How an ecosystem rebuilds after a change
Grade 7 Science Worksheet - Challenge Me
Circle the best answer.
An oak and hickory forest has been growing back for about 150 years after a fire. What has it most likely become, Ari?
- A grassland of annual plants
- Bare rock
- A pioneer stage
- A climax community
In a climax forest, the number of oak trees goes up and down a little each decade. What does that show, Bo?
- The forest is turning into rock
- Its balance is steady but still shifts
- The counts must be wrong
- Succession has started over
From 40 to 80 years after the field was left alone, how did tree cover change, Jun?
- Down 20 (40% to 20%)
- Up 70 (0% to 70%)
- Up 30 (20% to 50%)
- Up 50 (20% to 70%)
When does tree cover first become larger than grasses and shrubs added together, Luz?
Use the picture in question 3.
- Year 60
- Year 100
- Year 40
- Year 80
A new lava flow covers the edge of an old forest. What grows first on that new rock, Milo?
- Lichens and mosses
- Shrubs from the old forest
- Grasses from the old soil
- 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?
- Fewer plants of each type
- Just the same grasses
- Lichens and mosses on bare rock
- More shrubs, then trees
On a lava island, scientists see lichens, mosses and ferns but no grasses yet. What does the land still need before grasses spread, Pia?
- More soil
- Tall trees for shade
- Fewer lichens and mosses
- A fire to clear the mosses
Ren says a lava flow gives secondary succession because it clears away plants. Agree or disagree?
- Disagree: plants can't grow on lava
- Disagree: new lava has no soil, so it is primary
- Agree: lava adds soil right away
- Agree: any clearing gives secondary
Tala says primary succession is faster than secondary because it starts fresh. Agree or disagree?
- Agree: lava already holds soil
- Disagree: both take one year
- Disagree: it must build soil first, so it is slower
- Agree: bare rock is easier for plants
Zee says a climax forest is finished and can't change again. Agree or disagree?
- Agree: once trees grow, succession is over
- Disagree: it turns back into rock each year
- Disagree: a disturbance can start succession again
- Agree: its counts stay exactly the same