Ecology and Human Impact
Grade 8 · Science · Study Guide
Explore how living things interact with each other and their environment, and how human activities affect ecosystems.
Ecology is the scientific study of how organisms interact with each other and with their physical environment. An ecosystem includes all living organisms (biotic factors) and nonliving components (abiotic factors) in a particular area, such as a forest, pond, or desert.
Energy flows through ecosystems via food chains and food webs. Producers (plants and algae) capture energy from sunlight through photosynthesis. Consumers eat producers or other consumers. Decomposers break down dead organisms, returning nutrients to the soil.
Ecosystems also cycle nutrients. The carbon cycle, nitrogen cycle, and water cycle are essential processes that recycle matter through living and nonliving components of the environment.
Human activities significantly alter ecosystems. Deforestation destroys habitats and reduces biodiversity. Burning fossil fuels releases CO₂, contributing to climate change by enhancing the greenhouse effect. Pollution contaminates water, air, and soil. Overfishing depletes fish populations faster than they can recover. Invasive species introduced by humans can outcompete native species and disrupt ecosystems.
Conservation efforts include establishing protected areas, restoring habitats, reducing emissions, sustainable fishing practices, and protecting endangered species. Biodiversity — the variety of species in an ecosystem — is critical to ecosystem resilience and stability.
Key terms
- Ecosystem
- A community of living organisms interacting with each other and with their nonliving environment in a specific area
- Biodiversity
- The variety of different species of organisms in a given area; higher biodiversity generally means a more resilient ecosystem
- Food web
- A complex network of overlapping food chains showing the feeding relationships in an ecosystem
- Greenhouse effect
- The process by which certain gases in the atmosphere trap heat from the Sun, warming Earth's surface
- Deforestation
- The large-scale removal of forests, which destroys habitats, reduces biodiversity, and contributes to climate change
- Invasive species
- A non-native species introduced to a new environment where it has no natural predators and can disrupt the existing ecosystem
Flashcards
- Producer
- An organism that makes its own food through photosynthesis; the base of most food chains
- Consumer
- An organism that obtains energy by eating other organisms
- Decomposer
- An organism (like bacteria or fungi) that breaks down dead matter and returns nutrients to the ecosystem
- Food chain
- A linear sequence showing the flow of energy from one organism to the next through feeding relationships
- Abiotic factors
- Nonliving components of an ecosystem, such as temperature, sunlight, water, and soil
- Habitat destruction
- The process by which natural habitats are damaged or eliminated, threatening the species that live there
- Sustainability
- Using natural resources in a way that meets current needs without compromising the ability of future generations to meet theirs
Questions
Which of the following is an example of a biotic factor in an ecosystem?
- Temperature
- Soil composition
- Rainfall
- A deer
Show answer
Answer: A deer
Biotic factors are living components of an ecosystem. A deer is a living organism, while temperature, soil, and rainfall are abiotic (nonliving).
Decomposers are consumers that eat other animals.
Show answer
Answer: False
Decomposers (like fungi and bacteria) break down dead organisms and organic waste — they do not eat living animals the way carnivore consumers do.
The variety of different species in an ecosystem is called ______.
Show answer
Answer: biodiversity
Biodiversity refers to the number and variety of species in an area; it is a key indicator of ecosystem health and resilience.
How do humans most directly contribute to climate change?
- By building cities
- By burning fossil fuels, which releases CO₂
- By farming crops
- By using electric cars
Show answer
Answer: By burning fossil fuels, which releases CO₂
Burning fossil fuels (coal, oil, natural gas) releases large amounts of CO₂ and other greenhouse gases, trapping heat and driving climate change.
Invasive species can disrupt native ecosystems by outcompeting native organisms.
Show answer
Answer: True
Invasive species often have no natural predators in their new environment, allowing them to outcompete native species for food and habitat.
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