Organisms and their Environment
Each subtopic includes About section, revision page link, 10 preview questions, and practice CTAs.
Energy flow and food webs
SubtopicEnergy flow and food webs under Organisms and their Environment for Grade 11 IGCSE.
Preview questions (no answers)
- 1.
If an organism is described as an 'autotroph', what can it do?
A.It eats other organisms
B.It makes its own food
C.It only lives in water
D.It decomposes wood
- 2.
What does a pyramid of energy show that a pyramid of numbers might not?
A.The actual flow of energy over time
B.The size of the organisms
C.The color of the organisms
D.The number of predators
- 3.
A food chain is: Phytoplankton Zooplankton Small fish Shark. What is the shark?
A.Producer
B.Primary consumer
C.Secondary consumer
D.Tertiary consumer
- 4.
What happens to the energy that an organism uses for muscle contraction?
A.It is recycled into the food chain
B.It is lost to the surroundings as heat
C.It is stored as fat
D.It is returned to the sun
- 5.
If of energy is lost as heat and waste at each level, how much energy would be transferred to the next level?
A.B.C.D. - 6.
What does a 'primary consumer' eat?
A.Other consumers
B.Decomposers
C.Producers
D.Apex predators
- 7.
Which organism is both a secondary and a tertiary consumer in this web?
A.Organism A
B.Organism D
C.Organism E
D.Organism C
- 8.
Which statement correctly identifies a difference between a food chain and a food web?
A.Food chains include decomposers while food webs do not.
B.Food webs show multiple feeding relationships, reflecting a more complex and realistic ecosystem structure.
C.Energy flow is only one-way in a food chain but moves in circles in a food web.
D.Food chains always start with a consumer, whereas food webs start with a producer.
- 9.
In a pyramid of energy, the width of each bar represents:
A.The total number of individuals at that level.
B.The total dry mass of all organisms at that level.
C.The amount of energy per unit area per unit time at that level.
D.The speed at which energy is moving through the level.
- 10.
Which of the following is the most significant reason for the decrease in biomass at higher trophic levels in a stable terrestrial ecosystem?
A.High rates of immigration and emigration.
B.Cumulative energy loss due to metabolic processes at each level.
C.Lower reproductive rates of top predators.
D.Increased concentration of toxins in higher consumers.
Download the worksheet for Organisms and their Environment - Energy flow and food webs to practice offline. It includes additional chapter-level practice questions.
Nutrient cycles (Carbon and Nitrogen)
SubtopicNutrient cycles (Carbon and Nitrogen) under Organisms and their Environment for Grade 11 IGCSE.
Preview questions (no answers)
- 1.
Which form of nitrogen is found in DNA and proteins?
A.Nitrogen gas
B.Organic nitrogen
C.Nitrite ions
D.Nitrate ions
- 2.
In the carbon cycle, which of these is an example of 'combustion'?
A.A tree growing leaves
B.An animal running
C.Burning wood in a fireplace
D.Bacteria breaking down a leaf
- 3.
What role do fungi play when they grow on a fallen log?
A.Producers
B.Decomposers
C.Nitrogen fixers
D.Carnivores
- 4.
Which gas is released during the process of denitrification?
A.B.C.D. - 5.
How do lightning and nitrogen-fixing bacteria differ in their role in the nitrogen cycle?
A.Lightning produces ammonia, while bacteria produce nitrates
B.Lightning is a physical process, while bacteria perform a biological process
C.Lightning removes nitrogen from the soil, while bacteria add it
D.Lightning only occurs in the ocean, while bacteria only live on land
- 6.
Which of the following elements is found in proteins but NOT in most common carbohydrates or lipids?
A.Carbon
B.Hydrogen
C.Oxygen
D.Nitrogen
- 7.
In the carbon cycle, which process takes the longest time to complete?
A.Movement of carbon from producers to consumers
B.Release of by respiration
C.Formation of fossil fuels from dead organic matter
D.Uptake of by a leaf
- 8.
How do 'Cover Crops' like clover help manage the nitrogen cycle in sustainable farming?
A.They absorb all the nitrogen to prevent weeds from growing.
B.They have symbiotic Rhizobium that fix , which is then released into the soil when the clover is plowed back in.
C.They reflect sunlight to keep the soil cool for nitrifying bacteria.
D.They release oxygen into the soil to promote denitrification.
- 9.
What is the primary carbon source for 'Chemoautotrophic' nitrifying bacteria?
A.Organic glucose from plant roots.
B.Inorganic dissolved in the soil water.
C.Methane gas from decomposition.
D.Carbonate minerals in rocks.
- 10.
In the nitrogen cycle, which transition is specifically an 'oxidation' reaction?
A.Nitrite to Nitrate ( to )
B.Nitrate to Nitrogen gas ( to )
C.Nitrogen gas to Ammonia ( to )
D.Protein to Amino Acids
Download the worksheet for Organisms and their Environment - Nutrient cycles (Carbon and Nitrogen) to practice offline. It includes additional chapter-level practice questions.
Population size
SubtopicPopulation size under Organisms and their Environment for Grade 11 IGCSE.
Preview questions (no answers)
- 1.
Which of the following describes a population in the stationary phase?
A.The number of deaths is zero
B.The number of births is zero
C.The number of deaths equals the number of births
D.The population is doubling every hour
- 2.
What does a sigmoid growth curve represent?
A.The growth of a population over time in an environment with limited resources
B.The infinite growth of a population
C.A population that is going extinct
D.The growth of a population with no lag phase
- 3.
Which of the following is a result of improved agriculture on human population growth?
A.Decreased food security
B.Increased death rate
C.Increased food availability leading to population growth
D.Higher rate of emigration
- 4.
How does a decrease in birth rate and an increase in death rate affect the overall population growth?
A.The population grows faster
B.The population size will likely decline
C.The population size remains unchanged
D.The population enters the log phase
- 5.
What is the primary factor that determines the width of the base of a human population pyramid?
A.The death rate of the elderly
B.The number of people emigrating
C.The birth rate and number of children in the population
D.The average age of retirement
- 6.
Which of these is a likely effect of overfishing on a specific fish population in the North Sea?
A.The fish population will enter the log phase of growth
B.The population size will drop below the level required for recovery
C.The fish will evolve to breathe air and move to land
D.The carrying capacity of the North Sea will increase
- 7.
What happens to the death rate of a population during the transition from the log phase to the stationary phase?
A.It decreases until it reaches zero
B.It remains constant while the birth rate increases
C.It increases until it equals the birth rate
D.It becomes significantly lower than the birth rate
- 8.
When a population is at the 'Stationary Phase', which of the following is true about the environmental resistance?
A.Environmental resistance is zero.
B.Environmental resistance is at its maximum and balances the biotic potential.
C.Environmental resistance is lower than the birth rate.
D.Environmental resistance has been overcome by the species' adaptations.
- 9.
Which of these factors is a biotic limiting factor?
A.The concentration of sulfur dioxide in the atmosphere.
B.The intensity of sunlight reaching the forest floor.
C.The presence of a pathogenic bacterium in the water supply.
D.The pH of the soil in a grassland.
- 10.
A population of algae in a pond experiences 'Eutrophication' (an influx of nitrates). What is the most likely immediate effect on the population size?
A.The population will immediately enter the death phase.
B.The population will undergo a rapid log phase of growth.
C.The carrying capacity of the pond will decrease due to less nitrogen.
D.The algae will stop photosynthesizing and switch to respiration.
Download the worksheet for Organisms and their Environment - Population size to practice offline. It includes additional chapter-level practice questions.