Title ORGANISMS & POPULATIONS.pdf ✅

 Digital www.allendigital.in [ 3 ] 1. Introduction : The term ecology was coined and described by – E. Haeckel Father of ecology – Reiter Father of Indian Ecology – Prof. Ramdeo Misra First of all term ecology was employed for study of plant by – Warming Definition: The study of interaction or inter-relationship of organisms with their environment is called ecology. Organism Environment Organism and environment are interdependent, inter-related or mutually reactive. Ecology is a subject which studies the interactions among organisms and between the organism and its physical (abiotic) environment. Branches of Ecology – It is based on organisation level. (a) Autecology – Study of the relation of a single species with its environment is known as autecology (Here unit of study is a single species). It is also called species ecology. (b) Synecology – Study of the relation of the group of different species with their environment is known as synecology. (Here unit of study is community.) 2. Ecological Hierarchy : Organism → Population → Community → Ecosystem → Biome → Biosphere ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯→ Size → Increase Complexity → Increase Note : • Landscape : - It is a unit of land with a natural boundary having a mosaic of patches. These patches generally represent different ecosystem. In ecological hierarchy landscape can be present between Ecosystem and Biomes. • Habitat : -Physical area where an organism lives. The physico-chemical (abiotic) components (mainly temperature, water, light and soil) alone do not characterise the habitat of an organism completely; the habitat includes biotic components also – pathogens, parasites, predators and competitors – of the organism with which they interact constantly. • Micro climate and Micro habitat :- Subdivision of habitat is called microhabitat it is an immediate climate (real climate) of an organism which is different from the average climate of region. e.g. Forest floor, Burrow and surface of desert. Organisms and Populations 01
NEET : Biology [ 4 ] www.allendigital.in  Digital (1) Organism : An organism is the smallest unit of ecological hierarchy and basic unit of ecological study. • It may be small/large, unicellular/multicellular. • Fixed life span (birth to natural death) and organized life cycle. • Ecology at the organismic level is essentially physiological ecology. An organism adapts its physiology to its surrounding environment. (2) Population : A group of Individuals (members) of same species living at one place (specific geographical area) constitute a population. (A) Local Population or demes (Sub groups of population) :- Population of organism inhabiting a particular area. e.g. Homo sapiens inhabiting hills and plains (B) Sister population :- Different population of same species of organisms which are found in different places are known as sister population. (C) Metapopulation :- A set of local population which are interconnected by dispersing individuals. (D) Species : Definition - Species is a basic unit of classification, defined as the group of living organisms similar in structure, function and behaviour and produced by similar parents, have common gene pool, can inter breed under natural conditions and reproductively isolated from other group of organism. Some terms related to species : • Endemic Species or Endemism : A species which is found only in a particular area is known as endemic species. e.g. Metasequoia is found only in valley of China, Kangaroo in Australia. Ecosystem ORGANISMS ANIMALS MICROBES PLANTS Kangaroo (Mammalia) Metasequoia (Gymnosperm)
Organisms and Populations  Digital www.allendigital.in [ 5 ] • Key-stone Species : The species which have great influence on the community's characteristics relative to their low abundance or biomass are called key-stone species. The activities of key-stone species determine the structure of the community. e.g. Lion in forest, Kangaroo rat in desert, Fig tree in tropical forest, Pisaster. • Critical Link Species : The species which establishes an essential link with other species to help the latter in some vital activity is called link species. e.g. Mycorrhizal fungi, many insect species which works as pollinators of flowers. (3) Community : Groups of organisms of different species that live in common area, which are interrelated and interdependent. It is a natural aggregation of plants, animals and microbes (biotic community) interacting in the same environment/area. Biotic Community = Animal community + Plant community + Microbial community (A) Characteristics of a community : (i) Species Diversity :- There are different types of population (species) found in community, this is called species diversity. It depends on size of the area, type of area, type of soil, altitude, climate. (ii) Dominance :- The highest number of organisms of a species present in community, is called as the dominant species. Whole community is known by the name of that particular dominant species. e.g. Prosopis in Aravalli hills, Pinus in Himalaya and mangrove forest. Lion in forest Kangaroo rat in desert Fig tree in tropical forest Mycorrhizal fungi and plants Bees and plants Pinus in Himalaya Mangrove forest
NEET : Biology [ 6 ] www.allendigital.in  Digital (iii) Stratification :– The different growth form (trees, shrubs, under shrubs, herbs) determines the structure of a plant community. Stratification is based on mode of arrangement of various growth forms. (a) Stratification in lake :- In deep lake, zonation or stratification may be according to the need of light. There are three types of zones differentiated in a deep lake. • Littoral Zone – This zone is found at bank of lake where very shallow water or marshy land is present. Rooted vegetation is found in this zone. • Limnetic Zone – This is the zone of lake water, where light reaches in sufficient amount to entire surface area. It means this is not too deep. In this region different types of floating plants (phytoplankton), suspended and submerged plants are present. • Profundal Zone – It is very deep area of the lake where light does not reach up to the bottom. Only heterotrophs are present in this zone. Note : Ecotone – The transition zone in between two communities is called ecotone or tension zone. It has greater number of species & density or it is a transition zone between two communities where one type of community is modifying into another type of community is known as ecotone. Edge effect – Species which occur most abundantly and spend their time in ecotone are called edge species. The tendency to increase variety and density of some organism at the community border is known as edge effect. (b) Stratification in forest :–The clear stratification (vertical arrangement) in various growth forms of plants according to the need of light in any dense forest. Surface dwellers → Herbs → Under shrubs → Shrubs → Trees Note : The clear stratification is found in tropical rain forest. So it is known as multistoried forest. Littoral Zone Limnetic zone Profundal Zone Littoral Zone Stratification in lake community