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| Growth at Different Levels |
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| Growth is defined as an increase in the size and weight of an organism due to synthesis of new protoplasm. |
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| Growth takes place at 2 different levels in an organism. |
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| Strategies of Growth |
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| Molecular Levels |
| Growth at the molecular level involves the synthesis of new molecules. |
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| Cellular level |
| Growth at the cellular level involves four stages |
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 Cell expansion: an increase in the size of the cell due to formation of new protoplasm. |
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 Cell division: the cells increase in number due to mitotic cell division |
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 Cell differentiation: the cells became specialized to per form specific roles in the organism. |
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 Matrix formation: addition of intercellular materials, termed apoplasmatic substance, secreted by the cells between them. |
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| Mechanism of Growth |
| At the cellular level, growth is the increase in the amount of protoplasm (nuclues + cytoplasm). During growth, the synthesis of complex molecules like proteins nucleic acids and carbohydrates is at a higher rate than the rate at which the complex molecules are broken down. |
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| During growth, the anabolic process dominates the catabolic activity. The materials formed during anabolism- the proteins, provide the building blocks for the growth of the organism and the carbohydrates supply the extra energy needed for growth. This is called positive growth. If the anabolic and catabolic process are balanced, there is no addition to the bulk of the body and so no growth takes place. |
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| When decomposition exceeds synthesis, as in fasting, first the internal food reserve in the form of glycogen and fats is catabolised to run the metabolic depletion of the living matter. This phenomenon is called degrowth or negative growth. |
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