Chapter 16

1. Chapter 16 0 Plants and the Move onto Land

2. Terrestrial Adaptations of Plants Structural Adaptations • A plant is • A multicellular eukaryote • A photoautotroph, making organic molecules by photosynthesis • Plants are terrestrial organisms that include forms that have returned to water, such as water lilies. © 2010 Pearson Education, Inc.

3. In terrestrial habitats, the resources that a photosynthetic organism needs are found in two very different places: • Light and carbon dioxide are mainly available in the air • Water and mineral nutrients are found mainly in the soil • The complex bodies of plants are specialized to take advantage of these two environments by having • Aerial leaf-bearing organs called shoots • Subterranean organs called roots

4. Reproductive structures (such as those in flowers) contain spores and gametes Plant Leaf performs photosynthesis Cuticle reduces water loss; stomata regulate gas exchange Shoot supports plant (and may perform photosynthesis) Alga Whole alga performs photosynthesis; absorbs water, CO2, and minerals from the water Surrounding water supports the alga Roots anchor plant; absorb water and minerals from the soil (aided by fungi) Figure 16.1

5. Most plants have mycorrhizae, symbiotic fungi associated with their roots, in which the fungi • Absorb water and essential minerals from the soil • Provide these materials to the plant • Are nourished by sugars produced by the plant

6. Roots Fungus Root surrounded by fungus Figure 16.2

7. Leaves are the main photosynthetic organs of most plants, with • Stomata for the exchange of carbon dioxide and oxygen with the atmosphere • Vascular tissue for transporting vital materials • A waxy cuticle surface that helps the plant retain water

8. Phloem Vascular tissue Xylem Oak leaf Figure 16.3

9. Vascular tissue in plants is also found in the • Roots • Shoots • Two types of vascular tissue exist in plants: • Xylem transports water and minerals from roots to leaves • Phloem distributes sugars from leaves to the roots and other nonphotosynthetic parts of the plant

10. (1) About 475 million years ago plants originated from an algal ancestor giving rise to bryophytes, nonvascular plants, including mosses, liverworts, and hornworts that are nonvascular plants without • Lignified walls • True roots • True leaves

11. (2) About 425 million years ago ferns evolved • With vascular tissue hardened with lignin • But without seeds

12. (3) About 360 million years ago gymnosperms evolved with seeds that consisted of an embryo packaged along with a store of food within a protective covering but not enclosed in any specialized chambers. • Today, conifers,consisting mainly of cone-bearing trees such as pines, are the most diverse and widespread gymnosperms.

13. (4) About 140 million years ago angiosperms evolved with complex reproductive structures called flowers that bear seeds within protective chambers called ovaries.

14. The great majority of living plants • Are angiosperms • Include fruit and vegetable crops, grains, grasses, and most trees • Are represented by more than 250,000 species

15. PLANT DIVERSITY Bryophytes (nonvascular plants) Ferns (seedless vascular plants) Gymnosperms (naked-seed plants) Angiosperms (flowering plants) Figure 16.7

16. Bryophytes • Bryophytes, most commonly mosses • Sprawl as low mats over acres of land • Need water to reproduce because their sperm swim to reach eggs within the female gametangium • Have two key terrestrial adaptations: • A waxy cuticle that helps prevent dehydration • The retention of developing embryos within the mother plant’s gametangium

17. Figure 16.8

18. Mosses have two distinct forms: • The gametophyte, which produces gametes • The sporophyte, which produces spores

19. Spores Spore capsule Sporophyte Gametophytes Figure 16.9

20. The life cycle of a moss exhibits an alternation of generations shifting between the gametophyte and sporophyte forms. • Mosses and other bryophytes are unique in having the gametophyte as the larger, more obvious plant.

21. Mit osis osis Mit sis o t Mi Gametes: sperm and eggs (n) Spores (n) Gametophyte (n) FERTILIZATION MEIOSIS Spore capsule Zygote (2n) Sporophyte (2n) Key Haploid (n) Diploid (2n) Figure 16.10-5

22. Ferns • Ferns are • Seedless vascular plants • By far the most diverse with more than 12,000 known species • The sperm of ferns, like those of mosses • Have flagella • Must swim through a film of water to fertilize eggs

23. Spore capsule “Fiddlehead” (young leaves ready to unfurl) Figure 16.11

24. Conifers • Conifers • Cover much of northern Eurasia and North America • Are usually evergreens, which retain their leaves throughout the year • Include the tallest, largest, and oldest organisms on Earth

25. Figure 16.13

26. Terrestrial Adaptations of Seed Plants • Conifers and most other gymnosperms have three additional terrestrial adaptations: • Further reduction of the gametophyte • Pollen • Seeds • A pine tree or other conifer is actually a sporophyte with tiny gametophytes living in cones.

27. Scale Ovule-producing cones; the scales contain female gametophytes Pollen-producing cones; they produce male gametophytes Ponderosa pine Figure 16.15

28. A second adaptation of seed plants to dry land was the evolution of pollen. • A pollen grain • Is actually the much-reduced male gametophyte • Houses cells that will develop into sperm • The third terrestrial adaptation was the development of the seed, consisting of • A plant embryo • A food supply packaged together within a protective coat

29. Seeds • Develop from structures called ovules, located on the scales of female cones in conifers • Can remain dormant for long periods before they germinate, as the embryo emerges through the seed coat as a seedling

30. Haploid (n) Diploid (2n) Female cone, cross section Cross section of scale Integument Spore case (a) Ovule Spore Egg nucleus Female gametophyte Spore case (b) Fertilized ovule Pollen tube Discharged sperm nucleus Pollen grain (male gametophyte) Seed coat (derived from integument) (c) Seed Food supply (derived from female gametophyte tissue) Embryo (new sporophyte) Figure 16.16-3

31. Angiosperms • Angiosperms • Dominate the modern landscape • Are represented by about 250,000 species • Supply nearly all of our food and much of our fiber for textiles • Their success is largely due to • A more efficient water transport • The evolution of the flower

32. Flowers, Fruits, and the Angiosperm Life Cycle • Flowers help to attract pollinators who transfer pollen from the sperm-bearing organs of one flower to the egg-bearing organs of another. • A flower is actually a short stem with four whorls of modified leaves: • Sepals • Petals • Stamens • Carpels

33. Petal Stigma Anther Carpel Stamen Style Filament Ovary Ovule Sepal Figure 16.17

34. Pansy Bleeding heart California poppy Water lily Figure 16.18

35. Germinated pollen grain (male gametophyte) on stigma of carpel Anther at tip of stamen Pollen tube growing down style of carpel Mature sporophyte plant with flowers Ovary (base of carpel) Ovule FERTILIZATION Endosperm Embryo sac (female gametophyte) Egg Zygote Two sperm nuclei Sporophyte seedling Embryo (sporophyte) Seed Germinating seed Key Haploid (n) Diploid (2n) Seed (develops from ovule) Fruit (develops from ovary) Figure 16.19-6

36. Although both have seeds • Angiosperms enclose the seed within an ovary • Gymnosperms have naked seeds

37. Fruit • Is a ripened ovary • Helps protect the seed • Increases seed dispersal • Is a major food source for animals

38. Wind dispersal Animal transportation Animal ingestion Figure 16.20

39. Angiosperms and Agriculture • Gymnosperms supply most of our lumber and paper. • Angiosperms • Provide nearly all our food • Supply fiber, medications, perfumes, and decoration • Agriculture is a unique kind of evolutionary relationship between plants and animals. • The exploding human population is • Extinguishing plant species at an unprecedented rate • Destroying fifty million acres, an area the size of the state of Washington, every year!

40. Figure 16.21

41. Humans depend on plants for thousands of products including • Food • Building materials • Medicines

42. Table 16.1