Succession: how ecosystems rebuild after a change
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Read this first
Plant cover and soil depth on a lava field (model data)
year lichens and mosses (percent) grasses (percent) soil depth (cm) 0 0 0 0 10 30 0 1 20 40 10 3 30 30 40 6 40 20 60 9 50 10 50 12 Ari reads the table. In the first year grasses cover over 30 percent, how deep is the soil?
- 9 cm
- 40 cm
- 3 cm
- 6 cm
Bo reads the table. Which claim about the lichens and mosses does the table support?
- They were replaced in year 30 because people planted grasses
- They fell after year 20 because the soil became shallower
- They peaked at 40 percent in year 20, then fell as grasses and soil rose
- They stayed the main cover through year 50, even while the soil deepened and grasses rose
Two sites of the same size (model data)
site soil at the start (cm) years until the first shrubs lava rock 0 30 old field left alone 15 6 Jun reads the table. Which explanation best fits why shrubs came sooner on the old field?
- People planted shrubs on the field, and the lava rock was left unplanted
- The bare rock let shrubs spread fastest, so the table must hold a mistake
- The field began with soil, while the rock had to build soil first
- The field had lost its soil, so pioneers broke up its rock first, which sped things up
Kira reads the graph. What best explains why shrub cover fell after year 40?
- The fire destroyed the soil, so the shrubs lost the ground they had grown in before
- Taller trees shade the ground, so low plants such as shrubs get less light
- The shrubs ran out of room, so they stopped spreading
- A second fire cleared the shrubs, even though the graph shows no fire
Luz sees the lichen and moss line fall after year 20. What does this fit?
- Grasses are replacing the pioneers as soil forms, which fits primary succession
- A climax community has formed and stays the same, so the fall must be a mistake in the data
- Lichens and mosses are the permanent main cover here, so the line should keep rising
- A fire cleared the lichens and mosses, so secondary succession has begun
Notebook
Notes on a new lava field (classmate's notebook), 4 lines. Columns: line, entry. Line 1: A lava flow covered the land and cooled into bare rock. Line 2: Lichens and mosses are pioneers, so they can start on the rock. Line 3: Over time they help make soil, and grasses and shrubs can follow. Line 4: Trees are first on bare rock, so they are the pioneer stage.
Milo reads a classmate's notebook about a lava field. Which line has the mistake?
- Line 1: cooled lava keeps soil under it, so the rock already holds soil
- Line 4: pioneers are lichens and mosses, and trees come after the soil forms
- Line 2: lichens and mosses need deep soil first, so they cannot be the pioneers here
- Line 3: pioneers add nothing to the rock, so people must bring the soil
Notebook
Notes on two sites of the same size (classmate's notebook), 4 lines. Columns: line, entry. Line 1: Lava site: 0 cm of soil, and grasses covered half the ground at year 40. Line 2: Old field: 12 cm of soil, and grasses covered half the ground at year 5. Line 3: The field was 35 years sooner, because 40 − 5 = 35. Line 4: So primary succession is the faster kind.
Pia reads a classmate's notebook about two sites. Which line has the mistake?
- Line 3: the gap is 45 years, because 40 + 5 = 45
- Line 4: the field was sooner, so secondary succession was the faster kind
- Line 2: 12 cm of soil would slow the field down, so year 5 is too early
- Line 1: bare rock holds 0 cm of soil, so the lava site cannot be a real site
Two lava plots of the same age (model data)
plot lichens and mosses present soil depth after 10 years (cm) grass seedlings plot 1 yes 1 8 plot 2 no 0 0 Ren reads the table. Which claim goes with the right reason?
- Claim: the pioneers help later plants. Reason: plot 1 has 1 cm of soil and 8 grass seedlings
- Claim: the pioneers stay the main plants for good. Reason: plot 1 has soil because they remain on it
- Claim: grass appears when people plant it. Reason: plot 1 was planted, and plot 2 was not
- Claim: the pioneers block later plants. Reason: plot 1 has more living things in the way of the grass
Tala reads the graph. Which claim goes with the right reason?
- Claim: the forest is still a climax community. Reason: both lines stay perfectly flat at 80 and 20 percent from survey to survey
- Claim: the forest is no longer a climax community. Reason: its cover changes from survey to survey
- Claim: the forest has returned to the pioneer stage. Reason: the shrub line is below the tree line at each survey
- Claim: the forest is still a climax community. Reason: both lines move a little but stay near 80 and 20 percent
Bare lava rock over 40 years (model data)
year living things seen soil 0 none none 10 lichens and mosses thin 25 grasses deeper 40 shrubs deeper still Zee reads the table. Which claim goes with the right reason?
- Claim: bare lava can grow shrubs unplanted. Reason: pioneers came first and soil formed, then grasses and shrubs
- Claim: bare lava needs people to plant each stage. Reason: the table shows a new group of living things at each time
- Claim: trees were the first living things on the lava. Reason: trees are the biggest plants, so they start the succession
- Claim: this is secondary succession. Reason: the lava cleared away the plants that were there before