Evolution and Diversity of Plants Chapter 24

Evolution and Diversity of Plants 2Outline Evolutionary History  Alternation of Generations Nonvascular Plants Vascular Plants  Seedless  Seed  Angiosperms ­Monocots and Eudicots ­Flowers

Evolution and Diversity of Plants 3 Evolutionary History of Plants More than 98% of all biomass is plants Multicellular photosynthetic eukaryotes 280,000 known species Thought to have evolved from freshwater algae over 500 mya Evolution of plants marked by four evolutionary events associated with four major groups of plants  Nonvascular Plants ­Advent of nourishment of a multicellular embryo within the body of the female plant

4 Representatives of the Four Major Groups of Plants

Evolutionary History of Plants 5

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Evolution and Diversity of Plants 7 Alternation of Generations Life cycle involves alternation of generations  Multicellular 1n individuals (gametophytes) produce multicellular 2n individuals (sporophytes)  Multicellular 2n individuals (sporophytes) produce multicellular 1n individuals (gametophytes) Sporophyte (2n):  Multicellular individual that produces spores by meiosis  Spore is haploid cell that will become the gametophyte Gametophyte (1n):  Multicellular individual that produces gametes  Gametes fuse in fertilization to form zygote  Zygote is a diploid cell that will become the sporophyte

8 Alternation of Generations

Evolution and Diversity of Plants 9 Alternation of Generations Appearance of generations varies widely  In ferns, female portions are archegonia and are fertilized by flagellated sperm  In angiosperm, female gametophyte (embryo sac), consists of an ovule ­Following fertilization, ovule becomes seed  In seed plants, pollen grains are mature sperm- bearing male gametophytes

10 Reduction in the Size of the Gametophyte

Evolution and Diversity of Plants 11 Other Terrestrial Adaptations Vascular tissue transports water and nutrients to the body of the plant Cuticle provides an effective barrier to water loss Stomata bordered by guard cells that regulate opening, and thus water loss

12 Protection of Eggs and Embryos

13 Leaves of Vascular Plants

Evolution and Diversity of Plants 14 Nonvascular Plants Nonvascular plants (bryophytes) Lack specialized means of transporting water and organic nutrients Do not have true roots, stems, and leaves Gametophyte is dominant generation  Produces eggs in archegonia  Produces flagellated sperm in antheridia  Sperm swim to egg in film of water to make zygote

15 Hornwort

16 Liverwort, Marchantia

17 Moss (Polytrichum) Life Cycle

Evolution and Diversity of Plants 18 Vascular Plants Xylem conducts water and dissolved minerals up from roots Phloem conducts sucrose and other organic compounds throughout the plant Lignin strengthens walls of conducting cells in xylem Most seedless vascular plants are homosporous  Windblown spores are dispersal agents All seed plants are heterosporous and have male and female gametophytes  Seeds disperse offspring

19 Cooksonian Fossil

20 Vascular Tissue

Evolution and Diversity of Plants 21 Seedless Vascular Plants Club moss Club moss Horsetail Horsetail Whisk ferns Whisk ferns Ferns Ferns

22 Club Moss, Lycopodium

23 Horsetail, Equisetum

24 Whisk fern, Psilotum

25 Diversity of ferns

26 Fern Life Cycle

Evolution and Diversity of Plants 27 Seed Plants Seed plants are the most plentiful plants in the biosphere  Seed coat and stored food allow an embryo to survive harsh conditions during long period of dormancy  Heterosporous ­Drought-resistant pollen grains ­Ovule develops into seed

28 Seed Plants

Evolution and Diversity of Plants 29Gymnosperms Gymnosperms have ovules and seeds exposed on the surface of sporophylls  Confiers  Cycads  Ginkgoes  Gnetophytes

30 Conifers - Pine Life Cycle

31 Cycad Cones Figure 24.19

32 The Ginkgo Tree

33 Gnetophyte - Ephedra Figure 24.21

34 Gnetophytes - Welwitschia miribilis

Evolution and Diversity of Plants 35Angiosperms Angiosperms (phylum Anthophyta) An exceptionally large and successful group of plants Ovules are always enclosed within diploid tissues Became dominant group of plants in the late Cretaceous and early Paleocene periods

36 Amborella trichopoda

Evolution and Diversity of Plants 37 Monocots and Eudicots Two classes of flowering plants  Monocotyledones (Monocots) ­One cotyledon in seed  Eudicotyledones (Dicots) ­Two cotyledons in seed

38 Flower Diversity

39 Generalized Flower Peduncle (flower stalk) expands at tip into receptacle Bears sepals, petals, stamens, and carpels, all attached to receptacle in whorls Calyx (collection of sepals) protect flower bud before it opens Corolla (collection of petals) Each stamen consists of an anther and a filament (stalk) Carpel has three major regions: Ovary – swollen base (fruit) Style – elevates stigma Stigma – sticky receptor of pollen grains

40 Flowering plant life cycle

Evolution and Diversity of Plants 41 Flowers and Diversification Wind-pollinated flowers are usually not showy Bird-pollinated flowers are often colorful Night-blooming flowers attract nocturnal mammals or insects  Usually white or cream-colored Fruits of flowers protect and aid in dispersal  Utilize wind, gravity, water, and animals for dispersal

Evolution and Diversity of Plants Ending Slide Chapter 24