An Introduction to the Ecosystem

Introduction
The Source of Energy
Food Chains & Trophic Levels
Ecological Pyramids
Biogeochemical Cycles
Ecological Communities & Succession
Immature & Mature Ecosystems
Types of Ecosystems

Introduction

Upon observing any portion of the natural world, it will become evident that none of the organisms inhabiting a region exist in isolation. Each organism interacts with other species and the non-living environment in a variety of ways. The nature and scope of these connections varies from location to location. In every case, however, the interactions of numerous creatures under natural settings result in two outcomes:

Flow of energy through autotrophs (photosynthetic organisms) to heterotrophs (nonphotosynthetic organisms), and
The movement of inorganic materials from the abiotic (non-living) environment to the biotic environment (organisms) and then back to the abiotic environment.

An ecosystem is a complex web of living and nonliving elements through which energy flows and materials recycle. It is a biological community of organisms that interact with one another and their physical surroundings. In a broader sense, the entire biosphere can be viewed as a single ecosystem. This perspective is useful for understanding globally recycled substances such as carbon dioxide, oxygen, and water. On the other hand, an aquarium or terrarium that is properly filled is also an ecosystem. These man-made model ecosystems are useful for investigating ecological issues, such as the recycling pathways of a certain material. The aquarium is an example of an ecosystem created by humans. Most ecosystem studies are conducted on natural ecosystems that are more or less self-contained, such as ponds, swamps, and meadows.

The Source of Energy

Sunlight is the sole source of energy for all natural ecosystems. Here are a few fascinating statistics concerning the sun's energy contribution to the natural world:

A portion of the solar energy that reaches the planet is used to evaporate water.
However, the majority of it is absorbed by the earth's surface layers and radiated back as heat. Only a small portion of the sun's total available energy enters organisms' bodies and fuels their living processes.
Even when intense sunlight falls on dense vegetation, such as in a dense forest, a planted field, or a marsh, just 1-2 percent of it participates in photosynthesis.

The photosynthetic process, which utilises carbon, oxygen, water, and a few minerals, stores the energy in this tiny proportion of sunlight in order to generate organic compounds such as carbohydrates. In other words, autotrophs convert the light energy of sunlight into the chemical energy of diverse organic compounds that serve as a secondary source of energy for heterotrophs.

Both autotrophs and heterotrophs use a portion of the energy they store or consume for their numerous life activities. Only the remainder of the energy is stored in an organism's body and is therefore available for use by other organisms.

Typically, an organism utilises roughly 90 percent of the energy it stores or consumes. Only about 10% is kept in the animal's body.

Food Chains & Trophic Levels

The term "food-chain" refers to the chain of organisms that the stored energy travels along. A trophic (feeding) level is represented by each organism in a food chain. A food chain's first trophic level is always inhabited by one or more autotrophs. It is referred to as the food chain's major producer. All green plants, such as mosses, ferns, grasses, and trees, as well as numerous, mostly aquatic, unicellular and multicellular photosynthetic creatures, are examples of primary producers. Diverse types of heterotrophs occupy the lower levels of the food chain. An herbivore would occupy the second trophic level in the food chain (a heterotroph that feeds on the autotroph occupying the first trophic level). At this level, a heterotroph is referred to as the major consumer. Energy enters the realm of heterotrophs through the main consumer. Caterpillars, leaf ants, field mice, sparrows, cattle, and, yes, even elephants and blue whales are examples of main consumers. A carnivore lives on the third trophic level of the food chain (a heterotroph that feeds on the ones at the second trophic level.) In the food chain, this carnivore is known as the secondary consumer. Spiders, minnows, snakes, lions, robins, and slithers are a few examples of secondary consumers.

There are also third and fourth consumer tiers in some food chains. Five layers is typically the maximum. This is primarily due to the energy loss that is unavoidable when it is transferred from one trophic level to another. To put it another way, of the energy that the primary producers in an ecosystem collectively sequester, only a tenth, a hundredth, and a meagre one thousandth are made accessible to the primary consumers, secondary consumers, and tertiary consumers. At the fifth level and beyond, there is typically little energy left to sustain life. The amount of energy that is accessible decreases in this proportion. The two basic categories of food chains are:

Grazing food-chains are referred to as food-chains that begin with autotrophs.
Detritus (materials resulting from the partial degradation of dead creatures or body parts/excreta of living animals) is a food source for some organisms. Other creatures feed on detritus feeders in turn. Starfish and oyster catchers are two examples. Debris food-chains are those food-chains that begin from detritus.

However, in the natural world, feeding connections rarely take place in a straight chain. These relationships frequently take the form of complicated food-webs since there are organisms that feed on and are fed by members of many species, as well as individuals that occasionally occupy different trophic levels at different periods.

There is also a sizable population of consumers who get their energy from organic matter that is decomposing but not to the point where it can be eaten by other consumers or used as food by producers. This particular category of consumers, primarily made up of bacteria and fungus, is able to secrete enzymes that break down complex decomposing matter into simpler building blocks. Some of these simpler components are consumed as food by the organisms, while the remainder are transformed into forms that allow producers to use them as nutrients. Although these creatures go by a variety of scientific names, including detritivores, saprotrophs, and chemo-heterotrophs, the term "decomposers" is perhaps the one that best reflects their ecological function. The operations of the decomposers have the effect of releasing the matter that has been "imprisoned" in the wastes of the living world, making it once again available to producers and, through them, to the rest of the living world.

Ecological Pyramids

An ecological pyramid is a diagram that shows the quantitative relationships between the trophic levels in an ecosystem. An ecological pyramid could be a pyramid of numbers that displays how many organisms are present at each trophic level. A pyramid of energy that displays the energy available at each trophic level can also be used, as can a pyramid of biomass that displays the total dry weight of all organisms at each trophic level.

It is important to remember that ecological pyramids don't always have to be pyramidal. For instance, a pyramid of numbers representing this ecosystem would have a very small base that widens as we go higher and then narrows again towards the top if the primary producer in the ecosystem is a big tree, which supports a lot of primary consumers who in turn support a lot fewer secondary consumers. Similar to this, an oceanic ecosystem's biomass pyramid is always an inverted pyramid. This is due to the fact that the enormous quantities of tiny phytoplankton species always represent a smaller biomass than the zooplankton or even bigger heterotrophic creatures, like the blue whale, that they nourish. This is made possible by the main producers in issue having a higher rate of reproduction than their consumers. Because the amount of energy accessible always decreases with level, only pyramids of energy are inherently pyramidal. Ecological pyramids often have species at or near the top that are greater in size but fewer in number than those further down. The limited overall biomass and energy available to support them keeps their numbers in control, while their huge sizes aid in capturing and consuming their prey.

Biogeochemical Cycles

Numerous inorganic substances, including water, carbon, nitrogen, oxygen, and phosphorus cycle in ecosystems, in contrast to energy, which only goes in one direction. Among these, air, water, and other gases circulate the most widely. Contrarily, non-gaseous nutrients frequently move around an ecosystem. Ecosystems that are stable often have sufficient supplies of these elements on hand. The term "biogeochemical cycles" refers to such movements of inorganic materials that occur from the geological (atmosphere, hydrosphere, and lithosphere) to the biological (bodies of organisms) and back again of ecosystems. The primary element that is being circulated determines the name of the biogeochemical cycle. The nitrogen cycle is the method by which nitrogen is continuously circulated throughout the living universe.

The nitrogen cycle can be used as an example to highlight the complexity of biogeochemical cycles. The elemental nitrogen that makes up around 78 percent of the earth's atmosphere cannot be used by the majority of species. The inorganic nitrogen-containing molecules that are typically found in soils provide the organisms with the nitrogen they need to create the organic nitrogen-containing compounds necessary to maintain life. This explains why, despite the fact that nitrogen is abundant in the atmosphere, a lack of nitrogen in the soil significantly inhibits plant growth.

A large portion of the nitrogen in soil is produced naturally by soil-dwelling organisms like bacteria and fungi as they break down organic molecules. These organisms release the extra nitrogen as ammonia or ammonium into the soil after using the simple nitrogen-containing compounds that were thus generated for their own purposes. Ammonification is the name given to this phase of the nitrogen cycle. Other types of soil-dwelling bacteria have the ability to oxidise ammonia or ammonium into nitrites and then nitrates. The bacteria utilise the energy released during these activities as their main source of energy, while higher plants can obtain nitrogen from the created nitrates. Nitrification is the name given to this phase of the nitrogen cycle. Prior to being converted into complex nitrogen-containing organic compounds like amino acids and proteins, these nitrates must first be reduced back to ammonium in the plant cells. Assimilation is the name given to this phase of the nitrogen cycle.

Loss of Soil-nitrogen

For a variety of causes, some of the soil-nitrogen that is present in every given ecosystem is lost to the food chains in that ecosystem. The removal of plants from the soil is the principal cause of soil nitrogen loss. This explains why the nitrogen concentration of cultivated soils frequently shows a continuous drop. Additionally, soil nitrogen is lost as a result of burning vegetation, eroding topsoil, and water seeping downhill, which removes nitrogen-containing compounds and transports them outside of the root zone of the vegetation. Denitrifying bacteria break down inorganic nitrogen-containing compounds in waterlogged and thus inadequately aerated soils to get the oxygen necessary for their respiration. Some organisms, primarily bacteria and cyanobacteria, integrate atmospheric nitrogen into organic nitrogen-containing molecules to make up for this constant and inevitable loss of soil nitrogen. Nitrogenfixation is the name given to this stage of the nitrogen cycle. Leguminous plants, such as beans and peas, have roots symbiotically inhabited by bacteria, which fix nitrogen most efficiently. Each year, the earth's soil receives an estimated 90 percent of its nitrogen needs from biological sources, and just approximately 10 percent from human-made chemical fertilisers.

Ecological Communities & Succession

An ecological community is made up of the various living things in a place. One species' population in an ecological community is made up of all of its members. Thus, various constituent populations make up an ecological community. Numerous elements influence how an ecological community is made up. Physical aspects of these elements include things like local soil types, rainfall patterns, and temperature. The many interactions between the individuals or populations that make up the community are examples of biological factors.

Rarely is an ecological community constant. Instead, one community gradually gives way to another. Ecological succession is the name given to this process of societal transformation. The procedure typically follows a systematic and predictable progression. Primary succession refers to an ecological community taking up a dead space. It can be seen on bare ground, such as that left by glacial or volcanic activity, or on a freshly constructed riverbank. Soil formation often begins with the weathering of rocks. If physical factors like light, temperature, and moisture allow it, more complex creatures begin to colonise the soil. Pioneer species are those that are the first living things to populate a lifeless area. Pioneer species alter the local habitat, opening the door for new species to either join or displace the initial invaders. Although the community's species profile is changing quickly at first, it soon slows to a nearly unnoticeable rate. A sere is the collective unit created at each stage of the succession process. A climax community is the one that exists at the end of the process. Secondary succession is defined as succession brought on by the rupture of an earlier seral or climax society. At the scene of a forestfire, after a pasture has been relieved of grazing pressure, or after a field has stopped being farmed, secondary succession may be seen. The climax community will be the same regardless of whether succession is primary or secondary in any location. This is due to the fact that local environmental factors including climate, soil type, and rainfall affect the climax community's characteristics. Ecological succession has considerably fewer stages and a simpler climax community in regions where these variables are particularly unfavourable to life. The climax community is more intricate and varied in regions where these conditions are comparatively less restricting.

Immature & Mature Ecosystems

Ecosystem to ecosystem differs in the many stages of ecological succession, which are influenced by the species in question as well as the rate of change. However, as they move closer to the climax stage, all ecosystems exhibit some common consequences.

Firstly, there is always an increase in the biomass of the ecosystem.
Second, the number of species that make up the community is growing. This expansion of species will unavoidably have some significant effects. One is a higher stratification of primary producers, which results in better use of the various solar wavelengths. The other is a foodweb's intricacy, which leads in a foodweb's improved resilience to environmental changes.

An ecosystem is regarded as being more mature if it produces a bigger amount of biomass and has a more diverse range of living things. Ecological succession, then, transforms an ecosystem from an early to a late stage of development.

Types of Ecosystems

According on whether they are on land or in water, two very general categories are used to classify ecosystems. As a result, there are two different kinds of ecosystems: terrestrial ecosystems, which are found on land, and aquatic ecosystems, which are found in water. The availability of water is the primary distinction between terrestrial and aquatic habitats. Water is a scarce resource in terrestrial habitats, whereas it is abundant in aquatic ecosystems. In comparison to aquatic ecosystems in similar temperatures, terrestrial ecosystems typically undergo larger temperature swings during the course of a day as well as throughout the course of a year. Because light travels more quickly through air than it does through water, terrestrial ecosystems have access to more light than aquatic ecosystems do. In contrast to aquatic habitats, where they must first dissolve in the water to become available to aquatic organisms, terrestrial ecosystems also have simpler access to gases like carbon dioxide, oxygen, and nitrogen.

Terrestrial Ecosystems

Water is a key limiting element in terrestrial ecosystems due to its relative scarcity. Forests, grasslands, and deserts are the three basic categories of terrestrial ecosystems. Let's examine the fundamental variations between each.

Forest Ecosystem: Forest ecosystems have large numbers of trees. Different types of forest ecosystems include tropical evergreen forest, tropical deciduous forest, temperate evergreen forest, temperate deciduous forest, etc.
Desert Ecosystem: Desert ecosystems are found in areas with annual rainfall amounts of less than 25 cm. Such areas have very few trees and a lot of plants, shrubs, and grasses as their vegetation.
Grassland Ecosystem: Grasslands are places where most of the native vegetation is made up of grasses and only a few shrubs and trees.

Aquatic Ecosystems

Marine ecosystems, or aquatic ecosystems based in salt (sea)water, and freshwater ecosystems, or aquatic ecosystems based in sweet water, are the two main types into which aquatic ecosystems can be roughly classified. Either sunlight or nutrients have the potential to become the most significant limiting element in aquatic ecosystems. Light is the most significant limiting factor in the deeper waters of marine environments, such as seas and oceans, because it cannot penetrate water deeper than 200 metres. On the other hand, the majority of the nutrients needed by aquatic species are brought in by runoff from the land and end up on the waterbody's floor. Therefore, nutrients become the most significant limiting element the further one travels into an aquatic habitat from the land, either horizontally or vertically. We need to be aware of the key distinctions between the two aquatic ecosystems.

Marine Ecosystem: The interconnection of the maritime habitats on this planet, which technically merges them into a single large ecosystem, is a significant characteristic of these ecosystems. Another intriguing aspect of marine ecosystems is their dominance on our planet, which accounts for over 71 percent of the planet's surface and nearly 97 percent of its total water content.
Freshwater Ecosystems: Compared to marine ecosystems, freshwater ecosystems are much smaller in size. There are three main types of freshwater ecosystems:
1. lentic ecosystems, which are based in slow-moving or still fresh water, as found in ponds or lakes;
2. lotic ecosystems, which are based in fast-moving water, as found in streams and rivers; and
3. wetlands, which are based in shallow waters where the soil remains regularly saturated with wateron a day-to-day basis