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.