Speciation

Question 1

what are the three theories of what a species is?

Answer 1

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.

Question 2

what is the bases of the biological concept of speciation?

Answer 2

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

Question 3

what are the pros of the biological concept of speciation?

Answer 3

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

Question 4

what are the cons of the biological concept of speciation?

Answer 4

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)

Question 5

what is micro evolution?

Answer 5

the evolution within populations

Question 6

what is macroevolution?

Answer 6

evolution between species.

Question 7

what is anagenesis?

Answer 7

the evolution within a population (microevolution)

Question 8

what is cladogenesis?

Answer 8

the splitting of lineages and speciation- macroevolution

Question 9

what does the process of speciation depend on?

Answer 9

the lack of gene flow between populations

Question 10

what is prezygotic isolation?

Answer 10

• 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

Question 11

what is allopatric speciation?

Answer 11

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.

Question 12

what does peripatric mean?

Answer 12

a small subpopulation becomes isolated

Question 13

what is paraptric speciation?

Answer 13

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

Question 14

what is sympatric speciation?

Answer 14

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

Question 15

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

Answer 15

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.

Question 16

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

Answer 16

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

Question 17

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

Answer 17

• 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.

Question 18

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

Answer 18

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

Question 19

how can genetic reproductive barriers occur?

Answer 19

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

Question 20

how do mice in madeira show genetic reproductive barriers?

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

• 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

Question 23

what is the form of selection behind sympatric speciation?

Answer 23

under dominance- heterozygous disadvantage

Question 24

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.

Answer 24

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.

Question 25

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

Answer 25

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

Question 26

what are 3 examples of smypatric speciation?

Answer 26

- apple maggots - chichilids - heliconius butterflies

Question 27

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

Answer 27

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.

Question 28

how was the population preference in heliconius butterflies shown?

Answer 28

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

Question 29

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

Answer 29

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

Question 30

why is sympatric speciation hard to identify?

Answer 30

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

Question 31

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

Answer 31

- 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.

Question 32

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

Answer 32

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

Question 33

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

Answer 33

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.

Question 34

how do apple maggots find their specialised tree?

Answer 34

they have an olfactory specilisation which determines their preference

Question 35

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

Answer 35

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

Question 36

what colours o the Heliconius cydno and melpomene butterlfies?

Answer 36

kind are black and melpomene are white

Question 37

explain the chichilid example of sympatric speciation:

Answer 37

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.

Question 38

how is sexual selection involved in speciation? give an example

Answer 38

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

Question 39

what is the basic principle of sexual selection of speciation?

Answer 39

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.

Question 40

what are 9 ways in which isolation can occur

Answer 40

- Geographic - Ecological/temporal - Behavioural - Mechanical - Hybrid inviability - Gametic incompatibility - Hybrid sterility - Ecological mismatch - Mate choice

Question 41

how is drift involved in speciation?

Answer 41

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

Question 42

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

Answer 42

dobzhansky muller incompatibility theory

Question 43

what animal shows how sexual selection can influence

Answer 43

bushcrickets

Question 44

where are bush crickets found?

Answer 44

the Pyrenees

Question 45

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

Answer 45

mice in madeira- 6 different genetic populations