Unit 2-Lesson 9-AQUATIC ecosystems
AQUATIC ECOSYSTEMS
Aquatic ecosystems refers to plant and animal communities ocuring in water bodies.Aquatic ecosystems are classified on the basis of salinity into following two types:
(i) Freshwater
(ii) Marine
(i) Fresh water ecosystem
Water on land which is continuously cycling and has low salt content is known as fresh water and its study is called limnology.
(i) Static or still water (Lentic) e.g. pond, lake, bogs and swamps.
(ii) Running water (Lotic) e.g. springs, mountain brooks, streams and rivers.
Physical characteristics: Fresh waters have a low concentration of dissolved salts.The temperature shows diurnal and seasonal variations. In tropical lakes, surface temperature never goes below 40 degree Celcius, in temperate fresh waters, never goes above or below 4 degree Celcius and in polar lakes never above 4 degree Celcius.
• In temperate regions, the surface layer of water freezes but the organisms survive below the frozen surface.
• Light has a great influence on fresh water ecosystems.Alarge number of suspended materials obstruct penetration of light in water.
• Certain animals float upto water surface to take up oxygen for respiration Aquatic plants use carbon dioxide dissolved in water for photosynthesis.
• Lakes and ponds are inland depressions containing standing water.The largest lake in the world is lake Superior in NorthAmerica. Lake Baikal in Siberia is the deepest. Chilka lake of Orissa is largest lake in India.
LAKE BAIKAL
LAKE SUPERIOR
CHILKA LAKE (ORISSA,INDIA)
Three main zones can be differentiated in a lake:-
• Peripheral zone (littoral zone) with shallow water.
• Open water beyond the littoral zone where water is quite deep.
• Bentic zone (bottom) or the floor of the lake.
Aquatic organisms can be floating in water or free swimming or sedentary (fixed), depending on their size and habit. Microscopic floating organisms such as algae, diatoms, protozoans and larval forms are called plankton. Rooted aquatic plants, fish, mollusk and echinoderms are bottom dwellers.
Wetlands are areas that periodically get inundated with water and support a flourishing community of aquatic organisms including frog and other amphibians. Swamps, marshes and mangroves are examples of wetlands.
PLANKTONS
PLANKTONS
(ii) Marine ecosystem:Pertains to the seas and oceans including marine organisms.
Salinity of open sea is 3.6% and is quite constant.The range of temperature variation is much less in the sea than on the land. Hydrostatic pressure due to water column increases with depth in oceans. It is 1 atm near the surface and 1000 atm at greatest depth.Animals in the deeper layers are adapted to the high pressure. Some marine organisms such as sperm whales and certain seals can dive to the great depths and swim back to the surface without difficulty. Tides, due to gravitational pull of the moon are a common feature of marine ecosystems.
• Flora and fauna: Biodiversity of the marine ecosystems is very high as compared to terrestrial ecosystems.Almost every major group of animals occurs in the sea. Insects and vascular plant are completely absent in marine ecosystem. Maximum diversity of marine organisms is found in the tidal zone that is near the shore. Diatoms, algae, dinoflagellates and jelly fishes are some of the free floating life forms in oceans. Large crustaceans, molluscs, turtles and mammals like seals, porpoises, dolphins and whales are free swimming animals that can navigate. Bottom dwellers are generally sessile (fixed) organisms like sponges,corals, crabs and starfish.
Adaptations:
• Light weight animals and plants float in water and move with the water currents.
• Animals and plants in ocean are tolerant to high concentration of salts (osmoregulation).Osmoregulation is the process by which a constant osmotic pressure is maintained in blood.
• Swimming animals have streamlined body. Their body is laterally compressed.
• Deep sea forms show bioluminescence (they emit light).
• They are dependent for their food on the upper sea zones.
Aquatic ecosystems refers to plant and animal communities ocuring in water bodies.Aquatic ecosystems are classified on the basis of salinity into following two types:
(i) Freshwater
(ii) Marine
(i) Fresh water ecosystem
Water on land which is continuously cycling and has low salt content is known as fresh water and its study is called limnology.
(i) Static or still water (Lentic) e.g. pond, lake, bogs and swamps.
(ii) Running water (Lotic) e.g. springs, mountain brooks, streams and rivers.
Physical characteristics: Fresh waters have a low concentration of dissolved salts.The temperature shows diurnal and seasonal variations. In tropical lakes, surface temperature never goes below 40 degree Celcius, in temperate fresh waters, never goes above or below 4 degree Celcius and in polar lakes never above 4 degree Celcius.
• In temperate regions, the surface layer of water freezes but the organisms survive below the frozen surface.
• Light has a great influence on fresh water ecosystems.Alarge number of suspended materials obstruct penetration of light in water.
• Certain animals float upto water surface to take up oxygen for respiration Aquatic plants use carbon dioxide dissolved in water for photosynthesis.
• Lakes and ponds are inland depressions containing standing water.The largest lake in the world is lake Superior in NorthAmerica. Lake Baikal in Siberia is the deepest. Chilka lake of Orissa is largest lake in India.
LAKE BAIKAL
LAKE SUPERIOR
CHILKA LAKE (ORISSA,INDIA)
Three main zones can be differentiated in a lake:-
• Peripheral zone (littoral zone) with shallow water.
• Open water beyond the littoral zone where water is quite deep.
• Bentic zone (bottom) or the floor of the lake.
Aquatic organisms can be floating in water or free swimming or sedentary (fixed), depending on their size and habit. Microscopic floating organisms such as algae, diatoms, protozoans and larval forms are called plankton. Rooted aquatic plants, fish, mollusk and echinoderms are bottom dwellers.
Wetlands are areas that periodically get inundated with water and support a flourishing community of aquatic organisms including frog and other amphibians. Swamps, marshes and mangroves are examples of wetlands.
PLANKTONS
PLANKTONS
(ii) Marine ecosystem:Pertains to the seas and oceans including marine organisms.
• Distribution: Marine ecosystem covers nearly 71% of the earth’s surface with an average depth of about 4000 m. Fresh water rivers eventually empty into ocean. See the map below.(the darker shades of Blue indicates the richer Marine ecosystems of the World)
Different kinds of organisms live at different depths of the sea or ocean.
Salinity of open sea is 3.6% and is quite constant.The range of temperature variation is much less in the sea than on the land. Hydrostatic pressure due to water column increases with depth in oceans. It is 1 atm near the surface and 1000 atm at greatest depth.Animals in the deeper layers are adapted to the high pressure. Some marine organisms such as sperm whales and certain seals can dive to the great depths and swim back to the surface without difficulty. Tides, due to gravitational pull of the moon are a common feature of marine ecosystems.
• Flora and fauna: Biodiversity of the marine ecosystems is very high as compared to terrestrial ecosystems.Almost every major group of animals occurs in the sea. Insects and vascular plant are completely absent in marine ecosystem. Maximum diversity of marine organisms is found in the tidal zone that is near the shore. Diatoms, algae, dinoflagellates and jelly fishes are some of the free floating life forms in oceans. Large crustaceans, molluscs, turtles and mammals like seals, porpoises, dolphins and whales are free swimming animals that can navigate. Bottom dwellers are generally sessile (fixed) organisms like sponges,corals, crabs and starfish.
Adaptations:
• Light weight animals and plants float in water and move with the water currents.
• Animals and plants in ocean are tolerant to high concentration of salts (osmoregulation).Osmoregulation is the process by which a constant osmotic pressure is maintained in blood.
• Swimming animals have streamlined body. Their body is laterally compressed.
• Deep sea forms show bioluminescence (they emit light).
• They are dependent for their food on the upper sea zones.
A Bioluminescent organism of the deep - A jelly fish
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