Plants Study Guide for McGraw-Hill's ASVAB
Botany is the scientific study of plants. Many people consider everything from bacteria to the giant sequoia trees to be plants. That would include algae, fungi, lichens, mosses, ferns, conifers, and flowering plants. Today, scientists believe that bacteria, algae, and fungi have their own distinct kingdoms. The kingdom Plantae includes 250,000 species of mosses, liverworts, ferns, flowers, bushes, vines, trees, and other plants. Aquatic (water) and terrestrial (land) plants are the basis of all food webs. They emit into the atmosphere the oxygen that is needed by animals for survival.
Categorizing Plants Plants are categorized according to the structure by which the plant absorbs water. Plants are either vascular or nonvascular. Vascular plants transport water from the roots to the stems and to the leaves by means of tubelike structures. Nonvascular plants absorb water only through their surfaces.
Another way to categorize plants is according to how they reproduce. Some plants reproduce by producing seeds. Others produce spores. Yet another way to categorize plants is by whether they produce flowers (angiosperms, such as roses or apple trees) or don't produce flowers (gymnosperms, such as pine trees). Seeds store food for the growing plant; the part of the seed that stores the food is called the cotyledon. Some seeds have one cotyledon and are called monocots. Others have two and are called dicots.
Plants can also be classified by their life cycle. Annuals go through their entire life cycle, from germination through seed production to death, in one growing season. Corn, zinnias, beans, marigolds, and mums all have to be planted each year. Biennials have a two-year growing cycle. In year one, the seed germinates, produces leaves and roots, and forms a compact stem for food storage. In year two, the plant forms an elongated stem, produces flowers and fruits, and then ends with seed production. After seed production, the plant dies. Examples are onions, raspberries, hollyhocks, and carrots. Perennials live for many years. Parts of the plant may die back during the winter, but the plant will grow back in the spring.
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