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Speciation Flashcards

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Biology 101 flashcards
1
Q

what are the three theories of what a species is?

A

morphological concept- species are a set of organisms that look similar
phylogenetic concept: species are the smallest sets of organisms that share a common ancestor
biological concept: species are groups of interbreeding populations which are reproductively isolated.

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2
Q

what is the bases of the biological concept of speciation?

A

individuals from the same species can all breed with each other a produce offspring of a similar fitness. however, when populations diverge genetically or morphologically, a reproductive barrier forms which prevents mating or prevents offspring from being viable. When this reproductive barrier forms, two species have formed as there can be no gene flow between the two populations

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3
Q

what are the pros of the biological concept of speciation?

A
  • it does not rely on morphology, it accounts for unviable interbreeding, it accounts for the greater genetic distance between species.
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4
Q

what are the cons of the biological concept of speciation?

A

it does not apply for asexual species
it does not consider temporary geographic barriers to reproduction
some hybridisation has been successful between species (75% success in ducks)

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5
Q

what is micro evolution?

A

the evolution within populations

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6
Q

what is macroevolution?

A

evolution between species.

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7
Q

what is anagenesis?

A

the evolution within a population (microevolution)

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8
Q

what is cladogenesis?

A

the splitting of lineages and speciation- macroevolution

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9
Q

what does the process of speciation depend on?

A

the lack of gene flow between populations

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10
Q

what is prezygotic isolation?

A
  • reproductive isolation that occurs before mating can occur- this can be if mating seasons do not coincide, if populations are unable to meet
  • or if animals can meet but their behaviour (sexual selection- different bird song) or genitals are not complimentary
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11
Q

what is allopatric speciation?

A

speciation that occurs when a population is slit and there is a physical barrier between them, preventing gene flow. This could be a river or a mountain. This can be subdivided into peripatric (one smaller population) as opposed to two equally large populations.

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12
Q

what does peripatric mean?

A

a small subpopulation becomes isolated

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13
Q

what is paraptric speciation?

A

when there is a gradient of ecological change across the residence of a population, this results in two species at each end of the environment with a hybrid area in the middle

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14
Q

what is sympatric speciation?

A

when two species coexist in the same area but are found in different microenvironments- their domains overlap

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15
Q

what is an example of allopatric speciation occurring in the sea?

A

during the formation of the bridge between north and south america- movement of tectonic plates formed the isthmus of panama. this caused sediment to build up and eventually the caribbean sea and the pacific was divided. this cause allopatric speciation of snappy shrimp. either side of the barrier there are sister species for each species which are very similar but can’t breed- these are the descendent of the original population that has divided.

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16
Q

what is an example of reproductive barriers caused by timing of life cycle events?

A

corals that spore right next to each but two hours apart will never fertilise each other, apple maggots time the emergence of the pupa in correlation with the fruiting of the hawthorn or the apple tree- this means if you are int he wrong place you will starve

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17
Q

what is an example of reproductive barriers caused by behavioural changes?

A
  • the monkey flower has diverged in the mating signals that it transmits to pollenisers: the red flowers attract hummingbirds but the pink flowers attract insects therefore cross pollination will never occur between species.
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18
Q

what is an example of mechanical reproductive barriers? (2)

A

female genitilia co evolve within the species, if genitaia sizes different between species then they won’t cooperate with each other this is seen in carobs beetles who have intricate genitals.
it can also occur after mating: when the proteins on the sperm are not complimentary to the egg membrane so can’t fertilise

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19
Q

how can genetic reproductive barriers occur?

A

drift or selection can cause incompatible chromosomes or genes on each chromosome- this can as a result of macromutations which prevent the pairing of chromosomes or fusion: mice in the madeira

20
Q

how do mice in madeira show genetic reproductive barriers?

A

they are size different chromosome races found in mice in madeira, the sets vary in number and the chromosomes vary in size. this can negatively impact mitosis and meiosis, particularly if the numbers of unequal as meiosis needs aired chromosomes

21
Q

what is the dobzhansky muller incompatibilities of how genetic reproductive barriers can occur?

A

first there is the common ancestor which is wildtype homozygous for two proteins that interact with each other once transcribed. then a barrier spilts two subpopulations. in one population a mutation at the A locus occurs to a, however AaBb proteins can still interact. in the other lineage AABb occurs through a mutation at the B locus but these proteins can also interact fine.
the problem arises when these two populations try to breed- they will be AaBb, these proteins, due to the mutations have never interacted previously and do not interact very well so the hybrid organism is either dead or has a lower fitness (sterile)
this is the leading model for post zygotic mechanisms of reproductive isolation

22
Q

what is haldanes rule and how does this relate to reproductive barriers?

A
  • Haldane’s rule: when one sex is inviable, that sex is the heterogametic sex- Males in mammals- XY and females in birds and insects: this due to sex linked recessive genes acting epistatically in hybrids. This theory assumes that most alleles causng hyrbid sterility and inviability are recessive. because the sex chromosomes are heterogametic in one sex, sterility or inviability is predicted for the het sex of the F1 hybrids. In each species, these alleles evole adaptively in response to selection pressures within their own species. an allele that evolves in species A must coevolve with epistatic loci in its own species - it is not expressed in its own species but when placed with the chromosome from the other species, it does not have these epitstatic interactions and so causes inviability
    this shows how reproductive barriers can form due to the interaction of sex chromosome alleles
23
Q

what is the form of selection behind sympatric speciation?

A

under dominance- heterozygous disadvantage

24
Q

how can an insect example be used to explain how sympatric speciation may occur? how can this be related to an example learnt in the course.

A

if there is an insect population that feeds on 2 plants, sympatric speciation will occurs as the population tries to adapt the defence mechanisms of each plant- resulting in one becoming specialised for each type- this can be seen in black bellied seed crackers- two forms of beak size . however the bbsc interbreed.

25
Q

describe with an example of insects, how sympatric speciation can occur. what animal does this relate to

A

wo loci insect model: carriers of B1 prefer plant 1 and carriers of B2 prefer plant 2.another locus: A1 is primed for eating plant 1 and A2 is primed for eating plant 2. assume that insects mate on plants. in this examples optimums are A1A1B1B1 and A2A2B2B2. if there are any mixtures of this then individuals will be attracted to a plant that they their offsrping will survive poorly on and they will be selected against. therefore selection will favour divergent gene combinations and promotes linkage disequilbrium- apple maggots- the two alleles= rising time and olfactory preference of tree

26
Q

what are 3 examples of smypatric speciation?

A
  • apple maggots
  • chichilids
  • heliconius butterflies
27
Q

fully explain the example of the heliconius butterfly in sympatric speciation.

A

heliconius cydno and heliconius melpomene: these are sister species that diverged from sympatric speciation- one being adapted to areas of rainforest areas that are less covered and the other to darker more covered areas. this divergence in microhabitat along with larval host plant reduced gene flow. H. cydno is found in dark areas and h. melpomene in light areas. in each area the selection pressure oppose each other therefore homozygosity for either light or dark patterning would have been selected for. The hybrid between the two causes an intermediate offspring which is not camouflaged in either surrounding and is therefore attacked by predators. this iscalled reinforcement. Due to its low number, predators also dont knwo to avoid it so further selected against. this was shown by an expeirment. Due to the correlation between wing colour and mate choice, population preference is high, further prevent gene flow between species.

28
Q

how was the population preference in heliconius butterflies shown?

A

comparing the mating prefernce of polymorphic morphs of 1 species to two races of 1 species, to two parapatric species to two sympatric species. as you increase divergene the mating prefence for each inidivudals own species increases- shows mating prference increases with divergence

29
Q

what greatly supported the symatric speciation of the heliconius butterflies and why?

A

they mimic other poisonous species so that the greater in number they are, the more predators learn to avoid them- they need to look like their mimic partner so selected to look like them

30
Q

why is sympatric speciation hard to identify?

A

because can appear to sympatric but may in fact be allopatric- this can be seen in the apple maggot

31
Q

how does the apple maggot show that sympatric speciation is hard to identify?

A
  • an apple preferring species was found in mexico. also found that the preference for apple increased you moved more south. this could be accounted for by sympatric: he varying alleles for both apple and hawthorn perfence were present in the most recent common ancestor of the mexican and america species. The apple alleles became fixed in the mexican population but both persisted in the U.S. until a ecological situation arose which favoured the apple traits, this would be an example of sympatric
    or allopatric: it could also be a result of allopatric divergence in which the gene flow from the mexican apple fly were injected into the hawthorn population of the US and resulted in genetic variation that facilitated in the divergence later on in apple and hawthorn.
32
Q

what is the sympatric explanation for the presence of apple preferring species of apple maggot in mexico?

A

he varying alleles for both apple and hawthorn perfence were present in the most recent common ancestor of the mexican and america species. The apple alleles became fixed in the mexican population but both persisted in the U.S. until a ecological situation arose which favoured the apple traits, this would be an example of sympatric

33
Q

what is the sympatric explanation for the presence of apple preferring species of apple maggot in mexico?

A

it could also be a result of allopatric divergence in which the gene flow from the mexican apple fly were injected into the hawthorn population of the US and resulted in genetic variation that facilitated in the divergence later on in apple and hawthorn.

34
Q

how do apple maggots find their specialised tree?

A

they have an olfactory specilisation which determines their preference

35
Q

how do hawthorn and apple, apple maggots vary in reproductive cycle?

A

the pupa hatch to their corresponding fruiting cycles of the trees- apples fruits a few weeks earlier- they mate on the plant.

36
Q

what colours o the Heliconius cydno and melpomene butterlfies?

A

kind are black and melpomene are white

37
Q

explain the chichilid example of sympatric speciation:

A

chichilids have been found in multiple lakes in africa- there are two species- the larger surface feeding species and the smaller bottom feeding species. These are thought to have diverged from sympatric speciation- being gradually reproductively separated first by feeding preference and then by mechanics- difference in sizes.

38
Q

how is sexual selection involved in speciation? give an example

A

divergence in male traits and female preference could result in speciation through reproductive barriers via behaviour: if this is true then different species of hummingbirds will have different male songs and female preference. this was proved by showing that a population of bucscricket frog from the med had a different call from those in the pyrenees and that females preferred their relative song- this means the two populations would be able to breed cause not attracted

39
Q

what is the basic principle of sexual selection of speciation?

A

Genetically-based changes to these aspects of mating could complete the process of reproductive isolation and speciation. For example, bowerbirds (shown below) construct elaborate bowers and decorate them with different colors in order to woo females. If two incipient species evolved differences in this mating ritual, it might permanently isolate them and complete the process of speciation.

40
Q

what are 9 ways in which isolation can occur

A
  • Geographic
  • Ecological/temporal
  • Behavioural
  • Mechanical
  • Hybrid inviability
  • Gametic incompatibility
  • Hybrid sterility
  • Ecological mismatch
  • Mate choice
41
Q

how is drift involved in speciation?

A

by chance one population may fix an allele. by drift mutations can occur in different populations and different alleles will be fixed. this means that there may be genetic incompatibility in hybrid

42
Q

what is the name of the theory that predicts hybrids will be infertile due to incompatible different loci

A

dobzhansky muller incompatibility theory

43
Q

what animal shows how sexual selection can influence

A

bushcrickets

44
Q

where are bush crickets found?

A

the Pyrenees

45
Q

what are the animals that have shown the problems of genetic incompatibility and where are they found?

A

mice in madeira- 6 different genetic populations

Genetics (14 decks)

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