ECOSYSTEM : INTERACTION AND INTERDEPENDENCE

Ecology is the branch of science that deals with the relationship and interactions between organisms and their environment, including other organisms. Ecology includes not only how living things interact with each other, but how they interact with their physical environment: things such as climate, water, and soil.

Biodiversity is the variety of all life forms on earth - the different plants, animals and micro-organisms and the ecosystems of which they are a part.

Ecosystem

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system.  These biotic and abiotic components are regarded as linked together through nutrient cycles and energy flows.  As ecosystems are defined by the network of interactions among organisms, and between organisms and their environment,  they can be of any size but usually encompass specific, limited spaces.

There are two primary types of ecosystems:
• Natural ecosystems: Natural ecosystems may be terrestrial  ( meaning desert, forest , or meadow) or aquatic, ( pond ,river,  or  lake).  A  natural ecosystem is a biological environment that is found in nature (e.g. a forest) rather than created or altered by man.

• Artificial ecosystems: Humans have modified some ecosystems for  their own benefit. These are artificial ecosystems. They can be terrestrial (crop fields and gardens) or aquatic (aquariums, dams, and manmade ponds).

  There are two main components that exist in an ecosystem: the abiotic and biotic components. The abiotic components of any ecosystem are the properties of the environment; the biotic components are the life forms that occupy a given ecosystem.

Abiotic Components

Abiotic components of an ecosystem consist of the nonorganic aspects of the environment that determine what life forms can thrive. Examples of abiotic components are temperature, average humidity, topography and natural disturbances. Temperature varies by latitude; locations near the equator are warmer than are locations near the poles or the temperate zones. Humidity influences the amount of water and moisture in the air and soil, which, in turn, affect rainfall. Topography is the layout of the land in terms of elevation. Natural disturbances include tsunamis, lightning storms, hurricanes and forest fires.

Biotic Components

The biotic components of an ecosystem are the life forms that inhabit it. The life forms of an ecosystem aid in the transfer and cycle of energy. They are grouped in terms of the means they use to get energy. Producers such as plants produce their own energy without consuming other life forms; plants gain their energy from conducting photosynthesis via sunlight. Consumers exist on the next level of the food chain. There are three main types of consumers: herbivores, carnivores and omnivores. Herbivores feed on plants, carnivores get their food by eating other carnivores or herbivores, and omnivores can digest both plant and animal tissue. Decomposers , like fungi and bacteria ,are organisms that break down dead or decaying organisms, and in doing so, they carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development.

Ecosystems are controlled both by external and internal factors :

External factors such as climate, the parent material that forms the soil, and topography control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem.  Other external factors include time and potential biota. Ecosystems are dynamic entities—invariably, they are subject to periodic disturbances and are in the process of recovering from some past disturbance . Ecosystems in similar environments that are located in different parts of the world can have very different characteristics simply because they contain different species. The introduction of non-native species can cause substantial shifts in ecosystem function.

Internal factors not only control ecosystem processes but are also controlled by them and are often subject to feedback loops.  While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.  Other internal factors include disturbance, succession and the types of species present. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate. 

Processes of Ecosystems

The figure on the side, with the plants, zebra, lion, and so forth, illustrates the two main ideas about how ecosystems function: ecosystems have energy flows and ecosystems cycle materials. These two processes are linked, but they are not quite  the same.
Energy that enters the biological system as  light energy, or photons, is transformed into chemical energy in organic molecules by cellular processes including photosynthesis and respiration, and ultimately is converted to heat energy. This energy is dissipated, meaning it is lost to the system as heat; once it is lost it cannot be re-cycled.

Without the continued input of solar energy, biological systems would quickly shut down. Thus the earth is an open system with respect to energy. Elements such as carbon , nitrogen, or phosphorus enter living organisms in a variety of ways. Plants obtain elements from the surrounding atmosphere, water, or soils. Animals may also obtain elements directly from the physical environment, but usually they obtain these mainly as a consequence of consuming other organisms. These materials are transformed biochemically within the bodies of organisms, but sooner or later, due to excretion or decomposition, they are returned to an inorganic state.

Often bacteria complete this process ,through the process called decomposition or mineralization. During decomposition these materials are not destroyed or lost, so the earth is a closed system with respect to elements (with the exception of a meteorite entering the system now and then). The elements are cycled endlessly  between their biotic and abiotic states within ecosystems. Those elements whose supply tends to limit biological
activity are called nutrients.

Interaction

Biotic components and abiotic components of an eco-system interact with and affect one another. If the temperature of an area decreases, the life existing there must adapt to it. Global warming, or the worldwide increase in temperature due to the greenhouse effect, will speed up the metabolism rates of most organisms. Metabolic rate increases with temperature because the nutrient molecules in the body are more likely to contact and react with one another when excited by heat. Accordingly, tropical ectothermic - cold-blooded-organisms could experience increased metabolic rates from an increase of as little as 5 oC because their internal temperature is almost entirely dependent on external temperature. To adapt to these circumstances, cold-blooded life forms could reside in the shade and not actively search for food during daylight hours when the sun is at its brightest.

Different Types of Ecosystems

     There are essentially two kinds of ecosystems; Aquatic and Terrestrial. Any other sub-ecosystem falls under one of these two headings.

Terrestrial Ecosystems

Terrestrial  ecosystems  can  be  found  anywhere  apart  from  heavily  saturated places. They are broadly classed into:

The Forest Ecosystems

They are the ecosystems in which an abundance of flora, or plants, is seen so they have a big number of organisms which live in relatively small space. Therefore, in forest ecosystems the density of living organisms is quite high. A small change in this ecosystem could affect the whole balance, effectively bringing down the whole ecosystem. They are further divided into:
• Tropical evergreen forest: These are tropical forests that receive a mean rainfall of 80 for every 400 inches annually. The forests are characterized by dense vegetation which comprises tall trees at different heights. Each level is shelter to different types of animals.
• Tropical deciduous forest: There, shrubs and dense bushes rule along with a broad selection of trees. The type of forest is found in quite a few parts of the world while a large variety of fauna and flora are found there.
• Temperate evergreen forest: Those have quite a few number of trees as mosses and ferns make up for them. Trees have developed spiked leaves in order to minimize transpiration.
• Temperate deciduous forest: The forest is located in the moist temperate places that have sufficient rainfall. Summers and winters are clearly defined and the trees shed the leaves during the winter months.
• Taiga: Situated just before the arctic regions, the taiga is defined by evergreen conifers. As the temperature is below zero for almost half a year, the remainder of the months, it buzzes with migratory birds and insects.
The Desert Ecosystems
Desert ecosystems are located in regions that receive an annual rainfall less than 25. They occupy about 17 percent of all the land on our planet. Due to the extremely high temperature, low water availability and intense sunlight, fauna and flora are scarce and poorly developed. The vegetation is mainly shrubs, bushes, few grasses and rare trees. The stems and leaves of the plants are modified in order to conserve water as much as possible. The best known desert ones are the succulents such as the spiny leaved cacti. The animal organisms include insects, birds, camels, reptiles all of which
are  adapted to  the  desert conditions.

The Grassland Ecosystem

Grasslands are located in both the tropical and temperate regions of the world though the ecosystems vary slightly. The area mainly comprises grasses with a little number of trees and shrubs. The main vegetation includes grasses, plants and legumes that belong to the composite family. A lot of grazing animals, insectivores and herbivores inhabit the grasslands. The two main kinds of grasslands ecosystems are:
1. Savanna: The tropical grasslands are dry seasonally and have few individual trees. They support a large number of predators and grazers.
2. Prairies: It is temperate grassland, completely devoid of large shrubs and trees. Prairies could be categorized as mixed grass, tall grass and short grass prairies.

The Mountain Ecosystem

Mountain land provides a scattered and diverse array of  habitats  where  a large number  of  animals   and   plants  can  be  found .  At   the  higher   altitudes, the  harsh environmental conditions normally  prevail, and only  the  treeless alpine vegetation can survive.  The animals  that live  there  have  thick fur coats for prevention from  cold  and hibernation in the winter months.  Lower slopes are commonly  covered with coniferous forests.

Aquatic Ecosystems

The aquatic ecosystem is the ecosystem found in a body of water. It encompasses  aquatic  flora,  fauna and  water properties, as well.  There  are  two main
types  of  aquatic  ecosystem- Marine  and Freshwater.

The Marine Ecosystem

Marine ecosystems are the biggest ecosystems, which cover around 71% of Earth's surface and contain 97% of out planet's water. Water in Marine ecosystems features in high amounts minerals and salts dissolved in them. The different divisions of the marine ecosystem are:
• Oceanic: A relatively shallow part of oceans which lies on the continental shelf.
• Profundal:  deep or bottom water.
• Benthic Bottom substrates.
• Inter-tidal: The place between low and high tides.
• Estuaries
• Coral reefs
• Salt marshes
• Hydrothermal vents where chemosynthetic bacteria make up the food base.

Many  kinds  of  organisms  live  in  marine  ecosystems: the brown algae, corals, cephalopods, echinoderms, dinoflagellates  and sharks.

The Freshwater Ecosystem

Contrary to the Marine ecosystems, the freshwater ecosystem covers only 0.8% of Earth's surface and contains 0.009% of the total water. Three basic kinds of freshwater ecosystems exist:
• Lentic: Slow-moving or till water like pools, lakes or ponds.
• Lotic: Fast-moving water such as streams and rivers.
• Wetlands: Places in which the soil is inundated or saturated for some lengthy period of time.
The ecosystems are habitats to reptiles, amphibians and around 41% of the world’s fish species. The faster moving turbulent waters typically contain a greater concentrations of dissolved oxygen, supporting greater biodiversity than slow moving waters in pools.