Study Notes
Energy flow in ecosystems begins with the Sun, which is the principal source of energy input. Energy is transferred through food chains and food webs, starting with producers and moving through consumers and decomposers.
- Sun — the principal source of energy input to biological systems. Example: Provides light and heat energy to ecosystems.
- Food chain — shows the transfer of energy from one organism to the next, beginning with a producer. Example: Grass → Rabbit → Fox.
- Food web — a network of interconnected food chains. Example: Multiple food chains in a forest ecosystem.
- Producer — an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis. Example: Plants, algae.
- Consumer — an organism that gets its energy by feeding on other organisms. Example: Humans, animals.
- Herbivore — an animal that gets its energy by eating plants. Example: Cow, deer.
- Carnivore — an animal that gets its energy by eating other animals. Example: Lion, hawk.
- Decomposer — an organism that gets its energy from dead or waste organic matter. Example: Bacteria, fungi.
- Ecosystem — a unit containing all of the organisms and their environment, interacting together, in a given area. Example: A lake.
- Trophic level — the position of an organism in a food chain or food web. Example: Producers are at the first trophic level.
- Autotrophic nutrition — the mode of nutrition in which organisms make their food by themselves. Example: Plants using photosynthesis.
- Heterotrophic nutrition — organisms depend on other organisms for food. Example: Humans, animals.
- Saprotrophic nutrition — involves organisms that depend on dead and decaying matter for their food. Example: Decomposers like bacteria.
Exam Tips
Key Definitions to Remember
- Sun
- Food chain
- Food web
- Producer
- Consumer
- Herbivore
- Carnivore
- Decomposer
- Ecosystem
- Trophic level
- Autotrophic nutrition
- Heterotrophic nutrition
- Saprotrophic nutrition
Common Confusions
- Confusing food chains with food webs
- Misunderstanding the role of decomposers in ecosystems
Typical Exam Questions
- What is the principal source of energy input to biological systems? The Sun.
- How does energy flow through a food chain? Energy flows from producers to consumers and then to decomposers.
- What is the role of a decomposer in an ecosystem? Decomposers break down dead organic matter, returning nutrients to the environment.
What Examiners Usually Test
- Understanding of energy flow through ecosystems
- Ability to differentiate between producers, consumers, and decomposers
- Knowledge of trophic levels and their significance in food chains and webs