Why must there be variation in a population in order for natural selection to occur?

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?

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.

Stephen is a student who wants to test his knowledge of medical terminology. which option could he use?