Ecosystem logoSubject: Biology    Exam: AIPMT / NEET-UG

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Important Points

Xerophytes have a very low area/volume ratio of their body, a very high root /shoot ratio, highly developed xylem and sclerenchyma in general. They have a thick cuticle, stomata either sunken or present in pits/crypts as in Nerium, and commonly possess a multiple epidermis . Most adapted xerophytes like cacti and succulents even possess nocturnally opening (scotoactive) stomata.
Notable dates with reference to environment are : February 2 (World Wetlands Day) , March 21 (World Forestry Day), April 22 (Earth Day) , June 5 (World Environment Day), July 6 (Vanmahotsav), July 11 (World Population Day), October 1 to 7 (Wildlife week), November 1 (World Ecology Day) , and December 3 (World Conservation Day).
Certain pesticides like chlorinated hydrocarbons (=Organochloring) such as DDT and BHC are biologically non-degradable. Being fat-assimilable , these pestides keep accumulating in the body after they have come in the food chain as residues from surface application of pesticides on the crop plants. Amount of accumulated pesticide per unit body weight keeps increasing up the food chain, and this phenomenon is called biomagnification or biological amplification .
Hydrophytes have a very high area/volume ratio of their bodies. They have extreme reduction of xylem and sclerenchyma. Their root/shoot ratio is also very low. Submerged hydrophytes lack stomata (apostomatic). Non-anchored hydrophytes like Ceratophyllum, Myriophyllum and Ulticularia may be root less.
The biomass of producers represents primary productivity and is called standing crop. Biomass of consumers represents secondary productivity in an ecosystem.
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