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BIOL300C- Evolution > Unit 2 > Flashcards

Unit 2 Flashcards

(71 cards)

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1
Q

Microevolution

A

small-scale changes within a population or species over a short time

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2
Q

Macroevolution

A

involves large-scale evolutionary changes that occur over long periods and lead to the formation of new species, genera, families, or even higher taxonomic groups.

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3
Q

T/F: microevolution and macroevolution are underlined by the same evolutionary forces

A

TRUE

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4
Q

Evolution

A

change in allele frequencies over time

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5
Q

What evolutionary process can change allele frequencies over time? In other words, what processes can drive evolution?

A
  1. Mutation
  2. Gene Flow
  3. Natural Selection
  4. Genetic Drift
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6
Q

Mutation

A

creation of new alleles (can be
beneficial, deleterious, or neutral)

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7
Q

Gene Flow

A

migration of individuals to or from a population

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8
Q

Natural Selection

A

a “filter” that increases the frequency of BENEFICIAL alleles

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9
Q

Genetic Drift

A

random changes in allele frequencies

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10
Q

What processes (only these processes) consistently increase adaptive traits (adaptation) in a population?

A
  1. Mutation
  2. Gene Flow
  3. Natural Selection
  4. Genetic Drift
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11
Q

Adaptation (definition 1)

A

the process by which a population becomes better able to survive and reproduce in its environment= ADAPTIVE EVOLUTION.

This is a process by which natural selection increases average fitness within a population.

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12
Q

Adaptation (definition 2)

A

a heritable trait that increases fitness of individuals within a population = ADAPTIVE TRAIT

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13
Q

What processes are not considered adaptation?

A
  1. Acclimation
  2. Acclimatization
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14
Q

Acclimation

A

short-term change in an individual (ex. more rapid breathing, heart rate at high altitudes)

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15
Q

Acclimatization

A

long-term change in an individual (ex. increased red blood cell counts at high altitudes)
** not genetics- they tend to be developmental plasticity

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16
Q

T/F: Adaptation occurs over generations and only within populations (not individuals)

A

TRUE

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17
Q

When you enter into a dark room, your eyes adjust to the darkness (pupils dilate to admit more light). This is an example of…

A

Acclimation
- doesn’t involve genetics
- dilation is a temporary change

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18
Q

Homoplasy indicates what kind of evolution?

A

Convergent Evolution

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19
Q

What are the three general principles of Mendel’s Model of Genetics

A
  1. alternative versions of genes account for variations in inherited characters= alles
  2. for each character, an organism inherits two alleles, one from each parent
  3. if two alleles at the locus differ then the dominant allele determines organism’s appearance while the recessive allele has no noticeable effect on appearance. ** not always the case
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20
Q

Mendel’s Law of Segregation

A

The two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes.

  • corresponds to the distribution of homologous chromosomes to different gametes in meiosis
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21
Q

Homozygous

A

two identical alleles

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22
Q

Heterozygous

A

two different alleles

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23
Q

Phenotype

A

Physical or outward appearance

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24
Q

Genotype

A

Organism’s genetic makeup (chromosomes)

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25
Synonymous
Changes that do NOT alter the amino acids within a protein. - Wobbly position** may or may not see a change in the amino acids
26
Non-synonymous
Changes that DO alter the amino acid sequence for proteins. ex. Glu -> Val (sickle cell anemia)
27
What are the three steps for proteins to be synthesized?
1. Transcription 2. Alternative Splicing (Introns spliced out) 3. Translation
28
What is meant by the phrase 'units of evolution'
Darwin's concept of 'Fitness'. Higher fitness = more offspring - populations evolve - organisms don't evolve
29
Selection acts on...
Phenotype - results in changes in the genotypes present in a population (i.e changes on allele frequencies) - bad alleles are removed from gene pool
30
The Blind Cave Tetra lives in lightless underwater caves and does not have eyes an adult. Based on DNA evidence, its closest relatives have eyes. Assuming that it costs energy to make eyes, the loss of eyes is likely an example of...
Evolution by natural selection. - Fish that don't have eyes don't expend energy that other's use on other processes ( which will lead to an increase in their fitness)
31
What is required for the Hardy-Weinberg Principle?
- no natural selection - no gene flow - no mutation - no genetic drift - mating is random
32
Based on the Hardy-Weinberg Principle, what equation is used to calculate genotype frequencies?
p^2 + 2pq +q^2 = 1 if A1=p and A2=q (A1 and A2 are allele frequencies)
33
The Hardy-Weinberg Equilibrium serves as a ________ for investigating evolution
Null Hypothesis - if the allele frequencies and genotype frequencies do not match then one of the 5 requirements may be occurring.
34
Sickle-cell anemia: what evolutionary process is likely in play? Expected frequency of Ss = 0.42 Observed frequency of Ss = 0.52
Heterozygote advantage - observing more heterozygotes than expected - evolution is promoting a carrier
35
How can you calculate what percentage of the population is a carrier?
aa = 1/20,000 = 0.00005 = q^2 q = sqrt(0.00005) = 0.007 p= 1-q = 1-0.007 = 0.993 Assuming Hardy-Weinberg frequency of heterozygotes (carriers) is: 2pq = 2(0.007)(0.993) = 0.014 SO frequency of carriers is 1.4%
36
Natural Selection is .....
Directed by Fitness
37
Absolute fitness
the number of offspring
38
Relative fitness
relative to the population mean (if frequency of two types = 1/2, then mean is 3)
39
If relative fitness is greater than 1:
then the allele increases in frequency
40
If relative fitness is smaller than 1:
then the allele decreases in frequency
41
If relative fitness is = 1:
the allele frequency will change randomly (no selection)
42
What are the three types of mutations based on fitness?
-beneficial/adaptive - detrimental/deleterious -neutral
43
Beneficial/Adaptive mutations occur when...
Relative fitness of a mutation of a new mutation is greater than 1, therefore the new allele (beneficial/adaptive) will be favored by selection
44
Detrimental/deleterious mutations occur when...
Relative fitness of a new mutation is less than 1, the allele (detrimental/deleterious) will be removed by selection
45
Neutral mutations occur when...
Relative fitness of the new mutation = 1, therefore the allele (neutral) will change in frequency randomly
46
Selection acts on the phenotype and therefore results in changes of...?
Genotypes present within a population (changes in allele frequency)
47
What are the four types of Natural Selection?
1. Directional Selection 2. Stabilizing Selection 3. Disruptive Selection 4. Balancing Selection
48
Directional Selection:
favors change in a single direction in phenotypes or allele frequencies
49
Stabilizing Selection:
Intermediate phenotypes
50
Disruptive Selection:
favors extremes
51
Balancing Selection:
favors more than one allele (multiple alleles) in a population at the SAME time
52
What three subsets are included in Balancing Selection?
1. Fluctuating selection 2. Heterozygote advantage 3. Rarity advantage
53
What phenotype is selected for in Directional Selection?
The average phenotype in a population changes in one direction. EX. Antibiotic Resistance Less resistant ---> More resistant - low resistance is selected against - high resistance is selected for
54
How does Directional Selection impact variation (genetic diversity)?
Reduces Variation (Genetic Diversity) - If a new mutation is disadvantageous, alleles are purged ---PURIFYING SELECTION--- - If a new mutation is beneficial, alleles increase in frequency ----POSITIVE SELECTION----
55
When favorable alleles MAY reach a frequency = 1, what is this called?
Fixation
56
When unfavorable alleles MAY reach a frequency = 0, what is this called?
Loss
57
Why does Fixation not always occur?
1. Directional selection is not always constant 2. Opposing directional selection may be operating EXAMPLE W/BIRDS -Large size favored to migrate - Small size favored for speed and agility
58
What is a natural experiment?
Experiments that allow researchers to compare treatment groups created by an unplanned change in conditions (ex. drought)
59
What average phenotype is selected for in Stabilizing Selection?
Intermediate phenotypes are selected for. Ex. Birthweight - Small size and large size babies have higher mortality than an optimal size (intermediate) baby Small size --> Optimal Size <-- Large Size
60
How does Stabilizing Selection impact variation (genetic diversity)?
Genetic diversity is reduced - However, no change in average trait value
61
In a population of tree frogs, females prefer larger males that have deeper calls. Large males have high reproductive success. Over time, average body size in the population increases. What type of selection has occurred and what has likely happened to genetic variation?
Directional Selection : genetic diversity has decreased
62
What type of phenotypes are selected for in Disruptive Selection?
Extremes are selected over average phenotypes ** opposite of stabilizing selection ** Ex. Seedcracker Birds - small beaked birds can eat small seeds efficiently - large beaked birds can eat large seeds efficiently - birds w/intermediate beaks have trouble eating both small and large. (leads to disadvantage)
63
Disruptive selection + positive assortative mating can cause...
Speciation - Gene flow is reduced between small and large billed forms - Two distinct populations may form - May eventually become two distinct species
64
How does disruptive selection impact variation (genetic diversity)?
Preserves genetic diversity
65
What is NOT true about Disruptive Selection?
The average phenotype becomes more common
66
What is the main concept of Balancing Selection?
No single allele has a distinct advantage. (A and a are both preserved)
67
T/F: Genetic variation is maintained in Balancing Selection?
TRUE
68
What is Fluctuating Selection?
Because sometimes the environment varies. Sometimes A is favored, sometimes a is favored.
69
What is Heterozygote Advantage?
Aa individuals have higher fitness than either AA or aa
70
What is Direct Rarity Advantage?
alleles are favored when rare- direct negative frequency-dependent selection
71

BIOL300C- Evolution (2 decks)

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