Unit 3 Topic 2: Functioning ecosystems and succession

Photosynthesis in the leaves of a mangrove on the Brisbane River changes the form of the energy the leaves absorb. Which statement describes this transformation?

Which statement correctly defines the net primary productivity (NPP) of an ecosystem?

A survey of a seagrass meadow in Moreton Bay estimated the seagrass's gross primary productivity at 18 400 kJ m⁻² year⁻¹. The seagrass used 10 900 kJ m⁻² year⁻¹ in cellular respiration. What is the net primary productivity of the seagrass?

In a Brisbane River mangrove forest, the net primary productivity of the mangroves is 42 000 kJ m⁻² year⁻¹. The leaf-eating crabs that feed on them gain 3 150 kJ m⁻² year⁻¹ as new biomass. What is the efficiency of energy transfer from the mangroves to the crabs?

Students estimated the energy flows through grasshoppers in a grassland plot on the Darling Downs (table). What percentage of the grass's net primary productivity becomes new grasshopper biomass?

The table shows estimates of what happens to the light reaching the canopy of a rainforest at Lamington. What percentage of the light reaching the canopy is converted to chemical energy by photosynthesis?

A student claims that the energy in a food chain is recycled: decomposers break down dead animals, and the energy returns to the producers. Which statement best corrects the student?

A single large fig tree in a rainforest supports about 2 000 caterpillars, which are eaten by about 40 small birds. Which statement correctly describes the ecological pyramids for this food chain?

In a grassland, insect-eating lizards convert about 9% of the energy they eat into new biomass, but insect-eating birds convert about 1%. Which statement best explains the difference?

In an ocean food chain, the phytoplankton's net primary productivity is 30 000 kJ m⁻² year⁻¹. The transfer efficiencies are 15% from phytoplankton to zooplankton, 10% from zooplankton to small fish and 8% from small fish to tuna. How much energy reaches the tuna each year?

Food chains in a Queensland eucalypt woodland rarely have more than four or five trophic levels. Which statement best explains this?

A stand of young eucalypts near Toowoomba gains dry biomass every year. Which statement best links this gain in biomass to the carbon cycle?

Farmers on the Darling Downs often plant a legume crop such as chickpeas between wheat crops. Bacteria living in nodules on the legume roots carry out which process?

Which statement correctly describes nitrification in soil?

After weeks of heavy rain, a cane field near Mackay stayed waterlogged, and soil tests showed its nitrate content had fallen sharply. Which process best explains the loss of nitrate?

Which process in the water cycle moves water from the soil into the atmosphere through plants?

Researchers measured the carbon flows in a plot of eucalypt forest over one year (table). There was no fire and no carbon left the plot in water. Which conclusion is supported by the data?

A large area of forest in a catchment is cleared and replaced with short grass. Which change to the local water cycle is most likely?

In the nitrogen cycle, what do decomposers do with the nitrogen in dead leaves and animal wastes?

Which statement best explains why burning coal increases the amount of carbon dioxide in the atmosphere?

Which statement correctly describes a way that carbon moves from the atmosphere into long-term storage in the ocean?

A leaf falls from a wattle tree and decomposes. Some of its nitrogen ends up in a protein of a grass plant growing nearby in well-aerated soil. Which sequence shows the forms the nitrogen passes through, in order?

Reef-building corals on the Great Barrier Reef contain single-celled algae (zooxanthellae) in their tissues. The algae supply the coral with sugars from photosynthesis, and the coral supplies the algae with shelter, carbon dioxide and nutrients. Which interaction is this?

A paralysis tick attaches to a bandicoot in a Brisbane backyard and feeds on its blood for several days, weakening the bandicoot. Which interaction is this, and how does it affect each species?

A staghorn fern grows high on the trunk of a rainforest tree at Mount Tamborine. It gains light by growing high up and takes water and nutrients from rain and falling debris, not from the tree. The tree is not affected. Which interaction is this?

Which statement best describes the ecological niche of a species?

Two species of duckweed are grown together in tanks with limited nutrients. Both need the same nutrients and the same light at the water surface. After eight weeks only one species remains. Which principle does this illustrate?

Three species of honeyeater feed on insects in the same eucalypt woodland. One feeds mainly in the upper canopy, one on the outer leaves of the mid layer and one on the trunks and bark. All three persist there. Which statement best explains how they coexist?

On a rocky shore, students scraped barnacle species Y off some rock surfaces and left others untouched. The table shows where barnacle species X was found a year later. Species Y grows faster than X and lives from 0 to 1.0 m above low tide. Which conclusion is best supported?

Ecologists on a rocky shore on North Stradbroke Island removed one species at a time from sets of plots (table). In plots where the whelk was removed, mussels spread over most of the rock. Which species best fits the definition of a keystone species?

A greenhouse grower in the Lockyer Valley counted two mite species on strawberry plants every two weeks (graph). Which interpretation of the graph is best supported?

The table describes part of a food web on a reef flat. Turf algae compete with young corals for space on the reef. If triggerfish were heavily overfished, which chain of changes is most likely?

Two species of snail both graze the same film of algae on rocks. Students counted both species in six quadrats (table). Which interaction do the data most likely suggest?

Which statement best describes a keystone species?

Which statement best defines the carrying capacity of an ecosystem for a species?

Twenty wallabies were released onto an island with no wallabies. The graph shows their numbers over the next 20 years. What is the best estimate of the island's carrying capacity for wallabies?

Eastern grey kangaroos in a grazing reserve had been stable at about 600 animals for several years. A two-year drought then reduced the growth of pasture. Which outcome is most likely?

After heavy rain, fertiliser runs off farms into a coastal lake. A few weeks later there is an algal bloom, and dead fish are found. Which sequence best explains the fish deaths?

The table shows the concentration of a persistent pesticide measured in a lake food chain. The fish-eating bird feeds on the small fish. By what factor is the pesticide concentrated from the small fish to the bird?

Native vegetation on a coastal floodplain is cleared and replaced by a sugarcane monoculture. Which effect on the community is most likely?

Heavy line fishing removes most of the large predatory fish from a reef. Which longer-term effect on the reef community is most likely?

A large forest is cleared for housing except for several small, isolated patches. Which effect on the koalas living in the patches is most likely?

Rangers recorded rainfall, pasture biomass and the number of kangaroos in a reserve over four years (table). Which statement is best supported by the data?

Which of these is an example of primary succession?

A bushfire burns an area of open eucalypt forest. Within months, grasses and shrubs appear, and the community develops faster than it would on bare rock. Which statement best explains why?

Which set of features makes a species an effective pioneer on bare ground?

During succession on an abandoned paddock, which change in the plant species is most likely over time?

Ecologists compared five paddocks abandoned at different times (table). Which conclusion is best supported?

On a new sand dune, the first plants to establish are grasses that trap sand and add dead leaves to the sand. Shrubs later replace them. Which statement best explains the replacement?

Which statement best describes a climax community?

The table compares plant biomass and net primary productivity in a tropical rainforest and a tropical grassland. Which conclusion is best supported?

The table shows energy flows from herbivores to carnivores in a grassland. What is the efficiency of energy transfer from herbivore net production to carnivore net production?

Students incubated identical samples of moist soil from a pasture in two jars for four weeks (table). Which explanation of the results is best supported?

Ecologists placed mesh cages that keep out birds but not insects around some eucalypt saplings and left others open (table). Which conclusion is best supported?

The table shows mercury concentrations measured in a mangrove food chain on the Brisbane River. Which statement is supported by the data?

In a billabong near Rockhampton, the gross primary productivity of the algae is 25 000 kJ m⁻² year⁻¹, and the algae use 15 000 kJ m⁻² year⁻¹ in respiration. Snails graze the algae, and the snails' net production (new snail biomass) is 12% of the algae's net primary productivity. A fish that eats only these snails produces 108 kJ m⁻² year⁻¹ of new biomass. What is the efficiency of energy transfer from the snails to the fish?

The table accounts for all the light energy reaching a sorghum crop on the Darling Downs over one growing season: every kilojoule was reflected, transmitted to the soil, lost as heat or converted to chemical energy by photosynthesis. What percentage of the light reaching the crop became new plant biomass?

A grower near Bundaberg tested a chemical that slows the activity of nitrifying bacteria. Three plots were given fertiliser in week 0 (table), and heavy rain waterlogged all three plots from week 3 to week 5. Which explanation of the nitrogen lost as gas is best supported by the data?

A clear chamber over a pasture plot measured the carbon exchanged between the plot (plants and soil organisms) and the air. During the 13 hours of daylight the plot took up a net 0.6 g C m⁻² h⁻¹; during the 11 hours of darkness it released 0.2 g C m⁻² h⁻¹. The plot's total respiration rate was the same by day as by night. How much carbon did the pasture plants take up by photosynthesis over the 24 hours?

Ecologists surveyed semi-arid grassland on both sides of a dingo-proof fence in western Queensland (table). Dingoes eat kangaroos, foxes and small mammals; foxes eat small mammals; kangaroos eat grasses; the small mammals eat grass seeds. Which statement best identifies the keystone species and accounts for the data?

Two species of Paramecium, A and B, were grown in identical tubes fed the same bacteria: each species alone, and both species together (graph). Which interaction is best supported by the data?

A lagoon near Townsville was counted for magpie geese every year (graph). In year 8 a severe drought dried the lagoon, and silt washed in when rain returned, so the lagoon has been smaller ever since. From the graph, by what percentage did these events lower the lagoon's carrying capacity for magpie geese?

Rangers counted rock-wallabies at two rocky colonies in central Queensland that share the same climate (table). Rainfall was normal in every year except year 5, a severe drought. Within years 1 to 3 and within years 7 to 9 the count at each colony changed little from year to year. Which conclusion is best supported?

Ecologists recorded four plant species on coastal sand dunes of known age, then surveyed a dune of unknown age (table). Which statement best describes the surveyed dune?

Light energy reaching a pasture is 2 500 000 kJ m⁻² year⁻¹. The pasture converts 1.2% of this light to chemical energy by photosynthesis, and uses 55% of that chemical energy in its own respiration. What is the pasture's net primary productivity?