Energy in Ecosystems — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. The carbon cycle moves carbon between air, plants, animals, and soil in Grade 5 ecosystems.
Carbon moves through photosynthesis, respiration, and decomposition in the carbon cycle.
2. Evaporation, condensation, and precipitation are all parts of the water cycle.
The water cycle moves H2O between oceans, air, and land, supporting all Grade 5 ecosystems.
3. Bacteria in soil change air nitrogen into a form plants can use.
Nitrogen-fixing bacteria turn N2 gas into nitrates, an important part of the Grade 5 nitrogen cycle.
4. When animals breathe out, they release carbon dioxide into the air.
Respiration returns CO2 to the atmosphere, closing one loop in the carbon cycle.
5. The total mass of living things in an ecosystem is called biomass.
Biomass is a Grade 5 vocabulary word for the energy and matter stored in living organisms.
6. Energy flows in one direction through ecosystems, from sun to producers to consumers.
Energy flows one way and is lost as heat, while matter cycles between living and non-living parts.
7. Decomposers like fungi return nutrients to the soil so new plants can grow.
Decomposers recycle matter back into the soil, feeding producers in Grade 5 ecosystems.
8. Water returns to clouds when it changes from liquid to gas through evaporation.
Evaporation is a key step that links the water cycle to energy from the sun in Grade 5 science.
9. The variety of life forms in an ecosystem is called biodiversity.
Biodiversity is a Grade 5 vocabulary word for the number and variety of species in an ecosystem.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Carbon cycle
→ CO2 moves between air, plants, and animals
CO2 moves between air, plants, and animals
Water cycle
→ Evaporation, condensation, and precipitation
Evaporation, condensation, and precipitation
Nitrogen cycle
→ Bacteria turn N2 gas into nitrates for plants
Bacteria turn N2 gas into nitrates for plants
Energy flow
→ One-way path from sun to producers to consumers
One-way path from sun to producers to consumers
Each matter cycle has a unique pathway, while energy flows in one direction without cycling back.