DIVERSITY AND EVOLUTION [TOPIC GUIDE]

  1. Introduction to diversity and evolution
    • Diversity and evolution is a core JC2 topic in H2 BIO A levels. The basis of the topic is to compare organisms so as to obtain the degree of similarity or differences. The differences are important to allow for natural selection. As each generation descends with modifications, this may eventually lead to formation of new species. Some believe this is due to accumulation of small mutations over time. Sometimes environment may play a role in such events. How it does so is different for each scenario.


  2. Curated materials to help you

  3. Most common phrasing errors made by students during exams
    • Traits are passed on to the next generation
    • Organisms mutate to adapt to the environment
    • All mutations are inheritable and can be passed from one generation to the next
    • When mutations result in favorable alleles, they will then be passed on to the next generation


  4. Exam tips
    • Genetic drift ≠ antigenic drift
    • Genetic ≠ phylogenetic concept of species
    • Analogy ≠ biogeography ≠ convergent evolution. Don’t use these words interchangeably
    • When explaining heterozygous advantage, you should be careful which example you give and how you explain it. If you use the example of sickle cell trait, then describe the co-dominance behavior. Many erroneously write about masking of the recessive allele instead.
    • Genetic drift, gene flow, natural selection and non-random mating DON’T create alleles. Mutations do. The 4 mechanisms only serve to change the allele frequencies.
    • Isolated land mass doesn’t automatically imply allopatric speciation. These type of questions often highlight an organism in the scenario such as fishes for example that must be considered too!
    • Examiners like to use non-standard terms in questions pertaining to this topic. Don’t memorize them! Instead, correlate them to concepts you have learnt.


  5. Questions
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