? What conclusion did this lead him to draw?

A

He found fossils of oceanic organisms up in the Andes and concluded that because earthquakes can lift rocks, the fossil containing rocks must have been at sea level and were lifted by earthquakes over time

This meant that the Earth had to be older than a few thousand years

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43
Q

What did Darwin notice about the species on the Galapagos Islands? What did this lead him to conclude?

A

They were unique but still resembled those on the mainland

He hypothesized that the islands were colonized by mainland organisms that diversified and gave rise to new species

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44
Q

What is an example of the differences Darwin noticed between finches of different islands of the Galapagos?

A

Beaks of finches were adapted for food sources on each island

ex. cactus-eater vs insect-eater vs seed-eater all have different beaks

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45
Q

Define adaptation

A

Inherited characteristics of organisms that enhance their survival and reproduction in specific environments

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46
Q

What did Darwin hypothesize as a cause of speciation?

A

Populations in a new area can accumulate new adaptations

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47
Q

What do adaptations arise from?

A

natural selection

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48
Q

Define natural selection

A

A process in which individuals in a population that have certain inherited traits will survive and reproduce at greater rates than individuals without the traits

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49
Q

What was the name of the other naturalist who was also studying evolution at the same time as Darwin?

A

Alfred Russel Wallace

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50
Q

What year was On the Origins of Species by Darwin published?

A

1859

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51
Q

What were Darwin’s 3 main findings?

A
  1. evolution = descent with modification
  2. All organisms have descended from one ancestor
  3. Organisms changed and adapted to specific environments which led to the diversity of life
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52
Q

What are Darwin’s 2 observations?

A
  1. Members in the population often have variable inherited traits
  2. All species can produce more offspring than the environment can support and many will not survive
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53
Q

What are Darwin’s 2 inferences?

A
  1. Individuals that have better fit traits will tend to have higher survivorship and more offspring
  2. unequal survivorship and reproduction rates will cause population to accumulate favourable traits
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54
Q

Define Neo-Darwinism/new Darwinism

A

The comprehensive theory of evolution including genetics

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55
Q

What happened in the 1930s in regards to genetic heredity?

A

Population geneticists started studying genetic variation and quantitative characters

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56
Q

Define macroevolution and give examples

A

Broad pattern of evolution above the species level

ie, sweeping changes in life on Earth above the species level

ex. mass extinctions, evolution of flight, evolution of seeds

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57
Q

What are 4 types of evidence for macroevolution?

A
  1. direct observation
  2. homology
  3. fossil record
  4. biogeography
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58
Q

Describe direct observation, give an example

A

Biologists have documented evolutionary changes in thousands of scientific studies

ex. beak length in soapberry bugs changed when the plant they fed on became rare and they started to feed on an invasive species

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59
Q

describe homology and give an example

A

similar characteristics as a result of common ancestry

ex. bones in forelimbs of mammals are homologous but modified for different modes of travel

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60
Q

define homologous structures

A

variations on a structural theme that was present in a common ancestor (anatomical or molecular)

61
Q

describe embryology and give an example

A

early stages of development in different animals show additional homologies

ex. the four chordate characteristics

62
Q

Describe vestigial structures and give an example

A

Remnants of homologous structures that served a function in the organism’s ancestors

ex. arrector pili muscles in humans - in other mammals the muscles cause fur to stand up as insulation or to make the animal seem larger when threatened

63
Q

describe molecular homologies

A

All life shares some genetic characteristics from a distant common ancestor

64
Q

What is an example of something that is found in all life forms?

A

nucleic acids

65
Q

T or F: humans share genes with other organisms including prokaryotes

A

true

66
Q

Will more closely related organisms have fewer or more homologies? why?

A

More, due to a more recent common ancestor

67
Q

Define convergent evolution, give an example

A

When natural selection causes the evolution of similar features in different lineages

ex. gliding in rodents in different parts of the world (sugar glider vs flying squirrel) - similar niches with similar selectional pressures

68
Q

Describe the fossil record

A

Shows evolutionary changes that have occurred and reveals common ancestors that are now extinct to help complete the tree of life

69
Q

What does the fossil record show when species appear and disappear?

A

Succession of life forms

70
Q

What were the first life forms?

A

Prokaryotes

71
Q

Define biogeography

A

The study of the distribution of species on Earth

72
Q

What is Pangea?

A

The single landmass that used to exist on earth and broke apart ~200 mya

73
Q

Define endemic species

A

Species that are found only in one place (often islands)

They are similar to the mainland species because they were colonized from the mainland but have adapted to their new environment and became a new species

74
Q

T or F: closely related endemic species tend to be in the same regions

A

True, example is marsupials in Australia

75
Q

T or F: natural selection works on individuals and therefore individuals can evolve

A

FALSE. Natural selections works on individuals, but individuals CANNOT evolve

76
Q

What is the smallest unit of evolution?

A

Population

77
Q

Define population

A

members of a species in the same geographic area at the same time that interbreed and produce viable offspring

78
Q

Evolution works on ___ characteristics which must be ____

A

heritable; variable

79
Q

T or F: changes in the environment can change which adaptations are selected for

A

True

80
Q

Initially, black peppered moths were rare and lighter coloured moths were more common because they were better camouflaged. When the industrial revolution blackened the trunks of trees, what happened to the moths?

A

The darker moths became more camouflaged against the blackened trees and so they became more common than the light coloured moths that now stood out and were more heavily predated by birds

81
Q

Define microevolution

A

Changes over time in the genetic composition of a population over many generations

82
Q

Define allele frequency

A

Proportion of the population that has the alternative version of a gene

83
Q

What are the 3 main causes of microevolution?

A
  1. natural selection
  2. genetic drift
  3. gene flow
84
Q

Which of the 3 main causes of microevolution reliably increases the frequency of favourable alleles?

A

natural selection

85
Q

Define genetic drift

A

a process where CHANCE events can cause changes in allele frequency

86
Q

Is genetic drift always adaptive?

A

No because the allele change may not be the best allele since genetic drift occurs randomly

87
Q

What size of a population does genetic drift have a larger impact on?

A

Small populations

88
Q

What are the two main types of genetic drift?

A
  1. bottleneck effect

2. founder effect

89
Q

Define bottleneck effect

A

1/2 types of genetic drift

Occurs when a random change (such as a natural disaster) wipes out most of the population and…

the surviving population has different genetic frequency than the original population after the event

90
Q

Define founder effect

A

1/2 types of genetic drift

Occurs when few individuals become isolated from a larger population (ex. when a few organisms are blown/float to a new island) and…

the new population will have a different genetic frequency than the original population

91
Q

Define gene flow

A

the transfer of alleles into or out of a population due to the movements of fertile individuals or their gametes (ex. pollen)

92
Q

What is an example of gene flow?

A

The spread of insecticide resistance in mosquitoes

  • the resistance alleles were a result of mutations
  • spread to other populations through gene flow
  • frequencies increased due to natural selection
93
Q

Is gene flow adaptive?

A

Not necessarily because the outcome can be random

94
Q

Define natural selection

A

the process in which individuals that have certain traits tend to survive and produce more offspring because of those traits

95
Q

Is natural selection adaptive?

A

yes, the outcome is not random

96
Q

How does natural selection affect allele frequencies?

A

It increases allele frequencies for traits that enhance survival and reproduction in the environment

97
Q

What three ways does natural selection alter the frequency distribution of traits?

A
  1. directional selection
  2. disruptive selection
  3. stabilizing selection
98
Q

Describe directional selection

A

1/3 ways natural selection alters frequency distribution of traits

Favours one extreme of phenotypes and
occurs when conditions favour individuals exhibiting an extreme value in the phenotype range

99
Q

Which way does the population frequency curve shift when directional selection occurs?

A

to the left or to the right (one of the extremes)

100
Q

When is directional selection common?

A

When the environment changes or members of a population migrate to a different habitat

101
Q

Describe disruptive selection

A

1/3 ways natural selection alters frequency distribution of traits

When conditions favour individuals at both extremes of the phenotype range but not those with intermediate phenotypes

102
Q

What is an example of disruptive selection?

A

birds with small beaks and birds with big beaks are favoured

Birds with moderately sized beaks are not as good at feeding on soft or hard seeds and are therefore less favoured

103
Q

Describe stabilizing selection

A

1/3 ways natural selection alters frequency distribution of traits

When conditions favour the intermediate phenotypes but not the extremes

Reduces variation

104
Q

Which of the 3 ways natural selection alters frequency distribution of traits reduces variation?

A

Stabilizing selection

105
Q

What is an example of stabilizing selection

A

Birth weights of most human babies is 3-4 kg, and those outside that range have higher rates of mortality

106
Q

Which way does the population frequency curve shift when disruptive selection occurs?

A

To both the left and right (the extremes)

107
Q

Which way does the population frequency curve shift when stabilizing selection occurs?

A

Shifts inward and upward (gets taller and narrower)

108
Q

How can genetic variation be measured?

A

As gene variability (% of heterozygous loci –> different alleles) or

nucleotide variability (% sequence differences)

109
Q

What are 3 causes of genetic variation?

A
  1. mutations (gene, chromosomes, or genome)
  2. recombination
  3. mostly, sexual reproduction
110
Q

How does sexual reproduction cause genetic variation?

A

It shuffles around existing alleles into new combinations

111
Q

Do most populations show considerable or minimal genetic variation?

A

considerable

112
Q

T or F: genetic variation has no effect on the health of a population

A

FALSE.

Populations need a certain amount of variation to be healthy

113
Q

Are there genetic variations that have neutral results/cause no selective advantages?

A

Yes

ex. fingerprints

114
Q

Define Darwinian fitness

A

The relative contribution of an individual to the gene pool of the next generation

115
Q

What is an example of Darwinian fitness?

A

Ghengis Khan’s lineage is very fit as 1/200 men alive today are his descendants

116
Q

Define relative fitness

A

chances of survival and fertility of a genotype

117
Q

Does selection act on genotypes or phenotypes?

A

Phenotypes

118
Q

What can differential reproductive success lead to?

A

change in populations

119
Q

Define the biological species concept

A

A group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring

120
Q

Define reproductive isolation

A

Existence of biological factors (barriers) that impede members of two different species from interbreeding and producing viable, fertile offspring

121
Q

What are two purposes of reproductive isolation?

A
  1. maintain integrity of closely related species

2. formation of new species hinges on this

122
Q

What are prezygotic barriers?

A

Ways to impede matings or prevent fertilization

123
Q

What are 5 prezygotic barriers?

A
  1. habitat isolation
  2. temporal isolation
  3. behavioural isolation
  4. mechanical isolation
  5. gametic isolation
124
Q

Describe habitat isolation

A

1/5 prezygotic barriers

Species in aquatic and terrestrial environments would not interbreed even if they’re in the same area

125
Q

Describe temporal isolation

A

1/5 prezygotic barriers

Species have different breeding times (ex. times of day, seasons, years)

126
Q

Describe behavioural isolation

A

1/5 prezygotic barriers

Species have different courtship rituals

127
Q

Describe mechanical isolation

A

1/5 prezygotic barriers

Species have morphological differences to prevent completion of mating

128
Q

Describe gametic isolation

A

1/5 prezygotic barriers

Sperm of one species may not survive the reproductive tract of female of another species
Or
biochemical mechanisms can prevent the sperm from fertilizing the egg

129
Q

What are postzygotic barriers?

A

If fertilization occurs, these are ways to maintain reproductive isolation

130
Q

What are 3 postzygotic barriers?

A
  1. reduced hybrid viability
  2. reduced hybrid fertility
  3. hybrid breakdown
131
Q

Describe reduced hybrid viability

A

Hybrids fail to develop or may not survive

132
Q

Describe reduced hybrid fertility (give an example)

A

hybrids are not fertile

ex. mules (cross between donkey and horse are sterile)

133
Q

Describe hybrid breakdown

A

First generation is fertile but later generations are not or are weak

134
Q

Define speciation

A

A process by which a group of individuals which can breed together splits into two or more groups that can no longer interbreed between them

OR

One species splits into two or more species

135
Q

When can speciation occur?

A

When a group is reproductively separated from parent species and the group changes enough to form a new species

136
Q

What 2 ways can speciation occur?

A
  1. allopatric speciation

2. sympatric speciation

137
Q

Describe allopatric speciation

A

When gene flow is interrupted because population has been geographically isolated into subpopulations

138
Q

What causes allopatric speciation?

A

A change in habitat

ex. a lake drying, river changing course, formation of canyons

139
Q

What are 4 reasons allopatric speciation cause an isolated subpopulation to become a new species?

A

The subpopulation will be genetically different from the parent population (FOUNDER EFFECT)

Genetic drift occurs and will have a profound effect cause the group will likely be small

different mutations can occur

natural selection may favour different traits in a new habitat

140
Q

Define sympatric speciation

A

Speciation that occurs in populations that live in the same geographic area

141
Q

Why is sympatric speciation less common than allopatric?

A

Because the species are still in the same geographic area so they can still interbreed

142
Q

What are 3 examples of sympatric speciation?

A
  1. polyploid speciation in plants
  2. habitat differentiation
  3. sexual selection (may be triggered by colour)
143
Q

How does habitat differentiation work as a form of sympatric speciation?

A

A subpopulation can exploit habitat or resources not used by the parent population

144
Q

Define adaptive radiation

A

evolution of many new species from a common ancestor

145
Q

How does adaptive radiation work?

A

New species can fill different ecological roles or niches

146
Q

What 3 reasons could adaptive radiation occur?

A
  1. After mass extinctions when there are many vacant niches
  2. when ancestors have evolutionary innovations such as seeds or armoured body coverings
  3. when new island chains form (volcanism)
    - ex. Hawaiian or Galapagos Islands
147
Q

What are 4 reasons why natural selection cannot fashion perfect organisms?

A
  1. selection can only act on existing variations and ideal variations may not exist
  2. evolution is limited by historical constraints because it adapts EXISTING structures to new situations
  3. chance, natural selection and the environment all interact causing a moving target for natural selection
  4. adaptations are often compromises
148
Q

How does the interaction between chance, natural selection and the environment effect evolution?

A
  1. chance can affect evolution:
    - natural disasters don’t necessarily only affect the worst or best adapted individuals
  2. environmental change can cause moving targets for natural selection –> one year one trait might be adaptive and the next year it’s not
149
Q

In what way are adaptations often compromises? Give an example

A

traits can be advantageous in one way but disadvantage in another

ex. adaptations for speed can lead to fragility of limbs

BIO 1210 (16 decks)

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