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Largest Zone of the Lake Is? 1 11 ÷ªÙÞœüŒî¦ô¢Ù 4 íƇvñ÷J 2020 email: [email protected] Ecology and Environment 8 Marks Question Largest zone of the Lake is? 1. Describe lake as an ecosystem giving H Still deeper are the submerged plants such examples for the various zones and the 4 Marks Questions as Limmetic biotic components in it? ⎯→ Hydrilla Zone 1. What is summer stratification? Explain. A. Lake eco system: To understand the funda- ⎯→ Chara Littoral A: During summer in temperature lakes, the ⏐ Zone mentals of an aquatic ecosystem, let us take density of the surface water decreases ⎯→ Potamogeton a 'lake' as an example. This is fairly a self- H because of increase in its temperature sustainable unit and rather a simple exam- The free bloating vegetation includes ° ⎯→ (21-25 C). This ‘upper more warm water ple that explains even the complex interac- Pistia layer’ of a lake is called epilimnion. ⎯→ tions that exists in an aquatic ecosystem. Wolffia Profundal Below the epilimnion there is a zone in Lake Ecosystem Zone Lakes are large inland water bodies con- ⎯→ Lemna (duck weed) which the temperature decreases at the taining standing/ still water. They are deeper ⏐⎯→ Azolla rate of 1°C per meter in depth and it is than ponds (pond is not an ideal example as it ⎯→ Eclihornia Target-2020 called thermocline / metalimnion. The is very shallow). Most lakes contain water H The phytoplankton of the littoral zone bottom layer is the hypolimnion where throughout the year. In deep lakes, light can- → cosinodisus Junior Inter water is relatively cool. Stagnant and not penetrate more than 200 meters, in depth. with low O content (due to absence of composed of → Diatoms→ 100 2 They are vertically stratified in relation to light ⏐ photosynthetic activity). → Nitzschia Zoology intensity, temperature, pressure etc. 100 ⏐ →Volvox Epilimnion Deep water lakes contain 3 distinct zones → Green algae→⏐ H → Spirogyra The limnetic zone has autotrophs photo- (21°C to 25°C) namely littoral zone, limnectic zone and pro- synthetic plants →Euglena Thermocline (21°C) foundal zone. ⏐ → → Euglenoids→⏐ Euglenoids ° →Phacus Hypolimnion (9 C) 1. Littoral zone: It is the shallow part of the → Diatoms lake closer to the shore. Light penetrates up →Gymnodinium ⏐ → Cyanobacteria During autumn (also called fall), the epil- to the bottom. It is 'euphotic' (having good → Dioflag→ ⏐ imnion cools down and the surface water light), has rich vegetation and higher rate of ellates →Cystodinium → Dinoflagellates becomes heavy when the temperature is 4°C photosynthesis, hence rich in Oxygen. H → Green algae Animals, the consumers of the littoral zone, and sinks to the bottom of the lake. Overturns 2. Limnetic zone: It is open water zone away one abundant in this zone of the lake The consumers of the limmetic zone are bring about ‘uniform temperature’ in lakes from the shore. It extends upto the effective the zooplanktons during that period. This circulation during the light penetration level, vertically. The imag- → Zooplanton → Waterfleas → Daphnia, → Copepods autumn is known as the fall/ autumn. The inary line that separates the limnetic zone rotifers, Ostracods upper O rich water reaches the hypolimnion → Neuston (Air-water, interface) → Fishes 2 from the profundal zone is known as zone and the nutrient rich bottom water comes to of compensation/ compensation point/ light → Frogs the surface. Thus there is uniform distribution compensation level. It is the zone of effec- → Epineuston/ Supraneuston → Water snakes of nutrients and O2 in the lake. tive light penetration. Here, the rate of pho- → Hyponeuston/ Infraneustion Bota of the profundal zone: It includes the 2. What are the deleterious effects of deple- tosynthesis is equal to the rate of respira- ↓ organisms such as decomposers tion of ozone in the stratosphere? tion. Limnetic zone has no contact with the ← Larvae of Water sptrider/ A: The depletion of ozone is particularly bottom of the lake. → Bacteria mosqitoes Gerris marked over the Antarctic region. This Beetles ← → Chironomid larva has resulted in the formation of a large Water bugs/ Dineutes ← Writer → Chavobonus/ Phanfom larva area of thinned ozone larger, commonly called as the ''Ozone hole''. Dr. G. Venkat Reddy H The animals nectors such as (swimming) → Red amelids UV radiation with wavelengths shorter than → Clams etc that are capable of living in low Subject Expert → Fishes that of UV-B, are almost completely absorbed O2 levels. by earth's atmosphere, provided that the 3. Profundal Zone: It is the deep water area → Amphibians The decomposers of this zone decompose ozone layer is intact. But UV-B damages present below the limnetic zone and beyond → Water snakes the dead plants and animals and release DNA and may induce mutations. It causes the depth of effective light penetration.LIght → Terrapins nutrients which are used by the biotic commu- ageing of skin, damage to skin cells and var- is absent. Photosynthetic organisms are → nities of both littoral and limnetic zones. ious types of skin cancers. In human eye, absent and so the water is poor in oxygen insects (water scorpion/ Ranatra) cornea absorbs UV-B radiation and a high content. It includes mostly the anaerobic → Back swimmer -Notonecta The lake ecosystem performs all the func- tions of any ecosystem and of the biosphere dose of UV-B causes inflammation of cornea, organisms which feed on detritus. → Diving beetles -Dytiscus as a whole i.e.conversion of inorganic sub- called snow blindness, cataract etc. Such The Organisms giving in lentic habitat are stances into organic material with the help of exposure permanently damage the cornea. classified into pedonic forms, which live at H The animals periphytons such as the radiant solar energy by the autotrophs, 3. How do marine animals adopt to hyper- the bottom of the lake and those living in → consumption of the autotrophs by the het- tonic sea water? the open water of lakes, away from the Water snails erotrophs decomposition and minerlization of A: Sea water is high in salt content com- shore vegetation are known as limnetic → Nymphs of insects the matter to release the back for reuse by the pared to that of the body fluids. So, the forms. → Dryozoans autotrophs (recycling of mineral) marine animals continuously tend to lose Biota (animal and plant life of a → Turbellarians water from their bodies by exosmosis and particular region) of the littoral → Hydra Periplanta americana face the problem of dehydration. To over- l Draw a labelled diagram of ommatidium? come the problem of water loss, marine zone fishes have glomegular kidneys with less H They are attached to/ creeping on the (4M) number of nephrons. Such Kidneys mini- Littoral zone is rich with pedonic flora (espe- aquatic plants. Cornea cially upto the depth of the effective light pen- Crystalline cone mize the loss of water through urine. To etration). At the shore proper 'emergent vege- → Red annelids Corneagen compensate water loss the marine fish drink cells tation' is abundant with firmly fixed roots in the → Chironomid larvae Cone cell more water and along with this water, salts are added to the body fluids and disturb the bottom of the lake and shoots and leaves are → Cray fishes exposed above the level of water. These are Cone Iris pigment sheath internal equilibrium. To maintain salt bal- → Some isopods ance (salt homeostasis) in the body, they amphibian plants. Certain emergent rooted Retinal pigment sheath pants of littoral zone are the → Amphipods have salt secreting chloride cells in their ⎯→ gills. Marine birds like sea gulls and pen- cattails (Typha) → Clams guins eliminate salts in the form of salty ⎯→ bulrushes (Scirpus) ⏐ heat drips through their nostrils. In turtles ⎯→ arrowheads (Sagittaria) The animals that rest on/ move on the bot- Rhabdome the ducts of chloride secreting glands open H tom of the lake constitute the benthos. slightly deeper are the rooted plants with Retinular Cell near the eyes. Some cartilaginous fishes floating leaves, such as the Biota of the limmetic zone: It is the largest retain urea and Tri Methyleamine Oxide ⎯→ Water lillies (Nymphaea) zone of a lake. It is the region of rapid varia- (TMO) in their blood to keep the body heat ⎯→ Nelumbo tions of the level of the water, temperature O2 Nerve fibers Basement Membrane isotonic to the sea water and avoid dehy- ⏐ availability from time to time. ⎯→ Trapha Structure of a typical Ommatidium dration of the body due to exosmosis..
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