What holds the two strands of DNA molecules to each other. Hydrogen Bonds
Answer:
guard cells
Explanation:
they control the opening and closing of the stomata
The Paleozoic Era ended with the largest extinction event in the history of Earth, the Permian–Triassic extinction event. The effects of this catastrophe were so devastating that it took life on land 30 million years into the Mesozoic Era to recover
