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EXPLORING LIFE EXERCISE 6: SEED PLANTS Exercise 6: Seed Plants Workbook Contents Corresponding Section on CD Vocabulary Key Concepts Introduction 1. Introduction Seeds 2. Seeds Differences Between Gymnosperms and Angiosperms 3. Difference Between Gymnosperms and Angiosperms Pine Vegetative Body 4. Pine Vegetative Body Pine Reproduction 5. Pine Reproduction The Cycads, Ginkgo and the Gnetophyta 6. The Cycads 7. Gingko 8. The Gnetophyta Division Anthophyta: The Flowering Plants 9. Division Anthophyta: The Flowering Plants 9A. Introduction 9B. Flowers 9C. Fruits Introduction Flowers Fruits Summary & Review Vocabulary Accessory fruit - A fleshy fruit containing ovarian and non-ovarian tissue, e.g. an apple Achene - A simple dry indehiscent fruit derived from an inferior ovary in which the seed occupies most of the volume of the fruit and the seed coat does not adhere to the pericarp Aggregate fruit - A fruit derived from many pistils in the same flower Angiosperms - Flowering plants Anther - That part of a stamen that produces pollen Anthophyta - The division of flowering plants Antipodals - Haploid cells of the female gametophyte of angiosperms found at the end of the gametophyte opposite the micropyle Berry - A simple fleshy fruit with multiple seeds and derived from more than one carpel, e.g., a grape Bract - A modified leaf usually smaller than normal vegetative leaves Calyx - The whorl of sepals Carpel - The smallest segment of a pistil that encloses ovules Cleistogamy - A breeding system in which a flower is pollinated by its own pollen before the flower opens 6-1 Coleoptile - A sheath enclosing the shoot of grasses in the seed. This sheath penetrates the soil in advance of the shoot. Coleorhiza - The sheath that encloses the root of grasses Corolla - The whorl of petals Cotyledon - Seed leaf Dicotyledons - One of the two major groups of angiosperms characterized by having two cotyledons Dioecious - Species composed of unisexual individuals, i.e., staminate and pistillate plants Drupe - A simple fleshy fruit that has a thin ectocarp, a fleshy mesocarp, and a hard stony endocarp and is usually a single seed, e.g., a peach Ectocarp - The outer layer of the pericarp. The differentiation of the pericarp into three layers is common in fleshy fruits but not dry fruits. Endocarp - The inner layer of the pericarp of a fleshy fruit Endosperm - A distinctive nutritive tissue found only in angiosperms. The endosperm results from the fusion of a sperm with the polar nuclei and consequently usually has an odd ploidy number. Epicotyl - The upper portion of the embryo from which the shoot is derived Epigynous - Refers to a flower that appears to arise from a point above the ovary Filament - The stalk supporting an anther Follicle - A simple dry dehiscent fruit that splits only along one axis Funinculus - The stalk supporting an angiosperm ovule Gymnosperms - Naked seeded plants Hypocotyl - That portion of the embryo below the cotyledons Hypogynous - Refers to a flower in which the ovary is above where the other floral whorls attach to the stem Integuments - One of two pairs of leaves that surround the nucellus Legume - Dehiscent fruit formed from one carpel that splits along two axes Mesocarp - The middle portion of a fleshy pericarp, i.e., between the ecto- and endocarps Micropyle - The opening between the integuments of seed plants Monocotyledons - One of the two major groups of angiosperms characterized by the presence of one seed leaf Monoecious - An individual that produces both pistillate and staminate flowers Nucellus - Megasporangium of seed plants Nut - A dry indehiscent fruit derived from a compound ovary and having a hard pericarp Ovule - An ovule is composed of the integuments, nucellus and a female gametophyte of seed plants. A seed develops from a fertilized ovule. Ovuliferous scale - The modified leaf that bears the ovules of some gymnosperms Pepo - A modified berry having a hard rind for an ectoderm, e.g., a watermelon Pericarp - The fruit wall. The pericarp is derived from the ovary wall. Pistil - A single carpel or a fused group of carpels that function as a unit Polar nuclei - Two or more haploid nuclei in the angiosperm embryo sac that migrate from either pole to the center of the sac where they are fertilized by a sperm. The resulting polyploid tissue becomes the endosperm. Pollen grains - The immature male gametophytes of seed plants Protandry - A breeding system characterized by the stamens maturing before the pistils Prothallial cell - A cell in the male gametophytes of seed plants that does not directly participate in reproduction Protogyny - A breeding system characterized by the pistils maturing prior to the stamens Radicle - The portion of the embryo that becomes the root Seed - A mature fertilized ovule Sepal - A modified leaf found in the lowest whorl of a flower Stamen - The male or pollen producing structure of flowers Synergids - A pair of haploid cells on either side of the egg in an angiosperm ovule Tapetum - A nutritive tissue found in the microsporangium of angiosperm anthers Tube cell - The haploid cell in the male gametophyte of seed plants that directs the growth of the pollen tube. In the Anthophyta, it is only a haploid nucleus, not a separate cell. Whorl - Three or more leaves or modified leaves that occur at the same node 6-2 KEY CONCEPTS This section of the workbook is set up to help you note important information relating to the key concepts of this exercise and then organize and summarize the information in order to develop a synthesis and prepare for a review. As you complete this exercise, you will focus on the characteristics of various plant tissue types so that you will be able to distinguish: Seeds 1. What is a seed? 2. How does a seed develop? Gymnosperms and Angiosperms 3. What are the similarities/differences between these two groups? 4. What are some specific structures of gymnosperms? angiosperms? 5. How do gymnosperms reproduce? 6. What are some of the different groups of gymnosperms? How are they alike? How are they different? 7. What are the reproductive structures of angiosperms? How do they function? The first eleven pages are questions that can be answered by following the progression of slides and paying careful attention to the information, both visual and audio. These questions should be read in advance of each section so that you can be better prepared to answer them by knowing what you are looking for. The underlined subheadings correspond to the sections of the exercise as outlined in the main menu. The subsequent pages are designed to help you summarize and synthesize the pertinent information to answer the questions posed above. These are followed by a review quiz. 6-3 SEED PLANTS Introduction 1. Match the plant groups with their common names and seed characteristics: gymnosperm flowering plants seeds naked upon cone scale angiosperm naked seed plants seeds found inside fruits Seeds 2. In nonseed-producing tracheophytes, the gametophyte / sporophyte is the dominant stage and the gametophyte / sporophyte is independent of the dominant stage. Air / Animals / Water is/are needed for fertilization to occur. 3. Seeds plants, like non-seed plants, are heterosporous / homosporous, forming both megaspores and microspores / only megaspores / only microspores, which develop into male and female gametophytes, respectively. 4. Label each of the following phrases as a characteristic of non-seed (N) or seed-producing (S) plants: both megaspores and microspores fall to ground, where gametophytes develop female gametophyte is retained in tissue of sporophyte, up in the air male gametophyte reduced to pollen grain, moved by wind, water or animal sperm swim from one plant to another; fertilization tied to availability of free water internal fertilization; sperm do not need to swim and so some do not have flagella no internal fertilization; sperm need to swim and so need to have flagella Differences Between Gymnosperms and Angiosperms 5. What are the traits that all seed plants share? List at least three: 6. The most consistent difference between the two groups involves the development of the 7. Label the following diagram. Be sure to use the terms: egg, synergid, antipodals, polar nuclei, nucellus 6-4 . KEY CONCEPTS 8. In the development of the male gametophyte, how many sperm are formed? What do each of these sperm do? What do the fertilized polar nuclei develop into? 9. All / Most angiosperms produce an endosperm; they all also have double / single fertilization. On the other hand, all / most / no / only one genus/genera of gymnosperms has double fertilization, and only some / no endosperm is developed. 10. Mark each of the following statements (A) for angiosperms and (G) for gymnosperms: nucellus surrounded by two pairs of integuments produce tracheids in their xylem nucellus surrounded by one pair of integuments produce vessels in their xylem all members of this group woody; none are herbaceous produce cones members of this group can be woody or herbaceous produce true flowers Pine Vegetative Body . Some are deciduous / 11. The first group of gymnosperms in this exercise is the evergreen and keep their leaves year-round, while others are deciduous / evergreen and lose their leaves. 12. Circle which of the following conifer plant organs is woody: cones leaves roots stems 13. Label the following on the diagrams below: tracheid, pit, resin duct. Why are the cell walls of the tracheids so thick? Are these cells alive or dead ? What is their function? 14. Describe the function of the resin duct. How has this system helped our understanding of prehistoric life? 6-5 SEED PLANTS 15. Label the following diagrams with the terms: xylem, phloem, sieve area. The conducting cells of the phloem have only a primary / primary and secondary cell wall(s). When mature, sieve cells have cytoplasm / have no cytoplasm and have a nucleus / lack a nucleus. A neighboring cell called a(an) albuminous cell / companion cell regulates the sieve cell’s cytoplasm. 16. Label the diagram with these terms: xylem, phloem, vascular cambium, bark. When the cambium divides, the daughter cell may remain in line and become cambium / phloem / xylem, get pushed inside and become cambium / phloem / xylem, or get pushed outside and become cambium / phloem / xylem. This action is called primary / secondary growth, which all / most gymnosperms exhibit. The epidermis / periderm of the young plant will be lost and will be replaced by epidermis / periderm. Which two tissues form the bark of the pine tree? 6-6 KEY CONCEPTS 17. What are pine leaves called? 18. Connect the following terms to its place on the diagram and its definition (you may want to wait until the last segment of this exercise, when most of the structures are labeled all at once; then repeat as needed). cuticle gas exchange hypodermis helps reduce loss of water from stomata resin duct composed of wax to help retain water endodermis second skin inside epidermis phloem photosynthetic tissue xylem third or inner skin transfer tissues help transfers to and from vascular system mesophyll water-conducting vascular tissue stomata sugar-conducting vascular tissue chamber exudes substance to deter and trap insects Pine Reproduction 19. Label each of the following statements as belonging to male (M) or female (F) pine cones: microsporangiate; usually smaller borne on lower branches megasporangiate; usually larger borne on upper branches 20. How and why are male and female cones spatially separated? 21. Label the diagram and describe the arrangement and number of structures in the male cone. Be sure to include the terms microsporophyll, microsporangium, mother cells 6-7 SEED PLANTS 22. Number the following steps (from 1 to 11) in the order that they occur: body cell undergoes mitosis and forms 2 sperm microspore mother cell undergoes meiosis each microspore undergoes 2 mitotic divisions one sperm fertilizes egg four microspores are formed pollen grain produces two wings generative cell divides to form stalk and body cell pollination occurs sperm carried to egg by pollen tube male gametophyte is formed tube cell starts to produce pollen tube 23. Connect these terms to the diagram: ovuliferous scale bract ovule funiculus nucellus 24. Number the following steps (from 1 to 18) in the order that they occur: cell walls form in female gametophyte pollen grain is captured four cells in layer furthest from micropyle develop into separate embryos pollen tube grows pollen tube reaches archegonium four megaspores formed in a line remaining megaspore divides by mitosis layer below four embryos elongate and push embryos into female gametophyte single egg formed by each archegonium sperm discharged into egg cytoplasm megagametophyte (with 2000 nuclei) formed surviving embryo develops four layers of cells three megaspores farthest from micropyle break down megaspore undergoes meiosis micropyle exudes pollen droplet two embryos form from fertilized ovules one sperm fertilizes egg; other disintegrates two to three archegonia develop 6-8 KEY CONCEPTS 25. Match the following terms to the diagram: cotyledons apical meristems hypocotyl root axis root apical meristem female gametophyte seed coat The Cycads, Ginkgo and the Gnetophyta form endosperm do not form endosperm double fertilization single fertilization produce flowers produce stroboli sperm do not have flagella sperm have flagella deciduous leaves with parallel veins insect pollinated wind pollinated dioecious have vessels have tracheids wide range/habitats restricted range/habitats 26. Mark an “X” in the boxes that correspond to characteristics found within each group. Example organism(s) Conifers Cycads Gingko Gnetales Angiosperms Division Anthophyta: The Flowering Plants Introduction 27. True or False: The flowering plants are the largest group of plants ever. True or False: The flowering plants are the least diverse group of plants ever. True or False: The flowering plants are the most successful group of plants ever. True or False: The flowering plants group has a narrow range of sizes. True or False: All flowering plants have single fertilization, an endosperm, flowers, fruits and seeds. True or False: All flowering plants possess tracheids in their xylem and sieve tubes in their phloem. 6-9 SEED PLANTS Flowers Flower Structure 28. Match the whorl number with the whorl name and structures found in that whorl: Whorl Name Structures 1 calyx anthers and filaments 2 corolla carpels and ovules 3 pistils petals 4 stamen sepals Whorl Number 29. Label the following structures on the flower diagram: sepal, calyx, petal, corolla, perianth, stamen, filament, anther, pistil. You may need to repeat this section of the CD several times to complete this question. Flowers – Male Reproductive Structures 30. Match the following structures to this anther cross-section: locule mother cells tapetum 6-10 KEY CONCEPTS 31. Number the following steps (1 to 11) in the order in which they occur: anther walls split open coating is deposited on the pollen grains generative cell and tube nucleus are formed generative cell divides by mitosis haploid microspores are produced microspores divide by mitosis mother cells undergo meiosis pollen grain lands on receptive surface pollen is dispersed tube nucleus produces a pollen tube two non-flagellated sperm are produced Flowers – Female Reproductive Structures You will have to view this section several times to completely answer the questions for this section. 32. Label the structures on the ovule: outer integument antipodals inner integument polar nuclei nucellus synergids funiculus egg embryo sac micropyle 33. How many pair of integuments do gymnosperms have? How many do angiosperms have? 34. Number the following steps (1 to 10) in the order in which they occur: one sperm fertilizes polar nuclei; endosperm forms endosperm breaks down to nourish embryo female gametophyte (embryo sac) forms pollen tube penetrates embryo sac through the micropyle four megaspores are formed megaspore continues to divide remaining megaspore divides megaspore mother cell divides sperm are deposited in pollen tube one sperm fertilizes egg; zygote forms three megaspores disintegrate 6-11 SEED PLANTS Flowers – Structure Modifications 35. Label the following structures on the flower diagram: carpel, stigma, style, ovary, ovules. 36. Once the ovules are fertilized and become fruit / seeds, the ovary will become the fruit / seeds. 37. Match each ovary type with the correct flower type and placement of the perianth in relation to the ovary: Ovary Type Flower Type Placement of Perianth superior epigynous perianth fusion to stem above ovary inferior hypogynous perianth fusion to stem around ovary perigynous perianth fusion to stem below ovary 38. Wind pollinated flowers typically are missing one or both ovary / perianth parts. Why? 39. True or False: Wind pollinated flowers are usually devoid of any attractive device. 40. Match the flower type with its description (one description matches with two of the flower types): Flower Type Description complete flower has stamens or pistils, but not both imperfect flower has all four whorls incomplete flower is lacking one or more whorls perfect flower has stamens and pistils unisexual 6-12 KEY CONCEPTS Flowers – Inflorescences 41. What are the branches that bear flowers called? Flowers – Pollination 42. What has affected the size, color and shape of flowers? 43. Most flowering plant species are pollinated by animals / wind, and most plants use as an attractant. Label the following colors by the animals that are attracted to them: hummingbirds (H), bees (B), moths and bats (MB). blue orange red ultraviolet violet white yellow 44. List at least three of the other attractants plants use: 45. What do animals get from this relationship? What do plants get? 46. Animal / Wind pollinated plants produce nectar and pollen while animal / wind pollinated plants produce only nectar / pollen. 47. True or False: When a flower’s own pollen lands on its stigma, this self-pollination leads to selffertilization and is called cleistogamy. True or False: When a plant’s own pollen lands on the stigma of one of its flowers, this is called dichogamy. 48. Why to plants usually want to avoid self-pollination and self-fertilization? 49. Mark the following statements (D) for dioecious or (M) for monoecious: male & female flowers on separate plants flowers are perfect male and female flowers on same plants examples include box elder, aspen and willow flowers are imperfect examples include cucumbers and watermelon 50. If stamens and pistils on the same flowers are not functional at the same time, it is called . These flowers are imperfect / perfect. If the stamens mature before the pistils, it is called protandry / protogyny, while if the pistils mature before the stamens it is called protandry / protogyny. 6-13 SEED PLANTS 51. What mechanisms allows self-pollination but not self-fertilization? Fruits 52. What is the function(s) of the fruit? What structure is modified to form the fruit? multiple seeds per fruit one seed per fruit fleshy endocarp hard endocarp dry mesocarp fleshy mesocarp thick ectocarp (rind) thin ectocarp fruit is from the stem fruit from multiple ovaries fruit from single ovary fruit from many flowers Fleshy Fruit Type simple drupe accessory berry pepo aggregate of drupe of accessory multiple fruit from one flower 53. Mark an “X” in the boxes that correspond to characteristics found within each group. example fruits do not split (indehiscent) split in different ways split along one axis split along two axes dehiscent fruit from multiple ovaries Dry Fruit Type legume follicle capsule achene caryopsis fruit from single ovary 54. Mark an “X” in the boxes that correspond to characteristics found within each group. example fruits 6-14 KEY CONCEPTS 55. Label the following characteristics (D) for dicot and (M) for monocot. one cotyledon (scutellum) true root replaced by adventitious root two cotyledons (seed leaves) seed surrounded by seed coat epicotyl forms stem and leaves little endosperm left in seed embryo forms radicle, coleoptile and coleorhiza much endosperm left in seed floral parts in multiples of three embryo forms true root floral parts in multiples of 4 or 5 6-15 SEED PLANTS 1. What are the major differences between non-seed and seed-producing plants? Be sure to examine their structure, reproduction and life cycle and include such terms as sporophyte, gametophyte, pollen grains, sperm, internal fertilization, and flagella in your discussion. 2. In what ways are all seed-producing plants the same? 3. In what ways are gymnosperms and angiosperms different? 4. What characteristics link all gymnosperms? What characteristics link most gymnosperms? What characteristics are unique to the conifers? What characteristics are unique to the cycads? What characteristics are unique to the ginkgos? What characteristics are unique to the gnetales? 5. What characteristics link all angiosperms? 6. What characteristic of fertilization has enabled seed-producing plants to colonize dry land? 6-16 SUMMARY AND REVIEW 7. Circle the flowers that are complete. Draw a box around the flowers that are incomplete. Draw a solid headed arrow ( ) to the flowers that are perfect. Draw a non-solid headed arrow ( ) to the flowers that are imperfect. 8. Can flowers be imperfect and complete? Explain: Can flowers be perfect and incomplete? Explain: 9. Describe some of the ways flowers are pollinated and the characteristics that each type of flower has: 10. Describe some of the ways in which flowers avoid self-pollination and self-fertilization: 6-17