Why is evolution considered a theory?

A. It was proposed by a scientist.

B. It cannot be proven.

C. It is a guess about what happened.

D. It is backed up by scientific evidence.

How many levels of structure are there in a protein with only one polypeptide chain?

Which is the most common type of arthritis, resulting from wear and tear of joints over the years?

Which body system is responsible for breaking down gluten?

Sierra decides to write down everything she likes to eat. Then, she draws branches under each animal on the list and writes everything they like to eat, and so on until she is down to all plants at the bottom of the page.

Which of the following is a major difference between binary fission and mitosis? Mitosis can only occur in sexually reproducing eukaryotes. In mitosis, two parents, or mother cells, are needed to initiate the process.

How would the lack of water affect cellular respiration?

Different types of normal tissues in the human body have different mitotic indices. From the following list, which normal tissues would you expect to have the highest mitotic index: muscle, skin, kidney, or lung? Explain your answer.

A group of scientists decided to post their research results on the Internet instead of publishing in a scientific journal. What part of the scientific process have they skipped and why does it matter?

How does the structure of DNA allow it to complete the process of replication?

Which of the four types of organic compounds serve as an energy source for cells?