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BIOL 121 > 2-Evolution Mechanisms > Flashcards

2-Evolution Mechanisms Flashcards

1
Q

biological evolution

A

refers to a change in the (heritable) characters of a population over generations

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2
Q

microevolution

A

changes in allele frequencies in a population in a relative short period of time (one generation)

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3
Q

macroevolution

A

evolution that occurs at or above the species level
- how do new species arise
- Typically occurs over longer periods of time

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4
Q

current theory for evolution

A
  • all species are related
    • Current theory—we all descended from a single called common ancestor (LUCA)
      • ~3.7 billion years ago
  • Species change over time
  • Species do go extinct
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5
Q

EVIDENCE THAT ALL SPECIES SPECIES SHARE A COMMON ANCESTOR

A
  • all living taxa are made of Cells
  • universality of DNA as the genetic code
  • universal flow of Biological information
    • DNA to RNA to amino acids/proteins
  • Near universality of the Genetic code (codons) and DNA replication and repair

Can
Dogs
Beat
Goats?

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6
Q

HOMOLOGIES

A

EVIDENCE OF EVOLUTIONARY RELATEDNESS
traits present in two or more organisms that were inherited from their common ancestor
- anatomical /structural homologies
- Developmental homolgies
- Genetic homologies

homologies structures may or may not be modified in different taxa
- may not look the same (though they often do)
- Nor may they have the same function in different taxa

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7
Q

shared ancestry

A

allows us to study other organisms and apply that knowledge to help us

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8
Q

analogous traits or homoplasies

A
  • arise due to convergent evolution
  • Not inherited form a common ancestor
  • Streamlined shape and finds represent a similar solution to the same environmental demand (moving efficiently through the water)
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9
Q

convergent evolution

A

Independent soleution to an environmental demand

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10
Q

evidence that species have changed with time

A
  • extinctions — in the past (fossils) and today
    • Evidence of evolutionary change through time on the fossil record
  • Transitional fossils
    • Transitional/intermediate forms showing intermediate anatomy between earlier and later forms
  • Vestigial traits
    • Structures that have reduced function or no function compared to its ancestral from due to evolution
  • Real time evidence of charge
    • Evolution of antibiotic resistance in bacteria
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11
Q

mutation

A

any change in the nucleotide sequence of the DNA

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12
Q

germline mutations

A
  • occur in gametes (eggs or sperm)
  • Germline mutations Especially significant for evolution because they can be transmitted to offspring!!
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13
Q

Somatic mutations

A
  • occur in other cells in the body
    • Not heritable!
    • Confined to one cell
    • May or may not affect individuals during their lifetime
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14
Q

what causes high mutation rates?

A
  • organisms that undergo meiosis/mitosis more frequently—higher mutation rates
    • Most mutations occur due to errors in DNA replication
  • Organisms that reproduce more frequently will pass on those mutations to the next generation at a faster rate if mutation in germline cells

Organisms that invest more in DNA protection and repair will have LOWER mutation rates

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15
Q

adaptations definition

A

a structural, functional, or behavioural characteristic of an organism that helps individual survive/reproduce

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16
Q

Evolutionary (Darwinian) fitness

A

a measure of the relative reproductive success of individuals/an individual’s relative contribution of genotype (or phenotype) to future generations

Individuals that pass more genes to the next generation have a higher evolutionary fitness than individuals that pass fewer genes to the next generations

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17
Q

silent mutations

A

Any mutation in the non-coding region is unlikely to affect the phenotype/fitness of an individual

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18
Q

codon

A

3 letter combinations of nucleotides, writes the genetic code

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19
Q

amino acid

A

building block of proteins, is coded for by more than one codon

20
Q

why are mutations a weak evolutionary mechanism?

A
  • most mutations are silent/neutral with respect to fitness—do not matter to evolution
  • Mutations only affect one individual
  • Must occur in a germline cell to be passed on to future generations
  • It takes other evolutionary mechanisms (natural selection) to increase or decrease the new allele frequency in the population
21
Q

sickle-cell anemia

A
  • genetic disease caused by a recessive allele that produces abnormal hemoglobin proteins in red blood cells
  • Reduce oxygen carrying capacity of the blood
  • Blood cells break down prematurely, leading to anemia
  • But… carriers (heterozygotes) are resistent to malaria
22
Q

gene flow

A

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

23
Q

what happens if no gene flow?

A
  • genetic divergence of the two populations
  • Can lead to speciation
24
Q

who introduced the idea of natural selection?

A

charles darwin and. Alfred Russell Wallace. Introduced idea in 1800s

25
Q

natural selection

A

non-random differences in the survival and reproduction o f individuals with certain genotypes and the associated phenotypes in a population over time, generations

26
Q

three requirements for natural selection to occur

A
  1. variation in trait/phenotype in population
  2. Diffferences in fitness associated with the difference in phenotypes
  3. Phenotype must be heritable (genetic component)
27
Q

outcome of natural selection

A
  • increase in frequency with the advantageous phenotype in population over generations
  • Increase in frequency of the beneficial allele
  • Population becomes more well adapted to the environment
  • If environment changes, so can the direction of selection
28
Q

ADAPTATIONS (OR ADAPTIVE TRRAITS)

A

Refer to a heritable trait that increases the ability of an individual to survive and reproduce compared to ppl without that trait

29
Q

when is something NOT an adaptation?

A
  • not heritable
  • No function
  • Does not affect fitness
30
Q

directional selection

A

favours individuals with a phenotype at one end of the distribution of a trait

outcome:
frequency distribution of the trait in the subsequent generation is shifted in one direction from where it was in the parental generation
- average value for a trait is CHANGED!!
- variation (genotypic/phenotypic) tends to DECREASE

31
Q
  1. STABILIZING SELECTION
A

selects against extreme phenotypes at both ends of the frequency distribution
favours intermediate phenotypes, removes extreme phenotypes

outcome:
- average value of the trait remains the SAME
- phenotypic/genotypic variation is REDUCED

32
Q
  1. DISTRUPTIVE SELECTION
A

both extremes are favoured at the expense of intermediate phenotypes

  • average value of the trait remains the SAME
  • increase in phenotypic variation (?)
  • often drives speciation!!!
33
Q

THEORY OF SEXUAL SELECTION

A

certain conscpicuous traits that potential decrease survival could be selected for if they gave an individual an advantage for reproduction, either by:

  • enabling an individual to outcompete rivals for access to a mate
  • increasing the likelihood that an individual would be able to woo a prospective mate
34
Q

sexual dimorphism

A

distinct differences in size/appearance/behaviour/physiology between males and femals

35
Q

the two mechanisms of sexual selection

A

intrasexual selection
- competition for mates
- male-male interactions (mostly)

intersexual selection
- mate choice
- female mate choice (mostly)

36
Q

Intrasexual selection COMPETITION FOR MATES—DIRECT MALE-MALE INTERACTIONS

A
  • males may physically combat each other
  • males may evolve “weapons” that give them an advantage in a fight
  • but… does not always involve direct combat! maybe ornaments and behaviours? maybe mimicry? etc.
37
Q

Direct benefit

A

males can signal that they would provide good parental care

  • providing shelter from the environment
  • protecting female and/or young from threats such as predators
  • can provide resources to the female by bringing gifts
38
Q

indirect benefit

A

male’s phenotype is an indicator or advertisement for good genes/high fitness that can be passed to the female’s offspring

  • usually means the signal has to bear some cost to the female
  • LOOKING BEAUTIUFUL? MEANS DISPLAYING THEIR GOOD GENES!
    • healthy—no parasites
    • good immune system
    • non-damaged DNA, etc
39
Q

Artificial selection

A

people, instead of nature select which individuals get to reproduce and pass their alleles onto the next generation

40
Q

GENETIC DRIFT

A

changes in allele frequencies in a population over time due to random differences in survival and/or reproduction

changes in allele frequencies are not a function of whether the alleles are harmful or beneficial
- occurs in all populations that are not infinite in size
- outcome is due to chance!—sampling error

41
Q

genetic drift on small populations vs large populations?

A
  • random fluctuations in allele frequencies tend to be more pronounced in smaller populations than larger populations
  • small populations tend to lose genetic diversity more quickly than larger populations
42
Q

the opportunities for genetic drift

A
  1. (population) bottleneck event
  2. founder event
  • both events involve a change in population size
  • new population smaller than original population
  • allele frequencies in a population can ALSO change by due to chance events with no change in population size
43
Q

Population bottleneck Event

A

population size is greatly reduced (often over a short time period) for at least one generation (usually due to a catastrophe such as wildfire, flood, etc)

44
Q

founder event:

A

occurs when a new population is founded by a few individuals

45
Q

Transitional fossils

A

Transitional/intermediate forms showing intermediate anatomy between earlier and later forms

46
Q

Vestigial traits

A

Structures that have reduced function or no function compared to its ancestral from due to evolution

47
Q

how to tell when something is an adaptation?

A

Heritable – It has a genetic basis

Functional

Adaptive - Trait must increase the fitness of the organism compared to organisms lacking the trait

Current function – The trait evolved at the same time as the current function.

BIOL 121 (13 decks)

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