How people affect biodiversity

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Fish stocks with a known status, end of 2023 (real data, NOAA Fisheries, 2023)

   list	stocks with a known status	stocks flagged
   overfishing	364	21
   overfished	263	47

2. 1.

   Ari reads the NOAA table. Which list flagged the larger share of the stocks with a known status?

   • Overfished: 47 stocks against 21, about 2 times as large, since the counts decide the answer
   • Both flag about the same share: 47 of 506 and 21 of 506
   • Overfished: 17.9% (47 of 263) against 5.8% (21 of 364), about 3 times as large
   • Overfishing: 21 of 364 is 5.8%, which is larger than 47 of 263

3. Species lost from one wetland, by driver (model data)

   driver	species lost where it acted
   habitat loss	14
   invasive species	9
   pollution	7
   total species lost	20

4. 2.

   Esme reads the wetland table. Why do the driver counts add to more than 20, and what is the best reading?

   • Some species had more than one driver, so the counts overlap and cannot be added
   • Habitat loss was the main cause: 14 of the 20 species lost is 70%, the largest share
   • The total should be 30, so 10 lost species were left out
   • The table has an error, because each species lost has a single cause

5. Plant species in two woodland patches (model data)

   patch	species before	species after
   control (kept whole)	50	47
   cleared in part	50	35

6. 3.

   Jun reads the table. How many percent points more of its species did the cleared patch lose than the control?

   • 37 points: 15 of 35 is 43%, minus 6%
   • 12 points: 15 lost minus 3 lost
   • 24 points: 30% of the cleared patch's species were lost, against 6% in the control
   • 30 points: the cleared patch's loss on its own, without taking away what the control lost

7. Pesticide level in one model stream after a ban (model data)

   year after the ban	level (parts per billion)
   0	24
   3	12
   6	6

8. 4.

   Kira reads the table. What is the level at year 9, and by what percent did it fall from year 0?

   • 3 parts per billion, a fall of 12.5%
   • 3 parts per billion, a fall of 87.5%, since it halves every 3 years
   • 0 parts per billion, since a ban removes the pesticide
   • 1.5 parts per billion, a fall of 93.75%

9. Two sites on one model stream (model data)

   site	water looks	nitrate (milligrams per liter)	limit (milligrams per liter)
   site 1 (upstream)	clear	4	10
   site 2 (downstream)	clear	10	10

10. 5.

    Luz reads the table. By what percent did nitrate rise downstream, and is it over the limit?

    • 0%, since the water looks clear at both sites
    • 60%, and the reading is over the limit
    • 150%, and the reading is over the limit since it is 6 higher
    • 150%, and the reading is at the limit, not over it

11. Three model rivers (model data)

    river	driver acting	plant species before	plant species after
    river 1	a dam	40	34
    river 2	a pesticide	40	36
    river 3	a dam and a pesticide	40	27

12. 6.

    Milo reads the table. Which statement does the evidence support?

    • Both drivers matter: rivers 1 and 2 lost 6 and 4, but the river with both lost 13
    • The dam is the one cause, since both rivers with a dam lost more species than river 2
    • The effects simply add, since 6 + 4 is close to 13
    • The pesticide has no effect, since river 2 lost just 4 of 40
13. 7.

    Noah reads the graph. Which statement describes stream A and predicts its level at year 8?

    • Stream A falls 3 every 2 years, so it reaches 0 at year 8
    • Stream B also falls, to about 12 parts per billion by year 8
    • Stream A halves every 2 years, so it should be about 1.5 parts per billion at year 8
    • Stream A reaches 0 by year 8, because the ban stopped the pollutant from entering the stream
14. 8.

    Pia reads the graph. Which statement does it support about the stock after year 10?

    • It rebuilt by about 4 thousand tonnes a year, rising back above the line by year 15
    • It stayed above the overfished line the whole twenty years
    • It was extinct at year 10, then a new stock took over
    • It rebuilt by about 40 thousand tonnes a year, the size of the line

15. Fish stock status at the end of 2023 (real data, NOAA Fisheries, 2023)

    row	count
    stocks or stock complexes managed	506
    stocks on the overfishing list	21
    stocks on the overfished list	47
    stocks rebuilt since 2000	50

16. 9.

    Ren reads the NOAA rows. Which statement about overfished stocks do they support?

    • Overfishing has ended, since just 21 of 506 stocks are on that list
    • Recovery is possible: 50 stocks were rebuilt since 2000, though 47 were still overfished
    • Most managed stocks are overfished, since 47 is more than 21
    • The 47 overfished stocks are gone for good, since stocks that small do not come back after that

17. Four plans for testing the farm's pesticide (model data)

    plan	what is done
    plan A	count insects and test the pesticide at sites above and below the farm, before and after spraying
    plan B	ask neighbors whether the water looks clean
    plan C	count insects once, at one site below the farm
    plan D	test the pesticide at one site after the insects have fallen

18. 10.

    Tala wants to test whether a farm's pesticide lowered a stream's insect count. Which plan gives the best evidence?

    • Plan A: it measures both, with sites above the farm as a comparison
    • Plan D: a pesticide reading after the loss shows what caused the loss
    • Plan B: how clear the water looks shows whether a pesticide is present
    • Plan C: a single count below the farm shows the pesticide's effect