Billions of Living Things

How many organisms live on Earth?

Earth is covered with billions of living things. The plants, animals, fungi, protists, and microorganisms on Earth come in all sorts of sizes, shapes, and colors.

This young impala has two red-billed oxpeckers on its head searching for ticks. Imagine the highest mountain on Earth. Then, think of the harshest possible place to live--maybe the deepest trench of the ocean, a boiling hot geyser, or the bitter cold of the arctic. Organisms have found a way to survive in every one of those places!

Some organisms are strange, some are smelly, some are hideous, and others are dazzling. Each one has specific roles and functions in life, and together, they are all connected in ways we can only begin to understand.

Question

The photo above shows a ram with two birds on its head. What do you think the birds are doing, and why? Think about it, then click the Answer button to find out if you were right.

The birds are eating blood-sucking insects called ticks. To the ram, ticks could mean discomfort and disease. To the red-billed oxpeckers, or "tickbirds," they mean a delicious meal! Relationships like these help both species, and they can even mean the difference between life and death for both partners.