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Topic 6: Microbiology, immunity and ecosystems - Edexcel A-Level Biology B overview

An overview of Topic 6 of Edexcel A-Level Biology B (Salters-Nuffield, 9BN0), covering microorganisms and disease, the immune response, ecosystems and succession, and populations and sustainability, and how the topic is examined.

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  1. The four dot-point areas
  2. How Topic 6 is examined
  3. How to study Topic 6
  4. Work through the dot points
  5. For the official specification

Topic 6 of Edexcel A-Level Biology B (specification 9BN0, the Salters-Nuffield course) is titled Microbiology, immunity and ecosystems. It brings together how microorganisms cause disease, how the body defends itself, and how energy and populations behave in ecosystems. This page maps the four dot-point areas and how they are examined.

The four dot-point areas

Microorganisms and disease
The structure of bacteria and viruses, how pathogens cause disease, the culture and growth of microorganisms, and the action and resistance of antibiotics.
The immune response
Non-specific and specific immunity, phagocytes, B and T lymphocytes, antibodies, immunological memory, and vaccination.
Ecosystems and succession
Ecosystem structure, energy flow through food chains and webs, nutrient cycles, and ecological succession.
Populations and sustainability
The factors limiting population size, predator-prey relationships and carrying capacity, the sampling of populations, and sustainable management.

How Topic 6 is examined

Topic 6 features in Paper 1 (ecology) and Paper 2 (microbiology and immunity), and is revisited in the synoptic Paper 3. Expect precise descriptions of the immune response, antibiotic resistance explained as natural selection, energy-transfer calculations, sampling methods from the core practicals, and balanced arguments about sustainability.

How to study Topic 6

  1. Learn the immune response in order. Distinguish non-specific from specific, and the roles of phagocytes, B cells and T cells.
  2. Explain resistance as selection. Link antibiotic resistance back to mutation and natural selection.
  3. Handle energy and sampling maths. Calculate energy transfer and use quadrats, transects and mark-release-recapture.
  4. Argue sustainability both ways. Balance human needs against protecting ecosystems.

Work through the dot points

Each dot point has a focused answer page with worked exam questions and cross-links: microorganisms and disease; the immune response; ecosystems and succession; and populations and sustainability.

For the official specification

Pearson publishes the full specification (9BN0), past papers and mark schemes at qualifications.pearson.com. Always revise from the current specification and Edexcel's own past papers.

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