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Chapter 27; Plant Evolution & Diversity

Chapter 27 - Plant Evolution & Diversity

27.1 Major Themes in Plant Evolution

  • Overview of plant evolutionary history and major adaptations.

  • Discussion of key plant groups and their significance.

27.2 Bryophytes

  • Definition: Non-vascular plants including mosses, liverworts, and hornworts.

  • Essential for understanding early plant adaptations.

27.3 Vascular Plants

  • Importance of vascular tissue for transport of nutrients and water.

  • Key groups: Lycophytes, Monilophytes, Gymnosperms, and Angiosperms.

27.4 Gymnosperms

  • Definition: Seed plants that produce "naked seeds".

  • Key characteristics and examples including conifers and cycads.

27.5 Angiosperms

  • Definition: Flowering plants with seeds enclosed in fruit.

  • Significance of flowers and fruits in plant reproduction and dispersal.

Plant Characteristics

  • Eukaryotic: All plant cells are complex, with membrane-bound organelles.

  • Multicellular: Plants consist of multiple cells working together.

  • Photoautotrophic: Utilize sunlight to produce energy through photosynthesis.

  • Chloroplasts: Organelle where photosynthesis occurs.

  • Chlorophyll a & b: Pigments essential for capturing sunlight.

  • Non-motile: Plants cannot move, but they grow indeterminately.

  • Totipotent cells: Capable of differentiating into any cell type.

Alternation of Generations

  • Sexual Reproduction: Involves gametes and fertilization.

  • Asexual Reproduction: Reproduction without gametes.

  • Haplodiplontic: Life cycle has both haploid (gametophyte) and diploid (sporophyte) stages.

  • Gametophyte: The haploid phase that produces gametes.

  • Sporophyte: The diploid phase that produces spores.

Cell Structure

  • Cell wall: Composed of cellulose or lignin, important for structural support.

  • Turgor Pressure: Pressure of water within cells that helps maintain structure in hypotonic solutions.

  • Vascular tissue: Comprises xylem and phloem for transport.

Kingdom Plantae and Major Transformations

  • Glaucophytes: An ancient lineage giving rise to green algae.

  • Key evolutionary transformations:

    1. Alternation of Generations for embryo protection.

    2. Development of vascular tissue (xylem and phloem).

    3. Evolution of pollen and seeds.

    4. Evolution of flowers and fruits.

Major Plantae Synapomorphy

  • Primary Endosymbiosis: Event leading to chloroplast evolution, as cyanobacteria were engulfed by a host cell.

  • This led to diverse plant forms through evolution.

Adaptations to Land

  • Waxy Cuticle: Protects against water loss and pathogens.

  • Stomata: Pores in leaves/stems for gas exchange.

    • Open for CO2 uptake and closed to conserve water.

  • Tracheids: Specialized cells in xylem for water and nutrient transport, reinforced with lignin.

  • Pollen: Male gametophyte that transfers sperm to ovules without water.

  • Seeds: Protect embryos, store nutrients, and aid in dispersal.

  • Mutualism with fungi: Mycorrhizae increase water absorption in exchange for sugars from the plant.

Plantae Phylogeny

  • Classification based on molecular evidence.

  • Chlorophyll a & b: Key pigments shared among plants.

  • Sporopollenin: A biopolymer providing protection to spores.

  • Evolutionary relationships dictate plant classification and phylogeny.

Different Plant Groups

Bryophytes

  • Seedless, non-vascular plants (mosses, liverworts, hornworts).

  • Key Traits:

    • Short stature.

    • Rhizoids for anchorage.

    • Flagellated sperm for reproduction.

Lycophytes

  • First vascular plants, includes club mosses.

  • Key traits include archegonia, antheridia, and motile sperm.

Monilophytes

  • Includes ferns, horsetails, and whisk ferns, all seedless and vascular.

  • Dominant sporophyte stage and presence of roots and rhizoids.

Seed Plant Characteristics

  • Dominant sporophyte phase, photosynthetic.

  • Gametophytes develop within sporophytes and are microscopic and short-lived.

Gymnosperms

  • Characteristics include production of "naked seeds".

  • Key Groups: Conifers, cycads, and ginkgos, primarily wind-pollinated.

Angiosperms

  • Flowering plants with key structures:

    • Flower Parts: Carpels (female) and stamens (male).

    • Pollinators: Various animals serve as vectors for pollination.

    • Importance of seeds and fruits in reproduction and dispersal.

Major Angiosperm Groups

  • Monocots: One seed leaf (e.g., grass, corn).

  • Dicots: Two seed leaves (e.g., beans, oaks).

Conclusion

  • Recap of plant evolution highlighting diversity in adaptations and ecological roles.