What is Ecosystem?
An ecosystem is a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life.
Ecosystems contain biotic or living, parts, as well as abiotic factors, or non-living parts. Biotic factors include plants, animals, and other organisms. Abiotic factors include rocks, temperature, and humidity.
Every factor in an ecosystem depends on every other factor, either directly or indirectly. A change in the temperature of an ecosystem will often affect what plants will grow there, for instance.
Animals that depend on plants for food and shelter will have to adapt to the changes, move to another ecosystem, or perish.
Ecosystems can be very large or very small. Tide pools, the ponds left by the ocean as the tide goes out, are complete, tiny ecosystems. Tide pools contain seaweed, a kind of algae, which uses photosynthesis to create food. Herbivores such as abalone eat the seaweed.
such as sea stars eat other animals in the tide pool, such as clams or mussels. Tide pools depend on the changing level of ocean water. Some organisms, such as seaweed, thrive in an aquatic environment, when the tide is in and the pool is full.
Other organisms, such as hermit crabs, cannot live underwater and depend on the shallow pools left by low tides. In this way, the biotic parts of the ecosystem depend on abiotic factors.
The whole surface of Earth is a series of connected ecosystems. Ecosystems are often connected in a larger biome. Biomes are large sections of land, sea, or atmosphere. Forests, ponds, reefs, and tundra are all types of biomes, for example.
They’re organized very generally, based on the types of plants and animals that live in them. Within each forest, each pond, each reef, or each section of tundra, you’ll find many different ecosystems.
The biome of the Sahara Desert, for instance, includes a wide variety of ecosystems. The arid climate and hot weather characterize the biome. Within the Sahara are oasis ecosystems, which have date palm trees, freshwater, and animals such as crocodiles.
The Sahara also has dune ecosystems, with the changing landscape determined by the wind. Organisms in these ecosystems, such as snakes or scorpions, must be able to survive in sand dunes for long periods of time.
The Sahara even includes a marine environment, where the Atlantic Ocean creates cool fogs on the Northwest African coast. Shrubs and animals that feed on small trees, such as goats, live in this Sahara ecosystem.
Even similar-sounding biomes could have completely different ecosystems. The biome of the Sahara Desert, for instance, is very different from the biome of the Gobi Desert in Mongolia and China. The Gobi is a cold desert, with frequent snowfall and freezing temperatures.
Unlike the Sahara, the Gobi has ecosystems based not in sand, but kilometers of bare rock. Some grasses are able to grow in the cold, dry climate.
As a result, these Gobi ecosystems have grazing animals such as gazelles and even takhi, an endangered species of wild horse.
Even the cold desert ecosystems of the Gobi are distinct from the freezing desert ecosystems of Antarctica. Antarcticas thick ice sheet covers a continent made almost entirely of dry, bare rock. Only a few mosses grow in this desert ecosystem, supporting only a few birds, such as skuas.
The structure of an ecosystem consists of two major components:
- biotic components
- abiotic components
1. Biotic components
The biotic components include all the living things. Basically, there are two major types of living things. They are the eukaryotes and the prokaryotes. Eukaryotes are characterized by having membrane-bound organelles (such as a nucleus) inside their cells.
The prokaryotes, in turn, are those lacking membrane- bound organelles. For further differences between these two groups, read this).
Examples of eukaryotes are plants, animals, fungi, and protists. Bacteria and archaea represent the prokaryotes. Now, each of them has a “job” to do in the ecosystem.
Plants, for instance, have chloroplasts that enable them to harvest light energy. Then, they take carbon dioxide and water from their environment to convert them into sugar, a biomolecule that can be used to synthesize chemical energy (such as ATP).
Because they are capable of producing their own food through photosynthesis, they are referred to as the producers. Next to the producers are the primary consumers.
They feed on the producers while they serve as a food source to the higher levels of consumers (e.g. secondary and tertiary).
The animals are examples of consumers. The animals that feed on plants are called herbivores whereas those that feed on other animals are carnivores. Then, there are those that feed on both plants and animals. They are called omnivores.
2. Abiotic components
The abiotic components include all the non-living things, such as rocks, soil, minerals, water sources, and the local atmosphere. Similar to biotic components, the abiotic components also have their ecological role.
For example, elements and compounds serve as sources of nutrients. They are essential to the growth and metabolism of an organism. Apart from providing nutrients, they also provide organisms a place to live and thrive
The biotic and the abiotic components interact with one another as a system and are linked to one another via nutrient cycles and energy flows. For instance, energy and nutrients enter the system via the photoautotrophs.
They are organisms that carry out photosynthesis, such as plants and green algae. Then, the heterotrophs, for example, animals, feed on the photoautotrophs. This makes the energy and the nutrients move through the system.
The death of these organisms incites decomposition by the decomposers. This process releases the nutrients back to the environment to be re-used by the organisms. To learn more about this, proceed to: Processes of the Ecosystem.
The biotic and abiotic components can also serve as environmental (ecological) factors that affect the ecosystem. The biotic components whose biological activity creates an impact in the ecosystem are referred to as the biotic factors.
The abiotic factors, in turn, include the non-living things and the physical aspects of an ecosystem, such as climate, temperature, and pH.
An example of a biotic factor is the extent of predation in an ecosystem. If there is an increase in the number of predators, predation activity would likely increase. This, in turn, could significantly lessen the population density of their prey.
If their prey is a key species, meaning another group of organisms depends on them for survival, then the decline (or worse, the extinction) of these key species could also lead to the decline (or worse, the extinction) of the organisms relying upon them.
As for the abiotic factor, they can regulate the size or the density of a species population. For instance, acid rain, which is unusually acidic precipitation and has high levels of hydrogen ions, can produce detrimental effects to the soil (e.g. leaching) as well as to the plants and aquatic animals that are sensitive to low pH. Apart from pH, other abiotic factors are light, salinity, air, soil or substrate, and temperature.
Types of Ecosystems
What are the 4 types of ecosystems? The four types of ecosystems are terrestrial, freshwater, marine, and artificial. The first three occur naturally in various biomes. The last one is man-made. Ecosystems vary in size from the micro-ecosystems (e.g. tree ecosystems) to the largest ecosystems such as ocean ecosystems.
1. Terrestrial ecosystem
The terrestrial ecosystem is one that occurs on land. Examples of land-based ecosystems are forest ecosystems, grassland ecosystems, tundra ecosystems, and desert ecosystems.
A forest ecosystem is one that consists of various plants, particularly trees. Because of the abundance of plants that serve as producers, this ecosystem abounds in life.
Not only plants but also animals are teeming in a forest. They are also a great source of fruits, wood, They also help maintain the earth’s temperature. They are also a major carbon sink. (Ref.6)
Grassland ecosystems are typically found in tropical or temperate regions. They are dominated by grasses. As such, the animals commonly found in this type of ecosystem are grazing animals, such as cattle, goats, and deer.
Tundra ecosystems are characterized as being treeless and snow-covered. The snow melts briefly in spring and summer, producing shallow ponds. During this time, lichens and flowering plants typically grow.
Because of the ice that covers the land in the tundra, this type of ecosystem is important in regulating the earth’s temperature. It also serves as a water reservoir (in the form of ice or frost).
Desert ecosystems are the ones occurring in desert habitats. Deserts are typically arid and windy. Some of them contain sand dunes, others, mostly rock. Organisms in the desert are not as diverse as those in forests but they possess adaptations that make them suited to their environment.
Plants that are commonly found in the desert are CAM plants, such as cacti. Desert animals include insects, reptiles, and birds.
2. Freshwater ecosystems
Freshwater ecosystems are the aquatic ecosystems that do not contain saltwater. They are home to algae, plankton, insects, amphibians, and fish. There are two major types: lentic and lotic ecosystems.
A lentic ecosystem refers to ecosystems in still waters. Examples include the following: ponds, puddles, and lakes. Lakes, in particular, may form zonation. That is when it becomes very well established that different zones are formed.
These zones are as follows: littoral, limnetic, and profundal. The littoral zone is the part that is near the shore. Here, light can penetrate up to the bottom. The limnetic zone is the zone in which light does not completely penetrate through.
The part of the limnetic zone that is penetrated by light is the photic zone whereas the zone in which light cannot penetrate through, and therefore is dark, is the benthic zone. The plants and animals vary in these zones.
For instance, rooted plants are found in the littoral zone but not in the limnetic zone. Rather, freely-floating plants are the ones commonly seen on the surface of the limnetic zone.
A lotic ecosystem is an aquatic ecosystem characterized by a freshwater habitat that is freely flowing. That is as opposed to the lentic that is nearly stationary.
Examples include rivers and streams. Many plants and animals in these ecosystems have adaptations to help them cope with the force and the different conditions that running water brings.
3. Marine ecosystem
A marine ecosystem is an aquatic ecosystem that contains saltwater. Examples are the ecosystems in the seas and oceans. The ocean ecosystems, in particular, are an important source of atmospheric oxygen due to the vast population of autotrophic algae that release oxygen through photosynthesis. Marine ecosystems are regarded as the most abundant type of ecosystem in the world. ( Ref.7 )
4. Artificial ecosystem
An artificial ecosystem is a man-made system, which can be further classified as terrestrial, freshwater, or marine. An example of an artificial ecosystem is a terrarium. Many man-made ecosystems are built for conservation purposes, aesthetics, and studying biology and ecology.
Processes of the Ecosystem
In an ecosystem, energy flows while materials are cycled. These two processes are linked and essential to the structure, function, and biodiversity of an ecosystem. Let’s take a look at the figure below to understand them further.
1. Energy flow
The fundamental source of energy in almost all ecosystems is radiant energy from the Sun. The energy of sunlight is used by the ecosystem’s autotrophic, or self-sustaining, organisms (that is, those that can make their own food).
Consisting largely of green vegetation, these organisms are capable of photosynthesis i.e., they can use the energy of sunlight to convert carbon dioxide and water into simple, energy-rich carbohydrates.
The autotrophs use the energy stored within the simple carbohydrates to produce the more complex organic compounds, such as proteins, lipids, and starches, that maintain the organisms’ life processes. The autotrophic segment of the ecosystem is commonly referred to as the producer level.
Organic matter generated by autotrophs directly or indirectly sustains heterotrophic organisms. Heterotrophs are the consumers of the ecosystem; they cannot make their own food.
They use, rearrange, and ultimately decompose the complex organic materials built up by the autotrophs. All animals and fungi are heterotrophs, as are most bacteria and many other microorganisms.
2. Trophic levels
Together, the autotrophs and heterotrophs form various trophic levels in the ecosystem: the producer level, the primary consume, the secondary consumer level, and so on.
The movement of organic matter and energy from the producer level through various consumer levels makes up a food chain. For example, a typical food chain in a grassland might be
grass (producer) → mouse (primary consumer) → snake (secondary consumer) → hawk (tertiary consumer)
Actually, in many cases the food chains of the ecosystem’s biological community overlap and interconnect, forming what ecologists call a food web.
The final link in all food chains is made up of decomposers, those heterotrophs that break down dead organisms and organic wastes into smaller and smaller components, which can later be used by producers as nutrients.
A food chain in which the primary consumer feeds on living plants is called a grazing pathway, and a food chain in which the primary consumer feeds on dead plant matter is known as a detritus pathway. Both pathways are important in accounting for the energy budget of the ecosystem.
3. Nutrient cycling
Nutrients are chemical elements and compounds that organisms must obtain from their surroundings for growth and the sustenance of life.
Although autotrophs obtain nutrients primarily from the soil while heterotrophs obtain nutrients primarily from other organisms, the cells of each are made up primarily of six major elements that occur in similar proportions in all life-forms.
These elements—hydrogen, oxygen, carbon, nitrogen, phosphorus, and sulfur—form the core protoplasm of organisms. The first four of these elements make up about 99 percent of the mass of most cells.
Additional elements, however, are also essential to the growth of organisms. Calcium and other elements help to form cellular support structures such as shells, internal or external skeletons, and cell walls.
Chlorophyll molecules, which allow photosynthetic plants to convert solar energy into chemical energy, are chains of carbon, hydrogen, and oxygen compounds built around a magnesium ion.
Altogether, 16 elements are found in all organisms; another eight elements are found in some organisms but not in others.
These bioelements combine with one another to form a wide variety of chemical compounds. They occur in organisms in higher proportions than they do in the environment because organisms capture them, concentrating and combining them in various ways in their cells, and release them during metabolism and death.
As a result, these essential nutrients alternate between inorganic and organic states as they rotate through their respective biogeochemical cycles: the carbon cycle, the oxygen cycle, the nitrogen cycle, the sulfur cycle, the phosphorous cycle, and the water cycle.
These cycles can include all or part of the following environmental spheres:
- the atmosphere, which is made up largely of gases including water vapour;
- the lithosphere, which encompasses the soil and the entire solid crust of Earth;
- the hydrosphere, which includes lakes, rivers, oceans, groundwater, frozen water, and water vapour; and the biosphere, which includes all living things and overlaps with each of the other environmental spheres.
A portion of the elements are bound up in limestone and in the minerals of other rocks and are unavailable to organisms. The slow processes of weathering and erosion eventually release these elements to enter the cycle.
For most of the major nutrients, however, organisms not only intercept the elements moving through the biosphere, but they actually drive the biogeochemical cycles.
The movement of nutrients through the biosphere is different from the transfer of energy because, whereas energy flows through the biosphere and cannot be reused, elements are recycled.
For example, the same atoms of carbon or nitrogen may, over the course of eons, move repeatedly between organisms, the atmosphere, the soil, and the oceans.
Carbon released as carbon dioxide by an animal may remain in the atmosphere for 5 or 10 years before being taken up by another organism, or it may cycle almost immediately back into a neighbouring plant and be used during photosynthesis.
4. Community dynamics
Ecosystems are dynamic. Their composition and structure may change over time especially when a disturbance occurs. For example, a volcanic eruption is a natural disturbance that can create a new land that is open for colonization.
Oftentimes, the first species to colonize a barren land are lichens. Eventually, their biological activities will alter the condition of the environment. This will make it less harsh and more habitable for new species.
The progressive replacement of one dominant type of species or community by another is called succession.
This succession will go on until a climax state is established, meaning the ecosystem has achieved stability and no further successions will occur unless another disturbance disrupts the ecological balance.
For example, a massive flood wiped a previously stable community. The land will be open again for colonization.
A succession in which the new land is colonized for the first time is referred to as primary succession whereas a succession in an area that was previously occupied by a community but was disturbed and replaced by recolonization is called secondary succession.
Take a look at the schematic diagram of succession below. You will notice that the process started as a barren land with bare rocks. The pioneer species, like lichens and moss, will grow on the rocks and will become the pioneer species.
Then, the site is next colonized by grasses and herbaceous plants. Soon, trees will grow on this site when their seeds reach the site, for example by wind currents or by bird droppings containing undigested seeds.
5. Function and biodiversity
Ecosystems are responsible for the cycling of nutrients and for allowing the flow of energy, such as from the sun to the biotic components. The various biological, physical, and chemical systems work together in maintaining the stability of these systems on earth.
Biodiversity is essential for an ecosystem to function. Biodiversity refers to the biotic components. The more diverse the biotic components are, the “healthier” the ecosystem will be. That is because each species has an important role to play.
The more diverse the species are, the greater is the chance that the ecosystem will persist and continue to function. High diversity in an ecosystem can help improve productivity and thereby stabilize the functioning of an ecosystem.
Examples of Ecosystem
Examples of ecosystems described here are the following:
- Deciduous forest ecosystem
- Savannah ecosystem
- Coral reef ecosystem
- Hot spring ecosystem
1. Deciduous Forest ecosystem
A deciduous forest is dominated by trees that shed leaves seasonally and then regrow their leaves at the start of the new growing season. They shed leaves as an adaptive mechanism against the cold season in temperate regions or to the dry seasons of the subtropical and tropical regions.
The dominant trees in mid-latitude are oaks, beeches, birches, chestnuts, aspens, elms, maples, and basswoods. In the Southern Hemisphere, the dominant tree is the genus Nothofagus (southern beeches).
The animals commonly found are snakes, frogs, salamanders, turtles, nails, slugs, insects, spiders, birds (such as warblers, owls, woodpeckers, hawks, etc.), and mammals (such as mice, moles, chipmunks, rabbits, weasels, foxes, and deer).
2. Savannah ecosystem
Savannahs are a mix of woodland and grassland ecosystems. The widely spaced, scattered canopy trees allow light to penetrate and reach the ground.
Because of that, shrub and herbaceous layers dominated by grasses are able to grow abundantly as well. Thus, the animals commonly found here are the grazers, such as sheep, cattle, and goats. This type of ecosystem often serves as a transition zone between forest and desert or grassland.
3. Coral reef ecosystem
The coral reef is an ecosystem created by reef-building corals. The reefs are actually colonies of coral polyps, such as stony corals that live together in clusters. They are one of the most diverse ecosystems on earth.
As such, they are referred to as the rainforests of the sea. Most of them are found at shallow depths in tropical waters. Some of the species that inhabit the reefs are mollusks, worms, crustaceans, echinoderms, sponges, tunicates, and fish.
4. Hot spring ecosystem
A hot spring is a spring with water temperatures that are higher relative to its surroundings. The water that is coming out of the spring is heated geothermally, i.e. via the heat from the earth’s mantle.
Because of the high temperature, it is one of the ecosystems that contain very few types of organisms. Thermophiles are organisms that can thrive at temperatures ranging from 45 to 80°C (113 and 176 °F).
Some of these organisms are thermophilic amoeba (such as Naegleria fowleri and Acanthamoeba), thermophilic bacteria (e.g. Legionella), and various archaea.
Ecosystems confined to small or tiny spaces and yet defined by specific environmental factors are called micro-ecosystems. Let’s take a look at a tree ecosystem. A tree creates a small ecosystem where various kinds of organisms live.
For example, a tree may harbor lichens and other epiphytes (arboreal plant), invertebrates (such as insects), amphibians, and other animals. The epiphytes, themselves, provide a habitat for other organisms, such as fungi, bacteria, and myxomycetes.