Introduction to Plants PPT
- 1. By: Elaine Wang and Ananya Murali
- 2. Introduction: Pioneers In a New World • Transition from water -> land began in the precambrian period with cyanobacteria (green algae) • Developed into world’s 1st plants • Adaptations necessary for survival on land - Obtaining and preserving water - Reproduction
- 3. 23.1: Trends In Plant Evolution • Vascular plants: most diverse plants w/ internal tissue systems that conduct water and solutes through roots, stems and leaves • Seedless vascular plants: whisk ferns, lycophytes, horsetails, ferns • Gymnosperms: seed-bearing vascular plants – Cycads, ginkgos, gnetophytes, conifers • Angiosperms: vascular plants w/ flowers and seeds – Magnoliids, eudicots, monocots • Bryophytes: nonvascular plants – Liverworts, hornworts, mosses • Root systems: underground absorptive structures of a cumulatively large surface area – Rapidly take up soil water and mineral ions – Anchor for plants • Shoot systems: stems and leaves absorb energy from sun, CO2 from the air – Developed taller/branched stems after developing the capacity to synthesize/deposit lignin in cell walls • Xylem: vascular tissue that distributes water and dissolved ions in plants • Phloem: vascular tissue that distributes dissolved sugars and other photosynthetic products
- 4. 23.1: Trends In Plant Evolution • Cuticle: protective waxy coat that helps conserve water on hot, dry days • Stomata (stoma): tiny openings across surfaces of leaves and some stems to control CO2 absorption and restrict evaporative water loss • Gametophytes: gamete-producing bodies that dominate the haploid phase of algal life cycles – mostly aquatic plants • Sporophyte: multicelled diploid plant body • After a diploid zygote undergoes mitosis->Forms spores: haploid resting cells – fertilization could be timed with suitable environmental conditions – Diploid dominance is an adaptation to land • Heterospory: plants that produce 2 types of spores (both seedless an seed- bearing) • Homospory: plants that produce one type of spore • Pollen grains: cellular structures that become mature, sperm-bearing male gametophytes – Microspores that reach eggs via air currents, insects, and birds – Contributed to radiation of seed-bearing plants to high/dry habitats • Seed: an embryo sporophyte, nutritious tissues, and outer coat; Developed from female gametophytes
- 5. 23.2: The Bryophytes • Species of mosses, liverworts, hornworts – Adapted to moist habitats – Mosses, however, can be found in deserts as well • Sensitive to air pollution • Most common • Nonvascular: leaf/stem/root parts lack a xylem or phloem – Instead, have rhizoids: elongated cells/threadlike absorptive structures that attach the gametophytes to the soil, and absorb water and minerals • Show three features that were adaptive during the transition to land – 1. Cuticle: stomata to prevent water loss – 2. Cellular jacket around parts that produce sperm/eggs: holds in moisture – 3. Embryo sporophyte: sporophytes that begin life inside a female gametophyte • Sporophytes remain attached to the gamete-producing body for nutrition (do not disperse) • Mosses (most common) – Gametophytes grow in clusters to form cushiony mounds, or grow in branched patterns on tree trunks (humid conditions) – Eggs and sperm develop in gametangia at shoot tips of familiar moss plants – After fertilization, the zygote develops into a mature sporophyte • Develop a sporangium: stalk and jacketed structure where spores develop • o Examples • Peat mosses: used to soak up water (5x more than cotton), used as antiseptic, and also burned for electricity • peat bogs: moist mats of the remains of peat mosses
- 7. 23.3: Existing Seedless Vascular Plants • Whisk ferns, lycophytes, horsetails, and ferns • Different from bryophytes b/c sporophytes that develop independently of gametophytes – sporophytes that have well-developed vascular tissues – larger, longer-lived sporophyte phase of its life cycle • Sporophytes can live on land, while gametophytes cannot • Lycophytes: small club mosses on the forest floor – “ground pines” – sporophytes with true roots, stems, small leaves with vascular tissue – strobili (strobilius) bear spores that germinate, forming small, free-living gametophytes • heterosporous • Whisk ferns: not true ferns; resemble whisk brooms – have rhizomes: short, branched, mainly horizontal absorptive stems that grow underground – no leaves, made of scale-like branches – popular ornamental plants common to tropical/subtropical areas • Horsetails – sporophytes have rhizosomes – scalelike leaves whorl around a hollow, photosynthetic stem – spores produced inside cone-shaped clusters of leaves at shoot tip – found in streambank muds and other disrupted habitats • Ferns – have rhizosomes and fronds: aerial leaves that coil into what resembles a fiddlehead – sporangia: clusters of spores on the lower surface of the fronds
- 8. 23.4: Ancient Carbon Treasures • Lycophyte trees: giant club mosses that developed during the Carboniferous era – strobili that produced 8 billion microspores or hundreds of megaspores – 40m tall • 20m tall horsetails • Many swamp forests had sediments that compressed undecayed remains of plants into peat mosses – Pressure transformed the peat into coal: a renewable fossil fuel
- 9. 23.5: The Rise Of Seed-Bearing Plants • Most successful vascular plants because independent of water for fertilization – Seed ferns, gymnosperms, angiosperms • Different than seedless vascular plants because: – Microspores: develop into pollen grains to carry sperm to female structures (pollination) – Megaspores: develop within ovules: female reproductive structures that, when mature, produce seed • § female gametophyte, nutrient rich tissue, jacket of cell layers (to develop a seed coat) – Traits to conserve water: Thicker cuticles, stomata underneath leaves • Pre-Carboniferous: dominated by seed ferns (simlar to progymnosperms): earliest seed-producing plants
- 10. 23.6: Gymnosperms-Plants With “Naked” Seeds • Gymnosperm sporophyte stages are conspicuous trees and shrubs; the seeds are rather unprotected ("naked seeds") perched at the surface of reproductive parts. • Conifers (Coniferophyta) – The conifers (cone-bearers) are woody trees with needlelike or scalelike leaves. – Most are evergreens, some are deciduous. – Produce true cones: repro. structures in clusters of papery/wood-like scales that bear exposed to ovules on upper surface • Lesser Known Gymnosperms – Cycads (Cycadophyta) • These palmlike trees flourished during the Mesozoic era, but only about 100 species still exist--confined to the tropics and subtropics. • They bear massive cone-shaped strobili that produce either pollen (transferred by air currents or insects) or ovules. – Ginkgos (Ginkgophyta) • From the diversity of this group during the Mesozoic, only one species has survived. • They are remarkably hardy, showing resistance to insects, disease, and air pollutants. – Gnetophytes (Gnetophyta) are the most unusual gymnosperms; they live in tropical and desert areas.
- 11. 23.7: A Closer Look At The Conifers • Pine Life Cycle – The pine tree produces two kinds of cones: • Male cones produce sporangia which yield microspores that develop into pollen grains (male gametophyte). • Female cones produce ovules that yield megaspores (female gametophyte). – Pollination is the arrival of a pollen grain on the female reproductive parts, after which a pollen tube grows toward the egg. – Fertilization, which is delayed for up to a year, results in a zygote that develops into an embryo within the conifer seed. • Deforestation and the Conifers – Although conifers still dominate in certain climates, their slow reproductive pace puts them at a disadvantage compared to angiosperms. – However, deforestation by clear-cutting for their commercial value has put them at even greater risk.
- 13. 23.8: Angiosperms - Flowering, Seed-Bearing Plants • Characteristics of Flowering Plants – Only angiosperms produce specialized reproductive structures called flowers. • Of all the divisions of plants, angiosperms ("vessel seed") are the most successful and most diverse. • Most flowering plants coevolved with pollinators--insects, bats, birds, etc. – There are three major groups of flowering plants: • Magnoliids include magnolias, avocados, nutmeg, and black pepper plants. • Eudicots include familiar shrubs, trees (except conifers), and herbaceous plants. • Monocots include grasses, lilies, and the major food-crop grains. • Representative Life Cycle--A Monocot – The diploid sporophyte has extensive root and shoot systems; it also retains and nourishes the gametophyte. – Embryos are nourished by the endosperm within the seeds, which are packaged inside fruits.
- 14. 23.9: Seed Plants And People • Artificial selection of plants led to the development of domesticated grains including wheat and barley (11,000 yrs ago) • Different trees have been used for their wood pliability (paper, furniture, rope)
- 15. Works Cited Starr, Cecie and Ralph Taggart. Biology: The Unity and Diversity of Life. 10th Ed. Belmont: Brooks/Cole, 2004. Print.
Editor's Notes
- #2: Seed Plantshttp://www.youtube.com/profile?feature=iv&annotation_id=annotation_409148&user=greatpacificmedia&src_vid=kBPLKUTtXBM#p/c/9F64F28702C824B5/9/iv5JjH4kD1kand Byrophytes: http://www.youtube.com/profile?feature=iv&annotation_id=annotation_409148&user=greatpacificmedia&src_vid=kBPLKUTtXBM#p/c/9F64F28702C824B5/0/kBPLKUTtXBMChoice 2http://www.youtube.com/user/kosasihiskandarsjah?feature=BFThis guy has a bunch of vids on the different plant life cycles and he has ones for the moss, conifer, and flowering plant life cycles but not for the life cycle of a fern...