Evolution and Diversity of Multicellular Organisms (#15)

Evolution and Diversity of Multicellular Organisms

Office Hours and Quiz Details

• Office Hours: 4:00-5:50 PM
• Quiz 3: Next Thursday, includes multiple choice and short answer
• Format: 15 minutes at the start of class; study actively without notes
• Exit Ticket: Due within 24 hours of class finishing

Study Preparation Strategies

• Bloom's Taxonomy: Practice at various levels
• Supervised Instruction (SI) Worksheets: Complete for additional support
• Flashcards: Define key terms actively
• Concept Map: Create a diagram of major lines of evidence for the evolutionary transition of tetrapods
• Quick Write Task: Describe key challenges for plants and animals transitioning from water to land

Sample Exam Questions

• Compare and contrast lobe-finned fishes and tetrapods
• Identify characteristics of lobe-finned fishes and tetrapods
• Describe expected traits in transitional fossils

Objectives in Plant Diversity

• Plant Traits: Discuss what unites land plants and distinguishes them from other organisms
• Challenges for Land Plants: Identify major challenges and key innovations for terrestrial living
• Morphological Features: Describe and classify major morphological and developmental features among plant groups

Warm-Up Activities

• Brainstorming: Discuss advantages and challenges of transitioning from water to land

Challenges for Early Land Plants

• Desiccation Resistance: Need for adaptations to retain water
• Structural Support: Mechanisms to withstand gravity without water's buoyancy
• Water Management: Adaptations for regulating osmolarity in freshwater and saltwater environments

Advantages for Transitioning to Land

• Photosynthetic Efficiency: More sunlight available for photosynthesis
• Phototropism: Growth towards light leading to evolution from simple to complex structures
• Light Competition: Taller plants can avoid shading from competitors

Evolutionary Timeline of Plant Groups

• Early plants originated ~470 million years ago (mya)
• Bryophytes (Nonvascular Plants): Liverworts, Hornworts, Mosses
• Vascular Plants: Origin around ~425 mya
  • Seedless Vascular Plants: Lycophytes and Monilophytes
  • Seed Plants: Include Gymnosperms (~360 mya) and Angiosperms

Seedless Vascular Plants

• Reproduction: Use spores rather than seeds
• Structure: Have a 3D structure with specialized tissues
• Vascular System: Comprises transport tissues for water and nutrients

Advantages of Plant Structures

• Roots:

  • Anchor plants in soil
  • Absorb water and nutrients (Nitrogen, Phosphorus, Potassium)
  • Store food reserves

• Stems:

  • Provide structure and support
  • Transport water and nutrients
  • Connect roots to leaves

• Leaves:

  • Site for photosynthesis
  • Gas exchange regulation (O₂ and CO₂)
  • Control water loss via transpiration

Vascular Tissues and Their Functions

• Xylem: Transports water throughout the plant, essential for plant hydration
• Phloem: Transports nutrients and sugars from production sites (leaves) to other areas of the plant

Environmental Impact of Seedless Vascular Plants

• Seedless vascular plants once formed vast forests, influencing CO₂ levels
  • Led to a cooling planet and the formation of glaciers (Ice Age)

Fossil Fuels and Climate Impact

• Fossil fuels originated from ancient plant remains; burning these fuels increases atmospheric CO₂ levels
• Carbon Cycle Disruption: Sudden release of ancient carbon into the atmosphere contributes to climate change

Key Adaptations of Seed Plants

• Pollen and Seeds: Reduces dependency on water for reproduction and enhances dispersal mechanisms
• Advantages include:
  • Increased independence from water
  • Enhanced gamete protection

Gymnosperm vs. Moss Reproduction

• Moss Reproduction: Requires proximity of gametophytes in wet environments, with swimming sperm
• Gymnosperms: Male gametophytes (pollen) can travel further, less dependent on water for fertilization

Flowering Plants and Pollination Strategies

• For insect-pollinated flowering plants, timing is crucial to maximize reproductive success

Exit Ticket Questions

1. Discuss the evolutionary advantage of vascular tissue in plants and its contribution to their success.
2. Describe the evolutionary benefits of flowers in flowering plants and how this has led to their dominance in ecosystems.