Plant Diversity

1. Plant Diversity Chapter 22

2. 22-1 Introduction to Plants • Oldest fossil evidence-470 million years ago • Plants dominate the landscape • Provide the base for food chains on land • Provide shade, shelter and oxygen for animals of all sizes

3. What is a Plant? • Members of the Kingdom Plantae. • Multicellular eukaryotes • Cell walls of cellulose • Develop from multicellular embryos • Carry out photosynthesis using chlorophyll a and b • Most are autotrophs, few are parasites or saprobes (feed on decaying organisms)

4. How have plants become so successful if they can’t move to get away from predators or to get food? • Think of plants as “Stationary animals that eat sunlight”

5. The Plant Life Cycle • Two alternating phases known as the alternation of generations • Diploid (2N)- the sporophyte plant or spore producing • Haploid (N)- the gametophyte plant or gamete producing • Phyte-means plant

6. MEIOSIS Haploid Diploid FERTILIZATION Generalized Plant Life Cycle Section 22-1 Spores(N) Gametophyte Plant (N) Sporophyte Plant (2N) Sperm(N) Eggs(N)

7. Mosses and Ferns- Require water to reproduce • Seed Plants- reproduce without water • Many plants also have vegetative or asexual reproduction

8. What Plants Need to Survive • Developed adaptations to survive as sessile organisms • Plants need sunlight, water & minerals, gas exchange and transportation of water and minerals through the plant body

9. Sunlight • Need sunlight to carry out photosynthesis. • Adaptations to gather sunlight • Leaves broad and flat • Arrangement on stem to maximize light absorption

10. Water and Minerals • Need a constant supply of water • Need to get water to all cells, above ground too • Structures to limit water loss • Minerals absorbed with the water needed for plant growth

11. Gas Exchange • Require oxygen to carry out respiration and carbon dioxide for photosynthesis • Can’t lose water vapor in the process

12. Movement of Water and Nutrients • Specialized tissues that carry water up from the soil and distribute food through the plants • Simple plants do this by diffusion

13. Early Plants • Most of Earth’s history-no plants • Algae and photosynthetic prokaryotes provided the planets oxygen and food • Plants appeared, life on Earth changed • New ecosystems, soil formed, organisms developed • How did plants adapt to land, how did they evolve structures to allow life on land?

14. Origins in the Water • First plants evolved from an organism much like the green algae today • Algae have size, color and appearance of plants • Similar reproductive cycles • Cell walls and photosynthetic pigments like plants

15. The First Plants • DNA sequencing confirms that plants are closely related to certain groups of green algae. • Oldest known fossils of plants, 450 million years ago-similar to today’s mosses (cooksonia) • Suggest that they were still dependent on water to complete life cycle.

16. From plant pioneers two lineages • Mosses and their relatives • All other plants on Earth today • Evolved different adaptations to living on dry land.

17. Floweringplants Cone-bearingplants Ferns andtheir relatives Flowers; SeedsEnclosed in Fruit Mosses andtheir relatives Seeds Water-Conducting(Vascular) Tissue Green algaeancestor

18. Overview of the Plants Kingdom • Plants divided into four major divisions based on three features • Water conducting tissues • Seeds • Flowers • Mosses, Ferns, Cones, Flowers • Today classified more precisely by DNA sequencing

19. Cone-bearing plants760 species Floweringplants235,000 species Ferns andtheir relatives11,000 species Mosses andtheir relatives15,600 species

20. 22-2 Bryophytes • Nonvascular plants- No vascular tissue to conduct water and nutrients • Life cycles that depend on water for reproduction • No vascular tissue so they draw up water by osmosis only a few cm’s above ground • This keeps them very small • Produce sperm that swim to reach eggs • Have to live where rain or dew for part of yr.

21. Groups of Bryophytes • Most recognizable feature is that they are low growing plants in moist shaded areas • Plants thrive in areas where water is in regular supply • Three separate phyla. • Mosses or Bryophyta • Liverworts or Hepaticophyta • Hornworts or Anthocerophyta

22. Mosses • Most common Bryophyte. • Grow abundantly in areas with water and nutrient poor soil • Tolerate low temperatures, most abundant plants in the polar regions • Vary in appearance from mini evergreen trees to filament plants that form carpet of green

23. Gametophyte of moss looks like a stem with tiny leaves-one cell thick so lose water quickly • Reproduce with a thin stalk with a capsule that contains spores-sporophyte • No true roots-rhizoids anchor to the ground and absorb water and minerals • Water moves from cell to cell through rhizoids to rest of plant

24. Capsule Sporophyte Stalk Stemlikestructure Gametophyte Leaflikestructure Rhizoid

25. Liverworts • Flat leaves attached to the ground is what these plants look like. • Named because some species look like a flattened liver • Leaf forms an umbrella shaped object that produces the sperm and eggs. • Some form gemmae that are in cuplike structures that wash out and produce new individual

26. Hornwort • Look very much like the liverwort • Only difference is that the sporophyte looks like a tiny green horn • Most found where soil is moist year round

27. Life Cycle of Bryophytes • Life cycle involves alternation of generations • Gametophyte is dominant, recognized form and carries out the plants photosynthesis • Sporophyte is dependent on the gametophyte for water and nutrients

28. Dependence on Water • Sperm must swim to the egg to fertilize • Bryophytes must live in habitats where water is available at least part of the year

29. Life Cycle of Moss • When spore lands in a moist place it germinates and forms a protonema-mass of tangled green filaments. • Protonema grows to form rhizoids (rootlike structures and shoots that grow into the air. • Shoots form the familiar green part of the plants. The gametophyte • At the tips of the gametophyte are the archegonia (eggs) or antheridia (sperm).

30. Life cycle of Moss • Some have both on the same gametophyte some have separate gametophytes • When sperm and egg fuse and fertilization takes place the diploid zygote is formed • This zygote develops into the sporophyte part of the moss. It grows right out of the gametophyte part of the plant and depends on the gametophyte for food and water • When sporophyte matures it produces haploid spores in a capsule by meiosis and the capsule ruptures and releases the spores into the air and the cycle continues.

31. Protonema(young gametophyte)(N) Spores(N) Malegametophyte Femalegametophyte Maturesporophyte(2N) Capsule(sporangium) Antheridia Sperm(N) Archegonia Gametophyte(N) Youngsporophyte(2N) Zygote(2N) Sperm(N) Gametophyte(N) Egg(N) Figure 22–11  The Life Cycle of a Moss Section 22-2 Haploid (N) Diploid (2N) MEIOSIS FERTILIZATION

32. Human Uses of Moss • Sphagnum moss grow in acidic water of bogs • The dead sphagnum moss are called peat and accumulate in thick layers. • Peat can be harvested and used as fuel or in gardening to retain moisture near the plants or to increase the acidity of the soil near the plants.

33. 22.3 Seedless Vascular Plants • Bryophytes can only move water from cell to cell by osmosis. • 420 million years ago moss were joined by plants up to a few meters high • How did they grow that tall. • New transport system with vascular tissue. • Able to get water to a higher height

34. Evolution of Vascular Tissue: A Transport System • Tracheids-new type of cell that allows transport of fluids and nutrients in plants • Makes up xylem-the system of plants that transports water. • Def.-hollow cells with thick cell walls to resist pressure • Connected end to end like straws so that the water flows through them • More efficient movement than by diffusion

35. Evolution-cont. • 2nd type of vascular tissue is Phloem • Used to transport solutions of nutrients and carbohydrates produced by photosynthesis • Both xylem and phloem move nutrients through the plant even against gravity • Combination of xylem and lignin enables plants to grow much higher

36. Ferns and their Relatives • Include the club moss, horsetails and ferns • All have true roots, stems and leaves • Roots-underground organs that absorb water and nutrients. Xylem in center of root • Stems-supporting structure to connect root with the leaf • Leaves-Photosynthetic organs of the plants

37. Club Mosses-Phylum Lycophyta • Once very large and ancient group of land plants • Now much smaller phylum containing club mosses • Ancients grew up to 35 meters tall and made some of the Earth’s first forests that are now huge beds of coal. • Look like miniature pine trees so also called the ground pines.

38. Horsetails • Only living genus is Equisetum that grows about 1 meter tall. • Has true leaves, stems and leaves which are nonphotosynthetic. • Leaves are nonphotosynthetic, scalelike and are arranged in whorls • Scouring rush looks like a horses tail and has crystals of silica and used to scour pots and pans

39. Ferns • Phylum Pterophyta evolved 350 mya when the club moss forests covered the Earth. • Ferns survived in greater numbers than any other spore-bearing vascular plants • Have true vascular tissues, strong roots creeping stems called rhizomes and large leaves called fronds • Can thrive in areas of little light and most abundant in wet or seasonally wet habitats • Often found in forests of larger trees

40. Life Cycle of Ferns • Large plant that we recognize as the fern is the diploid sporophyte and is the dominant state. • Develop haploid spores in structures called sporangia in clusters called sori and are usually on the underside of the fronds • When spores germinate they develop into a haploid gametophyte.

41. Small gametophyte develops rootlike rhizoids and then flattens into a thin, heart shaped green structure that is the mature gametophyte • Small , tiny and develops independently from the sporophyte • Antheridia and archegonia are found on the underside of the gametophyte. Why??

42. Fertilization requires at least a thin film of water so sperm can swim to eggs • The zygote produced immediately develops into a new sporophyte plant • As the sporophyte develops the gametophyte withers away. • The sporophytes can live for many years as the fronds produced in spring die in the fall but the rhizomes live through the winter and produce new leaves

43. Figure 22–17  The Life Cycle of a Fern Section 22-3 MEIOSIS Sporangium(2N) Haploid gametophyte (N) Diploid sporophyte (2N) Frond Younggametophyte(N) Spores(N) Maturesporophyte(2N) Developingsporophyte(2N) Maturegametophyte(N) Antheridium Sperm Gametophyte(N) Egg Sporophyteembryo(2N) Archegonium FERTILIZATION

44. Compare/Contrast Table Section 22-3 Comparing Spore-Bearing Vascular Plants Characteristics Watertransportation Structure Club Mosses By vasculartissue Look like miniature pine trees; scalelike leaves Horsetails By vasculartissue True leaves, stems, and roots Ferns By vasculartissue Creeping or underground rhizomes (stems); fronts (leaves); some have no roots or leaves

45. 22.4 Seed Plants • Whether acorns, pine nuts, dandelion seeds, or kernels of corn seeds are found everywhere. • Plants with this single trait have evolved to become the most dominant group of photosynthetic organisms on land • Two major groups- • Gymnosperms-bear seeds on surface of cones • Angiosperms-flowering plants bear seeds inside a layer of tissue that protects the seed

46. Reproduction Free From Water • Like all plants-alternation of generations • Gametophyte and sporophyte stage • Difference from moss/ferns in that they don’t need water for fertilization of gametes • Because of this they can live everywhere • Adaptations that allow this • Flowers or cones, transfer of sperm by pollination, protection of embryo in seeds

47. Cones and Flowers • Gametophytes of seed plants grow and mature in sporophyte structures called cones or flowers. • Cones are seed bearing structures of gymnosperms • Flowers are angiosperms seed bearing structures

48. Pollen • The entire male gametophyte is contained in a tiny structure called a pollen grain. • Doesn’t travel through water • Carried to the female reproductive structure by • Wind • Insects • Animals • Transfer of pollen to female is called pollination

49. Seeds • Def.-Seed is the embryo of a plant that is encased in a protective covering and surrounded by a food supply. • Embryo-organism in an early stage of development • Plant embryo is diploid and is the early developmental stage of the sporophyte plant

50. Seed food supply provides nutrients to the growing embryo • Seed coat-surrounds and protects the embryo and keeps it from drying out • Seeds may have specialized structures to help with dispersal to other habitats • Embryos in seeds can remain dormant for long periods of time and start growing again only when the conditions are good for survival