How an ecosystem rebuilds after a change

Grade 7 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   An oak and hickory forest has been growing back for about 150 years after a fire. What has it most likely become, Ari?

   • A pioneer stage
   • Bare rock
   • A climax community
   • A grassland of annual plants
2. 2.

   In a climax forest, the number of oak trees goes up and down a little each decade. What does that show, Bo?

   • Its balance is steady but still shifts
   • Succession has started over
   • The forest is turning into rock
   • The counts must be wrong
3. 3.

   A storm knocks down part of a climax forest, but the soil stays. What happens in that part next, Esme?

   • Lichens must cover it first
   • Secondary succession starts again
   • It stays a climax forest, unchanged
   • It stays bare for good
5. 4.

   From 40 to 80 years after the field was left alone, how did tree cover change, Jun?

   • Up 50 (20% to 70%)
   • Down 20 (40% to 20%)
   • Up 30 (20% to 50%)
   • Up 70 (0% to 70%)
6. 5.

   When does tree cover first become larger than grasses and shrubs added together, Luz?

   Use the picture in question 4.

   • Year 100
   • Year 80
   • Year 40
   • Year 60
7. 6.

   A new lava flow covers the edge of an old forest. What grows first on that new rock, Milo?

   • Oak and hickory trees
   • Lichens and mosses
   • Shrubs from the old forest
   • Grasses from the old soil
8. 7.

   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
   • More shrubs, then trees
   • Just the same grasses
   • Lichens and mosses on bare rock
9. 8.

   Ren says a lava flow gives secondary succession because it clears away plants. Agree or disagree?

   • Agree: any clearing gives secondary
   • Disagree: new lava has no soil, so it is primary
   • Disagree: plants can't grow on lava
   • Agree: lava adds soil right away
10. 9.

    Tala says primary succession is faster than secondary because it starts fresh. Agree or disagree?

    • Agree: lava already holds soil
    • Agree: bare rock is easier for plants
    • Disagree: both take one year
    • Disagree: it must build soil first, so it is slower
11. 10.

    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
    • Agree: its counts stay exactly the same
    • Disagree: a disturbance can start succession again