AS Biology Unit 2

AS AQA Biology Genetic Diversity and Classification

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  • Created by: Kaimlee
  • Created on: 13-03-11 10:52

Genetic Bottlenecks

A random reduction in a population size of a species lessing there genetic diversity meaning their are fewer alleles that will be passed on from generations. Making it less likely the population will adapt to changes in their environment.

Caused by a chance event such as a natural disater i.e. a volcanic eruption

Q1.) Explain how genetic bottlenecks reduce genetic diversity?

Q2.) What causes the genetic bottleneck effect?

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Exam Questions

Q3.) What does this drop in the population result in?

Q4.) Why does less alleles within a population cause a problem?

Q5.) Define what is meant by the term genetic bottleneck?

Q6.) If there was an increase in the variety of the alleles within a population would this cause an increase or decrease in the genetic diversity?

Q7.) What is meant by the term genetic diversity?

Q8.) What is meant by the ecological term population?

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The Founder Effect

Few individuals from a population inhabit a new area of land, because there are only a few members of the population the alleles they carry are not representative of the whole population so their offspring will be less genetically diverse than the whole population of the species.

This allows evolution & adaptation to occur because a portion of the population settles there are no competitors.

Charles Darwin: Finches according to their home island had different beaks that they had formed to adapt to their environment to help them survive.

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Exam Questions

Q1.) What effect does the founder effect have on a populations genetic diversity?

Q2.) How would you expect the founder effect to influence genetic diversity? and explain why?

Q3.) Explain how the founder effect can cause evolution and adaption to an environment to occur?

Q4.) Charles Darwin observed that finches living on different islands had different shaped beaks, explain why?

Q5.) What is the founder effect?

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Selective Breeding

Individuals with desired characteristics are choosen and used to produce offspring with the same desired characteristics.

Alleles for unwanted characteristics are removed from the population, therefore the population is less genetically diverse - limited alleles avaliable. Used in farming and domestic animals - produce a high yelid

Ethical issues: interfering with nature - accelerating evolution animal rights?, less resistant to illness. ADV - reliable high yield food source to feed growing population + famine.

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Exam Questions

Q1.) What is selective breeding?

Q2.) What effect does selective breeding have on genetic diversity? explain how?

Q3.) Some people are against selective breeding give 2 reasons why?

Q4.) Give an advantage to selective breeding?

Q5.) What is meant by genetic drift?

Q6.) Outline issues surrounding selective breeding?

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What is a species?

- Similar in appearance, behaviour and biochemistry

- Organisms from the same species can breed together to produce fertile offspring

- Share a common ancestor (evolutionary history)

Structure of Classification:

Kingdom, Phylum, Class, Order, Family, Genus, Species

(king peter's crouch overexicits for great sex) LOOOOL

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Exam Questions

Q1.) Name 3 peices of evidence that would suggest that 3 armadillos belong to different species?

Q2.) Fill in the gaps? Kingdom, ......, Class, Order, .......,......, Species

Q3.) Why it is hard to classify organisms as 1 species?

Q4.) Scientists studied two species of North American seahorse. They thought that these
two species are closely related. Describe how comparisons of biological molecules in
these two species could be used to find out if they are closely related.

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Phylogenies - are family trees representing true evolutionary relationships, rather than just convenient groups.

Method 1 - Using DNA

Sequence the entire genome of the organism compare the DNA sequence

- Takes a very long time to sequence

Method 2 - alternative sequences a small number of genes and just these.

- takes less time, but less accurate

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DNA Hybridisation

Method 3 - Uses large portions of DNA from an organism

- more reliable + quicker

Heat the DNA (to break hydrogen bonds) - strands seperate ---> cool DNA

Some hydrogen bonds form again, but some dont because bases dont match (mismatch regions)

Heat again slowly, measure the amount of single strands every 2oC - the temperature of which they seperate = there simiarlity. High B.P - v.simular Low B.P - not simular

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Exam Questions

Q1.) Explain how DNA hybridisation can give a measure of genetic relatedness between species?

Q2.) Why is molecular evidence more accurate for correctly classifying pants or animals than morphological?

Q3.) Comparing the base sequence of a gene provides more information than comparing amino acid sequence for which the gene codes explain why?

Q4.) Discuss methods of classification using DNA?

Q5.) What are the disadvantages of these methods?

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Comparison of amino acid sequence in proteins

Protein sequences are determined by DNA sequence (triplet code) We can compare amino acid sequences to draw phylogenies

- but the proteins are hard to sequence

Immunology Comparisons of Proteins:

Allows us to compare simularities between species without sequencing the protein.

Antibodies of 1 species will respond to specific antigens on proteins, the fewer simular antigens less precipitate.

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Courtship Behaviour

It is important because reproduction is necessary if a species is to survive a long time.

maximises the chance of the species survival

- recognising members of their own species - so produces fertile offspring

- identify a mate that is capable of breeding -both sexually mature/fertile

- form a pair bond - successful raising of the offspring

- synchronise mating - max.probability sperm/egg meet

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Exam Questions

Q1.) Explain why courtship song is an important part of species recognition in mole crickets?

Q2.) Why is courtship behaviour important?

Q3.) What is meant by courtship behaviour?

Q4.) The scientists produced hybrids between the two crickets by fertilising eggs from one species with sperms from the other. The male hybrids had songs that had some features of one parent species and some features of the other. Suggest why the male hybrids were not able to reproduce?

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where are the answers for the exam questins???

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