Ecosystems and their importance and classification

ecosytems its classification and function

1. Dr. narayan panda Assistant Professor Odisha University of Agriculture and Technology, Bhubaneswar, India-751003 Ecosystem, its Classification and function Environmental Studies and Disaster Management AC-213 (ESDM)

2. The concept of ecosystem was 1 st put forth by A. G. Tansley (1935). According to E. P. Odum ;- Father of Ecology Ecosystem is the basic functional unit of organisms and their environment interacting with each other and with their own component. What is Ecosystem ? is an integrated unit is a discrete unit of space is a unit/system which is composed of a number of sub-units The environment in which a particular organism lives is called its habitat . The role of an organism in a habitat is called its niche .

3. Structure of ecosystem The structure of an ecosystem basically describes the organisms and physical feature of the environment It also provides a range of climatic conditions prevailing in the area. All ecosystem consists of the following components Abiotic component Biotic component

4. a) Abiotic component The physical and chemical components of an ecosystem constitute its abiotic structure. It includes climatic factors , edaphic factors, geographic factors, energy, nutrients , and toxic substances. Chemical factors Availability of major essential nutrients like C, N, P, K, O, S, toxic substances, salts, and organic substances present in the soil or water largely influence the functioning of the ecosystem . Physical factors The sunlight and shade , intensity of solar flux, sunshine hours , temperature, rainfall , wind, latitude , longitude, soil type, water availability , etc. are some of the physical features which have strong influence on the ecosystem.

5. b) Biotic components The biotic components include all living organisms present in the environmental system. Biotic components of an ecosystem can be described under following heads. Producers Consumers Decomposers

6. Producers are organisms that are capable of using sources of energy ( sun light ) to make complex, organic molecules from the simple inorganic substances in their environment. -In terrestrial eco systems , plants are the major producers In aquatic ecosystems, phytoplankton are the predominant Consumers are organisms that require organic matter as a source of food. -Primary consumers (herbivores) -Secondary consumers (carnivores) -Omnivores -Scavenger ( eg . vulture, blowflies) -Parasite ( eg . Tapeworm, Many bacteria, insects, etc) Decomposers are organisms that use nonliving organic matter as a source of energy and raw materials to build their bodies. E.g. Bacteria , Fungi, some worms, etc.

7. DIFFERENT TYPES OF ECOSYSTEM

8. Natural Ecosystem A. Forest Ecosystem Abiotic Inorganic and organic substances found in the soil and atmosphere. Climatic, edaphic , forest litter (humus) etc. are some attributes varies with different forest types and determines their functional features. Biotic Producers Mainly trees, shrubs, herbs and other plants. A great degree of variation in tree composition and stratification is observed in different forests. For example: dominant tree species in Tropical moist deciduous forest-teak, Sal, Dhak , lagerstroemia etc. Temperate coniferous forest- Pines, Deodar, Spruce etc. Temperate broad leaf forest- different species of oak Consumers Primary Secondary Tertiary - Herbivores those who feed on the leaves, fruits, nuts and other plant parts. Ex. Ant, flies, beetles , spiders bugs, ruminants, etc. -Carnivores feeding on herbivores ex. Snake, birds, lizards etc. Top carnivores feeding on secondary consumers like tiger, lion etc. Decomposers Includes a wide variety of microorganisms like bacteria, fungi, actinomycetes . The rate of turnover is higher in tropical and subtropical forests than temperate forests.

9. B. Grassland ecosystem: Grassland ecosystem generally receives such an amount of rainfall which is not enough to support a forest but enough to prevent it from being desert. Dominant vegetation-grasses, sedges , forage plants and few tree species . B1. Tropical grassland: Tropical grasslands are located near the equator between the tropic of cancer and the tropic of Capricorn. They cover much of Africa, as well as large areas of Australia, South America and India with an annual rainfall ranging between 50-127 cm . Tropical grasslands are also known as Savanna in Africa and llanos in South America.   B2. Temperate Grassland: The most prominent temperate grass lands are found in the great plains of Canada and the United States, Argentina, South Africa, Central Eurasia and Australia. In United States and Canada these grass lands are known as Prairies, in South America and Argentina as Pampas , S. Africa as Veldt, central Europe and Asia as Steppe . The climate is characterized by moderate rainfall, hot summer and cold winter for which vegetation is primarily dominated by grass without trees and shrubs.

10. C. Desert Ecosystem: Desert ecosystem is characterized by extremely low rain fall ( less than 25 cm ) and high temperature. Deserts occupy about 17% of the land. Abiotic components : -poor nutrient cycling because of scanty biota, high temperature and low rainfall. Biotic components : Producers: Shrubs, bushes, some grasses and few trees. Sometimes succulents like cacti , lower plants like lichens and xerophytic mosses are also present. Consumers - Primary - Herbivores and plant eating insects including termites, millipedes - Secondary: Reptile, nocturnal rodents, birds etc. - Tertiary: Hawks, kites, owl etc. Decomposers: Thermophylic fungi and bacteria.

11. Aquatic ecosystem : Aquatic ecosystem deals with water and biotic communities present in them may be either freshwater or marine . Fresh water ecosystem is either standing type ( lentic ) like ponds & lakes or free flowing type like rivers ( lotic ). A. Pond ecosystem: Pond is a small lentic freshwater ecosystem where water is filled in the rainy season. It plays a critical role in the life of pond centric rural villagers. The pond water can also be divided into Epilimnion and Hypolimnion based on temperature differences. In between the two layers there is an intermediate zone known as Thermocline

12. Abiotic components : -heat, light intensity, pH value of water, dissolved organic and inorganic salts, turbidity etc. Biotic components : a. Producers: Macrophytes (either submersed, floating or emergent type like hydrilla and free floating forms like Azolla ) and Phytoplankton. b. Consumers - Primary - Benthic population (consisting of fish, beetles, mites, mollusks, crustaceans etc.) and zooplanktons - Secondary: Insects and fish which feed on zooplanktons. - Tertiary: Large carnivorous fish c. Decomposers: Fungi (like Aspoergillus , Phythium etc.), bacteria. And actinomycetes Pond Ecosystem

13. Pond Ecosystem

14. Lake ecosystem: Lakes are usually big freshwater bodies with standing water. Different Layers: shallow water zone called littoral zone , an open water zone where effective penetration of solar light takes place called limnetic zone and a deep bottom area where light penetration is negligible known as profundal zone . On the basis of the temperature variation in lake water the lake can be divided into two zones.

15. River and stream ecosystems: Water current is a major controlling factor in these fresh water ecosystems. Oxygen and nutrient is more uniform and land water exchange is more extensive. Producers: Green algae, diatoms and aquatic mosses Consumers: Different kinds of fish, crocodiles, flatworms, leeches, freshwater sponges, caddis-fly larvae, snils , mayfly nymphs etc. some birds also get their food from streams and rivers. Decomposers : Fungi, bacteria and actinomycetes .

16. Marine Ecosystem: The oceans constitute nearly 70% of the earth’s surface. Of all the water found in the earth, 97% is marine. The marine region is divided between coral reefs , estuaries and oceans Producers Phytoplankton (diatoms, dinoflagellates), large marine plants (sea weeds) Consumers Primary Secondary Tertiary Zooplanktons crustaceans, molluscs , fish etc. Insects and carnivorous fish (like herring, shad, mackerel etc) Large carnivorous fish like cod, haddock etc. Decomposers Bacteria and some Fungi

17. Estuaries ecosystem: An estuary is a partially enclosed coastal area at the mouth of the river where fresh water and salty sea water meet. These are the transition zones which are strongly affected by the action of tidal action. River mouths , coastal bays, tidal marshes etc are some examples of estuaries ecosystem. The constant mixing of water makes this zone rich in nutrients for primary producers. Because of high productivity estuaries are rich in biodiversity and many of them are endemic. The chief biotic components of estuarine ecosystem are: Producer: microphytes such as marsh, grasses, sea weeds, sea grasses etc., benthic algae, and phytoplankton Consumer: Oysters, crabs, shrimps, and much kind of fishes etc.

18. Estuaries ecosystem:

19. Coral reef ecosystem: Coral reefs are diverse underwater ecosystems held together by calcium carbonate structures secreted by corals and certain algae. Class: Cnidaria It is Hermatypic (hard) corals, contains symbiotic algae up to 500 spp. at some sites. Individual animals are called polyps . Several polyps make up a colony.  Corals are capable of both sexual and asexual reproduction . Corals build protective shells of calcium carbonate around their bodies which after their death, sink and accumulate on the sea bottom. Coral ecosystems are confined mainly to the warm waters of the pacific and Indian oceans . The reef building corals grow best in normal saline waters (35g/L ) at annual temperature of about 24 C at a depth of 40-50 m eters.

20. Types of Coral Reefs: 1. Fringing Reef. : This type of reef grows seaward directly from the shore. They form borders along the shoreline and surrounding islands are most common type of reef. 2. Atoll Reef: When a fringing reef continues to grow upward from a volcanic island that has sunk entirely below sea level, an atoll is formed. Atolls are usually circular or oval in shape, with an open lagoon in the center. 3. Barrier reefs: These are similar to fringing reefs in that they also border a shoreline; however, instead of growing directly out from the shore, they are separated from land by an expanse of water. This creates a lagoon of open, often deep water between the reef and the shore. Uses: Many drugs are now being developed from coral reef animals and plants as possible cures for cancer, arthritis , human bacterial infections , viruses, and other diseases .

21. Most corals are made up of hundreds of thousands individual polyps like this one, 1-3 mm in diameter. Most food is captured with the help of special stinging cells called nematocysts which are inside the polyp' outer tissues, which is called the epidermis. Calcium carbonate is secreted by reef-building polyps and forms a protective cup called a calyx within which the polyps sits.

22. Coral reef ecosystem Great Barrier Reef – Australia. New Caledonia Barrier Reef – New Caledonia. Red Sea Coral Reef – Red Sea. Rainbow Reef – Fiji. Tubbataha Reefs – Cagayancillo , Philippines. Raja Ampat – Indonesia. Palancar Reef – Cozumel, Mexico. Wakatobi Islands – Indonesia.

23. Lagoon A  lagoon  is a shallow body of water separated from a larger body of water by barrier islands or reefs.

24. FUNCTION OF AN ECOSYSTEM Every ecosystem receives energy from the sun and pass it on through various biotic components by which all life persists on the earth . Major functional attributes of ecosystem are: Food chain, food web and trophic structure Energy flow Biogeochemical cycles Primary and secondary production Ecosystem development and regulation.

25. Food chain, food web and trophic structure The sequence of eating and being eaten in an ecosystem is known as food chain. The flow of energy is mediated through food chain. The consumers and producers are arranged in the ecosystem in a definite manner and their interactions along with the population size are expressed together as trophic structure. Each food level is known as trophic level and the amount of living matter at each trophic level at a given time is known as standing crop or standing biomass . Interconnected and usually complex network with several linkages of food chain is known as food web . A different types of organism are connected at different trophic levels so that there are a number of options for eating and being eaten at each trophic level.

26. Food Chain Grazing food chain : it starts with green plants (Producers) and culminates with carnivores. b. Detritus food chain : it starts with dead organic matter which the detritivores and decomposers consume. Grass land ecosystem: Grass Grass hopper Frog Snake Hawk Pond ecosystem : Phytoplankton Water fleas Small fish Tuna fish Significance of food chain and food web: Energy flow and nutrient cycling takes place through them Helps in maintaining ecological balance Shows biomagnification of some chemicals (Like DDT, a broad range insecticide).

27. Ecological Pyramids Graphic representation of trophic structure and function of an ecosystem starting with producers at the base and successive trophic levels forming the apex is known as ecological pyramid. Ecological pyramids are of three types a. Pyramid of numbers b. Pyramid of biomass c. Pyramid of energy

28. Pyramid of numbers It represents the relationship between the producers, herbivores and consumers at successive trophic levels in terms of their number. Pyramid of numbers may be upright or inverted type depending upon the type of ecosystems and food chain.

29. Pyramid of biomass It describes the total biomass (dry mass) at each trophic level in a food chain. The pyramid of biomass can also be upright or inverted.

30. Pyramid of energy It shows the rate of energy flow or productivity at successive trophic levels. It is a picture of the rates of passage of food mass through food chains. So it’s shape is always upright . Because there is always a gradual decrease in the energy content at successive trophic levels from the producers to various consumer. (At every successive trophic level there is a huge loss of energy ( about 90%) in the form of heat, respiration etc. and 10% of energy passes on to the next higher trophic level).

31. Ten(10) % energy and transfer rule: [ Lindemann ,1942] According to the law, during the transfer of organic food from one tropic level to the other only 10 percent of organic matter is stored as flesh and the remaining is lost during transfer or broke down during respiration process. On a clear day, radiant energy reaching the earth surface is about 10% UV, 45% visible and 45% infra-red. About 34 % of the sunlight reaching the earth’s atmosphere is reflected back into its atmosphere, 10% is held by the ozone layer, water vapour and other gases. The rest 56% reaches the earth’s surface. Only a fraction of this energy ( 1-5% ) is used by the green plants for photosynthesis. Plants absorb strongly the blue and red light.

32. Flow of Energy in ecosystem Energy is defined as the ability to do work. Flow of energy in an ecosystem takes place through food chain and helps in ecosystem functioning. Energy flows from one organism to another in an ecosystem in a unidirectional manner. It follows the two laws of entropy or thermodynamics as follows. 1 st law of thermodynamics: Energy may be transformed from one type into another but is neither created nor destroyed. [ The solar energy is captured by the green plants, get converted into biochemical energy of plants and later that of consumers ] 2 nd law of thermodynamics: Energy dissipates as it is used i.e. no process involving an energy transformation will spontaneously occur, unless there is a degradation of the energy from a concentrated form into a dispersed form. [ Dissipation of energy takes place at each trophic level of food chain and it is approximately 90%.]

33. For understanding the energy flow efficiency of an ecosystem the following points may be considered. The efficiency of producers in conversion and absorption of solar energy Use of chemical energy of autotrophs by consumers Assimilation efficiency of carnivores Loss through metabolism and locomotion The gross net production