CIE iGCSE Co-Ordinated Science B18.2 Food chains and food webs Exam Style Questions Paper 3
Question
(a) Fig. 4.1 shows a food web from a rainforest environment.
(i) Construct a food chain from Fig. 4.1 that includes the snake.
…………………………………………………………………………………………………………………….
(ii) Use Fig. 4.1 to identify one:
herbivore ………………………………………………………………………………………….
tertiary consumer. ………………………………………………………………………………………….
(iii) Removal of banana trees can cause the extinction of three‐toed sloths.
List two other undesirable effects of deforestation.
(b) Banana trees are producers that make their own carbohydrates.
State the two raw materials that producers need to make their own carbohydrates.
(c) A student makes a statement:
‘All carnivores are consumers but not all consumers are carnivores.’
Explain this statement.
(d) State the name of the type of organism that gets its energy from dead organic matter.
▶️Answer/Explanation
Ans : 4(a)(i) banana tree → howler monkey → snake ;;
4(a)(ii) herbivore howler monkey / three-toed sloth ;
tertiary consumer jaguar ;
4(a)(iii) any two from:
loss of soil / soil erosion ;
flooding ;
increase of carbon dioxide in the atmosphere ;
habitat destruction / animals displaced ;
decreased biodiversity ;
AVP ;;
4(b) carbon dioxide ;
water ;
4(c) consumers get their energy from eating animals or plants / consumers can be herbivores ;
carnivores get their energy from eating (only) animals ;
4(d) decomposer ;
Question
(a) Horses are herbivores.
Define the term herbivore.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(b) Fig. 7.1 is a photograph of the lower jaw of a horse.
(i) The dental pattern of a horse is similar to that of humans.
Identify the type of teeth labelled X and Y in Fig. 7.1.
X ……………………………………………………………………………………………………………….
Y ………………………………………………………………………………………………………………..
(ii) Identify the type of teeth found in a human jaw but not present in the jaw shown in Fig. 7.1.
………………………………………………………………………………………………………………….
(iii) State the name of the type of digestion that takes place using teeth.
…………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………
(c) The statements describe some processes that occur in the alimentary canal.
Place ticks (✓) to show all the statements that describe the process of absorption.
(d) Complete these sentences about biological molecules.
Choose words or phrases from the list.
Each word or phrase may be used once, more than once or not at all.
amino acids fatty acids glycerol glycogen starch
Proteins are made from smaller molecules called …………………………………. .
Glucose is used to make two larger molecules called
………………………………………………… and ………………………………………………… .
Iodine solution is used to test for the presence of ………………………………………………… .
▶️Answer/Explanation
Ans: 7(a) animal that gets its energy ;
from eating plants / AW ;
7(b)(i) X – premolars ;
Y – incisors ;
7(b)(ii) canines ;
7(b)(iii) mechanical ;
7(c)
;;
2 ticks and 2 correct = 2 marks
3 ticks and 2 correct = 1 mark
otherwise 0 marks
7(d) amino acids ;
glycogen ;
starch ;
starch ;
Question
(a) Fig. 1.1 is a diagram of a marine food web.
Table 1.1 shows terms used to describe the organisms in Fig. 1.1.
Place ticks (✓) in the boxes to show the term(s) used to describe each organism.
(b) An orca eats arctic cod and leopard seal.
Add this information to the food web in Fig. 1.1.
(c) State the principal source of energy for all food chains.
(d) The process of photosynthesis occurs in some marine organisms.
(i) State the word equation for photosynthesis.
…………………………………………………………………………………………………………………….
(ii) State the name of the cell structure where photosynthesis occurs.
…………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 1(a)
1 mark for each row ;;;;
1(b) arrows drawn from leopard seal and artic cod to orca ;
1(c) Sun ;
1(d)(i) carbon dioxide + water → glucose + oxygen ;
1(d)(ii) chloroplast ;
Question
(a) A researcher collects some information about organisms that live in a desert environment.
Fig. 10.1 is a summary of the information.
(i) Construct a food chain from the information given in Fig. 10.1.
…………………………………………………………………………………………………………………….
(ii) Table 10.1 contains the names of the organisms from Fig. 10.1 and some of the terms that can be used to describe them.
Complete Table 10.1 by placing ticks (√) in the boxes to show all the terms that describe each organism. Use only the information given in Fig. 10.1.
One row has been done for you.
(b) State the name of the type of organisms that get their energy from dead and waste organic matter.
……………………………………………………………………………………………………………………………
(c) State the name of the principal source of energy for all food chains.
……………………………………………………………………………………………………………………………
(d) Nutrition is one of the characteristics of living things.
State the name of three other characteristics.
1 ………………………………………………………………………………………………………………………………
2 ………………………………………………………………………………………………………………………………
3 ………………………………………………………………………………………………………………………………
(e) State the name of the basic building blocks of which all living organisms are made.
…………………………………………………………………………………………………………………………………
▶️Answer/Explanation
Ans: 10(a)(i) cactus → desert rats → snake → desert fox ;;
10(a)(ii)
1 mark for each correct row ;;;
10(b) decomposer ;
10(c) Sun ;
10(d) any three from:
movement ;
respiration ;
sensitivity ;
growth ;
reproduction ;
excretion ;
10(e) cells ;
Question
(a) Fig. 4.1 shows part of a desert food web.
(i) Identify the name of one producer in Fig. 4.1.
▶️Answer/Explanation
Answer:
Yucca plant or prickly pear
(ii) Identify the name of one herbivore in Fig. 4.1.
▶️Answer/Explanation
Answer:
Rat or rabbit
(iii) Identify the name of an organism that can be classified as both a secondary and tertiary consumer.
▶️Answer/Explanation
Answer:
Hawk
(iv) Use Fig. 4.1 to construct a food chain containing four organisms.
▶️Answer/Explanation
Answer:
Yucca plant → rabbit → fox → hawk
or prickly pear → rat → fox → hawk
or prickly pear → rabbit → fox → hawk
correct organisms ;
correct arrows (direction of energy transfer) ;
(b) A new species is introduced that eats yucca plants.
Explain the effect this has on the population of rabbits.
▶️Answer/Explanation
Answer:
number of rabbits decrease ;
more competition for food / less food to eat ;
(c) State the term used to describe organisms that get their energy from dead organic matter.
▶️Answer/Explanation
Answer:
Decomposers
(d) State the principal source of energy for all food chains.
▶️Answer/Explanation
Answer:
The Sun
(e) Plants play an important role in the carbon cycle.
Describe how an increase in plant population affects the concentration of carbon dioxide in the atmosphere.
▶️Answer/Explanation
Answer:
more carbon dioxide removed ;
used as material for photosynthesis ;
Question
(a) Below list shows some information about feeding relationships in a national park.
- Lions are the top predator. Lions eat jackals.
- Goats eat grass.
- Goats are eaten by jackals.
(i) Use the information to construct a food chain containing all the organisms.
▶️Answer/Explanation
Answer: grass → goat → jackal → lion
Explanation: The food chain starts with the producer (grass), which is eaten by the primary consumer (goat). The goat is then eaten by the secondary consumer (jackal), and finally, the jackal is eaten by the top predator (lion).
(ii) Use the information to identify the:
- producer
- secondary consumer
▶️Answer/Explanation
Answer:
Producer: grass
Secondary consumer: jackal
Explanation: The producer is the organism that produces its own food through photosynthesis, which is grass in this case. The secondary consumer is the organism that eats the primary consumer (goat), which is the jackal
(b) State the principal source of energy for all food chains.
▶️Answer/Explanation
Answer: The Sun
Explanation: The Sun is the primary source of energy for all food chains. Producers (plants) convert solar energy into chemical energy through photosynthesis, which is then passed through the food chain.
(c) Table 4.1 shows the number and types of teeth for goats and humans.
| Type of teeth | Number in goats | Number in humans |
|---|---|---|
| incisors | 8 | 8 |
| canines | 0 | 4 |
| premolars | 12 | 8 |
| molars | 12 | 12 |
(i) Goats have a greater total number of premolar and molar teeth than humans. Describe two other differences between the types and number of teeth in goats and humans.
▶️Answer/Explanation
Answer:
1. Goats have no canine teeth, while humans have 4 canine teeth.
2. Goats have more premolar teeth (12) compared to humans (8).
Explanation: Goats are herbivores and do not need canine teeth for tearing meat, which is why they have none. Humans, being omnivores, have canine teeth for tearing food. Additionally, goats have more premolar teeth to help them grind plant material.
(ii) Goats are herbivores. Humans are able to gain their energy by eating both animals and plants. Suggest reasons why goats have a greater total number of premolar and molar teeth than humans.
▶️Answer/Explanation
Answer:
Goats need more premolar and molar teeth to grind and break down tough plant material, which is their primary food source. Humans, being omnivores, have a more varied diet that includes both plant and animal matter, so they do not require as many grinding teeth.
Explanation: Herbivores like goats rely on plant material, which is tough and fibrous, requiring more grinding teeth (premolars and molars) to break it down effectively. Humans, with a more varied diet, have fewer grinding teeth because their diet includes softer foods like meat and cooked vegetables.
(iii) Circle the top two layers in a human tooth.
- cement
- dentine
- enamel
- gum
- pulp
- nerve
▶️Answer/Explanation
Answer: enamel and dentine
Explanation: The top two layers of a human tooth are the enamel, which is the hard outer layer, and the dentine, which lies beneath the enamel and is less hard but still protective.
Question
(a) Fig. 1.1 is a diagram of a food web in the sea.
(i) Construct a food chain from the food web shown in Fig. 1.1. Your food chain must include four organisms.
▶️Answer/Explanation
Answer: green algae → limpets → crab → lobster / phytoplankton → mussels → crab → lobster
Explanation: A food chain represents the flow of energy from one organism to another. In this case, the food chain starts with a producer (green algae or phytoplankton), which is eaten by a primary consumer (limpets or mussels), which is then eaten by a secondary consumer (crab), and finally by a tertiary consumer (lobster).
(ii) Table 1.1 shows some terms that can be used to describe organisms in the food web shown in Fig. 1.1. Place ticks (✓) in the boxes to show all the terms that describe each organism.
| carnivore | herbivore | producer | primary consumer | tertiary consumer | |
|---|---|---|---|---|---|
| crabs | |||||
| limpets | |||||
| lobsters | |||||
| phytoplankton |
▶️Answer/Explanation
Answer:
| carnivore | herbivore | producer | primary consumer | tertiary consumer | |
|---|---|---|---|---|---|
| crabs | ✓ | ||||
| limpets | ✓ | ✓ | |||
| lobsters | ✓ | ✓ | |||
| phytoplankton | ✓ |
Explanation:
- Crabs are carnivores as they eat other animals (limpets, mussels) and are tertiary consumers as they are at the top of the food chain.
- Limpets are herbivores as they eat producers (green algae) and are primary consumers as they are the first consumers in the food chain.
- Lobsters are carnivores as they eat other animals (crabs) and are tertiary consumers as they are at the top of the food chain.
- Phytoplankton are producers as they produce their own food through photosynthesis.
(iii) A disease kills all the limpets in the food web shown in Fig. 1.1. State why:
- the population of green algae increases
- the immediate population of mussels decreases.
▶️Answer/Explanation
Answer:
- The population of green algae increases due to less predation (by limpets).
- The population of mussels decreases because there is more predation of mussels by crabs or lobsters.
Explanation:
- When limpets are removed from the food web, there are fewer organisms feeding on green algae, leading to an increase in their population.
- With the absence of limpets, crabs and lobsters may increase their predation on mussels, leading to a decrease in the mussel population.
(b) Disease can cause organisms to become extinct. Deforestation is another reason for extinction of organisms. List two other undesirable effects of deforestation.
▶️Answer/Explanation
Answer:
- Loss of habitat
- Loss of soil
- Flooding
- Build-up of carbon dioxide in the atmosphere
Explanation:
- Loss of habitat: Deforestation destroys the natural habitats of many species, leading to a loss of biodiversity.
- Loss of soil: Trees help to hold soil together, and their removal can lead to soil erosion.
- Flooding: Trees absorb water, and their removal can lead to increased flooding.
- Build-up of carbon dioxide: Trees absorb carbon dioxide, and their removal contributes to increased levels of greenhouse gases in the atmosphere.
Question 7
Fig. 7.1 shows a food chain.
(a) Table 7.1 shows some of the terms that can be used to describe the organisms in the food chain in Fig. 7.1.
Complete Table 7.1 by placing ticks (✓) to identify the terms that can be used to describe each organism in this food chain.
| maize | locust | lizard | snake | |
|---|---|---|---|---|
| producer | ||||
| consumer | ||||
| carnivore |
▶️Answer/Explanation
Answer:
| maize | locust | lizard | snake | |
|---|---|---|---|---|
| producer | ✓ | |||
| consumer | ✓ | ✓ | ✓ | |
| carnivore | ✓ | ✓ |
Explanation:
– Maize is a producer because it produces its own food through photosynthesis.
– Locust is a consumer because it feeds on producers (maize).
– Lizard is a consumer and a carnivore because it feeds on other animals (locust).
– Snake is a consumer and a carnivore because it feeds on other animals (lizard).
(b) The Sun is the principal source of energy input to biological systems.
Describe how energy from the Sun is used to make organic nutrients.
▶️Answer/Explanation
Answer:
Energy from the Sun is used by plants (producers) in the process of photosynthesis to convert carbon dioxide and water into glucose (an organic nutrient). This glucose is then used by the plant for growth and energy, and it also serves as a source of energy for consumers in the food chain when they eat the plants.
Explanation:
– The Sun provides light energy, which is absorbed by chlorophyll in the leaves of plants.
– This energy is used to convert carbon dioxide and water into glucose and oxygen during photosynthesis.
– The glucose produced is an organic nutrient that stores chemical energy, which is then transferred through the food chain as organisms consume each other.
(c) Corn snakes are a type of snake often kept as pets.
Selective breeding has resulted in bright red-coloured corn snakes.
The sentences below describe the process of selective breeding of bright red corn snakes.
The sentences are not in the correct order.
Use numbers 1–5 to show the correct order.
The third sentence has been identified.
| Sentence | Order |
|---|---|
| Their offspring are observed and bright red snakes identified. | 3 |
| This process is repeated over many generations. | |
| The two bright red corn snakes are bred together. | |
| Two bright red corn snakes are selected. | |
| The bright red offspring are bred. |
▶️Answer/Explanation
Answer:
| Sentence | Order |
|---|---|
| Their offspring are observed and bright red snakes identified. | 3 |
| This process is repeated over many generations. | 5 |
| The two bright red corn snakes are bred together. | 2 |
| Two bright red corn snakes are selected. | 1 |
| The bright red offspring are bred. | 4 |
Explanation:
– Step 1: Two bright red corn snakes are selected.
– Step 2: The two bright red corn snakes are bred together.
– Step 3: Their offspring are observed and bright red snakes identified.
– Step 4: The bright red offspring are bred.
– Step 5: This process is repeated over many generations to ensure the trait is passed on.
Question
(a) Fig. 4.1 shows a food web.
(i) Identify one producer shown in Fig. 4.1.
▶️Answer/Explanation
Answer: grass / dandelion (plants)
Explanation: Producers are organisms that produce their own food through photosynthesis. In the food web, grass and dandelion plants are producers as they convert sunlight into energy.
(ii) Identify one herbivore shown in Fig. 4.1.
▶️Answer/Explanation
Answer: rabbit / mouse
Explanation: Herbivores are organisms that feed on plants. In the food web, the rabbit and mouse are herbivores as they consume grass and dandelion plants.
(iii) Use information from Fig. 4.1 to complete a food chain that includes the mouse and three other organisms.
▶️Answer/Explanation
Answer: grass / dandelion plants → mouse → snake → hawk
Explanation: A food chain shows the flow of energy from one organism to another. In this case, the grass/dandelion plants are eaten by the mouse, which is then eaten by the snake, and finally, the snake is eaten by the hawk.
(b) Complete the sentences to describe why the hawk can be classed as a secondary or a tertiary consumer.
The hawk is a secondary consumer when it eats:
▶️Answer/Explanation
Answer: rabbits / mice / primary consumers
Explanation: The hawk is a secondary consumer when it eats primary consumers like rabbits or mice, which feed directly on producers.
The hawk is a tertiary consumer when it eats:
▶️Answer/Explanation
Answer: snakes / secondary consumers
Explanation: The hawk is a tertiary consumer when it eats secondary consumers like snakes, which feed on primary consumers.
(c) A disease causes a large decrease in the rabbit population. This causes a decrease in the snake population. Give two reasons why the snake population decreases.
▶️Answer/Explanation
Answer:
- As there is less food for snakes.
- Increased predation of snakes.
Explanation: The decrease in the rabbit population reduces the food supply for snakes, leading to a decline in the snake population. Additionally, with fewer rabbits, predators may turn to snakes as an alternative food source, increasing predation on snakes.
(d) State the principal source of energy for all food webs.
▶️Answer/Explanation
Answer: Sun
Explanation: The Sun is the primary source of energy for all food webs. Producers (plants) convert solar energy into chemical energy through photosynthesis, which is then passed through the food chain.