ASIM'S WEBWORLD View: Main School Main AP Biology Chapter Guides RELATED LINKS Chapter Outline		AP BIOLOGY: Chapter Thirty-Five Review Answers 1. The three tissue types are vascular tissue, including phloem and xylem, which are responsible for conducting materials through the plant; ground tissue, which functions in storage, photosynthesis and secretion; and dermal tissue, which is the outer protective covering of the plant. The shoot apical meristem develops into leaves and lateral branches; the root apical meristem grows continually downward as the root system of the plant; lateral meristems add girth to woody plants (and many herbaceous ones as well). 2. Angiosperms begin differentiation immediately after fertilization (in the embryo). In gymnosperms, the nuclei divide repeatedly, creating a large mass with no cell walls between the nuclei. After eight rounds of division, cell walls begin to form. After the walls have formed, the cells begin to undergo differentiation. 3. Growth of the embryo is usually arrested after the meristems and cotyledons are formed. Seeds are adaptively important because they permit the plant to postpone development until conditions are best for growth, allow synchrony of development with optimal weather conditions such as temperature and moisture, protects the young plant embryo, and facilitates dispersal. Many seeds may fail to germinate unless they are exposed to specific stresses, such as fire, the intestinal tract of an animal, or the leaching of specific materials from their seed coats. 4. Primary growth occurs in the apical meristems of roots and stems and is seen in herbaceous plants, shrubs, and trees. The change produced is elongation of the plant body. Secondary growth occurs in the lateral meristems. This tissue is found in the vascular cambium and cork cambium. The change produced by secondary growth is thickening of the plant body. 5. Annual plants grow to maturity and die in a single year; biennials grow to maturity and die in two years; perennials grow continuously (i.e., do not complete their life cycles within one or two years). Deciduous trees and shrubs lose their leaves on a cyclical basis, evergreens do not. Deciduous trees are encountered in many climates. Loss of leaves may be for conservation of water in times of drought in tropical regions. 6. A parenchyma cell is spherical with functioning cytoplasm, organelles, and nucleus with only primary walls. They are alive at maturity, which confers on them the capability to divide further. Collenchyma cells are elongated cells that form strands beneath the stems and leaf stalks; they are typically alive at maturity. The two types of sclerenchyma cells have tough, thick secondary cell walls, fibers that are elongated, and sclereids that are variable and often branched. They are found in supportive or mechanical tissue. They are not alive at maturity. 7. Xylem conduct water. Primary xylem are derived from procambium, apical meristem. Secondary xylem are derived from vascular cambium, lateral meristem. The conducting cells are tracheids and vessel elements. These cells are both elongated and fiberlike and not alive at maturity. Tracheids have pits in the secondary walls, and vessels have pits on the side walls and perforations in the end walls. Other cell types that are in xylem are fibers and parenchyma. 8. Phloem conducts food and contains sieve cells and sieve-tube members. They are slender and elongated, and lack nuclei. They are alive at maturity. Sieve areas are pores that connect protoplasts of adjoining sieve cells or sieve-tube members to one another. Sieve cells are less specialized; the pores in sieve areas are all the same size; sieve-tube members occur end to end, forming sieve tubes; and the larger pores in sieve areas are called sieve plates. Sieve-tube members are more evolutionarily advanced. Companion cells are specialized parenchyma cells associated with sieve-tube members; they carry out metabolic functions for the sieve-tube members. 9. A cross-section through a monocot root has bundles of xylem and phloem scattered throughout the section. The layers of a dicot root are epidermis (protection and root hairs), cortex (storage), endodermis (determines passage of water and minerals into vascular system), and pericycle (formation of lateral root). The Casperian strip is associated with the endodermis. Roots form lateral branches that are initiated deep within the root tissues through cell divisions in the pericycle. 10. The vascular cambium is in a cylinder around the stem between the main stem and the bark, and it initiates secondary growth. It is derived from both ground tissue and cells between the xylem and phloem of the primary vascular bundles. As the stem grows in diameter, phloem, xylem, and more cambium are produced. A girdled tree eventually dies because the vascular cambium is removed so water and nutrients cannot be transported. 11. The periderm is composed of the cork, cork cambium, and phelloderm. Cork cambium produces cork cells. Suberin is contained in these cells. This substance makes cork impermeable to water. These cells are dead at maturity. The tissue of bark includes all of the tissues in a mature root or stem outside of the vascular cambium. Removing the periderm does not equal girdling the tree because no vascular tissue is removed and of itself this will not kill the tree. The primary phloem ultimately becomes crushed among the layers of secondary phloem in the inner layers of bark. 12. Angiosperm leaves grow by their marginal meristems. This growth is determinate. Most leaves have a blade, stalklike petiole, stipules that may be present at the base of the petiole, and veins comprising vascular tissue. Simple leaves are undivided, and compound leaves consist of clearly divided leaflets. The three types of growth patterns of leaves are as follows: (1) alternate-leaves spirally arranged along the length of the stem;(2) opposite-leaves occur in pairs along the stem; and (3) whorled-more than two leaves are attached at any one level on a stem.