variation and evolution

• What are the twotypesof variation shown in individuals of the same species?

  
  

  
  

  Continuous and discontinuous
• HT:which type of variation has a bell curve shape

  
  

  Continuous variation

  
• HT:which type of variation has data split into discrete groups

  Discontinuous variation - the bars do not touch

  
• HT:is blood type an example of continuous or discontinuous variation

  Discontinuous

  Each blood type is a discrete group

  
• HT:is height or length in organisms an example of continuous or discontinuous variation

  
  

  Continuous

  Any height/length is possible between a range of values

  
• What are thecauses of variation between individuals of a species

  Environmental(e.g. diet and exercise) orgenetic
• What are the main features of sexual reproduction?

  Two parents

  Fertilisation of an egg by a sperm

  Offspring are genetically different to the parents
• What are the main features of asexual reproduction?

  One parent

  No fertilisation

  Offspring genetically identical to the parents (clones)
• What is the term given to offspring produced as a result of a sexual reproduction?

  Clones- they are genetically identical
• Why does sexual reproduction lead to

  geneticvariation within a species?The fertilisation of an egg by a sperm results in offspring that are genetically different to their parents, with a combination of their parent's DNA
• Why is it beneficial for there to be

  geneticvariation within a species?The species is more able to adapt to changing environmental conditions e.g. climate change
• What is the benefit of asexual reproduction?

  There is no need to find a mate

  It has a fast reproductive rate
• What is a mutation?

  A change in the DNA code
• Do mutations in genes always have an effect on the organism?

  No - most have no effect

  Some are beneficial and can give a survival advantage

  Some are harmful and can lead to disease
• Why is ionising radiation dangerous?

  It increases the chance of mutations

  The higher the dose, the greater the chance of mutation
• Which inherited disease, caused by a gene mutation, results in the build-up of thick mucus in the bronchioles?

  Cystic fibrosis
• What is the probability of a child inheriting cystic fibrosis if both parents are carriers (heterozygous for the condition)?

  25%

  Child inherits two recessive alleles (nn)

  
• How are new genes formed?

  Throughrandommutations
• What is evolution?

  The change in the characteristics of a species over several generations
• What is 'natural selection'?

  A theory put forward by Wallace and Darwin to explain evolution

  Random mutation of genes enable better adapted individuals to survive, breed and pass on these genes to the next generation
• What are the steps involved in

  natural selection?1. Arandommutation gives rise to a beneficialcharacteristic (variation)2. Those organisms with the mutationsurvive,breedandpass on the beneficial geneto the nextgeneration3. Over time more of the population have the beneficialtrait
• What happens to species when the process of natural selection is too slow for organisms to adapt to changing environmental conditions?


  They becomeextinct
• Give examples of evolution that is happening at this present time

  Antibiotic resistance in bacteria

  Warfarin resistance in rats

  Pesticide resistance in plants
• Give a reason for the variation in organisms raised under identical

  environmentalconditionsGeneticcauses