What must occur for a change in the environment to be considered a stimulus?

Hummingbirds drink nectar from flowers, while robins eat plant seeds. what does this reduce?

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.

If your blood becomes too concentrated with iona, what will happen to the red blood cells