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 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 peaked at 40 percent in year 20, then fell as grasses and soil rose
- They fell after year 20 because the soil became shallower
- They stayed the main cover through year 50, even while the soil deepened and grasses rose
Esme reads the table. At year 40, how much more do grasses cover than lichens and mosses, and how deep is the soil?
- 40 percentage points more, with 9 cm of soil
- 20 percentage points more, with 9 cm of soil
- 40 percentage points more, with 6 cm of soil
- 80 percentage points more, with 9 cm of soil
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 field had lost its soil, so pioneers broke up its rock first, which sped things up
- 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
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
- A second fire cleared the shrubs, even though the graph shows no fire
- The shrubs ran out of room, so they stopped spreading
- Taller trees shade the ground, so low plants such as shrubs get less light
Luz sees the lichen and moss line fall after year 20. What does this fit?
- Lichens and mosses are the permanent main cover here, so the line should keep rising
- A climax community has formed and stays the same, so the fall must be a mistake in the data
- Grasses are replacing the pioneers as soil forms, which fits primary succession
- 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 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
- Line 4: pioneers are lichens and mosses, and trees come after the soil forms
- Line 1: cooled lava keeps soil under it, so the rock already holds soil
Notebook
Notes on a forest after a fire (classmate's notebook), 4 lines. Columns: line, entry. Line 1: A fire cleared the forest, and ash returned nutrients to the ground. Line 2: The soil stayed, so this is secondary succession. Line 3: Lichens must first break the rock into soil before anything else grows. Line 4: Annual plants and grasses return first, then shrubs and small trees.
Noah reads a classmate's notebook about a forest after a fire. Which line has the mistake?
- Line 2: the soil was cleared away too, so this is primary succession
- Line 1: ash holds no nutrients, so the ground gets nothing from the fire
- Line 4: grasses come after trees, so the order of the plants is reversed
- Line 3: the soil is already there, so no pioneers need to make it first
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 4: the field was sooner, so secondary succession was the faster kind
- Line 3: the gap is 45 years, because 40 + 5 = 45
- Line 1: bare rock holds 0 cm of soil, so the lava site cannot be a real site
- Line 2: 12 cm of soil would slow the field down, so year 5 is too early
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 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
- Claim: the pioneers help later plants. Reason: plot 1 has 1 cm of soil and 8 grass seedlings
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: 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
- Claim: bare lava needs people to plant each stage. Reason: the table shows a new group of living things at each time
- Claim: bare lava can grow shrubs unplanted. Reason: pioneers came first and soil formed, then grasses and shrubs