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AS Biology
Unit 2 Module 3: Biodiversity and Evolution
OCR
Evolution
Evolution has generated a wide variety of organisms. The fact that all organisms share a common
ancestry allows them to be classified. There is increasing recognition of the need to maintain
biodiversity. “Nothing in biology makes sense except in the light of evolution” Theodosius
Dobzhansky 1973.
Key Words
Variation. Continuous variation. Discontinuous variation. DNA. RNA. Allele. Gene. Species. Hypha.
Adaptation. Xerophyte. Evolution. Photosynthesis. Disease. Enzyme. Respiration. Stomata. Water
vapour potential. Diffusion. Transpiration. Pits. Speciation. Natural selection. Selection pressure.
Allopatric. Sympatric. Protein. Amino acid. Diversity. Metabolism. Receptor site. Antibiotic.
You should be able to:
 Define the term variation
 Discuss the fact that variation occurs within as well as between species
 Describe the differences between continuous and discontinuous variation, using examples
of a range of characteristics found in plants, animals and microorganisms.
 Explain both genetic and environmental causes of variation.
 Outline the behavioural, physiological and anatomical (structural) adaptations of organisms
to their environments.
 Explain the consequences of the four observations made by Darwin in proposing his
theory of natural selection.
 Define the term speciation.
 Discuss the evidence supporting the theory of evolution with reference to fossil, DNA and
molecular evidence.
 Outline how variation, adaptation and selection are major components of evolution.
 Discuss why the evolution of pesticide resistance in insects and drug resistance in
microorganisms has implications for humans.
Recommended reading
Core Text Book
Toole & Toole, 4th Ed.
Pgs 210 - 219
Pgs 177-181 and 199-209
NAS Genetics, Evolution and
Biodiversity
Pgs 88-92 and 101-108