21. Organisms and their Environment (Self-Study)

Organisms and their Environment

  • Study of interactions between organisms and their environments.

Key Concepts in Ecology

Environmental Factors

  • Biotic Factors: Living components that influence organisms (e.g. competition, predation, symbiosis).

  • Abiotic Factors: Non-living components affecting organisms (e.g. wind, rain, sunlight, temperature).

    • Example: In a stream, the water temperature (abiotic) affects fish, while food organisms (biotic) are crucial for sustenance.

Levels of Organization in Ecology

  • Population: A group of organisms of the same species.

  • Community: Interacting populations of different species.

  • Ecosystem: Interacting organisms in an area with their abiotic surroundings.

  • Habitat: Specific part of a community occupied by an organism.

Ecosystem Dynamics

  1. Energy Utilization

    • Ecosystems require both energy and inorganic nutrients.

    • Energy from the sun: Drives photosynthesis in plants, converting light energy into chemical energy.

    • Energy flow: Energy is passed from one organism to another; however, part is lost as heat.

  2. Inorganic Nutrients

    • Sourced from abiotic elements in the environment.

    • Cycles through ecosystems (e.g. nitrogen, phosphorus).

    • Nutrients are recycled while energy diminishes.

Flow of Energy and Nutrients

  • All organisms require energy obtained from food sources.

  • Energy conversion begins with photosynthesis in producers (e.g. plants), which store energy as glucose.

  • Nutrients from plants are consumed by herbivores and then passed along to carnivores, forming food chains.

  • Decomposers (e.g. bacteria, fungi) recycle nutrients back into the ecosystem upon the death of organisms.

Food Chains and Food Webs

  • Food Chain: Linear sequence of energy transfer (e.g. Grass → Rabbit → Hawk).

  • Food Web: A complex network of interlinked food chains illustrating feeding relationships.

  • Trophic levels correspond to energy flow:

    • Producers: First level (e.g. trees, algae).

    • Consumers: Secondary (herbivores) and tertiary levels (carnivores).

    • Decomposers break down organic matter, influencing all levels.

Ecological Pyramids

  • Illustrates trophic levels in food chains:

    • Pyramid of Energy: Shows total energy at each level; typically drops 90% between levels.

    • Pyramid of Numbers: Counts the number of organisms at each trophic level.

    • Pyramid of Biomass: Measures total biomass at each level; may vary (e.g. aquatic ecosystems).

    • Graphical representation indicates energy and biomass drops as you ascend trophic levels.

Nutrient Cycles

  • Nutrient Cycle: Transfer of chemical elements in ecosystems (carbon, nitrogen, phosphorus).

  • Carbon Cycle Processes: Photosynthesis, respiration, decomposition, combustion.

    • Plants absorb CO2 for photosynthesis; animals obtain carbon through eating.

    • Decomposition and combustion replenish CO2 in the atmosphere.

Importance of Biodiversity

  • Species diversity contributes to ecosystem stability and productivity.

  • Loss of a species can impair ecosystem functionality and recovery.

Learning Outcomes

  • Differentiate between food chains and webs, the roles of producers, consumers, and decomposers.

  • Interpret energy, number, and biomass pyramids.

  • Understand the carbon cycle's role and the need for biodiversity conservation.