chapter29&30 - 1 what evidence is there for the...

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1. what evidence is there for the theory that charophyceans are most similar to the ancestors of modern plants? Charophyceans contain rose-shaped arrays of proteins that synthesize the cellulose in the cell walls. These rosette-cellulose-synthesizing complexes contrast the linear arrays of cellulose-producing proteins in noncharophycean algae. This difference suggests that cellulose walls of an ancestor common to charophyceans and land plants evolved independently of the cellulose walls of other algae. The function of the enzymes contained within peroxisomes is another similarity between charophyceans and land plants. The enzymes help minimize the loss of organic product from photorespiration. The flagellated sperm cells in both charophyceans and land plants are also a fundamental similarity. During cell division both types use phragmoplasts, vesicles from the golgi filled with cell wall material, used to build cell walls. Charophyceans and land plants also have similar DNA and protein sequences further exhibiting their similarities. 2. What particular problems did land plants face? What specific adaptations have helped them survive? Plants have adaptations for conserving, transporting and acquiring water. The epidermis of leaves is coated with a cutile, a layer of polyesters and waxes. The coating helps protect the plant from microbial attack and acts as waterproofing, which helps prevent excessive water loss. The stomata are the main system by which water exits the leaves. The guard cells, boarding the stomata, change shape in order to close the pores, minimizing water loss. Xylem and Phloem are two types of tissues that conduct materials in the plant’s vascular system. Water-conducitng cells, that are in fact dead, remain to provide a system of tube-shaped water pipes in the xylem that carry water and minerals up from the roots. Phloem is a living tissue with nutrient-conducting cells that distribute sugars, amino acids, and other organic products. Land plants produce unique molecules called secondary compounds as a means of protecting themselves. Various alkaloids, terpenes, and tannins have bitter tastes, strong odors, or toxic effects that help
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chapter29&30 - 1 what evidence is there for the...

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