Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

+ BIOL 121 > Evolution - Week 7 > Flashcards

Evolution - Week 7 Flashcards

1
Q

What does extant mean?

A

modern-day, currently living (not extinct)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

In a specific type of phylogenetic tree, what would the length of the branch correspond to?

A

the number of substitutions (mutations that made it into the next generation) that appear to have occurred along each branch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

In a specific type of phylogenetic tree, what would a longer length branch represent?

A

more molecule evolution (more change in DNA sequences over time)

*notice how little evolution has occurred in some parts of the tree compared to others

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are phylogenetic trees used to represent?

A

relatedness between many different levels of taxonomic organization (ie. species, subspecies)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a taxon on a phylogenetic tree?

A

species, subspecies, genus, family, etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where are taxa on a phylogenetic tree?

A

tips

they represent extant taxa (usually we only include extant taxa in trees)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are sister taxa?

A

closest relatives in an evolutionary tree

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a root on a phylogenetic tree?

A

common ancestor of the whole tree

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where is the root on a phylogenetic tree?

A

bottom of the phylogenetic tree

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are nodes on a phylogenetic tree?

A

common ancestors

they are NOT present-day species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why are nodes on a phylogenetic tree NOT a present-day species?

A
  • it is impossible for one extant species to be the common ancestor of another extant species
  • any organism or population of organisms that was an ancestor of an extant species would itself now be extinct
    remember that all extant species have undergone evolution compared to their ancestral species

ie. the common ancestor of the gibbon and the human was neither a gibbon, nor a human

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How can you determine which individuals are more closely related?

A

sharing a more recent common ancestor = more closely related

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a monophyletic group (clade)?

A

ancestor and all of its descendants

*remember that even the end of a single branch (lineage) can be considered a clade

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is an outgroup?

A

least related to all other taxa in the tree

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Can you see outgroups in rooted and unrooted trees?

A

rooted trees have clear outgroups

unrooted trees do not have outgroups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What must you remember about the order of the branches (as read across the tips) when reading phylogenetic trees?

A
  • when determining whether or not two trees show the same phylogenetic relationships between taxa, the order of the branches (as read across the tips) is not important
  • branches can rotate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What must you remember about the order of the nodes (ie. from past (root) to present) when reading phylogenetic trees?

A
  • important

- in order to show the same phylogenetic relationships, two trees must display the same monophyletic groupings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is important when thinking about how the phylogenetic tree represents past to present?

A
  • it is not accurate to think of a branch furthest from the root as being closer to the present than a branch closest to the root
  • all branch tips (=extant species) are equally situated in the present day
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does it mean if a branch doesn’t stretch all the way to present-day?

A

the lineage/taxon went extinct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Does fewer offshoots on a tree mean the species is less evolved?

A

NO

just because a species branches off first, that does not mean that it is more ancestral or less evolved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Why are living species not a “sample” of the past?

A
  • modern-day species have all undergone a considerable amount of evolution since branching off from closely related lineages
  • modern-day species are not direct samples of the past
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Do phylogenetic trees include all taxa?

A

NO

remember that these phylogenetic trees often do not include all species that actually exists – the data shown here depends entirely on what we are able to add as data

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What came first, the chicken or the egg?

A

the egg is an ancestral trait here, and appeared before the evolution of chicken

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How do you know which organisms are more closely related to each other on a phylogenetic tree?

A

more recent common ancestor = more closely related

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How are phylogenetic trees constructed?

A

based on the similarity of traits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How do you determine which phylogenetic tree is the “best” tree?

A

count the number of changes (fewest number of steps), and the tree was the fewest amount of changes is the best tree

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How likely is it that a trait evolved more than one separate times?

A

it is more likely that it evolved once

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the principle of parsimony?

A

the simplest explanation is the most likely

  • the tree with the smallest number of changes (derived traits) is the most likely
  • if there are two competing trees that represent relationships between the same group of taxa, the tree that displays the fewest number of trait changes is considered to be the most likely
  • gaining a trait or losing a trait (ie. because the trait turned into something else) are both considered to be changes in the trait
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the relationship between octopus legs and tetrapod logs?

A

analogous traits (they fulfill a similar function), NOT homologous traits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is a synapomorphies?

A

characteristics (traits) present in ancestral species and shared by its descendants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What do synapomorphies define?

A

clades

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Does similarity mean relatedness?

A

NO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What do we use similarity to infer?

A

relatedness between lineages

  • morphological similarity (but be careful!)
  • similarity of DNA sequences
  • based on homologous traits
34
Q

How might 2 organisms be similar without being related?

A

convergent evolution

35
Q

How might 2 organisms be closely related without being very similar?

A

divergent evolution

36
Q

What happens when convergent evolution occurs?

A
  • two organisms may be similar without being related

- homoplasies/analogous traits

37
Q

What happens when divergent evolution occurs?

A

two organisms may be closely related without being very similar

38
Q

What are the “best” phylogenetic trees based on?

A
  • highly heritable traits (ie. DNA sequences)

- many different traits

39
Q

What are homologies (homologous traits)?

A

traits that are similar because they were inherited from a common ancestor (ie. five digits)

40
Q

What are homoplasy (analogous) traits?

A

trait shared, but not because of shared evolutionary history

41
Q

What is convergent evolution?

A

independent evolution of similar (convergent) traits in multiple lineages

42
Q

Why might traits be similar due to convergent evolution?

A

because they evolved under similar selective pressures, NOT because of inheritance

43
Q

What is divergent evolution?

A

evolution of differences between closely related groups or lineages

44
Q

Why might traits be different due to divergent evolution?

A

because they evolved under different selective pressures

45
Q

What is an ancestral trait?

A

trait that is shared with the ancestor

46
Q

What is a derived trait?

A

trait that has evolved in a lineage that is different from ancestral state

  • a trait is derived if it represents a change from a relatively ancestral form of the trait (ie. no hair → hair)
47
Q

What are similar traits due to?

A
  • inheritance from a common ancestor

- convergent evolution

48
Q

What is homology?

A
  • inheritance from a common ancestor

- forms homologous traits

49
Q

What do organisms with homologous traits reflect?

A

relatedness between lineages

50
Q

What is homoplasy?

A
  • convergent evolution

- forms analogous traits

51
Q

What do organisms with analogous traits reflect?

A

evolution under similar selection pressures

52
Q

How do most species arise?

A
  • one existing species turns into another species
  • one existing species splits into two species
  • two existing species combine to create one new species
53
Q

What is speciation through hybridization?

A

two existing species combine to create one new species

- possible, but requires a very special set of circumstances

54
Q

What are the special set of circumstances required fro hybridization?

A
  • reproductively isolated from either parental species in order to be considered a new species, AND
  • be able to successfully produce their own offspring
55
Q

Speciation Through Divergence

What is a speciation event?

A

what was initially one species is about to split into two independent lineages
- the two lineages diverge from one another through time until they are so different that we recognize them as a separate species

56
Q

Speciation Through Divergence

What would happen in the case of a species that exists in multiple populations?

A

it seems unlikely that those populations would all evolve in exactly the same way at exactly the same time (although this might happen if the populations were all under the same type of selection, or if there was a lot of gene flow between the populations)

  • what might be more likely is one population evolving into a new species, while the other population remains unchanged
  • if the original species went extinct very soon after the speciation event, it would appear as though the entire species turned into a completely new species
57
Q

Speciation Through Divergence

Describe the 3 steps of a speciation event.

A
  1. low gene flow between populations: populations are somehow prevented from interbreeding
  2. population allele frequencies begin to diverge due to evolutionary mechanisms
  3. populations diverge enough that they are considered different species: different species = evolutionary independent populations
58
Q

How do we know if a ‘different’ species is different enough?

A

species concept

59
Q

In what ways may asexual organisms be considered evolutionary independent from each other?

A
  • in terms of the resources they use
  • in terms of how they look (morphology)
  • they belong to separate clades
  • in terms of their DNA sequences
60
Q

In what ways may sexual organisms be considered evolutionary independent from each other?

A
  • in terms of the resources they use
  • in terms of how they look (morphology)
  • they belong to separate clades
  • in terms of their DNA sequences
  • they belong to separate gene pools (=reproductively isolated)
61
Q

What are the pre-zygotic (pre-fertilization) mechanisms of reproductive isolation?

A
  • spatial isolation (isolation by living in different habitats)
  • temporal isolation
  • behavioural isolation (different mating behaviour)
  • mechanical isolation (different parts)
  • gametic incompatibility
62
Q

What are the post-zygotic (post-fertilization) mechanisms of reproductive isolation?

A
  • hybrids are inviable

- hybrids are sterile

63
Q

How can low hybrid fitness influence selection for pre-zygotic isolating mechanisms?

A
  • if hybrid offspring have lower fitness than nonhybrids, individuals that avoid producing hybrid offspring will be more reproductively successful
  • certain traits might influence how likely an individual is to produce hybrid vs. non-hybrid offspring

ie. some females may avoid mating with individuals that look/smell like they belong to a different species
- there is heritable variation in such traits, they could evolve due to natural selection
- post-zygotic isolating mechanisms (ie. low hybrid fitness) could result in natural selection for pre-zygotic isolating mechanisms (ie. behavioural isolation, in the form of different mating behaviours)

64
Q

Spatial Isolation due to Vicariance

What is vicariance?

A

the physical splitting of one population into two or more smaller populations, due to a geographic barrier (ie. river, mountain range, etc.)

65
Q

Spatial Isolation due to Vicariance

Describe the 3 steps of a speciation event.

A
  1. low gene flow between populations: populations can no longer interbreed (what kind of barriers are there?)
  2. population allele frequencies begin to diverge: what kinds of evolutionary mechanisms are involved? (ie. mutation, natural selection, genetic drift)
  3. populations diverge enough that they are considered different species: under which species concept?
66
Q

Spatial Isolation due to Dispersal

What is dispersal?

A

movement of organisms from one location to another

67
Q

Spatial Isolation due to Dispersal

Describe the 3 steps of a speciation event.

A
  1. low gene flow between populations: populations can no longer interbreed (what kind of barriers are there?)
  2. population allele frequencies begin to diverge: what kinds of evolutionary mechanisms are involved? (ie. mutation, natural selection, genetic drift)
  3. populations diverge enough that they are considered different species: under which species concept?
68
Q

Distinguish between mechanisms resulting in physical isolation (ie. forming allopatric populations) vs. evolutionary mechanisms (ie. mutation, gene flow, genetic drift, natural selection).

A

mechanisms resulting in physical isolation: describe how those populations came about

evolutionary mechanisms: describe the changes in the allele frequencies on that population as a result of that event on the population(s)
- in step two of speciation, where the population allele frequencies begin to diverge, it may require more than just one evolutionary mechanism to be involved

69
Q

What is speciation?

A

evolutionary independence of a group of organisms

70
Q

What are the prerequisites for speciation?

A

evolution is the only thing absolutely necessary

  • in order to become evolutionarily independent from one another, two groups of organisms must evolve along separate evolutionary paths
71
Q

Why might physical separation of populations not be necessary for speciation?

A

it may be possible to have low gene flow between two populations and subsequent divergence and speciation, even if the two populations are in contact with one another

72
Q

Why isn’t natural selection necessary for speciation?

A

other evolutionary mechanisms (ie. genetic drift) could also cause two populations to diverge

73
Q

What is an allopatric population?

A
  • found in separate geographic areas

- populations are physically isolated from one another

74
Q

What is a sympatric population?

A
  • exist in the same geographic area

- individuals regularly encounter one another

75
Q

What mechanisms of reproductive isolation can possibly lead to sympatric speciation?

A

pre-zygotic:

  • temporal isolation
  • behavioural isolation (different mating behaviour)
  • mechanical isolation (different parts)
  • gametic incompatibility

post-zygotic:

  • hybrids are inviable
  • hybrids are sterile
76
Q

What is the species concept?

A

different ways of defining species

77
Q

What are the 4 species concepts?

A
  • phylogenetic = smallest possible monophyletic group
  • biological = interbreeding populations
  • morphological = specific form & function
  • ecological = specific niche (ie. habitat, food, predators)
78
Q

Phylogenetic Species Concept

What is a species?

A

smallest possible monophyletic group

79
Q

Phylogenetic Species Concept

Why is a single human population not a true monophyletic group on its own?

A
  • high degree of interbreeding between human populations
  • in order to create something resembling a monophyletic group, we would have to include all of humanity
  • in other words, according to the phylogenetic species concept, all humans belong to the same species
80
Q

Phylogenetic Species Concept

When is divergence between populations possible for sexually reproducing species?

A

only if there is a lack of gene flow between those populations

*a lack of gene flow does not cause divergence, it only makes divergence possible

81
Q

Phylogenetic Species Concept

How does gene flow have a homogenizing effect on allele frequencies?

A
  • if there is gene flow between two populations, then what happens to allele frequencies in one population will influence what happens to allele frequencies in the other population
  • two lineages that have been sharing alleles with one another will not be evolutionarily independent, and they will not form separate monophyletic groups
  • descendants in one population will have ancestors from both parent populations, and both populations will show much of the same variation in traits
  • instead of being two separate branches on a phylogenetic tree, the populations will form one large branch

+ BIOL 121 (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions