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SHANKAR IAS - SUMMARY EMIRONMENT AND ECOLOGY CRASH COURSE
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Let's take the environment of a fish in the pond. External environment of fish Its environment consists of abiotic components such as light, temperature, including the water in which nutrients, oxygen, other gases and organic matter are dissolved. The biotic environment consists of microscopic organisms called plankton as well as 10 aquatic plants and animals and decomposers. Internal environment of fish It is enclosed by the outer body surface. The internal environment is relatively stable as compared to the external environment. However, it is not absolutely constant. Injury illness or excessive stress upsets the internal environment. For example, if a marine fish is transferred to a fresh water environment, it will not be able to survive
Ecologists organize their study into several levels (ecological hierarchy) Total area of Earth where living things are found Biosphere A single living thing Organism Population Community Ecosyst Living community + physical environment Same species sharinga habitat Different populations interacting in a particular area p
LEVELS OF ORGANISATIONS IN Individual ECOLOGY a Population .The main levels of organisation of ecology are six and are as follows. Community Individual Ecosystem Organism is an individual living being that has the ability to act or function independently, It may be plant, animal, bacterium, fungi, etc. It is a body made up of organs, organelles, or other parts that work together to carry out on the various processes of life Biome Biosphere
Population .Population is a group of organisms usually of the same species, occupying a defined area during a specific time. Population growth rate is the percentage variation between the number of individuals in a population at two different times. Therefore the population growth rate can be positive or negative. .The main factors that make population grow are birth and immigration. The main factors that make population decrease are death and emigration. The main limiting factors for the growth of a population are abiotic and biotic components. Population density is the relation between the number of individuals of a population and the area they occupy .
Community .If we look around our self, we will notice that population of plants and animals seldom occur by themselves. The reason for this is quite obvious., In order to survive, individuals of any one species depend on individuals of different species with which they actively interact in several ways. A grassland community is dominated by grasses, though it may contain herbs, shrubs, and trees, alongwith associated animals of different species. Tyres oaf commu nf size and degree of relative independence On the basis of size and degree of relative independence communities may be divided into two type:s Major Community These are large-sized, well organized and relatively independent
They depend only on the sun's energy from outside and are independent of the inputs and outputs from adjacent communities. E.g: tropical ever green forest in the North-East Minor Communities These are dependent on neighbouring communities and are often called societies. They are secondary aggregations within a major community and are not therefore completely independent units as far as energy and nutrient dynamics are concerned. e.g: A mat of lichen on a cow dung pad. Structure of a community In a community the number of species and size of their population vary greatly. A community may have one or several species. The environmental factors determine the characteristic of the community as well as the pattern of organisation of the members in the community.
The characteristic pattern of the community is termed as structure which is reflected in the roles played by various population, their range, the type of area they inhabit, the diversity of species in the community and the spectrum of interactions between them