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 two sites took the same time, because both began with no plants on them
- The lava site was quicker, because bare rock leaves nothing in the way of the new plants as they spread
- 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
- 65 years
- 5 years
- 12 years
Kira reads the graph. Which plant type has the greatest cover at year 20?
- Trees, at 5 percent
- Shrubs, at 50 percent
- Annual plants, at 20 percent
- Grasses, at 50 percent
Luz reads the graph. In which year do shrubs first cover more ground than grasses?
Use the picture in question 3.
- Year 40
- Year 20
- Year 30
- Year 10
Milo reads the graph. Between which two years does the tree cover rise the most?
Use the picture in question 3.
- Year 20 to year 30, a rise of 15
- Year 40 to year 50, a rise of 30
- Year 50 to year 60, a rise of 20
- Year 30 to year 40, a rise of 20
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 three sites share one kind of succession
- The fire-cleared forest and the farm field left alone
- The cooled lava flow and the fire-cleared forest, since both were cleared
- The cooled lava flow and the farm field left alone
Cover on a lava field at year 35 (model data)
plant type cover (percent) lichens and mosses 15 grasses 20 shrubs 45 trees 5 Noah reads the table. Which stage is this lava field in?
- The shrub stage, because shrubs cover the most and trees are just starting
- The pioneer stage, because lichens and mosses are still the main cover of the ground
- The tree stage, because any trees mean the trees have come first
- The grass stage, because grasses must lead before any shrubs appear
Tala reads the graph. A fire cleared the forest between year 80 and year 100. What starts after the drop?
- Secondary succession, because the soil stayed behind
- Primary succession, because the cleared forest lost its soil
- No change, because a climax community cannot change
- 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?
- Pine is rising, so the forest is leaving its climax stage and starting again
- The forest has no equilibrium, because the three shares are not equal
- The same three trees lead, with small shifts, so the balance is dynamic
- The shares should not move in a climax forest, so the surveys must be wrong
A lava field at year 30 (model data)
question answer first living things lichens and mosses soil a thin layer grasses now growing Ari reads the card. Why can grasses now replace the pioneers on this lava field?
- Grasses can grow straight on the bare rock, so the soil changed nothing for them
- Grasses need people to plant them once the pioneers have gone from the rock
- The pioneers stay the main plants, and the grasses grow on top of them
- The pioneers built soil where less hardy, more competitive grasses can grow
