Many characteristics are caused by a combination of both the environment and genes.Examples are height and skin colour.Height is partly determined by genes and partly by diet.Skin colour can be modified by exposure to the sun.Features influenced by the environment will show a continuous distribution and a range of values.Studies on identical twins can show the extent to which the environment plays a part in variation of some characteristics.Identical twins are produced when a fertilised egg splits into two.Both twins contain identical genetic material.Features such as intelligence have been investigated with no definitive conclusion reached as it is difficult to exactly duplicate human environments.Sources of environmental variation are radiation, chemicals in the environment and nutrition.
Environmental Causes of Variation
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Specification: OCR Biology A (H020), AS-level, 4.2.2 Classification and evolution. Topic: Classification and Evolution.
Key terms in this lesson
- organelle
- A membrane-bound structure within a cell with a specific structure suited to a specific function.
- lysosome
- A vesicle containing hydrolytic enzymes that breaks down waste material, old organelles and pathogens.
- phagocytosis
- The process by which a cell, such as a white blood cell, engulfs and digests a pathogen or debris.
- pathogen
- A microorganism that causes disease.
- antigen
- A molecule, usually a protein, on the surface of a cell or pathogen that triggers an immune response.
More in Classification and Evolution
- Comparative Biochemistry
- Types of Variation
- Genetic Causes of Variation - Mutation
- Genetic Causes of Variation - Meiosis and Chance
- Discontinuous Variation
- Continuous Variation
- Normal Distribution
- Standard Deviation
All 36 lessons in Classification and Evolution · All OCR AS-level Biology topics