Ecology and Ecosystems
Grade 10 · Science · Study Guide
Explore how living organisms interact with each other and their environment in complex, interconnected ecosystems.
Ecology is the scientific study of how organisms interact with each other and with their physical environment. An ecosystem includes all the living organisms (biotic factors) and the nonliving components (abiotic factors — such as temperature, water, sunlight, and soil) in a given area. Energy flows through ecosystems in one direction: from the sun through producers (plants, algae) to primary consumers (herbivores), secondary consumers (carnivores), and decomposers.
Food webs map the complex feeding relationships in an ecosystem and show how energy moves between trophic levels. A general rule is that only about 10% of the energy at one trophic level transfers to the next — the rest is lost as heat. This '10% rule' explains why ecosystems can support fewer top predators than prey animals.
Ecosystems also cycle nutrients through biogeochemical cycles — the water cycle, carbon cycle, and nitrogen cycle being critical examples. Disruptions to ecosystems, such as habitat loss, invasive species, and climate change, can have cascading effects. Biodiversity — the variety of life in an ecosystem — increases ecosystem resilience, helping it recover from disturbance.
| Trophic Level | Example | Energy Available (kJ) |
|---|---|---|
| Producers (Level 1) | Grass | 10,000 |
| Primary Consumers (Level 2) | Grasshoppers | 1,000 |
| Secondary Consumers (Level 3) | Frogs | 100 |
| Tertiary Consumers (Level 4) | Hawks | 10 |
Key terms
- Ecosystem
- A community of organisms plus the abiotic (nonliving) environment they interact with.
- Biotic factor
- Living components of an ecosystem, including plants, animals, fungi, and microorganisms.
- Abiotic factor
- Nonliving components of an ecosystem such as temperature, water, sunlight, and minerals.
- Trophic level
- A feeding level in a food chain or web; producers are level 1, primary consumers level 2, etc.
- Biodiversity
- The variety of life forms in a given ecosystem or on Earth; higher biodiversity increases resilience.
- Decomposer
- Organisms (bacteria, fungi) that break down dead organic matter, recycling nutrients back into the ecosystem.
Flashcards
- Producer
- Organism that makes its own food via photosynthesis or chemosynthesis; base of the food chain.
- Consumer
- Organism that obtains energy by eating other organisms.
- Food web
- A diagram showing the complex network of feeding relationships among organisms in an ecosystem.
- Carrying capacity
- The maximum population size an environment can sustainably support given available resources.
- Trophic cascade
- Indirect effects that ripple through a food web when a predator population changes.
- Biogeochemical cycle
- The cycling of chemical elements (like carbon, nitrogen, water) through living organisms and the environment.
Practice questions
Which trophic level contains organisms that make their own food through photosynthesis?
- Primary consumers
- Secondary consumers
- Producers
- Decomposers
Show answer
Answer: Producers
Producers (plants, algae, some bacteria) convert sunlight into chemical energy via photosynthesis — they form the foundation of every food chain.
According to the 10% rule, only 10% of energy is transferred from one trophic level to the next.
Show answer
Answer: True
The 10% rule states that approximately 10% of the energy stored at one trophic level is available to the next; the other 90% is lost as heat or used in metabolism.
The nonliving components of an ecosystem, such as temperature and water, are called ___ factors.
Show answer
Answer: abiotic
Abiotic factors are the nonliving physical and chemical components of an ecosystem. Biotic factors are the living components.
Which of the following best describes biodiversity's role in an ecosystem?
- Increases competition only
- Reduces energy efficiency
- Increases ecosystem resilience
- Decreases food web complexity
Show answer
Answer: Increases ecosystem resilience
Higher biodiversity means more species can fill ecological roles, so if one species declines, others can compensate — making the ecosystem more stable and resilient.
Decomposers return nutrients to the environment by breaking down dead organic matter.
Show answer
Answer: True
Decomposers like fungi and bacteria break down dead matter into simpler compounds, releasing nutrients back into the soil and water for producers to use.
Fun facts
- A single oak tree can support over 500 species of insects, birds, and other organisms — a whole ecosystem in itself.
- Wolves reintroduced to Yellowstone in 1995 changed the behavior of elk, which allowed riverbanks to revegetate, altering the course of rivers — a 'trophic cascade.'
- Decomposers are so efficient that all the carbon in your body will be recycled back into the environment within decades of your death.
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