People, resources and biodiversity: reading a model
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Read this first
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.
Bo's friend says deforestation fell from 16 to 10 million ha a year, so forests are now growing. Which reply fits FAO?
- Yes: net loss fell, so it is now below zero
- No: deforestation fell, but net loss rose over those years
- No: net loss was still 4.7 million ha a year in 2010–2020
- Yes: when deforestation falls, forest area must grow
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.
A classmate says the model proves real fish stocks collapse once catches pass 100 thousand tons. Esme replies. Which reply is best?
- Models are tested on real fish each time, so the claim holds
- NOAA's own table lists 100 as the catch limit for any real stock
- The model uses chosen numbers; real stocks need real assessments
- Catches above 100 help a stock grow back, so the claim must fail
In the model, Jun holds the catch at 100 instead of 80 for 10 years. How much more is caught, and how much lower does the stock finally settle?
- 200 thousand tons more caught; the settled stock is 20 lower
- 200 thousand tons more caught; the settled stock is 220 lower
- 2,000 thousand tons more caught; the settled stock is 2,200 lower
- 20 thousand tons more caught; the settled stock is 220 lower
Going from a catch of 80 to 100, the model's settled stock drops from 720 to 500. What percent drop does Kira find?
- About 44%, found as 220 ÷ 500
- About 4%, found as 20 ÷ 500
- About 22%, found as 220 ÷ 1,000
- About 31%, found as 220 ÷ 720
A manager sets the model's catch at 100 while the stock is only 250. At 250 the stock adds 0.4 × 250 × 0.75. What does Luz predict?
- It falls, since it adds 75 and loses 100 a year
- It falls until the stock reaches 500, then holds steady
- It holds steady, since 100 is the model's largest steady catch
- It rises, since a low stock grows at its fastest pace
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.
Milo wants evidence that world population growth is slowing. Which pair of UN facts is best, with its limit?
- 8 billion in 2022 and 10.2 billion in 2100, which are both measured
- 7 to 8 billion took 12 years; 8 to 9 billion is projected at 15
- The projected 10.3 billion peak is higher than the 8 billion in 2022
- 7 to 8 billion took 12 years, the fastest billion ever counted
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 Noah wants the best evidence that U.S. fishery management can work. Which NOAA fact fits, with its limit?
- 42 stocks are overfished, so no stock has been rebuilt
- 522 stocks are managed, so the whole list must be healthy
- 23 stocks are on the overfishing list, so management has failed
- 51 stocks were rebuilt since 2000, though 42 are still overfished
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.
Pia wants to test whether the model fits a real fish stock. Which evidence would help most?
- More model tables for many other catch levels and growth rates
- A much longer model run that keeps the same growth rate and cap
- Survey counts and catches of a real stock, against the model
- NOAA's count of stocks on the overfished list this year
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.
Ren writes one summary of world population from the UN table. Which one fits best?
- 8 billion counted in 2022; growth speeds up, with a peak near 10.3 billion
- 8 billion counted in 2022; projected to slow and peak near 10.3 billion
- 10.3 billion counted in 2022, falling to 8 billion by 2037
- 8 billion projected for 2037, with a counted peak near 20 billion
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.
Zee writes one summary of the fishery model. Which one fits best?
- Any catch settles at a steady stock level; these are NOAA records
- Larger catches leave a larger stock at the end; this is measured data
- A catch of 120 settles the stock at about 500; this is model output
- Catches up to 100 settle; larger ones drain the stock; model output
