How people affect biodiversity

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Fish stock counts at the end of 2023 (real data, NOAA Fisheries, 2023)

   group of stocks	number of stocks
   managed	506
   with a known overfishing status	364
   subject to overfishing, of the known ones	21

2. 1.

   Ari assumes the stocks with unknown status match the known ones. About how many of all 506 stocks would be subject to overfishing?

   • About 42, the 21 doubled for the unknown stocks
   • About 142, the number of stocks with an unknown status
   • About 21, because the known stocks count and the rest do not
   • About 29: 21 of 364 is 5.8%, and 5.8% of 506 is about 29

3. Record of one model site after a ban (model data)

   years after the ban	water looks	pesticide level (parts per billion)
   0	clear	16
   2	clear	8
   4	clear	4
   6	clear	2

4. 2.

   Esme reads the record. The safe level is 1 part per billion. When does the level reach it?

   • Year 2: the ban stopped the pollutant, so it is already gone
   • Year 15: it falls 1 each year from 16 until it reaches 1
   • Year 8: the level halves every 2 years, 16 → 8 → 4 → 2 → 1
   • Year 4: the water already looks clear, so it is safe

5. Use this

   States with a first zebra mussel record (each point counts the states whose first record was in that year or earlier) (real data, USGS Nonindigenous Aquatic Species). Year (calendar year) across, 1988 to 2028, a mark every 8. States (number of states) up, 0 to 40, a mark every 10. The line "States with a record" joins (1988, 3), (1996, 19), (2004, 22), (2012, 30), (2020, 31) with straight pieces.

6. 3.

   Jun reads the graph. Which statement about the spread of the mussels does it support?

   • Records fell after 1996, so the mussels left some states
   • The spread stayed steady at about 2 states a year
   • The first 8 years added 16 states, 2 a year; 2004 to 2020 added 9, about 0.6 a year
   • The mussels are native to each new state, so the records show where they already lived

7. A model fish stock under a rebuilding plan (model data)

   year	catch (thousand tonnes)	stock size (thousand tonnes)
   1	30	40
   6	10	28
   11	10	45
   16	12	70

8. 4.

   Kira reads the table. Between years 6 and 11, about how much did the stock grow each year before the catch was taken?

   • About 7 thousand tonnes: 17 minus the 10 caught
   • About 27 thousand tonnes a year: the 17 gained in total plus the 10 caught
   • About 3 thousand tonnes: the net gain each year
   • About 13 thousand tonnes: a net gain of 3.4 a year plus the 10 caught

9. One plant species on a mountain (model data)

   year	air temperature (°C)	lowest elevation of the plant (meters)	grazing on the lower slope
   1980	8.0	800	light
   2000	8.6	870	heavy
   2020	9.2	940	heavy

10. 5.

    Luz sees the plant's lowest elevation rise as the air warms. Which new evidence would best separate warming from grazing as the cause?

    • The air temperature at the top of the mountain
    • The plant's lowest elevation on ungrazed slopes over the same years
    • Warming explains the move, so no other driver could be acting on the mountain
    • The plant's count at the grazed sites, measured again

11. Notebook

    Notes on two model meadows (classmate's notebook), 4 lines. Columns: line, entry. Line 1: Meadow A had 20 plant species and now has 14. Line 2: Meadow B had 50 plant species and now has 40. Line 3: A lost 6 and B lost 10, so B was hit harder. Line 4: A share compares the loss with the starting number.

12. 6.

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

    • Line 3: A lost 6 ÷ 20 = 30% and B lost 10 ÷ 50 = 20%, so A was hit harder
    • Line 2: B lost 10, so the line should say B has 60 species
    • Line 4: a share should divide by the number now, not the starting number
    • Line 1: A lost 14 species, since 14 is the number it has now

13. Notebook

    Notes on two model fish stocks (classmate's notebook), 4 lines. Columns: line, entry. Line 1: Catch limits began on stock P in 2010. Line 2: Stock P rose from 28 to 70 thousand tonnes by 2020, a rise of 42. Line 3: Stock Q, with no limits, rose from 30 to 66 thousand tonnes. Line 4: So the catch limits caused the rise in stock P.

14. 7.

    Noah reads a classmate's notebook about catch limits. Which line has the mistake?

    • Line 3: a stock with no limits cannot be used for comparison
    • Line 2: 70 − 28 should be 98 thousand tonnes
    • Line 4: stock Q rose without limits too, so the limits are not shown to cause the rise
    • Line 1: limits cannot work if they begin before any data are taken, so line 1 is the flaw

15. Record of one model site after a ban (model data)

    years after the ban	water looks	pesticide level (parts per billion)
    0	clear	16
    2	clear	8
    4	clear	4

16. 8.

    Ren's friend says the ban fixed the stream by year 4. Which reply fits the record? The safe level is 1 part per billion.

    • Yes: the level fell 75%, from 16 to 4, so the stream is safe and the problem is solved
    • Yes: the level fell by 12, which is a big drop
    • Yes: the water looks clear, so the stream is clean
    • Not yet: at year 4 the level is 4, still four times the safe level of 1

17. Two ways to clear an invasive plant (model data)

    option	cost (thousand dollars)	native species recovered
    pulling by hand	50	8
    herbicide	20	5

18. 9.

    Tala compares two ways to clear an invasive plant. Which reply uses the table best?

    • Pulling wins, since it recovers the most species, 8
    • The costs per species are equal, since both are in thousands
    • Herbicide wins, since $20 thousand is less than $50 thousand, so it is the cheaper option overall here
    • Herbicide costs less per species, $4 thousand against $6.25 thousand; harm to others is not shown

19. Direct drivers of change in nature, ranked by global impact so far (real data, IPBES 2019)

    rank	driver
    1	changes in land and sea use
    2	direct exploitation of organisms
    3	climate change
    4	pollution
    5	invasive alien species

20. 10.

    Zee's friend says pollution does not matter, since it ranks fourth. Which reply fits the IPBES ranking?

    • Disagree: the ranking is global, so a driver ranked fourth can be the main one in one place
    • Agree: the top driver explains the loss, so the lower four can be ignored
    • Agree: a fourth-place driver has not harmed any species anywhere
    • Disagree: the ranking is wrong, because invasive species have spread faster than pollution has