In a coastal marine ecosystem, the primary producers are giant kelp forests.
Sunlight that can potentially be used in photosynthesis by autotrophs is called photosynthetically active radiation (PAR).
In one year, 8.41×108 kJ m−28.41 \times 10^8 \text{ kJ m}^{-2}8.41×108 kJ m−2 of PAR fell on an area of this kelp forest. The giant kelp converted 4.93×106 kJ m−24.93 \times 10^6 \text{ kJ m}^{-2}4.93×106 kJ m−2 of this energy into biomass.
Calculate the energy in the PAR that the giant kelp did not convert into biomass. Give your answer in standard form to three significant figures.
A marine mammal, the sea otter, is a keystone predator in this ecosystem. The current breeding population of sea otters in a marine reserve is estimated at 147 individuals. This represents 42%42\%42% of the estimated population thirty years ago.
Calculate the estimated breeding population of sea otters in the reserve thirty years ago, rounded to the nearest whole number.
37 exam-style questions on OCR A A Level Biology Ecosystems. Each one has a worked solution and a mark scheme showing where the marks go.