Births, deaths, immigration and emigration

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Two lakes of ducks during one year (model data)

   lake	ducks at the start	births
   A	400	60
   B	100	20

2. 1.

   Bo reads the table. Which lake has the higher per-capita birth rate?

   • Lake A: 0.15 births per duck, against 0.20 for lake B
   • Lake B: 0.20 births per duck, against 0.15 for lake A
   • Lake A: it had more births, 60 against 20 for lake B
   • Lake A: it started with more ducks, 400 against 100

3. Turtles in one year with no moves in or out (model data)

   measure	value
   turtles at the start of the year	500
   births per turtle	0.20
   deaths per turtle	0.08

4. 2.

   Esme reads the model data for 500 turtles. No turtles move in or out. What is the change in the number of turtles in one year?

   • +140: (0.20 + 0.08) × 500, the two rates added
   • +0.12: 0.20 − 0.08, a rate and not a count
   • +60: (0.20 − 0.08) × 500
   • +100: 0.20 × 500, the births alone and no losses

5. Birds in one wood, starting with 120 birds (model data)

   year	births	deaths	immigrants	emigrants
   1	15	6	4	3
   2	12	9	2	8
   3	18	7	5	4

6. 3.

   Jun reads the table. Immigrants moved in; emigrants moved out. How many birds are in the wood at the end of year 3?

   • 143 birds: 120 plus births minus deaths, no moves
   • 132 birds: 120 plus the year 3 change alone
   • 165 birds: 120 plus the births of the 3 years
   • 139 birds: 120 + 10 − 3 + 12

7. Turtles on one island (model data)

   year	births	deaths	immigrants	emigrants
   1	30	20	6	4
   2	40	25	5	30
   3	15	22	20	3
   4	28	28	2	2

8. 4.

   Luz reads the table of turtles on one island. Immigrants moved in; emigrants moved out. In which year did the number of turtles fall?

   • Year 4: births and deaths are both 28, so it fell
   • Year 2: a fall of 10, as 30 moved out
   • Year 3: deaths, 22, are more than births, 15
   • Year 1: deaths, 20, and emigrants, 4, make 24 lost, so it fell

9. Two plots of seedlings after one night of frost (model data)

   plot	seedlings before	seedlings after	percent that survive
   sparse plot	50	30	60
   crowded plot	400	240	60

10. 5.

    Milo reads the model data after one night of frost. Which type of factor is the frost?

    • Density-dependent: the crowded plot had 160 fewer seedlings, the sparse plot 20 fewer
    • Neither type: a frost is not a factor that changes a population
    • Density-independent: the frost did not change the seedlings in either plot
    • Density-independent: both plots kept 60%, sparse or crowded

11. Plants per square meter and the percent that survive the year (model data)

    plants per square meter	percent that survive
    10	90
    40	70
    80	45

12. 6.

    Noah reads the model data. Which statement fits the table?

    • A density-dependent effect: a smaller share survives as crowding rises
    • A density-dependent effect: a larger share survives as crowding rises
    • A density-independent effect: the share that survives is the same in each plot
    • A density-independent effect: weather reached the three plots alike

13. Four factors that change a plant population (model data)

    factor	what happens
    flood	water covers a whole meadow
    competition for space	crowded plants share limited ground
    frost	one cold night reaches a whole meadow
    drought	a dry season reaches a whole meadow

14. 7.

    Pia reads the factor cards. Which choice sorts two of the factors correctly?

    • Drought: density-dependent. Competition for space: density-dependent, as both are crowded
    • Competition for space: density-independent. Frost: density-dependent, as crowds hold heat
    • Frost: density-dependent. Drought: density-independent, as the ground is crowded
    • Flood: density-independent. Competition for space: density-dependent

15. Mark and recapture on one lake (model data)

    step	ducks
    marked and released in the first catch	60
    caught in the second catch	90
    marked ducks in the second catch	15

16. 8.

    Ren reads the model data for one lake. What is the estimate of the number of ducks in the lake?

    • 135 ducks: 60 + 90 − 15, the counts added
    • 10 ducks: (60 × 15) ÷ 90, flipped
    • 150 ducks: 60 + 90, the two catches added
    • 360 ducks: (60 × 90) ÷ 15

17. Mark and recapture on one pond (model data)

    step	frogs
    marked and released in the first catch	45
    caught in the second catch	60
    marked frogs in the second catch	18

18. 9.

    Tala reads the model data for one pond. Estimate the number of frogs in the pond.

    • 87 frogs: 45 + 60 − 18, the counts added
    • 13.5 frogs: (45 × 18) ÷ 60, flipped
    • 150 frogs: (45 × 60) ÷ 18
    • 60 frogs: the number caught the second time

19. Two ways a second catch of 90 turtles can go, with 60 turtles marked (model data)

    marked turtles	marked turtles in the second catch	estimate
    mix freely	15	360
    avoid the traps	10	540

20. 10.

    Zee reads the table. Marked turtles learn to avoid the traps. How does that change the estimate?

    • It is too high: fewer marked turtles are recaptured, so 540 not 360
    • It stays the same: 60 turtles were marked and 90 were caught either way
    • It cannot be found: the estimate needs each marked turtle recaptured
    • It is too low: fewer marked turtles caught means a smaller population