Characteristics & Classification of Living Things

Introduction to Classification

The study of living organisms involves understanding their classification into various groups based on shared characteristics. The acronym MRS. GREN serves as a mnemonic to summarize the seven key characteristics of living organisms:

1. Movement: An action by an organism or part of an organism causing a change of position or place.
2. Respiration: The chemical reactions that break down nutrient molecules in living cells to release energy for metabolism.
3. Sensitivity: The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.
4. Growth and Development: A permanent increase in size and dry mass resulting from an increase in cell number, cell size, or both.
5. Reproduction: The processes that make more of the same kind of organism.
6. Excretion: The removal from organisms of toxic materials and waste products of metabolism, including respiratory waste and substances in excess of requirements.
7. Nutrition: The intake of materials for energy, growth, and development. Plants require light, carbon dioxide, water, and ions; animals need organic compounds, ions, and usually water.