Wednesday, 5 January 2011

MYRSFO: A2 Biology

By A2, the students should be able to deal with some quite high-level research, and read some straightforward scientific papers. They have probably carried out some ecological fieldwork, so are used to the particular issues raised by sample size, data collection, and trying to do science in horizontal rain (why there isn't more uptake for earth science degrees, I do not know).

Unit BIOL4
  • Succession from pioneer species to climax community
  • At each stage in succession, certain species may be recognised which change the environment so that it becomes more suitable for other species
  • The changes in the abiotic environment result in a less hostile environment and changing diversity
  • Species exist as one or more populations
  • The concepts of gene pool and allele frequency
  • The Hardy-Weinberg principle. The conditions under which the principle applies
  • Differential reproductive success and its effect on the allele frequency within a gene pool
  • Directional and stabilising selection

Unit A2.1
Students should be able to:
  • Understand how populations grow
  • Distinguish between r- and K-selected species
  • Understand the ways in which populations may interact
Unit A2.2
Students should be able to:
  • Understand the concept of the gene pool
  • Understand the Hardy-Weinberg equation and apply it to calculate allele and genotype frequencies in an outbreeding population
  • Understand selection and its contribution to the maintenance of polymorphic populations and evolutionary change in populations
  • Understand the concept of species and the process of speciation

Unit 4
Students will be assessed on their ability to:
  • Describe the concept of succession to a climax community
  • Describe how evolution (a change in the allele frequency) can come about through gene mutation and natural selection
  • Explain how reproductive isolation can lead to speciation
  • Describe the role of the scientific community in validating new evidence (including molecular biology, eg DNA, proteomics) supporting the accepted scientific theory of evolution (scientific journals, the peer review process, scientific conferences)
  • Describe how DNA profiling is used for identification and determining genetic relationships between organisms (plants and animals)

Unit F215
Candidates should be able to:
  • explain why variation is essential in selection
  • use the Hardy–Weinberg principle to calculate allele frequencies in populations
  • explain, with examples, how environmental factors can act as stabilising or evolutionary forces of natural selection
  • explain how genetic drift can cause large changes in small populations
  • explain the role of isolating mechanisms in the evolution of new species, with reference to ecological (geographic), seasonal (temporal) and reproductive mechanisms
  • explain the significance of the various concepts of the species, with reference to the biological species concept and the phylogenetic (cladistic/evolutionary) species concept
  • explain, with examples, the terms interspecific and intraspecific competition

Unit BY5
  • Genetic and environmental factors produce variation between individuals
  • Variation may be continuous and discontinuous; heritable and nonheritable. Inter and intra-specific competition for breeding success and survival
  • Selective agencies (e.g. supply of food, breeding sites, climate). The gene pool and genetic drift
  • Selection can change the frequency of alleles in a population
  • Isolation and speciation
  • Separation of populations by geographical, behavioural, morphological seasonal and other isolation mechanisms. Hybrid sterility
  • Darwin's theory of evolution that existing species have arisen through modification of ancestral species by natural selection
  • Principles of succession as illustrated by the change from bare rock to woodland
  • Use of terms primary and secondary succession, pioneers, sere and climax community
A2 Biology is much more concerned with ecology, speciation and reproductive isolation. Some new examples of evidence for speciation, co-evolution of parasites, or even a tame scientist with a collection of cichlid fish, will go down very well indeed.


  1. Don't have any Cichlids yet I'm afraid. I do have some bitterlings, but I can't get the clams they parasitise to stay alive long enough to breed. When I get a bigger house I'm tempted to get a small tank of Neolamprologus multifasciatus though. Videos can be provided on request, but don't hold your breath.

  2. A level biology certainly seems to have changed from the early 80's.
    Although field work doesn't seem to have.
    I spent a week on the Isle of Man at Easter studying beaches and comparing the Ecology of sandy and rocky beaches. Don't recall it raining.

  3. A-Level has changed from when I sat it in 1998! I remember having to learn a good half dozen intermediates in the Krebs cycle, and about the same in the Calvin cycle. I also had to know the difference between C3, C4 and CAM plants. Edexcel have removed the kidney and excretion from the specification, and some of the losses are worrying.

    I have a dilemma as to when to have fieldwork in the A2 course - we get a few students transferring for their A2 year, so it has to be done during the A2 course, rather than after the AS exams in the summer. After about March it's getting too late to get the work done in time for the coursework deadline. October (which was when we did it this time round) is slightly warmer, but there are fewer signs of life. February (last year's stint) was very cold but there were bluebells up and catkins on all the hazel trees.


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