10. Use your understanding of natural selection to describe how the following trait might have evolved: a. Plants have pores on the surfaces of their leaves that allow carbon dioxide into the leaf (for photosynthesis), but also allow water to escape. Land plants have guard cells surrounding these pores that actively regulate the size of the pore and will make the pore smaller in dry conditions. The ancestors of land plants did not have guard cells.
The ancestors of the land plants did not have guard cells because their environment was... View the full answer