Biology · Class 12 Science
Ch 14Ecosystems and Energy Flow — Class 12 Biology, concept-first.
An ecosystem is a self-regulatory and self-sustaining structural and functional unit of nature (the biosphere), containing both biotic and abiotic components that interact continuously with one another. The term 'ecosystem' was coined by Tansley in 1935.
Key concepts
Hover a concept to preview it and jump to its most relevant Q&A.
Ecological Pyramids
An ecological pyramid is a graphic device, introduced by Charles Elton in 1927 (hence also called an Eltonian pyramid), for representing an ecosystem's trophic structure and function at each successive trophic level.
Most relevant Q&A
- Which one of the following has the largest population in a food chain? (a) Producers (b) Primary consumers (c) Secondary consumers (d) Decom…Free
- Give an example of ecosystem which shows inverted pyramid of numbers.Preview
- Give an example of ecosystem which shows inverted pyramid of biomass.Preview
- Distinguish between upright and inverted pyramid of biomassPreview
- Define ecological pyramids and describe with examples, pyramids of number and biomass.Preview
In previous exams
How often this chapter’s concepts have been examined — real appearance data, never estimated.
Chapter contents
The NCERT structure, section by section. Open a section to see its questions, then read the concept-first solution.
Ecosystem: Structure and Function
An ecosystem is a self-regulatory and self-sustaining structural and functional unit of nature (the biosphere), containing both biotic and abiotic components that interact continuously with one anothe…
Productivity
Productivity refers to the rate at which biomass is generated in an ecosystem, expressed in units of mass per unit surface area (or volume) per unit time — for instance, grams per square metre per day…
Decomposition
Decomposition is the process by which decomposers break down complex organic matter into simpler inorganic substances such as carbon dioxide, water and mineral nutrients.
Energy Flow
The sun is the only source of energy for virtually all ecosystems on Earth, with the exception of certain deep-sea ecosystems.
Ecological Pyramids
An ecological pyramid is a graphic representation of the relationship between the organisms of successive trophic levels in an ecosystem, expressed in terms of number, biomass, or energy — a concept f…
Nutrient Cycles
Nutrient cycling — also known as the biogeochemical cycle — is the movement of nutrient elements through the various components of an ecosystem.
Carbon Cycle
All life on Earth is carbon-based, since carbon is the principal component of the organic compounds that make up protoplasm, constituting roughly 49% of the dry weight of organisms.
Phosphorus Cycle
The phosphorus cycle is the cyclic movement of phosphorus through the hydrosphere, lithosphere and biosphere.
Ecological Succession
Ecological succession is the gradual and predictable change in the species composition of a given area over time — a spatial pattern that unfolds through time, with time itself being the crucial varia…
Succession of Plants
Based on the nature of the habitat in which it occurs, plant succession is termed hydrarch (or hydrosere) when it takes place in wet or wetland areas, and xerarch (or xerosere) when it takes place in…
Ecosystem Services
Healthy ecosystems form the basis for a wide range of economic, environmental and aesthetic goods and services: for instance, healthy forest ecosystems purify air and water and help mitigate droughts…
+−Exercise18 questions
- Q1Which one of the following has the largest population in a food chain? (a) Producers (b) Primary consumers (c) Secondary consumers (d) Decom…Free
- Q2The second trophic level in a lake is ________________ (a) Phytoplankton (b) Zooplankton (c) Benthos (d) FishesFree
- Q3Secondary consumers are __________ (a) Herbivores (b) Producers (c) Carnivores (d) AutotrophsFree
- Q4What is the % of photosynthetically active radiation in the incident solar radiation? (a) 100% (b) 50% (c) 1-5% (d) 2-10%Preview
- Q5Give the term used to express a community in its final stage of succession? (a) End community (b) Final community (c) Climax community (d) D…Preview
- Q6After landslide which of the following type of succession occurs? (a) Primary (b) Secondary (c) Tertiary (d) ClimaxPreview
- Q7Which of the following is most often a limiting factor of the primary productivity in any ecosystem. (a) Carbon (b) Nitrogen (c) Phosphorus…Preview
- Q8Give an example of ecosystem which shows inverted pyramid of numbers.Preview
- Q9Give an example of ecosystem which shows inverted pyramid of biomass.Preview
- Q10Which mineral acts as limiting factor for productivity in an aquatic ecosystem.Preview
- Q11Name the reservoir and sink of carbon in carbon cycle.Preview
- Q12Distinguish between upright and inverted pyramid of biomassPreview
- Q13Distinguish between Food chain and Food web.Preview
- Q14Define ecological pyramids and describe with examples, pyramids of number and biomass.Preview
- Q15What is primary productivity? Give brief description of factors that affect primary productivity.Preview
- Q16Define decomposition and describe the processes and products of decomposition.Preview
- Q17Write important features of a sedimentary cycle in an ecosystem.Preview
- Q18Discribe carbon cycle and add a note on the impact of human activities on carbon cycle.Preview
Sample & Board Papers
Sample papers and previous-year board questions for this subject.
+−Show 21 questionsHide questions21 questions
- Q1What is Humification?Preview
- Q2What is ecological succession?Preview
- Q3Explain 'Carbon cycle'.Preview
- Q4Breakdown of detritus into smaller particles is called __________. (a) fragmentation (b) leaching (c) catabolism (d) humificationPreview
- Q5What is meant by ecological succession?Preview
- Q6Give schematic representation of carbon cycle.Preview
- Q7In a food chain, the herbivores are represented by ______. (a) producers (b) primary consumers (c) secondary consumers (d) decomposersPreview
- Q8Explain energy pyramid.Preview
- Q9Give scientific reasons : (A) The pyramid of energy is always upright. (B) In an ecosystem the energy flow is always unidirectional. (C) Ozo…Preview
- Q10Among biotic components, the micro consumers are called _______.Preview
- Q11What do you mean by Pioneer species?Preview
- Q12What is ecological succession? Name various seral stages from pioneer species to climax community with suitable example in hydrarch successi…Preview
- Q13Define the terms: (a) Gross Primary Productivity (b) Net Primary ProductivityPreview
- Q14Complete the following chart regarding energy flow in an Ecosystem and re-write: ? | Herbivores Primary Producer | ? ? | Man, Lion Secondary…Preview
- Q15Which one of the following does not evolve further? (a) Climax community (b) Primary Succession (c) Pioneer Species (d) Seral CommunityPreview
- Q16Describe pyramid of energy with the help of diagram.Preview
- Q17In the given food chain, if plants absorb 1000 Joules of light energy, then how much energy is available for Lion? Plants (Producer) → Deer…Preview
- Q18What is decomposition? Give diagrammatic representation of 'decomposition cycle.'Preview
- Q19Identify the organism which meet their energy and nutrient requirements by degrading the detritus: (a) Omnivores (b) Carnivores (c) Autotrop…Preview
- Q20The producers receive 5000 Joules of light energy, then how much energy will be transferred to the carnivores (secondary consumers)?Preview
- Q21Calculate the amount of ATP required by nitrogen fixer for the formation of 1000 molecules of ammonia. Name the specialised cell of cyanobac…Preview