A2 REAL -Populations and Evolution

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  • Created by: DonaJ2002
  • Created on: 30-01-20 06:22
Define and explain what species are
Group of individuals in one or many populations that can interbreed to produce fertile offspring
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Define a population
Group of the same species that live in a certain area at certain time can interbreed to produce fertile offspring
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Define gene pool
Complete range of alleles in population
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Define and explain the Hardy-Weinberg principle
Mathematical model that predicts the allele frequency in population won't change between generations; this is only true under certain conditions
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When can the Hardy-Weinberg principle be true and explain why?
Big population with 1.No emigration/ immigration(gene flow)= no new alleles intro/exit 2.No mutations=no new alleles made=no natural selection 3.No Natural select=no allele frequency change btw generations 4.Random mating=no preference for genotypes
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What are the 2 Hardy-Weinberg principles and state what they mean?
.
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How do you predict the genotype and phenotype in a population with Hardy-Weinberg?
Genotype found by using p^2+2pq+q^2=1 Phenotypes found by using genotype frequencies by working out genotypes you have and the total frequency then, rearrange and use p+q=1
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How do you predict percentage of population with certain genotype and state what to do if you need to find this for the carrier population?
If it says 1 in every 1000 has that genotype and the condition is recessive, then it'sq^2=1/1000 then to find q=square root then, p=1-q. If you need to find the percentage for the carrier population, after doing all that, do 2pq
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How can you show if external factors such as natural selection/ mutation/ emigration/ immigration/ random mating are affecting the allele frequency?
Do the calculations as per the question, then compare the answer you got to the allele frequency before, if it has changed then frequency has been affected by external factors.
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Why should there be a large population for Hardy-Weinberg?
Large population= unlikely to be affected by allele frequency change due to chance as chance changes is small compared to allele copies in big populations but in small populations there are fewer allele copies so, likely that chance changes occur
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Define variation
Difference between individuals
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What is the difference between inter and intraspecific variaition and how can you remember this?
''Inter''= between and ''Intra''= within so, interspecific variation is the difference between species
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Explain intraspecific variation and interspecific variation
Intraspecific variation is when population doesn't have a lot of different phenotypes as it's variation within a species but when it's interspecific variation then there is a wide range of different phenotypes as it's the variation between species
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Explain how genetic variation within species is caused
Individuals within a species have the same genes but have different alleles
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List and explain the main sources of genetic variation
1. Mutation that makes new alleles 2. During meiosis via crossing over and independent segregation 3. Random fertilisation of gametes during sexual reproduction 4. Environmental change (e.g. climate)
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What can genetic variation lead to?
Evolution
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Define evolution
Allele frequency change over TIME
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Which method does evolution occur by and explain how?
Natural selection:1. Members of same species have different alleles; selection pressures= hard to survive 2.Those with beneficial phenotype allele increases survival chances=reproduce+ pass advantageous allele to future generation=more in gene pool
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List the examples of selection pressures
Predation, competition, Disease
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Name the types of selection
1. Stabilising 2. Directional 3. Disruptive
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Define stabilising selection
The environment is stable and doesn't change therefore, those with advantageous alleles survive and reproduce and their population(breeding) range is in the middle
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Define directional selection
Environment chances= individuals with alleles for single extreme phenotype are more likely to survive and reproduce so, their population is on one side of the range of the total population=their curve shift to one side compared to total population
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Define and explain why disruptive selection occurs
Environment favours multiple phenotype= individuals with extreme phenotypeS are at both ends of range will survive and reproduce by NON-RANDOM Mating=2 breeding population= MIDDLE RANGE LOST= opposite to stabilising selection.
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How can you remember what stabilising, directional and disruptive selection are?
1.Stabilising=Stable environment= breeding population stable in middle 2.Directional= Environment's direction change= breeding population move to one direction of range 3.Disruptive= Environment change favours many extreme phenotype= disrupt range
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Why do you end up with 2 breeding population in disruptive selection?
Environment favours multiple extreme phenotypes= NON-random mating= small beaks x small beaks and big beaks x big beaks= 2 different breeding populations
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Define, describe and explain how speciation occurs
Development of new species from existing species when populations of the same species become reproductively isolated with/ without physical barrier= allele frequency changes = phenotypes change= CAN'T interbreed to produce fertile offspring
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Define polyploidy
Mutation leads to increase in chromosomes in a diploid organism (eukaryote)
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Which type of speciation occurs when population of the same are reproductively isolated without a physical barrier?
Sympatric speciation
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Which type of speciation occurs when populations of the same species are reproductively isolated with a physical barrier and state how you can remember the difference between the 2 types of speciation
Allopatric speciation- REMEMBER: Sympatric is isolated in a Simple way= NO Barrier BUT Allopatric is not simple= there is a barrier
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List 2 things that lead to change in allele frequencies in speciation topic
1. Allopatric speciation's difference in selection pressures 2. Genetic drift
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Besides the physical barrier, DESCRIBE+ EXPLAIN what else is different between allopatric and sympatric speciation?
Allopatric=physical barrier=reproductively isolated=both populations have different selection pressures=separated population normally in warm; NOW in cold get new advantageous alleles(long fur) via mutation=survive+reproduce=change allele frequency
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When the allele frequency changes in the separated population, in allopatric speciation, discuss what it could result to
Change in allele frequency= change in gene pool of separated population= change phenotype frequencies EVENTUALLY, the separated population change SO MUCH that they can't interbreed to produce fertile offspring= reproductively isolated + new species
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List the ways that reproductive isolation can occur without physical barriers (i.e. sympatric speciation)
1. Polyploidy 2. Seasonal 3. Mechanical 4. Behavioural
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Describe how polyploidy organisms sympatrically speciate
Polyploidy in a diploid population= polyploidy individual has different numbers of chromosomes can't reproduce sexually to give fertile offspring; if polyploidy asexually reproduce= new species BUT IT'S COMMON IN PLANTS
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Card 2

Front

Define a population

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Group of the same species that live in a certain area at certain time can interbreed to produce fertile offspring

Card 3

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Define gene pool

Back

Preview of the front of card 3

Card 4

Front

Define and explain the Hardy-Weinberg principle

Back

Preview of the front of card 4

Card 5

Front

When can the Hardy-Weinberg principle be true and explain why?

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Preview of the front of card 5
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