Ecosystem: Definition, Types, Structure & Examples

The natural world is made up of vastly different types of physical environments and organisms uniquely adapted to living there. Another word for this concept in biology is an ecosystem.

This article will provide you clear explanations of ecosystems and offer interesting examples.

Ecosystem Definition in Biology

Biologists define an ecosystem as a community of living organisms and their physical environment, which includes both biotic and abiotic factors.

Biotic factors are living things in an interdependent ecological system like plants, animals, microbes and fungi.

Abiotic factors are non-living things like water, sunlight, shelter, rocks, minerals, soil and climate.

Origins of Ecology

The scientific study and classification of plants and animals dates back to Aristotle in ancient Greece. In the early 1800s, Darwin described competition between species and evolution through natural selection. Ernst Haeckel coined the word ecology around this same time.

In the late 1800s, Eugenius Warming suggested that abiotic factors, such as drought, fire and cold weather also influenced species behavior and adaptation strategies. Warming traveled extensively in his work and developed a University course on plant ecology. His ideas caught on when British and North American scientists read his classic book, Oecology of Plants.

The term ecosystem was coined by Arthur Tansley in 1936.

Types of Ecological Systems

There are three broad categories of biological ecosystems. Each has a distinct species composition and structure. The largest ecosystem is the marine ecosystem. All ecosystems are affected by global climate and human activity, such as pollution, irrigation, urbanization, mining and deforestation.

Marine ecosystem covers about 70 percent of the Earth’s surface. Along with the oceans, marine ecosystems include sandy shores, estuaries, mud flats, Antarctica waters, salt marshes and vibrant coral reefs, all teeming with life. The climate of marine ecosystems around the world ranges from tropical heat to polar vortexes.

Aquatic ecosystems include lakes, rivers, ponds and wetlands. Freshwater species are going extinct at a much faster rate than marine or terrestrial species, according to National Geographic. Climate change and pollution are major threats to aquatic ecosystems.

Terrestrial ecosystems are land-based ecological communities in places like the Arctic tundra, desert, forests and grasslands. Animals in polar climates have co-evolved similar adaptive traits such as thick fur and an insulating fat layer.

Key Ecosystem Biomes

Biomes are a slightly broader term than ecosystems, although they're quite similar. Biomes are distinctive ecological communities that themselves can contain many ecosystems within it. They're useful for categorizing the characteristics of certain areas that can directly affect the type or types of ecosystems that arise there.

Distinguishing characteristics of these biomes/ecological systems include their particular climate, zone, elevation, soil type, amount of precipitation and species composition.

Aquatic biomes include coral reefs, estuaries, marine, wetlands and freshwater.

Desert biomes include Mojave desert, Chile’s coastal deserts, Death Valley and Greenland’s frigid deserts.

Forest biomes include tropic rainforest, temperate forest, chaparral (shrubs) and taiga (boreal forest).

Grassland biomes include savannas, steppes, prairies and South American pampas.

Structure of Ecosystems

Living organisms must have energy and nutrients to grow, react and reproduce. Organisms are interdependent and connected to each other in the circle of life. Energy is transferred from one level of the food pyramid to the next. For example, fish eat algae and squid eat fish.

Algae, fish, squid and predatory sharks are an example of a food chain. The food web is made of many overlapping food chains. The energy pyramid starts with producers at the base of the pyramid followed by consumers and predators at upper levels. Energy is lost with each transfer between organisms, so the pyramid is upright and not inverted.

Plants and phytoplankton are producers that contain photosynthetic pigments that use sun energy and carbon dioxide to make sugar. Primary consumers eat plants and secondary consumers eat primary consumers. An apex predator with no natural enemies holds the top spot on the food pyramid.

Functions of the Nutrient Cycle

Biomass is conserved and recycled in an ecosystem. When organisms die, decomposers break down the organic matter into energy and nutrients that flow back into the ecosystem. Decomposing animals release carbohydrates, fats, proteins and gasses when acted upon by microbes, flies and worms.

Bacteria and microbes break down decaying plant matter into nutrients like calcium, nitrogen, potassium and phosphorus that enrich the soil.

Energy and nutrients also flow between ecosystems. For example, rocks in a river erode and put minerals into the water that flow downstream into lakes and fields. The effect can also be deleterious. Nitrogen and phosphorous runoff from farmlands can pollute the waterways.

Unlike matter that gets recycled, energy flows in one direction. Plants produce energy-rich molecules of glucose from captured sunlight, water and carbon dioxide. Chemical energy is transferred to consumers for cell metabolism, and extra energy is given off as heat.

Stability in Ecosystem Functioning

Ecosystems are dynamic with a constant ebb and flow of energy and matter. Nutrient levels, populations of species, weather patterns, temperature, seasons of the year fluctuate and change. Diversity in an ecosystem contributes to stability.

Despite the flux and dynamic nature of ecosystem ecology, an overall state of equilibrium remains steady. Ecosystems maintain a steady state with a fairly consistent composition. Normally, fluctuating biotic and abiotic features do not threaten a stable system. In other words, a rainforest is still a rainforest even if the population of monkeys decreases.

Disruptions in Ecosystem Functioning

Natural disturbances can disrupt ecosystem functioning. For instance, hurricanes, wild fires, flooding and volcanoes upset ecosystem services. Flooding can contaminate water sources. Habitat is lost and species may be displaced. Predator-prey balance may be off causing a domino effect on other species.

Invasive species can potentially threaten the well-being and very existence of other species. Invasive species include plants and animals introduced to an area intentionally or accidentally. Sometimes invasive species are deliberately brought in to stop a predator that is taking over. For example, conservationists released salmon into the Great Lakes to control a less desirable invasive species.

Human activity is another major cause of perilous ecosystem change. Hunting, overfishing, exploitation of non-renewable resources, toxic waste and pollution threaten the ecosystems and their biomes. In extreme cases, such as a leak from nuclear power plant, the affected ecosystems could be radioactive and carcinogenic for years to come.

Marine Ecosystem Example

The Great Barrier Reef off the coast of Australia is an incredibly large and diverse marine ecosystem that has existed for millions of years. Algae provide food for growing corals that attach to dead corals in the reef.

Young corals floating in the water are eaten by fish and animals swimming in the ocean. Skeletonized corals can still be consumed by worms, snails and voracious starfish.

Some corals have a mutually beneficial relationships with shrimp and crabs that live in coral colonies and fight off mutual enemies using their pinchers. Abiotic factors that significantly affect corals are rising water temperatures, ocean acidification and carbon dioxide levels.

According to the Smithsonian Museum of Natural History, acidic seawater is already starting to dissolve the skeleton structure of coral reefs in places like Hawaii.

Aquatic Ecosystem Example

The Lake of the Woods aquatic ecosystem is located on the border of Canada and the United States. This freshwater body is what remains of the once massive glacial Lake Agassiz.

In this freshwater aquatic ecosystem, phytoplankton, zooplankton, algae and bacteria provide optimal levels of food, habitat and oxygen for tasty fish. Lake of the Woods is often called the Walleye Capital of the World_._

Invertebrates like mayflies and midges also play an important role in freshwater lakes. They eat microorganisms that feed on decaying plant and animal matter. Invertebrates provide an excellent source of food for little fish that may be eaten by big fish, which may be caught by pelicans, herons, bear and humans.

Abiotic factors affecting the state of an aquatic ecosystem like Lake of the Woods include air and water temperature, carbon dioxide levels and toxic runoff.

Terrestrial Ecosystem Example

The Amazon rainforest ecosystem is a species-rich terrestrial environment in South America. Sunlight is absorbed by lush broad-leaf plants and tall trees that provide food and shelter for an astounding number of birds, mammals, insect, lizards and snakes in the tropics. Many of those creatures are eaten by predators like the jaguar.

When organisms die in the rainforest, their energy and nutrients are broken down quickly by decomposers like maggots and microbes. Nutrients go back into the soil and help plants grow. Abiotic factors of the rainforest include large amounts of rainfall, heat and a tropical climate that nourishes species biodiversity from the forest floor to the thick hanging canopies.

Ecosystem vs. Community Ecology

Depending on their research interests, ecologists may focus on the field of community ecology, ecosystem ecology or both. Community ecology specifically examines interactions between differing species and the outcome of that interaction. Ecosystem ecology takes a much broader look at living and non-living factors that affect an ecological community and trigger ecosystem change.

For example, an ecologist who wants to find out why giant carp are taking over a lake that was once full of trout might undertake a community ecology study of the fish population along with an ecosystem study of diminishing water quality that affects all species of aquatic life. Ecologists conduct studies that help save natural resources for future generations.

Protection of Ecosystem Structures

Ecosystem management employs conservation practices to maintain the integrity of ecosystem functioning and structures. Ecosystem structures are said to have integrity when they are balanced, stable and characteristic of ecological communities in that natural region.

Both abiotic and biotic factors are generally predictable. Population dynamics should also be self-sustaining without need of human intervention to restore balance.

Good ecosystem management plays an important role in preserving state parks, national parks and other wildlife areas. Understanding the history of the ecosystem and normal rates of change or succession helps aid in early detection of structural problems. The goal is to maintain biodiversity and ensure the viability of native species. From New York to California, environmentalists are closely monitoring climate patterns.

Catastrophic Ecosystem Destruction

Natural disasters such as a hurricane are followed by orderly succession and natural rebuilding of the area to its prior state. However, human activity can temporarily or permanently destroy an ecosystem ecology. Ecosystem disasters have happened in the United States and around the world.

The Gulf of Mexico ecosystem has been severely disrupted by pollutants carried to the Gulf from the Mississippi River. Nitrogen and phosphorous from fields, feedlots and sewage drain into the river from many states.

Excessive levels of nutrients stimulate toxic algal blooms, alter the food change and deplete oxygen in the water resulting in a dead zone and massive fish kills. The area is also impacted by abiotic factors such as hurricanes and flooding.

In 1986, an accident at the Chernobyl nuclear power plant in the Ukraine discharged deadly radioactive material into the atmosphere. Millions of people were exposed to radiation. Thousands of children who drank milk from cows grazing in the contaminated area developed thyroid cancer. Today, the radioactive area surrounding Chernobyl is off limits to people, but wolves, wild horses and other animals are present in significant numbers.