Angiosperms, the flowering plants, are incredibly diverse thanks to their relationships with animals. These partnerships have led to specialized pollination methods and seed dispersal strategies, driving the evolution of both plants and animals.

Seed plants, including angiosperms and gymnosperms, have unique structures that aid their survival. From vascular tissues for nutrient transport to seeds for reproduction, these adaptations have helped plants thrive in various environments and play crucial ecological roles.

Angiosperm Diversity and Pollination

Animal contributions to angiosperm diversity

• Animal pollination promotes genetic diversity in angiosperms
  • Cross-pollination introduces genetic variation leads to increased diversity (hybridization)
  • Animals transport pollen over long distances enables gene flow between populations (birds, bees)
• Coevolution between angiosperms and pollinators drives specialization
  • Plants develop specific floral traits to attract certain pollinators (color, shape, scent)
  • Pollinators adapt to efficiently exploit floral resources (long tongues, specialized mouthparts)
  • Specialization leads to development of new species and increased diversity (orchids, hummingbirds)
• Animal seed dispersal expands the range of angiosperms
  • Animals consume fruits and disperse seeds to new habitats (birds, mammals)
  • Seed dispersal by animals allows angiosperms to colonize new areas promotes diversity (islands, disturbed sites)

Pollination mechanisms in seed plants

• Wind pollination
  • Pollen is lightweight and produced in large quantities
  • Flowers are typically small, inconspicuous, lack nectar or scent
  • Examples include grasses, sedges, many trees (oak, birch, pine)
• Animal pollination
  • Flowers attract pollinators with showy petals, scent, nectar rewards
  • Pollen grains are often sticky or barbed to adhere to animal bodies
  • Pollinators include:
    1. Insects (bees, butterflies, moths)
    2. Birds (hummingbirds, sunbirds)
    3. Mammals (bats, rodents)
• Self-pollination
  • Pollen from a flower fertilizes the same flower or another flower on the same plant
  • Ensures reproduction in absence of pollinators or when cross-pollination is limited
  • Can lead to reduced genetic diversity over time (inbreeding depression)

Ecological Importance and Deforestation

Ecological importance of plants vs deforestation

• Plants are primary producers form foundation of most terrestrial ecosystems
  • Convert solar energy into chemical energy through photosynthesis ($6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$)
  • Provide food and habitat for countless animal species (insects, birds, mammals)
  • Play crucial role in nutrient cycling and soil formation (nitrogen fixation, decomposition)
• Plants regulate Earth's climate and atmosphere
  • Absorb carbon dioxide and release oxygen during photosynthesis
  • Help mitigate effects of climate change by storing carbon in biomass and soil
  • Influence local and regional weather patterns through transpiration and albedo
• Deforestation has severe consequences for biodiversity
  • Habitat loss is primary cause of species extinctions (tropical rainforests)
  • Fragmentation of forests isolates populations disrupts gene flow
  • Loss of keystone species can trigger cascading effects on ecosystem stability (elephants, jaguars)
• Deforestation alters ecosystem services and functions
  • Reduced carbon sequestration increased greenhouse gas emissions
  • Disruption of water cycles leads to changes in precipitation patterns and soil erosion
  • Loss of medicinal plants potential sources of new drugs and materials (rosy periwinkle, quinine)

Seed Plant Structure and Development

Vascular tissue and plant structure

• Seed plants contain vascular tissue for efficient transport of water and nutrients
  • Xylem transports water and minerals from roots to shoots
  • Phloem distributes sugars and other organic compounds throughout the plant

Seed structure and components

• Seeds contain an embryo, food supply, and protective covering
  • Embryo develops into a new plant upon germination
  • Endosperm provides nutrients for the developing embryo
  • Seed coat protects the embryo and food supply from damage and desiccation
• Cotyledons are embryonic leaves that may store food or aid in initial growth

Types of seed plants

• Gymnosperms (e.g., conifers) produce naked seeds not enclosed in fruits
• Angiosperms produce seeds enclosed within fruits