Births, deaths, immigration and emigration

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   One frog pond during one year (model data)

   measure	frogs
   frogs at the start of the year	200
   births in the year	30
   deaths in the year	10

2. 1.

   Ari reads the model data for one frog pond. What is the per-capita birth rate for the year?

   • 0.05 births per frog: 10 ÷ 200, the deaths row
   • 30 births per frog: the total number of births
   • 6.67 births per frog: 200 ÷ 30
   • 0.15 births per frog: 30 ÷ 200

3. Two lakes of ducks during one year (model data)

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

4. 2.

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

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

5. 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

6. 3.

   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?

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

7. 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

8. 4.

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

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

9. 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

10. 5.

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

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

11. 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

12. 6.

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

13. 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

14. 7.

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

    • 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-dependent: the crowded plot had 160 fewer seedlings, the sparse plot 20 fewer
    • Density-independent: both plots kept 60%, sparse or crowded

15. 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

16. 8.

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

    • A density-independent effect: weather reached the three plots alike
    • 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

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. 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

20. 10.

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

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