A scientist prepared four culture vessels containing the same starting population density of alga P. Alga Q was added to two of the vessels. Both algae require mineral ions from the culture solution. The vessels received equal light intensity and were kept at either 16∘C16^{\circ}\mathrm{C}16∘C or 26∘C26^{\circ}\mathrm{C}26∘C.
| Temperature in ∘C^{\circ}\mathrm{C}∘C | Mean population density of alga P without alga Q in millions of cells per cm3\mathrm{cm}^3cm3 | Mean population density of alga P with alga Q in millions of cells per cm3\mathrm{cm}^3cm3 |
|---|---|---|
| 16 | 1.4 | 1.2 |
| 26 | 3.8 | 2.4 |
Which statement is supported by the table?
At 16∘C16^{\circ}\mathrm{C}16∘C, adding alga Q reduces the mean population density of alga P by more than half.
The temperature increase produces a larger proportional rise in mean population density with alga Q than without alga Q.
The difference between the cultures with and without alga Q is larger at 26∘C26^{\circ}\mathrm{C}26∘C than at 16∘C16^{\circ}\mathrm{C}16∘C.
At 26∘C26^{\circ}\mathrm{C}26∘C with alga Q, the mean population density of alga P is twice that at 16∘C16^{\circ}\mathrm{C}16∘C without alga Q.
82 exam-style questions on Edexcel GCSE Biology 9.1 Ecosystems and interdependence, covering 9.1.1 Levels of organisation in ecosystems, 9.1.2 Abiotic and biotic factors, 9.1.3 Importance of interdependence, 9.1.4 Parasitism and mutualism, and 9.1.5 Determining number of organisms in an area. Each one has a worked solution and a mark scheme showing where the marks go.