UNIT 2: ECOLOGY AND ECOSYSTEMS •Concept of ecology and ecosystem, Structure and function of ecosystem; Energy flow in an ecosystem; food chains, food webs; Basic concept of population and community ecology; ecological succession. •Characteristic features of the following: a) Forest ecosystem b) Grassland ecosystem c) Desert ecosystem d) Aquatic ecosystems (ponds, streams, lakes, wetlands, rivers, oceans, estuaries) ECOLOGY: Ecology (from the Greek “oikos” meaning "house" or "dwelling", and “logos” meaning "to study") is the study of the interactions of organisms with each other and their environment. The hierarchy define each of the following. species ~genus~ population ~ community ~ ecosystem ~ biosphere AUTECOLOGY & SYNECOLOGY: Autecology & Synecology are two main branches of ecology. Autecology is the study of individual organism or individual species. It is also known as population ecology. Synecology is the study of group of organisms of different species which are associated together as a unit in form of a community. Levels of Ecological Study ORGANISMAL ECOLOGY - the study of individual organisms' behavior, physiology, morphology, etc. in response to environmental challenges. POPULATION ECOLOGY - the study of factors that affect and change the size and genetic composition of populations of organisms. COMMUNITY ECOLOGY - the study of how community structure and organization are changed by interactions among living organisms ECOSYSTEM ECOLOGY - the study of entire ecosystems, including the responses and changes in the community in response to the abiotic components of the ecosystem. This field is concerned with such large-scale topics as energy and nutrient cycling. LANDSCAPE ECOLOGY – study of the exchanges of energy, materials, organisms and other products of between ecosystems. GLOBAL ECOLOGY - the study of the effects of regional change in energy and matter exchange on the function and distribution of organisms across the biosphere. ECOSYSTEM: An ecosystem is a large community of living organisms (plants, animals and microbes) in a particular area. The living and physical components are linked together through nutrient cycles and energy flows. Ecosystems are of any size, but usually they are in particular places. STRUCTURE OF AN ECOSYSTEM: An ecosystem consists of 2 components: 1. Abiotic components - The non living factors or the physical environment prevailing in an ecosystem form the abiotic components. They have a strong influence on the structure, distribution, behaviour and inter-relationship of organisms. Abiotic favtors are light, temperature, water, nutrients, topography, etc. Abiotic components are mainly of two types: Climatic Factors: Which include rain, temperature, light, wind, humidity etc. Edaphic Factors: Which include soil, pH, topography minerals etc. SNC/KOUSIK GHOSH/2019 Page 1 2. Biotic Components: The living organisms including plants, animals and micro-organisms (Bacteria and Fungi) that are present in an ecosystem form the biotic components. On the basis of their role in the ecosystem the biotic components can be classified into three main groups: Producers Consumers Decomposers or Reducers. Producers: The green plants have chlorophyll with the help of which they trap solar energy and change it into chemical energy of carbohydrates using simple inorganic compounds namely water and carbon dioxide. This process is known as photosynthesis. As the green plants manufacture their own food they are known as Autotrophs (i.e. auto = self, trophos = feeder) The chemical energy stored by the producers is utilised partly by the producers for their own growth and survival and the remaining is stored in the plant parts for their future use. Consumers: The animals lack chlorophyll and are unable to synthesise their own food. Therefore, they depend on the producers for their food. They are known as heterotrophs (i.e. heteros = other, trophos = feeder) The consumers are of four types, namely: Primary Consumers or First Order Consumers or Herbivores: These are the animals which feed on plants or the producers. They are called herbivores. Examples are rabbit, deer, goat, cattle etc. Secondary Consumers or Second Order Consumers or Primary Carnivores: The animals which feed on the herbivores are called the primary carnivores. Examples are cats, foxes, snakes etc. Tertiary Consumers or Third Order Consumers:These are the large carnivores which feed on the secondary consumers. Example are Wolves. Quaternary Consumers or Fourth Order Consumers or Omnivores:These are the largest carnivores which feed on the tertiary consumers and are not eaten up by any other animal. Examples are lions and tigers. Decomposers or Reducers: Bacteria and fungi belong to this category. They breakdown the dead organic materials of producers (plants) and consumers (animals) for their food and release to the environment the simple inorganic and organic substances produced as by-products of their metabolisms. These simple substances are reused by the producers resulting in a cyclic exchange of materials between the biotic community and the abiotic environment of the ecosystem. The decomposers are known as Saprotrophs (i.e., sapros = rotten, trophos = feeder) Ecosystem Abiotic components Biotic components Climatic Factors Edaphic Factors Producers Consumers Decomposers (Autotrophs) (Heterotrophs) (Saprotrophs) Rain Soil Primary Light pH Secondary Wind Minerals Tertiary Temperature Topography Quaternary SNC/KOUSIK GHOSH/2019 Page 2 FUNCTIONS OF AN ECOSYSTEM: In the ecosystem, biotic components and other materials like N, C, H2O Circulated within and outside of the system. The energy is transferred from one tropic level to the other in the form of a chain called as food chain. The important source of energy is the sun. Some factors which are responsible for high productivity. for example high temperature and rainfall accelerate weathering and decomposition of dead organic matter. Climatic changes is the functioning of ecosystem Effects of local and regional shifts of energy, materials and populations on ecosystems and economic of rational use of ecosystem. Production, consumption and decomposition are important functions of ecosystem. Production: "Conservancy of solar energy into potential energy" Every year about 100 billion tones of organic matter is produced on the earth by "Photosynthetic organisms". Photosynthesis by Green plants The plants capture the solar energy and converted into carbohydrate through the process of photosynthesis Chlorophyll 6 CO2 + 12 H2O C6H12O6 + 6O2 + 6H2 O The Presence of chlorophyll in the plants absorbs sun light, CO2 and water to prepare carbohydrate and liberate oxygen. Composition (Consumption): It is the process of transfer of material and transformation of energy from one tropic level to another through the process of eating and being eaten. SNC/KOUSIK GHOSH/2019 Page 3 Decomposition: It is a process in which complex compounds are broken into simpler compounds. The simple compounds can be utilizes for plants growth. This process is done by bacteria and fungi. In ecosystem dead bodies are decomposes by bacterial action. ENERGY FLOW IN AN ECOSYSTEM An ecosystem comprises biotic and abiotic components which interact extensively with each other. Based on their ecological roles, the biotic components of an ecosystem can be classified as: Producer: they are the green plants which absorb solar energy to synthesize complex organic compounds from simple inorganic substances by photosynthesis, they act as the ultimate food source to all the heterotrophs. The other producers are green algae and blue green algae, they are mainly found in aquatic habitat, such as freshwater and marine water, they are the most important producers in earth (as 70% of the earth surface is covered with water). Consumer: they are heterotrophs which ingest other organisms or organic particles, they are mainly animals primary consumer : they are the herbivores which feed on plants e. g. pond snail, insect larva and zooplanktons secondary consumer : they are the carnivores which feed on primary consumers e. g. water beetles, tigers, etc. tertiary consumer : they are large carnivores which feed on the secondary and primary consumers as well as producers, e. g. man detritus consumer : they are detritivores ( detritus feeder / scavengers) which feed on detritus that refer to the particulate organic matter involved in the decomposition of dead organisms, e. g. earthworm and crab etc. Decomposer: they are mainly bacteria, fungi and some flagellates, by means of their saprophytic activities; they decompose the eliminated products of animals and the dead bodies of the organisms into simple compounds, these compounds are absorbed as nutrients by the green plants again they enable the nutrients to be used continuously in a cyclic form in the ecosystem. They are most abundant in the soil or water bottom where the dead bodies of plant and animals accumulate when the temperature conditions are favourable, decomposition occurs rapidly Energy and essential materials are therefore transferred from producers to consumers through the feeding processes. Eventually, decomposers break down the organic matter and release inorganic materials back to the environment. These inorganic materials are used by the producers as nutrients again. Food chain: the transfer of food energy from producers through a series of organisms with repeated eating and being eaten Ecosystem Producer Primary Secondary Tertiary consumer consumer consumer freshwater pond green algae