Lecture 14 - Plant Characteristics, Evolution, and Ecology 2024

Overview of Plant Characteristics, Evolution, and Ecology

• Focus on five plant lineages: green algae, nonvascular plants, seedless vascular plants, gymnosperms, angiosperms.

• Key questions to consider for each lineage:

  • Ecosystems inhabited

  • Adaptations for terrestrial life:

    • Tissues and organs

    • Cuticle and stomata

    • Vascular tissue and lignin

    • Spores, seeds, fruits

  • Nutrient and water acquisition

  • Ecological importance and impacts on biological production and biodiversity.

Green Algae (Lineage 1)

Ecosystems

• Inhabits aquatic environments.

Characteristics

• Organisms can be unicellular or multicellular.

• Generally consist of similar cell types, lacking tissues or organs.

Nutrient and Water Acquisition

• Absorption of:

  • Carbon dioxide

  • Nitrogen

  • Phosphorus

  • Water across cell membrane.

Ecological Importance

• Photosynthesis contributes to biological production, providing resources:

  • Food to consumers

  • Oxygen production

  • Habitat support.

Nonvascular Plants (Lineage 2)

Ecosystems

• Found in aquatic and wet terrestrial habitats.

Characteristics

• Cells organized into tissues and organs.

• Presence of cuticle and stomata:

  • Cuticle prevents water loss.

  • Stomata facilitate gas exchange.

• Low-lying growth form (no vascular tissue).

• Embryo is released from the plant in a desiccation-resistant spore.

Nutrient and Water Acquisition

• Rhizoids anchor the plant to the substrate (soil, wood, rock) and absorb:

  • Water

  • Nitrogen

  • Phosphorus.

• Carbon dioxide is absorbed through stomata.

Ecological Importance

• Provided resources (food, habitat, oxygen) vital for the evolution of terrestrial consumers.

• Contributed to increased biological production and biodiversity.

Seedless Vascular Plants (Lineage 3)

Ecosystems

• Thrive in both aquatic and wet terrestrial habitats.

Characteristics

• Presence of:

  • Cuticle and stomata

  • Vascular tissue for water/nutrient transport (xylem and phloem).

  • Lignin for structural support.

• Embryo released in a desiccation-resistant spore.

Nutrient and Water Acquisition

• Xylem transports:

  • Water

  • Nitrogen

  • Phosphorus from roots to cells.

• Phloem conducts carbohydrates from photosynthetic cells to roots.

Ecological Importance

• Enabled taller growth forms to occupy drier habitats.

• Increased species diversity and plant abundance supports diverse ecosystems and higher trophic levels.

Gymnosperms (Lineage 4)

Ecosystems

• Predominantly terrestrial.

Characteristics

• Contains:

  • Cuticle and stomata

  • Vascular tissue and lignin

  • Seeds encapsulating the embryo, protecting against desiccation and providing nutrients.

Nutrient and Water Acquisition

• Utilizes a vascular system similar to seedless vascular plants.

Ecological Importance

• Capable of reproducing in dry habitats.

• Increased availability of food and habitat resources leads to greater biological production and biodiversity.

Angiosperms (Lineage 5)

Ecosystems

• Found in both terrestrial and aquatic environments.

Characteristics

• Presence of:

  • Cuticle and stomata

  • Vascular tissue and lignin

  • Seeds surrounded by fruit that protects the embryo.

Nutrient and Water Acquisition

• Similar to previous lineages, utilizing a vascular system.

Ecological Importance

• Emergence of flowers and fruits enhances food resources for primary consumers, contributing to biological production and biodiversity.

Life Cycle Differences: Nonvascular vs. Angiosperms

Nonvascular Plants

• Mature plant: Gametophyte (n).

• Fertilization: Male gamete requires water to reach the egg.

• Development: Plant develops from spores.

• Adaptations: Spores enable survival in dry conditions and effective dispersal.

Angiosperms

• Mature plant: Sporophyte (2n).

• Fertilization: Pollen grains (resistant to desiccation) allow reproduction without water.

• Development: Plant develops from seeds.

• Adaptations: Seeds protect embryos and allow dispersal by wind or animals.