3. Ecology

Ecosystem Components

• Ecology: Focuses on how organisms interact with each other and their nonliving environment.

  • Ecologists study five levels of matter: Biosphere, Ecosystems, Communities, Population, and Organisms.

• Ecosystem Components:

  • Biotic: Decomposers, Producers (Autotrophs & Chemotrophs), and Consumers (Herbivores, Carnivores, Omnivores, and Detritivores).

  • Abiotic: Light, Soil, Water, Temperature, and Climate.

3 Major roles in our ecosystem

• 1. Producers: Organisms that make their own nutrients from compounds and energy from their environment (e.g., green plants).

  • Photosynthesis: CO2 + H2O + \text{Solar Energy} \rightarrow C6H{12}O6 + O2

• 2. Consumers: Organisms that cannot produce their own food and feed on other producers or consumers.

  • Primary Consumers: Herbivores (plant eaters).

    • Examples: Caterpillars, Zooplankton.

  • Carnivores: Meat eaters.

  • Secondary Consumers: Feed on herbivores or other carnivores.

    • Examples: Tigers, Hawks (tertiary consumers).

  • Omnivores: Eat both plants and animals.

    • Examples: Pigs, Rats, Humans.

• 3. Decomposers: Break down wastes of plants and animals, returning nutrients to the soil, water, and air.

  • Examples: Bacteria and Fungi.

Other consumers or detritivores

• Detritivores: Get nutrients by feeding on the dead bodies of organisms.

  • Examples: Earthworms, Soil Insects.

• Respiration: Producers, consumers, and decomposers use chemical energy stored in glucose via respiration.

  • C6H{12}O6 + O2 \rightarrow CO2 + H2O + \text{Energy}

Energy in an Ecosystem

• Energy Flow: Chemical energy flows through ecosystems from one trophic level to another via food chains and food webs.

• Food Chains: Sequence of organisms where each serves as a nutrient/energy source for the next level.

• Energy Loss: Energy is lost as low-quality heat (Second Law of Thermodynamics); energy loss at each trophic level is the pyramid of energy flow. Approximately 90% energy loss at each level.

• Food Web: A complex network of interconnected food chains in an ecosystem.

• Trophic Levels: Steps in a food chain or ecological pyramid where transfer of food/energy occurs.

Matter in an Ecosystem

• Nutrient Cycle: Elements and compounds cycle through air, water, soil, rock, and living organisms.

• Driven by solar energy and Earth's gravity.

• Includes cycles for water, carbon, nitrogen, and phosphorus.

• Human activities are altering these cycles.

• Water Cycle:

  • Solar energy causes evaporation; water vapor condenses into clouds; gravity returns water as precipitation.

  • Precipitation becomes surface runoff, some evaporates, some seeps into soil (used by plants or becomes groundwater).

  • Groundwater collects in aquifers.

  • Human impacts: withdrawing fresh water, clearing vegetation, draining wetlands.

• Carbon Cycle:

  • Carbon compounds circulate through the biosphere, atmosphere, hydrosphere, and geosphere; CO2 is a key component.

  • Photosynthesis removes CO2; respiration adds CO2.

  • CO2 dissolves in ocean water.

  • Human impacts: burning fossil fuels (adds CO2), deforestation (reduces CO2 removal).

• Nitrogen Cycle:

  • Nitrogen gas (N2) is converted to usable forms (NH3, NH4, NO3) by bacteria and lightning. This process is essential for plant growth, as nitrogen is a critical component of amino acids and nucleic acids, enabling the synthesis of proteins and DNA.

  • Human impacts: burning fuels (creates nitric oxide, leading to acid deposition).