Ecosystems and Biomes
Grade 5 · Science · Study Guide
Discover how living things and their environments form complex, interconnected systems around the world.
An ecosystem is all the living things (plants, animals, fungi, bacteria) in an area PLUS the non-living things (water, soil, sunlight, air temperature) they interact with. Everything in an ecosystem is connected — change one part and you affect the whole system. When wolves were removed from Yellowstone National Park, deer populations exploded, overgrazing destroyed riverside vegetation, which caused rivers to erode and change course. When wolves were reintroduced, the whole ecosystem — including the rivers — recovered. Scientists call this a trophic cascade.
A biome is a large region of Earth characterized by its climate and the types of plants and animals that live there. Earth has several major biomes: tropical rainforests (hot, rainy, incredibly diverse), deserts (hot or cold, very little rain), grasslands (flat, grassy, moderate rainfall), temperate forests (four seasons, deciduous trees), taiga (cold, conifer forests), and tundra (frozen ground, treeless, extreme cold). The ocean is sometimes counted as its own biome.
Each biome has characteristic plants and animals that are adapted to survive there. A cactus stores water in its thick stem to survive desert droughts. An arctic fox has white fur in winter for camouflage and thick insulation against the cold. These adaptations developed over thousands of generations of natural selection.
Within any ecosystem, energy flows from producers (plants) to consumers (animals) to decomposers (bacteria and fungi). Matter cycles through the system — nutrients from a dead tree return to the soil and feed new plants. Healthy ecosystems cycle matter and energy efficiently and can recover from disturbances. Human activities like deforestation, pollution, and climate change threaten this balance.
| Biome | Climate | Key Plants | Example Animal |
|---|---|---|---|
| Tropical Rainforest | Hot and very rainy year-round | Tall trees, ferns, vines | Jaguar |
| Desert | Very little rainfall, hot or cold | Cactus, shrubs | Camel |
| Grassland | Moderate rain, flat terrain | Grasses, few trees | Bison |
| Temperate Forest | Four seasons, moderate rain | Oak, maple trees | White-tailed deer |
| Taiga | Cold, snowy winters | Spruce, pine, fir | Moose |
| Tundra | Extremely cold, frozen ground | Mosses, lichens | Arctic fox |
Key terms
- Ecosystem
- All the living and non-living things in an area and the interactions between them.
- Biome
- A large region with a characteristic climate, plant life, and animal life.
- Producer
- An organism that makes its own food through photosynthesis, like a plant or algae.
- Consumer
- An organism that gets energy by eating other organisms.
- Decomposer
- An organism that breaks down dead matter and returns nutrients to the soil, like fungi or bacteria.
- Abiotic
- Non-living factors in an ecosystem such as water, sunlight, soil, and temperature.
- Biotic
- Living factors in an ecosystem such as plants, animals, and microorganisms.
Flashcards
- Ecosystem
- All living and non-living things in an area and their interactions.
- Biome
- A large region with a specific climate and characteristic organisms.
- Trophic cascade
- A chain reaction when one species' change affects many others throughout an ecosystem.
- Abiotic factors
- Non-living parts of an ecosystem: water, sunlight, soil, air, temperature.
- Biotic factors
- Living parts of an ecosystem: plants, animals, fungi, bacteria.
- Decomposer
- Organism that breaks down dead matter and returns nutrients to the environment.
Practice questions
Which of the following is an abiotic factor in an ecosystem?
- A deer
- A pine tree
- Sunlight
- A mushroom
Show answer
Answer: Sunlight
Sunlight is non-living (abiotic). Deer, pine trees, and mushrooms are all living (biotic) factors.
Decomposers are consumers because they get energy from other organisms.
Show answer
Answer: False
Decomposers are not classified as consumers. They occupy their own category — they break down dead organic material rather than consuming living organisms.
Which biome has the LEAST amount of rainfall?
- Tropical rainforest
- Temperate forest
- Grassland
- Desert
Show answer
Answer: Desert
Deserts receive less than 10 inches of rain per year by definition, making them the driest biome.
A ___ is a large region of Earth defined by its climate and characteristic plants and animals.
Show answer
Answer: biome
A biome is defined by climate (temperature and precipitation patterns) and the organisms adapted to live in those conditions.
Removing a predator from an ecosystem can affect plants and even rivers.
Show answer
Answer: True
The Yellowstone wolf reintroduction is a famous example: wolves reduced deer overgrazing, restored vegetation, stabilized riverbanks, and changed river courses — a trophic cascade.
Fun facts
- The Amazon rainforest produces about 20% of Earth's oxygen and is home to 10% of all known species on the planet.
- A single teaspoon of healthy forest soil contains more microorganisms than there are people on Earth.
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