Lecture_13_slides

Lecture 13: Overview

• Topic: Flowering Plants Overview

• Course: Bio 80, Chapter 30

Lecture Plan

• 1. What are angiosperms?

• 2. Angiosperm diversity

• 3. Pollination & pollination syndromes

• 4. Fruit

• 5. Angiosperm benefits & threats

Lecture Outcomes

• Understand the creation and roles of pollen and embryos.

• Explain the significance of double fertilization, impacting seed tissue.

• Identify floral parts.

• Compare various types of flowers: complete vs. incomplete, perfect vs. imperfect.

• Describe animal pollination dynamics.

• Predict which flower types are favored by specific pollinators (bees, butterflies, etc.).

• Recall the four main fruit tissues and compare fruit types.

• Understand human usage of plants.

• Recognize the threats to plant survival.

Part 1: Angiosperms

• Definition: Seed plants with flowers and fruits, dominating the plant kingdom.

  • Over 90% of all plants (approximately 250,000 species).

  • Classified in phylum Magnoliophyta (or Anthophyta), from Greek "anthos" meaning flower.

Evolutionary Background

• Ancestors of angiosperms:

  • Origin from green algae; progression through bryophytes, vascular plants, gymnosperms.

• Evolution timeline of land plants:

  • Appearance of angiosperms around 50 million years ago.

Plant Classification

• Angiosperms are categorized as:

  • Monocots

  • Dicots

  • Basal angiosperms

  • Magnoliids

• Monocots: One cotyledon, parallel leaf veins, scattered vascular tissues.

• Dicots: Two cotyledons, net-like leaf veins, ring-structured vascular tissues.

Floral Structure

• Parts of Flowers:

  • Stamen: Male part – includes anther and filament.

  • Carpel (Pistil): Female part – includes stigma, style, ovary.

  • Petals and Sepals: Attract and protect.

• Flowers can be:

  • Complete: All four flower organ types present.

  • Incomplete: Lacking one or more organs.

• Perfect vs. Imperfect:

  • Perfect: Contains both male and female structures.

  • Imperfect: Missing one sex (male or female).

Pollination Mechanism

• Pollination involves pollen transfer from anther to stigma, facilitated mostly by animals, making it more directed than in gymnosperms.

• Double Fertilization Process:

  • Pollen grain lands on stigma, forming pollen tube that reaches ovule.

  • Two sperm cells; one fertilizes the egg, while the other forms the triploid endosperm (nutrient support for the embryo).

Types of Fruits

• Fruits develop from the ovary after fertilization, including:

  • Fleshy Fruits: Mesocarp is fleshy - edible and helps in seed dispersal.

  • Dry Fruits: Hard outer structure; typically non-edible for seed dispersal.

• **Classification based on Development:

  • Simple fruits (single ovary), Aggregate fruits (multiple pistils from one flower), Multiple fruits (fusion from multiple flowers).

Angiosperm Benefits to Humans

• Medicinal Uses: Source of drugs (e.g., Taxol for cancer).

• Wood Products: Major construction and fuel source.

• Crops: Major food sources, 6 crops provide 80% of calories.

Threats to Angiosperms

• Extinction Risks: Over 1/5 of plants at risk; factors include climate change, habitat loss, and human impact.

• Example: Tiehm's buckwheat endangered by mining operations.

Questions for Review

• Discuss the differences in life cycles between angiosperms and gymnosperms.

• What are the implications of pollinator decline on angiosperm reproduction?