19.2. Food chains and food webs
A subsection of Biology, 0610, through 19. Organisms and their environment
Listing 10 of 345 questions
is a drawing of a rainforest food web. sloth golden lion tamarin howler monkey banana plant anaconda ocelot jaguar pineapple plant not to scale State the name of one producer shown in . State the name of one herbivore shown in . State the number of carnivore species shown in . Use the information in to complete the food chain that contains the howler monkey and three other organisms. howler monkey Overhunting of golden lion tamarins caused the population of anacondas and sloths to change. Explain why the populations of: • anacondas decrease • sloths increase. anacondas sloths State the principal source of energy for food webs. Conservationists counted the number of organisms in each feeding level for one of the food chains in a rainforest. The data were used to draw a pyramid of numbers. Table 4.1 shows the data. Table 4.1 feeding level number of organisms width of the bar in the pyramid of numbers / cm producer 0.4 primary consumer 10.0 secondary consumer tertiary consumer 0.8 Complete Table 4.1 by calculating the width of the bar for the secondary consumer feeding level. cm Using the information in Table 4.1 and your answer to 4, draw a pyramid of numbers on the grid. Each small square on the grid is 0.2 cm wide. Label each bar with the feeding level. Deforestation is a cause of habitat loss for many organisms. List three other undesirable effects of deforestation.
0610_s22_qp_32
THEORY
2022
Paper 3, Variant 2
View
Coral reefs are important ecosystems. Complete the sentence about ecosystems. An ecosystem can be defined as a unit containing the of organisms and their , interacting together. is a photograph of a coral reef. is part of a food web for a coral reef ecosystem which is similar to the one shown in . phytoplankton zooplankton coral polyps butterflyfish blue chromis fish fan worm pufferfish reef shark angelfish sea sponge State the number of secondary consumers shown in . State the name of a species that feeds at more than one trophic level in . State the number of different organisms in the shortest food chain in . State the evidence from the food web in , that phytoplankton are producers. It is rare for there to be more than five trophic levels in an ecosystem. Explain what limits the number of trophic levels in food webs. One threat to aquatic ecosystems, such as coral reefs, is global climate change. Discuss the threats to aquatic ecosystems, other than climate change.
0610_s22_qp_42
THEORY
2022
Paper 4, Variant 2
View
For Examiner's Use Marine conservationists are concerned that fish stocks in the sea are decreasing. Drastic measures will have to be taken to stop the extinction of many fish species. shows a marine food web. Tuna are large carnivorous fish that are an important human food. Dolphins may be caught in fishermen’s nets and die. photosynthetic algae growing on reefs herbivorous fish zooplankton photosynthetic plankton small carnivorous fish squid tuna dolphins trophic level fishing boat State the names given to trophic levels 1 and 3. For Examiner's Use Explain why it is more energy efficient for humans to eat herbivorous fish rather than tuna. Explain why it is necessary to conserve animals, such as tuna and dolphins, which are at trophic level 4. Many seas are polluted by non-biodegradable plastics. Suggest the likely effects of this pollutant on the marine environment.
0610_w10_qp_31
THEORY
2010
Paper 3, Variant 1
View
For Examiner's Use The brown plant hopper is a serious insect pest of rice. Spraying with pesticides is a common way to control it. However, brown plant hoppers have become resistant to pesticides. shows the effect of spraying pesticides against populations of this insect pest. days after transplanting rice mean number of brown plant hoppers per m2 sprays with pesticide Define the term population. For Examiner's Use Use to describe the effect of pesticides on populations of the brown plant hopper. Some pesticides used against insects kill them on contact. Others are systemic pesticides. Explain how these systemic pesticides kill insects. For Examiner's Use As an alternative to spraying pesticides, some farmers use predatory animals, such as the hunting spider, Lycosa pseudoannulata, to control brown plant hoppers. During an investigation into the effectiveness of this method, brown plant hoppers were put into cages in rice fields. The plant hoppers could not leave the cages but were able to feed. Predators, such as hunting spiders, could enter some of the cages to feed. shows the change in numbers of brown plant hoppers in these cages over a period of time. mean number of brown plant hoppers per cage time / days cages closed cages closed to predators to predators cages open cages open to predators to predators cages closed to predators cages open to predators For Examiner's Use Use the information in to explain the advantages of using predators, such as spiders, to control brown plant hoppers. Rice growing has involved the destruction of forests. Describe the long-term effects of deforestation on the environment.
0610_w11_qp_31
THEORY
2011
Paper 3, Variant 1
View
is a vertical section of a human molar tooth and surrounding structures. D C B A State the names of the parts labelled A to D on . A B C D Describe and explain the function of molar teeth. is an X-ray of decay in a molar tooth. decayed molar tooth Explain how tooth decay occurs. is a food web for a forested area in Central America. hooded skunk jaguar bobcat great horned owl long-tailed weasel nine-banded armadillo termites red harvester ants lowland tapir collared peccary muhly grass Peruvian feather grass Complete Table 3.1 using information from . Table 3.1 trophic level description example from herbivore producer feeds on tertiary consumers secondary consumer shows the flow of energy through a food chain. The size of each box represents the energy available in each trophic level, numbered 1, 2, 3 and 4. respiration respiration respiration Z trophic level 1 trophic level 2 trophic level 3 trophic level 4 solar energy State the term given to the group of organisms represented by Z in . Explain, with reference to , why food chains usually have fewer than five trophic levels. Intensive livestock production can be damaging to natural ecosystems. shows intensive farming of chickens. Describe the negative impact on an ecosystem of the intensive production of livestock, such as chickens. Forests are cleared for farmland. Deforestation can lead to a loss of soil (soil erosion). Explain the effects of soil erosion on ecosystems.
0610_w20_qp_42
THEORY
2020
Paper 4, Variant 2
View
is part of a food web in a rainforest. coconut tree iguana frog jaguar monkey grasshopper anaconda fruit bat banana plant Complete using the information in . The first one has been done for you. the number of different producers the number of different secondary consumers the number of different trophic levels in the food web how many different trophic levels monkeys feed at Sometimes anacondas are able to kill and eat jaguars. Using the information in , state the name of the highest possible trophic level of an anaconda that eats a jaguar. Explain why the population of anacondas is always smaller than the population of fruit bats in the food web shown in . Use the concept of energy flow in your answer. A giant rat was discovered in a natural rainforest on Vangunu Island. Scientists wanted to determine if it was a new species. Explain how scientists can use tissue samples to classify this rat. Giant rats eat coconuts. Coconuts are grown as a monoculture for human consumption. Suggest how monocultures of crop plants can result in the extinction of some animals.
0610_w20_qp_43
THEORY
2020
Paper 4, Variant 3
View
Ecologists studied an area of woodland and estimated the biomass of each trophic level for one of the food chains in the woodland. Some students wanted to use the data to draw a pyramid of biomass for the food chain. Table 3.1 shows the students’ table. The students added a column to calculate the width of the bars they would need to draw. Table 3.1 trophic level biomass / g m−2 width of bar / cm producer 12.0 primary consumer 4.8 secondary consumer 1.6 tertiary consumer Complete Table 3.1 by calculating the missing value and writing it in the table. Using the information in Table 3.1, draw a pyramid of biomass. Label each bar with the trophic level. A type of organism gains energy from waste organic material from all trophic levels. State the name of this type of organism. Outline how organisms in the first trophic level of the woodland food chain produce biomass using energy from the Sun. Explain why the fourth trophic level has the least biomass in this food chain. The woodland is a conservation area. Outline the possible benefits of conserving this specific area of woodland.
0610_m18_qp_42
THEORY
2018
Paper 4, Variant 2
View
Questions Discovered
345