Ecosystem Concepts Ecosystem Sir A Tansely Biotic community

Ecosystem : Concepts

Ecosystem Sir A. Tansely Biotic community + physical environment “ as a structural and functional unit of biosphere/segment of nature consisting of community of living beings and the physical environment both interacting and exchanging materials between them. ”

Ecosystem Self sufficient interacting system Small /large Open system Varied (distinct community) Not an isolated unit eg leaves falling in river water

Types of Ecosystem Natural �Terrestrial �Aquatic Saltwater Fresh water Lentic Lotic Man-made/Artificial

Components of Ecosystem Abiotic Biotic � Autotrophs/Producers Terrestrial Deep aquatic Shallow water � Heterotrophs Consumers Herbivores/first order consumers Carnivores/primary carnivores/second order consumers Secondary Carnivores/third order consumers Tertiary Carnivores/ fourth order consumers Top carnivores Decomposers/micro consumers - Mineralization

Components of Ecosystem

Abiotic Components Climatic factors Inorganic substances Organic substances Biogeochemical cycles –minerals & gases

Structure of Ecosystem Species composition- forest/desert Stratification- tropical rain forest Tropic organization- food relationships � T 1, T 2, T 3 and so on……. Nutrients

Standing Stage- amount of abiotic materials present in an ecosystem at a given time. Standing Crop - amount of biotic materials present in an ecosystem at a given time. � Expressed unit area as number/biomass of organism per

Functions of Ecosystem Productivity- g/m 2/year � Primary GPP (Gross primary productivity) NPP (Net primary productivity) NPP=GPP-Loss due to respiration & maintenance � Secondary Decomposition /Nutrient cycling Energy flow - Law of thermodynamics � Unidirectional � Energy decreases with successive trophic levels � 10%of GPP

Energy flow

Flow of Energy

Food chain The transfer of food energy from the source in plants through a series organism with repeated steps of eating and being eaten is referred as food chain The transfer of energy from one trophic level to the next trophic level is called food chain Food chains were first introduced by the African. Arab scientist and philosopher Al-Jahiz in the 9 th century and later popularized in a book published in 1927 by Charles Elton, which also introduced the food web concept

Types of Food chains Grazing Food chain � Starts with producers, passes through consumers to decomposers � A typical food chain here could be : Grass > Rabbit > Fox Detritus Food chain � Starts with dead organic matter and passes through detritus feeding organisms in soil to organisms feeding on detritus feeders and their predators � A typical food chain here could be : mangrove leaves > microbes>crabs>shrimps>small fish

Detritus food chain

Y shape flow of energy

Food Web A network of food chains which are interconnected at various trophic level so as to form a number of feeding connections among different organisms of a biotic community called food web. Alternate pathways for flow of energy Complexity > diversity Stability

food web

Significance of food chains & food webs Energy flow and nutrient cycling take place through them Ecological Balance- population size Unique property of biological magnification

Can an ecosystem regulate itself? Human beings should try to keep ecosystems within the homeostatic plateau. Should not contribute to positive feedbacks otherwise ecosystem will collapse

Ecological pyramid An ecological pyramid is a graphical representation designed to show the ecological parameters (biomass /number/energy) at each trophic level in a given ecosystem. 1927 Charles Elton – Eltonian pyramids Ecological pyramids begin with producers on the bottom and the highest level is the top of the food chain Upright/Inverted/spindle shape

Ecological pyramid Pyramid of Number Pyramid of Biomass Pyramid of Energy

Pyramid of Number

Pyramid of Biomass

Pyramid of Energy

Major Ecosystems Forest Ecosystem � Tropical rain forest � Tropical deciduous forest � Coniferous forest Abiotic � Inorganic � Climate � litter and organic substances present in soil

Biotic � Producers vegetation – trees , diff species , shrubs and ground TRF – Teak( Tectona grandis), Dhak (Butea frondosa), Sal Coniferous – Abies, Spruce, Deodar, Pine Temperate forest – Quercus (oak) � Consumers Primary Consumers Small animals feeding on trees beetles, flies, bugs, spiders, leaf -hoppers, ants Large animals – elephants, deer, moles, squirrels, mangooses etc Secondary Consumers – snakes, birds, lizards, fox etc Tertiary Consumers – lion, tiger etc � Decomposers fungi(Aspergillus, Fusarium, Alternaria, Trichoderma) bacteria (Bacillus, Pseudomonas, Clostridium)

Major Ecosystems Pond Ecosystem Abiotic � Inorganic � Climate and organic substances present in soil

Biotic � Producers – Phytoplankton and Macrophytes Phytoplankton – Ulothrix, Spirogyra, Oedogonium, Chlamydomonas, Vovox, Anabaena Macrophytes – Hydrilla, Utricularia, Vallisneris, Wolfia, Lemna, Eichhornia, Pist ia, Azolla, Typha � Consumers Primary Consumers Zooplankton – Copepods and Daphnia Benthos – annelids, molluscs Secondary Consumers – insects and fish Tertiary Consumers –large fish � Decomposers fungi(Aspergillus, Phythium) bacteria (Bacillus, Pseudomonas)