Ecology Lecture 3: The Biosphere

Ecology Overview

• Biosphere: The portion of Earth that encompasses all ecosystems, comprising complex interrelated systems.
• Ecology Definition: The study of interactions between living (biotic) and non-living (abiotic) components in environments.

Ecological Levels

• Molecules: Smallest units of most chemical compounds; groups of atoms.
• Cells: The smallest functional units of life.
• Groups of Cells: Composed of tissues, organs, and organ systems.

Carrying Capacity

• Definition: Maximum number of organisms an area can support based on available resources and ecosystem's recycling abilities.

Nutritional Relationships

• Autotrophs: Organisms (plants) that synthesize their own food using inorganic compounds and energy (e.g., sunlight).
• Heterotrophs: Organisms (animals) that depend on other organisms for sustenance, cannot produce their own food.
  • Types of Heterotrophs:
    • Saprophytes: Feed on decaying organic matter (bacteria, fungi).
    • Herbivores: Consume plant matter.
    • Carnivores: Feed on other animals.
      • Predators: Hunt and eat prey.
      • Scavengers: Feed on dead animals.
    • Omnivores: Eat both plant and animal matter.

Symbiotic Relationships

• Symbiosis: Mutual, beneficial relationships between different species.

Energy Flow

• Energy Dynamics: Energy flows unidirectionally through ecosystems, originating from the sun and moving through producers to consumers and decomposers.
• Food Chain and Web: Represents energy transfer through various trophic levels, illustrating complex interactions and feeding relationships.
  • Energy Decrease: Energy diminishes with each trophic level, typically represented as 100% → 75% → 50% → 25% → 0%.

Food Web Interactions

• Producers: Primary source of energy in ecosystems, generating organic compounds from sunlight.
• Primary Consumers: Herbivores that feed on producers.
• Secondary Consumers: Carnivores that prey on primary consumers.
• Decomposers: Breakdown organic waste and dead organisms, recycling nutrients back into the environment.

Biomass and Climax Community

• Biomass: Total mass of living organisms in a particular area, decreases with each successive trophic level.
• Climax Community: A stable and self-perpetuating ecosystem dominated by a specific plant species until a significant disturbance occurs (e.g., fires, floods).

Niche and Habitat

• Niche: The role of an organism within its community, especially concerning food and interaction with other species.
• Habitat: The specific environment in which a plant or animal resides, providing necessary resources.

Material Cycles

• Recycling: Ecosystems must cycle materials among living organisms and their abiotic environment. The same materials can be reused.

Major Biogeochemical Cycles

• Carbon Cycle: Involves the movement of carbon through the environment, affecting various life forms and processes.
• Nitrogen Cycle: Essential for building proteins and nucleic acids; involves different forms of nitrogen utilized by living organisms.
• Phosphorus Cycle: Critical for energy transfer and genetic material.
• Water Cycle: Encompasses processes like evaporation, condensation, and transpiration, essential for ecosystem function.

Composition of Air

• Nitrogen: 78%
• Oxygen: 20.9%
• Other Gases: Includes Argon (>0.9%) and Carbon Dioxide (0.03%).

Biomes

• Oceans: Cover about 70% of Earth's surface and support diverse ecosystems.