Some bacteria can convert atmospheric nitrogen into forms that plants can use. This process is called:

Scientists measure the amounts of a radioactive isotope and its decay products in a rock. This information can be used to:

Cyanobacteria are important examples of autotrophic bacteria because they:

A scientist observes a spherical bacterium under a microscope. Which term best describes its shape?

The appearance of photosynthetic organisms was particularly important in Earth’s history because:

Why are Bacteria and Archaea classified into separate domains?

An archaeon is found thriving in an extremely salty lake. It would most likely be classified as a:

Which statement best explains how fossils support the theory of evolution?

What does the fossil record reveal about the history of life on Earth?

Why are radioactive isotopes useful for determining the age of rocks?