Births, deaths, immigration and emigration
Grade 9 Science Worksheet - Building Confidence
Circle the best answer.
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Frogs in one pond in one year (model data)
count frogs births 14 deaths 6 immigrants (moved in) 3 emigrants (moved out) 2 Ari reads the model data for frogs in one pond. What is the change in the number of frogs?
- +9: (14 + 3) − (6 + 2)
- +15: (14 + 6) − (3 + 2), deaths put with the gains
- +17: 14 births + 3 immigrants, with no losses counted
- +8: 14 births − 6 deaths, with no moves counted
Turtles on one pond island in one year (model data)
count turtles births 8 deaths 5 immigrants (moved in) 2 emigrants (moved out) 7 Bo reads the model data for turtles on one pond island. What is the change in the number of turtles?
- +3: 8 births − 5 deaths, with no moves counted
- +10: 8 births + 2 immigrants, with no losses counted
- +2: (5 + 7) − (8 + 2), the losses minus the gains
- −2: (8 + 2) − (5 + 7)
Ducks on one lake in one year (model data)
count ducks births 12 deaths 9 immigrants (moved in) 4 emigrants (moved out) ? change in the number of ducks 0 Esme reads the table. The number of ducks did not change. How many emigrants moved out?
- 5: 9 deaths − 4 immigrants, one loss and one gain mixed
- 3: 12 births − 9 deaths, with the arrivals left out
- 7: the losses must match the 16 gained, and 16 − 9 = 7
- 16: 12 births + 4 immigrants, the gains and not the moves out
Birds in one wood (model data)
year births deaths immigrants emigrants 2022 16 10 4 4 2023 24 14 3 5 2024 18 6 7 2 2025 20 6 0 12 Jun reads the table of birds in one wood. Immigrants moved in; emigrants moved out. In which year did the number of birds grow the most?
- 2025: the biggest births minus deaths, 14
- 2022: the first row of the table, with 16 births
- 2023: the most births, 24, in any year
- 2024: a gain of 17 birds
Snails in one marsh during 2024 (model data)
count snails at the start of 2024 80 births 30 deaths 12 immigrants (moved in) 5 emigrants (moved out) 9 Kira reads the table of snails in one marsh. How many snails are in the marsh at the start of 2025?
- 110 snails: 80 + the 30 births, with no losses counted
- 98 snails: 80 + 30 − 12, with no moves counted
- 14 snails: the change alone, read as the new size
- 94 snails: 80 + 14
Bees on one hillside (model data)
year births deaths immigrants emigrants 2021 30 18 2 8 2022 22 20 6 8 2023 26 26 4 9 2024 14 9 1 3 Luz reads the table of bees on one hillside. Immigrants moved in; emigrants moved out. In which year did the number of bees stay the same?
- 2024: the fewest births, 14, so the count held steady
- 2021: the most births, 30, so the count held steady
- 2023: births and deaths are both 26, so nothing changed
- 2022: the gains and the losses are both 28
Milo reads the graph. How many seedlings are in the plot at year 4?
- 65 seedlings: the height of the line above year 3
- 4 seedlings: the year, read as the count
- 90 seedlings: the height of the line above year 5
- 80 seedlings: the height of the line above year 4
Pia reads the graph. What is the change in the number of frogs from year 2 to year 5?
- +70 frogs: the count at year 5
- +40 frogs: 70 − 30
- +3 frogs: year 5 − year 2
- +30 frogs: the count at year 2
One seedling plot (model data)
measure value seedlings in the plot 120 area of the plot (square meters) 20 Ren reads the model data for one plot. What is the density of seedlings?
- 0.17 seedlings per square meter: 20 ÷ 120
- 120 seedlings per square meter: the count itself
- 100 seedlings per square meter: 120 − 20
- 6 seedlings per square meter: 120 ÷ 20
Two strips of pond edge (model data)
strip snails area (square meters) X 48 12 Y 48 6 Zee reads the table. Both strips hold 48 snails. Which strip has the higher density?
- Strip X: it has the larger area, 12 against 6 for strip Y
- Strip Y: 8 snails per square meter, against 4 for strip X
- The same: both strips hold 48 snails, so the density is equal
- Strip X: 4 snails per square meter, against 8 for strip Y