Living organisms have certain life processes in common. There are seven things that they need to do to count as being alive. The phrase MRS GREN is one way to remember them. These letters stand for movement, respiration, sensitivity, growth, reproduction, excretion and nutrition.
It can be easy to tell if something is living or not. A teddy bear might look like a bear, but it cannot do any of the seven things it needs to be able to do to count for being alive. All it can do is what you make it do.
On the other hand a car can move, it gets energy from petrol, (like nutrition and respiration) it might have a car alarm (sensitivity) and it gets rid of waste gases through its exhaust pipe. (excretion) but it cannot grow or make babies. So a car is not alive.
Movement is one of the conditions of a living organism. Sometimes it is not that obvious in examples such as plants and fungi, but animals can move like a monkey can climb trees and fish can swim in water but all living organisms can move one way or another.
Respiration, or being able to breathe, is the next condition. Some living things breathe oxygen in the air using lungs whilst others like fish use gills to breathe underwater and plants use photosynthesis.
Sensitivity is all about being able to detect things. Like humans use fingers and hairs to detect things. Whereas cats and dogs use whiskers to detect things and octopuses use tentacles to detect objects in and out of the water.
Growth is one of the most important thing for a living creature. If things cannot grow you would stay the same size as when you are born to when you die :0 so a bird will stay the same size as when they hatch.
All living things need to reproduce. There is also a huge amount of diversity has evolved, now reproduction is done in many different ways in many different species. For example mammals give birth to living young, whereas reptiles, fish and birds lay eggs which over a certain amount of time will hatch into young.
Another thing all living organisms need to do to survive is excretion. This comes in different forms such as, faeces, urine, carbon dioxide. (CO2)
Nutrition, or obtaining and consuming food, is the N in the mnemonic MRS GREN. This means all living things must eat to gather nutrition from the plants and animals to survive. For instance lions eat other animals, but on the other hand bees gather nectar from plants to survive.
In conclusion, it’s well known that life on planet earth is very diverse. From the fish in the sea, to the animals on land we all need to do the same things to survive, they need to move, breath, feel, grow, reproduce, excrete, and eat. If living organisms don’t do these things they will not be able to survive.
