One theory of early life on Earth states that the first life forms did not use oxygen for respiration and were unable to make their own food. Based on this theory, which types of organisms were most likely present? * A. aerobic, autotrophic bacteria
B. anaerobic, autotrophic bacteria
C. aerobic, heterotrophic bacteria
D. anaerobic, heterotrophic bacteria

Which prefix mean under less or below

True or false: (a) the strings of little red dots represent carbohydrates. (b) the model is called a bilayer because there are two main types of molecules present, lipids and proteins. (c) the many black lines represent amino acid tails. (d) this model shows membrane transport. (e) the blue ovals are hydrophobic. (f) the blue ovals represent phospholipid heads.

Why do mountaineers become breathless as they reach high altitudes