a group of organisms of different kinds or species living together in a particular place.

assembly of populations of different species in a particular area of a particular time.

a community consists of all plants and animals in a place of a particular time. It is the biotic part of an ecosystem.

It is the biotic part of an ecosystem.

It consists of the producer, consumer and decomposer.

Human Community- refers to all

people, buildings, roads and others in a town or other political unit.

They possess the highest biomass, occupy the most space, make the largest contribution to the flow of energy, and cycling of materials, and exert control over the other organisms in the community.

Trees are the dominants in the forest because they create a climate suitable for certain groups of organisms which set the character of the community.

Numerical abundance is the determining factor of dominance.

… the fundamental role of the organism in the

community --- what it does, its

relation to its foods and to is enemies…

(CHARLES ELTON)

-other definitions of niche-• part of the environment occupied by an organism• the role of organism in the ecosystem as well as its position in time and place• the job of an organism- how it gets its supply of energy and materials• the means of living• functional role- what it does for a living in a community

COMPETITIVE EXCLUSION PRINCIPLE

This concept states that no two species can occupy the same niche at the same time. According to this principle, if two species in the same area occupy the same niche, three things would most likely 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 not completely similar or identical occupy a habitat, one of the organisms will leave the habitat and occupy an adjacent habitat for as long as the organism can tolerate the conditions of the adjacent habitat.3. If two species occupy the same area and are very much similar at first, they develop differences from one another which tend to decrease their competition. This is also known as CHARACTER DISPLACEMENT.

FORESTCOMMUNITY

CANOPYconsists of all tallest trees.

It is the major site of production.

UNDERSTOREY consists of tall shrubsThose that are not able to

withstand the shade and competition will die; others will reach the canopy layer after some of the older trees die or are harvested.

HERB LAYER consist of

the plants shorter than the shrubs.

forest floor consists of leaves,

branches, dead bodies of plants and animals, and other matter which have fallen to the ground.

AQUATIC RESOURCES

A LAKE is stratified into:1. Littoral

zone2. limnetic

zone3. Profunda

zone

The littoral zone is that part of a sea, lake or river that is close to the shore. In coastal environments the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged.

The limnetic zone is the well-lit, open surface waters in a lake, away from the shore

The profundal zone is a very cold and ordinary zone, such as an ocean or a lake, located below the range of effective light penetration.

Blue green algae

In the field of ecology, community composition changes over time. The study of succession

addresses 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 be the local forest, grassland, pond, abandoned farm (or urban lot), park, or even your backyard — and you are likely to observe changes to the organisms found in the community.

New plants may appear and other plants disappear, and these changes may also be reflected in the animal life. These changes may be subtle or obvious, but we can count on communities changing over time in composition, structure, diversity, and productivity. This principle has been exploited by human populations for 1000’s of years, with the manipulation of habitat (e.g., use of fire) to promote the abundance of certain plant and animal species to our benefit. For over a century, ecologists 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

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 in which most, but not all organisms have been destroyed. Lodgepole pines (a) will replace meadows in the absence of fire. Prescribe fires (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,[1] 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 world's 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.

A DESERT BIOME

TUNDRA BIOME