Rebecca L. Johnson

The digestive system is made up of the tongue, the esophagus, the stomach, the intestines...

The muscular system is made up of three different kinds of muscles: skeletal muscles, smo...

Take a walk in the boreal forest. Sunlight filters through tall spruce and pine trees. It...

Take a walk in the deciduous forest. Sunlight filters through new green leaves. It's earl...

Take a walk in the desert. It's hot and dry—and full of life. An elf owl peers out ...

Take a walk in the prairie. This land of all grass and open sky is full of life. You can ...

Take a walk in the rain forest. It's hot and humid and humming with life. Look up into th...

Take a walk in the tundra. In this cold, harsh biome at the top of the world, summer is s...