You probably believe that Earth is spherical. But as we look around, it certainly appears that earth is flat. One classmate sugg
ests that if you call someone on the other side of the world by phone, they can verify that it is midnight there when it it noon here. Another student reminds you of the picture taken of the spherical Earth from the moon landing. You teacher explains the ancient observation that when the sun was directly over head on one day near the equator, a pole some hundreds of miles away to the north still cast a shadow. What, then, is the best scientific basis for considering that the Earth is spherical? A. If scientists say it, it must be correct until they determine otherwise.
B. Reasoning must be used to arrive at a model that best fits the observations.
C. If it is in a science book, it is known to be correct until another explanation is agreed upon and published.
D. The observation that Earth is flat is direct and objective, while all of the other observations are indirect, subjective, or based on extrapolated judgment.
A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke. Mutations can occur during DNA replication if errors are made and not corrected in time.
