Earth is tilted at a 23.5 degree angle. Explain how this causes the equator to be hot and the poles to be cold.

The organelle pictured is found in cells of and is theorized to have once been an independent organism.

Explain the difference between incomplete dominance and codominance

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?