We don't know exactly when the first animals on Earth appeared, but it's thought to be around 700 million years ago. Around 541 million years ago, at the start of the Cambrian period, hundreds of thousands of new species appeared within a span of about 20 million years — an event known as the Cambrian explosion. Since then, millions — or possibly billions — of species have come and gone. Scientists estimate that 99.9% of all creatures that ever lived have gone extinct.
Researchers think there are now around 7.7 million animal species living on Earth, with thousands more discovered every year. But species are also going extinct at an alarming rate, with many likely vanishing before they've even been formally recognized. Many scientists even say we're entering a sixth mass extinction.
How much do you know about the animals currently living on our planet? Take our quiz to find out. If you need a hint, hit the yellow button. Good luck!
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