exam questions

• Explain how natural selection could produce a population of plant that could be tolerant to acidic soil found around the mine shaft (4)

  • variation in the population of plant due to mutations creating different phenotypes.
  • therefore, when selection pressure of acidic soils is introduced, only the species of plant with advantageous allele to survive in these conditions, will survive and reproduce.
  • These advantageous alleles will then be passed onto their offspring who will also be able to withstand acidic soil
  • Frequency of advantageous allele increases in the population and gene pool
• State what is meant by the term species:

  -       Individuals which can interbreed to produce fertile offspring
• other than the fossil record, state 2 sources that provide evidence for evolution (2)

  -       DNA/gene sequencing 

  -       Development of antibiotic resistance in bacteria
• What event must occur for speciation to happen (1)

  -       There must be no gene flow between the populations
• Explain how urbanisation could result in speciation within a population of cape dwarf chameleons over time (5)

  • Urbanisation= geographical barrier forming between 2 populations of cape dwarf chameleons e.g., via roads
  • different selection pressures acting on the different populations 
  • Different alleles are advantageous to survive and reproduce 
  • Genetic differences will accumulate in population over time and phenotypes will change 
  • reproductively isolated from each other and no longer able to breed with each other to produce fertile offspring 
  • =allopatric speciation
• Compare and contrast allopatric and sympatric speciation (4) 

  • Allopatric has a geographical barrier and sympatric does not, usually a mutations 
  • Both experience no gene flow between populations 
  • Both produce reproductively isolated species which cannot interbreed to produce fertile offspring
  • Both result in changes to the allele frequencies with the populations 
  •  In sympatric speciation the populations may live in the same habitat
  • allopatric speciation the population live in different habitats/ experience different environmental pressures.
• Describe how different species of fish have evolved in lakes and rivers in Africa (5) 

  • Random mutations are responsible for variation within the pop, creating different phenotypes 
  • Different selection pressure is acting on different habitats 
  • Some individuals have advantageous alleles for example the food they eat 
  • Fish that have advantageous alleles survive and reproduce and pass on to offspring
  • Reduced gene flow between populations 
  • Sympatric speciation of fish in the same lake, allopatric speciation of species of fish in different lakes- geographically isolated