Ecosystem for NEET UG
An ecosystem is a community of living things plus its physical surroundings, linked by the flow of energy and the cycling of nutrients. Learn productivity, food chains, the 10% law and ecological pyramids.
BiologyClass 1274 MCQs2 lessons14 flashcards4 memory tricks
What you'll learn
- Productivity and energy flow
Define primary productivity and apply the 10% law along a food chain. - Ecological pyramids, decomposition and succession
Draw pyramids of number, biomass and energy, and describe decomposition and succession.
Key formulas
| Net primary productivity | NPP = GPP − R (respiration losses) |
|---|---|
| Lindeman's 10% law | About 10% of energy passes from one trophic level to the next |
Memory tricks
About 10% of energy passes from one trophic level to the next (Lindeman). That's why food chains rarely have more than 4–5 links.
Fragmentation, Leaching, Catabolism, Humification, Mineralisation.
Pyramid of energy is always upright. Biomass is inverted in the sea (small phytoplankton biomass). Numbers is inverted for one tree carrying many insects.
Pioneer species: lichens on rock, phytoplankton in water. The final stable community is the climax community, often a forest.
Try 3 NEET-style questions
Q1. Biomass of a species in an ecosystem is measured as
- dry weight, which is more accurate than fresh weight
- fresh weight only
- volume
- number of individuals
Show answer
Answer: (1) dry weight, which is more accurate than fresh weight
Biomass is measured as fresh or dry weight. Dry weight is more accurate because water content varies.
Q2. Secondary productivity is defined as
- the rate of photosynthesis carried out by producers
- the total biomass of all decomposers present
- the energy lost as heat at each trophic level
- the rate of formation of new organic matter by consumers
Show answer
Answer: (4) the rate of formation of new organic matter by consumers
Secondary productivity is the rate of formation of new organic matter by consumers.
Q3. Which of the following is an exception to the rule that the sun is the only source of energy for ecosystems on Earth?
- Tropical rainforests
- Grasslands
- Deep-sea hydrothermal ecosystems
- Freshwater ponds
Show answer
Answer: (3) Deep-sea hydrothermal ecosystems
Except for deep-sea hydrothermal ecosystems, the sun is the only source of energy for all ecosystems on Earth.
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