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

[Q]: Passage: Imagine walking in the forest in Figure below . The towering trees have been growing here for hundreds of years. It may seem as though the forest has been there forever. But no ecosystem is truly static. The numbers and types of species in most ecosystems change to some degree through time. This is called ecological succession. Important cases of ecological succession are primary succession and secondary succession. Answer: ecological succession
[A]: The numbers and types of species in most ecosystems change to some degree through time and this is called?

[Q]: Passage: The cornea is the transparent outer covering of the eye. It protects the eye and also acts as a convex lens, helping to focus light that enters the eye. Answer: cornea
[A]: What is the transparent outer covering of the eye?

[Q]: Passage: The universe contains all the matter and energy that exists and all of space and time. We are always learning more about the universe. In the early 20th century, Edwin Hubble used powerful telescopes to show that some distant specks of light seen through telescopes are actually other galaxies. ( Figure below ) Hubble discovered that the Andromeda Nebula is over 2 million light years away. This is many times farther than the farthest distances we had measured before. He realized that galaxies were collections of millions or billions of stars. Hubble also measured the distances to hundreds of galaxies. Today, we know that the universe contains about a hundred billion galaxies. Answer: edwin hubble
[A]:
Who discovered that the andromeda nebula is over 2 million light years away