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evolution Flashcards

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Biology 101 flashcards
1
Q

where does trait evolution occur on a phylogenetic tree?

A

internodes

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2
Q

tips

A

summations over their evolutionary history

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3
Q

relationship between relatedness and similarity

A

-similarity does not determine relatedness
-the number of trait changes does not determine relatedness

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4
Q

separate ancestry

A

the alternative hypothesis to common ancestry, which proposes that each living taxon has an independent origin

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5
Q

rate of trait evolution

A

-about the same for all branches
-the expected number of changes from the root will be the same for all living tips
-more nodes does not equal more trait changes
-all living species are equally “evolved”

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6
Q

exceptions to the nesting pattern within the common ancestry model

A

-a trait might evolve independently a few times
-a trait may evolve and later on be lost on one or more lineages

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7
Q

homologous trait

A

trait shared in separate species that derives from the same evolutionary origin

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8
Q

non-homologous trait

A

trait shared in separate species that derives from different evolutionary origins through convergent evolution

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9
Q

principle of parsimony

A

the hypothesis that invokes the fewest changes is most likely to be true; this reasoning works so long as the trait is one that evolves relatively rarely

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10
Q

occam’s razor

A

similar to parsimony; the simplest explanation for an observation is most likely the correct one

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11
Q

are trait gains or losses more likely?

A

equally likely

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12
Q

convergent evolution

A

the same trait evolves separately in more than one lineage; although they appear similar, these traits are not homologous

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13
Q

reversal

A

an ancestral trait was lost and then re-evolved along a lineage; makes the trait non-homologous

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14
Q

ancestral trait reconstruction

A

if we know where changes occurred, we also know ancestral states

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15
Q

evolution’s 3 big ideas

A

1) common ancestry unites all life
-diverse living species descend
from common ancestors
2) populations evolve
-the genetic composition of
populations changes over time
3) natural selection provides direction
-adaptations are explained by
natural selection (and related
processes)

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16
Q

phylogenetic tree

A

a branching diagram used to represent evolutionary relationships and relatedness between different organisms based on their common ancestry

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17
Q

root

A

the base of a tree, representing the common ancestral lineage of all taxa in the tree

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18
Q

branch

A

the lines that make up a tree diagram, which represent population lineages

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19
Q

taxon (plural= taxa)

A

a named group of biological organisms, often shown at the tips of a tree

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20
Q

lineage splitting/speciation

A

splitting of a population into genetically separate populations that no longer have gene flow; the origin of multiple species from a few ancestral species

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21
Q

node

A

branching point on a tree diagram, which represents lineage splitting

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22
Q

reasons for lineage splitting

A

-geographic changes
-climate changes
-rare dispersal events

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23
Q

clade

A

all descendants of an ancestral lineage

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24
Q

sister clade/lineage

A

lineages or clades from the same node

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25
Q

tree topology

A

a list of all clades a tree contains; stable to pruning

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26
Q

relatedness

A

recency of common ancestry

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27
Q

biogeography

A

the geographic distribution of living organisms

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28
Q

common ancestry

A

the concept that if you trace back the lineages of living species far enough in time, those species will converge to a shared ancestor

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29
Q

evidence for common ancestry

A

-biogeography
~similar species occur near one
another
-fossil record
~transitional forms in temporal
sequence
-homology
~surprising similarities among
organisms
-classification
~hierarchical nesting of biological
taxa

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30
Q

homology

A

traits whose similarities are explained by common ancestry

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31
Q

transitional fossil

A

fossil taxa that have some, but not all, of the derived traits of a living group

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32
Q

nested hierarchy/classification

A

a pattern of groups nested within groups (without overlaps) as seen in taxonomies

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33
Q

polymorphism

A

the existence of multiple variants within a population

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34
Q

evolution

A

the change in frequency of genetic variants within a population; changes in allele frequency of a population over time

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35
Q

fixation

A

the loss of all variants except one from a population

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36
Q

natural selection

A

the tendency for genetic variants that enhance fitness to go to fixation and variants that reduce fitness to be lost from a population, making the population better suited to its environment over time

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37
Q

plasticity

A

changes caused by the environment that do not have a genetic basis

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38
Q

locus

A

a place in the genome where alleles reside; in diploids, each individual has two alleles per locus

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39
Q

allele frequency

A

in a population, the proportion of all alleles at a locus that are of a particular type; changes in allele frequency over time causes evolution

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40
Q

heritable variation

A

allelic variation is segregating in a population

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41
Q

what determines phenotype of an individual?

A

the alleles they carry at many loci and the environment

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42
Q

hardy-weinberg assumptions

A

-no mutation
-no migration
-no selection
-mating is random with respect to the alleles

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43
Q

hardy-weinberg law

A

assuming assumptions hold:
-homozygote frequencies are the
square of the corresponding allele
frequency (p^2 or q^2)
-heterozygote frequencies are twice
the product of their allele
frequencies (2pq)

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44
Q

deviations from hardy-weinberg assumptions that cause evolution

A

-selection: alleles do not have equal fitness
-genetic drift: population is not infinitely large

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45
Q

probability that an allele becomes fixed under genetic drift

A

equal to that allele’s frequency

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46
Q

genetic drift

A

random change in allele frequencies in a population over time

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47
Q

genetic bottleneck

A

phenomenon in which a population lineage shrinks to a small size for a period, causing that population to lose genetic variation; occurred during the expansion of human populations around the world

48
Q

how does directional selection affect genetic drift?

A

directional selection biases the genetic drift towards the favored allele

49
Q

when can genetic drift overcome directional selection?

A

when the population is small and the allele being selected starts at a low frequency

50
Q

directional selection

A

occurs when genotypes differ in fitness and one allele is favored; eventually the beneficial allele is expected to become fixed in the population

51
Q

relative fitness

A

the fitness of a given genotype divided by the fitness of a reference genotype, which relative fitness is assigned to be 1.0

52
Q

beneficial mutation

A

a new allele that enhances the fitness of organisms

53
Q

deleterious mutation

A

a new allele that decreased organismal fitness

54
Q

neutral mutation

A

a new allele with neither a beneficial nor deleterious effect

55
Q

over-dominant selection

A

heterozygotes have the highest fitness; acts on a few genetic disease loci

56
Q

under-dominant selection

A

homozygotes have the highest fitness

57
Q

trans-specific polymorphism

A

a set of alleles that are shared between closely related species; they arose before speciation and were maintained as polymorphisms; can be explained by over-dominant selection

58
Q

continuous trait

A

a trait that is characterized by values on a continuous scale, rather than being controlled by a single locus

59
Q

disruptive selection

A

selection that favors trait values at both ends of the trait value distribution; mean stays the same, variance increases

60
Q

heritability (h^2)

A

the fraction of the variation in a population that can be explained by genetics

61
Q

response to selection (r)

A

the amount the mean trait value in a population changes after one generation

62
Q

stabilizing selection

A

selection that disfavors extreme trait values and favors trait values towards the center of the trait value distribution; mean stays the same, variance decreases

63
Q

standard deviation

A

square root of variance

64
Q

variance

A

a measure of the spread of distribution of trait values in a population (the sum of the squared deviations from the mean value)

65
Q

strength of selection

A

mean of the reproducing individuals minus the mean of the whole population

66
Q

exaptation

A

the phenomenon in which a trait that evolved for one function is currently used for a different function

67
Q

exaggerated secondary sexual characteristics

A

dramatic traits in an organism that lower the organism’s viability but evolve because they are favored by sexual selection

68
Q

sexual selection

A

directional selection in which the selective pressure is on mating, instead of on survivorship

69
Q

runaway sexual selection

A

the phenomenon in which secondary sexual traits become exaggerated due to feedback between male traits and female preferences

70
Q

polygamy

A

the phenomenon in which one male can mate with many females

71
Q

monogamy

A

the phenomenon in which one male mates with one female

72
Q

altruism

A

actions (or tendencies to act) that result in the organism exhibiting the behavior lowering its own fitness while increasing the fitness of other organisms within its population

73
Q

group selection

A

in a population composed of subgroups that vary in their frequency of altruistic individuals, subgroups with more altruists leave more offspring than ones with primarily non-altruists

74
Q

biological species concept

A

the view that species are defined by the ability of their members to reproduce with one another and to be unable to reproduce with members of other species

75
Q

phylogenetic species concept

A

the view that species are clades (monophyletic groups), like other in the taxonomic hierarchy, that biologists have chosen to assign to the species rank for practical reasons

76
Q

clinal variation

A

gradual changes in traits as a function of geographical separation

77
Q

discrete variation

A

genetic variation among geographically separated populations, where each population contains genetically similar individuals

78
Q

Fst

A

ranges from 0 to 1 with higher values indicating more genetic variation between subpopulations (0.25 is sufficient to recognize biological races)

79
Q

speciation

A

the splitting of ancestral species into descendant species

80
Q

allopatric speciation

A

speciation driven by geographical isolation

81
Q

assortative mating

A

the phenomenon in which individual organisms tend to mate with other organisms with trait values like their own

82
Q

sympatric speciation

A

speciation without geographical isolation, driven by disruptive selection and assortative mating within a population; rare

83
Q

extrinsic reproductive isolation

A

the phenomenon in which two organisms are unable to reproduce due to geographic isolation

84
Q

intrinsic reproductive isolation

A

the phenomenon in which two organisms are no longer able to reproduce, even when they are allowed to encounter one another

85
Q

oxygenic photosynthesis

A

the reduction of carbon dioxide to organic molecules using light energy in which water is the electron donor and oxygen gas is released

86
Q

anoxygenic photosynthesis

A

the reduction of carbon dioxide to organic molecules using light energy in which something other than water is the electron donor and oxygen gas is not released

87
Q

great oxidation event

A

the evolution of cyanobacteria to perform oxygenic photosynthesis and oxygenate the atmosphere

88
Q

common traits of cellular life

A

-proteins and L-amino acids
-genetic molecules
-genetic system
-metabolic system

89
Q

last universal common ancestor (LUCA)

A

-last living thing ancestral to all known life
-had all features shared by archaea, bacteria, and eukaryotes including a metabolism and genetic system that contained ribosomes, DNA, and proteins

90
Q

bacteria

A

prokaryotic cells that perform critical functions for our biosphere including cycling carbon, photosynthesis, and chemosynthesis; can be parasitic or mutualistic; metabolically diverse

91
Q

cyanobacteria

A

only lineage to evolve oxygenic photosynthesis; can be single-celled or form filaments of many cells

92
Q

archaea

A

metabolically diverse; membranes are made of ether-linked isoprenoids

93
Q

prokaryotic cells

A

lack membrane bound organelles; consist of bacteria and archea

94
Q

organelle

A

membrane-bound compartment of a eukaryotic cell

95
Q

endomembrane system

A

other membrane-bound organelles, including the endoplasmic reticulum, golgi apparatus, and secretory vesicles

96
Q

endosymbiosis

A

the phenomenon in which a prokaryotic cell comes to live and divide within a host cell

97
Q

evidence for endosymbiosis as the origin of the mitochondria

A

-bacteria and mitochondria both contain a circular genome and ribosomes
-mitochondria perform biochemical reactions in a similar manner to some free-living alphaproteobacteria
-mitochondria arise from the growth and division of existing mitochondria
-phylogenetic analysis of genes in the mitochondrial genome

98
Q

autogenous hypothesis for eukaryotes

A

the theory that mitochondria and nuclei both evolved within the same eukaryotic lineage

99
Q

outside-in model

A

the theory for the development of eukaryotes that starts with the production of vesicles within the cytoplasm by internalization

100
Q

inside-out model

A

the theory for the development of eukaryotic internal compartments that suggests that the outer plasma membrane of a prokaryotic ancestor was pushed outward and ultimately fused to create the cytoplasm and plasma membrane of eukaryotes

101
Q

asgard archaea

A

prokaryotes more closely related to eukaryotes than any other organism; produce extracellular protrusions, including long filamentous ones; provides support for the inside-out theory

102
Q

mitochondria

A

derived from alphaproteobacteria

103
Q

plastids

A

derived from cyanobacteria

104
Q

characteristics of hominids

A

-bedding down
-diurnal
-complex social systems capable of coordinated actions as a group
-problem solving skills

105
Q

differences between humans and other hominids

A

-opposable thumbs
-less body hair
-larger brain
-shorter gut
-physically weaker
-fully bipedal
-better at throwing
-better at problem solving
-true language

106
Q

diurnal

A

the characteristic of being active during the day

107
Q

hominid

A

great ape clade; of the primate clade; sister clade is gibbons

108
Q

arboreal

A

tree-dwelling

109
Q

hominin

A

all modern and extinct humans and their immediate ancestors

110
Q

hypotheses of bipedality origin

A

1) by being upright, it is easier to look for prey and predators in the grassy savannas
2) if you are upright, your hands are free to do actions such as carrying and throwing
3) in a vertical position in a hot savanna, an organism intercepts less sun and is better at cooling
4) for long distances, hominins are more efficient at locomoting than other hominids (not supported)

111
Q

introgression

A

the transfer of genetic information between species

112
Q

admixture

A

the mating of two individuals from genetically distinct groups

113
Q

evolutionary events that changed the planet

A

1) oxygenic photosynthesis (cyanobacteria)
2) invasion of land (plants)
3) agriculture and technology (humans)

114
Q

anthropoids

A

monkeys; mainly frugivores

115
Q

frugivory

A

diet of fruits and succulent-like produce from plants

bio 152 (3 decks)

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