a group of organisms of different kinds orspecies living together in a particular place. assembly of populations of different speciesin a particular area of a particular time. a community consists of all plants andanimals in a place of a particular time. It is thebiotic part of an ecosystem.
It is thebiotic part ofan ecosystem. It consistsof theproducer, consumer anddecomposer.
HumanCommunity- refers to all people, buildings, roads and others in a town or other political unit.
They possess the highest biomass, occupythe most space, make the largest contribution tothe flow of energy, and cycling of materials, andexert control over the other organisms in thecommunity. Trees are the dominants in the forestbecause they create a climate suitable for certaingroups of organisms which set the character ofthe community. Numerical abundance is the determiningfactor of dominance.
… the fundamental role of the organism in the community --- what it does, itsrelation to its foods and to is enemies… (CHARLES ELTON)
• part of the environment occupied by anorganism• the role of organism in the ecosystem as well asits position in time and place• the job of an organism- how it gets its supply ofenergy and materials• the means of living• functional role- what it does for a living in acommunity
This concept states that no two species canoccupy the same niche at the same time. Accordingto this principle, if two species in the same areaoccupy the same niche, three things would mostlikely to happen: 1. If one species has greater advantage due to greater reproductive capacity or some other factors, the organism will eventually be discarded from that area.
2. If two kinds of organisms which are notcompletely similar or identical occupy ahabitat, one of the organisms will leave thehabitat and occupy an adjacent habitat foras long as the organism can tolerate theconditions of the adjacent habitat.3. If two species occupy the same area andare very much similar at first, they developdifferences from one another which tend todecrease their competition. This is alsoknown as CHARACTER DISPLACEMENT.
CANOPY consists of all tallest trees.It is the major site of production.
UNDERSTOREY consists of tall shrubs Those that are not able towithstand the shade andcompetition will die; others willreach the canopy layer aftersome of the older trees die orare harvested.
HERB LAYER consist ofthe plants shorterthan the shrubs.
forest floor consists ofleaves, branches, dead bodiesof plants and animals, andother matter which have fallento the ground.
A LAKE isstratified into:1. Littoral zone2. limnetic zone3. Profunda zone
The littoral zone isthat part of a sea, lakeor river that is close tothe shore. In coastalenvironments thelittoral zone extendsfrom the high watermark, which is rarelyinundated, toshoreline areas thatare permanentlysubmerged.
The limneticzone is the well-lit, open surfacewaters in alake, away fromthe shore
The profundal zone is avery cold and ordinaryzone, such as an ocean or alake, located below therange of effective lightpenetration.
In the field of ecology, community composition changes over time. The study of successionaddresses this change, which can be influenced by the environment, biotic interactions, and dispersal.
Over the course of several years, you can return to any location — whether it bethe local forest, grassland, pond, abandoned farm (or urban lot), park, or evenyour backyard — and you are likely to observe changes to the organisms found inthe community.New plants may appear and other plants disappear, and these changes may alsobe reflected in the animal life. These changes may be subtle or obvious, but wecan count on communities changing over time in composition, structure, diversity,and productivity. This principle has been exploited by human populations for1000’s of years, with the manipulation of habitat (e.g., use of fire) to promote theabundance of certain plant and animal species to our benefit. For over a century,ecologistshave investigated the nature of these changes in communities, documenting thecauses and patterns of change, indentifying mechanisms for change, anddeveloping sets of general principles to explain this change. This change incommunity composition over time is termed succession. Some definitions alsoinclude adjectives for succession (e.g., Odum 1969) that include“orderly”, “directional,” and “stabilizing.” However, these qualifiers have beenmuch disputed and do not accurately represent the process in most cases
TYPES OF SUCCESSION• have investigated the nature of these changes in communities, documenting the causes and patterns of change, indentifying mechanisms for change, and developing sets of general principles to explain this change. This change in community composition over time is termed succession. Some definitions also include adjectives for succession (e.g., Odum 1969) that include “orderly”, “directional,” and “stabilizing.” However, these qualifiers have been much disputed and do not accurately represent the process in most cases
MODELS OF COMMUNITY• Several models have been developed that describe and make predictions about the successional process. One of the most influential was Frederic Clements’ work from early in the twentieth century (e.g., Clements 1936). Succession was viewed as a deterministic and orderly sequence of serial stages that ended with the climax community. In this view, each stage was composed of a group of species viewed as a super-organism working together and developing on a site that was then replaced by another stage. Ultimately, succession arrived at a climax community, which characterizes the habitat and was viewed as the “expression of the climate”. In contrast, Henry Gleason presented a different view of succession that emphasized individualistic traits (a biotic tolerances and dispersal) of species and their interactions with the environment (Gleason 1926). Species occur together in a location as the result of their a biotic tolerances (niche requirements), not because they are part of an integrated “super organism.” This perspective viewed succession as less deterministic and more reliant on chance dispersal events. One of the consequences is the potential for different successional trajectories resulting in alternative climax communities.
The reestablishment of a community inwhich most, but not all organisms have beendestroyed. Lodgepole pines (a) will replacemeadows in the absence of fire. Prescribefires (b) burned trees in the meadow (c).
THE WORLDS MAJOR COMMUNITIES• Biomes are climatically and geographically defined as similar climatic conditions on the Earth, such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems. Some parts of the earth have more or less the same kind of abiotic and biotic factors spread over a large area creating a typical ecosystem over that area. Such major ecosystems are termed as biomes. Biomes are defined by factors such as plant structures (such as trees, shrubs, and grasses), leaf types (such as broadleaf and needleleaf), plant spacing (forest, woodland, savanna), and climate. Unlike ecozones, biomes are not defined by genetic, taxonomic, or historical similarities. Biomes are often identified with particular patterns of ecological succession and climax vegetation (quasi-equilibrium state of the local ecosystem
– Biomes are defined as "the worlds major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment" (Campbell 1996). The importance of biomes cannot be overestimated. Biomes have changed and moved many times during the history of life on Earth. More recently, human activities have drastically altered these communities. Thus, conservation and preservation of biomes should be a major concern to all.