Lecture+13+slides

Lecture Overview

• Topic: Flowering Plants (Angiosperms)

• Chapter: 30

Lecture Plan

1. What are angiosperms?

2. Angiosperm diversity

3. Pollination and pollination syndromes

4. Fruit

5. Angiosperm benefits and threats

Learning Outcomes

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

1. Contrast where pollen and embryos are created, and their roles.

2. Explain the importance of double fertilization and its influence on seed tissue.

3. Identify floral parts.

4. Compare types of flowers (complete vs incomplete, perfect vs imperfect) and plants (monoecious vs dioecious, monocot vs dicot).

5. Describe animal pollination.

6. Infer which pollinator (bee, butterfly, moth, or bird) is attracted to specific flowers.

7. Recall the four main tissues in fruits and compare fruit types.

8. Recall how humans utilize plants.

9. Explain the threats to plant species.

• Tip: Key terms are highlighted in bold.

What are Angiosperms?

• Definition: Seed plants with reproductive structures called flowers and fruits.

• Significance: Most widespread and diverse plant group

• Classification: >90% of all plants (approximately 250,000 species) included in the phylum Magnoliophyta (Anthophyta), derived from the Greek word anthos (flower).

Evolutionary Ancestry

• Ancestral Green Alga: Forebear of terrestrial plants.

• Lineage: Includes bryophytes (liverworts, mosses, hornworts) to vascular plants, moving towards seed plants (gymnosperms and angiosperms).

• Timeline: Angiosperms emerged around 140-200 million years ago.

Plant Groups and Dominance

• Plant Hierarchy:

  • Bryophytes: Nonvascular and seedless.

  • Vascular Plants: Include seedless (ferns, horsetails, etc.) and seed plants (gymnosperms, angiosperms).

  • Dominant Lifecycle: Angiosperms have reduced, dependent gametophytes (both male and female).

Characteristics of Flowering Plants

• Flowers: Specialized for sexual reproduction, often relying on animals for pollen transfer.

• Pollination Method: More directed compared to wind-pollination in gymnosperms.

Structures of Flowers

• Parts of Flower:

  • Stamens: Male part consisting of anther and filament.

  • Carpels: Female part consisting of stigma, style, ovary, and ovules.

  • Flowers: Contain sepals, petals, stamens, and carpels, structured in rings.

Gametophyte Development

• Male Gametophyte (Pollen): Formed in pollen grains from microspores in anthers.

• Female Gametophyte (Embryo Sac): Formed within ovules housed in ovaries.

Reproductive Adaptations

• Double Fertilization: Occurs when one sperm fertilizes the egg and the other fuses with two polar nuclei, forming a triploid endosperm.

• Significance: Ensures synchronization of embryo and endosperm development.

Angiosperm Diversity

• Types: Monocots, dicots, basal angiosperms, and magnoliids.

• Classification Change: Monocots classified as monophyletic, dicots as polyphyletic.

Pollination and Syndromes

• Pollination: Transfer of pollen grains from male to female structures is essential for reproduction.

• Co-Evolution: Pollinators influence flower morphology and vice versa.

• Pollination Syndromes: Traits that have evolved in response to the selection pressures imposed by different pollen vectors.

• Differences in Pollination Strategies:

  • Bees: Bright colors, nectar guides, sweet smells.

  • Butterflies: Bright colors and approachable shapes.

  • Moths: Strong sweet odor and night opening.

  • Birds: Bright red/yellow colors, large and sturdy flowers.

Fruits: Understanding and Classification

• Definition: A mature ovary containing seeds.

• Functions: Dispersal of seeds through various methods: fleshy (animal-dispersed) or dry (wind- or water-dispersed).

• Fruit Types:

  • Simple Fruits: Either dry or fleshy, arising from one pistil.

  • Aggregate Fruits: From several pistils of a single flower.

  • Multiple Fruits: From many flowers in an inflorescence.

Benefits of Angiosperms

• Human Relevance: Major contributions in medicine, food production, and construction materials.

• Threats: Over one-fifth of plant species face extinction due to habitat loss, climate change, and human activities.