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Flashcards in Microevolution Deck (86):
1

Term that applies to evolutionary change within a lineage.It occurs continuously. Depending upon the organism and the circumstances, it can transform a lineage dramatically over time.

Microevolution

2

Alternately, a lineage may appear to remain the same over time-this is called

Stasis

3

Term that applies to the origin and extinction of lineages. It can happen gradually, or slowly.

Macroevolution

4

Which type of evolution do we understand better? Why?

Microevolution because it takes place on appropriate timescales that we can study directly

5

Did Darwin include a mechanism for the origin of species in his microevolution theory?

No.

6

Is the replacement of one species by another natural selection?

No. It is an ecological process with macroevolutionary implications

7

Is the genotype of an individual fixed at birth?

Yes

8

Then what is the smallest unit where evolutionary change is possible?

Do individuals evolve?

Populations

No

9

Populations permit the origin of new alleles through...

They permit change in the frequency of alleles through...

Mutation

Selection, Genetic Drift

10

refers to the study of evolution via the observation and modeling of allele frequencies and genetic change in populations of organisms.

Population Genetics

11

the proportion of a specific allele at a given locus, considering that the population may contain from one to many alleles at that locus.

Allele Frequency

12

The proportion of a specific genotype at a given locus, considering that many different genotypes may be possible

Genotype Frequency

13

The proportion of individuals in a population that exhibit a given phenotype

Phenotype Frequency

14

count the number of individuals with that phenotype, and then divide by the total. This gives you...

Phenotype Frequency

15

find the total number of individuals in the population with that genotype, and divide by the population size, N

Genotype Frequency

16

The formula for allele frequency for heterozygotes and homozygotes using alleles

p = (#AA) + 0.5*(Aa)/N
q= (#aa) + 0.5*(Aa)/N

17

The formula for allele frequency if you know the genotype frequencies

p=[f(AA)+0.5* f(Aa)]/N
q=[f(aa) + 0.5* f(Aa)]/N

18

Evolutionary Change is a Consequence of Changes in...

Is this macroevolutionary or microevolutionary change?

Allele Frequencies

Microevolutionary Change

19

All of the evolutionary change between our single-celled ancestors and ourselves can be described as the sequential origin of new alleles, their replacement of old ones, and occasionally the origin of new genes through duplication.

!!

20

defined as the situation in which no evolution is occurring. It is a genetic equilibrium.

Hardy-Weinberg Equilibrium

21

Was the notion that the dominance or recessiveness of an allele alone cause evolutionary change?

No.

22

Does Hardy Weinberg Equilibrium refer to one particular locus or multiple?

One lucus. It may be undergoing rapid allele-frequency change, while other loci are in equilibrium.

23

The five assumptions of hardy weinberg equilibrium

Infinite Population Size
No Allele Flow
No Mutation
Random Mating
No Selection

24

there are infinitely many individuals in the population

Infinite Population Size

25

no movement of individuals from population to population

No Allele Flow

26

no biochemical changes in DNA that produce new alleles

No Mutation

27

this means that with regard to the trait we're looking at, individuals mate at random they don't select mates based on this trait in any way

Random Mating

28

the different genotypes (for the genetic trait we're studying) have equal fitness

No Selection

29

Genotype frequency for AA
for Aa
for aa

p^2
2pq
q^2

30

One of five ways in which evolution occurs in which the five assumptions of HW are not met: A change in allele frequency by random chance. It occurs if a population is not infinite in size.

Genetic Drift

31

The effect of genetic drift is larger or smaller in small populations.

larger

32

In populations that are not infinitely large, there will be random error in which alleles are passed from generation, and allele frequencies will change at random.

!!

33

change in allele frequency that occurs because individuals move among populations

Allele Flow

34

biochemical change in DNA that one allele into another and creates alleles. It not a common event as a result, evolution through this is extremely slow.

Mutation

35

(typical mutation rates are about one mutation in a million genes passed from generation to generation );

!

36

Ultimately is the source of genetic variation

Mutation

37

Is fitness of mutations always good? Or is it random?

Do they result in higher or lower fitness more frequently?

Random

Lower

38

Note: the probability of a mutation occurring is independent of the need for one

!!

39

evolution that occurs because individuals select mates based on their characteristics.

Random Mating

40

evolution that occurs because different genotypes have different fitness. More about this later.

Natural Selection

41

Mutations may affect somatic tissue, also called

Mutations may affect the germ line, also called

Non-reproductive Tissue

Reproductive

42

In general, can somatic mutations be passed on?

No. Exception: Clonial Organisms

43

Mutations that can be passed to the next generation

Heritable Mutations

44

Whether a mutation is harmful, neutral, or favorable, depends upon

The environment

45

Type of mutation where one nucleotide is substituted for another, frequently this causes no change in the resulting organism, sometimes the change can be dramatic.

Substitution

46

Type of mutation where DNA is inserted into a gene, either one nucleotide or many. Sometimes, entire genes are inserted by viruses and transposable elements.

Insertion

47

Type of mutation where DNA bases are removed.

Deletion

48

Small insertions and deletions can inactivate large stretches of a gene, by causing this - which renders a gene meaningless

Frame Shift

49

Type of mutation where an entire gene is duplicated.

Duplication

50

Type of mutation where DNA is moved to a new place in the genome, frequently this happens because of errors in meiosis or transposable elements.

Transposition

51

their occurrence is independent of their selective value - i.e., they do not occur when they are needed any more often than they would otherwise.

Mutations are random events

52

Mutations at any single locus are rare events, mutation rates at a typical locus are about 1 in 10^6 gametes

!

53

Since each individual has thousands of alleles, the cumulative effect of mutations is considerable:
Consider that each gamete has 2x104 loci, and the mutation rates are about 1x10-6 per locus.

!

54

How many out of 50 of our gametes has a new mutation somewhere in its genome?

1 in 50

55

That means about 4% of us (we are diploid), more or less, have a new mutation somewhere in our genomes. Most of these new mutations are silent. YOU could be a mutant.

I can shoot lasers from my eye! Haha!

56

The only source of new alleles and hence the ultimate source of genetic variation is....

Mutation

57

What then acts on mutations?

Natural Selection

58

The allele that codes for a 32 base pair deletion that makes the protein non functional. People with this mutation lack the protein on the surface of their blood cells and homozygous individuals are essentially resistant to HIV

CCR-(delta)32

59

Did the CCR-32 mutation arise because of HIV?

No! It predates evolution by hundreds or thousands of years and was neutral

60

the change in allele frequencies that occurs by chance events. In essence, it is identical to the statistical phenomenon of sampling error on an evolutionary scale.
It is a random (stochastic) process.

Genetic Drift

61

Does the strength of genetic drift get larger or smaller as populations get smaller?

Larger

62

Does genetic drift generally result in adaptation?

No. There is little effect on large populations with one exception

63

What is the exception to genetic drift not resulting in adaptation?

It does effect populations over enormous spans of time

64

When the frequency of an allele reaches 1.0, what is the allele called? This can result in a population becoming homozgous at many loci

Fixed

65

genetic drift that occurs when a few individuals, representing a fraction of the original allele pool, invade a new area and establish a new population.

Founder Effect

66

The Amish and the California Cypress a large populations established from a small number of individuals and are therefore examples of

The Founder Effect

67

periods of very low population size or near extinction. This is another special case of genetic drift.

Bottlenecks

68

What happens to genetic variation when population ssize is allowed to go very low (when bottlenecks occur?)

Genetic variation is reduced

69

Cheetahs, Northern Elephant Seals, Ashkenazic Jews, and endangered species are all examples of population that were once in a

Bottleneck

70

by decreasing genetic diversity, it can put the population at risk of extinction
its random nature increases the genetic differentiation between two or more populations

Genetic Drift

71

What might occur when one or more populations become reproductively isolated by genetic drift

Speciation

72

This caused by genetic drift may change the genetic background against which new mutations act. If there is epistasis, a new mutation may be favorable in some populations and unfavorable in others.

Genetic Differentiation

73

postulates that the interplay between drift and selection are necessary for the origin of certain adaptations.

Wright's Shifting Balance Theory of evolution

74

It runs in parallel with Darwinian evolution by natural selection, though its effects are most noticeable and easiest to understand on loci for which there are no differences in fitness between alleles

The Neutral Theory of Molecular Evolution

75

One of the most interesting breakthroughs in evolutionary biology in the 1960’s-1990’s, has been the development of the neutral theory of molecular evolution.
It was introduced by the Japanese theoretician Motoo Kimura, in the late 1960’s.
It is a theory of evolution that Darwin never could have anticipated (evolutionary biology does not begin and end with Darwin).

The Neutral Theory of Molecular Evolution

76

It causes change over vast spans of time, at a more-or-less constant rate, when averaged over many loci.
For that reason, it can be used to develop a “molecular clock”..to tell how long it has been since two lineages have diverged.

The Neutral Theory of Molecular Evolution

77

In the 1960’s techniques of observing genetic variation in natural populations became available, and were pioneered by researchers such as Richard Lewontin.
It was discovered that, in natural populations, many selectively neutral genetic polymorphisms exist.
Kimura based his theory upon this.

The Neutral Theory of Molecular Evolution

78

He hypothesized that much of genetic variation is actually neutral

Motoo Kimura

79

He also asserted that most evolutionary change is the result of _______ acting on neutral alleles.

Genetic Drift

80

New alleles originate through the spontaneous mutatation of a single nucleotide within the sequence of a gene.
In single-celled organisms, or asexuals, this immediately contributes a new allele to the population, and this allele is subject to drift.

The Neutral Theory of Molecular Evolution

81

In sexually reproducing, multicellular organisms, the nucleotide substitution must arise within the germ line that gives rise to gametes.

The Neutral Theory of Molecular Evolution

82

Most new alleles are lost due to ______, but occasionally one becomes more common, and by random accident, replaces the original.
The chance of this is small, but over time, it happens occasionally, at a predictable rate.

Genetic Drift

83

n this way, neutral substitutions tend to accumulate, and genomes tend to evolve.
Many of the polymorphisms we see may be “transient”-one allele is in the process of replacing another.

The Neutral Theory of Molecular Evolution

84

Is the neutral theory well supported now?

Yes

85

Do rates of molecular evolution vary among proteins, and among organisms?

Yes. Some proteins allow much less neutral variation, and evolve more slowly.

86

Is population size important for rates of molecular evolution?

Why?

No.

It cancels out in the math, small populations drift faster, but have fewer mutants per generation