Grade 7 · Science · Unit 3 of 14
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.
Alberta Curriculum learning outcome: Unit A: Interactions and Ecosystems · cycles of matter and how ecosystems change over time
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.