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Biology > Speciation and Phylogenies > Flashcards

Speciation and Phylogenies Flashcards

1
Q

What is speciation

A

The process by which one species divides into two

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2
Q

How do you initate the speciation process

A

Restricting gene flow between isolated populations

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3
Q

Whats allopatric speciation

A

Involves physical seperation between two populations

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4
Q

Whats vicariance

A

A type of allopatric speciation, large populations become split into two via a physical barrier

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5
Q

Whats peripatric

A

A peripheral population is established outside the original range of the population and forms an independant colony

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6
Q

Whats sympatric speciation

A

A population being split into two reproductively isolated populations while staying in the same geographic location

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7
Q

Whats parapatric speciation

A

When neighbouring populations of a species are geographically connect and exchange genes but diverge into seperate species

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8
Q

How can allopatric speciation occur

A

Vicariance e.g. mountain uplifts or peripatric e.g. dispersal to oceanic islands

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9
Q

Example of vicariance (1)

A

Isthmus of Panama in central America, the isthmus closed 2.8 million years ago and now species show adapted divergence either side of the lung bridge

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10
Q

Examples of vicariance (2)

A

Speciation in birds such as the South American Andes, populations shift up and down the mountain range

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11
Q

Dispersal/ peripatric/ founder effect examples

A

Archipelago and island bird colonisations dispered from mainland to isolated islands.

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12
Q

Example of sympatric speciation

A

Rhagoletis apple maggot fly, ancestor of the r. pomenella which layed eggs in fruit Hawthorn trees

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13
Q

Whats more common than sympatric speciation

A

Parapatric

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14
Q

Examples of parapatric speciation

A

Lizards at the white sands

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15
Q

What can ecological speciation be defined as

A

The evolution of reproductive isolation between populations as a result of ecologically based divergent natural selection

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16
Q

An example of ecological divergence

A

Monkey flowers (mimulus)

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17
Q

Whats sexual selection defined as

A

Differential reproduction as a result of variation in the ability to obtain mates

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18
Q

Why does sexual selection vary across populations

A

To improve conspecific recongition
To provide optimal direct benefits to mates
As a result of pleiotrophic effects
Because of variation in good gene mechanisms
Because of runaway mechanisms when trait and preference alleles become genetically linked

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19
Q

What does higher taxa refer to

A

Any grouping above the species level for example genus or family

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20
Q

Whats another process that promotes speciation

A

Reinforcement

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21
Q

What is reinforcement defined as

A

The evolution of enhanced reproductive isolation between populations due to natural selection for greater isolation

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22
Q

What needs to be low in order to reinforcement to occur

A

Hybrid fitness

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23
Q

What can reproductive character displacement be defined as

A

the accentuation of differences between sympatric populations from two species as a result of reproductive interactions between them

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24
Q

Example of reproductive character displacement

A

Ficedula fly catchers including pied flycatcher and the collared fly catcher, they look different in the area of sympatry

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25
Q

When does polyploidy occur

A

When chromosomes fail to segregate during meiosis

26
Q

How are tetraploids formed

A

From two individuals in the same species

27
Q

Whats allopolyploid

A

Duplication of chromosomes in hybrids between species

28
Q

What are the consequences of having more chromosomes than normal

A

Increase in the number of gene copies
Tetraploid individuals reproductively isolated from parental species
Unable to form any viable offspring

29
Q

How common is polyploidy in plants

A

15% in flowering plants and 31% in ferns

30
Q

Whats an example of polyploidy in plants

A

Tragogan goatsbeards.

31
Q

How can we prevent extinction in new polyploid species

A

Reduce sterile triploid offspring by self fertilisation, vegetative propogation and habitat segregation

32
Q

How can we capatilise on the advantages of polyploidy

A

Heterozygote advantage, extreme phenotypic traits, chance to access new fitness opitma in the adaptive landscape

33
Q

Whats allopolyploid a form of

A

Hybrid speciation

34
Q

Whats homoploid hybrid speciation

A

Speciation via hybridisation without change in chromosome (ploidy) number

35
Q

Example of homoploid hybrid speciation

A

Helianthus sunflowers

36
Q

Example of adaptive radiation

A

Cichild fish in Lake Victoria

37
Q

Whats random genetic drift

A

Random changes in frequencies of two or more alleles or genotypes within a population

38
Q

What are phenograms

A

Represent similarity or distance but may not represent historical relationships

39
Q

What are phylogenetic trees

A

Represent a hypothesis about historical relationships

40
Q

What are cladograms

A

Y axis has no meaning, only tells the relationship between species

41
Q

What are additive trees

A

Where the y axis tells us about the amount of evolutionary change, how much sequence change happens

42
Q

What are ultra-metric trees

A

Y axis means time

43
Q

What are fully bifurcated trees

A

Assumes all speciation events involve one ting splitting into two

44
Q

What are multifurcated trees

A

A node splits into more than two species/ branches

45
Q

How do we add a root to the tree

A

Add information for an outgroup

46
Q

Whats an outgroup

A

A taxon that we believe, a priori to be more distantly related to the focal species than they are to one another

47
Q

How do we estimate genetic distance

A

K = the proportion of nucleotide sites that are different

48
Q

What does UPGMA stand for

A

Unweighted pair group method with arithmetic mean

49
Q

What does the jukes cantor distance correlation show

A

The more evolutionary distance there is, the more likely theres more hits (lorgarthmic scaling)

50
Q

Examples of when Phylogenies are useful

A

To see if flying mammals died once or twice

51
Q

Limitations in phlyogenetic analysis

A

Trees are hypotheses:
scoring characters are hard
homoplasy is common
Acient events are hard to infer
Some lineages might be diverging too rapidly
Hybridisation can be a problem
Incomplete lineage sorting

52
Q

Phylogenetic imbalance definition

A

A difference in the number of descendent tips either side of a focal node

53
Q

What does the equal-rates Markov model show

A

The probabiltiy of speciation per unit time is constant across all lineages

54
Q

Whats lateral gene transfer defined as

A

The aquisition of genetic material from another organism without sexual reproduction

55
Q

Why is Alloterepopsis important

A

Because its the only known species with the C4 and non-C4 enzymes

56
Q

Why does Zambian accession have more LGT

A

Has a much greater rate of gains due to diverse habitiat

57
Q

how many genes are LGT

A

0.04%

58
Q

What factors drive differentiation

A

Speciation and extinction

59
Q

Why do speciation rates vary

A

The frequency of barriers/ factors that produce geographical isolation
The rate at which these isolated populations evolve isolating mechanisms
The degree of these ecological diversity offering vacant ecological niches to these newly arising species

60
Q

Whats the cycle of speciation

A
  1. the formation of geographical isolates
  2. acquisition of reproductive isolating mechanisms
  3. ecological differentation
  4. cycle begins again
61
Q

What factors might affect progress through speciation

A

Rate of geographic isolation, rate of reproductive isolating barriers, rate of ecological differentiation and co-existence

Biology (9 decks)

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