A model community has 1000 species. Half of them are lost in 100 years, at a steady yearly rate…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A model community has species. Half of them are lost in years, at a steady yearly rate. (This model is not in the NEET syllabus, but A-Level and IB use rate models.)
- What per cent of the species is lost each year, to two decimals?
- How many species are left after years?
- After how many years has a quarter of the species been lost? Give one decimal.
Need a reminder? The key ideaShow
Five mass extinctions have happened, and a sixth is in progress at a rate 100 to 1000 times faster than before humans. In the last 500 years, 784 species have gone extinct: 338 vertebrates, 359 invertebrates and 87 plants. If a share of the species is left after years, the share kept each year is (not in the NEET syllabus).
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. species. A fraction is left after years.
Plan. The share kept each year is .
Step 1. (a) The share lost each year is , which is per cent.
Step 2. (b) species.
Step 3. (c) , so . So years.
Answer: per cent; species; years.
Check. It takes less than half of years to lose a quarter, because the loss is a share of what is left.
Discussion (0)
Log in to join the discussion.
Loading…