20. Human influences on ecosystems
A section of Biology, 0610
Listing 10 of 393 questions
The Mulanje cedar, Widdringtonia whytei, is the national tree of Malawi. This species of tree grows naturally only on Mount Mulanje in Malawi. Many of the trees have been overharvested or destroyed by wildfires, resulting in deforestation, as shown in . State the genus name of the Mulanje cedar tree. Explain the undesirable effects of deforestation on habitats that are on mountains, such as Mount Mulanje. Scientists in Malawi are working to prevent the extinction of the Mulanje cedar tree in its natural habitat. Explain the benefits to other organisms on Mount Mulanje of conserving the Mulanje cedar tree in its natural habitat. The seeds of many endangered tree species are kept in seed banks. Suggest why it is important to collect seeds from many individual trees of each species rather than just one tree.
0610_s22_qp_41
THEORY
2022
Paper 4, Variant 1
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shows a boreal toad, Anaxyrus boreas. This toad is listed as an endangered species. State the genus of the boreal toad. One reason for the boreal toad’s recent decrease in population is a disease caused by chytrid fungus. State two reasons other than disease that could cause the boreal toad to become endangered. Scientists investigated whether increasing the number of beneficial bacteria that live on the toads’ skin could provide protection against the fungus. The scientists took 42 toads and placed 21 in group 1 and 21 in group 2. • Group 1 – the toads’ skin was treated with beneficial bacteria. • Group 2 – the toads’ skin was not treated with beneficial bacteria. The scientists measured the number of toads that became infected with the fungus. Table 6.1 shows the results. Table 6.1 time since treatment with beneficial bacteria / days number of toads with fungal infection group 1 group 2 Calculate the percentage of the 21 toads that have the fungal infection after 100 days in group 1 in Table 6.1. Give your answer to two significant figures. Space for working. % Using the information in Table 6.1, describe the effect of treating the toads with beneficial bacteria. There are conservation programmes to reintroduce boreal toads into their natural habitat. Describe why conservation programmes are set up for animals like the boreal toad. Conservation programmes for other endangered animals, such as birds, use artificial insemination as part of a captive breeding programme. Describe how artificial insemination is carried out as part of a captive breeding programme.
0610_s24_qp_43
THEORY
2024
Paper 4, Variant 3
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Wetlands are internationally important ecosystems. The spoon-billed sandpiper, Calidris pygmaea, is an endangered species. shows a spoon-billed sandpiper feeding in a wetland ecosystem. The wetland is a stopover on the bird’s long migration from north-east Russia to south-east Asia. The smaller photograph is a close-up of the bird’s legs to show that it has been ringed. Spoon-billed sandpipers stop to feed at the Rudong mudflats near Shanghai, China. Putting one or more rings on a bird’s leg is a common way to identify individual birds. Spoon-billed sandpipers ringed in Russia have been seen at the Rudong mudflats. Suggest why scientists put leg rings on birds, such as the spoon-billed sandpiper. Explain why it is important to conserve ecosystems, such as wetlands.
0610_w16_qp_42
THEORY
2016
Paper 4, Variant 2
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The Canadian Government were concerned about overfishing at the Grand Banks in the Atlantic Ocean. As a result, commercial fish stocks were monitored from 2002 until 2013. The population data for four species of fish are shown in . number of fish / million 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 year number of fish / million species L 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 number of fish / million year species K species M 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 year species N 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 number of fish / million year Use the information in to: state the most abundant fish species in 2002 suggest the fish species that had the most carefully controlled fishing quotas between 2002 and 2013. Give a reason for your choice. calculate the percentage increase in species N between 2002 and 2003. Show your working. Overfishing is a possible reason for the decrease of the population of species M between 2002 and 2003. State two other reasons that could have caused this decrease. Overfishing can be reduced by having large holes in fishing nets. shows sections of two fishing nets, the drawings are both at the same scale. fishing net with large holes fishing net with small holes Suggest how controlling the size of the holes in fishing nets helps to reduce overfishing. Describe and explain how methods other than fishing net hole size, could help to prevent overfishing. shows part of a food web at the Grand Banks. guillemot gull seal cod zooplankton phytoplankton squid Cod is a species of fish that almost became extinct in the Grand Banks due to overfishing. Suggest how the extinction of cod could affect the food web in . Sustainable development is required to manage fish stocks. Define the term sustainable development.
0610_w17_qp_43
THEORY
2017
Paper 4, Variant 3
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Questions Discovered
393