Grade 7 · Science · Unit 3 of 12
Cycles & Succession
Matter cycles; land regrows
What your child practises
How water, carbon and nitrogen are cycled through ecosystems, why cycling supports sustainability, and the difference between primary and secondary succession.
Ontario Curriculum expectation: B2.5, B2.6 · cycling of matter; primary and secondary succession
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
A wildfire burns a forest. The next spring, fireweed is already growing. Why so soon?
- Succession cannot happen after a fire
- Fireweed seeds fall from clouds
- Roots, seeds and soil survived the fire
- The fire created new soil from rock
Show answer
Roots, seeds and soil survived the fire
Hint: This is secondary succession, which starts with soil and seeds already in place.
Question 2
Water vapour cools and turns into tiny droplets in clouds. This is called…
- precipitation
- condensation
- evaporation
- runoff
Show answer
condensation
Hint: A gas turning into a liquid is condensation.
Question 3
Which statement about succession is true?
- It never happens after fires
- It happens only in water
- It always ends in a desert
- Communities change over time in a fairly predictable pattern
Show answer
Communities change over time in a fairly predictable pattern
Hint: Simple, fast-growing species come first and are later replaced by larger, longer-lived ones.
Question 4
A farmer plants a different crop in a field each year. How can this keep the soil healthy?
- It removes all decomposers
- Different crops use and return different nutrients
- It stops the water cycle
- It adds new matter to Earth
Show answer
Different crops use and return different nutrients
Hint: Crop rotation helps keep nutrients in balance.
Question 5
Why do pioneer species usually come first?
- Animals plant them on purpose
- They can survive harsh conditions with little soil and few nutrients
- They need rich soil
- They are the largest plants
Show answer
They can survive harsh conditions with little soil and few nutrients
Hint: Tough, small species are able to start where others cannot.
Question 6
Which process puts carbon dioxide into the air?
- condensation
- photosynthesis
- evaporation
- respiration by living things
Show answer
respiration by living things
Hint: Plants and animals release carbon dioxide when they use food for energy. Burning fuels does too.