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

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?

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

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
   • 165 birds: 120 plus the births of the 3 years
   • 139 birds: 120 + 10 − 3 + 12
   • 132 birds: 120 plus the year 3 change alone

7. Snails in one marsh for one year (model data)

   count	snails
   at the start of the year	200
   births	30
   deaths	12
   immigrants (moved in)	5
   emigrants (moved out)	?
   at the end of the year	205

8. 4.

   Kira reads the table of snails in one marsh for a year. How many emigrants moved out?

   • 18 snails: 200 + 30 + 5 − 12 − 205
   • 23 snails: 30 + 5 − 12, the gain of the year
   • 5 snails: 205 − 200, the net change
   • 13 snails: 200 + 30 − 12 − 205, no arrivals

9. 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

10. 5.

    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 1: deaths, 20, and emigrants, 4, make 24 lost, so it fell
    • 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

11. 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

12. 6.

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

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

13. 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

14. 7.

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

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

15. 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

16. 8.

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

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

17. 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

18. 9.

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

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

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