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

3. Evidence in lake Y (model data)

   driver	evidence
   zebra mussels	90 per square meter
   shoreline cleared	30 percent
   pesticide	4 parts per billion
   native mussels before	20 per square meter
   native mussels after	8 per square meter

4. 2.

   Bo reads the lake Y table. By what percent did native mussels fall, and what do the rows support?

   • 150%, and zebra mussels alone explain the fall as the largest number
   • 60%, and the zebra mussels are the one cause, at 90 per square meter
   • 60%, and three drivers have evidence, so the fall may have several causes
   • 40%, the share that fell, and the cause is mixed

5. 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

6. 3.

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

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

7. 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.

8. 4.

   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 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
   • The spread stayed steady at about 2 states a year

9. 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

10. 5.

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

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

11. 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

12. 6.

    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

13. 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.

14. 7.

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

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

15. 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.

16. 8.

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

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

17. Notebook

    Notes on one model stream (classmate's notebook), 4 lines. Columns: line, entry. Line 1: One test at one site in autumn found 2 parts per billion of a pesticide. Line 2: The limit is 5 parts per billion. Line 3: The farm sprays only in spring. Line 4: So the stream never goes over the limit.

18. 9.

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

    • Line 3: clear autumn water shows the spring level was the same
    • Line 4: one autumn sample from one site cannot show the spring level
    • Line 2: a limit cannot protect the stream, so line 4 does not matter
    • Line 1: the pesticide would be visible in the water, so the 2 must be wrong

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