Introduction to nutrition

Jenny and Michael are preparing dinner for their dad’s birthday. We often use food to show someone we care about them. We prepare their favourite dishes, or share a meal together. But food is so much more than that! It provides us with materials — the nutrients — necessary for survival.

It’s not only humans who need food to survive. All living things — organisms — require nutrients to stay alive! In fact, obtaining and using nutrients — what we call nutrition — is one of the basic characteristics of living things! Nutrition allows an organism to carry out chemical reactions that release energy. This energy then powers movement and growth.

It also powers the repair of an organism if it gets damaged. Not all organisms obtain their nutrients in the same way however. You have to make yourself a meal when you’re hungry, but plants don’t have to! So how do plants get their nutrients? Plants take in simple substances from their environment and transform them into nutrients through chemical processes.

They absorb water and carbon dioxide. With energy from the sun, these combine into glucose and oxygen — and glucose is plant food! This is the process of photosynthesis and you can think of it as the plant prepping its meal. When a living organism makes its own nutrients ‘automatically’ from simple chemical substances, we call that type of nutrition autotrophism. Organisms who get their nutrients through autotrophism are called autotrophs.

Along with plants, other examples of autotrophs include algae and some bacteria. Now, think of yourself for a moment. When you feel hungry you eat something. You can’t produce your own nutrients. You might eat some fruit, or a burger.

Whichever one you choose, the food contains parts of other organisms — plants or animals. That’s where you get your nutrients from — other organisms! This mode of nutrition that involves taking in “ready-made” nutrients from other organisms is heterotrophism. Along with you and me, other animals, fungi and some bacteria, need to get nutrients from other organisms — they are heterotrophs too! There are three major groups of heterotrophic organisms.

The first contains those organisms that only eat plants — herbivores. The second group contains those organisms that only eat animals — carnivores. Finally, the third group contains those organisms that eat both plants and animals — omnivores. Think, which group of heterotrophs do humans belong to? The main purpose of nutrition is to keep us alive, but food also brings us together and makes us happy!

Happy birthday dad!