Ch. 30 Plant Diversity II: The Evolution of Seed Plants

1. Ch. 30 Plant Diversity II: The Evolution of Seed Plants

2. The seed replaces the spore • Spores used for first 100 million years of plant life on land • A seed is a resistant structure that is multicellular and is more complex

3. Overview • Seed plants are vascular plants • Produce seeds • Three Important Reproductive adaptations • Advent of seed • Evolution of pollen • Reduction of Gametophyte (produce gametes)

4. Reduction of Gametophyte • Alteration of generations: • 2N vs. 4N life stage • Gametophyte: haploid cell, • Sporophyte: dipliod cell

5. Reproductive Adaptations • Gametophytes of seedless vascular plants develop is soil independently • Gametophytes of seed plants are protected in reproductive tissue of sporophyte generation

6. Seeds for dispersing offspring • Solution for resisting harsh climates • Sporophyte embryo w/ food supply w/I protective coat • Two types of sporangia produce 2 spores • Megasporangia: megaspores; give rise to female gametophyte, kept w/ parent • Integument cover megasporangium • Microsporangia: microspores; give rise to male gametophyte • Ovule: integument, megasporangium, megaspore

7. Pollen • Microspore develop into pollen grain • Pollination: transfer of pollen to ovule • Two Clades of seed plants (seeds/pollen) • Gymnosperm • Angiosperms

8. Gymnosperms • Means naked seeds • Mesozoic era “age of gymnosperm” • There are four divisions • Cycad – resemble palms • Ginkgo – fanlike leaves, gold and decidous in autumn • Gnetophyta – 3 genera not closely related • Weltwitshcia, gnetum, gnetophyta • Conifers

9. Phylum Cycadophyta • Resembles palms trees • Cycads

10. Phylum Ginkophyta • Fanlike leaves, deciduous,

11. Phylum Gnetophyta • Three Genera • Welwitschia: giant strap like leaves • Gnetum: tropical trees, vines • Ephedra: a shrub of American deserts

12. Conifers • Cones Latin conus, cone and ferre, to carry • Pines, firs, spruces, larches, most large trees • Most are evergreen, retain leaves for year • Needle shaped leaves, thick cuticles, • Most pulp and paper come from conifers • Largest and oldest organism on earth • Largest phylum of plants

13. Figure 30.8a Phylum Coniferophyta: Douglas fir Oregon Most used for timber

14. Figure 30.8b Phylum Coniferophyta: Sequoia 2500 metric tons 14 blue whales 40,000 people

15. Figure 30.8bx Sequoias

16. Figure 30.8c Phylum Coniferophyta: Cypress

17. Figure 30.8d Phylum Coniferophyta: Pacific yew Source of Taxol (treatment of ovarian cancer)

18. Figure 30.8e Phylum Coniferophyta: Common juniper Fleshy sporophylls cones

19. Figure 30.8f Phylum Coniferophyta: A pine farm Clones from cell culture produce seedlings

20. Figure 30.8g Phylum Coniferophyta: Wollemia pine Thought to be extinct till found in 1994 40 individuals, in two small groves “Living Fossil”

21. Life Cycle of Pine: Step 1 • Pollen cones and Ovulate cones • Pollen has microsporangia • Meiosis • Pollen grains • Ovulate contains • Scales each w/ 2 ovules • Megasporangim • Pollination • Pollen falls on ovulate cones • Drawn into ovule • Pollen grain germinates forming pollen tube, digest its way through megasporangium • Fertilization occurs 1 year after pollination

22. Life Cycle Part 2 • Megaspore mother cell produces 4 megaspores, only one survives. • Two archegonia develop each w/ egg • Pollinization occurs

23. Life Cycle Part 3 • New sporophyte has rudimentary • Roots • Embryonic leaves • Food Supply (female gametophyte) • Ovule developed into Pine seed • Embryo (new sporphyte) • Three Plant Generations: • One Gametophyte • Two Sporophyte

24. Figure 30.10 A closer look at pine cones (Pinus sp.)

25. Figure 30.10x1 Pine Sporangium with spores

26. Pollen Grain

27. Figure 30.10x3 Pine embryo

28. Angiosperms: Flowering Plants • Most diverse and widespread • Vascular seed plants producing a flower. • Most diverse and widespread • 250,000 known species (720 known gymnosperms) • There are two classes of angiosperms • Monocots- lillies, orchids, yuccas, palms, and grasses • Dicots- roses, peas, buttercups, sunflowers, oaks, maples

29. Refinements of Angiosperms • Better xylem, better tracheids. • Fiber cell for support of tracheids. • Vessel Elements more efficient. • Strong role in adaptations leading to flowers and fruits.

30. Flowers: reproductive organ • Reproductive structure of angiosperm • Flower: specialized shoot w/ 4 modified leaves • Sepals: green, enclose flower before it opens • Petals: bright colors, Attractor, sterile, surrounds sporophyll (fertile) • Stamen: produce microspore, give rise to male gametophyte. • Carpels: female sporophyll, produces megaspore, give rise to female gametophyte

31. Carpel Evolution: Theory

32. Fruit • Mature Ovary • Develops from Ovule • Protects dormant seed • Aids in dispersal • Modifications: (flower withers, fruit develops) • Pericarp: wall of ovary, thickened wall of fruit • Pollination does not occur, no fruit develops

33. Figure 30.16 Fruit adaptations that enhance seed dispersal: Red berries (left), dandelion (right)

34. Figure 30.16x1 Dandelion seed dispersal

35. Figure 30.16x2 A bird eating berries containing seeds that will be dispersed later with the animal's feces

36. Fruit Classifications: • Fruits have several types • Simple Fruit: fruit from single ovary. Cherry, soybean pod • Aggregate Fruit: single flower that has several carpels. Blackberry. • Multiple Fruit: group of flowers clustered together. Walls of ovaries thicken and fuse together…..become one fruit. Pineapple • Inflorescence

37. Life cycle of an angiosperm • Pollen Grain • Ovule • Embryo Sac • Cross pollination: same species, different plant • Stamen/Carpel mature at different time • Arragment prevents self pollination • Double Fertilization: 2 sperm pollinate single ovule, triploid nucleus

38. Figure 30.17 The life cycle of an angiosperm

39. Figure 38.1 Simplified overview of angiosperm life cycle

40. Flowers: • Complete flowers have all four basic floral organs • Incomplete flowers lacking one or more floral organs • Bisexual Flower: equipped with both stamen and carpel • Trillium • Unisex Flower: missing either stamen or carpel • Monoecious: stamen and carpel are located on same individual plant • Dioecious: stamen and carpel located on separate plants

41. Figure 38.4 The development of angiosperm gametophytes (pollen and embryo sacs)

42. Figure 38.7 Genetic basis of self-incompatibility

43. Figure 38.9 Growth of the pollen tube and double fertilization

44. Figure 38.10 The development of a dicot plant embryo

45. Figure 38.11 Seed structure

47. Coevolution • Angiosperms and Animals have influenced each other. • Mutual evolution b/w two species is CoEvolution: • Pollinator/Plant relationships • Monkey and the Fig

48. Figure 30.18 Flower-pollinator relationships: Scottish broom flower and honeybee (left), hummingbird (top right), baobab tree and bat (bottom right)

49. Plants and Humans • Agriculture based mostly on angiosperms • Nonrenewable source • Space for people vr. Plants • Slash and Burn • 50 million acres of tropical rain forest cut down per year (state of Washington) • Source of medicine resource

50. Figure 30.19 Deforestation is an international practice