Births, deaths, immigration and emigration

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Noah reads the graph of one plot. What is the density of seedlings at year 4?

   • 5 seedlings per square meter: 100 ÷ 20
   • 3.5 seedlings per square meter: 70 ÷ 20, the count at year 3
   • 0.2 seedlings per square meter: 20 ÷ 100
   • 100 seedlings per square meter: the count at year 4

2. Read this first

   Bees on one hillside during one year (model data)

   count	bees
   at the start of the year	250
   births	40
   deaths	15
   immigrants (moved in)	10
   emigrants (moved out)	5

3. 2.

   Bo reads the table. What is the change in the number of bees, and the change for each bee at the start?

   • +25 bees, or 0.10 per bee: 25 ÷ 250
   • +30 bees, or 30 per bee: the count as a rate
   • +30 bees, or 0.12 per bee: 30 ÷ 250
   • +50 bees, or 0.20 per bee: 50 ÷ 250

4. One field of plants over two years (model data)

   measure	year 1	year 2
   plants	200	400
   area (square meters)	40	100

5. 3.

   Esme reads the table. What happened to the density of plants from year 1 to year 2?

   • It fell, from 5 to 4 plants per square meter, as the area grew faster
   • It stayed at 5 plants per square meter, as both numbers grew
   • It doubled, from 200 to 400 plants, because the count of plants doubled in a year
   • It rose, from 5 to 10 plants per square meter: 400 ÷ 40

6. Two plots of seedlings in a normal year and a drought year (model data)

   plot	percent that survive in a normal year	percent that survive in a drought year
   sparse plot, 10 seedlings per square meter	90	63
   crowded plot, 50 seedlings per square meter	60	42

7. 4.

   Jun reads the table of two plots of seedlings. Which statement fits the data?

   • The drought cut a larger share from the sparse plot, since it fell 27 points against 18
   • The drought cut a larger share from the crowded plot, since it ended lower, at 42%
   • Crowding lowers survival in both years; the drought cut each plot by the same 30%
   • Crowding does not matter: both plots were cut by the same drought

8. Plots of 10 square meters at four densities (model data)

   plants per square meter	plants	births per plant	total births
   5	50	0.8	40
   10	100	0.6	60
   20	200	0.4	80
   40	400	0.2	80

9. 5.

   Kira reads the table of plots, each 10 square meters. Which statement fits the data?

   • Total births rose from 40 to 80, so births per plant rose with density too
   • Births per plant fall as density rises, so total births must fall too
   • Births per plant fall because of a flood, a density-independent factor
   • Births per plant fall as density rises, even though total births rose from 40 to 80

10. Mark and recapture on a lake of 50 hectares (model data)

    step	ducks
    marked and released in the first catch	40
    caught in the second catch	50
    marked ducks in the second catch	8

11. 6.

    Luz reads the model data for one lake. What are the estimated number of ducks and the density?

    • 250 ducks, and 0.2 ducks per hectare: 50 ÷ 250
    • 6.4 ducks, and 0.13 ducks per hectare: flipped
    • 250 ducks, and 5 ducks per hectare: 250 ÷ 50
    • 250 ducks, and 250 ducks per hectare: the count as density

12. Notebook

    Notes on two plots of seedlings (classmate's notebook), 4 lines. Columns: line, entry. Line 1: Plot X holds 120 seedlings on 40 square meters, which is 3 per square meter. Line 2: Plot Y holds 90 seedlings on 15 square meters, which is 6 per square meter. Line 3: Plot X has the higher density, since 120 is more than 90. Line 4: So plot Y has twice the density of plot X.

13. 7.

    Milo reads a classmate's notebook about two plots. Which line has the mistake?

    • Line 3: density is count ÷ area, so plot Y at 6 is higher than plot X at 3
    • Line 1: 120 ÷ 40 is 0.3 seedlings per square meter, not 3 seedlings
    • Line 2: 90 ÷ 15 is 60 seedlings per square meter, not 6 seedlings
    • Line 4: 6 is three times 3, so plot Y has three times the density

14. Notebook

    Notes on a drought and two plots (classmate's notebook), 4 lines. Columns: line, entry. Line 1: After a drought, 56 of 80 seedlings in the sparse plot survived, which is 70%. Line 2: In the crowded plot, 210 of 300 seedlings survived, which is 70%. Line 3: More seedlings did not survive in the crowded plot, 90 against 24, so drought is density-dependent. Line 4: In both plots the drought left the same share, 70%.

15. 8.

    Pia reads a classmate's notebook about a drought. Which line has the mistake?

    • Line 1: 56 of 80 seedlings is 7%, not 70%
    • Line 3: both plots kept 70%, so the drought is density-independent
    • Line 4: the same share cannot survive in plots of different density
    • Line 2: 210 of 300 seedlings is 21%, not 70%

16. Two ponds of frogs during one year (model data)

    pond	frogs at the start	births
    A	500	50
    B	80	16

17. 9.

    Ren reads the table. Which claim goes with the right reason?

    • Claim: pond A has the higher rate per frog. Reason: it had more births, 50 against 16
    • Claim: the ponds have the same rate. Reason: each pond had births in the year
    • Claim: pond B has the higher rate per frog. Reason: it has fewer frogs, 80 against 500
    • Claim: pond B has the higher rate per frog. Reason: 16 ÷ 80 is 0.20, against 0.10
18. 10.

    Tala reads the graph. Which claim goes with the right reason?

    • Claim: the population has stopped changing. Reason: the line flattens near 190
    • Claim: the population is shrinking. Reason: the yearly gains get smaller, from 30 to 6
    • Claim: growth is speeding up. Reason: the line keeps climbing from 100 to 190
    • Claim: the population is still growing. Reason: each yearly change is above 0, but smaller, 30 to 6