Why are pioneer species usually autotrophs? A. Newly established ecosystems do not usually have pre-existing food sources.

B. Only autotrophs are large enough to survive.

C. Autotrophs are usually at the top of an ecosystem's food chain.

D. Only autotrophs can survive where water is scarce.

Which of the following statements is most likely correct about a rock belonging to the jurassic age and a rock belonging to the cambrian age? options: 1) they have identical fossils of organisms that have evolved over time. 2) both have animal fossils preserved in them due to weathering and erosion. 3) they contain different fossils because life on earth has changed through time. 4) the fossils in them were formed on the surface of earth due to exposure to sunlight.