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 as well as 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.

    A selection of materials for diversity and evolution

    Most common phrasing errors students commit during exams

    • Traits are passed on to the next generation
    • Organisms mutate to adapt to the environment
    • All mutations are inheritable and can pass from one generation to the next
    • When mutations result in favorable alleles, they will then pass on to the next generation

    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 where it doesn’t apply!
    • 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.

    BYang’s tough questions bank

    • The development of the human nervous system only completes in the mid 20’s long after birth leading to a fully functional adult. Suggest why that is the case. [4m. Date of creation 210614]
    • To date, there are no documentation of blue pigment production in animals. Any perception of blue color is due to the unique structural makeup of the animal’s exterior that changes the absorption and reflection patterns. Suggest why changing structural characteristics is preferred over the macro-evolution of a blue pigment in animals. [3m. Date of creation 210929]
    • Suggest 3 reasons why 2 different organisms of the same species having the same allele may have different survival probabilities. [6m. Date of creation 220923]
    • In the experimentation of dog breeding, a type of artificial selection, the tame allele is frequently associated with the allele coding for the droopiness of the ear flap. There are no known biochemical interactions between the 2 gene products. Suggest a potential cause of such a phenotypic phenomenon, and explain how these 2 traits can be favored. [3m. Date of creation 220923]
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    Questions and other matters

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    • You may also be interested to know how to boost your performance for A levels.