19.2. Food chains and food webs
A subsection of Biology, 0610, through 19. Organisms and their environment
Listing 10 of 345 questions
For Examiner's Use In the Arctic, snowy owls are predators of lemmings. The lemmings eat arctic plants. Draw the food chain for this arctic ecosystem. shows changes in the populations of snowy owls and lemmings over a three year period. year 1 year 2 year 3 hundreds of lemmings per km2 number of owls per km2 lemmings snowy owls During the first 10 months of year 1 the lemming population increases slowly at first and then more rapidly. Suggest why the rate of increase becomes greater. Using information in , suggest why the lemming population falls during year 2. For Examiner's Use Using information in , describe and explain how changes in the lemming population affect the snowy owl population. If all the snowy owls were removed from the arctic ecosystem, suggest and explain what effect this would have on the lemming population in the following years. Lemmings and snowy owls get their energy from the food they eat. What is the original source of all the energy in this ecosystem? Name the process that first traps this energy. [Total 12]
0610_s10_qp_22
THEORY
2010
Paper 2, Variant 2
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For Examiner's Use The passage describes the feeding relationships between some of the organisms in an African grassland ecosystem. The dominant grass species in the African grassland ecosystem are star grass and red oat grass. Star grass is eaten by antelope species, such as topi and Thomson’s gazelle. Smaller animals such as mice and grasshoppers also feed on grass. Antelopes are eaten by predators such as cheetahs, lions and serval cats. Grasshoppers and mice are eaten by serval cats and tawny eagles. Ruppell’s vulture feeds on dead mammals. shows part of the food web for this ecosystem. star grass red oat grass topi Thomson’s gazelle grasshoppers lions serval cats tawny eagles Complete the food web in by writing the names of the organisms in the boxes. Write your answers in the boxes in . Name the trophic level of the following species: star grass topi State the source of energy for the food web shown in . State what happens to energy when it leaves an ecosystem, such as the African grassland. For Examiner's Use Nutrients are recycled in ecosystems but energy is not recycled. Explain why there are no more than four trophic levels in the ecosystem shown in . Fish, such as salmon reared in fish farms, are fed on high protein food made from animals. When eating this food, these fish are feeding as secondary consumers. Discuss the disadvantages of farming fish, such as salmon, for human food.
0610_s11_qp_32
THEORY
2011
Paper 3, Variant 2
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For Examiner's Use The passage describes the feeding relationships between some of the organisms in an African grassland ecosystem. The dominant grass species in the African grassland ecosystem are star grass and red oat grass. Star grass is eaten by antelope species, such as topi and Thomson’s gazelle. Smaller animals such as mice and grasshoppers also feed on grass. Antelopes are eaten by predators such as cheetahs, lions and serval cats. Grasshoppers and mice are eaten by serval cats and tawny eagles. Ruppell’s vulture feeds on dead mammals. shows part of the food web for this ecosystem. star grass red oat grass topi Thomson’s gazelle grasshoppers lions serval cats tawny eagles Complete the food web in by writing the names of the organisms in the boxes. Write your answers in the boxes in . Name the trophic level of the following species: star grass topi State the source of energy for the food web shown in . State what happens to energy when it leaves an ecosystem, such as the African grassland. For Examiner's Use Nutrients are recycled in ecosystems but energy is not recycled. Explain why there are no more than four trophic levels in the ecosystem shown in . Fish, such as salmon reared in fish farms, are fed on high protein food made from animals. When eating this food, these fish are feeding as secondary consumers. Discuss the disadvantages of farming fish, such as salmon, for human food.
0610_s11_qp_33
THEORY
2011
Paper 3, Variant 3
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For Examiner's Use shows three annelid species and Ascaris lumbricoides, a species of nematode. Chaetopterus variopedatus Nereis diversicolor Lagisca flocculosa Ascaris lumbricoides annelids nematode not drawn to scale State three features shown by the three annelid species that are not shown by the nematode species. For Examiner's Use Organisms are given two names, e.g. Nereis diversicolor. State what is meant by the first name. N. diversicolor is a filter feeder. It filters plankton from sea water. Annelids like N. diversicolor form an important part of the ecosystems of estuaries. Fish feed on annelids when the sea covers the mud in the estuary. When the tide is out wading birds are the main predators of annelids. Birds of prey are the main predators of the wading birds. Explain the term ecosystem. Use the space below to draw a food chain for the estuary ecosystem when the tide is out. Describe the advantages of drawing a food web rather than a food chain for an ecosystem. For Examiner's Use The palolo worm is a species of annelid that lives on coral reefs in the Pacific Ocean. At certain times of the year, all the worms in an area leave their burrows to swim to the surface. They all release their gametes into the water at the same time. This is known as mass spawning. Suggest the advantages of having mass spawning occurring only at certain times of the year and not all year round. Meiosis is involved in producing gametes in palolo worms. Describe how meiosis differs from mitosis and explain why meiosis is important for the production of gametes.
0610_s13_qp_33
THEORY
2013
Paper 3, Variant 3
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Myriapods are a group of arthropods that are commonly found in soil habitats in many parts of the world. Many myriapods are very small and not easy to identify. shows four species of myriapod, not drawn to the same scale. Polydesmus denticulatus Scutigera coleoptrata Cylindroiulus punctatus Scolopocryptops sexspinosus State three features of all myriapods that are visible in . Describe three features of myriapods that could be used to make a dichotomous key to distinguish between the four species in . Mitochondria are cell structures that contain a small quantity of DNA. Scientists are sequencing the DNA of one particular gene in mitochondria to help identify different species of many animals including myriapods. The sequences that they find are called ‘barcodes’. State the part of the cell that contains most of the DNA. Suggest how DNA barcoding might be useful in the conservation of animals, such as myriapods. State the function of DNA in cells. A student found the following information about the feeding relationships between some organisms in a soil habitat. Dead organic matter, such as leaves, provides food for bacteria and soil fungi. Earthworms eat dead leaves. Many millipedes feed on dead plant matter and also on soil fungi. Nematodes feed on bacteria and are eaten by springtails. Centipedes are predators that feed on earthworms, millipedes and springtails. Draw a food web to show the feeding relationships described above. Describe the roles of the soil organisms in the carbon cycle.
0610_s14_qp_32
THEORY
2014
Paper 3, Variant 2
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Questions Discovered
345