20. Human influences on ecosystems
A section of Biology, 0610
Listing 10 of 393 questions
Very small pieces of plastic, called microplastics, are found in many products such as soaps and toothpaste. shows toothpaste that contains microplastics. It is estimated that microplastics make up 5% of the mass of some toothpastes. Each person uses approximately 2 g of toothpaste a day. There were estimated to be 1.2 × 109 people using toothpaste that contained microplastics in some countries in 2013. Calculate the mass of microplastics contained in the toothpaste used on one day in 2013 for these countries. Show your working and state appropriate units with your answer. State one recommendation, other than regular brushing, for the proper care of teeth. Lugworms live in sand on coastal beaches and are eaten by wading birds. Lugworms feed on diatoms. Diatoms are photosynthetic protoctists that require ammonium ions as a source of nitrogen. Beach sand contains ammonium ions. Construct a food chain for these marine organisms. There is some evidence that microplastics affect ammonium ions. Affected ammonium ions cannot be used by diatoms. A group of researchers thought that this could affect lugworms living in sand polluted by microplastics. The researchers collected 30 healthy lugworms, all with the same initial mass. They divided them into three groups, A, B and C. Each group contained 10 lugworms. Each group of lugworms was placed in a bucket containing the same mass of beach sand and ammonium ions and: A biodegradable microplastics B non-biodegradable microplastics C no microplastics. The measurements that were recorded at the end of the investigation are shown in Table 3.1. Table 3.1 variable measured group A B C ammonium ion concentration in the bucket / µmol per dm3 19.3 47.0 27.4 average respiration rate of lugworms / mg oxygen per hour per g mass 5.2 9.6 5.1 volume of lugworm faeces / cm3 60.0 25.0 40.0 average lugworm mass / g 9.1 7.0 9.1 Describe and explain why the researchers concluded that non-biodegradable microplastics are the most harmful to lugworms. Use the information in Table 3.1 in your answer. Ammonium ions are an important part of the nitrogen cycle. They can be converted into nitrate ions, which are used by plants and protoctists such as diatoms. State the name of the molecules that are converted into ammonium ions in the nitrogen cycle. State the name of the process of converting ammonium ions into nitrate ions. Explain the effects of nitrate ion deficiency on plant growth. Non-biodegradable plastics are also harmful to terrestrial ecosystems. Discuss the effects of non-biodegradable plastics on terrestrial ecosystems.
0610_s19_qp_42
THEORY
2019
Paper 4, Variant 2
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shows some of the processes involved in the treatment of sewage. settlement trickle filters OR activated sludge sludge treatment methane screening raw sewage treated water Complete Table 4.1 by placing ticks (3) in the correct boxes to show what is involved in each process during the treatment of sewage. The first row has been completed for you. Table 4.1 process process involves: aeration removal of large solids separating liquid waste from solid waste the use of microorganisms production of methane screening settlement sludge treatment trickle filters OR activated sludge Describe two reasons why it is necessary to treat sewage before returning the water to the environment.
0610_s20_qp_32
THEORY
2020
Paper 3, Variant 2
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Sewage treatment reduces water pollution. State the names of two of the stages of sewage treatment. Raw sewage is a major source of water pollution. State the name of one other source of water pollution. Urea is found in sewage. Urea is made in the human body and excreted in urine. State the name of the biological molecules that are broken down to make urea. State the name of the organ that produces urea. Raw sewage can be produced by intensive livestock farming. State two other negative impacts of intensive livestock farming.
0610_s22_qp_33
THEORY
2022
Paper 3, Variant 3
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Questions Discovered
393