There are different types of observers. Casual observers differ from scientific observer. Seeing and observing are two different things. Not that everybody seeing is actually observing the thing.
A casual observer just sits back and watch for something to happen while a scientific observer comes up with some hypothesis to work on it.
Answer: To help researchers conclude that results are related to the new drug and not to the orange juice.
Explanation:
I could be wrong, Hope this helps
Pollution :) Since Abiotic means non living.
Bacteria: Living
Food (worms or smaller fish): Living
Predators: Living
Pollution (dirt, trash, or other stuff): Non Living
Answer:
Savanna do not exist in the united states because there are no true tropic climates.
4) digestive and circulatory, because the bladder is part of the digestive system. The circulatory system carries blood around the body using blood vessels.
