Answer on paper first, then reveal the mark scheme one mark at a time.
Water is recycled through the water cycle.
Name the process described in each statement.
(a) Water from the sea is heated by the Sun and turns into water vapour. [1]
(b) Water vapour cools in the air and forms clouds. [1]
(c) Water falls from clouds as rain. [1]
The carbon cycle returns carbon from organisms to the atmosphere.
(a) Explain how the carbon in dead leaves on a forest floor is returned to the atmosphere. [3]
(b) Name the process by which plants remove carbon dioxide from the atmosphere. [1]
(c) Large areas of tropical forest are being cut down and burned. Explain how this increases the concentration of carbon dioxide in the atmosphere. [2]
The diagram shows part of the carbon cycle.
The letters P, Q, R, S, T and U show processes that move carbon.
(a) Name the process shown by arrow P. [1]
(b) Name the process shown by arrow T. [1]
(c) Arrows R and U show the same process. Name this process. [1]
(d) Which arrow, Q or S, shows a process carried out by microorganisms such as bacteria and fungi? [1]
The water cycle provides fresh water for plants and animals that live on land.
(a) Sea water contains dissolved salts, but rain water does not. Explain why. [2]
(b) Plants return water from the soil to the atmosphere. Name the process by which water vapour is lost from the leaves of plants. [1]
(c) In a dry country, a large area of forest is cut down. Suggest two ways this could affect the water cycle in that area. [2]
Carbon atoms are cycled between living organisms and the atmosphere.
Describe how a carbon atom in a molecule of carbon dioxide in the air could become part of a protein in the muscle of a sheep, and then be returned to the air. [4]
| Level | Marks | What it looks like |
|---|---|---|
| Level 2 | 3–4 | A clear, linked sequence covering both halves of the journey: carbon taken in by photosynthesis and built into plant molecules, passed to the sheep by feeding and used to make muscle protein, and then returned to the air by respiration of decomposers (or of the sheep). |
| Level 1 | 1–2 | Relevant processes named, e.g. photosynthesis, eating, decay or respiration, but the sequence is incomplete or the links between steps are not made. |
| No marks | 0 | No relevant content. |
A gardener makes compost from grass cuttings and vegetable peelings.
(a) Name one type of microorganism that decays the waste in the compost heap. [1]
(b) Every week the gardener turns the compost heap over with a fork to mix air into it. Explain why this makes the waste decay faster. [2]
(c) Give one other condition that would make the waste decay faster. [1]
(d) The gardener adds the finished compost to the soil. Give one reason why this helps plants to grow. [1]
A student investigated the effect of temperature on the decay of fresh milk.
She put 100 cm³ of fresh milk into each of three flasks. She kept the flasks at 4 °C, 20 °C and 30 °C. She measured the pH of the milk in each flask with a pH probe at the start and again after 48 hours.
| Temperature in °C | pH at start | pH after 48 hours |
|---|---|---|
| 4 | 6.7 | 6.5 |
| 20 | 6.7 | 5.1 |
| 30 | 6.7 | 4.3 |
(a) Give the independent variable in this investigation. [1]
(b) Give one variable the student should control. [1]
(c) Calculate the mean rate of change of pH at 30 °C.
Give your answer in pH units per hour. [2]
(d) Explain why the pH of the milk decreases as it decays. [2]
(e) Suggest why the pH changed very little at 4 °C. [1]
Scientists put 20.0 g of dried leaves into each of several fine mesh bags. They buried the bags in the soil at two sites:
Every 4 weeks they dug up one bag from each site, dried the leaves again and found their dry mass. The graph shows the results.
(a) Calculate the mean rate of decay of the leaves at Site A during the first 8 weeks.
Give your answer in g per week. [2]
(b) Calculate the percentage of the original mass of leaves that was lost at Site B by week 20. [2]
(c) Explain why the leaves decayed more slowly at Site B. [2]
(d) The rate of decay at Site A becomes slower as time goes on. Suggest one reason why. [1]
A farm uses a biogas generator. Animal manure and plant waste are put into a sealed tank where microorganisms decay them.
(a) Name the gas in biogas that is burned as a fuel. [1]
(b) Explain why the tank must be sealed so that no air can get in. [2]
(c) The generator produces 18 m³ of biogas each day. 65% of the biogas is the fuel gas.
Calculate the volume of fuel gas produced in one week. [2]
(d) Suggest why the generator produces less biogas in winter. [1]
(e) The waste left in the tank after decay is spread on the farm's fields. Give one reason why. [1]
Scientists recorded how far north a species of butterfly was found in Britain. They also recorded the mean summer temperature in Britain.
| Year | Mean summer temperature in °C | Furthest distance north of the south coast where the butterfly was found in km |
|---|---|---|
| 1975 | 14.6 | 310 |
| 1985 | 14.5 | 330 |
| 1995 | 15.0 | 390 |
| 2005 | 15.3 | 450 |
| 2015 | 15.4 | 480 |
Further information:
Evaluate the evidence that the change in distribution of the butterfly was caused by a rise in temperature.
Use information from the table and your own knowledge. [6]
| Level | Marks | What it looks like |
|---|---|---|
| Level 3 | 5–6 | Evidence both for and against a temperature cause is discussed, using data from the table and the extra information (alternative explanations such as food supply or recording effort), with a reasoned judgement that follows from the evidence. |
| Level 2 | 3–4 | Evidence for and against is given, with some use of data, but the discussion is one-sided in depth or the conclusion is missing or not supported. |
| Level 1 | 1–2 | Simple statements, e.g. the butterfly moved north as it got warmer, or a single alternative factor named, with little use of the data. |
| No marks | 0 | No relevant content. |
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