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Plants and Society, 3/e
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Plants in Our Lives

Chapter Summary

1. Angiosperms, also called flowering plants, supply humanity with the essentials of life. The food staples of civilization—wheat, rice, and corn—are all angiosperms, as are almost all other food crops. Other angiosperm products that have shaped modern society include cloth, hardwood, herbs and spices, beverages, drugs, perfumes, vegetable oils, gums, and rubber.

2. The algae are aquatic, photosynthetic organisms that show a great diversity of form, ranging in size from the microscopic unicellular algae to gigantic seaweeds. They are important as components of aquatic food chains, contributors to the global photosynthetic rate, sources of a number of economically important products, and, in the case of algal blooms, can be detrimental to both the environment and the economy.

3. Fungi are also an economically important group of organisms. They include molds, mildews, yeast, and mushrooms. Fungi provide many beneficial items, such as penicillin, beer, wine, edible mushrooms, and leavened bread. A negative aspect of their economic importance is the impact of fungal disease and spoilage.

4. All living organisms have the capacity to grow and reproduce, the ability to respond, the ability to evolve and adapt, a metabolism, an organized structure, and organic composition.

5. Nine elements (carbon, oxygen, hydrogen, nitrogen, potassium, magnesium, calcium, phosphorus, and sulfur) make up 99.5% of living matter. The chemical nature of living matter is based on the element carbon and its ability to covalently bond to other carbon atoms to form the skeletons of carbohydrates, lipids, proteins, and nucleic acids—the molecules of life. Monosaccharides, especially glucose molecules, serve as sources of energy for cells; polysaccharides have storage and structural functions. Proteins, composed of long chains of amino acids, have many functions as enzymes, structural molecules, regulatory molecules, and transport molecules. Lipids are a diverse group of compounds that are insoluble in water. Some serve as energy reserves, others as structural materials or hormones. DNA serves as the hereditary material of life by encoding information in the sequences of bases. RNA functions in the manufacture of proteins by transcribing and translating information encoded in the DNA molecule.