What makes something alive? This might seem like a simple question, but scientists have spent years figuring out exactly what separates living things from non-living things. The answer lies in seven special processes that all living organisms carry out. These are called the seven life processes and every single living thing on Earth - from the tiniest bacteria to the largest whale - performs all of these processes.
To help you remember these seven processes, scientists use the acronym MRS GREN. Each letter stands for one of the life processes, making it much easier to memorise them all.
Key Definitions:
Life processes are essential because they help us classify what is living and what is not. A rock might move if you push it, but it doesn't carry out all seven life processes. A plant might seem very different from an animal, but both carry out all seven processes - just in different ways!
Let's explore each of the seven life processes in detail, understanding what they mean and seeing examples of how different organisms carry them out.
Movement is the ability of an organism to change its position or move parts of its body. This doesn't just mean running or walking - it includes any type of movement that helps the organism survive.
Most animals can move their whole body from place to place. Cheetahs run, fish swim and birds fly to find food, escape predators, or find mates.
Plants can't move their whole body, but they can move parts of themselves. Sunflowers turn their heads to follow the sun and plant roots grow towards water.
Even tiny organisms like bacteria can move using whip-like structures called flagella to swim through water.
Respiration is the process of releasing energy from food. This happens inside cells and provides the energy needed for all other life processes. Don't confuse this with breathing - respiration happens in every cell of every living thing!
When you eat a sandwich, your body breaks down the food and uses oxygen to release energy from it. This energy powers everything you do - from thinking to moving to growing. Even when you're asleep, respiration continues in every cell of your body to keep you alive.
Sensitivity means being able to detect and respond to changes in the environment. Living things need to sense what's happening around them to survive and thrive.
Humans have five main senses: sight, hearing, smell, taste and touch. These help us detect light, sound, chemicals and physical contact. When you smell food cooking, your sensitivity to chemicals in the air tells your brain that food is nearby.
Plants are sensitive too! They can detect light (growing towards it), gravity (roots grow down, shoots grow up) and even touch (like the Venus flytrap snapping shut when an insect touches its trigger hairs).
Growth is the permanent increase in size and complexity of an organism. All living things grow at some point in their lives, though they do it in different ways and at different rates.
Humans grow rapidly as babies and children, then more slowly as teenagers, before stopping in early adulthood. We grow by making new cells.
Trees can grow for hundreds of years, getting taller and wider. They grow by adding new layers of wood and bark each year.
Bacteria grow very quickly, sometimes doubling in size in just 20 minutes before dividing into two new bacteria.
Reproduction is the process of producing offspring - new individuals of the same species. This ensures that species continue to exist even after individual organisms die.
There are two main types of reproduction:
Emperor penguins travel hundreds of miles across Antarctic ice to reach their breeding grounds, where they mate and raise their chicks together. Meanwhile, strawberry plants can reproduce by sending out runners that grow into new plants - no partner needed! Both strategies work, but they suit different lifestyles and environments.
Excretion is the removal of waste products that are made by the organism's own chemical processes. These waste products could be harmful if they build up inside the organism.
Humans excrete waste in several ways: carbon dioxide through our lungs when we breathe out, urea through our kidneys in urine and excess water and salts through our skin when we sweat.
Plants excrete oxygen during photosynthesis (which is actually waste for them, but lucky for us!) and they can also excrete waste products through their leaves or store them in parts that fall off, like autumn leaves.
Nutrition is the process of obtaining and using food for energy, growth and repair. Different organisms get their nutrition in completely different ways.
Animals are heterotrophs - they must eat other organisms to get their food. Lions eat zebras, rabbits eat grass and humans eat both plants and animals.
Plants are autotrophs - they make their own food through photosynthesis, using sunlight, carbon dioxide and water to create glucose.
Fungi are decomposers - they break down dead organic matter and absorb the nutrients, like mushrooms growing on rotting logs.
The seven life processes don't work in isolation - they're all connected and depend on each other. For example, nutrition provides the materials needed for growth and reproduction, while respiration provides the energy for movement and sensitivity. Excretion removes the waste products created by respiration and other processes.
Let's follow a rabbit through its day to see all seven life processes in action: It moves to find fresh grass (Movement), eats the grass for energy (Nutrition), breaks down the grass in its cells to release energy (Respiration), stays alert for predators using its keen hearing and sight (Sensitivity), gradually gets bigger as it matures (Growth), may mate to produce baby rabbits (Reproduction) and removes waste products through urine and faeces (Excretion). All seven processes working together keep the rabbit alive and healthy!
Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition - these seven processes are what make something truly alive. Every living organism, no matter how simple or complex, carries out all seven of these processes throughout its life.
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