Ecosystem

33 solved questions from Class 12 Biology, each with the full working. Tap any question to see the step-by-step solution.

• 1 What is the primary topic or theoretical principle explored in 'Ecosystem' (Class 12 BIOLOGY)? medium MCQ Chapter Core Principle
• 2 Which key mechanism or analytical rule is highlighted in 'Ecosystem'? medium MCQ Key Analytical Mechanism
• 3 What is the primary topic or principle explained in 'Ecosystem' (Class 12 Biology)? medium MCQ Chapter Core Concept
• 4 Which key observation or fact is central to understanding 'Ecosystem'? medium MCQ Key Fact & Mechanism
• 5 Why is the study of 'Ecosystem' important for students of Class 12? medium MCQ Learning Significance
• 6 What is a common application or real-world example related to 'Ecosystem'? medium MCQ Real World Application
• 7 What key takeaway should students retain after completing 'Ecosystem'? medium MCQ Chapter Summary & Takeaway
• 8 Which statement best describes the primary productivity in a tropical rainforest compared to a temperate forest? medium MCQ 2 marks Primary productivity differences
• 9 In a grassland ecosystem, the Gross Primary Production (GPP) is 4000 kJ m⁻² d⁻¹. The energy transfer efficiency from producers to herbivores is 10 % and from herbivores to carnivores is 12 %. Calculate the overall efficiency (in percent) of energy transfer from primary producers to carnivores. hard 3 marks Energy transfer efficiency
• 10 A food web of a freshwater ecosystem consists of 3 producers, 2 primary consumers, 2 secondary consumers and 1 tertiary consumer. How many trophic levels are present in this food web? easy 1 mark Trophic levels in a food web
• 11 Explain how clear‑cut deforestation in a mixed forest ecosystem affects the nitrogen cycle, from nitrogen fixation to plant uptake. Provide at least three specific consequences. hard 5 marks Human impact on biogeochemical cycles
• 12 In a temperate forest, net primary production is 8000 kJ m^-2d^-1. The energy transfer efficiency from producers to primary consumers is 15\% and from primary consumers to secondary consumers is 10\%. Calculate the energy available to secondary consumers per square metre per day. medium 2 marks energy transfer efficiency
• 13 Discuss how the use of synthetic nitrogen fertilizers in an agricultural ecosystem can alter the nitrogen cycle. In your answer, describe at least three specific processes that are affected and the ecological consequences of each. hard 5 marks fertilizer impact on nitrogen cycle
• 14 In a coastal mangrove ecosystem, which organism is most likely to be considered a keystone species because its removal would cause a dramatic shift in community structure? medium MCQ 2 marks keystone species identification
• 15 Which of the following is an abiotic factor in a desert ecosystem? easy MCQ 1 mark abiotic vs biotic factors
• 16 A freshwater lake food web consists of 1 species of phytoplankton (producer), 2 species of zooplankton (primary consumers), 2 species of small fish (secondary consumers) and 1 species of larger predatory fish (tertiary consumer). How many trophic levels are present in this food web? Also, name a keystone species that, if removed, could cause a major shift in this lake ecosystem. medium 2 marks Trophic levels and keystone species
• 17 In a subtropical grassland, the Gross Primary Production (GPP) is 5000 kJ m⁻² d⁻¹. The energy transfer efficiency from producers to primary consumers is 12 % and from primary consumers to secondary consumers is 8 %. Calculate the amount of energy (in kJ m⁻² d⁻¹) available to secondary consumers. medium 2 marks Energy transfer efficiency calculation
• 18 Which of the following is an abiotic component of a tropical rainforest ecosystem? easy MCQ 1 mark Identify abiotic factor
• 19 In a temperate grassland the Gross Primary Production (GPP) is 6000 kJ m^-2d^-1 and the ecosystem respiration is 2000 kJ m^-2d^-1. Energy transfer efficiency from producers to primary consumers is 10% and from primary consumers to secondary consumers is 7%. Calculate the amount of energy (in kJ m^-2d^-1) available to secondary consumers. medium 3 marks Energy flow and ecological efficiency
• 20 Explain how overgrazing in a grassland ecosystem can lead to desertification. Mention at least three ecological processes involved and their consequences. medium 4 marks Impact of overgrazing and desertification
• 21 In a marine estuary the recorded energy contents are: phytoplankton 8000 kJ m^-2, zooplankton 600 kJ m^-2, small fish 120 kJ m^-2, large fish 24 kJ m^-2. (a) Calculate the overall ecological efficiency from phytoplankton to large fish as a percentage. (b) State whether this overall efficiency follows the typical 10% rule. hard 5 marks Ecological pyramids and energy efficiency
• 22 Consider a coral reef ecosystem where the Gross Primary Production is 8000 kJ,m^-2day^-1. The energy transfer efficiencies are 12% from producers to primary consumers, 8% from primary to secondary, and 5% from secondary to tertiary. (a) Calculate the total energy available to tertiary consumers per square metre per day. (b) Discuss the ecological significance of this low efficiency at higher trophic levels, mentioning at least two consequences for the reef biodiversity. hard 5 marks Energy transfer efficiency and ecosystem stability
• 23 In a freshwater marsh, the Gross Primary Production is 3000 kJ,m^-2day^-1. The ecological efficiency from producers to primary consumers is 9% and from primary consumers to secondary consumers is 7%. How much energy per square metre per day is available to secondary consumers? easy 1 mark Energy transfer in food chains
• 24 GPP of a temperate grassland is 7000 kJ,m^-2d^-1 and ecosystem respiration is 2500 kJ,m^-2d^-1. Energy transfer efficiencies are 10% from producers to primary consumers and 8% from primary to secondary consumers. What is the energy available to secondary consumers per square metre per day? easy 1 mark Energy flow through trophic levels
• 25 Which of the following is an abiotic component of a tropical rainforest ecosystem? medium MCQ 2 marks Abiotic versus biotic components
• 26 A mangrove ecosystem has GPP of 9000 kJ,m^-2d^-1 and ecosystem respiration of 3500 kJ,m^-2d^-1. The energy transfer efficiencies are: 15% from producers to primary consumers, 10% from primary to secondary consumers, and 5% from secondary to tertiary consumers. Calculate the total energy available to tertiary consumers per square metre per day, accounting for respiration losses before each transfer. hard 5 marks Energy flow with respiration losses
• 27 Consider a freshwater lake food web consisting of (i) phytoplankton as producers, (ii) zooplankton as primary consumers, (iii) small fish as secondary consumers, and (iv) large predatory fish as tertiary consumers. Suppose an invasive predator, the Nile perch, is introduced and starts preying heavily on the small fish. Describe in detail how this introduction could alter the structure and functioning of the lake ecosystem. Discuss at least three cascading effects on energy flow, nutrient cycling, and biodiversity, and explain the mechanisms behind each. hard 4 marks Trophic cascade and invasive species
• 28 A freshwater marsh has a Gross Primary Production (GPP) of 5000 kJ m^-2d^-1 and ecosystem respiration of 2000 kJ m^-2d^-1. The energy transfer efficiencies are 12% from producers to primary consumers, 8% from primary to secondary consumers and 5% from secondary to tertiary consumers. Calculate the total energy available to tertiary consumers per square metre per day, accounting for respiration losses before each transfer. medium 3 marks Energy flow calculation
• 29 In a forest food web there are three trophic levels: producers, herbivores and carnivores. If the total biomass of producers is 2000 g m^-2 and the average ecological efficiency between successive levels is 10%, calculate the biomass of carnivores per square metre. medium 2 marks Biomass transfer efficiency
• 30 Which of the following is an abiotic component of a desert ecosystem? easy MCQ 1 mark Abiotic component identification
• 31 Which of the following is an abiotic component of a tropical rainforest ecosystem? medium MCQ 2 marks Abiotic component identification
• 32 A temperate marsh records Gross Primary Production of 8500 kJ m^-2 d^-1 and ecosystem respiration of 2500 kJ m^-2 d^-1. Calculate the Net Primary Production (NPP) per square metre per day. easy 1 mark Primary production, Net Primary Production
• 33 Which of the following is an abiotic component of a temperate forest ecosystem? medium MCQ 1 mark Abiotic components of ecosystems