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Biology for IGCSE & O level - Organisms And Their Environment (Section 1)

1
Which group of organisms is responsible for breaking down dead plants and animals, returning nutrients to the soil?
Answer
(C)
Decomposers
2
What is the ultimate source of energy for most ecosystems?
Answer
(C)
Sunlight
3
What is the role of fertilizers in the nitrogen cycle?
Answer
(D)
To increase the amount of nitrogen in the soil.
4
What is a secondary consumer?
Answer
(B)
An animal that eats primary consumers.
5
What is the process that converts atmospheric nitrogen into a usable form for plants?
Answer
(D)
Nitrogen fixation
6
Which organisms are responsible for converting ammonia into nitrite and then to nitrate?
Answer
(B)
Nitrifying Bacteria
7
Which of the following is a primary producer?
Answer
(B)
A tree
8
What is the role of plants in the carbon cycle?
Answer
(B)
They absorb carbon dioxide through photosynthesis.
9
Which of the following organisms are most likely to be at the base of a food chain or web?
Answer
(C)
Producers
10
Which of the following processes are involved in the carbon cycle?
Answer
A
B
C
11
What is the role of the waste of animals or dead organisms in the nitrogen cycle?
Answer
(D)
All of the above.
12
Which organisms are involved in the process of ammonification?
Answer
(C)
Bacteria and fungi
13
In the context of energy flow, what do arrows in a food web represent?
Answer
(B)
The direction of energy transfer
14
What is a 'food web'?
Answer
(C)
A network of interconnected food chains.
15
What best describes the role of bacteria in the nitrogen cycle?
Answer
A
B
C
16
What term is used to describe the total mass of living organisms in a trophic level?
Answer
(A)
Biomass
17
Which of the following best describes the flow of energy in a food web?
Answer
(A)
One-directional, from producers to consumers.
18
What is the primary role of producers in an ecosystem?
Answer
(B)
To convert light energy into chemical energy.
19
What is the most efficient way for humans to increase the amount of energy available to them from an ecosystem?
Answer
(B)
Eating only primary consumers
20
What is the main source of energy for photosynthesis?
Answer
(B)
Sunlight
21
Which of these compounds does a plant absorb to create its own food?
Answer
(A)
Carbon dioxide
22
What process turns nitrates into nitrogen gas?
Answer
(B)
Denitrification
23
What is the process by which plants create their own food using sunlight?
Answer
(B)
Photosynthesis
24
What is the primary function of producers in an ecosystem?
Answer
(C)
To convert sunlight into energy
25
What happens to the energy after an organism dies in an ecosystem?
Answer
(B)
It is lost as heat during decomposition.
26
What type of organisms create their own food through photosynthesis?
Answer
(C)
Producers
27
What type of organism is at the highest trophic level in a food chain?
Answer
(D)
Apex predators
28
What is the name of the process where plants use light energy to make food?
Answer
(B)
Photosynthesis
29
What type of organisms are carnivores?
Answer
(A)
Organisms that eat other animals.
30
Where does the energy flow in a food web begin?
Answer
(C)
Producers
31
How is energy lost in a food chain?
Answer
(D)
All of the above
32
In what form is nitrogen primarily found in the atmosphere?
Answer
(C)
Nitrogen gas (N2)
33
Which organisms are the producers?
Answer
(B)
Organisms that make their own food from sunlight.
34
What does the term 'trophic level' refer to in an ecosystem?
Answer
(B)
The position an organism occupies in a food chain
35
What is the source of energy for most food chains?
Answer
(B)
Sunlight
36
What are the characteristics of a food chain?
Answer
A
B
D
37
Which of the following is a major reservoir of carbon in the carbon cycle?
Answer
(D)
All of the above
38
What is the primary source of energy for most ecosystems?
Answer
(C)
Sunlight
39
What is the name of the process where a plant converts sunlight into energy?
Answer
(B)
Photosynthesis
40
Which organisms eat the producers in a food chain?
Answer
(A)
Primary consumers
41
What are the main processes in the nitrogen cycle?
Answer
A
B
D
42
What is a 'food chain' in the context of an ecosystem?
Answer
(B)
A series of organisms, each eating the one before it.
43
Which of the following processes releases carbon dioxide into the atmosphere?
Answer
B
C
44
Which cycle involves the movement of carbon between the atmosphere, land, and water?
Answer
(C)
The carbon cycle
45
What is a pyramid of numbers used to show?
Answer
(B)
The number of organisms at each trophic level
46
Why are pyramids of biomass often more useful than pyramids of numbers?
Answer
(A)
They indicate the mass of living material at each trophic level.
47
What are the main functions of decomposers in an ecosystem?
Answer
A
B
48
Which of the following are examples of fossil fuels?
Answer
A
B
C
49
In what form is carbon primarily stored in the atmosphere?
Answer
(B)
Carbon dioxide (CO2)
50
In a pyramid of numbers, what might cause the pyramid to have an inverted shape (be wider at the top than the bottom)?
Answer
(B)
Many small producers support a few large consumers.