Ecology Practice Questions
IB (International Baccalaureate) · IB Biology HL · 150 free MCQs with instant results and detailed explanations.
150
Total
49
Easy
78
Medium
23
Hard
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Sample Questions from Ecology
Here are 10 sample questions. Start a quiz to get randomized questions with scoring.
Q1
Easy
Which of the following best defines 'ecology'?
A.
The study of the relationships between organisms and their environment.
B.
The study of the physical and chemical processes of the earth.
C.
The study of the genetic variation within species.
D.
The study of the behavior of individual organisms.
Show Answer & Explanation
Correct Answer: A
'Ecology' specifically focuses on how organisms interact with each other and with their environment, making option A the correct definition.
Q2
Easy
In a simple food chain, which of the following represents the correct flow of energy?
A.
Producer → Primary Consumer → Secondary Consumer
B.
Secondary Consumer → Producer → Primary Consumer
C.
Primary Consumer → Secondary Consumer → Producer
D.
Producer → Secondary Consumer → Primary Consumer
Show Answer & Explanation
Correct Answer: A
Energy flows from producers to primary consumers and then to secondary consumers, making option A the correct sequence.
Q3
Easy
Which of the following biomes is characterized by low temperatures and permafrost?
A.
Tropical rainforest
B.
Desert
C.
Tundra
D.
Savanna
Show Answer & Explanation
Correct Answer: C
The tundra biome is known for its cold temperatures and presence of permafrost, which distinguishes it from the other biomes listed.
Q4
Medium
Which of the following best describes the term 'trophic level'?
A.
A position in a food web representing a specific energy transfer.
B.
The total biomass of organisms in a given area.
C.
The reproductive rate of a species in an ecosystem.
D.
The diversity of species in a community.
Show Answer & Explanation
Correct Answer: A
A trophic level defines the position of an organism in a food web, indicating its role in energy transfer within an ecosystem.
Q5
Medium
In a certain ecosystem, the primary productivity is measured to be 3000 grams of carbon per square meter per year. If the efficiency of energy transfer between trophic levels is approximately 10%, what would be the secondary productivity for the primary consumers?
A.
300 grams per square meter per year
B.
3000 grams per square meter per year
C.
30000 grams per square meter per year
D.
30 grams per square meter per year
Show Answer & Explanation
Correct Answer: A
Secondary productivity can be calculated by taking 10% of the primary productivity (3000g), which results in 300g/m²/year for primary consumers.
Q6
Medium
Which of the following factors is most likely to increase species diversity in an ecosystem?
A.
Increased habitat fragmentation
B.
Introduction of invasive species
C.
Ecological succession
D.
Climate change
Show Answer & Explanation
Correct Answer: C
Ecological succession typically leads to increased species diversity as new niches are created and resources are utilized more effectively over time.
Q7
Medium
What is the role of decomposers in an ecosystem?
A.
To produce energy through photosynthesis.
B.
To break down organic material and recycle nutrients.
C.
To compete with primary producers for resources.
D.
To provide habitat for other organisms.
Show Answer & Explanation
Correct Answer: B
Decomposers break down dead organic material, which recycles nutrients back into the ecosystem, allowing for continued growth of primary producers.
Q8
Hard
Which of the following best describes the concept of carrying capacity in an ecosystem?
A.
The maximum population size that an environment can sustain indefinitely without being degraded.
B.
The total number of species that can coexist in an ecosystem.
C.
The rate at which renewable resources are replenished in an ecosystem.
D.
The minimum population size required for a species to maintain genetic diversity.
Show Answer & Explanation
Correct Answer: A
Carrying capacity refers to the largest number of individuals of a particular species that an environment can support sustainably over time. This concept highlights the limits of resources and space, distinguishing it from other options that do not accurately define the concept.
Q9
Hard
In a food web, if a decrease in the population of a top predator occurs, what is the most likely outcome for the populations of primary and secondary consumers?
A.
The populations of primary consumers will decrease, while secondary consumers will increase.
B.
The populations of primary consumers will increase, while secondary consumers will decrease.
C.
Both primary and secondary consumers will experience no change.
D.
The populations of primary consumers will increase, and secondary consumers will also increase.
Show Answer & Explanation
Correct Answer: D
A decrease in the population of a top predator typically allows for an increase in the population of primary consumers due to reduced predation. This increase in primary consumers can then lead to an increase in secondary consumers who have more food resources available, thereby influencing the entire food web positively.
Q10
Hard
In an ecosystem, which of the following biogeochemical cycles involves the conversion of nitrogen gas into ammonia by bacteria?
A.
Carbon Cycle
B.
Phosphorus Cycle
C.
Nitrogen Cycle
D.
Sulfur Cycle
Show Answer & Explanation
Correct Answer: C
The nitrogen cycle specifically describes the conversion of nitrogen gas (N2) into ammonia (NH3) by nitrogen-fixing bacteria, making option C the correct answer.
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Ecology — IB (International Baccalaureate) IB Biology HL Practice Questions Online
This page contains 150 practice MCQs for the chapter Ecology in IB (International Baccalaureate) IB Biology HL. The questions are organized by difficulty — 49 easy, 78 medium, 23 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.