Fig. 1 shows an island forest where native fruit-eating birds disperse seeds from a tree. Goats were introduced for farming and now eat young plants. Conser...
Question 1 Report
Fig. 1 shows an island forest where native fruit-eating birds disperse seeds from a tree. Goats were introduced for farming and now eat young plants. Conservation workers counted tree seedlings in fenced and unfenced squares of equal area. The table shows the mean number of seedlings after one year. Each square had similar soil, light and water conditions.
| Square type | Mean tree seedlings per m2 | Mean goat droppings per m2 |
|---|---|---|
| Fenced | 18 | 0 |
| Unfenced | 3 | 11 |
(a) Describe the effect of fencing on the number of tree seedlings. [1]
(b) Give one variable that was controlled in this investigation. [1]
(c) Explain how goats can reduce the population of native birds over several years. [2]
The figure shows a coastal village that uses wind turbines and diesel generators to supply electricity. Engineers recorded the percentage of electricity generated by each source over four months. The village also measures carbon dioxide released from fuel use. Wind energy does not require diesel to be burned.
| Month | Electricity from wind / % | Diesel used / dm3 | Carbon dioxide released / tonnes |
|---|---|---|---|
| January | 64 | 920 | 2.5 |
| February | 52 | 1210 | 3.3 |
| March | 71 | 690 | 1.9 |
| April | 43 | 1510 | 4.1 |
(a) Which month had the greatest percentage of electricity from wind? [1]
(b) Describe the relationship between wind electricity and diesel use. [1]
(c) Explain why replacing diesel with wind energy can reduce global warming. [2]
Answer Details
Labelled answer diagram:
Island seedlings
- (a) Fencing increases the number of tree seedlings: fenced squares had 18 seedlings per \(\text{m}^2\), compared with 3 in unfenced squares. [1]
- (b) One controlled variable was soil conditions. Other acceptable controls include square area, light intensity, water availability, or the time left for growth. Controlling these means fencing is the main difference being tested. [1]
- (c) Goats eat seedlings, so fewer seedlings survive to become mature trees. Over several years, birds have less fruit for food, and possibly fewer nesting sites; this reduces bird survival and reproduction. [2]
Wind and diesel electricity
- (a) March had the greatest wind-generated electricity, at 71%. [1]
- (b) Higher wind electricity is associated with lower diesel use. For example, March has the highest wind percentage and the lowest diesel use, whereas April has the lowest wind percentage and the highest diesel use. [1]
- (c) Replacing diesel means less fossil fuel is burned. Therefore less carbon dioxide is released, reducing the enhanced greenhouse effect and hence global warming. [2]
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