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All the creatures on Planet Earth affect each other. That's what we call ecosystems. Usually they affect each other in quite small ways, but there's one creature who affects all the others in quite an extreme way. It's called the human being.

Because there are so many of us, and because we've learnt to make very powerful tools, we can make huge changes like cutting down all the trees in a forest. Or sometimes we make changes that we hardly even notice, like throwing litter away.

When plastic ends up in the ocean, it gets eaten by lots of creatures, but it's not just them who get poisoned by the plastic. It's all the bigger creatures who eat these as well. But because as humans, we can think about these things and understand them, we can also change ecosystems in a positive way. Like build marine parks to protect endangered species.

There are also many things that you can do to make a difference, like recycle or grow your own vegetables. These things might seem small, but if enough people do it, it can have a huge impact on the planet's ecosystem.