Digestive system: A hydra eating: the mouth is where all the tentacles come together,near the center of the picture.The hydra is eating the round bug in its stomach. Before digestive [...]
Circulatory system: A dog heart What is the circulatory system? The circulatory system takes food and air from outside your body and brings it all over your body so that [...]
Chordates include this giraffe from Kenya What is a chordate? Any animal that has a spinal cord is a chordate. This group covers most of the creatures you see at [...]
A frog sitting half in the water: Evolution of frogs When did frogs evolve? Frogs developed out of lungfish about 375 million years ago, in the Devonian period. They used their [...]
Evolution of fish: a lungfish Why did fish leave the water? About 400 million years ago, during the Devonian period, the Earth was going through an especially warm period. Some [...]
History of fish: it looks like a severed tentacle but it's a lamprey. When did fish evolve? About 510 million years ago, in the Cambrian period, some of the worms [...]
Bee on a flower What are arthropods? Insects, spiders, crabs, and lobsters are all arthropods, so there are a lot of arthropods on Earth. Annelid worms All our biology articles [...]
Evolution of grasshoppers: Grasshopper sitting on a leaf Why do grasshoppers jump? When grasshoppers first evolved from earlier insects, about 300 million years ago, they lived in forests of huge [...]
