Plant Evolution and Diversity: From Algae to Land Colonizers

1. Chapter 17 0 Plants, Fungi, and the Colonization of Land

2. Plants and Fungi—A Beneficial Partnership • Orange groves in Florida, Texas, and California • Rely on associations between plants and fungi

3. A mycorrhizal fungus enveloping roots of a red pine tree • Mycorrhizae, mutually beneficial associations of plant roots and fungi • Are common, and may have enabled plants to colonize land

4. LM 444 PLANT EVOLUTION AND DIVERSITY • 17.1 Plants evolved from green algae • Molecular, physical, and chemical evidence • Indicates that green algae called charophyceans are the closest living relatives of plants Figure 17.1A, B

5. 17.2 Plants have adaptations for life on land • Plants are multicellular photosynthetic eukaryotes

6. Plant Reproductive structures, as in flowers,contain spores and gametes Leaf performs photosynthesis Cuticle covering leaves and stemsreduces water loss; stomata inleaves allow gas exchange Stem supports plant and mayperform photosynthesis Surrounding watersupports alga Alga Whole algaperformsphotosynthesis;absorbs water,CO2, andminerals fromthe water Rootsanchor plant;absorb water andminerals fromthe soil Holdfastanchors alga • Plants have some specific adaptations • That are not found in algae Figure 17.2A

7. Obtaining Resources from Two Locations • Apical meristems • Are the growth-producing regions of a plant • Help maximize exposure to the resources in the soil and air

8. Plants have vascular tissue • Which helps distribute nutrients throughout the organism Figure 17.2B

9. Supporting the Plant Body • The cell walls of some plant tissues • Are thickened and strengthened by lignin

10. Maintaining Moisture • A waxy cuticle covers the stems and leaves of plants • And helps retain water • Stomata • Are tiny pores in leaves that allow for gas exchange

11. Reproducing on Land • Many living plants • Produce gametes that are encased in protective structures

12. Land plants Vascular plants Bryophytes(nonvascular plants) Seed plants Seedless vascular plants Mosses Hornworts Liverworts Angiosperms Gymnosperms Lycophytes(club mosses and relatives) Pterophytes(ferns and relatives) Origin of seed plants(about 360 mya) Origin of vascular plants(about 420 mya) Origin of land plants(about 475 mya) • 17.3 Plant diversity reflects the evolutionary history of the plant kingdom • Some highlights of plant evolution Figure 17.3A

13. Bryophytes lack vascular tissue and include • The mosses, hornworts, and liverworts Figure 17.3B

14. Vascular plants • Have supportive vascular tissues

15. Ferns are seedless vascular plants • With flagellated sperm Figure 17.3C

16. Seed plants • Have pollen grains that transport sperm • Protect their embryos in seeds

17. Gymnosperms, such as pines • Produce seeds in cones Figure 17.3D

18. The seeds of angiosperms • Develop within protective ovaries Figure 17.3E

19. ALTERNATION OF GENERATIONS AND PLANT LIFE CYCLES • 17.4 Haploid and diploid generations alternate in plant life cycles • The haploid gametophyte • Produces eggs and sperm by mitosis

20. The zygote develops into the diploid sporophyte • In which meiosis produces haploid spores • Spores grow into gametophytes

21. Key Gametophyteplant (n) Haploid (n) Diploid (2n) Mitosis Sperm Mitosis Spores (n) Egg Gametes (n) Meiosis Fertilization Zygote (2n) Mitosis Sporophyteplant (2n) • Alternation of generations Figure 17.4

22. 17.5 Mosses have a dominant gametophyte • A mat of moss is mostly gametophytes • Which produce eggs and swimming sperm • The zygote develops on the gametophyte • Into the smaller sporophyte

23. Gametophytes (n) Key 1 Haploid (n) Male Mitosis anddevelopment Diploid (2n) 5 Sperm (n) (releasedfrom gametangium) Spores (n) Egg (n) Female 1 Fertilization Sporangium Stalk Sporophytes (growingfrom gametophytes) Meiosis 2 Zygote (2n) Sporophyte (2n) 4 Mitosis anddevelopment 3 • Life cycle of a moss Figure 17.5

24. 17.6 Ferns, like most plants, have a dominant sporophyte • Sperm, produced by the gametophyte • Swim to the egg

25. Key 1 Haploid (n) Sperm (n)(released from malegametangium) Diploid (2n) Mitosis anddevelopment 5 Gametophyte (n)(underside) Female gametangium (n) Spores (n) Egg (n) Meiosis Fertilization Clusters ofsporangia 4 2 Zygote (2n) New sporophyte (2n)growing out ofgametophyte Mitosis anddevelopment 3 Mature sporophyte(independent of gametophyte) • Life cycle of a fern Figure 17.6

26. 17.7 Seedless plants dominated vast “coal forests” • Ferns and other seedless plants • Once dominated ancient forests • Their remains formed coal Figure 17.7

27. 17.8 A pine tree is a sporophyte with tiny gametophytes in its cones • A sperm from a pollen grain • Fertilizes an egg in the female gametophyte • The zygote develops into a sporophyte embryo • And the ovule becomes a seed, with stored food and a protective coat

28. 4 A haploid spore cell inovule develops intofemale gametophyte,which makes eggs. Scale 1 Female conebears ovules. Female gametophyte (n) Ovule Meiosis Sporangium (2n) 5 Male gametophyte(pollen) grows tubeto egg and makesand releases sperm. Spore mother cell (2n) Integument Eggs (n) Pollen grains (malegametophytes) (n) 3 Pollination Sperm (n) Fertilization Male gametophyte(pollen grain) Meiosis 2 Sporangia in male coneproduce spores by meiosis;spores develop into pollengrains. Mature sporophyte Seed coat Embryo(2n) Zygote(2n) Foodsupply Zygote developsinto embryo, andovule becomes seed. 6 Key Seed germinates,and embryo growsinto seedling. Haploid (n) 7 Diploid (2n) Seed • Life cycle of a pine tree Figure 17.8

29. Stigma Style Carpel Anther Stamen Ovary Filament Petal Sepal Ovule Receptacle • 17.9 The flower is the centerpiece of angiosperm reproduction • Flowers usually consist of • Sepals, petals, stamens (which produce pollen), and carpels (which produce eggs) Figure 17.9A, B

30. 17.10 The angiosperm plant is a sporophyte with gametophytes in its flowers • In the angiosperm life cycle • Ovules become seeds, and ovaries become flowers

31. Haploid spores in anthers develop into pollen grains: male gametophytes. 1 Pollen grains (n) Pollination and growth of pollen tube 3 Meiosis Stigma Haploid spore in each ovule develops into female gametophyte, which produces egg. 2 Stigma Pollen grain Anther Pollen tube Meiosis Egg (n) Ovule Ovary Ovule Sporophyte (2n) 7 Seed germinates, and embryo grows into plant. Seeds Food supply Fertilization Fruit (mature ovary) 6 Seed coat Key Haploid (n) 5 Seed 4 Zygote (2n) Diploid (2n) Embryo (2n) • Life cycle of an angiosperm Sperm Figure 17.10

32. 17.11 The structure of a fruit reflects its function in seed dispersal • Fruits are adaptations that disperse seeds Figure 17.11A–C

33. CONNECTION • 17.12 Agriculture is based almost entirely on angiosperms • Angiosperms provide most of our food • And other important commercial products

34. 17.13 Interactions with animals have profoundly influenced angiosperm evolution • Angiosperms • Are a major source of food for animals

35. Animals also aid plants in pollination Figure 17.13A–C

36. CONNECTION • 17.14 Plant diversity is a nonrenewable resource • Many types of forests • Are being destroyed worldwide Figure 17.14

37. Some plants in these forests • Can be used in medicinal ways Table 17.14

38. FUNGI • 17.15 Fungi absorb food after digesting it outside their bodies • Fungi are heterotrophic eukaryotes • That digest their food externally and absorb the nutrients Figure 17.15A

39. Hypha Mycelium • A fungus usually consists of a mass of threadlike hyphae • Called a mycelium Figure 17.15B, C

40. 17.16 Fungi produce spores in both asexual and sexual life cycles • In some fungi, fusion of haploid hyphae • Produces a heterokaryotic stage containing nuclei from two parents

41. Key Heterokaryotic stage Haploid (n) Heterokaryotic (n+n) (unfused nuclei) Fusion of nuclei Diploid (2n) Fusion of cytoplasm Zygote (2n) Spore-producing structures Sexual reproduction Meiosis Spores (n) Asexual reproduction Mycelium Spore-producing structures Germination Germination Spores (n) • After the nuclei fuse • Meiosis produces haploid spores Figure 17.16

42. 17.17 Fungi can be classified into five groups • Fungi evolved from an aquatic, flagellated ancestor

43. Chytrids Zygomycetes (zygote fungi) Ascomycetes (sac fungi) Basidiomycetes (club fungi) Glomeromycetes (arbuscular mycorrhizal fungi) • Fungal phylogeny Figure 17.17A

44. Fungal groups include • Chytrids

45. SEM 6,500 • Zygomycetes • Glomeromycetes Figure 17.17B, C

46. Ascomycetes Figure 17.17D

47. Basidiomycetes Figure 17.17E

48. Key Zygosporangium (n + n) Haploid (n) Heterokaryotic (n + n) Diploid (2n) Mycelia of different mating types Cells fuse 2 3 Fusion of nuclei 1 4 Meiosis Young zygosporangium (heterokaryotic) Sporangium Spores (n) • 17.18 Fungal groups differ in their life cycles and reproductive structures • Fungal life cycles • Often include asexual and sexual stages Figure 17.18A

49. Key Diploid nuclei 3 Haploid (n) Fusion of nuclei Heterokaryotic (n+n) Meiosis Diploid (2n) Spores released 4 Basidia Spores (n) Mushroom Germination of spores and growth of mycelia 5 Growth of heterokaryotic mycelium 2 Fusion of two hyphae of different mating types 1 • Fungal groups have characteristic reproductive structures Figure 17.18B

50. CONNECTION • 17.19 Parasitic fungi harm plants and animals • Parasitic fungi cause 80% of plant diseases • And some serious human mycoses Figure 17.19A–C