18.) When and by whom was the idea of a spherical Earth first developed?
O 1492 by Christopher Columbus
O 300 BC by philosophers in Ancient Greece
O hundreds of thousands of years ago by cavemen
O 1519 by Ferdinand Magellan

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.