CK-12 Foundation
Ck 12: Life Science: Human Sperm
[Free Registration/Login may be required to access all resource tools.] Sperm, the male reproductive cells, are tiny. In fact, they are the smallest cells in the human body. Some people think that they look like tadpoles. Learn more...
Curated OER
Science Kids: Science Images: Frog Metamorphosis
This drawing shows the metamorphosis of a frog. The five different images each show a stage in the development from tadpole to fully grown frog.
CK-12 Foundation
Ck 12: Life Science: Frogs and Toads
[Free Registration/Login may be required to access all resource tools.] Frogs and toads are amphibians in the order Anura. In terms of classification, there is actually not a big difference between frogs and toads. Learn more about frogs...