Evolution and Diversity of Plants Chapter 24

Evolution and Diversity of Plants 2Outline Evolutionary History  Alternation of Generations Flower Diversity

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

15 Flower Diversity

16 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

17 Flowering plant life cycle

Evolution and Diversity of Plants 18 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