BIOLOGY Quiz 3 of the second semester

Energy in Ecosystems

Overview

All energy in ecosystems ultimately comes from the sun, serving as the foundational source for life on Earth.

Producers (Autotrophs)

  • Definition: Organisms that produce their own energy from nonliving sources.

  • Process: Most producers capture energy through photosynthesis, converting sunlight into chemical energy in the form of simple sugars.

  • Examples:

    • Plants: Utilize chlorophyll to absorb sunlight.

    • Some Bacteria: Such as cyanobacteria, perform photosynthesis under water.

    • Algae: Aquatic producers that are crucial for underwater ecosystems.

Consumers (Heterotrophs)

  • Definition: Organisms that obtain energy by consuming other living or once-living organisms.

  • Process: Consumers break down macromolecules within their food to release energy in the form of adenosine triphosphate (ATP) through cellular respiration.

  • Examples: Animals, most bacteria, and fungi.

Photosynthesis

  • Energy Source: Sunlight is converted to chemical energy.

  • Key Organisms: Plants, algae, and cyanobacteria are fundamental to photosynthesis, forming the base of food chains.

Chemosynthesis

  • Energy Source: Chemical reactions involving substances like sulfur and methane.

  • Key Organisms: Deep-sea vent bacteria utilize chemosynthesis in extreme environments where sunlight is absent.

Types of Consumers

  1. Herbivores: Organisms that consume only vegetation (e.g., rabbits, deer).

  2. Carnivores: Organisms that consume only meat (e.g., lions, hawks).

  3. Omnivores: Organisms that eat both plants and animals (e.g., bears, humans).

  4. Detritivores: Organisms that consume decomposing organic matter (e.g., earthworms, fungi).

Food Chains

  • Definition: Simple linear pathways showing the flow of energy between organisms that depict trophic levels, which indicate levels of nourishment.

  • Rule of 10: Refers to the preservation of energy as it flows through the food chain. Each organism generally retains only 10% of the energy from the previous level, as 90% is used for life processes or lost as heat.

Energy Flow in Food Chains

  1. Producers

  2. Primary Consumers (herbivores)

  3. Secondary Consumers (carnivores eating herbivores)

  4. Tertiary Consumers (carnivores eating other carnivores)

Food Webs

  • Definition: Complex models that illustrate multiple interconnected food chains within an ecosystem. They demonstrate the various pathways through which energy flows.

Trophic Pyramids

  • Energy Pyramid: Displays energy availability at each trophic level, consistently showing decreasing energy as one ascends the levels.

  • Numbers Pyramid: Represents the number of organisms at each trophic level. As energy diminishes, fewer organisms can be supported.

  • Biomass Pyramid: Illustrates the total mass of living organic matter at each trophic level, indicating how much organic material exists in the ecosystem at those levels.