Succession: how ecosystems rebuild after a change
Grade 9 Science Worksheet
Circle the best answer.
Read this first
Two sites after a change (model data)
site what happened soil at the start years until grasses cover half the ground lava site a lava flow covered the land none 40 fire site a fire cleared the forest soil and ash 4 Jun compares two sites. Which claim fits the table?
- The fire site was slower, because its soil was lost and had to form again
- The lava site was quicker, because bare rock leaves nothing in the way of the new plants as they spread
- The two sites took the same time, because both began with no plants on them
- The fire site is secondary succession, and it was quicker because its soil was still there
Years until grasses cover half the ground (model data)
site years lava rock (primary) 60 old field (secondary) 5 Bo compares two sites. How many more years did the primary site need to reach half cover?
- 55 years
- 12 years
- 5 years
- 65 years
Two sites at the start (model data)
site soil depth at the start (cm) first plants seen new lava rock 0 lichens and mosses abandoned field 12 annual plants Esme compares the sites. Which statement does the table support?
- The field began with soil, but the rock has to build its soil first
- Both sites need people to plant their first species before anything starts
- The rock began with no soil, so it will recover faster than the field
- The field began with soil, so it has to build soil first, like the rock
Kira reads the graph. Which plant type has the greatest cover at year 20?
- Trees, at 5 percent
- Annual plants, at 20 percent
- Grasses, at 50 percent
- Shrubs, at 50 percent
Luz reads the graph. In which year do shrubs first cover more ground than grasses?
Use the picture in question 4.
- Year 30
- Year 10
- Year 40
- Year 20
Milo reads the graph. Between which two years does the tree cover rise the most?
Use the picture in question 4.
- Year 30 to year 40, a rise of 20
- Year 40 to year 50, a rise of 30
- Year 50 to year 60, a rise of 20
- Year 20 to year 30, a rise of 15
An old field left alone (model data)
question answer years since farming stopped 8 ground cover now grasses cover most; a few shrubs; no trees soil deep Pia reads the card. What most likely comes next in this secondary succession?
- Shrubs spread, and small trees begin to join them
- Lichens and mosses begin to build soil on the bare ground
- Tall trees take over before the shrubs have spread
- Annual plants return as the main cover for good
Three sites after a change (model data)
site what happened soil afterward cooled lava flow lava covered the land none fire-cleared forest a fire cleared the trees soil and ash farm field left alone farming stopped soil Ren reads the table. Which two sites will show the same kind of succession?
- The fire-cleared forest and the farm field left alone
- The cooled lava flow and the farm field left alone
- The three sites share one kind of succession
- The cooled lava flow and the fire-cleared forest, since both were cleared
Tala reads the graph. A fire cleared the forest between year 80 and year 100. What starts after the drop?
- Primary succession, because the cleared forest lost its soil
- No change, because a climax community cannot change
- Secondary succession, because the soil stayed behind
- A new forest, once people plant the trees
Share of trees in a climax forest (model data)
survey oak (percent) hickory (percent) pine (percent) year 0 40 35 25 year 30 38 36 26 Zee compares two surveys of a climax forest. What do they show?
- The shares should not move in a climax forest, so the surveys must be wrong
- The same three trees lead, with small shifts, so the balance is dynamic
- The forest has no equilibrium, because the three shares are not equal
- Pine is rising, so the forest is leaving its climax stage and starting again