Paper 2: Topic 6 Inheritance, variation & evolution - Variation & evolution Flashcards Preview

Mrs P's GCSE Biology > Paper 2: Topic 6 Inheritance, variation & evolution - Variation & evolution > Flashcards

Flashcards in Paper 2: Topic 6 Inheritance, variation & evolution - Variation & evolution Deck (52)
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Define the term variation

Differences in the characteristics of individuals within a population


State 3 causes of variation within a population

  1. Genetics
  2. Environment
  3. Combination of genetics and the environment


Explain how genetics can lead to variation in a population

  • Different individuals will inherit different combinations of alleles
  • The different combination of alleles will cause differences in the proteins that are or are not produced
  • This will cause differences in the characteristics in the different individuals
  • E.g. eye colour, blood group, genetic disorders such as cystic fibrosis


Explain how the environment can lead to variation within a population

Different environmental factors can affect certain characteristics in individuals


  • Road accident → loss of a limb
  • Exposure to UV light → affects melanin content of the skin


Explain how genetics and the environment can lead to variation in a population

Individuals who possess certain genes and are exposed to certain environmental factors can have different characteristics e.g.

  • skin colour (affected by UV light and gene for melanin production)
  • body mass (affected by quality and quantity of diet and the genes for muscle development and growth)


State what factors influence most physical characteristics

Genetics AND the environment


State what causes variation within a population



Describe the range of variation observed in most populations

  • Extensive
  • This means there is a wide range of variants for most characteristics within a population


Define the term ‘evolution’ Hint: 3 key parts to this definition

  • A change in the inherited characteristics of a population over time
  • Through a process of natural selection
  • Which result in the formation of a new species


Explain the theory of natural selection

  • A mutation occurs within an individual in a population
  • This causes variation to develop within a population exists
  • Some individuals are more suited to their environment (due to the characteristics they possess)
  • The individuals who are more suited to the environment are more successful
  • These individuals are more likely to survive and breed
  • These individuals will pass on the alleles for the beneficial characteristics to the their offspring
  • Over a LONG period of time and MANY generations the beneficial alleles will become more common in the population
  • Over time the variants that posses the best phenotypes are selected for and increase in number


Define the term ‘selective breeding’

Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics


State 2 reasons why Humans have used selective breeding for centuries

Humans have been doing this for thousands of years since they first bred food crops from wild plants and domesticated animals.


State the 4 key steps in artificial selection/selective breeding

  • Selective breeding involves choosing parents with the desired characteristic from a mixed population
  • They are bred together
  • From the offspring those with the desired characteristic are bred together
  • This continues over many generations until all the offspring show the desired characteristic


Give 4 features that have been selected for in selective breeding

  1. Disease resistance in food crops
  2. Animals which produce more meat or milk
  3. Domestic dogs with a gentle nature
  4. Large or unusual flowers


State 3 disadvantages of using artificial selection / selective breeding

  1. Inbreeding can result in a reduced gene pool
  2. Inbreeding can result in health problems
  3. Inbreeding results in reduced variation within the population


Explain what is meant by the expression ‘reduced gene pool’

The number of different alleles in a population decreases


Explain how artificial selection can result in health problems in the population

  • Selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects
  • This is because of a reduced gene pool


Explain how artificial selection can reduce the gene pool

The number of alleles in the population can be decreased over time


Explain how artificial selection can cause problems is a new disease occurs

  • As a result of selective breeding there is less variation in a population
  • So all the individuals in the population have very similar characteristics
  • This means that if one individual is likely to be killed by the new disease then all the individuals in the population are also likely to die from the new disease
  • This is because there is less chance of any resistant alleles being in a population


Give 3 reasons why a gardener/farmer may use selective breeding

  1. To produce a crop with higher yield
  2. To produce a crop with more fruits
  3. To produce a crop with larger fruits


Describe the process of genetic engineering

A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic


Give 2 characteristics that have been genetically engineered in plants

  1. Resistant to diseases
  2. To produce bigger better fruits


Describe an example of where bacteria have been used in genetic engineering

Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes


Describe the 10 key steps in genetic engineering

  1. The desired gene is identified
  2. The gene for the desired protein is isolated (cut) from the DNA of one organisms genome using a restriction enzyme
  3. Plasmids are isolated from bacteria
  4. The same restriction enzyme is used to cut the plasmids
  5. The cut plasmids and the desired gene are mixed together in the presence of DNA ligase
  6. The DNA ligase joins the plasmid and desired gene together to form a recombinant (hybrid) plasmid
  7. The recombinant/hybrid plasmid is inserted back into the bacteria
  8. The bacteria are grown in large scale fermenters
  9. The bacteria produce the required protein
  10. The protein is extracted, purified and packaged for use


Explain why plasmids used in genetic engineering are called vectors

A vector transfers something from one place to another

In this case it transfers the DNA from one organism to another


State the 2 types of vectors that are usually used in genetic engineering

  1. Bacterial plasmids
  2. Viruses


Give 3 examples of genetic engineering

  1. Production of human insulin (Humulin) to treat type I diabetics
  2. Production of GM crops
  3. Production of specific drugs in sheep’s milk to treat disease


Give 4 reasons scientists may want to use genetic engineering in plants

  1. To produce a herbicide or insecticide resistant crops
  2. To produce plants with larger fruits
  3. To produce plants which are disease resistant
  4. To produce crops with greater yield


Define a insecticide

A chemical that selectively kills insects


Define a herbicide

A chemical that selectively kills plants e.g. broad leaved plants

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