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		Q. Why don't animals use this strategy? - animal cells may need all that cytoplasm to support a higher metabolic activity The combination of the cell wall (with high tensile strength) and water (relatively incompressible) inside forms a rigid structure. It's like putting a water balloon inside a box; plant cells are like bricks. This provides the rigidity for all non-woody parts to a plant, all the parts that wilt in drought. This saves energy. Cellulose is a glucose polymer; it takes much less energy to make cellulose than to make the proteins that form our internal skeleton or the chitin used in insect exoskeletons. III. Evolution of plants29.3 Plants are thought to have evolved from aquatic green algae and colonized the land. We will focus primarily on angiosperms, flowering plants that produce seeds.
		IV. Plant morphology vs anatomy There are 2 ways to look at plant structure: morphology-the external structure, and anatomy- the internal struucture			35.12
		A. Morphology(external structure based on functional units) Morphologists would subdivide the plant into functional units (1) the root systemis specialized for anchoring the plant in the ground and gathering water and minerals (2) the shoot system, made up of leaves, flowers and stems, is specialized for reproduction, gathering light and CO2, exchanging gases and photosynthesis