Ecology and Evolution > Lecture 2: Evolution > Flashcards

Lecture 2: Evolution Flashcards

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1
Q

What is evolution?

A

Evolution is the theory that species
change over time

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2
Q

Do individuals evolve or do populations evolve?

A

evolution is how populations
(not an individual) change over successive
generations

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3
Q

Is evolution constant?

A

This is a constant process, species are
always in the process of changing

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4
Q

What is a population?

A

A group of interbreeding individuals of the same species (in the same place)

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5
Q

What is microevolution?

A

Change in allele frequencies
(little changes)
ex: peppered moth

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6
Q

What is macroevolution?

A

Large changes, usually creates a
new species or group
ex: Lions and Tigers

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7
Q

How do we know evolution is
occurring?

A
  • Life occurred one time and then
    we speciated into all living things
    found today
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8
Q

What is the evidence for evolution?

A
  • Fossil record
  • Comparative Anatomy
  • Molecular Evidence
  • Direct observation
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9
Q

How does evolution occur?

A

mechanism of evolution: a biological process that
causes changes in allele frequencies (gene variants)
within a population across generations.

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10
Q

What are the mechanisms of evolution?

A
  • Natural Selection
  • Sexual Selection
  • Genetic Drift
  • Mutation
  • Gene Flow (Immigration/Emigration)
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11
Q

What were Darwin’s observations?

A
  • Darwin observed:
  • Individuals in a species are not all the same: Variability
  • Offspring tend to resemble their parents: Heredity
  • Some traits are advantageous, with only most fit surviving:
    Fitness Consequences (survival of the fittest)
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12
Q

What is Fitness?

A
  • Fitness is the reproductive contribution of a phenotype to
    subsequent generations. (It is a discrete and measurable quantity)
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13
Q

When does fitness increase?

A

it increases if an individual has increased
* Survivability (the longer you live, the more likely you are to
have babies)
* Reproductive success (the higher your reproductive success,
the more babies you will have)

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14
Q

Define Natural selection

A

Natural selection is the process by
which individuals with traits that enhance
survival and reproduction pass those traits on,
leading to gradual changes in populations over
generations

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15
Q

What are the key components of natural selection?

A
  • Variation (mutations and sexual reproduction)
  • Heritability
  • Differential survival and reproduction
    (favourable phenotypes)
  • Evolution over generations
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16
Q

Why does natural selection occur?

A
  • Individuals in a population are not equal in their ability to survive and
    produce viable, fertile offspring
  • Populations adapt to their environment by accumulating and maintaining
    favourable genotypes
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17
Q

What is relative fitness?

A

Contribution an individual makes to
the gene pool of the next generation
relative to contribution of others
ex: Snake jaw that allows them to swallow larger prey

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18
Q

How do environmental conditions affect natural selection?

A

results in different alleles being
favoured (acts as an evolutionary pressure)

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19
Q

What type of individuals leave more offspring?

A

individuals with inherited traits that give them a
better chance of surviving and reproducing in a given
environment

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20
Q

What happens if certain individuals have an unequal ability to survive and reproduce?

A

leads to accumulation of favourable traits in a
population over time in a given environment.

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21
Q

What happens to unfavourable traits in a population?

A

The rate of unfavourable traits will decrease over time in a particular environment.

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22
Q

What will influence which traits are favoured?

A

Which traits are favoured depends on
context (depends on environmental
conditions – selective pressure)

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23
Q

What are the steps to evolution by natural selection?

A
  1. Overproduction: more offspring is produced than can possibly survive
  2. Variation: inherited traits vary in a population
  3. Selection: one individual is more likely to survive and reproduce than
    another due to different traits (selective pressure must be present)
  4. Adaptation: over time, traits that improve survival and reproduction will
    become more common
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24
Q

What factors drive natural selection?

A
  • Competition for resources such as food and shelter
  • Competition for mates
  • Differential reproductive success (how good you are at making babies)
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25
What would happen if all individuals in a population had equal reproductive success? (i.e. produced the same # of offspring)
Evolution would never occur because there would be no evolutionary pressure
26
What is artificial selection?
Selective breeding of domesticated plants and animals (natural selection forced by humans thus not natural anymore)
27
How do we study evolution?
* Homology * Anatomical * Developmental * Molecular * Convergent evolution * Fossil record * Biogeography
28
What is homology?
traits inherited by two different organisms from a common ancestor
29
What is Analogy?
similarity due to convergent evolution, not common ancestry
30
What is divergent evolution?
- a population becomes separated from the rest of the species (common ancestry) - Different selective pressures cause different patterns of evolution
31
Which type of evolution are homologous structures associated with?
Divergent evolution (common ancestry)
32
What is convergent evolution?
Convergent evolution: - Organisms evolve to resemble each other because they occupy similar environments, have similar selective pressures. - Constructed from different structures, evolved independently
33
Which type of evolution are analogous structures associated with?
Convergent evolution
34
Are convergent and divergent evolution examples of micro or macro evolution?
Macroevolution
35
What is evidence for homology?
* Forelimbs of all mammals show same bone arrangement even though appendages have different functions * Unlikely if structures had arisen anew in each species
36
What are anatomical homologies in early stages of development?
similarities in the body structures of embryos from different species, seen during their early development - ex: All vertebrate embryos have post- anal tail and pharyngeal arches
37
What are vestigial structures?
* Remnants of features that served a function in the organism’s ancestors ex: * Snakes with vestiges of pelvis and leg bones * Eye remnants buried under scales in blind species of cave fishes * human tailbone
38
What are molecular homologies?
* All life uses the same genetic code * Humans and bacteria share genes inherited from very distant common ancestor
39
Are codons the same for all living things?
yes
40
What are pseudogenes?
* Genes that have lost their function, even though homologous genes in related species may still be functional
41
Why does convergent evolution happen?
Because two species have the same evolutionary pressure ex: sugar glider and flying squirrel
42
Is resemblance analogous or homologous?
Analgous
43
Are the wings of bats, birds and insects convergent or divergent evolution?
Convergent evolution: all their wings are analogous structures that evolved independently (all realized wings were useful separately)
44
What is biogeography?
Study of geographic distribution of species
45
Why are the animals in Australia so different?
Australia broke off from the rest of the world ~30 million years ago – a long time before the rest of the continents.
46
Define what a species is?
individuals who have the potential to interbreed and produce viable, fertile offspring
47
What is a gene pool?
all the genes in a population (all the alleles in a population)
48
Is a mule a species?
No because they are infertile
49
What is allele frequency?
the frequency a specific allele is found in the population
50
If I have a population with 75% AA individuals and 25% Aa individuals, which alleles are present in the gene pool?
A and a
51
What is the Hardy-Weinberg equilibrium?
The Hardy-Weinberg equilibrium is a theory that states a population’s allele frequency is inherently stable – unless some kind of evolutionary force is acting upon the population
52
What does the Hardy-Weinberg principle assume?
* 2 alleles * Simple dominant and recessive * No mutations, * No migration * No selective pressure for or against genotype (no natural selection) * Random mating (no sexual preference) * Very large population
53
Under the conditions of the HW equilibrium should allele frequencies of a population change over time?
NO
54
What is the smallest unit of evolution?
microevolution
55
What are the Main mechanisms that can cause allele frequency changes?
1. Natural selection 2. Sexual Selection 3. Genetic drift (chance events that alter allele frequencies) 4.Gene flow (transfer of alleles between populations) 5. Mutations
56
What are the sources of genetic variation?
* Formation of new alleles * Mutation * Altering gene number or position * Rapid reproduction * Sexual reproduction
57
Why is genetic variation important?
In order to change allele frequency over generations, you need to have different alleles in a populaiton (genetic variation).
58
How can we tell whether a population is evolving?
Determine what the allele frequency of a population would be if it were not evolving and compare it to the actual allele frequency in the population. * No difference = not evolving * Difference = an evolving population
59
What does p represent in HW?
A (dominant allele)
60
What does q represent in HW
a (recessive allele)
61
What does p^2 represent is HW?
AA
62
What does q^2 represent in HW?
aa
63
What does 2pq represent in HW?
Aa
64
What happens if a population meets all HW assumptions?
it’s in H-W equilibrium and NOT evolving.
65
What is HW equation used for?
* Test if evolution is occurring in a population * Estimate % of a population carrying an allele for a genetic disease
66
How are gene frequencies altered?
* New mutations can alter gene frequencies (Mutations rare) * Non-random mating can affect frequencies of homozygous and heterozygous frequencies
67
Which 3 mechanisms alter gene frequencies directly and cause the most change?
1. Natural selection 2. Genetic drift 3. Gene flow
68
Which type of mutation persists in a population?
Mutations that occur within sex cells
69
Which individuals produce more offspring?
Those better suited to their environment
70
What is sexual selection?
* Individuals with certain inherited characteristics are more likely than others to mate ex: male peacocks
71
What can sexual selection cause?
sexual dimorphism * Difference in appearance between males and females of the same species
72
What is intrasexual selection?
Individuals of one sex compete directly for mates of the opposite sex ex: male deer
73
What is Intersexual selection?
Individuals of one sex (often females) are choosy in selecting mates ex: female peacocks
74
What is genetic drift?
Genetic drift is when chance events cause allele frequencies to fluctuate unpredictably from one generation to the next *Think about coin flip example: The lower the number of coin flips, the farther away from 50/50 heads vs tails you would expect.
75
Is the effect of genetic drift stronger in large or small populations?
Effect is stronger in small populations
76
What are the founder effect and bottleneck effect examples of?
Genetic drift
77
Explain the founder effect?
A small group of individuals, not representative of the overall population, colonize a new habitat
78
Explain the bottleneck effect?
A disaster kills victims randomly causing the genetic makeup (allele frequencies) of the new population to not be representative of the original population *natural disaster is the bottleneck to the flow of alleles
79
Can human actions cause genetic drift?
Human actions can create bottlenecks for other species
80
What are the main effects of genetic drift?
* Significant in small populations * Can cause allele frequencies to change at random * Can lead to loss of genetic variation within populations * Can cause harmful alleles to become fixed
81
What is gene flow?
Transfer of alleles into or out of population * Individuals or their gametes may enter or leave a population ex: insects carrying pollen from one pop to another
82
How could gene flow affect two distinct populations?
Can reduce genetic differences between populations and result in two populations becoming one
83
What is a species?
Group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
84
What is speciation?
Formation of new species
85
What causes speciation?
Formation of new species hinges on reproductive isolation
86
What factors contribute to speciation?
* Prezygotic barriers block fertilization * Postzygotic barriers contribute to reproductive isolation after hybrid zygote is formed
87
What is Habitat isolation and what type of barrier is it?
species living in different habitats (pre zygotic)
88
What is Temporal isolation and what type of barrier is it?
2 species breed at different times of the day, season or year (pre zygotic)
89
What is Behavioural isolation and what type of barrier is it?
Species have specific signals and behaviour to attract mates (pre zygotic)
90
What is mechanical isolation and what type of barrier is it?
Morphological differences (parts don't fit together) prevent mating (pre zygotic)
91
What is Gametic isolation and what type of barrier is it?
Sperm not able to fertilize egg of different species * Sperm can’t penetrate egg’s membrane * Sperm can’t survive in female’s reproductive tract (pre zygotic)
92
What is Reduced hybrid viability and what type of barrier is it?
- Hybrids don’t complete development or are frail (post zygotic)
93
What is Reduced hybrid fertility and what type of barrier is it?
- Hybrid is sterile (post zygotic)
94
What is Hybrid breakdown and what type of barrier is it?
* 1st generation hybrids are viable and fertile * Hybrid mating with other hybrids or either parent species results in frail or sterile 2nd generation (post zygotic)
95
What are the modes of speciation?
(1) Allopatric speciation * Geographic isolation (2) Sympatric speciation * No geographic isolation
96
How do we know whether something is a barrier regarding allopatric speciation?
Depends of the organisms abilities ex: a canyon isn't a barrier to birds but it is for mice
97
How does sympatric speciation occur?
* Polyploidy * Sexual selection * Habitat differentiation
98
Is sympatic or allopatric speciation more common?
Allopatric
99
What is polyploidy?
* Accident during cell division results in extra sets of chromosomes * More common in plants than animals
Ecology and Evolution
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