Speciations final

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  • Created by: Hindleyc
  • Created on: 31-03-19 14:48
What is evolution
change in allele frequency of a population
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what is the origin of a new species
speciation
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What does evolution by natural selection not always give rise to
new species though they do illustrate change
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what did the 100 million species that do and have existed arose by
evolution
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What has E changes over a long period of time resulted in
great diversity of species
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What is speciation
Evolution of new species from existing species
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What do species belong to
same gene pool (similar characteristics and bred to produce fertile viable offspring)
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How do new species arise
When 1 existing species splits into 2 reproductively isolated populations that go their separate ways
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What can reproductive isolation result in
accumulation of differences in their gene pools
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What may differ
environmental conditions that each group encounters
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What will selection do
affect 2 populations in different ways and so the type and freq of ales in each will change so each population will evolve along separate lines
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In time what will the gene pools of the 2 populations may become
so different that even if reunited they would be incapable of breeding with each other - have become separate species each with its own gene pool
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So how have new species arisen
when these genetic differences lead to an inability of members of the population to interbreed and produce fertile offspring in this way new species arise from existing species
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What is most common
when 2 populations become physically separated from each other
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2 forms of speciation
geographical isolation (allopatric) and sympatric
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Steps of geographical isolation
Interbreeding population of one species, population becomes divided by a physical barrier such as water, mountains desert or large distance eg when some of population migrates or is dispersed or when the geography changes catastrophically eg earthqua
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how else can it occur
gradually eg erosion continental drift
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What if E (abiotic/ biotic) are diff in the 2 places (common)
then the 2 populations will evolve differently
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Even if the E are similar what may the population still do
change by rando genetic drift especially if population is small
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Much later if the barrier is now removed and the 2 populations meet again what happens
They are now so different they can no longer interbreed therefore remain reproductively isolated and are 2 distinct species- may both be different from the original species if it still exists elsewhere
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What may natural selection and isolation result in
change in the allele and phenotype freq and lead to formation of a new species
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What is sympatric speciation
Means same country and describes the form of speciation that results within a population in the same area leading them to becoming reproductively separated
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eg
fruit fly
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Why is it meaningless to say that 1 species is absolutely better than another species
it is only better adapted to that particular environment
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What may a species be
well adapted to its environment
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but if the environment changes
then the species must evolve or die
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in either case the original species will become?
extinct because all environments change eventually so the fate of all species to become extinct (including our own)
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Who can experience random genetic drift
small colonising populations
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what is it important in
causing changes in allele freq in some populations
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what is it
changes in the frequency of particular allele in a population from generation to generation due to chance fluctuations
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What type of population is the effects of RGD more pronounced
small
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What can it result in
loss of some alleles (freq 0%) whilst others can become fixed (freq =100%)
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what is it important in
small
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What is genetic bottleneck
occurs when an event (eg a drastic environmental change)kills a significant percentage of a population/ species or prevent them from reproducing so that numbers are greatly reduced
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What does catastrophe allow
only a few individuals of a population to survive
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by chance what happens
shaking of bottle results in black beads being overrepresented in the 'surviving population' and the yellow beads absent
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similarly what do genetic bottlenecks result in
populations with reduced genetic diversity
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what is cause often and eg
environmental disasters are often the cause of a genetic bottleneck and flood killing random members of a population or rising sea levels forming new islands with small isolated populations
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cheetahs?
low G diversity
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why
result of 2 genetic bottlenecks, last ice age when climate changes disease or starvation causes a massive decline in the population, cheetahs were hunted to near extinction in the 19th century
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What is the founder effect
loss of genetic variation when a new colony is established by a very small number of individuals from a larger population
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What happens
colonisation by a small number of individuals
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consequences of the founder effect and genetic bottlenecks- both result in
reduced genetic diversity, increased rate of random genetic drift and increased interbreeding due to limited numbers of mates
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Card 2

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what is the origin of a new species

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speciation

Card 3

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What does evolution by natural selection not always give rise to

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Card 4

Front

what did the 100 million species that do and have existed arose by

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Card 5

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What has E changes over a long period of time resulted in

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