People, resources and biodiversity: reading a model

Grade 9 Science Worksheet

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 turns the UN's 12 years and projected 15 years for each billion into people added per year. What is the result?

   • About 12 million a year, then about 15 million a year
   • About 0.83 million a year, then about 0.67 million
   • About 83 million a year, then about 100 million a year
   • About 83 million a year, then about 67 million a year
3. 2.

   From 7 to 8 billion, the UN adds about 83 million people a year to a base near 7.5 billion. What yearly percent growth does Bo get?

   • About 1.1% a year, found as 83 ÷ 7,500
   • About 11% a year, found as 83 ÷ 750
   • About 0.11% a year, found as 8.3 ÷ 7,500
   • About 8.3% a year, found as 83 ÷ 1,000
4. 3.

   Esme compares 8 billion in 2022 with the projected 10.3 billion peak. How many more people is that, as a share of 8 billion?

   • About 2.3 billion more, about 29% of 8 billion
   • About 2.3 billion more, about 2.9% of 8 billion
   • About 2.3 billion more, about 22% of 8 billion
   • About 18.3 billion more, about 229% of 8 billion

5. 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.

6. 4.

   Jun multiplies each FAO net-loss rate by its ten years and adds them. About how much net forest was lost from 1990 to 2020?

   • About 5.9 million ha, the average yearly rate
   • About 47 million ha, the last decade alone
   • About 177 million ha, close to FAO's 178 million
   • About 17.7 million ha, found by adding the three rates
7. 5.

   Suppose net loss stays at 4.7 million ha a year for 30 more years. What share of 2020's 4.06 billion ha would Kira say is lost?

   • About 12%, found as 141 million ÷ 1,170 million
   • About 35%, found as 141 million ÷ 406 million
   • About 3.5%, found as 141 million ÷ 4,060 million
   • About 0.12%, which is one year's loss alone
8. 6.

   For 1990–2000, deforestation 16 minus net loss 7.8 gives gains of 8.2. Luz uses 8.2 to guess 2015–2020 net loss as 10 minus 8.2, or 1.8. Why is that shaky?

   • It is fine, because forest gains are fixed at 8.2 million ha
   • Gains in 1990–2000 may differ from gains in 2015–2020
   • Net loss is deforestation plus gains, so the sum is wrong
   • FAO has no net loss figures for the years after 2010

9. 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.

10. 7.

    The model stock is 800 and Pia holds the catch at 80 a year. At 800 the stock adds 0.4 × 800 × 0.2 = 64. What happens?

    • It falls toward 720: it adds 64 and loses 80
    • It falls to zero, since 64 is less than 80
    • It rises, since a catch of 80 is below the largest
    • It holds at 800, since a catch of 80 is under 100

11. 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

12. 8.

    NOAA has 42 stocks on the overfished list out of 522 managed. Ren wants the share of all stocks that are overfished.

    • About 4.4%, found as 23 ÷ 522 from the other list
    • About 12.5%, found by adding both lists, 65 ÷ 522
    • About 8.0%, found as 42 ÷ 522
    • About 80%, found as 42 ÷ 52.2
13. 9.

    NOAA rebuilt 51 stocks from 2000 to 2024. At that yearly pace, about how long would Tala need to rebuild the 42 overfished stocks?

    • About 89 years, found as 42 × 2.1
    • About 24 years, the time since the year 2000
    • About 0.05 years, found as 2.1 ÷ 42
    • About 20 years, found as 42 ÷ about 2.1 a year
14. 10.

    Zee finds 23 of 522 stocks (4.4%) and 23 of 372 stocks (6.2%). Which share describes stocks whose status is known?

    • 6.2%, because 372 stocks are already rebuilt
    • 6.2%: the other 150 stocks have no known status
    • Either one, since 23 is the same number in both shares
    • 4.4%, because 522 includes the unknown stocks too