What does Darwin's controversial book, On the Origin of Species by Means of Natural Selection, illustrate?
А
the importance of variations in organisms
B
that traits affect how likely an organism is to reproduce
C
how species evolve by adapting to their environment
D
all the above

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?