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Transcript
AP Biology, Chapter 29 Plant Diversity I: The Colonization of Land SUMMARY INTRODUCTION AN OVERVIEW OF PLANT EVOLUTION Structural, chemical, and reproductive adaptations enabled plants to colonize land 1. Summarize the terrestrial adaptations of plants. a. Apical meristems for longitudinal growth of subterranean and aerial organs b. Embryophytes: multicellular, dependent embryos retained by the female c. Alternation of generations with a dormant, resistant spore stage d. Waxy cuticle and gas exchange through stomata for water conservation e. Xylem and phloem for distribution of water+mineral and organic products f. Secondary biosynthetic products: tannins, lignins, sporopollenin 2. Define and distinguish between the stages of the alternation of generations reproductive cycle. Compare the life cycle of humans with alternation of generations. a. Stages i. Sporophyte: multicelluar diploid that performs meiosis ii. Haploid spores grow by mitosis into gametophyte iii. Gametophyte makes gametes iv. Gametes fuse to form diploid zygote v. Zygote divides by mitosis to form sporophyte b. Human haploids do not grow by mitosis into a multicellular organism The history of terrestrial adaptation is the key to modern plant diversity 3. Describe the four great evolutionary episodes in the history of land plants. a. Ordovician, 475 mya i. Charophytes land plants ii. Sporopollenin, jacketed gametangia, vascular tissue b. Early Devonian, 400 mya i. ferns ii. Seedless vascular plants c. Late Devonian, 360 mya i. gymnosperms ii. Seeds d. Cretaceous, 130 mya i. angiosperms ii. Seeds protected in ovaries 4. Distinguish between the four main groups of land plants. a. Bryophytes i. Mosses and liverworts ii. Seedless and avascular with primitive tissues b. Pteridophytes i. Ferns, lycophytes, horsetails ii. Seedless with an independent gametophyte c. Gymnosperms i. Conifers, ginkgoes, cycads ii. Cone-bearing, seeds not enclosed in a flower or fruit d. Angiosperms i. Flowering plants ii. Seeds enclosed in fruit THE ORIGIN OF PLANTS Plants probably evolved from green algae called charophytes 5. Describe five shared derived homologies that link charophyceans and land plants. a. Homologous chloroplasts: pigments, stacked thylakoids, DNA sequence, # of membranes b. Biochemical similarity: cell wall composition, peroxisomal enzymes c. Mitosis and cytokinesis i. Nuclear membrane disassembly ii. Spindle persists until cytokinesis iii. Cell plate for cytokinesis in some charophytes d. Similar sperm ultrastructure e. Genetic relationship: nuclear and rRNA sequences Alternation of generations in plants may have originated by delayed meiosis 6. Describe a likely hypothesis for the origin of alternation of generations in plants. a. No multicellular alternation of generations in modern charophytes i. Multicellular form is haploid ii. Fertilization takes place on the haploid iii. Meiosis immediately follows b. Hypothesis i. Zygote divides by mitosis before meiosis ii. Advantage: more cells available for meiosis Adaptations to shallow water preadapted plants for living on land 7. Explain how adaptations of charophycean algae to shallow water preadapted plants for life on land. a. Sporopollenin protects spores b. Protective sheath on oogonium 8. Distinguish between the kingdoms Plantae, Streptophyta, and Viridiplantae. Note which of these is used in the textbook. [6th edition] a. Plantae: land plants; embryophytes (used in the 6th edition) b. Streptophyta: embryophytes + charophyta c. Viridiplantae: embryophytes + charophyta + chlorophyta BRYOPHYTES The embryophyte adaptation evolved in bryophytes 9. List and distinguish between the three phyla of bryophytes. Briefly describe the members of each group, note their common names, and indicate which phylum represented the earliest plants. a. Bryophyta i. Feathery with thin sporophyte stalks topped with sporangium ii. Commonly called mosses (ex. "peat") b. Hepatophyta i. Lobed with gemmae cups for asexual reproduction ii. Commonly called liverworts c. Anthocerophyta i. Sporophytes horn or spike-shaped ii. Commonly called hornworts (ex. Sphagnum) iii. These are most closely related to fully vascular plants The gametophyte is the dominant generation in the life cycle of bryophytes 10. Describe the structure of the sporophyte and gametophyte stages of bryophytes. Explain why most bryophytes grow close to the ground. a. Sporophyte i. Thin stalk or spike tipped with sporangium ii. Grow up out of the archegonium after fertilization b. Gametophyte i. Dominant form ii. Green with small leaflike, stemlike, and rootlike (rhizoids) parts iii. Lacks well-developed vascular tissue and supporting tissue iv. Can't transport water very far 12. On a diagram the life cycle of a bryophyte, label the gametophyte and sporophyte stages and the locations of gamete production, fertilization, and spore production. a. See 5th edition, page 553 The three divisions of bryophytes are mosses, liverworts, and hornworts 13. Describe the ecological and economic benefits of bryophytes. a. Form habitats of tiny animals b. Pioneer species; helps soil formation c. Store carbon d. Mined for fuel and for use as a soil amendment THE ORIGIN OF VASCULAR PLANTS Introduction Additional terrestrial adaptations evolved as vascular plants descended from bryophyte-like ancestors 14. Describe the adaptations of vascular plants, including modifications of the life cycle and modifications of the sporophyte, that have contributed to their success on land. a. Dominant sporophyte generation b. Modifications i. Branched sporophyte for producing more spores ii. Vascular tissue with chains of cells including xylem with lignified walls The branched sporophytes of vascular plants amplified the production of spores and made more complex bodies possible SEEDLESS VASCULAR PLANTS Introduction A sporophyte-dominant life cycle evolved in seedless vascular plants 15. Distinguish between homosporous and heterosporous conditions. a. Homosporous: one type of spore, bisexual gametophyte (ex. ferns) b. Heterosporous: micro- (male) and mega- (female); separate gametophytes 16. Explain why seedless vascular plants are most commonly found in damp habitats. a. Swimming sperm b. Fragile gametophytes The three divisions of seedless vascular plants are lycophytes, horsetails, and ferns 17. Compare the structures of lycophytes, pteridophytes, and sphenophytes. a. Lycophytes i. Large (40 m) woody trees in the fossil record ii. Currently prostrate hebaceous vines and epiphytes iii. Simple, microphyll leaves; sporangia on stalks iv. Separate gametophyte; non-photosynthetic; persistent, relies on mycorrhizae b. Sphenophytes (horsetails) i. Once very diverse; fossil forms to 15 m ii. Reduced to 15 species; now found in swampy areas ii. Green jointed stems with tiny leaves iii. Stem tip cones harbor sporangia c. Pteridophytes i. Ferns, whisk ferns, and horsetails ii. Well-developed roots with lignified vascular tissue iii. Complex megaphyll leaves; sori are clusters of sporangia on leaf bottoms 18. Describe the production and dispersal of fern spores. a. Each sorus on the leaf bottom is a cluster of sporangia b. Springlike devices hurl spores c. Spores are small enough to be blown by the wind 19. Describe the major life cycle differences between mosses and ferns. a. Ferns have a separate sporophyte stage b. Fern sporophyte is larger c. See fern life cycle, 5th edition, page 556 Seedless vascular plants formed vast "coal forests" during the Carboniferous period 20. Explain how coal is formed and note during which geologic period the most extensive coal beds were produced. a. Formation i. Anoxic swamps limited decay ii. Dead plants built up and were heated and compressed b. Geologic period: Carboniferous, 290-360 mya