Given a scientific passage and an answer, generate a question for the given answer.

[Q]: Passage: Photosynthetic organisms include plants, algae, and some bacteria. Answer: photosynthetic
[A]: Plants, algae and bacteria are all examples of what type of organism?

[Q]: Passage: You can't go to the mantle but small pieces of the mantle can come to you. Kimberlite forms deep in the mantle and is erupted violently into the crust. Kimberlite can contain diamonds. Most kimberlites reached the surface much earlier in Earth history. Answer: crust
[A]: What is the upper most level of earth's layers called?

[Q]: Passage: Catalysts are not reactants, but they help reactants come together so they can react. You can see one way this happens in the animation at the URL below. By helping reactants come together, a catalyst decreases the activation energy needed to start a chemical reaction. This speeds up the reaction. Answer: activation energy
[A]:
A catalyst decreases the amount of what resource that is required in order to begin a chemical reaction?