Unit E: Plant Biology Introduction to Plants 1. Identify the characteristics of the plant kingdom. Multicellular eukaryotes; cell walls made of cellulose; develop from multicellular embryos; the green pigments, chlorophyll a and b, carry out photosynthesis. 2. To live successfully on land, what substances must plants obtain from their environment? Sunlight, water and minerals, and oxygen and carbon dioxide. 3. From which group of protists did the first plants evolve? How are plants similar to these protists? Multicellular green algae; similar in size, color, appearance, reproductive cycles, cell walls and photosynthetic pigments. 4. Compare the gametophyte and sporophyte stages of the plant life cycle. Which is haploid? Which is diploid? Gametophyte: haploid, produces eggs and sperm by mitosis, formed from spores; Sporophyte: diploid, produces spores by meiosis, formed during fertilization with fusion of egg and sperm 5. Compare the roles of mitosis and meiosis in a plant life cycle. Which of these processes is related to sexual reproduction? To asexual reproduction? Mitosis: sexual reproduction; occurs in the haploid gametophytes to produce the haploid gametes. Meiosis: asexual reproduction; produces haploid spores in the sporophyte, which grow into the gametophyte. Structure and Function How do the cells of plants differ from those of animals? How are they different from those of fungi? You may whish to use labeled diagrams or a compare-and-contrast table to present your results. Refer to Chapters 7 and 21 for help in answering these questions. Bryophytes 1. How is water essential in the life cycle of a bryophyte? Bryophytes produce sperm that must swim through water to reach the eggs of others. 2. List the three groups of bryophytes. In what type of habitat do they live? Mosses, liverworts and hornworts; in moist, shaded areas. 3. What is the relationship between the gametophyte and the sporophyte in mosses and other bryophytes? The gametophyte is the dominant, recognizable stage and is the form that carries out most of the plant’s photosynthesis. The sporophyte depends on the gametophyte for water and nutrients. 4. What is an archegonium? An antheridium? How are these structures important in the life cycle of a moss? An archegonium is the reproductive structure that produces egg cells; an antheridium is the reproductive structure that produces sperm. These gametes fuse to form a diploid zygote, the beginning of the sporophyte stage. 5. What characteristic of bryophytes is responsible for their small size? Explain. Bryophytes are limited in size because they lack vascular tissue and therefore can draw only a few centimeters of water up from the ground by osmosis. Descriptive Writing You are writing a pocket field guide about plants and are working on the bryophytes chapter. Develop several paragraphs to help your readers distinguish among the mosses, hornworts and liverworts. Hint: Do additional library or internet research to find examples of bryophytes in your locality. Seedless Vascular Plants 1. What are the two types of vascular tissue? Describe the function of each. Xylem carries water from the roots to the rest of the plant. Phloem transports solutions of nutrients and the products of photosynthesis. 2. What are the three phyla of seedless vascular plants? Give an example of each. Lycophyta: club mosses; Arthrophtya: horsetails; and Pterophyta: ferns 3. What is the dominant stage of the fern life cycle? What is the relationship of the fern gametophyte and sporophyte? The diploid sporophyte; the gametophyte grows independently of the sporophyte. The young sporophyte grows from the gametophyte. 4. The size of plants increased dramatically with the evolution of vascular tissue. How might these two events be related? Plants without vascular tissue can draw up water by osmosis only a few centimeters above the ground. Vascular tissue moves fluids efficiently throughout a plant, even against gravity. The rigidity of vascular tissue also helps support a tall plant. 5. Explain why xylem and phloem together can be considered to be a transport system. Xylem moves water from roots to leaves and phloem moves nutrients from leaves to roots. Together they move materials throughout a plant, forming a transport system. Making a Visual Essay Find out more about club mosses, horsetails and ferns. Research information such as description, method of development, ecology and scientific name. Use this information along with photographs or drawings of these plants to create a two-page photo essay about seedless vascular plants. Seed Plants 1. Identify the main characteristics of seed plants. The ability to reproduce without water, the formation of cones or flowers, the transfer of sperm by pollination and the protection of embryos in seeds. 2. What are the different groups of gymnosperms? Gnetophytes, cycads, ginkgoes and conifers. 3. What major change in Earth’s climate favored the evolution of seed plants? Earth’s climate became much drier. 4. Pollination is a process that occurs only in seed plants. What process in seedless plants is analogous to pollination? In seedless plants, the swimming of the male gametes to the female gametes is analogous to pollination in seed plants. Comparing and Contrasting Compare reproduction in non-seed plants and seed plants. Then, explain how the evolution of the seed was critical to the success of gymnosperms and angiosperms. Angiosperms 1. What reproductive structures are unique to angiosperms? Briefly describe the function of each. Flowers and fruits; flowers attract pollinators; fruits protect the seed and aid in its dispersal. 2. What are monocots and dicots? Monocots have one seed leaf or cotyledon, in the plant embryo; dicots have two. 3. How do annuals, biennials and perennials differ? Annuals complete a life cycle within one growing season. Biennials complete their life cycle in two years. Perennials live for more than two years, usually many years. 4. Compare the growth forms of plants with woody stems and those with herbaceous stems. Plants with woody stems are trees, shrubs or vines. Plants with herbaceous stems include flowers such as zinnias and petunias. 5. Which are more likely to be dispersed by animals – the seeds of an angiosperm or the spores of a fern? Explain your reasoning. The seeds of angiosperms, because the seeds are enclosed in fruit, which animals eat. Creating a Display Prepare a display comparing two specific plants, one monocot and one dicot. On this display, show photographs or drawings of the plants and write a brief summary of the basic differences between these two types of angiosperms. Specialized Tissues in Plants 1. What are the three main organs of seed plants? Describe the structure of each. Roots: tissue to transport and anchor; stems: tissue for transport and to support leaves and branches; leaves: flat surfaces for light absorption 2. List the three tissue systems of plants. Describe how each tissue is distributed in stems, tissues and leaves. Dermal tissue: outermost layer of cells; vascular tissue: cells that transport water and nutrients throughout the plant; ground tissue: all other cells making up the plant 3. What two cell types make up xylem? Phloem? Tracheids and vessel elements; sieve tube elements and companion cells. 4. What is the function of meristematic tissue in a plant? Produces new cells by mitosis 5. In a stem that needs to support heavy leaves, what type of ground tissue might you expect to find? Sclerenchyma cells; they have thicker and harder cell walls that make ground tissue stronger. 6. Choose a group of cells making up vascular tissue in the root, the stem and the leaf. Compare these cells, showing how they are alike and different. The structure of cells making up vascular tissue in roots, stems and leaves is similar. However, the arrangement of the cells differs in each. Figure 23-1 shows this arrangement. Comparing and Contrasting You probably have some knowledge of the human circulatory system. Based on this knowledge, write a paragraph comparing and contrasting the vascular system of a plant to the human circulatory system. Hint: Show how the systems are alike and different. Roots 1. Compare a taproot and a fibrous root. Taproots: central primary root, grow deep; fibrous roots: shallow, many thin roots. 2. How are tissues distributed in a plant root? Roots have an outside layer of epidermal cells and a central cylinder of vascular tissue; between these lies ground tissue. 3. Describe the two main functions of roots. Anchor a plant in the ground and absorb water and dissolved nutrients from the soil. 4. How is osmosis involved in the absorption of water and nutrients? Active transport through the root epidermis results in a high concentration of mineral ions in the root cells that causes water molecules to move into the root by osmosis. 5. Analyze how a root is part of a plant’s transport system. Which parts of a root may be thought of as a subsystem? A root is the starting point for the movement of water through the vascular system. Subsystems: epidermis, cortex, endodermis, vascular cylinder 6. Why is it important that the root endodermis permit only a one-way passage of materials? The one-way passage of materials creates the root pressure that moves water up into the stem and leaves. Making a Diagram Make two diagrams, one showing a root’s structure and growth, the other showing how roots absorb water and nutrients. Label the diagrams and write brief descriptions of the processes shown in each. Stems 1. How do the functions of a stem relate to the roots and leaves of a plant? Stems transport substances between roots and leaves. 2. Describe how the arrangement of vascular bundles differs between monocot and dicot stems. Monocots: scattered throughout stem; dicots: arranged in a cylinder 3. Define primary and secondary growth. Which involves divisions of the apical meristem? Primary growth occurs only at the ends of plants. Secondary growth is a pattern in which stems increase in width. Primary growth involves the apical meristem. 4. How do heartwood and sapwood differ? Heartwood contains old, nonfunctioning xylem. Sapwood contains active xylem. 5. Analyze how a stem is part of a plant’s transport system. Which parts of a stem may be thought of as a subsystem? The stem conducts water and nutrients; xylem and phloem form a subsystem. 6. Evaluate the significance of the structural adaptations of the white potato. How does a tuber enable the plant to survive unfavorable conditions? The plant uses the food stored in the tuber for survival until favorable conditions return and the plant can make food again. Descriptive Writing Pretend that you are small enough to enter a plant through its root system. Describe what you would see as you traveled into a plant and through one of its stems. Include illustrations to enhance your description. Hint: Review the illustrations in this chapter for ideas. Reproduction with Cones & Flowers 1. What are the reproductive structures of gymnosperms? The reproductive structures of gymnosperms are pollen cones, pollen grains, seed cones, ovules and pollen tubes. 2. Describe the flower and how it is involved in reproduction. Flowers are reproductive organs that are composed of four kinds of specialized leaves: sepals, petals, stamens and carpels. The stamens produce male gametophytes, and the carpels produce female gametophytes. 3. Are angiosperms typically wind pollinated or animal pollinated? How does this process occur? Angiosperms are typically pollinated by animals. Insects, birds and bats carry pollen from one flower to another as they gather nectar. 4. What is endosperm? Where does it form in a flowering plant? A food-rich tissue that nourishes a seedling as it grows; inside the embryo sac. 5. Many flowers have bright patterns of coloration that directly surround the reproductive structures. How might this type of coloration by advantageous to the plant? Bright patterns of coloration might attract insects and other animals to the reproductive structures of the flower and increase the chances of pollination. Information and Heredity Review the life cycle of the green alga Chlamydomonas on Section 20-4. Make a compare-andcontrast table comparing alternation of generations in seed plants and Chlamydomonas. Include which stage (haploid or diploid) of each organism’s life cycle is dominant and when meiois occurs. Seed Development & Germination 1. Describe what happens as fertilized angiosperm seeds mature. Nutrients flow into the flower tissue and support the development of the embryo within the seed. Parts of the ovule toughen to form a seed coat, and the ovary wall thickens and joins with other flower parts to form a fruit that encloses and protects the seed. 2. Compare the typical structure of seeds that are dispersed by animals to those dispersed by wind and water. Seeds dispersed by animals typically have a tough coat and are contained in fleshy fruits. Seeds dispersed by wind and water typically are lightweight and may be encased in winglike structures. 3. Why is it adaptive for some seeds to remain dormant before they germinate? It allows for long-distance dispersal and for germination under ideal conditions. 4. The seeds of a bishop pine germinate only after they have undergone a forest fire. Evaluate the significance of this structural adaptation. It enables the species to recover after a fire and ensures that seedlings grow in a favorable environment. 5. Describe which adaptations of a seed would enable it to germinate in a vacant lot where a building once stood. Dispersal by wind and possibly animals. Writing a Book Imagine that you are writing a children’s book on seeds and that you are working on the chapter on dispersal. Write from one to three paragraphs on seed dispersal by wind. Hint: Try to include details that you would have found appealing when you were about 8 years old.