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GENETICS > Midterm 2- Evolution > Flashcards

Midterm 2- Evolution Flashcards

1
Q

Evolution

Definition

A

A change in heridable characteristics of a population over generations

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2
Q

Microevolution

Definition

A

Changes in allele frequencies in a population over a short period of time

ex. over one generation

Our primary focus in class

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3
Q

Macroevolution

Definition

A

Changes in allele frequencies that occur at or above the species level

ex. thousands/millions of years

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4
Q

4 hints that we are all descendant from a common ancestor

A
  1. We are all made up of cells
  2. Use DNA as the genetic code
  3. Flow of biological information
  4. Same system of DNA repair/replication
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5
Q

Homologies

Definition

A

Traits present in two or more organisms that were inherited from their common ancestor

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6
Q

Structural/anatomical homologies

Definition

A

Physical traits

ex. Forelimb bones in turtles/whales/humans

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7
Q

Developmental homologies

Definition

A

Similarities during the embryonic stage

ex. we have gills and a tail in embryo

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8
Q

Genetic homologies

Definition

A

Genetic similarities between organisms due to shared ancestory

ex. humans/chimpanzees share 99%

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9
Q

Convergent evolution

Definition

A

Analogous traits: Similar features that evolved independantly due to shared environmental demand

ex. sharks and whales dorsal fins

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10
Q

4 evidence of evolution

A
  1. Vestigual traits
  2. Transitional features
  3. Extinctions
  4. Evolution in real time

TEEV

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11
Q

Vestigual structure

Definition

A

Lost ancestoral function and now has no or reduced functions

ex. hip bones in whales

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12
Q

What is the HWE?

A

P^2 + 2pq + q^2 = 1

P = HOMO DOM, Q = HOMO RECCESS, PQ = HETERO

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13
Q

What does the HWE calculate?

A

The EXPECTED genotype frequency, if evolution is not acting on a population

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14
Q

What assumptions are made with HWE?

A

NO natural selection, sexual selection, population is infinitely large (genetic drift), no gene flow, no mutations

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15
Q

What is the cutoff point for HWE?

A

0.1, if difference is > 0.1 then evolution is acting on that gene

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16
Q

Organism of the day:

Trilobites

A

Extinct marine invertebrates, first to develop complex eyes , roll into a ball when threatened, likely scavengers

Existed for 300 million years

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17
Q

Organism of the day:

Barnacles

A

Have the largest penis size of any animal, glued to rock so cannot move to find mate

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18
Q

Natural selection

Definition

A

A process where certain phenotypes/genotypes are more likely than others to survive and reproduce, therefore pass alleles onto next generation

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19
Q

What is the outcome of natural selection?

A

Increase in frequency of beneficial alleles, population becomes more well adapted to environment as long as it doesnt change

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20
Q

Name the 3 criterea for natural selection

A
  1. Must be variation amongst individuals phenotype
  2. Variation must be hereditable (have a genetic basis)
  3. Variation must be associated with differences in fitness

VHF

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21
Q

Definition

Fitness

A

Measure of individuals reproductive success

NOT only survival

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22
Q

Name the 3 modes of natural selection

A
  1. Directional 2. Stabilizing 3. Disruptive
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23
Q

Directional natural selection

Definition

A

Shift in one direction from parental generation favouring an extreme

Phenotypic variation is reduced

ex. Finches with smaller beaks favoured smaller seeds

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24
Q

Stabilizing natural selection

Definition

A

Selects against extremes at both ends of distribution, favours the intermediate

Phenotypic variation is reduced

ex. number of robin eggs layed

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25
Q

Disruptive natural selection

Definition

A

Both end extremes are favoured, intermediate has the lowest fitness

Variation is increased

ex. Chinook salmon two strategies

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26
Q

Adaptations

Definition

A

A population becomes more well adapted to the environment as a result of natural selection OR a heritable trait that enhances survival or reproduction of the organism

27
Q

What are the 3 requirements of adaptations?

A
  1. Heritable
  2. Functional
  3. Positive effect on fitness

FHF

28
Q

What differentiates adaptations from natural selection?

A

Has to have a FUNCTION (not variation)

29
Q

Organism of the day

Rubber Boa

A

Only boa native to Canada, skelaton is enlarged at the tail tip threatened curls into a ball and raises tail to look like head

30
Q

Adaptation in Pistol shrimp?

A

Enlarged left claw for snapping that can superheat water around them to temperatures near the surface of the sun to stun predator/preys

31
Q

What is Darwins theory of Sexual Selection?

A

Natural selection cant explain certain traits such as courtship/sexual dimorphism/lethal male combat/male ornamentation

CAN be explained if increases chances of attracting a mate

32
Q

Sexual dimorphism

Definition

A

Differences in the appearances of males and females

33
Q

Intrasexual selection

A

Competition between two individuals of the same sex for mates

ex. Deer antlers

Often male to male

34
Q

Intersexual selection

Definition

A

Interactions between the sexes- elaborate behavioral displays

35
Q

Why are females more choosy than males with respect to chosing a mate?

A
  • Asymmetry in gametes (cheap sperm/costly eggs)
  • Donation of resources - - Males can mate more times than females
36
Q

What are the two hypotheses of Intersexual selection

A
  1. Better provider of direct resources to female and offspring ex. Food, protection, parental care (nuptual gifts)
  2. Better provider of indirect resources ex. have good genes, health, DNA, immune system, no parasites (long tail on peacocks)

Mate choice (females)

37
Q

What are the 3 requirements for evolution by sexual selection

A
  1. Variation
  2. Hereitable
  3. Fitness difference associated with differences in mating oppurtunities/quality of offspring
38
Q

Organism of the day

Pacific Spiny Lumpsucker

A

Poor swimmers, modified pelvic fins attach to rocks to combat water movement, males glow bright red to attract females (intersexual)

39
Q

Genetic Drift

Definition

A

Changes in allele frequencies in a population over time due to random differences in survival or reproduction

Evolution at random (not better genes)

Results in a reduction of variation

40
Q

What populations does genetic drift occur in?

A

ALL populations that are not infinite in size, but does have a stronger affect on SMALLER populations

Similar to sampling error (sample doesnt represent the population)

41
Q

Two oppurtunities for Genetic drift occur in?

A

1. Population bottle neck event: Often due to catastrophe, pop size drastically reduces
2. Founder event: New pop is started by members of original pop

Both reduce variation, Founder event can increase rare alleles in new po

42
Q

What are the two consequences of genetic drift?

A
  1. Reduction of genetic variation in population can affect organisms ability to adapt to a changing environment
  2. May also contribute to speciation (pops genetically diverging from eachother)
43
Q

Can genetic drift occur with and without a change in population size?

A

Yes
with = survival
without = random reproductive events

44
Q

Can genetic drift introduce new alleles?

A

NO, only gene flow and mutations do

45
Q

Gene flow

Definition

A

Movement of alleles from one population into another

46
Q

In what two ways can gene flow occur?

A
  1. Organism leaves the population they were born into a different population in which they will mate ex. wolf cub leaves pack
  2. Gametes move (not organism) ex. wind/water
47
Q

What is the outcome of bi-directional gene flow?

3

A
  • Allele frequencies start to become more and more similar to eachother
  • Increases genetic variability within a population (introduces new alleles)
  • Can counteract negative effects of genetic drift on pop
48
Q

Organism of the day

American Pika

A

Tolerate warm temps better, juvinelles leave to form new colony and disperse into new areas, important for maintainng genetic variation and reducing genetic drift but problem is WARMER/COOLER temps

gene flow

49
Q

Mutations

Definition

A

Changes in nucleotide sequence of DNA that can create new alleles

50
Q

What are two causes of mutations ?

A
  1. Mistakes made during DNA replication
  2. Environmental exposure to chemical/radiation that causes DNA to break down and mistakes made during repair
51
Q

Mutations: implications for evolution?

A
  • Produces new alleles that give rise to genetic variation that natural selection and genetic drift can act on
52
Q

Why are mutations alone a weak force in changing allele frequencies in a population?

A

They are rare, organisms invest in DNA production and repair

53
Q

What are the two categories of mutations?

A

Somatic: occur in non-reproductive cells = non-heritable
Germline: occur in gametes = heritable

Somatic are not important for evolution

MOST are neutral

54
Q

Harmful vs advantageous mutations

Definition

A

Reduce OR increase an organisms fitness or success

55
Q

Assortive mating

Definition

A

Like mates with like, results in a decrease in heterozygotes and increase in homozygotes

56
Q

Phylogenetic tree

Definition

A

Diagram that depicits the hypothesized evolutionary relationships amongst species

57
Q

What do internal nodes on a PT represent?

A

Speciation events, last common ancestor

58
Q

What does a monophyletic group/clade include?

A
  1. The most recent ancestor of all organisms
  2. ALL of the descendants of that ancestor

SNIP test - if you cut a branch anything that falls off is a clade

59
Q

Paraphyletic group

Definition

A

Does NOT contain all of the descendants of common ancestor

60
Q

Polyphyletic group

Definition

A

does NOT contain the most recent common ancestor

61
Q

Synapomorphies

Definition

A

Homologous traits that were inherited from the most recent common ancestor to the group

Characterizes monophyletic groups

62
Q

Principle of Parsimony

Definition

A

The simplest explanation is most likely to be true

the FEWEST amount of evolutionary changes is most likely to be correct

63
Q

Organism of the day

Rough Skinned Newt

Taricha-granulosa

A

When threatened, curl body to display orange coloration as a warning, produces neurotoxin that is potent when consumed

Tetrodotoxin

64
Q

How do you know what taxa are more closely related?

A

They share a more recent common ancestor in time

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