Angiosperms Summary

Angiosperms Overview

• Reproductive Structures: Angiosperms possess flowers and fruits.
• Diversity: They are the most widely distributed and diverse plant group.

Classification

• Main Groups:
  • Monocots: One cotyledon (e.g., lilies, orchids, grasses).
  • Dicots: Two cotyledons (e.g., elms, roses, peas).
• Recent studies suggest that many species previously classified as dicots now belong to a clade called Eudicots.

Key Adaptations

• Flowers:
  • Specialized shoots with modified leaves.
  • Components include:
  • Sepals: Enclose flower.
  • Petals: Attract pollinators.
  • Stamens: Produce pollen.
  • Carpels: Produce ovules.
• Fruits:
  • Formed when the ovary wall thickens; help protect seeds and aid in dispersal.
  • Can be fleshy or dry.

Flower Structure

• Flowers may be complete (all four organs) or incomplete (lacking one or more organs).
• Symmetry and organization of stamens and carpels can vary.

Seeds and Dispersal

• Seeds can disperse through:
  • Wind: e.g., dandelions,
  • Water: e.g., coconuts,
  • Animals: help in spreading seeds.
• Some seeds require a period of rough treatment for germination.

Angiosperm Lifecycle

• Sporophyte: Dominant phase with both male (anthers) and female (ovaries) structures.
• Gametophytes: Male gametophytes within pollen grains, female gametophytes (embryo sacs) within ovaries.
• Fertilization can occur via self-fertilization or cross-pollination.
• Double Fertilization: Unique to angiosperms where one sperm fertilizes the egg, and the other forms the endosperm.
• Endosperm: Provides nourishment to the developing embryo.

Seed Structure

• Cotyledons: Two leaves in dicots; one in monocots.
• Contains endosperm for embryo nourishment.

Economic Importance

• Major food sources derived from angiosperms (e.g., wheat, rice, maize).
• Seed plants contribute to medicine and provide wood materials.