31 Years NEET Previous Year Questions: Ecosystem - 3 - SSS 3 MCQ

Pyramid of numbers in a g rassland ecosystem is always upright. For most ecosystem, like grass and ecosystem. Pyramids of numbers are upright because numbering of organisms decrease at successively higher trophic levels. Trophic level refers to the organisms, position in the food chain.

Detritus food chain being with dead organic matter with dead plant parts, animals and their excretory product which is being acted upon by decomposers such as saprophytes to obtain energy needed for their survival.

Phytoplankton → zooplankton → Fish. This is a type of food chain in aquatic ecosystem. 

Pyramid of  number represents the number of individuals on each tropic level.

Energ y pyramid can not be inver ted because energy always flows in one direction only. According to 10% law of energy transfer given by Lindemann (1972), during transfer of energy from one trophic level to other there is always loss in respiration and other activities only 10% of energy is transfered to neat trophic level. So the amount of energy flow decreases with successive trophic levels.

According to 10% law of Lindemann,if 1 tonne (1000kg) biomass is present in the grass, only 10% of it means 100 kg will go into deer and in tiger, the biomass will be only 10kg, i.g. 10% of deer' biomass.

First tropic level in a lake is phytoplankton, second is zooplankton.

The decomposers act on the dead organic matter and break them down into simpler compounds and minerals.

In a biotic community the herbivores (goat, deer) are those animals, which consume the primary producers (green plants). Hence they are primary consumers.

Biogeochemical cycles : Two types :
(a) Gaseous : Biogenetic materials involved in circulation are gases eg. N₂, O₂, CO₂ etc.
(b) Sedimentary : Biogenetic materials involved in circulation are non-gaseous eg. P₂, Ca, S etc. forms rocks.