Concept of communities and community interactions, Biology tutorial


Communities are populations of numerous species of organisms living altogether in the similar habitat or environment. The habitats differ from terrestrial to aquatic and so, affect the kinds of communities living in them.

The concept of Communities:

A community is a grouping of populations of numerous species which live in the similar place. The community is dynamic and reflects the evolution and variability of its components. It as well comprises vast interactions between extremely discrete groups.

Coevolution of species within Communities:  

Interactions among organisms which characterize specific communities have arisen as an outcome of their evolutionary history. The animals, plants, protists, fungi and bacteria which live altogether in communities have changed and adjusted to one other continually over a period of millions of years. For illustration, numerous features of flowering plants have evolved in relation to the dispersal of the plant's gametes by animals, particularly insects. Such animals in turn have evolved a number of special features which let them to get food or other resources proficiently from the plants they visit, frequently from their flowers. In predator-prey interactions, carnivore's example: lion have evolved strategies to assist them capture their prey while the prey example: gazelle on their part developed strategies for escape from predation. These are general features which have evolved over millions of years in, for illustration, the grassland communities of Africa.

The long-term evolutionary adjustment of two or more groups of organism which ease the organisms living together is known as Coevolution. It is a method by which various types of organisms adjust to one another through genetic change over long periods of time. 

The stepwise procedure ultimately comprises adjustment of both groups of organisms. Defense methods plants adopt similar to possession of thorns, spines and prickles or of chemical compound to prevent being eaten by herbivores and different chemical defenses of animal's example: venomous snakes, lizards and fishes and also stings from bees, predatory bugs, wasps, scorpions and spiders are different strategies evolved over time for survival in communities.

Coevolution can as well be recognized in the various kinds of symbiotic relations in which organisms have coevolved to the point of dependence.

Types of Communities:

The Biological communities are named according to their positions on land or water. Three main communities can thus be recognized as follows.

1) Terrestrial communities

2) Ocean communities

3) Freshwater communities

A few communities though take their names from physical features for illustration: lakes, rock pools and sand dunes. Specialized communities do as well happen, example: the mammalian gut communities.

1) Terrestrial Communities:

The main terrestrial communities of organisms are structured largely by climate, specifically temperature and rainfall which is in turn affected by the geographical position on the planet. Terrestrial communities are termed as biomes and are simply recognized by their total appearance and features climates. Each biome, categorized mainly by the general characteristics of the vegetation, is alike in its structure and appearance wherever it takes place on earth and distinct considerably from other types of biomes.

2) Ocean or Marine Communities:

Almost three quarters of the earth surface is covered by ocean. A huge wealth of nutrients and biomass are present in the oceans world specifically in warm coastal areas and the planktonic stratum of the surface zone. Around 40% of the world's photosynthetic productivity is estimated to take place in the oceans. Notwithstanding, an anticipated 90% of living species of organisms are terrestrial however representatives of nearly every phylum take place in the sea. Brackish water habitats generally take place between marine and freshwater.

3) Freshwater Communities:

Very little of the earth's water is stored as fresh water in the rivers, ponds and lakes. Freshwater habitats are dissimilar from both marine and terrestrial ones however they are limited in area. Inland lakes cover around 1.8% of the earth's surface and running water covers around 0.3%. All freshwater habitats are strongly joined with terrestrial ones with marshes and swamps comprising intermediate habitats. Ponds and lakes encompass three zones in which organisms take place. The littoral zone is the shallow region all along the shore. The limnetic zone is the well elucidated surface water away from the shore inhabited by plankton and other organisms which live in open water. The profundal zone is the area beneath the limits of efficient light penetration.

The structure of Communities:

Communities are influenced by both the abiotic and biotic characteristics of where they occupy. One of the abiotic characteristics is the water situation, whether the physical atmosphere is fresh water, marine, marsh, drained soil or desert. As well significant are the mineral nutrients, geology and topography of the environment.

The abiotic features help to explain the overall form of communities that is generally determined by vegetation in the terrestrial communities. Plants can encompass different growth forms comprising:

Trees that form forest or woodland communities; bushes that dominate scrub; herbs and grasses which are the main types in grasslands such as savannah or prairie and wet mosses which builds up bogs. This physical structure is not so apparent in the aquatic habitats apart from where calcareous reefs take place.

The total structure of a community is found out by a combination of features like the physical environment, community size and long life of species present. A recently build up community might have only a few species and the number will increase as more species invade and establish. The richness of species of a community is as well affected by features of the community comprising the age of the community, its primary productivity, the form of the organisms present and their competitive capability. A community might be stable or unstable, having high or low primary productivity and might change seasonally or even every day.

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