Factors of Ecosystem [Part 2]

Topographic Factors (Physiographic Factors): Topographic factors include height, direction and the steepness of slope.

1) Height or Altitude: Higher altitude (mountains, hills, etc.) is characterised by low temperature, high velocity of wind, lower atmospheric pressure, high humidity and rainfall. The temperature decreases with the increase of height and the lower temperature favour the formation of clouds and rain. Thus, the mountains and hills are favourable for plant growth and causes different types of forest due to above climatic variations. However, at very high hills and mountains the water vapours directly condense into snow and cause poor vegetation.

2) Direction of the Slope: It is generally observed that the sunward direction of the slope is warmer compared to the opposite, because, the duration of sunlight is longest in sunward direction. It also gets good rainfall. Thus, the sunward directed slope possesses good vegetation whereas the vegetation is poor on the opposite direction due to little or no direct solar radiations.

3) Steepness of the Slope: The steepness of the slope allows rapid flow of rain water and causes water deficit. The rapid movement of water over the slopes cause erosion of the top soil and thus the vegetation disappears from the area. On the other hand plain soil surface sloe the water movement and allows to soak in the soil. It also receives sunlight for long duration. thus the less steepy area is best suitable for plant growth.

Habitat and Niche:

Habitat is the natural place where the organism live. Every population in a community has its own special place to live within the community. The habitat supplies all of the biotic and abiotic elements necessary for the survival of the population. Habitat is the most important of all factors that determines the quality and quantity of life forms in a particular place. it includes a relatively large area such as a pond, forest, grass land, ocean etc. There are normally a number of different microhabitatats within a large habitat. The microhabitats have special conditions suitable for different microhabitats within a large habitat. The microhabitats have special conditions suitable for different organisms, such as muddy bottom of a pond, forest floor, tree canopy, etc. Some populations can live in a variety of habitats, whereas other can survive within only very limited conditions. For example sharks can live only in marine habitat, while Hilsa , a fish can survive in freshwater as well as in marine water. Each organism lives and functions in a particular part of the habitat. This part of the habitat along with its functions is called niche. The niche of an organism means its place in the biotic environment and its relation to food, enemies, habits and abiotic factors. A population of each species within a community has a separate niche. When a niche is occupied by two different species one will be ultimately eliminated through competition.

Biome:

A major terrestrial community of organisms extending over large natural areas is called biome. The biome is based on the life form of the most important plants (i.e. trees, grasses, scrubs) that give to the landscape its special character. The chief character of a biome is depicted by climax communities with their dominant life forms. Seral communities within the region of a biome are considered part of that biome.

• A biome has climax vegetation of a uniform type.
• A biome has specific kinds of plants and animal species.
• A biome is identified by its plant species which influence the animals life.
• A biome is a bigger unit than community, constitute the great regions of the world distinguished on an ecological basis.
• Biomes are not sharply marked off from each other and there are often intermediate zone.

The major biomes of the world are: Tundra, Northern Confier forest (Taiga), Temperate deciduos forest, Tropical rain forest, Chapparal (The mediterranean scrub forest), Tropical Savannah, Grass Land and Desert.

Biotic Factors (Components): The biotic factors include all living organisms present in an ecosystem. These are producers, consumers and decomposers which constantly interact with one another and form an interdependent system. These are grouped in following categories:

a) Producers: The producers are the autotrophic organisms like algae, chemosynthetic and photosynthetic bacteria and all other green plants. They trap solar energy during photosynthesis bacteria and all other green plants. They trap solar energy during photosynthesis and synthesize complex organic food from simple inorganic substances such as CO2 and H2O. Oxygen is evolved as byproduct in the photosynthesis. In aquatic ecosystem algae of various types and other hydrophytes, while in terrestrial ecosystem trees, shrubs, herbs, grasses and mosses are examples of producers. Since they can produce food for all other organisms, they are called the producers.

b) Consumers: These are living members of ecosystem, mostly animals, which feed upon the organic food manufactured by producers. Based on the feeding habit, the consumers are classified into the following types:

i) Primary Consumers: These are the herbivorous animals that totally depend upon green plants for their food. Insects, rodents, rabbit, deer, cow, buffalo, goat, sheep, mouse are some of the common herbivores in the terrestrial ecosystem.

ii) Secondary Consumers: These are carnivorous and omnivorous animals. Carnivorous are flesh eating animals while the omnivores are adapted to consume both plants and herbivores as their food. These are fox, jackals, snakes, frogs, lizards, birds, dogs, cats, crow, etc.

iii) Tertiary Consumers: These are the top carnivores which prey upon other carnivores, omnivores and herbivores. Lions, tigers, hawk, vulture, etc. are considered as tertiary or top consumers.

c) Decomposers: These are mostly fungi and bacteria. They attack the dead body of plants and animals and degrade the complex organic substances into simpler compounds. Thus, the decomposers convert complex organic matter into the inorganic forms that are suitable for reuse by green plants and play an important role in maintaining the dynamic nature of ecosystem.

Interaction between Biotic Factors (Community): Various species of biotic community live together in the same environment and interact with each other for food, shelter and habits. They show positive as well as negative interactions:

1) Positive Interactions:

a) Mutualism (Symbiosis): When two species live together in a close association and they are benefited from each other, the relationship is called mutualism. In such association there occurs a close and permanent contact. In some cases they show obligatory contact, i.e. essential for survival of each. For example: lichen is an association of algae and fungi. The algal partner produces food both for itself and fungi. While the fungal partner provide fixation, protection against dessication and absorption of water and minerals for the lichen. Another best example is association of nitrogen fixing bacteria in the root nodules of leguminous plants. Rhizobium bacteria provide nitrates to the leguminous plant. In turn bacteria get organic food from leguminous plant.

b) Commensalism: It is an association of two species where one organism is benefited while the other organism is neither benefited nor harmed. The association of sea anemone (Adamsia) and the hermit crab (Eupagurus) is the best example of commensalism. The sea anemone (sedentary animals) gets attached to the body of hermit crab. Sea anemone is carried from one place to another by hermit crab which help for their feeding purposes. The hermit crab remains unaffected. The epiphytes such as orchids are plants growing on other plants. They use other plants only for support. They manufacture their own food by photosynthesis.

c) Protocooperation: It is less extreme sort of interaction than mutualism, where both the species are benefited. However, it is not obligatory i.e. not essential for either species. The relationship between water snakes and large birds (herons and ibises) on several islands of the west coast of Florida is the best example. The birds nest in the lower climbing branches, while the snakes congregate around the base. This protects the bird from tree climbing predators such as racoons. In turn, the snake feed on fish dropped by the birds and occasionally baby birds that fall out of the nest.

d) Colonization: A group of animals of the same species living together and dependent upon each other. Some, such as the corals and sponges are physically connected and function as a single unit.

e) Social Organization: There are many example of social organization, where division of labour seen among the individuals in the population. Such organization is exhibited by bees, ants , wasps, termites among insects, certain fishes and birds. The honey bees are social insects and live in a highly organized colony. Excellent division of labour is exhibited by these bees. The colony consists of three types of bee: (i) a functional female or queen (ii) males or drones (iii) sterile females or workers. They work in coordinate manner for the welfare of colony.

f) Aggregation: It refers to the tendency among animals to concentrate in large numbers by their own movements. Aggregation of animals have some survival significance- as hundreds, sometimes thousands of spotted lady beetles hibernate under leaves at the forest edge. Millions of bats roost together in large caves. the migratory locust moves from one locality to another in immense hordes, and birds usually migrate in groups.

2) Negative Interactions:

a) Predation: This is a direct interaction of two species, in which one organism kills another for food. The species that captures, kills and eats up is called predator or enemy and that which is caught is called the prey. Generally, predator is larger and stronger than its prey. For example: Tiger feeds on deers, snake feeds on frog, etc.

b) Parasitism: A parasite is the organism which live on another organisms. They get their nourishment from host body. It is one sided relationship in which parasite gets benefited and the host is always harmed. A large number of organisms grow as parasite on other organisms. They absorb their food causing diseases and serious damage to the host. Several species of fungi, bacteria, arthropods and viruses are well known parasites. They live as parasite and cause disease to plant, animal and man.

c) Competition: Competition refers to the type of interaction in which two individuals or species compete for a limited resource. They share the same resources like water, nutrients, space, sunlight, food, etc. Competition is maximum among the individuals of the same species, because of the similar requirements and adaptations. Competition also occurs among the individuals of different species. This is best seen in crop fields, where, if the weeds are not removed, they dominate the crop plants and reduce their yielding capacity. Similarly, animals like tiger and lion compete for the prey.

d) Antibiosis: The term 'antibiosis' generally refers to the complete or partial inhibition or death of one organism by another through the production of some substance or environment conditions as a result of metabolic pathways. Here none of them derives any benefit. The phenomenon of antibiosis is much common among microbial world. The production of antibiotics is well known among microorganisms, which inhibits the growth of other microorganisms.

The Ecosystem: The term ecosystem was coined by A.G. Tansley (1935), who defined it as "The system resulting from the integration of all living and non-living factors of the environment is called ecosystem. Eco means environment and system means an interacting, interdependent complex. According to woodbury (1954), ecosystem is a complex habitat in which, plants and animals are considered as one interacting unit, the materials and energy of one passing in and out of the others. Ecosystem consists of a community of organisms and the non-living components of the habitat interacting with each other. The living communities in a given area interacts with the physical environment and exchange material among themselves. Such a natural unit in which biotic and abiotic components interact exchanging materials between them to form a self-regulating system is called ecosystem. It is a complete, self-sufficient ecological unit. It may be natural like a forest or artificial like an aquarium. An ecosystem may thus be as small as an aquarium , a pond, a cropland or as large as an ocean, desert or forest. These unit ecosystems are simply separated from each other with time and space, but functionally they all are indeed linked with each other, forming as an integrated whole. There exists practically no functional boundaries between them.

Organisation of the ecosystem (Structural and functional): The two major aspects of an ecosystem are the structure and function. Te structure of an ecosystem is basically a description of the organisms and physical features of environment including the amount and distribution of nutrients in a particular habitat. It also provides information regarding the range of climatic conditions prevailing in the area. While the functional aspects of ecosystem describe the flow of energy and the cycling of nutrients.

Structure of Ecosystem:

1) Abiotic (non-living) Component: These are inorganic compounds and organic compounds of the environment. The organic compounds are carbon dioxide, water, nitrogen , calcium, phosphate, all of which are involved in matter cycle (biogeochemical cycles). The organic components of an ecosystem are carbohydrates, proteins, lipids and amino acids all of which are synthesized by the producers. Producers (green plant) absorb inorganic compounds from the soil. These inorganic substances are utilized in the formation of organic food. From green plants these organic foods are passed on to the consumers. Lastly, upon the death and decay, decomposers attack the dead body of plants and animals and decompose the complex organic matter into simple organic compounds. Thus, inorganic and organic substances circulate in the ecosystem between biotic components and environment. Abiotic components also include light, temperature, wind, gases, rainfall, soil, etc.

2) Biotic Components: The biotic components include all living organisms present in an ecosystem. These are grouped in following categories:

a) Producers: The producers are the autotrophic organisms like algae, chemosynthetic and photosynthetic bacteria and all other green plants. They trap solar energy during photosynthesis and synthesise complex organic food from simple inorganic substances such as CO2 and H2O. Oxygen is evolved as byproduct in the photosynthesis. In aquatic ecosystem algae of various types and other hydrophytes, while in terrestrial ecosystem trees, shrubs, herbs, grasses and mosses are examples of producers. Since they produce food for all other organisms, they are called the producers.

b) Cosumers: Primary, secondary and tertiary consumers.

c) Decomposers: Fungi and bacteria are most common decomposers. They bring nutrients back into the soil.