What is true of carbon atoms?
a. they are not found in living organisms
b. they have five valence electrons
c. they can form up to four covalent bonds.
d. they do not bond with other elements.

The blue particles in this image are able to cross the cell membrane through simple diffusion. how will they be transported? outside the cell inside the cell o a. the substances will move directly across the membrane from outside the cell to inside the cell. b. the substances will move through channels in the membrane proteins from outside the cell to inside the cell. o c. the substances will move through channels in the membrane proteins from inside the cell to outside the cell. o d. the substances will move directly across the membrane from inside the cell to outside the cell.

Ivan is looking at a cross section of a stem taken from a vascular plant. he sees two different types of vascular tissue: the xylem, which is closer to the center of the stem, and the phloem, located around the xylem, closer to the outside of the stem. how do these two structures work together in a living plant?

The process of meiosis produces only gametes, eggs or sperm. according to the diagram, how many sperm are formed from each cell that undergoes meiosis?