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From Organisms to Ecosystems - Lectures > Lecture 10. Natural Selection and Evolutionary Processes > Flashcards

Lecture 10. Natural Selection and Evolutionary Processes Flashcards

1
Q

When is natural selection inevitable ?

A
  1. Replication
  2. Variation between individuals
  3. Heritability of traits
  4. Differential survival
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2
Q

What is differential survival ?

A

Only the individuals who do best in the environment, grow up and successfully breed

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3
Q

What conclusion can we draw about individuals who inherit traits which fit them well for their current environment ?

A

They are more likely to breed and pass on those good traits to their offspring

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4
Q

What does the frequency of the increase in good traits and reduction of bad traits result in ?

A

The population slowly changing to be better adapted to its environment

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5
Q

What is the evolution of the population ?

A

The inevitable outcome of replication, variation between individuals causing differential survival and heritability of the locally beneficial traits

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6
Q

What was Darwin’s problem of variation and inheritance ?

A

He did not know how traits passed from parents to offspring and he thought the traits of the parents blended in the offspring which gets rid of variation very fast. He also knew that variation is maintained much longer than blending would allow.

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7
Q

What theory did Darwin propose for his problem of variation and inheritance which turned out to be incorrect ?

A

Pangenesis

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8
Q

What is pangenesis ?

A

This theory says that variation acquired during the animals lifetime are transmitted to the germ cells by gemmules returning variation to the system.

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9
Q

What did Gregor Mendel do ?

A

Carried out breeding experiments with peas, and quantitative analysis of the resulting forms to infer how inheritance worked

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10
Q

What did Mendel’s genetic show us ?

A
  1. Inheritance through alleles of genes is particulate not blended. This maintains variation despite variation.
  2. Acquired characteristics are not inherited, so play no part in evolutionary change
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11
Q

What did Mendel’s genetics tell us about natural selection ?

A

Natural selection is the change in frequency of stable variants

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12
Q

Which scientists integrated all our evolutionary understanding into “The modern synthesis” ?

A

Ernst Mayer, George Ledyard Stebbins, Theodosius Dobzhansky

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13
Q

What does the “Modern Synthesis” reconcile ?

A
  1. Natural selection
  2. Mendelian genetics
  3. Population genetics
  4. Macroevolution
  5. Microevolution
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14
Q

What is macroevolution ?

A

Species level patterns in survival and extinction

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15
Q

What is microevolution ?

A

Individual level changes in populations of organisms

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16
Q

What does “The Modern Synthesis” theory agree with ?

A

That natural selection, working on heritable variation, supplied by mutation, brings about evolution

17
Q

What does natural selection remove ?

A

Variance

18
Q

What is punctuated equilibrium ?

A

New species are formed by leaps where whole organism changes occur

19
Q

What do evolutionary scientists say how does evolution progress on the geological timescale ?

A

Punctuated gradualism

20
Q

What is punctuated gradualism ?

A

Bouts of faster change when selection pressure are high, and variation is present. Slower or no change when less selection pressure or mutations are needed

21
Q

What did Sheldon 1987 show ?

A

Evolution is gradual, but it varied in both rate and direction

22
Q

What are the three types of selection over geological timescales ?

A
  1. Directional selection
  2. Stabilising selection
  3. Disruptive selection
23
Q

What is directional selection ?

A

One extreme of the population is the fittest

24
Q

What is stabilising selection ?

A

The mean of the population is the fittest

25
Q

What is disruptive selection ?

A

If both extremes are fitter, than the mean or the middle is disadvantageous

26
Q

What causes fitness ?

A

Variation between individuals

27
Q

What is inclusive fitness ?

A

The effects of an individual on gene propagation

28
Q

What are the two types of inclusive fitness ?

A
  1. Directly

2. Indirectly

29
Q

What is direct inclusive fitness ?

A

In the bodies of surviving offspring who themselves are fertile

30
Q

What is indirect inclusive fitness ?

A

Via non descendent kin. Also a function of how closely related those non-descendent kin are to you.

31
Q

What is the problem with measuring fitness ?

A

It is almost impossible

32
Q

When fitness is measured what are you actually measuring ?

A

Partial fitness

33
Q

What is partial fitness ?

A

Incomplete measures of fitness

34
Q

Why are comparisons of partial fitness useful ?

A

They indicate which individual in fitter and will leave more copies of its genes

35
Q

How do organisms act to maximise their fitness ?

A
  1. By looking after their own interests
  2. By fighting for mating opportunities
  3. By having as many offspring as possible
  4. By competing for food to feed them
  5. By defending them even at a danger to themselves
  6. By helping their relatives but not their rivals
36
Q

What are two important perspectives when thinking about evolution ?

A
  1. It is not about the individual trying to survive or breed, its a race between different alleles of the same gene.
  2. Animals are in competition with other of their species
37
Q

What is a population of animals ?

A

A collection of individuals with genes that passed on copies

38
Q

What are four concepts widely misunderstood ?

A
  1. Natural selection only selects within the available variation in the population
  2. Natural selection cannot plan ahead, it only responds to current conditions
  3. Natural selection is between individuals, but evolution happens to populations.
  4. There is no intent, direction or purpose to evolution, it just happens

From Organisms to Ecosystems - Lectures (37 decks)

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