ECOSYSTEM - INTRODUCTION Dr. Sristisri Upadhyaya Assistant Professor Dept. of Botany Mangaldai College Darrang-784125, Assam

Ecosystem is a system formed by the interaction of a variety of organism among themselves and with the physical environment. or The structural and functional system of communities and their environment is called Ecological system or ecosystem. The term Ecosystem was first proposed by A.G. Tansley (1935)

CENTRAL DOGMA OF ECOSYSTEM CONCEPT: At any place where organisms live, there is a continuous interaction between plants, animals and their environment to produce and exchange materials. It means that there are mechanisms for – Continuous absorption of materials by organisms for The purpose of production of organic materials and release and Conservation of the organic material into inorganic form. - also known as cycling of material.

Structure of Ecosystem Abiotic component Biotic component Inorganic - C, H, O, N etc. Consumer Producer Decomposer Organic – Protein, Carbohydrate etc. Animals Green plants Microbes Climatic – Temperature, light (duration, intensity)

A total study of all the components is essential for complete analysis of an ecosystem. BIOTIC COMPONENTS: The Producer – Green plants The Consumer – a) The primary consumer/Consumer of the first order Ex.- Herbivorous animal (rabbit, insects etc.) b) The secondary consumer/Consumer of the second order Ex.- Toad, bird, small carnivorous fish etc. c) The tertiary consumer/Consumer of the third order Ex.- Snake, big carnivorous fish d) The top consumer/Consumer of the highest order Ex.- Lion, Vulture etc.

3) The decomposers – Fungi, bacteria etc 3) The decomposers – Fungi, bacteria etc. ABIOTIC COMPONENTS: 1) The inorganic components: Carbon, nitrogen, hydrogen etc. which are involved in cycling 2) The organic components: Protein, carbohydrates etc. which make the body of the organisms 3) The climatic components: Temperature, light duration and intensity etc.

FOOD CHAIN: The series of organisms fixing energy, eating and being eaten is called a food chain. 3 types of food chain- 1) Grazing food chain: starts with green plants. Ex. Grass Grasshopper Frog Snake Vulture 2) Parasitic food chain: starts with higher organisms. Ex. Higher animals Leach, Lice Bird Snake Vulture 3) Detritus food chain: starts with dead organic matters. Ex. Dead parts of plants & animals Microbes Protozoa, Nematodes Higher animals

FOOD WEB: The trophic relationship of the biotic component of an ecosystem are not always simple chain like structure. Sometimes one food chain linking with another forming complex network structure, this network structure is known as food web. Ex. - Food web of terrestrial ecosystem Grass Rabbit Wild cat Tiger/Lion Wild dog Insect Toad Bird Jackal Rat Snake Vulture Leech

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