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Evolution Flashcards

1
Q

What is evolution?

A

Change in properties of groups of organisms over the course of generations

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2
Q

Who developed the theory of evolution by natural selection?

A

Darwin and Wallace, but there are key differences in their ideas

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3
Q

What held back the acceptance of evolution by natural selection?

A

A lack of understanding the mechanism of inheritance

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4
Q

What brought together the understanding of inheritance?

A

The Modern Synthesis

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5
Q

What is a synonymous mutation?

A

Amino acid does not change

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6
Q

What is a nonsynonymous mutation?

A

Amino acid changes

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7
Q

What determines mutation rates?

A

Efficiency of DNA repair mechanisms

Exposure to mutagens

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8
Q

What is gene pool?

A

Sum of all copies of all alleles within a population

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9
Q

What causes selection?

A

Occurs when there is a difference in the survival and/or reproduction of individuals based on their phenotype

Selection increases the frequency of the favoured trait in the next generation

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10
Q

What is an individual’s fitness?

A

Their survival and reproduction

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11
Q

What is natural selection?

A

When the difference in fitness occurs due to conditions in the biotic or abiotic environment

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12
Q

What is artificial selection?

A

When the difference in fitness occurs due to human preference for traits (i.e. selective breeding)

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13
Q

What is sexual selection?

A

When individuals mate preferentially with particular individuals and rather than at random

It has the power to favour traits that enhance chances of reproduction, even if those traits reduce chances of survival

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14
Q

What is migration?

A

Movement of individuals or gametes

If migrants survive and reproduce gene flow occurs which changes Allele frequencies

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15
Q

What is genetic drift?

A

Random changes in Allele frequencies from one generation to the next. Driven by chance, not selection.

Has larger impacts in smaller populations

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16
Q

What is population bottleneck?

A

When a population is dramatically reduced in size, by chance the small number of survivors may not be representative of the original population.

  1. Original population has approx equal frequencies
  2. Chance environmental event greatly reduces population size
  3. Allele frequencies in the surviving population differ from those of the original population
  4. Population grows following the bottleneck event, its Allele frequencies reflect the surviving population
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17
Q

What are some mechanisms in unstable populations?

A

Population bottleneck

Founder effect

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18
Q

What is the founder effect?

A

When a population is started by a small number of individuals, they are unlikely to possess all the Allele found in the gene pool of the source population

Founder populations will be less variable than the original

Rare alleles likely to be lost

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19
Q

How can a population’s genetic structure be described as?

A

By the frequencies of the alleles and genotypes in it

Biologists develop an estimate based on a reasonably sized sample

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20
Q

What is the frequency of an Allele equal to?

A

= the number of copies of the Allele in the population ÷ total number of copies of all alleles in the population

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21
Q

What is the Hardy-Weinberg principle?

A

p² + 2pq + q² = 1

In order for the principle to apply the population must be in equilibrium, not evolving

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22
Q

What happens in a population of Hardy-Weinberg equilibrium?

A

All individuals have equal probabilities of surviving and reproducing

The population is infinitely large

Genes are not added to or removed from the population by migration

DNA sequence does not change

Mating is random

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23
Q

What does Hardy-Weinberg equilibrium describe?

A

The theoretical conditions required for evolution to not occur

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24
Q

What is the Chi square test?

A

Evaluates statistically significant differences between two or more groups in a data set

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25
What are the 3 conditions of selection?
Variation in a trait Heritability of a trait Differential fitness conferred by a trait
26
What are qualitative traits?
Those that have discrete qualities, often controlled by alleles at a single locus
27
What are quantitative traits?
Show continuous variation Can be influenced by genes at many locus as well as the environment
28
What type of trait does natural selection act on, and how does it do this?
Acts on quantitative variation 1. Directional selection/positive selection- favours one extreme value 2. Stabilising selection/balancing selection- favours average values 3. Disruptive selection/diversifying selection- favours both extreme values
29
What is intra sexual selectio?
Competition between members of the same sex
30
What is inter sexual selection?
Mate choice
31
What is pre-copulatory?
Acquiring mating opportunities
32
What is post-copulatory?
Events that occur during and after mating
33
What is the direct benefit of sexually selected traits?
Can give honest signals of parenting quality
34
What are the indirect benefits of sexually selected traits?
Good genes- genes that enable males to develop impressive ornaments or fighting ability may indicate overall genetic quality Sexy sons (runaway selection)- females express a preference for a male trait, no direct benefit to use, Sons express the trait that mothers preferred, increasing the sons reproductive success. Male trait and it's female preference must be heritable
35
What are evolutionary constraints?
Development of many potentially favourable traits is prevented by a lack of genetic variation that would produce the trait -because the Allele does not exist in the population -because mutation has not given rise to an Allele that would produce the phenotype
36
What do trade offs do to evolution and what are the different types?
They limit evolution Types: Allocation constraints Functional constraints Shared biochemical pathways Ecological circumstances Sexual Vs natural selection
37
What is micro evolution?
Changes in Allele frequencies within populations
38
What is macroevolution?
Over time micro evolution builds up and leads to macro evolution
39
What are the patterns in macro evolution?
Stasis- some lineages don't change much in outwards appearance for long periods of time Rates of character changes- lineages can change quickly or slowly Lineage splitting and speciation- key evolutionary innovations can lead to rapid diversification Extinction- can be due to bad genes, a species dies out because of some aspect of natural selection OR bad luck, during mass extinctions environmental stresses are severe.
40
What is Bergmann's rule?
Within a species of closely related taxa, individuals in colder climates tend to be larger than those in warmer climates
41
Why are larger endotherms more common in colder regions?
Heat conservation Heat mortality Resource availability Starvation resistance
42
What is negative frequency dependent selection?
The less common a phenotype is the higher it's fitness
43
What is positive frequency dependent selection?
More common a phenotype is, the higher it's fitness
44
How is variation maintained within populations?
Frequency dependent selection. Heterozygote advantage
45
What is heterozygote advantage?
When different alleles are favoured under different environmental conditions heterozygous individuals may outperform homozygotes
46
What are the models of gene flow?
Continental island model: -One way gene flow from a large continental mainland population to a smaller island population -Allele frequency on the island depends on the rate of gene flow and the difference in Allele frequency between the island and the mainland Island model: -Describes gene flow among many populations exchanging immigrants with one another Stepping stone model: -allow subpopulations to exchange individuals only with adjacent subpopulations in one or two or more dimensions -two subpopulations that are far apart will expedimve little gene flow and will be more different than two subpopulations closer together -probability of mating decreases with distance
47
Where is geographic variation most likely to develop among populations?
When populations are discrete, however can also occur in continuous populations
48
How can variation among populations be driven?
Genetic drift Adaptation
49
What is phylogeny?
A diagram that depicts the lines of evolutionary descent of different lineages
50
What is a taxon?
Group of individuals that are related at any scale
51
What is a clade?
A taxon that consists of all evolutionary descendants of a common ancestor
52
What is a sister species?
Two species that are each others closest relatives
53
What are sister clades?
Two clades that are each others closest relatives
54
What are ancestral traits?
Characters inherited from the common ancestor of a group
55
What are derived traits?
Characters that are unique to specific sub groups
56
What are homologous traits?
A feature shared by taxa that are descended from a common ancestor
57
What is synapomorphy?
Derived traits shared across all members of a group Evidence of common ancestry
58
What is autapomorphy?
A derived trait that is unique and defines that taxon
59
What is homoplasies?
Traits that are superficially similar but do not arise from shared ancestry A trait that appears homologous may actually be homoplastic
60
How can homoplasies arise?
Convergent evolution- independently evolved features subjected to similar selective pressures become superficially similar Evolutionary reversal- a character reverts from a derived state back to an ancestral one
61
How to construct a phylogeny?
Choose the terminal taxa Make observations of the characters Reconstruct all possible trees Evaluate support for the tree
62
Sequence Vs morphology?
Sequence provides more characters Morphological convergence is common Morphological data can be collected from long extinct species using fossils
63
How do we know which tree reflects the data set best?
Using the principle of parsimony/Occasm's razor When there are competing theories and explanations, the simpler one is more likely to be true For a phylogeny, the tree that requires the fewest character changes is more likely to be correct

Genetics And Evolution (10 decks)

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