Class 12 Biology - KARNATAKA
Ecosystem
The chapter 'Ecosystem' in Class 12 Biology explores the structural and functional units of nature where living organisms interact with each other and their physical environment. It covers crucial topics such as ecosystem structure and function, productivity, decomposition, energy flow through trophic levels, ecological pyramids, and nutrient cycling (carbon and phosphorus). Additionally, it introduces ecological succession and ecosystem services. For Karnataka (KSEEB) board exams, this chapter is high-scoring, frequently featuring direct questions on ecological pyramids, energy flow percentages, and the steps of decomposition.
Start Learning FreeKey Concepts
Productivity
The rate of biomass production, divided into Gross Primary Productivity (GPP) and Net Primary Productivity (NPP) available to consumers.
Decomposition
The breakdown of complex organic matter into inorganic substances by decomposers, involving steps like fragmentation, leaching, catabolism, humification, and mineralization.
Energy Flow
The unidirectional movement of energy through trophic levels, governed by the 10% law of energy transfer.
Ecological Pyramids
Graphical representations of trophic structure and function, which can be pyramids of number, biomass, or energy.
Ecological Succession
The predictable and gradual change in species composition in a given area over time, leading to a climax community.
Important Formulas
Board Exam Info
In the Karnataka (KSEEB) Class 12 Biology board exam, the Ecosystem chapter typically carries around 5 to 7 marks. Common question types include 1-mark objective questions, 2 or 3-mark short answers explaining ecological pyramids or decomposition steps, and occasionally a 5-mark question detailing nutrient cycles like the carbon or phosphorus cycle.
Frequently Asked Questions
Can a pyramid of biomass be inverted?
Yes, in aquatic ecosystems, the pyramid of biomass is often inverted because the biomass of phytoplankton (producers) is much smaller than that of zooplankton and fish (consumers) at any given time.
What is the difference between GPP and NPP?
Gross Primary Productivity (GPP) is the total rate of biomass production during photosynthesis, while Net Primary Productivity (NPP) is the remaining biomass after accounting for plant respiration losses (NPP = GPP - R).
Why is the flow of energy in an ecosystem unidirectional?
Energy flows in a single direction because energy captured by autotrophs does not revert back to the sun, and energy lost as heat at each trophic level cannot be reused by organisms.
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