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Biol 121!!! > Evidence for Evolution/Mechanisms of Evolution > Flashcards

Evidence for Evolution/Mechanisms of Evolution Flashcards

1
Q

What are the 4 mechanisms for evolution??

A
  1. Mutations
  2. Gene flow
  3. Natural selection (including sexual selection)
  4. Genetic Drift
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2
Q

Evolution - Definition

A

change in the (heritable) characteristics of a population over generations
- can be micro or macro

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3
Q

Microevolution

A

Changes in allele frequencies in POPULATION over short period of time (EX ONE GENERATION)

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4
Q

Macroevolution

A

occurs at or above the species level - how new species arise. occurs over long time periods

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5
Q

whats the current theory of evolution??

A

we’re all descended from single celled ancestor (LUCA - Last Universal Common Ancestor) which existed around 3.7 billion years ago

species change through time

species can go extinct

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6
Q

evidence that all species share a common a common ancestor

A
  1. all living things are made of cells
  2. the universality of DNA as the genetic code
  3. universal flow of biological info (DNA to RNA to amino acids/proteins)
  4. almost universality of genetic code (codons) and DNA replication/repair
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7
Q

what does all species sharing common ancestor help us do

A

use bacterial gene editing to edit our genome (CRISPR-Cas9)

crazy things like insert jellyfish gene that codes for green light protein into a cat

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8
Q

evidence that species are related to each other (evolutionary relatedness)

A
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9
Q

homologies

A

traits present in two or more organisms INHERITED FROM THEIR COMMON ANCESTOR

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10
Q

homologies can be…

A
  1. anatomical/structural
  2. developmental
  3. genetic
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11
Q

anatomical/structural homologies

A

ex in bone structure - human, horse, seal, turtle etc all have a humerus, radius, ulna, carpals, metacarpals, phalanges

homologous structures may not look the same in different species and may not have the same function

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12
Q

developmental homologies

A

developmental similarities in early embryonic stages (because of inheritance of developmental processes from a common ancestor)

ex humans had gills and tails during development, developmental homology with cats and chickens

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13
Q

genetic homologies

A

genetic similarities between organisms due to common ancestry

ex. human and chimp DNA is about 99%

since some dna sequences can code for the same proteins, its possible for two species to have around 85% genetic similarity but 100% protein similarity in a specific gene

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14
Q

analogous traits/homologies

A

occur as an independent solution to an environmental demands - CONVERGENT EVOLUTION

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15
Q

convergent evolution

A

independant solution to an environmental demand

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16
Q

evidence that species have changed with time

A
  1. extinctions in the past and today
  2. transitional fossils
  3. vestigial traits
  4. real time evidence of change
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17
Q

evidence of evolutionary change from fossil record

A

looking at fossils from the past and comparing to animals now - show that life on earth was once different from life on earth today

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18
Q

evidence of evolutionary change - transitional fossils

A

transitional/intermediate forms showing intermediate anatomy between early and later forms of species

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19
Q

evidence of evolutionary change - vestigial structures

A

structures w/ reduced or no function compared to ancestral form due to evolution

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20
Q

ex of vestigial structures

A

pelvic bones in whales and dolphins from when ancestors walked on land 40 mill years ago

humans - smooth muscles in skin called arrector pili, make us get goosebumps, also ear muscles to change direction of ears

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21
Q

real time evidence of evolutionary change

A

evolution of antibiotic resistance in bacteria - populations can change overtime but always over generations

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21
Q

mechanisms of evolutionary change

A
  1. mutations
  2. gene flow
  3. natural selection (inc sexual selection)
  4. mutations
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22
Q

Mutation definition

A

any change in the nucleotide sequence of DNA

  • can range in size from one nucleotide to large segments of a chromosome that affect multiple genes
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23
Q

point mutation OR ____

A

SNiP - and mutation that alters a single base pair, or small number of adjacent base pairs

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24
Q

what does SNiP stand for

A

single nucleotide polymorphism

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25
Q

main causes of point mutations

A
  • errors during DNA replication (most commonly)
  • errors during repair of DNA damaged by radiation/chemical mutagens
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26
Q

more causes of mutations (more than just SNiP)
NOT TESTABLE

A
  • unequal crossing over
    -chromosome inversion from DNA breakage (radiation)
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27
Q

where can mutations occur/what does that mean?

A

mutations can occur in germline and somatic cells

somatic cells - not heritable, confined to one cell, and may not affect individuals during their lifetime

germline cells - in gametes, significant for evolution because HERITABLE, could potentially affect every cell in the body

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28
Q

how can mutation vary amongst species??

A

if undergo mitosis/meiosis more frequently - higher mutation rates (most mutations occur in DNA replication)

org. that reproduce more quickly pass on those mutations faster (IF mutations in germline cells)

org. that invest more in DNA protection and repair lower mutation rates

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29
Q

pros and cons high mutation rate?

A

pros, population can aquire new phenotype/adapt to new environments more quickly

cons, easier to lose current adaptations

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30
Q

darwinian fitness

A

measures the relative reproductive success
OR
individuals relative contribution of genetype/phenotype to future generations

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31
Q

neutral mutations

A

mutations are random, not related to how helpful it would be

only 2% of our DNA codes for proteins, so mutation in non coding regions wouldn’t affect phenotype/fitness

codon is also written in 3 letter codes, multiple codons creating the same amino acid so a a mutation in coding region may not affect the individual at all

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32
Q

harmful mutations

A

reduce an organism’s fitness, reduce survival/fertility

ex. cystic fibrosis, cancer

33
Q

beneficial mutations

A

increase an organism’s fitness, increase likelihood of survival ^ fertility

34
Q

how the environment affects the fitness effects of mutations

A

ex sickle cell anemia - recessive allele produces abnormal hemoglobin proteins in red blood cells (makes them sickle shaped)

cons - reduced oxygen carrying capacity, oxygen deprivation can lead to organ damage and stroke, blood cells break down prematurely - anemia

pros - carriers are resistant to malaria, mutation is beneficial where malaria is common but harmful where malaria is rare

35
Q

what makes mutations beneficial??

A
  • ultimate source of genetic variation
    -generates new allels
    -new phenotypes
    -raw materials for evolution to take place
    -EVOLUTION COULDN’T OCCUR WITHOUT THEM
36
Q

are mutations a strong or weak evolutionary mechanism?? why??

A

weak!
- most are silent/neutral w respect to fitness
- mostly only affect one individual (unless occuring in germline cells)
- takes other evolutionary mechanisms to increase/decrease new allele in population
- only mutations with strong selective advantage are likely to sweep through population

37
Q

gene flow definition

A

the movement of alleles between populations caused by dispersal (of individuals or gametes) and mating

change allele frequencies in new population/introduce new alleles

38
Q

what happens when individuals are moving between populations (gene flow)??

A

homogenizes allele frequencies between populations over time

39
Q

what happens when little to no gene flow?

A

genetic divergence between population - if this continues it can lead to speciation

40
Q

Natural selection

A

Non-random differences in the survival and reproduction of individuals with certain genotypes/phenotypes in population over generations

41
Q

three requirements for natural selection to occur *****

A
  1. VARIATION in trait/phenotype amongst individuals (selection acts on the phenotype)
  2. DIFFERENCES IN FITNESS associated with the different phenotypes
  3. the phenotype must be HERITABLE - so survivors leave more offspring w/ the same phenotype
42
Q

randomness with mutations and selections

A

mutations are random w/ respect to fitness, but the probability of that allele passing onto the next generation is NOT random

43
Q

adaptations

A

process in which individuals become more well adapted to environment as a result of mutations/natural selection
OR
heritable trait that ^ ability of an individual to survive and reproduce compared to individuals without the trait

44
Q

what can adaptations be??

A

structural, physiological, behavioural

45
Q

a trait is NOT an adaptation if…

A
  • not heritable
  • not functional
  • does not affect fitness
46
Q

if asked a question about whether natural selection has occured, what should you include???

A

the three requirements for natural selection to occur - heritable, variation in phenotype, differences in fitness associated with diff phenotypes

46
Q

if asked a question about whether natural selection has occured, what should you include???

A

the three requirements for natural selection to occur - heritable, variation in phenotype, differences in fitness associated with diff phenotypes

47
Q

three modes of natural selection

A
  1. directional
  2. stabilizing
  3. disruptive
48
Q

directional selection

A

favours individual w phenotype at one end of spectrum, frequency distribution of the trait is shifted in the direction of the favourable trait

OUTCOME - changes average value for trait in population & decrease in phenotypic variation

can change directions

49
Q

stabilizing selection

A

favours intermediate phenotypes, selects against phenotypes at extreme ends of the spectrum

OUTCOME - average value of the phenotype remains the same, phenotype/genotype variation is reduced

ex baby weight, not too heavy or too small, also robins lay 4 eggs, too little and none may survive, too many not enough food to go around

50
Q

disruptive selection

A

phenotypes at either end of the spectrum favoured, not intermediate phenotypes

OUTCOME - average value of the trait remains the same, increase in phenotypic variation

ex small and sneaky chinook salmon vs large and fighty salmon, middle no

51
Q

trends in directional, stabilizing, and disruptive selection

A

DIRECTIONAL - average trait value increase or decrease, phenotypic variation reduced

STABILIZING - average trait value same, phenotypic variation reduced

DISRUPTIVE - average trait value same, phenotypic variation increased

52
Q

how sexual selection came about

A

natural selection is largely ecological, but traits were observed that logically wouldnt actually benefit the individuals fitness. An explanation for this is that those traits make the individual more likely to find a mate and reproduce

53
Q

sexual dimorphism

A

distinct differences in size, appearance, behaviour, physiology between males and females

54
Q

two mechanisms of sexual selection

A
  1. intrasexual selection (competition for mates, mostly male-male)
  2. intersexual selection (mate choice, female choice mostly)
55
Q

intrasexual selection

A

can involve physical battles between males, more outward displays of dominance (ex size) or sneaky/indirect tactics

copulatory plug, scoop shaped penis, marking females, destroying sperm etc

56
Q

what is male fitness linked to

A

number of mating opportunities

57
Q

asymmetric cost of reproduction

A

females invest much more time and energy into reproduction and caring for offspring compared to males

58
Q

two things that would make a male more enticing to a female

A
  1. male better at providing direct benefits - food, shelter, protection
  2. male better indirect benefits - good genes, maximize fitness of the females offspring
59
Q

direct benefits from males

A

male signal that they would provide good parental care

ex. female lions preferentially mate with lions with darker manes, this signals, older age (survivor) high testosterone levels (fighting ability), good protector

males could demonstrate that they can provide resources by bring gifts (nuptial gift)

60
Q

indirect benefit

A

phenotype is an indicater of good genes/high fitness could be passed to females offspring

look fab! - healthy, good immune system, non-damaged dna

61
Q

artificial selection

A

people rather than nature select which individuals get to reproduce and pass genes onto the next generation

62
Q

again! what are the 4 mechanisms of evolution

A
  1. mutations
  2. gene flow
  3. natural selection
  4. genetic drift
63
Q

genetic drift definition

A

drifting of allele frequencies over time due to RANDOM differences in survival and/or reproduction

64
Q

what sort of population does genetic drift affect more??

A

small populations, which tend to lose genetic diversity more quickly

65
Q

what in math is genetic drift equivalent to

A

sampling error, like flipping a coin twice and getting heads twice. doesnt mean 100% chance of heads just random

65
Q

what in math is genetic drift equivalent to

A

sampling error, like flipping a coin twice and getting heads twice. doesnt mean 100% chance of heads just random

66
Q

what are two opportunities for genetic drift??

A
  1. Population bottle neck event
    - current population decreases by large amount, likely diff allele frequency
  2. Founder effect
    - new population founded, allele frequency different from parent population
  • both involve a change in population size, one where result is substantially smaller than original
67
Q

population bottleneck event

A

population size is greatly reduced over a very short period of time, usually due to a natural disaster such as a wildfire etc

all down to chance, wrong place at the wrong time, so could not change allele frequency at all or could change it a lot!

68
Q

founder effect

A

new population is founded be a few individual, founders isolated from og population so no gene flow

allele frequencies in new pop can be very very different from original

69
Q

very bad founder event

A

invasive species :(

can be significant losses in allelic diversity in new population

disrupts ecosystems

70
Q

can genetic drift happen without reduction in population size??

A

YES!!! could just be completely random and related to reproduction rather than survival, right place at right time

71
Q

potential impacts of genetic drift

A

if a large loss of genetic diversity occurs, populations can lose important physiological features, resistance to diff things, adaptations etc. ex when northern elephant seal population reduced greatly, lost skull symmetry

72
Q

differences between genetic drift and gene flow

A

genetic drift involves movement within a population whether thats reduction in size or moving to a new place, can increase or decrease the frequency of an allele but can’t introduce new ones founder effect specifically reduces genetic variation

gene flow could introduce a new allele because of individuals from another population joining the current one - MOVEMENT OF INDIVIDUALS OR ALLELES, could increase genetic variation

73
Q

genetic drift v natural selection

A

genetic drift involves random sampling, while natural selection is specific

genetic drift is unpredictable while natural selection is

74
Q

MUTATIONS (summary)

A

change in an individuals DNA, must occur in gametes in order to be a mechanism of evolution, random, weak force but very important

EFFECT ON GENETIC VAR: increases genetic variation by introducing new alleles

EFFECT ON AVG FITNESS: not all have an affect, many are neutral, can be harmful or beneficial, and can depend on environment

75
Q

GENE FLOW (summary)

A

changes in allele frequencies from movement of individuals or gametes between populations

EFFECT on GEN VARIATIO: could increase by incroducing new alleles recieving population, decrease by removing alleles from giving poplation, can also HOMOGENIZE populations

EFFECT on AVG FITNESS: could increase, decrease, or no effect on fitness depending on the allele

76
Q

NATURAL SELECTION (summary)

A

Individuals with heritable trait have higher fitness than without, NON RANDOM, requires; a)heritable b)variation c)diff in fitness between variations

EFFECT on GEN VARIATION: generally decrease genetic variation unless disruptive selectioon

EFFECTS on AVG FITNESS; gen increase fitness over time

77
Q

GENETIC DRIFT (summary)

A

changes in allele frequencies over time due to chance/random events

EFFECTS on GEN VARIATION: generally reduces variation

EFFECTS on AVG FITNESS: generally random w respect to fitness, or reduces avg fitness

Biol 121!!! (3 decks)

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