People, resources and biodiversity: reading a model

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Table, World population (UN), with columns Milestone, UN figure

   8 billion reached, November 15, 2022; Time from 7 to 8 billion, about 12 years; Time from 8 to 9 billion (projected), about 15 years, to about 2037; Peak (projected), about 10.3 billion, mid-2080s; 2100 (projected), about 10.2 billion.

2. 1.

   Ari compares the UN's 12 years from 7 to 8 billion with the projected 15 years from 8 to 9 billion. What does it show?

   • The total will start to fall, because 15 years is longer than 12 years
   • Total still rises, but people added yearly fall from 83 to 67 million
   • Yearly growth speeds up, because 9 billion is more than 8 billion
   • Yearly growth stays the same, at about 1 billion per 12 years
3. 2.

   Bo reads the UN table for a report. Which claim does it support best?

   • The UN projects a peak near 10.3 billion, then a slight fall
   • Population reached 10.3 billion in 2022 and has fallen since
   • Population keeps rising after the 2080s, with no peak in sight
   • The UN counted 10.3 billion people alive in the mid-2080s

4. Table, Forests (FAO, 2020 assessment), with columns Measure, FAO figure

   Forest area, 2020, 4.06 billion hectares (31% of land); Deforestation, 1990–2000, 16 million ha a year; Deforestation, 2015–2020, 10 million ha a year; Net forest loss, 1990–2000, 7.8 million ha a year; Net forest loss, 2000–2010, 5.2 million ha a year; Net forest loss, 2010–2020, 4.7 million ha a year; Net forest loss since 1990, 178 million ha.

5. 3.

   FAO says net forest loss fell from 7.8 to 4.7 million ha a year. What does Jun conclude about total forest area?

   • Forest area grew, because net loss went down
   • Forest area still shrank each decade, only more slowly
   • Forest area shrank faster in each later decade
   • Forest area has held the same since the year 2000
6. 4.

   In 1990–2000, FAO has deforestation at 16 million ha a year and net loss at 7.8. How much forest was gained each year, by Kira's subtraction?

   • About 8.2 million ha a year gained back
   • About 7.8 million ha a year, the net loss itself
   • About 0.5 million ha a year, found by dividing
   • About 23.8 million ha a year, found by adding them
7. 5.

   FAO says 4.06 billion ha of forest is 31% of land. What total land area does Luz get?

   • About 5.9 billion ha, found as 4.06 ÷ 0.69
   • About 13.1 billion ha, found as 4.06 ÷ 0.31
   • About 5.3 billion ha, found as 4.06 plus 31%
   • About 1.26 billion ha, found as 4.06 × 0.31

8. Use the table

   U.S. fish stocks, end of 2024 (NOAA Fisheries)

   Measure	Number of stocks
   Stocks managed	522
   With a known overfishing status	372
   On the overfishing list	23
   On the overfished list	42
   Rebuilt since 2000	51

9. 6.

   NOAA lists 23 stocks on the overfishing list and 42 on the overfished list. Milo says they are the same stocks. Reply?

   • Yes: fishing too hard puts a stock on both lists at once
   • No: overfished stocks are the ones already rebuilt by NOAA
   • Yes: both lists are smaller than the 51 rebuilt stocks
   • Not necessarily: one is a catch rate, the other a low population
10. 7.

    NOAA: 372 stocks have a known overfishing status, and 23 of them are subject to overfishing. What share is that for Noah?

    • About 16%, found as 372 ÷ 23
    • About 4%, found as 23 ÷ 522
    • About 62%, found as 23 ÷ 37.2
    • About 6%, found as 23 ÷ 372
11. 8.

    Pia studies a stock caught faster than the rate that gives maximum sustainable yield, though its population is still high. Which fits?

    • Both overfished and subject to overfishing
    • On the overfishing list, but not overfished
    • Overfished, but not subject to overfishing
    • Neither one, because its population is still high

12. Fishery computer model output (model data)

    Steady catch (thousand tons a year)	Stock the model settles at (thousand tons)
    40	about 890
    80	about 720
    100	about 500
    120	falls toward 0

    Note: The model starts at 1,000 thousand tons, the most the habitat holds. Each year the stock adds 0.4 × stock × (1 − stock ÷ 1,000) thousand tons.

13. 9.

    Ren raises the model's steady catch from 40 to 100 thousand tons a year. How much less fish settles in the water?

    • About 500 thousand tons less, the stock left at 100
    • About 60 thousand tons less, found as 100 minus 40
    • About 390 thousand tons less, from 890 down to 500
    • About 170 thousand tons less, from 890 down to 720
14. 10.

    In the model, Tala sets the catch at 120 thousand tons a year, above the table's largest steady catch. What happens to the stock?

    • It falls toward zero, since the stock cannot replace 120 a year
    • It rises, because a bigger catch needs a bigger stock
    • It settles near 1,000, the most the habitat holds
    • It settles at about 500, just like a catch of 100 would