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HIA International — Grade 8

Unit 1: Photosynthesis and the carbon cycle

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Unit 2: Properties of materials

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Unit 3: Forces and energy

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Unit 4: Maintaining life

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Unit 5: Reactivity

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Unit 6: Sound and space

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Unit 7: Genes and inheritance

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Unit 8: Rates of reaction

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Unit 9: Electricity

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Quiz

Checkpoint Grade 8 Unit 7 – 7.4 Microorganisms In Food Webs

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Microorganisms In Food Webs Checkpoint Biology quiz set 2: free practice for Cambridge Checkpoint Biology 0893. Work through this Microorganisms In Food Webs Checkpoint Biology quiz set 2 and get instant feedback on every answer. If you get stuck, review the 9.4 Microorganisms in food webs lesson. More practice: Cambridge Checkpoint Biology 0893 — all units. Syllabus: Cambridge Lower Secondary programme.

  • Questions count: 50
  • Passing grade: B+
  • Time limit:
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1.
Which statement correctly describes decomposer?
substances needed for growth
returning materials for reuse
interconnected food chains
an organism that breaks down dead material
2.
Which statement correctly describes nutrients?
an organism that breaks down dead material
returning materials for reuse
interconnected food chains
substances needed for growth
3.
Which statement correctly describes recycling?
an organism that breaks down dead material
interconnected food chains
returning materials for reuse
substances needed for growth
4.
Which of these is the FIRST step in the correct order?
decomposers break it down
producers take up nutrients
organism dies or produces waste
nutrients return to the environment
5.
Which step comes immediately after "decomposers break it down"?
organism dies or produces waste
producers take up nutrients
nutrients return to the environment
6.
Which practical work belongs to Microorganisms In Food Webs?
Interpret feeding relationships and check arrow direction from food to consumer
Plan an investigation into how temperature affects the rate of decay
Use sterile technique and observe colonies without opening cultures
Add microorganisms to food-web models and connect decomposition with nutrient cycling
7.
Mateo recorded the temperature in the centre of his compost heap. The temperature had been falling, but it rose again after he turned the heap on day 22. Which explanation is best?
Dr Dabour Hub Academy - figure 1
Turning let in oxygen, so decomposers respired faster and released more heat
Turning mixed in cold air, which made the heap warm itself up to stay alive
Turning killed the bacteria, and heat was released as their cells dried out
Turning let sunlight reach the centre, so the peel began to photosynthesise
8.
Farah left one apple slice in each of six incubators to rot. What should she do about the result at 15 °C?
Dr Dabour Hub Academy - figure 2
Use it to conclude that 15 °C is the best temperature for decomposers
Change the other five results so they fit the pattern of the 15 °C result
Treat it as anomalous and repeat the 15 °C test before drawing a conclusion
Keep it, because the highest value in a set of results is always the most accurate
9.
Jun measured carbon dioxide given off by soil with leaf litter after adding different volumes of water. Why was less carbon dioxide released at 50 and 60 cm³ than at 30 cm³?
Dr Dabour Hub Academy - figure 3
The extra water dissolved the dead leaves, so there was nothing left to decay
Water filled the air spaces, so decomposers had less oxygen for respiration
Decomposers only respire in completely dry soil, so any water slows them down
The water was a producer and took in the carbon dioxide by photosynthesis
10.
Lucia left two nylon mesh bags of oak leaves on a woodland floor for three months, as shown. Each option pairs a part of her method with its purpose. Which pairing is correct?
Dr Dabour Hub Academy - figure 4
Bag X – keeps out every living thing so the leaves cannot decay
Drying the leaves first – adds extra water for the decomposers to use
Same mass in each bag – makes the mesh size the dependent variable
Bag Y – lets in bacteria and fungi but keeps out earthworms
11.
Kofi stored slices of the same loaf in four ways and checked them daily for 30 days. He concludes: "Removing water stops decay just as well as freezing." What is the main weakness in his conclusion?
Dr Dabour Hub Academy - figure 5
Toasting also heated the bread, which may have killed the mould spores
The freezer bread was colder than the fridge bread, so the test was unfair
Mould is a producer, so it would not grow on dried bread in any case
Thirty days is too long, because mould can only be seen in the first week
12.
The Sonoran Desert is almost as warm as the Amazon rainforest, yet leaves take much longer to disappear. Which explanation fits the data?
Decomposers work fastest in cold places, and the desert has cold nights
Desert plants make leaves with no nutrients, so decomposers ignore them
Desert leaves are producers, so they keep photosynthesising after falling
Decomposers need moisture as well as warmth, and the desert is too dry
13.
Hana and Omar followed the same method and got the same mean. Which statement about their results is correct?
Omar's results are more repeatable, as his values cover a wider range
Hana's results are more repeatable, as her three values are close together
Both sets are equally repeatable, because the two means are exactly equal
Neither set can be judged, because three dishes is too many to compare
14.
Ines buried equal masses of four materials in fine-mesh bags. Which conclusion is best supported by her results?
The plastic bag was broken down fastest because it is the thinnest material
Decomposers break down all dead plant material at the same rate
Decomposers broke down the three plant materials at different rates but not the plastic
The pine twig lost least mass because it contains the most nutrients
15.
Sara wants a fair test of how moisture affects the rate of composting. Which two bins should she compare?
Bins A and B
Bins B and C
Bins A and C
Bins B and D
16.
A bracket fungus on a fallen beech log grows a network of very thin threads through the wood. How does this help it feed?
The threads release enzymes into the wood and absorb the dissolved products
The threads trap sunlight inside the wood so the fungus can photosynthesise
The threads let the fungus swallow whole pieces of wood like an animal does
The threads carry minerals from the fungus into the log to feed the tree
17.
Why does fish stored in a freezer at −18 °C stay fresh for months, while fish on a kitchen worktop goes bad in a day?
Freezing turns the fish proteins into minerals, which cannot rot
Freezing makes the fish a producer, so it makes its own food
Freezer air contains more oxygen, which stops microbes feeding
Cold greatly slows the growth and activity of decomposers
18.
An orchard owner sprays the ground every year with a chemical that kills soil fungi. After several years, which change is most likely?
Leaf litter disappears faster because fewer fungi compete
The trees grow faster because fungi no longer eat their roots
Leaf litter builds up and the apple trees grow less well
Soil minerals increase because fungi stop taking them up
19.
A woolly mammoth that died 30 000 years ago was found frozen in Siberian permafrost with its skin and muscle still present. Which is the best explanation?
Mammoths had no bacteria in their bodies, so nothing could make them decay
Low temperature kept decomposers too inactive to break the body down
The ice acted as a producer and fed the body, keeping its cells alive
Decomposers break down only plants, so animal bodies never decay
20.
Priya says: "Bacteria cause disease, so the best compost heap would have all its bacteria removed." Which reply is most accurate?
She is right, because compost is made by the plants rotting on their own
She is right, because only viruses are needed to break down garden waste
Bacteria are needed only to make the heap smell, not to break down waste
Most bacteria are harmless, and in compost they break down the waste into minerals
21.
Tom puts bacteria and fungi at the very top of his food web, above the eagle, "because they eat everything in the end". What is the best comment?
They should link to every level, as they feed on dead remains and waste from all of them
He is correct, because decomposers are the top predators in every ecosystem
They should be at the bottom, because they are producers that make food from light
They should be left out, because microorganisms are not part of food webs
22.
Aisha wants to investigate how temperature affects how fast bread goes mouldy. Which plan is best?
Put one piece of bread in a fridge and a different brand in a warm room, and check them after one week
Put equal pieces of bread at 25 °C, some dry and some damp, and record the days until mould appears
Put equal pieces of the same damp bread in sealed bags at 5, 15, 25 and 35 °C, three bags at each, and record the days until mould appears
Put bread at four temperatures and open the bags each day to smell them, stopping when one smells bad
23.
Fallen leaves on a forest floor contain chemical energy. After decomposers have completely broken the leaves down, what has happened to most of this energy?
It was returned to the soil and taken up again by roots
It was changed into minerals, which plants use as energy
It was released by decomposer respiration and lost as heat
It stayed stored in the leaves until the next spring
24.
Carbon dioxide builds up inside a sealed jar of damp, rotting leaves. Which process in the decomposers produces this gas?
Photosynthesis in the threads of the fungi
Respiration of the food they have digested
Evaporation of water from the leaf surfaces
Absorption of minerals from the jar's air
25.
Each option pairs a way of preserving food with the condition it takes away from decomposers. Which pairing is correct?
Freezing peas – the light that decomposers use to make food
Vacuum packing – the warmth that decomposers need
Drying fruit – the water that decomposers need
Keeping milk in a fridge – the oxygen that decomposers need
26.
Yusuf grows mould on agar plates in incubators at 10, 20 and 30 °C and measures the area of mould after 4 days. Each option pairs a variable with its type. Which pairing is correct?
Area of mould after 4 days – independent variable
Temperature of the incubator – dependent variable
Number of days of growth – dependent variable
Volume of agar in each dish – control variable
27.
Which statement correctly describes decay?
an organism that breaks down dead material
a factor that can change
breakdown of organic matter
a type of fungus
28.
Which statement correctly describes mould?
breakdown of organic matter
an organism that breaks down dead material
a factor that can change
a type of fungus
29.
Which term is described as: an organism that breaks down dead material?
nutrients
recycling
food web
decomposer
30.
Which term is described as: substances needed for growth?
decomposer
food web
nutrients
recycling
31.
Which term is described as: returning materials for reuse?
decomposer
food web
recycling
nutrients
32.
Which term is described as: breakdown of organic matter?
decomposer
variable
decay
mould
33.
Which term is described as: a type of fungus?
decay
variable
mould
decomposer
34.
Which term is described as: a microorganism that breaks down dead material and releases nutrients?
decomposer
nitrogen cycle
carbon cycle
biodegradable
35.
Match the term to its correct meaning: decomposer
a microorganism that breaks down dead material and releases nutrients
the substance decomposers release to break down large molecules outside their cells
digestion that happens outside the cell before the products are absorbed
the continuous movement of carbon between the air, living things and the ground
36.
Which term is described as: the continuous movement of carbon between the air, living things and the ground?
carbon cycle
sewage treatment
landfill
biodegradable
37.
Fungi and many bacteria feed as _____: they release enzymes onto dead material and absorb the digested products.
producers
predators
herbivores
saprotrophs
38.
When decomposers break down proteins in dead organisms, they return _____ to the soil, which plants absorb through their roots.
nitrates and other minerals
energy from the Sun
glucose for respiration
oxygen for the leaves
39.
Decomposers release _____ to break material down outside their cells.
vitamins
minerals
hormones
enzymes
40.
Comparing containers B and C shows that removing oxygen slows the decay of strawberries. True or false?
False – the statement is wrong
False – containers C and D should be compared, as they differ in oxygen only
True – the statement is correct
False – B and C differ in temperature, so they cannot be compared
41.
The data support the idea that animals at 1000 m depend on food made near the surface, which sinks down as dead material and waste. True or false?
False – the statement is wrong
True – the statement is correct
False – there are producers at 1000 m that make food without light
False – deep-sea animals need no food because the water is so cold
42.
Decomposers digest dead material outside their cells and then absorb the small soluble molecules produced. True or false?
True – the statement is correct
False – the statement is wrong
False – decomposers swallow dead material and digest it inside a stomach
False – decomposers absorb whole dead leaves without digesting them
43.
Vacuum-packed meat keeps longer because most decomposers need oxygen to respire and grow. True or false?
False – the statement is wrong
False – vacuum packing works only by keeping the meat very cold
False – decomposers need no oxygen, so the packing only keeps out dust
True – the statement is correct
44.
Plants absorb the carbon dioxide released by soil decomposers through their roots, together with minerals. True or false?
True – the statement is correct
False – roots take up minerals; carbon dioxide enters through the leaves
True, because roots absorb everything that decomposers release
True, but only for plants growing in very wet soil
45.
Viruses are important decomposers because they break down dead leaves on the forest floor. True or false?
True – the statement is correct
True, because viruses are the smallest microorganisms
False – viruses can reproduce only inside living cells
True, but only in warm and moist forest soils
46.
Decomposers are found only in soil, so dead fish on the sea bed do not decay. True or false?
True – the statement is correct
False – decomposers also live in water and sea-bed mud
True, because salt water kills every kind of microorganism
True, but only in the deepest parts of the ocean
47.
Phytoplankton release oxygen into the water as they photosynthesise. True or false?
False – the statement is wrong
False – phytoplankton take in oxygen and release only minerals
True – the statement is correct
False – phytoplankton are decomposers and release carbon dioxide only
48.
When growing moulds on agar jelly in class, the Petri dish lids should be taped shut and not opened, so that spores do not escape. True or false?
True – the statement is correct
False – the statement is wrong
False – lids should be removed so the moulds get enough light
False – taping is only needed if the moulds are producers
49.
Decomposers release enzymes to break down material outside their cells. - True or false?
True
False
50.
Decomposers swallow large lumps of material whole. - True or false?
True
False
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Part of Unit 7: Genes and inheritance — see every lesson and quiz in this unit.
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