Characteristics of Living Things
All living organisms share eight essential life processes, whether they're animals, plants, bacteria, fungi, or protoctists. Think of these as the ultimate checklist for life - if something ticks all eight boxes, it's officially alive!
The easiest way to remember these characteristics is with the acronym MRS H GREN. Each letter represents a different life process: Movement, Respiration, Sensitivity, Homeostasis, Growth, Reproduction, Excretion, and Nutrition. These processes work together to keep organisms functioning and surviving.
Viruses are the tricky exception here - they don't tick all the boxes since they can't grow or excrete on their own. This is why scientists debate whether viruses are truly "living" or not, making them perfect exam question material!
Quick Tip: Practice explaining each part of MRS H GREN in your own words - this shows you really understand the concepts rather than just memorising them.
Let's break down what each life process actually means. Movement is the ability to change position through muscle action. Respiration releases energy from food through chemical reactions in cells, usually requiring oxygen. Sensitivity means detecting and responding to environmental changes - animals use sense organs whilst plants respond to light and gravity.
Homeostasis maintains stable internal conditions like body temperature and pH levels. Growth involves permanent increases in size and dry mass (your mass without water). Reproduction creates offspring to continue the species. Excretion removes metabolic waste like CO₂ and excess substances. Finally, Nutrition involves taking in materials for energy, growth, and repair.
