How an ecosystem rebuilds after a change
Grade 7 Science Worksheet - Challenge Me
Circle the best answer.
In a climax forest, the number of oak trees goes up and down a little each decade. What does that show, Bo?
- Succession has started over
- The forest is turning into rock
- The counts must be wrong
- Its balance is steady but still shifts
A storm knocks down part of a climax forest, but the soil stays. What happens in that part next, Esme?
- It stays a climax forest, unchanged
- Secondary succession starts again
- Lichens must cover it first
- It stays bare for good
In which 20-year span did tree cover rise the most, Kira?
- From year 40 to year 60
- From year 20 to year 40
- From year 80 to year 100
- From year 0 to year 20
When does tree cover first become larger than grasses and shrubs added together, Luz?
Use the picture in question 3.
- Year 80
- Year 100
- Year 60
- Year 40
A new lava flow covers the edge of an old forest. What grows first on that new rock, Milo?
- Grasses from the old soil
- Lichens and mosses
- Shrubs from the old forest
- Oak and hickory trees
A field left alone 10 years ago now has grasses and young shrubs. What will most likely spread over the next 50 years, Noah?
- More shrubs, then trees
- Fewer plants of each type
- Just the same grasses
- Lichens and mosses on bare rock
On a lava island, scientists see lichens, mosses and ferns but no grasses yet. What does the land still need before grasses spread, Pia?
- Fewer lichens and mosses
- More soil
- Tall trees for shade
- A fire to clear the mosses
Ren says a lava flow gives secondary succession because it clears away plants. Agree or disagree?
- Agree: lava adds soil right away
- Agree: any clearing gives secondary
- Disagree: new lava has no soil, so it is primary
- Disagree: plants can't grow on lava
Tala says primary succession is faster than secondary because it starts fresh. Agree or disagree?
- Disagree: both take one year
- Agree: bare rock is easier for plants
- Agree: lava already holds soil
- Disagree: it must build soil first, so it is slower
Zee says a climax forest is finished and can't change again. Agree or disagree?
- Agree: once trees grow, succession is over
- Agree: its counts stay exactly the same
- Disagree: a disturbance can start succession again
- Disagree: it turns back into rock each year