Water pollution

6 (a) Using the recommended amount of fertiliser on a crop increases crop yield. Some farmers think that adding extra fertiliser will give an even greater crop yield.

Give a reason why adding extra fertiliser does not result in an even greater crop yield.

Some farmers apply more nitrogen fertiliser and more water to their fields than are needed. Explain the biological consequences of applying more nitrogen fertiliser and more water than needed.

The atmosphere can be polluted by gases such as carbon monoxide released from industry. Describe the effects of carbon monoxide on the human body.

Which of these is not a greenhouse gas?

The diagram shows the nitrogen cycle with some processes labelled.

Explain why plants need nitrate ions.

Name the processes V, X and Y.

Scientists measure the dissolved nitrate levels in a river that passes through farmland. They also measure the nitrogen compounds being used on the farmland either as fertiliser or as manure from livestock. The graph shows how the nitrate levels in the river and the nitrogen compounds applied to the farmland changed from 1950 to 2005.

(Source: Graph: Trends in Nitrate Levels in Maumee River | U.S. Geological Survey (usgs.gov))

Comment on the relationship between nitrate levels in the river and the nitrogen compounds applied to the farmland.

Describe the changes within the river that would have occurred between 1950 and 2000.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow. When the Oceans Glow In some areas of the world the oceans around the coast sometimes glow with a blue light. The photograph shows an area of coast that is glowing. This blue light is produced by the presence of thousands of microscopic, living organisms called dinoflagellates. These dinoflagellates are protoctists. The production of light by living organisms is called bioluminescence, a process that has evolved many times in different species of organism.

(Source: © AMIRREZA KAMKAR/SCIENCE PHOTO LIBRARY) To generate light, dinoflagellates use special proteins and the ATP produced within their cells. Many species of dinoflagellate contain chlorophyll and are able to photosynthesize. The appearance of glowing dinoflagellates in the sea used to be a rare event but this now occurs much more frequently. Many of the events occur in the sea around river estuaries and scientists think that intensive farming and deforestation could be to blame. Due to overpopulation of dinoflagellates in these areas, other species of animal are often harmed. After a series of glowing events, large numbers of dinoflagellates die causing oxygen levels in the water to decrease. People have often wondered why dinoflagellates glow. They only glow in areas where the water moves around, such as when waves hit a beach. Scientists now think that the production of light is a type of warning to stop predators eating the dinoflagellates. If an animal eats dinoflagellates, the dinoflagellates in the area glow making the animal obvious to its own predators. To test this, scientists placed dinoflagellates into a tank along with 15 copepods, which are predators of dinoflagellates. When the dinoflagellates glowed, the copepods ate 1200 dinoflagellates in two hours. When the dinoflagellates did not glow, the copepods ate 2100 dinoflagellates in two hours. Some scientists think that we could make use of the dinoflagellates to provide sustainable street lighting. Tanks of dinoflagellates could be placed on top of lamp posts. The dinoflagellates would photosynthesise during the day when it is light. A stirrer powered by a small battery would then move them at night so that they would glow. These sustainable lamps could be carbon neutral and help to reduce pollution.

Which of these processes produces ATP? (line 6)

Explain why intensive farming and deforestation would cause an increase in populations of dinoflagellates. (lines 9 to 11)

Explain why oxygen levels decrease after a series of glowing events. (lines 10 to 13)

Which type of bacteria converts ammonia into nitrates?

Each of the 15 copepods ate glowing dinoflagellates at a mean rate of 40 dinoflagellates per hour. Calculate the mean rate at which each copepod ate dinoflagellates that were not glowing. (lines 18 to 21)

mean rate =_........ dinoflagellates per hour

Explain how natural selection could have resulted in the evolution of dinoflagellates that glow. (lines 15 to 18)

Explain why using dinoflagellates for street lighting would help to reduce pollution. (lines 22 to 26)

The diagram shows the nitrogen cycle. Some of the stages have been labelled.

Which stage shows nitrogen fixation?

Which stage shows nitrification?

Which stage shows denitrification?

Farmers sometimes add chemical fertiliser to the soil.

Describe how pollution by fertiliser can affect aquatic ecosystems.

Give an alternative to chemical fertiliser that a farmer could use.

The table gives some examples of biological processes.

Complete the table by giving the name of each process.

The first one has been done for you.

Zinc is poisonous to many plants and can affect natural selection.

A scientist investigates the ability of one grass species to survive at different distances from a zinc mine.

The scientist uses a sampling method to measure the percentage cover of this grass species at different distances from the zinc mine.

The graph shows the scientist’s results.

The zinc concentration in soil is higher near the zinc mine than it is further from the zinc mine.

Explain how natural selection could be responsible for the results shown in the graph between 0 and 100 metres.

Describe a method the scientist could use to compare the population size of the grass species at 50 metres and 100 metres from the mine.

Farmers may add chemical fertilisers to their soil.

Explain how chemical fertilisers can increase crop yield.

These fertilisers may leak into rivers. A scientist measures the oxygen content of water in two different locations of the same river during the month of April.

In location A he finds that the mean dissolved oxygen was 6 mg per litre and at location B he finds that the mean dissolved oxygen was 3 mg per litre. He concludes that the use of fertiliser in the field has affected the oxygen content of the river. Discuss his conclusion.

Some farmers use alternative substances to chemical fertilisers. Suggest one alternative substance that a farmer may use.

Farmers can increase their crop yield by growing crops in a temperature controlled glasshouse.

Explain how increasing the temperature can result in an increase in crop yield.

Farmers sometimes use a type of heater that burns gas or oil to raise the temperature of their glasshouse to improve crop yield.

Explain why they use this type of heater to improve crop yield.

Some farmers also add chemical fertilisers to their crops in a glasshouse.

Different minerals are added to chemical fertilisers. Explain one mineral that should be added to these fertilisers.

Discuss why some farmers limit the amount of chemical fertilisers they add to their crops.

Pollution can occur in the atmosphere and in rivers.

Carbon monoxide can pollute the atmosphere. Describe the effects of carbon monoxide pollution on humans.

Water pollution can occur if sewage enters a river. Explain the biological consequences of sewage pollution on a river ecosystem.