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Growth and development

Growth and development

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What happens to organisms made up of more than one cell when the cells divide and take up more space?

Growth and development

Sofia, Maria’s little sister, was born two months ago. Maria doesn’t think Sofia is growing fast enough — Maria wants someone to play with her, but Sofia can’t do anything by herself! So Maria’s parents surprise her with a puppy, which Maria decides to call Diva. Diva the puppy is also just two months old, but she can do a lot more than baby Sofia can. The puppy can walk and run around, and she’s great at playing fetch!

A few months later, Diva is twice as big as when the family got her. Sometimes, Maria wishes Diva could go back to being a tiny puppy — it would be so much easier to carry her around! But once a puppy increases in size, it can’t shrink again. The puppy has grown. Growth is a biological process, and one of the basic characteristics of living things!

Organisms grow when their cells divide. In organisms that are made up of single cells, this division is considered growth in itself. In organisms made up of more than one cell, cells divide so there are more new cells, which take up more space. And this makes the organism bigger! Living things don’t grow indefinitely.

Sooner or later they reach a final size. Think of adults you know. If you measure your height a couple of times a year, it’s likely you’re a little bit taller every time. But if you were to measure the height of an adult each time, their height doesn’t change. Baby Sofia is seven months old now.

The other day when Maria was tickling her, Sofia grabbed hold of Maria’s finger and… bit it! Sofia now has her first tooth. When organisms grow, other things happen as well. One of them is that the organism changes shape or becomes more complex. For example, a baby starts getting teeth.

This is development. Development always accompanies growth. Even very complex organisms, like you or a cat, begin only as a fertilised cell, that starts dividing into more cells. Initially, these cells are all the same. However, they all have the potential to develop, for example into a muscle cell, a skin cell or a nerve cell.

You grew from one fertilised cell because that cell divided, and the resulting cells kept dividing. And from that moment on, you started to develop, to become the complex individual you are today. You might not have a younger sibling or a puppy that you can watch grow and develop. But you can observe growth and development by a simple experiment! Find a plant outside — ideally in an area where it won’t be cut down or eaten by animals.

Then measure how long or tall it is, how many leaves it has and whether it has any flowers. Then go back to it every week and take the measurements again. You can see how much the plant grows week by week! If you do this over weeks, or months, you might notice other changes as well. Maybe the plant you chose will develop new branches or leaves, or even fruit!

Sofia is now 5 years old. She can do many things by herself, but she prefers doing things with Maria. I’m glad Sofia can never go back to being a baby, she’s so much more fun now!