Brainscape's Knowledge GenomeTM

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


See full index

Sem 2: Evolutionary biology > Week 8 > Flashcards

Week 8 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is speciation?

A

‘Evolution of reproductive isolation within an ancestral species, resulting in two or more descendant species.’

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

What is anagenesis?

A

Anagenesis is the gradual evolution of a species that continues to exist as an interbreeding population

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

What is cladogenesis?

A

Cladogenesis occurs when there is branching or splitting, leading to two or more lineages and resulting in separate species

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

Why is speciation important?

A

Speciation generates biodiversity
But note that much diversity exists within species as well, and may itself contribute to speciation
Speciation events in very distant evolutionary past generate higher-level branches (e.g. phyla)
Study of speciation illuminates role of genetic processes and natural selection in evolution

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

What are the 3 methods for demonstrating species existance?

A

Common sense
Folk
Statistical methods

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

What is an overview of the common sense argument

A

Species are real because everyone recognizes they are real.
Nobody claims a continuum between crows and eagles

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

Does the common sense argument prove species are real?

A

Common sense argument does not provide hard evidence for existence of species.
Humans separate the continuous spectrum of light into 7 distinct colours - propensity to divide a continuous array of organisms into discrete units?

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

How can you compare Folk vs Linnaean?

A

Survey a regions indigenous peoples and compare lists of animal and plant types with Linnaean species.
One to one correspondence. - evidence for reality of species.
Folk species are under-differentiated – 2 or more Linnean species per folk species. - evidence for reality of species if untrained observers cannot tell cryptic species apart
Folk species are over-differentiated - evidence against the reality of species

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

What are examples of Folk vs Linnean?

A

Remarkable concordance between folk and Linnean species
Mayr 1963 - F136 vs L137 species, 99% correspondance, birds, New Guinea Arfak tribesmen

Majnep & Bulmer 1977 - F123 vs L176, 70-80% correspondance, Birds, New Guinea Kalam people

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

Is the folk arguemtn covincing?

A

All humans have same visual system.
Do animals recognise the same species as we do? e.g. Mates or pollinators

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

If we use statistical tools do we see sympatric organisms falling into distinct clusters?

A

Could use morphology, behaviour, molecular characteristics.
Statistical methods will not identify clusters if they don’t exist

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

What are the use of using genetics to identify species?

A

DNA barcoding typically identifies > 3% divergence between species, but < 1% within species.
In 260 bird species COI variation between species averaged 7.93%, whereas variation within species averaged 0.43% (Herbert 2004)

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

What is the aim of the concept of species?

A

Helps with systematic classification
Corresponds to discrete entities we see in nature.
Helps understanding of how species arise
Represents evolutionary history of organisms
Applies to largest possible number of organisms

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

What is the biological species concept?

A

Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups

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

What is the morphological species concept?

A

A lineage judged to be evolutionarily independent on the basis of size, shape or other morphological features

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

What is the phylogenetic species concept?

A

A species is the smallest monophyletic group of common ancestry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the genotypic cluster species concept?

A

Species are groups that remain recognizable in sympatry because of the morphological and genotypic gaps between them (Mallet 1995)

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

What are the pros of the morphological species concept?

A

Widely applicable - used for asexual organisms and extinct fossilised species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the cons of the morphological species concept?

A

Can be arbitrary and subjective
Some groups may subdivided into species that differ little or not at all in morphology (cryptic species)

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

What is an example of a crypic species?

A

Previous single species now recognised as two: Common Pipistrelle (Pipistrelle pipistrellus) and Soprano Pipistrelle (P. pygmaeus)
Two forms with differences in frequency of calls identified by differences in mitochondrial DNA (11% divergence)

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

What are the pros of biological species concept?

A

Stresses genetic independance of species (total lack of gene flow)
Interbreeding can be tested
Widely adopted, legal definition in the USA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the cons of biological species concept?

A

Can’t be applied to asexual organisms and fossils
In practice, testing for interbreeding can be difficult
Reproductive isolation is not an all or nothing trait

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

What is an example testing the biological species concept?

A

Closely related alloptaric ‘forms’
Incipient species
No postzygotic isolation
Out of 1955 offspring genotyped, 1296 (66.3%) were sired by the male from the same population as the female.
More than three times the rate expected if females do not differentiate among males of the five different populations (20%)

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

What is an example fo incomplete reproductive isolation?

A

Greenish Warbler (Phylloscopus trochiloides) (Irwin et al. 2005 Science)
Northern forms (viridanus and plumbeitarsus) do not interbreed (and have distinct songs and plumages and are distinct genetically), southern forms do interbreed (and have less distinct songs and plumages and are less distinct genetically)

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

What is an example of geographical hybridisation in non-ring species?

A

Spotted Towhee (Pipilo maculatus) and Collared Towhee (P. ocai)
Hybridise some areas where they co-occur but not in others

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

What are the pros of the phylogenetic species concept?

A

Uses increasing phylogenetic data
Seperateness in a phylogeny reflects genetic isolation
Widely application, can be used for asexual and extinct organisms

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

What are are the cons for phylogenetic species concept?

A

Robst phylogeny not always avaliable. especially phylogeny
Not clear what characters should be used to contrust phylogeny
Doesnt lead to stable systematics, since phylogenies change as new data emerge

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

What is an example of the application of phylogenetic species concept?

A

Forest Elephant (Loxodonta cyclotis) v. Savannah Elephant (L. africana): Forest Elephant is smaller (2.5m high v. 3-4m high) and has straighter, thinner tusks, rounder ears and differently-shaped skull
Phylogeny based on 4 nuclear genes
Forest v. Savannah Elephants show 58% of difference shown between African and Asian Elephants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What are the pros of genotypic cluster species concept?

A

Combines elements of previous definitions
Operational definition, aims to seperate definition of species from hypotheseses about how speciation occurs
Does not assume complete reproductive isolation is required to define a species

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

What are the cons of genotypic cluster species concept?

A

Element of subjectivity remains
Not widely used

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

What is an example of a species created by hybridisation?

A

Heliconius cydno and Heliconius melpomene crossed in laboratory to re-create Heliconius heurippa
H. heurippa:
Occurs in nature (in Colombia)
Does not breed with putative parent species
Hybrid genome

32
Q

What is an example of different species concept coming to a different conclusion?

A

Under MSC, Red Wolf is a species
Under BSC, it is not a species as it hybridises with the Coyote
Phylogenetic SC - suggests red wolves result from hybrids between the Gray Wolf and the Coyote!

33
Q

What is an example of speciation in a lab with Drosophila?

A

Fruitfly Drosophila pseudoobscura
4 reared on starch-based medium and 4 reared on maltose-based medium
2 groups became differentially adapted to media
1 year after start, mating experiments performed

34
Q

What were the results of fruitflies speciation?

A

Positive assortative mating: individuals from each group prefer to mate with opposite sex from same group, even across cages
Reproductive isolation as a by-product of adaptation to media (not separation per se).

35
Q

What is an example of speciation in a lab with Polychaete worm?

A

Polychaete worm Nereis acuminata
Lab population founded in 1964 from 5-6 individuals, grew to 1000s, 4 pairs selected in 1986, new population grew to 1000s (two ‘bottlenecks’)
Test against field populations for pre-mating and post-mating isolation

36
Q

What were the results of speciation in a lab of Polychaete worm?

A

Pre-mating: In Lab-Field crosses, worms more reluctant to mate than in Lab-Lab or Field-Field crosses
Post-mating: In Lab-Field crosses, 0% offspring survived; in Lab-Lab or Field-Field crosses, 75-95% offspring survived Reproductive isolation (with hybrid sterility) as a by-product of bottlenecking and/or adaptation to lab environment

37
Q

What are isolating barriers?

A

Any intrinsic process or phenomenon that forms a barrier to gene flow between populations but excludes (large-scale) physical separation per se

38
Q

What are the two types of mating barriers?

A

Premating barriers: by-products or products of selection for avoidance of hybridisation (reinforcement), if populations have hybridised in the past and hybrids have reduced fitness
Postmating barriers: by-products, since, for example, cannot be selection for greater degree of sterility in hybrids

39
Q

What is an example of temporal ecological isolation (pre)?

A

Bishop Pine (Pinus muricata) v. Monterey Pine (P. radiata) in California: former sheds pollen late in year, latter early in year, so do not cross although can be made to hybridise

40
Q

What is an example of habitat ecological isolation (pre)?

A

Dixie Iris (Iris hexagona) v. Copper Iris (Iris fulva) in SE USA: hybridise where habitats meet in Louisiana

41
Q

What is an example of behavioural isolation in animals (pre)?

A

Field Grasshopper (Chorthippus brunneus) and relatives (C. biguttulus and C. mollis) look very similar but have different male songs: interspecific matings occur if ‘right’ song is played in laboratory; plus Fireflies: females respond only to male flash pattern of their own species

42
Q

What is an example of behavioural isolation in plants (pre)?

A

Congeneric monkeyflowers (Mimulus lewisii and M. cardinalis) differ in floral form and hence in pollinators (bees v. hummingbirds)

43
Q

What is an example of mechanical mismatch/copulatory failure (post)?

A

Damselflies, males clasp females across the thorax; female inserts tip of abdomen into underside of midbody of male to pick up spermatophore that male has placed there; there is fine match of these structures – any mismatch makes the copulation unsuccessful

44
Q

What is an example of gametic incompatibility failure (post)?

A

Sea-urchins and abalones, only conspecific fertilisation occurs because biochemical compatibility gametes required in abalone, there is a species-specific relationship between lysine in sperm head and vitelline envelope surrounding egg)

45
Q

What is an example of prezygotic reproductive isolation in Drosophila?

A

Allopatric taxa - increase in genetic difference means greater prezygotic isolation
Sympatric taxa - small genetic difference can mean total prezygotic isolation

46
Q

What are an example of postzygotic hybrid zygote reducing fitness in amphibians?

A

Hybrid inviability: hybrid embryos die during development, e.g. Wood Frog (Rana sylvatica) x Leopard Frog (R. pipiens)

47
Q

What are an example of postzygotic hybrid zygote reducing fitness in mammals?

A

Hybrid sterility: e.g. a mule is a (viable) hybrid between Horse (Equus caballus) and Donkey (E. asinus) but is sterile owing to unequal chromosome numbers (Horse: 2n = 64; Donkey: 2n = 62)

48
Q

What are an example of postzygotic hybrid zygote reducing fitness in insects?

A

Cytotypes of grasshopper Caledia captiva in Australia: in hybrid zone, F1 hybrids are common but F2 hybrids are rare (because die during embryonic development)

49
Q

What are an example of postzygotic hybrid zygote reducing fitness in fish?

A

Fitness of F2 hybrids of African haplochromine cichlid fish bred from species pairs spanning several thousand to several million years divergence time. F2 hybrids consistently showed the lowest viability compared to F1 hybrids and non-hybrid crosses

50
Q

What is an example of post zygotic isolation?

A

Hybridisation of Heliconius melpomene and H.cydno
Hybrids are attacked by birds at a much higher rate then either of the parent species

51
Q

What is an overview of apple maggot fly?

A

Rhagoletic pomonella
Invest hawthorn vs apple, 150 years ago
Differ in six allozyme loci

52
Q

What are the overviews of the zygotc isolation of Apple maggot fly?

A

Pre - host plant fidelity and allochronic isolation (apples ripen earlier)
Post - no intrinsic inviability/sterility of hybrids expect ecological isolation from host-specific adaptation

53
Q

Are there multiple barriers for Apple maggot fly?

A

Hawthron is better food for both races
Apples do have less interspecific competition, less parasites and lower population density
Fitness maybe similar but not enough to cuase isolation

54
Q

What is the cause between the speciation of the Apple maggot fly?

A

Hawthron race developes fast and Apple race is slow
Pupae overwinter but diapause is faculative
Apples avaiable 3 weeks earlier and apple race pupates 16 days earlier
Fast development on apples - breaks diapause before winter dies
Slow development on hawthorn - not ready to enter diapause by winter
Hybrid impactes development speed so either too fast or slow

55
Q

What is the hybrid zone?

A

Region where genetically distinct populations meet and mate, resulting in at least some offspring of mixed ancestry

56
Q

What is the primary hybrid zone?

A

Population genetic differentiation correlated with environmental discontinuities (with hybrid zones along these discontinuities)

57
Q

What is the secondary hybrid zone?

A

Two formerly separate populations expand, meet and interbreed, but do not necessarily merge

58
Q

What is an example of a hybrid zone?

A

Yellow-bellied Toad (Bombina variegata) of western Europe, Fire-bellied Toad (B. bombina) of eastern Europe
Ranges contact in narrow (6km wide ) hybrid zone in central Europe
Hybrids have lower rates of survival (= postzygotic isolating barrier)
Ancestors confined to refuges in southern Europe in Pleistocene glacial period
Secondary contact on spread from refuges in SW and SE Europe, respectively

59
Q

What maintains stability of hybrid zone?

A

Balance of dispersal and degree of hybridisation - bringing about gene flow - and selection against hybrids - preventing gene flow

60
Q

What is the mechanism of the hybrid zone?

A

Two populations fixed at a locus for alleles A and a (hence populations are AA and aa)
Dispersal of AA individual into aa range, followed by mating, creates Aa hybrid; mating of this F1 hybrid with aa individual introduces A into aa population (introgression)
But if Aa hybrids are less fit (postzygotic isolating mechanism), then introgression does not occur or occurs rarely
Hence steepness of cline determined by balance of amount of gene flow and strength of selection against hybrids

61
Q

What are the fate of hybrid zones?

A

Lower than parental fitness have a relatively narrow and short lived hybrid zone and increase in reinforcement of parental populations
Equal to parental fitness have a relatively wide and long lived hybrid zone and parental populations coalesce
Higher than parental fitness depends on fitness advantage occurs in ecotone or new habitat ends with stable hybrid zone or formation of a new species

62
Q

What are the modes of speciation?

A

Allopatric speciation (geographically separated populations become reproductively isolated)
Parapatric speciation (geographically neighbouring populations become reproductively isolated)
Sympatric speciation (geographically overlapping populations become reproductively isolated)

63
Q

What are the sub forms of allopatric speciation?

A

Vicariance (an existing population is subdivided into one or more smaller populations)
Peripatric speciation (a larger parental population gives rise to a smaller population at its periphery, by subdivision or by dispersal)

64
Q

What can cause allopatric speciation?

A

Land bridges
Glaciation
Mountain formation
Continental drift
Climatic change
Barrier prevents (or severely reduces) gene flow.
Most common mode of speciation in animals

65
Q

What are an example of allopatric speciation?

A

Current Isthmus closed 3 million years ago – developing long before that.
Different sides of the Isthmus experience different environmental conditions – salinity, clarity, temperature, tidal fluctuations.
Upwelling-driven, plankton-based ecosystem on the Pacific side and a coral-reef-based, clear-water ecosystem in the Caribbean
Lots of taxa are different on each side of the Isthmus.

66
Q

What is an example of allopatric speciation across Isthmus of Panama?

A

16 taxa (eight putative geminate species pairs) within the genus Alpheus.
Strong reproductive isolation between species pairs in Lab
1% of interspecific matings yield fertile offspring vs 60% of conspecific
Molecular clocks indicate species pairs did not all diverge at the same time – range of dates from 3mya to 10mya

67
Q

What is the relationship between compatibility and genetic distance?

A

Reproductive compatibility is correlated with genetic distance, low reproductive compatibility is correlatied with genetic divergence

68
Q

What is peripatric speciation?

A

Same mechanism as allopatric speciation except that the isolated population is very small (1 to 100 individuals).
May involve invasion of new habitats
Genetic drift becomes important in small populations.

69
Q

Why might perpatric speciation occur?

A

Founder events
Isolation of peripheral population.
Non-peripheral population could become isolated from rest (rare?).

70
Q

What is the model of perapatric speciation?

A

Reproductive isolation evolves between two populations that are exchanging some genes.
“Clinal models” involve a single species distributed across a variable environment.
Subpopulations become adapted to their local environments
“Stepping stone” models involve discrete populations having limited genetic exchange.

71
Q

What is an overview of sympatric speciation?

A

New species form within a freely interbreeding population
“the origin of an isolating mechanism (i.e. a barrier to gene flow) among the members of an interbreeding population”
Should evolve within the average dispersal distance of a single individual
Not caused by geography or distance but be some biological feature of organisms
Remains controversial and is probably quite rare if it does occur

72
Q

What 4 criteria are used to support sympatric speciation?

A

1- The species must be largely or completely sympatric. Although presently allopatric species may have arisen in sympatry, this will usually be impossible to determine.
2- The species must have substantial reproductive isolation, preferably based on genetic differences.
3- The sympatric taxa must be sister groups. The genetic similarity used to establish this fact must not result from hybridisation.
4- The biogeographic and evolutionary history of the groups must make the existence of an allopatric phase very unlikely.

73
Q

What is a case study for sympatric speciation?

A

Cichlid fish
Small conical lakes that are isolated
11 spp in lake Barombi Mbo and 9 spp in lake Bermin, all species are endemic
Species differ in diet feeding morphology and breeding colouration
No hybrids found

74
Q

What is evidence of Cichild fish in Lake Barombi Mbo and lake Bermin?

A

The “monophyly” (descent from a common ancestor) of the two radiations shown above is weaker than previously thought.
The authors conclude that this monophyly, which is crucial evidence for sympatric speciation, is not strongly supported

75
Q

What is the new suggested mechanism for the presence of the Cichild in Lake Barombi Mbo and lake Bermin?

A

Substantial introgression (movement of genes) between not only some of the species in each of the two radiations, but also between the species in the lake and different “outgroup” species in rivers outside the lakes.
This suggests that there have been multiple invasions of the lakes by ancestors of the crater-lake fish, and this again militates against a single common ancestor forming multiple species in the lake

76
Q

What is the overview of speciation on Lord Howe Island?

A

The native flora of LHI comprises 242 species in 179 genera.
In 139 genera only a single species is present on LHI; of these species, 42 are endemic to the island
The remaining 40 genera include between two and six LHI species.
In 13 cases, all species are endemic; in 15, all are non-endemic; and the remaining 12 genera contain a mixture of endemic and non-endemic species

77
Q

What was the breakdown of the speciaiton of flora on Lord Howe Island?

A

When modeled
55.4% of trees arrived by colonisation
24.8% of cases by Allopatric speciation
Sympatric speciation depending on strength of cases was either 3.7% or 4.5%

Sem 2: Evolutionary biology (11 decks)

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