Lecture+11+slides

Lecture Overview

• Title: Lecture 11: Plants 1 - Non-Vascular and Non-Seed Bearing Plants

• Course: Bio 80

• Study Focus:

  • Define plants

  • Explore the evolutionary history of plants

  • Differentiate non-vascular plants from seedless vascular plants

Weekly Plan

• Review: Lecture exam 1

• Topics to Cover:

  • Finish lecture 10

  • Lecture 11 topics:

    • What are plants?

    • The evolution of plants

    • Nonvascular plants

    • Seedless vascular plants

Lecture Exam 1 Review

• Instructions:

  • Look over your exam for questions or regrades

  • Token earning opportunity – "Exam Wrapper" due next Tuesday, worth 1 token

Lecture Outcomes

By the end of this lecture, students should be able to:

1. List and describe important uses of plants by humans.

2. Describe plant evolution from green algae to terrestrial life.

3. Compare land plants with charophytes (green algae).

4. Discuss pros and cons of life on land and how plants overcame challenges.

5. Explain alternation of generations in bryophytes and ferns.

6. Recall different types of bryophytes: liverworts, mosses, hornworts.

7. Discuss ferns' adaptations that enhanced their success on land.

• Tip: Important terms are highlighted in bold.

What are Plants?

• Definition:

  • Typically autotrophic organisms lacking motility, with cellulose-based cell walls.

  • Use growth instead of movement to acquire resources.

  • Characterized by alternation of generations in life cycles.

• Classification:

  • Multicellular terrestrial organisms evolved from green algae, emphasizing photosynthesis and unique life cycles.

Evolution of Plants

• Ancestry:

  • Plants evolved from green algae approximately 470 million years ago.

  • Major developments by 425 million years ago included traits for terrestrial life:

    • Reproductive structures

    • Photosynthetic branches

    • Soil anchoring systems

• Shared Traits with Charophytes:

  • Peroxisome enzymes

  • Structure of flagellated sperm

  • Formation of the phragmoplast

  • Cellulose synthesis complexities

  • DNA sequence similarities across organelles.

Pros and Cons of Terrestrial Life

• Pros:

  • Unfiltered sunlight

  • Increased CO2 availability

  • Nutrient-rich soil

• Cons:

  • Water scarcity

  • Effects of gravity

  • Increased vulnerability of gametes and offspring.

Traits of Land Plants

1. Alternation of Generations: Includes multicellular, dependent embryos.

2. Walled Spores: Produced in specialized sporangia for resilience in dry conditions.

3. Multicellular Gametangia: Distinct structures for egg (archegonium) and sperm (antheridia) formation.

4. Apical Meristems: Zones for growth and tissue differentiation.

5. Other Traits:

• Development of a cuticle for protection against desiccation.

• Symbiosis with mycorrhizal fungi enhancing nutrient absorption.

• Secondary compounds for defense against herbivores and pathogens.

Nonvascular Plants Overview

• Definition:

  • Nonvascular plants (bryophytes) lack vascular tissues and seeds, comprising about 7% of plant species.

• Phyla:

  • Bryophyta (mosses)

  • Hepatophyta (liverworts)

  • Anthocerophyta (hornworts)

• Characteristics of Mosses:

  • Approx. 15,000 species; thrive in moist habitats; critical for soil stabilization and habitat colonization.

Examples of Nonvascular Plants

• Mosses: Key species include peat mosses and rock mosses.

• Liverworts: Thallus structure, gemmae cups for asexual reproduction.

• Hornworts: Unique sporangium release mechanism, association with nitrogen-fixing bacteria.

Seedless Vascular Plants Overview

• Transition:

  • Seedless vascular plants show dominance of sporophytes; lineage includes ferns and their relatives.

• Characteristics of Vascular Plants:

  • Vascular tissue enables nutrient and water transport, allowing growth to significant heights.

  • Roots anchor plants; leaves facilitate light capture for photosynthesis.

  • Differences between microphylls (single vein) and megaphylls (branched veins).

• Reproduction: Varied modes including homosporous and heterosporous spore production.

Summary of Important Concepts

• Understand the key evolutionary transitions in plant history, differences among major plant groups, and the overall ecological significance of plants in habitats and human benefits.