Helping students to link TOK - Reasoning

Monday 28 July 2014

Students learn about "Reasoning" as a way of knowing in TOK lessons. Often examples illustrate the idea of reasoning like this;

  • a] If you don’t work hard in school you won’t pass your IB diploma
  • b] Kate doesn’t work hard
  • Conclusion: Kate won't pass her IB diploma

This is an example of deductive reasoning, in fact it is a conditional syllogism (but that's not important).

The important question is, do IB Biology students ever use this type of reasoning in Biology? Students rarely find it easy to make such links so here are a few examples of when reasoning is used in Biology.

In the cells topic

  • Eukaryotic cells contain membrane bound organelles including a nucleus.
  • Human cheek cells each have a clearly visible nucleus.
  • Conclusion: Human cheek cells are eukaryotic cells.

In the biochemistry topic

  • Biuret reagent turns lilac if there is protein present.
  • Sucrose solution does not turn Biurets reagent lilac
  • Conclusion: Sucrose solution doesn't contain protein.

In the genetics topic

  • Recessive genetic conditions only show themselves when there is no dominant allele present.
  • Cystic fibrosis does not occur in heterozygous individuals, with one dominant allele (and one recessive cf allele)
  • Conclusion: Cystic fibrosis is a recessive genetic condition.

If biology teachers can help students to connect their biology work to TOK then the students may think about Biology during TOK lessons which can only be a good thing.


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