What is an ecosystem?
A simple definition of an ecosystem is a group of interacting organisms both living and non-living, that inhabit a particular place known as the habitat. It can also be described as a community of living and non-living entities that co-exist and affect each other either directly or indirectly.
Etymologically the word ecosystem is derived from the Greek word “Oikos” which translates to home, and “systema” meaning system. Ecologists from the nineteenth and early twentieth century knew about the complex interdependence of living and non-living matter.
They came up with terms to best describe the existing conditions. Terms like biosystem, geobiocoenosis, biocoenosis, microcosm, and holocoen. A British ecologist A.G. Tansley proposed the term ecosystem in 1935. Seven years later in 1942, Raymond L Lindeman came up with the definition that is widely used even today.
His interpretation submits that an ecosystem’s mainspring is energy flow through several trophic levels; ensuring the transformation or transmutation of material from one state to another. Therefore a food chain will consist of several relays that non-living matter (i.e. gaseous, liquid or solid) is turned into living tissue by plants. These are subsequently digested by phytophagous animals (i.e. insects); who in turn are consumed by carnivores that may also end up consumed by other carnivores.
The 2 Components of an Ecosystem – Biotic and Abiotic Factors
The two components of an ecosystem are categorized based on living and non-living bodies. These components can be termed biotic and abiotic factors; they interact with each other in a habitat. The living components are the Biotic factors while the non-living components are the Abiotic factors.
Biotic components or factors are the living organisms within an ecosystem, that interact with the rest of the system. They do this when they take and give out resources; the biotic factors can physically affect and be affected by the same ecosystem. These actions are generally carried out when the organism either; forages to feed, locomotes, mates, molts, competes with others or modifies the environment. Pathogens and diseases are also part of the ecosystem. These biotic factors are located in the part of the ecosystem known as the biosphere. The biosphere is simply the habitat of living organisms in an ecosystem.
Biotic factors of an ecosystem can be sub-divided into three main parts namely: producers, consumers, and decomposers.
Also referred to as autotrophs or primary producers; these biotic members are at the bottom of the food chain. They play an important role in the ecosystem as they undergo photosynthesis converting solar energy to food. They also supply most of the nutrition that the consumers consume. Autotrophs have the ability to produce complex organic compounds like fats, carbohydrates, and proteins using carbon from simple substances like carbon dioxide. They use energy from light by a process known as photosynthesis to make their own food, and can also use inorganic chemical reactions through chemosynthesis for food production. The producers of an ecosystem convert light from the ecosystem into energy stored in organic compounds which can be used by other organisms like the heterotrophs.
The consumers in an ecosystem are also known as heterotrophs. They are higher organisms that cannot naturally produce their own food but get their own nutrition from other sources of carbon mostly plant and animal matter. The heterotrophs can be primary, secondary, or tertiary consumers in the food chain but not producers. Heterotrophic living organisms include all animals, fungi, some bacteria, protists, and many parasitic plants.
Heterotrophs are further subdivided according to their source of energy. Those that use chemical energy like humans and mushrooms are called chemoheterotrophs. While those that use light for energy such as green non-sulfur bacteria are called photoheterotrophs.
These are organisms that act on, and break down other organisms that are either dead or decaying. They achieve this through a process called decomposition. Decomposers are heterotrophic like the consumers and use organic substrates to get their energy, nutrients, and carbon for growth and development.
There are a number of organisms that act on dead matter in aid of decomposition.
Some decomposers carry out decomposition by saprotrophic nutrition; (absorbing and metabolizing matter on a molecular scale). These include many different types of bacteria, fungi, and protists.
Some decomposers are heterotrophs and like many different vertebrates, invertebrates, and plants, carry out coprophagic nutrition (consumption and digestion of fecal matter). They are called detritivores.
Detritivores, also called detritus feeders, detrivores, or detritophages like arthropods, carry out coprophagy (feeding on fecal matter). They are similar to decomposers in that their action also results in the decomposition of matter; however, unlike true decomposers who get their nutrition by saprotrophic nutrition (first decaying the matter before absorbing it), the detritivores must ingest the detritus before it can be decomposed.
Detritivores help in the decomposition of organic matter into smaller partially decomposed particles known as Detritus. After the first stage of decomposition to detritus, the organic molecules are released into the ecosystem by the primary decomposers.
Therefore, detritivores and primary decomposers, work together to reintroduce organic resources back into the ecosystem (soil or water) through their process of breaking down plant matter into fragments. This makes it easier for the true decomposers’ action of absorption to take place at the second stage of remineralization.
The abiotic components of an ecosystem are those factors that do not hold life but have a physical or chemical effect on the living organisms and the functioning of the rest of the environment.
Abiotic factors of an ecosystem affect all other factors and organisms because it includes the very medium in which everything else exists. They are part of the environment because they include such physical parts as the atmosphere, the climate, and even the land/oceans,
Non-living resources, physical environment, and conditions are part of abiotic components that affect living organisms. They are affected in areas of growth, level of well-being, and success or failure of reproduction. Degradation of solid parts of abiotic factors occurs solely through chemical or physical processes.
Types of Ecosystems
There are three main types of ecosystems. Two are naturally occurring and are the source from which the remaining six sub-types of ecosystems are derived. One type is a man-made or artificial type of ecosystem. They are as follows:
A forest ecosystem is a community of all organisms both arboreal(in the trees and roots) and terrestrial(forest floor) including plants, animals, and microbes that interact with the physical and chemical components of a community that is dominated by numerous trees close to each other; even though there are many different trees in a forest, several of the trees will be of the same species due to successful self-propagation.
The branches and leaves often form a continuous canopy that can cover vast areas. This canopy limits the amount of sunlight reaching the forest floor thereby limiting the population of the vegetation that can thrive beneath the canopy. This is why there is a much lighter concentration of greenery under the canopy layer. There are however a range of different plants, animals, and microbes that habitate and even thrive at different parts of the structure of the canopy in these forest ecosystems
Structure of the Forest Canopy of a Forest Ecosystem
The tree has the basic structure of roots at the bottom leading up to the stem and from there the crown which holds the branches, shoots, leaves, and fruits. The forest canopy structure of the terrestrial ecosystem can be basically described as the arrangement of the crests or crowns of trees in a large group of trees. The forest canopy structure influences and is influenced by environmental and soil factors. It has a structure that can be described as being made up of three components, although it is one structure being analyzed from three different perspectives. The structure of a forest canopy in a forest ecosystem contains several sub-structures and different life forms.
The three main structures are:
- The vertical structure: This is made up of seven layers from below to the top as follows: The soil layer, forest floor, shrub layer, understorey layer, sub-canopy layer, canopy layer, and the emergent layer.
- The horizontal structure: This is the part of the forest that runs across the mid-to-upper areas of the vegetation on the horizontal plane. Its created by the placement of trees and how close their crowns are to each other.
- The stand structure: The stand structure refers to the overall look of a forest stand. This can be briefly described as a cross-sectional profile or a side-sectional view of a forest. It looks at a combination of the vertical and the horizontal distributions of a stand or section of a forest canopy structure.
This look at the vertical and horizontal distributions of a section of the forest includes; the height, diameter, crown layers, stems of trees, shrubs, herbaceous understorey, snags, and down woody debris.
The stand structure of a forest ecosystem can also be defined as the distribution of trees by species and size within a stand. It may be determined by a few factors such as:
- Growth habits and characteristics of a tree species with attention to the level of shade tolerance.
- General and specific ecological conditions present.
- History of disturbance, distribution, and management.
There are different cultural classes that stands can be grouped in. However, there are three common stand structure classes are as follows:
- Evenly-aged stand: Trees that are of the same age due to being planted around the same time on the same day; germinated at the same time. Trees that were planted roughly around the same period or were germinated within a short period of each other. Small age differences are generally not considered practically significant.
- Unevenly-aged stand: Stands that consist of mixtures of species and ages without any clear distinction between them.
- Multi-aged stand: The multi-aged stands are intermediate and fall between the aged and unaged stands. Two or more age and species groups can be found within this category of stand although the boundaries may not be clearly defined. Stands where regeneration is occurring in patches that were opened in the stand either by timber harvesting, dying of old trees, or any other event that caused the death or removal of trees in a given area.
The Vertical Structure
The vertical layers of a forest canopy structure of a forest ecosystem are formed because trees, shrubs, and creepers in a forest will have different rates of growth, varying nutritional and climatic requirements resulting in different levels of shrub, plant, and tree heights. The limited amount of light reaching the parts of the forest ecosystem below the canopy layer also plays a major role in determining the stratified nature of that ecosystem. This is the reason two or more tree-crown layers can be found in forest analysis.
These layers are termed forest layers or strata.
The Emergent Layer
The topmost layer is the emergent layer. It is made up of the tallest trees in the forest averaging approximately ranging between (35m to 65m) depending on the area. Sometimes the emergent trees can even grow taller; ranging up to (70 to 80 meters).
The lowland dipterocarp rainforests of Malesia (Malaysia and Indonesia geographical regions) generally have the tallest rainforests in the world particularly with consideration for the emergent layer. They are less dense in that are typically sparsely distributed with not more than one or two per hectare of forest space.
These trees that make up the emergent layer have access to an abundance of sunlight due to their height, and an abundance of moisture due to increased precipitation from the forest density. The emergent stratum typically has crowns (branches, leaves, flowers, and fruits) that do not come close or make contact with neighboring emergents due to the significant distances between them.
There are some living organisms that can be found even here; although not too many thrive or permanently habitate such heights due to the hazards associated with such locations.
Advantages and Disadvantages of the Emergent Layer
There are advantages of being at the height of emergent trees like access to abundant sunlight and space to expand. However, there are several disadvantages and hazards of being at that altitude that limit the population of organisms that habitate there. These include The full heat of the sun throughout the daylight hours, exposure to lightning, exposure to strong winds, and other extreme and potentially damaging weather and climate conditions like hail storms.
Despite the emergent layer of the vertical structure of the forest canopy ecosystem being exposed to the potentially hazardous elements, some organisms can still be found there. Organisms such as some parasitic plants, some species of birds that favor high nesting like the eagle, and other birds of prey, bats high-climbing rodents like the flying squirrel, several insects including the butterfly, moths, bees and wasps, arachnids, polypores (bracket fungus), epiphytes (numerous ferns, bromeliads, air plants, and orchids), vines and a few primates like some species of monkey, orangutan, and sloths.
The canopy layer or canopy stratum is just below the emergent layer usually about (25 to 40 meters)above ground level. The whole structure derives its name from this layer because it is the most extensive and dense part of the forest ecosystem. This layer is usually the only one that is continuous throughout the expanse of that particular forest ecosystem.
The canopy layer is made up of the crowns of most trees, which are usually of a similar height and girth. The closeness and similar or sometimes matching heights allow for the proximity and in many cases, the close contact the crown areas have with each other.
The crown of these trees usually seem to merge into each other as they form this canopy in a continuous sea of leaves and compete for light; however, there is a phenomenon that sometimes occurs termed crown-shyness.
Crown-shyness is a natural occurrence in a forest ecosystem where the crowns of neighboring trees stop just short of making contact or merging their respective branches and leaves but leave a noticeable gap. This phenomenon usually occurs with neighboring trees of the same species.
In some instances, some of the lower hanging branches from the emergent layer make contact or come within a few feet or less of the canopy layer allowing for easy movement between the two layers by arboreal-dwelling organisms and animals.
This closeness is what forms the continuous canopy layer and supports many life forms like insects, birds, some marsupials, other mammals like bats and monkeys, and other life forms. The canopy layer leaves, vines, climbers and epiphytes, also trap most of the sunlight and much of the moisture that falls on the forest ecosystem.
This helps to create its own microclimate providing shade, nourishing and fertilizing the nooks and crannies of the tree crowns with fallen leaves and branches. It also enables many organisms and animals the ability to move between trees and feeding along large areas without descending to the ground.
The layer just below the canopy layer is called the sub-canopy layer. It consists of mainly juvenile trees and those adapted to living in the shade or limited sunlight, bare branchless trunks of larger trees, and climbers that are creeping upwards.
Typically this layer is between (5 to 20 meters) above ground level but just below the lower branches of the canopy layer. Living organisms can also be found here including animals like the Malayan colugo (Galeopterus variegates) and the Paradise tree snake (Chrysopelea paradise)
The Understorey Layer
The understorey layer is the stratum just below the sub-canopy layer. It consists of plants that have just managed to grow beyond the preceding shrub layer. The plants in this layer also grow very slowly because of the limited sunlight that reaches them. They include many species from the lower layers like climbers shade-tolerant palms and ferns
The shrub layer is the last stratum that has some elevation from the ground layer. This layer is full of a variety of different plants and animals. Virtually all the vegetation that have root systems that are in the ground; and not growing from nooks or gaps in trunks or certain parts of other trees, are found here. There are shrubs, flora such as palms, saplings, seedlings, ferns, and even the occasional cycad.
Many organisms and smaller animals from the ground layer can be found foraging at the shrub level. They include species like caterpillars, ants, termites, beetles butterflies, rodents, snakes, etc.
The Ground layer.
As the name suggests this is the forest floor, terra firma, and supports the rest of the strata. All the trees and other numerous plants that have roots in the ground are found here. The various herbs and plants that are found here are all shade-tolerant and have a very slowed rate of growth which can occasionally be accelerated from a gap in the canopy caused by a falling tree.
This makes the ground stratum very busy with the whole space covered with most of the plants from the shrub layer and several that don’t grow far beyond a few inches off the ground. There are seedlings, saplings, and all sorts of plants fungi, and animals here.
The ground layer is the most biodiverse in the whole structure. It is full of an abundance of different living and decomposing organisms. Thick piles of leaves branches and fallen trees and shrubs litter the entire area and there are thousands of termites, ants, worms, larvae, rodents, reptiles, large and small animals that inhabit the ground layer
The soil Layer
Just below the ground layer is the final section of the forest canopy structure, the soil stratum which contains the roots of all the ground-rooted vegetation and burrowing wildlife. Organisms like bacteria, nematodes, crickets, termites, moles, snakes, and many others inhabit this layer.
The Horizontal Structure
The horizontal structure refers to the spatial distribution of trees, other vegetation, and large deadwood across a stand. In some extreme cases, evenly-aged plantations have uniform horizontal structures with an even distribution of trees, canopy cover, understory vegetation, and forest floor conditions.
Savanna/grassland ecosystems are made up of areas that have large expanses of land dominated by grass-covered plains with a few trees and shrubs scattered around although the density of trees may vary depending on the region in question. Notable examples are the tropical savanna ecosystems of Africa and Australia.
Grassland/savannahs are tropical biomes that are characterized by warm all-year-round temperatures with their highest rainfall in the summer. There are numerous living organisms in this ecosystem. It contains the largest variety of big herd animals in any ecosystem. It is also here that the largest and furthest ranging animals can be found.
Examples of animals found in a savanna ecosystem are; the lion, the elephant, wildebeest, badgers, birds, elephants, snakes, insects, wild dogs, hyenas, giraffes, nematodes, rhinoceroses, gazelles, deer, big cats, and zebras among many.
There is usually an abundance of grass and though there are some large trees, they are never grouped close enough to form a closed canopy. The open canopy allows plenty of sunlight to reach the ground allowing herbaceous plants to thrive.
The Sahel Region of the Savannah
Grassland ecosystems which are estimated to make up 20% of the global land are also characterized by the seasonal availability of moisture and water. Rainfall only significantly occurs during the wet season.
Savannahs are generally between the desert biome and the rainforest biome.
The tundra biome is the coldest ecosystem that supports some life. It is characterized by low year-round temperatures, an absence of trees, the presence of permafrost, low precipitation, a short growing season, and long, cold winters with high winds.
Tundra can be found in two distinct cold and dry regions.
Arctic tundra is located on high-latitude landmasses above the Arctic Circle which includes; Russia, Alaska, Canada, Scandinavia, Greenland, Iceland, and Antarctica.
Alpine tundra is found at very high elevations on top of mountains and though they are below the Arctic Circle, the overnight temperatures can still fall several degrees below freezing. Some large regions of alpine tundra occur in; the North American Cordillera, and part of the northern Appalachian Mountains in North America, the Alps, and Pyrenees of Europe, the Himalaya, the Karakoram in Asia, the Andes of South America, the Eastern Rift mountains of Africa, and the South Islands of New Zealand.
Tundra regions typically receive less than 25 centimeters (10 inches) of precipitation annually. This somewhat categorizes them as deserts. The biodiversity in the tundra is low.
In addition to long cold winters and high winds, tundra regions average temperatures below freezing for six to ten months of the year. Averagely only six to ten weeks in the whole year are warm enough and have sufficiently long enough days to allow for plant growth.
Permafrost of the tundra ecosystem
The soil found in tundra ecosystems is mostly frozen virtually all year round a natural phenomenon termed permafrost. This leaves very little usable soil for plants and microorganisms to thrive on which is why tundra ecosystems have only very few organisms plants and animals present; except the low number of them that have the ability to adapt.
The plants in the tundra are made up of low-to-the-ground patchy vegetation. This sparse and light vegetation is made up of shrubs that have been able to adapt to harsh conditions like small tufts of certain types of tough perennial grass, forbs, cushion plants, mosses, sedges, and lichens.
The animals that can be found in tundra ecosystems also have to be able to adapt to the harsh conditions. They must make maximum use of the few weeks of the growing season to hunt and forage. This is to get as much nourishment as possible before the temperature drops too low for the growth and decomposition that drives the food chain.
Some of these animals include; small mammals like Norway lemmings (Lemmus lemmus), arctic hares(Lepus arcticus), arctic ground squirrels(Spermophilus parry), and large mammals like caribou(Rangifer tarandus).
Many of these animals accumulate fats during the short summer so that they can sustain themselves during hibernation or migration during the long winter months
The desert biome or ecosystem covers one-fifth of the Earth’s surface. This is in terms of total collective area. This biome typically has a dry layer of sand, gravel, or rocks depending on the type of desert, location, or region.
Deserts usually only get about 50 centimeters (20 inches) of rainfall in a year but several organisms, plants, and animals have adapted to survive under these dry and harsh conditions.
Plant Adaptation in a Desert
Plants have evolved many adaptations to survive the harshness of the desert. There are three main types of plants that have adjusted their characteristics(adapted) to living in the desert. They are as follows:
- Ephemeral annuals. These plants, also known as drought evaders that germinate, grow, flower, and release seeds within a short time. (6 to 8 weeks)
- Succulents. Succulent and fleshy stems, leaves, and roots help this plant to retain a maximum amount of moisture.
- Desert shrubs. Also called non-succulent perennials, their morphological and physiological adaptations include rapid elongation and extensive root system, high osmotic pressure, and endurance of desiccation. Also the ability to reduce transpiration.
Animal Adaptations in Desert Ecosystem
Animals of the desert ecosystem are more affected by the extreme desert climate conditions than plants especially temperature. The reason is that the biological processes of animal tissue function properly within a notably narrow temperature range.
This is the reason that most desert ecosystem-dwelling animals rely mostly on their behavioral, physiological, and structural adaptations to avoid desert heat and dryness.
Drought-resistant animals are active throughout the year. They can work around the arid and hot weather through morphological and physiological adaptations or by modifying their feeding and activity patterns.
They remain in their relatively cool and hidden underground burrows during the day when temperatures are high and only emerge to forage and hunt at night when temperatures are cooler.
Four main types of deserts are classified according to the predominant climate conditions that are found in each desert region.
Types of desert ecosystems
- Hot and dry/arid desert
- Semi-arid desert
- Coastal desert
- Cold deserts
Hot and dry/arid deserts
In hot, dry, and arid deserts the temperatures are hot year-round and they have low annual precipitation. Low levels of relative humidity in arid desert ecosystems contribute to high daytime temperatures and extensive nighttime loss of heat.
Arid deserts are physically characterized by vast landscapes of plains, mountains, valleys, dunes of different sizes, sparse vegetation and rocks, oasis, and a few rock outcrops. They are covered with an abundance of dry, loose sand that has low water retention.
The thick layers of sand in arid deserts make the surfaces mobile and unstable. The loose sand gets blown into large sand dunes and sand storms frequently.
The average annual temperature in hot deserts is roughly 20 to 25°C. However extreme weather and climate conditions can lead to temperatures ranging between -18° to 49°C.
Rainfall is usually followed by long periods of dryness when resources and nutrients become very scarce. Despite the harsh environmental condition, the hot desert ecosystem has a surprising amount of biodiversity.
Those plants, animals, and other organisms that thrive have undergone morphological, anatomical, behavioral, and physiological adaptations to survive under such harsh conditions.
Plants that can be found in an arid desert ecosystem include:
- Barrel cactus
- Pancake prickly pear cactus
- Creosote bush
- Desert ironwood plant
- Organ pipe cactus
Animals that can be found in an arid desert ecosystem include:
- Fennec foxes
- Dung beetles
- Bactrian camels
- Sidewinder snake
- Mexican coyotes
- Thorny devil lizard
Semi-arid deserts have similar climatic and topographic conditions to the arid deserts except that it is less extreme. Temperatures generally range between 10° to 38°C. They generally have fewer dunes than arid deserts and have larger rocks and harder more stable ground.
Rainfall is slightly more prevalent in the semi-arid deserts receiving between 250mm to 500mm annually.
Plants that can be found in semi-arid deserts
- Brittle bushes
- Bur sage
- Creosote bushes
- white thorns
Animals that can be found in semi-arid ecosystems
- Kangaroo rats
- Burrowing owl
Coastal Desert Ecosystems
The coastal desert ecosystems are more hospitable than the other desert types both in terms of temperature and rainfall. They have many of the attributes of the other desert types like an oasis, dunes, etc, but in addition, they have beaches because they are located near bodies of water.
The average temperature of the coastal desert ecosystem ranges between 13°C to 24°C in the summer and 5°C and below in the winter.
Rainfall averages 37centimeters at the peak and 5 centimeters as the least amount.
The soil is moderately textured with moderate salt content.
Some plants that can be found in a coastal desert ecosystem are:
- Black bushes
- Black sage
- Buckwheat bushes
- little leaf horsebrush
- Rice grass
- Salt bushes
Animals that can be found in coastal desert ecosystems are:
- A range of insects
- Different species of birds
Cold Desert Ecosystem
Polar or cold deserts are located in the earth’s two polar regions. The North Pole and the South Pole. They are characterized by year-round cold, dry and snowy conditions.
The topographic conditions of the cold desert ecosystems differ from the other three which have similar physical features. The polar deserts have flat plains with snow dunes and areas with icebergs.
Temperatures are similar to that of the coastal deserts but significantly colder. Summer temperature is between 21°C to 26°C and winter temperatures range between -2°C and 4°C. Winters are generally very long in polar deserts.
The soil is heavy, silty, and salty. The drainage of the soil is good and leaches some of the salt it contains. This makes the water bodies around polar desert ecosystems to be salty and not freeze often.
The soil of the polar desert is permafrost most of the year.
Rainfall and snowfall vary through the seasons. Although snowfall occurs mostly in winter, it can also occur during the summer. Similarly, rainfall mostly occurs in the summer but can also occur during winter. The average precipitation is below 250mm annually.
Plants that can be found in a cold desert are mainly deciduous. They include:
- Grasses (bunchgrass)
- Camel’s thorn
- Rubber rabbitbrush
- Prickly pear
Animals that can be found in a cold desert
- Arctic fox
- Rock ptarmigan
- Fennec fox
- Kangaroo rats
An aquatic ecosystem is a self-sufficient community of biotic and abiotic factors that are interdependent, interact and exist underwater or inside a body of water.
There are two basic types of aquatic ecosystems namely:
- Marine ecosystems
- Freshwater ecosystems
The marine ecosystem is by far the largest of all the types of ecosystems on earth. They cover about 71% of the earth’s surface and hold 97% of the world’s water. They generate 32% of the world’s primary production.
Marine ecosystems are distinguished from freshwater ecosystems due to the dissolved compounds in the water which are mostly salts. Roughly 85% of the dissolved minerals in marine oceans are sodium and chlorine.
Marine ecosystems include oceans and seas and can be categorized into several zones depending on shoreline features and water depth.
The oceanic zone
This is the larger part of the marine ocean where the majority of the large aquatic animals like whales sharks and tuna are found.
The benthic zone
The benthic zone is made up of substrates below water where a large number of invertebrates live.
The intertidal zone
These are parts of the oceans that fall in areas between high and low tides.
Other near-shore neritic zones are mainly made up of estuaries, salt marshes, coral reefs, lagoons, and mangrove swamps. Hydrothermal vents may sometimes occur in water that is deep where chemosynthetic sulfur bacteria form the bases of the food web.
In marine and some cases, freshwater ecosystems, the distinction between plant organisms and animals can sometimes become hard to distinguish.
Examples of plants that can be found in a marine ecosystem/biome
- Brown algae
- Sea anemones
- Sea cabbage
Examples of Animals found in marine ecosystems
- Assorted mollusks
- Assorted fish
0.78 percent of the Earth’s surface is covered by freshwater. It is distinguished from marine water by the absence of dissolved compounds especially salt. Freshwater makes up about 0.009 percent of the world’s total water. They generate almost 3% of the Earth’s net primary production.
Freshwater accounts for 41% of the world’s known fish species.
Three basic types of freshwater ecosystems exist in nature:
- Lentic: Slow-moving water bodies including; ponds, pools, and lakes.
- Lotic: Fast-moving bodies of water like streams and rivers.
- Wetlands: Areas where the soil is generally saturated. Wetlands have soggy wet conditions virtually all year round.
Artificial ecosystems have biotic and abiotic factors but are not naturally occurring. They are designed and largely controlled by humans.
Some are still subjected to natural climatic conditions as in the case where crops are cultivated in an open land where they are still affected by the weather.
Then there are arrangements where the plants, animals, and other organisms are insulated from the natural elements, and nourishment is channeled to them by artificial means.
Types of Artificial Ecosystems
There are several types of manmade ecosystems. They are much simpler than natural ones and contain much lower biodiversity. The following are a number of them:
- Crop field
- Fish farm
- Modern cities
Crop fields are designed by man with consideration for soil type, climatic conditions, removal of weeds, artificial irrigation application of pesticides, and other non-natural measures taken to achieve the desired yield.
Rows of ridges or heaps are dug to contain and irrigate the crops, This may sometimes be carried out even outside the natural regular seasons since nourishment is provided independently of climate.
A greenhouse is another artificially cultivated environment that is even more isolated than the crop fields. This is because greenhouses are completely insulated from most elements of nature except sunlight.
They are usually made of transparent glass or synthetic material like plastic that keeps out wind, rain, atmospheric pressure, and other natural elements like insects and organic matter.
The sun can shine through however, it can also be controlled by using visors or dark covers.
These artificial aquatic ecosystems are typically built of glass or synthetics like fiber. They are used to keep marine life for aesthetic value, as pets, or as subjects of study.
Water, aquatic plants, and microbial elements are also sometimes put inside creating an ecosystem of its own. They can either be large or small.
Zoos are manmade structures used to house plants and animals away from their natural habitats. They sometimes have quite a variety and constitute a manmade ecosystem.
Fish farms are manmade containment arrangements for raising fish and other marine life that is meant for food.
Terrariums are similar containment structures to aquariums but do not necessarily contain water like aquariums. They are vessels used to keep certain animals and plants.
The main notable difference between natural and artificial ecosystems is that natural ecosystems are self-sufficient. They do not require any input from non-natural sources to function and thrive. Whereas manmade ecosystems by their very make-up need constant input from artificial sources to function.
Modern built-up communities like towns, mass housing, and cities are examples of artificial ecosystems. All the attributes of an ecosystem (a self-sufficient group of biotic and abiotic organisms interacting) are present. The major difference is the reduced level of biodiversity.
Disadvantages of Artificial Ecosystems
The disadvantages of artificial ecosystems are:
- Not self-sufficient and manpower is needed to sustain function.
- Potentially harmful unnatural additives like inorganic fertilizers and pesticides are used.
- There is low biodiversity.
- The natural ecosystem is partly destroyed to create space for cultivation. Some animals, plants, and microorganisms are displaced.
- It can aid in overpopulation
Advantages of Artificial Ecosystems
- Unwanted species can be excluded,
- Cultivation can be carried out even out of season
- Industrial quantities can be derived
- Less space can yield more.
- Crop and animal science can be studied more closely for optimum derivation.
Energy Flow in an Ecosystem
Two early pioneers of the study of the energy flow in an ecosystem were G. Evelyn Hutchinson who was a limnologist (a person who studied inland aquatic systems) and Charles Elton’s (an English zoologist and animal ecologist). G. Evelyn postulated that mineral nutrient availability in a body of water such as a lake limited algal generation, this would result in limiting the number of animals that feed on the algae. Raymond Lindeman expatiated on this idea further suggesting that the flow of energy through a lake was the primary driver of an ecosystem.
Today, we now know that energy flows and nutrient cycles are what link the biotic and abiotic factors of an ecosystem. Energy enters the ecosystem and is absorbed by the plants through photosynthesis. Animals also aid the movement of energy and matter by feeding on the plants and each other. Decomposers aid in nutrient cycling by converting nutrients stored in dead plants and animals back to a state that can readily be used up by other organisms. These decomposers also break down organic matter and release carbon back into the atmosphere. Therefore, the energy flow in an ecosystem involves three (3) phases or stages known as trophic levels. The trophic level shows how each organism contributes to the energy flow in an ecosystem.
Trophic Levels in an Ecosystem
In trophic systems, there are 3 levels of food production and consumption; these include primary producers, secondary producers (or primary consumers), and decomposers. Photosynthetic organisms are the primary producers while organisms or animals that feed on the primary producers are called primary consumers or secondary producers (herbivores). The animals that in turn feed on primary consumers are termed, secondary consumers. Each of these categories constitutes an individual trophic level. Those organisms that feed on microbes (bacteria and fungi) are called microbivores.
Primary Food Production in an Ecosystem (Photosynthesis)
Photosynthesis is the process through which energy and carbon enter an ecosystem. The process of photosynthesis is the first trophic level of the energy flow in an ecosystem. Plants make use of sunlight and carbon dioxide to make their own food. These plants and other photosynthetic organisms are referred to as Primary producers. The energy and carbon that are incorporated into plant tissue through photosynthesis are sometimes consumed by animals while the plant is still living or when the plant dies.
Primary consumers or Secondary Producers in an Ecosystem
The second trophic level of an ecosystem includes the primary consumers or secondary producers. Primary consumers are animals that feed directly on plants; these animals may include humans, herbivores, and decomposers. When humans eat plants directly, they can be referred to as primary consumers, the same term applies to herbivores that feed on plants. But when humans or carnivores eat herbivores such as goats, cattle, or sheep, the human and the carnivores are termed secondary consumers (because they eat the primary consumers).
Decomposition in an Ecosystem
The series of processes through which the carbon and nutrients in dead organic matter are broken down is known as decomposition. Without decomposition, the energy and nourishment cannot be absorbed by other organisms. This could potentially cause environmental contamination or pollution which may, in turn, cause the spread of diseases and litter the ecosystem. Decomposition releases nutrients that can be re-used for plant and microbial production. It also returns carbon dioxide to the atmosphere and water where it can be used in photosynthesis.
The organisms that help in the process of decomposition are termed Decomposers.
Food Chain and Food Web
The energy flow of an ecosystem showing the trophic levels can be represented graphical or pictorially using the Food chain and Food web.
The food chain is a graphical representation showing how food is produced to how it is consumed. It is a unidirectional graph or representation which starts with photosynthesis in plants and ends with digestion in consumers as well as decomposition in decomposers.
Food consumption in an ecosystem is not as simple as it is depicted in a food chain, because one animal can be eaten by many other animals and some animals such as humans can eat plants as well as other animals. Therefore, the process that completely shows the complex feeding habit in an ecosystem is known as the Foodweb.
Just as energy is exchanged within the biotic component of an ecosystem through the trophic levels, the abiotic components of an ecosystem also exchange nutrients. This exchange of nutrients of an ecosystem can be represented in the Nutrient Cycle.
The nutrient cycle shows how mineral nutrients are cycled between microbes, soil, plants, and animals. Some common nutrients being cycled include nitrogen, carbon, sulfur, and phosphorus.
Ecosystems are described as dynamic entities because they are constantly changing; animals reproduce and increase the population, rocks are being degraded and erosions take place thereby transforming the landscape – all these are changes or dynamics that occur in an ecosystem. Ecosystem dynamics, therefore, study the changes that occur in an ecosystem. They can be said to be the different shifts and movements biotic and abiotic components of an ecosystem undergo.
Factors that affect Ecosystem dynamics
Ecosystem dynamics are controlled by both internal and external factors that can be either resistant or resilient to ecosystem disturbances; ecosystems are subject to periodic disturbances that may take time to recover or worsen if counter-measures are not taken.
When negative factors affect the ecosystem, they need to be controlled in order not to cause destruction or disturbances to the normal functions. If small changes occur, the ecosystem can recover through negative feedback mechanisms, returning to its original state. But when overwhelming changes occur, then damages occur leading to disequilibrium.
These factors that influence the Ecosystem may include climate, soil, growth, competition, migration, succession, topography, etc.
The external factors determine the overall structure and physical behavior of the ecosystem. These external factors include climate, soil, and topography; these external factors can influence the ecosystem but cannot be affected by the ecosystem on which they act.
Internal factors on the other hand are affected and controlled by elements of the ecosystem; these factors include growth, competition, migration, succession, and types of species present.
Ecosystem ecology is the study of the processes and dynamics of ecosystems and how the flow of matter and energy through them affects other natural processes.
It can also be defined as the integrated study of an ecosystem’s biotic and abiotic components and their interactions within an ecosystem framework. This science examines how ecosystems function and how that relates to their basic constituents like soil, bedrock, chemicals, plants, and animals.
Ecosystem ecology scrutinizes physical and biological structures and how these ecosystem characteristics interact with one another. This helps eventually helps in understanding and knowing how to maintain good quality water and economically viable productivity.
Functional processes are one of the main areas of interest in ecosystem ecology. The ecological mechanisms maintain the structure and services produced by the ecosystem. They include primary productivity (production of biomass), trophic interactions, and decomposition.
Human understanding of sustainable production of fiber, fuel, forage, and production of water has been greatly improved by studies into the ecosystem function. The functional processes are mediated by regional-to-local level climate, disturbance, and management.
Therefore ecosystem ecology provides a formidable framework for identifying ecological mechanisms that interact with global environmental challenges. Two important examples are global warming and the degradation of surface water.
Ecology is the study of an ecosystem; it deals with the study of living organisms and their interaction and interdependency with their physical environment; it cannot be separated from the ecosystem.
Ecosystem ecology is inherently an interdisciplinary field of study because it encompasses every material, substance, and gas that is contained on the entire planet. Interactions are across the board because whatever affects one part of any ecosystem anywhere in the world will eventually affect others no matter how far away.
There have been significant debates about the specific dimensions of where an ecosystem begins and where it ends. Some believe the whole world is one ecosystem, while others think there are rather a set of several different ones that support the various species.
Importance of Biodiversity in an Ecosystem
Biodiversity describes the many different species of organisms or animals in an ecosystem and how these organisms depend on one another. The plants need nutrients in order to grow; these nutrients are provided by decomposers or microbes that act on dead organic materials. Animals in turn need plants in order to survive while releasing carbon dioxide into the atmosphere that is then used by plants to make food through photosynthesis.
Therefore, biodiversity is important for the equilibrium and continuous functioning of the ecosystem.
Frequently Asked Questions
What are the four types of ecosystems?
The four types of ecosystems are a set of classifications that include artificial, terrestrial, lentic, and lotic ecosystems.
What is a simple definition of an ecosystem?
A simple definition of an ecosystem is a group of living and non-living things that live and interact with each other in a given area.
What is the importance of an ecosystem?
The importance of an ecosystem is that it provides a habitat for plants and animals. They promote food chains and webs. Determination of ecological processes and promotion of life is another important input it contributes. The ecosystem plays a major role in recycling nutrients and resources making them available for biotic and abiotic functions.
How is the ecosystem useful to human beings?
A healthy ecosystem helps humans by purifying the air we breathe, sequestering carbon for climate regulation, and recycling nutrients needed for plant growth. It helps to decay organic matter to prevent the buildup of matter and as well releases energy for other animals and plants.
What is the biosphere?
The biosphere is part of the Earth that contains life forms. It can be described as the biotic component or factor of the Earth. All ecosystems contain biotic factors but the biosphere refers to the entire living organisms of the world.
What are the layers of the atmosphere?
The layers of the atmosphere or atmospheric layers are the stages or levels of airspace between the ground all the way up to the threshold or end of the Earth’s airspace. It is sorted into stages listed based on temperature prevalence. The layers are; the troposphere, the stratosphere, mesosphere, and thermosphere.
How do humans affect the ecosystem?
Humans affect the ecosystem in more negative ways than positive ways. Overpopulation puts a strain on resources and does not allow for sufficient time for the ecosystem to recover from damage caused. Pollution contaminates water systems and soil adversely affecting plants and wildlife. Burning fossil fuels and deforestation impede the ecosystem’s ability to regenerate important resources.
Some of this negative input causes ecological problems like climate change, soil erosion, air pollution loss of plant and animal habitat and increased mortality rate, and plant and animal extinction.
What are Ecosystem Services
Definition of Ecosystem Services
Ecosystem services can be defined as the advantages, benefits, and useful resources that human beings derive from a healthy ecosystem. Anything that is helpful to man but which he has not created himself is considered a natural service from the ecosystem. Ecosystem services, therefore, refer to the services rendered to humans by the ecosystem such as trees providing shed and oxygen, plants and trees providing food, wood, and medicine, etc.
The benefits we have been getting are derived from the natural environment right from the dawn of man; however, the consideration of these services as tangible services rendered was only postulated in relatively recent times.
Examples of Ecosystem Services
The Millenium Ecosystem Assessment (MA) was a major assessment of the impact the actions inactions of and human beings have had on the environment and the ecosystems at large. The assessment was called for by the late former Secretary-General of the United Nations Kofi Anan and carried out between 2000 and 2005.
The body through its work popularized the term ‘ecosystem services‘ and identified four major categories of ecosystem services namely:
- Provisioning services
- Regulating services
- Cultural services
- Supporting services
Provisioning services are also referred to as ecosystem goods and can be described as the products of nature that beings are able to collect directly. These resources are naturally produced and people can harvest and utilize them without any further complex processes.
- Raw materials
- Natural energy
- Genetic resources
- Ornamental resources
- Medicinal resources
- Biogenetic materials
All naturally occurring foods fall into this group they include; wild game (wild animals, birds), seafood (fish, crustaceans, molluscs, cephalopods, sea plants, microalgae, etc). Crops (cereals, vegetables, fruits, etc), edible plants, herbs, and spices, wild foods (mushrooms, honey, etc), and water.
This ecosystem service includes the natural resources that require a notable level of processing before the optimum utility (highest value) can be derived from them. They are; Rocks, wood, stone dust, laterite, tree sap, resins, crude oil, skins, etc.
Naturally occurring raw energy is another important ecosystem service. It is comprised of solar energy (sunlight), wind energy (wind currents), biomass energy, hydropower (water), natural gas.
Genetic resources are those biological materials that contain genes or metabolic material that may be derived from genes. In other words, genetic material is any substance that is derived from any plant, animal, microbial, or other natural sources containing individual functioning units of heredity. Some examples of genetic resources are microorganisms, animal breeds, plant varieties, genetic sequences, nucleotide, and amino acid sequencing information, traits molecular events.
Ornamental resources are naturally occurring materials that are valued and used for mostly decorative, representative, or symbolic purposes. The materials used for these types of functions are usually either beautiful to look at or performs the function of representing or being a symbol of an idea, a group, status, or designation. Examples of ornamental resources are; feathers of certain birds worn as a symbol of hierarchy or chieftaincy of particular tribes such as the native Americans, ornamental cowrie shells worn by some African tribes, stones, and diamonds considered precious that are used as decorations in dwellings and in body jewelry, ivory, ceramics, wood carvings, seashells, etc, used as ornaments and decorations.
Medicinal resources are substances and compounds that are used to diagnose, relieve, treat, modify or immunize human beings and animals against disease or ill health.
Originally all medicinal resources were derived from the natural ecosystem but relatively recent advances in research and development now include manmade compounds.
Naturally occurring medicinal resources in an ecosystem still account for most of the total volume of medicinal resources. They are derived from plants, animals, types of fungi, and bacteria with the overwhelming majority coming from plants.
Sources of Medicines
- Plant sources
- Animal sources
- Microbial sources
- Marine sources
- Mineral sources
- Synthetic/chemical derivative sources
- Semi-synthetic sources
- Biosynthetic (genetically engineered) sources
Numerous discovered and potentially undiscovered plants have medicinal and therapeutic qualities that have been used for centuries for a wide range of health issues. Plants their various parts, byproducts, and their derivatives make up the largest percentage of medicinal resources.
Early in the use of plants for medicines, mainly the leaves were used but later other parts like the bark, the fruit, the stem, and inner pulp have been found to also contain medicinal and therapeutic properties and eventually became widely used.
Plant parts and extracts that can be used without major or significant processing are called crude drugs.
The table below depicts some of the particular types of pharmaceuticals and medicinal utilities that can be obtained from what plant parts.
|Plant part||Derived drug|
|Leaves||Digoxin, digitoxin (from Digitalis purpurea/foxglove plant); atropine (from Atropa belladonna ).|
|Flowers||Vincristine, vinblastine (from Vinca rosea)|
|Fruits||Physostigmine (from Physostigma venenosum/calabar bean ).|
|Seeds||Strychnine (from Nux vomica) physostigmine (from Physostigma venenosum/calabar bean).|
|Roots||Emetine (from Cephaelis ipecacuanha); reserpine (from Rauwolfa serpentina)|
|Bark||Quinine (from Cinchona); atropine (from atropa belladonna)|
|Stem||Tubocurarine (from chondrodendron tomentosum)|
Animals are another source of medicinal substances that are natural in origin. Most of the time these substances are derived from bodily secretions, glands, or fluids of certain animals. They include material that may or may not require further processing to obtain the desired medicinal value from them.
The medicinal substances derived from animals that are not refined further are termed crude products while those that are processed further are termed refined animal products.
Examples of medicinally applicable animal products and by-products are; cod liver oil, beeswax, musk, antitoxins sera, enzymes, insulin, adrenaline, heparin, and thyroxine.
Microorganisms have been the source of many important medicinal substances that have been discovered and utilized till today. Some of these medicinal substances were discovered accidentally but have made a big difference in general human health.
Microorganisms can broadly be categorized into six types namely:
Examples of important medicinal substances derived from microbial sources under medicinal resources of provisioning ecosystem services; penicillin (produced by Penicillium chrysogenum), streptomycin from streptomyces griceus, chloramphenicol (from Streptomyces venezuelae), neomycin (from Streptomyces fradiae), bacitracin (Bacillus subtilis), xanthan (polysaccharide gum secreted by Xanthomonas campestris), etc.
Marine flora and fauna contain compounds that have been found to have many beneficial medicinal and health properties. Some of them have bio-active materials that have been shown to prevent, cure, combat, and relieve a variety of health challenges.
Some examples of these marine sources of provisionary ecosystem services are; coral sponges, fish, and some marine microorganisms. They produce biologically potent chemicals that have been shown to carry out anti-inflammatory, anti-cancer/tumor growth, and antiviral activity.
For instance, curacin A from cyanobacterium Lyngbya majuscule; eleutherobin from coral (Eleutherobia sp.), discodermolide from the marine sponge Discoderdermia dissoluta, show potent tumor-fighting activity.
The human body requires trace elements of certain minerals to maintain homeostasis (the physiological process of a living organism in maintaining the stability of diverse internal variables such as temperature, acidity, and water levels despite environmental changes and disturbances ).
People that are deficient in these minerals can be administered certain specific drugs that contain the necessary minerals to restore this function. Metallic and non-metallic mineral extracts from marine ecosystem sources have been used as drugs for this purpose for ages
The table below highlights some of the minerals that can be used for certain conditions.
|Ferrous sulfate||iron-deficiency anemia|
|Magnesium sulfate||diarrheal disorder|
|Magnesium trisilicate, aluminum hydroxide, sodium bicarbonate||as antacids for hyperacidity and peptic ulcer|
|Zinc oxide ointment||skin protection, wounds, eczema|
|Gold salts (solganal auranofin)||anti-inflammatory; rheumatoid arthritis|
|Radioactive isotopes of gold, iodine, and phosphorus||diagnosis/treatment of malignant conditions|
Synthetic/chemical derivative sources
Synthetic drugs are produced using chemical synthesis which involves rearranging chemical derivatives to constitute new compounds.
Research and development have evolved the level of expertise to such a standard that it has lead to an increase in the number of sources for successfully synthesizing more useful drugs.
Scientific advances in research and development also lead to a better understanding of the phytochemical method of investigation. Now there is a huge volume of synthetically developed drugs.
A few examples of synthetic/chemically derived drugs are as follows:
- synthetic cathinones
- novel benzodiazepines
- synthetic cannabiniods
Semi-synthetics are partly synthetic and partly natural which makes them hybrid drugs. They are basically substances that are obtained from natural sources but are chemically modified to improve efficacy, potency, or reduce side effects.
The semi-synthetics are sometimes resorted to when there is a risk of the natural one being unsuitable for usage.
Examples of semi-synthetic drugs are:
- the antibiotic penicillin
- the anti-cancer drug paclitaxel
Biosynthetic (genetically engineered) sources
Biosynthetic or genetically engineered sources are a relatively new development in the industry that has been combined with discoveries and advances in the fields of molecular biology, recombinant DNA technology, DNA alteration, gene splicing, immunology, and immune pharmacology.
Medication that is developed using living organisms aided by biotechnology or genetic engineering is termed biologics, biopharmaceuticals, recombinant DNA expressed products, bioengineered, or genetically engineered drugs.
Some examples are; recombinant Hepatitis B vaccine, recombinant insulin.
Other examples of biosynthetic/genetically engineered drugs and their applications are illustrated in the table below:
|Hepatitis C||Interferon α|
|Multiple sclerosis||Interferon β|
|Hemophilia||Factor VIII and Factor IX|
Regulating services can be described as the processes that the ecosystem/nature carries out to purify, recycle, reconstitute, or improve natural resources that humans, animals microorganisms, and plants need for their well-being.
They include such resources and processes as; pollination, decomposition, water purification, air purification, erosion/flood control, control of populations, biological control of pests/diseases, carbon storage, and climate regulation.
Cultural services refer to the heavy influence the ecosystem and nature as a whole have on human cultures. From ancient times human activities, religious beliefs, migration, style/type of clothing worn, location of habitation, type of habitation, creativity artistic appreciation, and many other cultural and core values are determined directly or indirectly by the cultural services of the ecosystem.
Supporting services are simply the functions that the ecosystem carries out that help its own system continue operating normally and to be able to provide the other services.
Some of the supporting services are; photosynthesis, nutrient cycling, soil formation, primary production, and the water cycle.