Ecological Succession: Definition, Types, Examples, Facts, Characteristics

What is Ecological Succession?

Ecological succession is the amount of subsequent, orderly processes where ecosystems make changes across time from disturbed environments into stable, mature ecosystems. It involves the gradual colonisation of species, establishment of communities, and interaction of the organisms with the environment. There are two forms of this process: primary succession, which starts in an entirely new habitat lacking soil and vegetation, and secondary succession, which takes place in areas where an existing community has been disturbed or destroyed but the soil remains.

Ecological succession is important in appreciating the evolution of an ecosystem to changes in the environment. Succession plays a significant role in the dynamics of ecosystems as it promotes biodiversity, enhances resilience, and promotes nutrient turnover. Through succession, it is possible to make several inferences about the behaviour an ecosystem can face in the case of perturbation through events such as natural disasters or man-induced activities, hence conserving endeavours and management strategies of ecosystems aimed at conserving biodiversity and functions.

Types of Ecological Succession

The ecological succession and its types are listed below:

Primary Succession

Primary succession takes place in areas where the soil is completely absent at the beginning, for instance, on bare rock or land exposed by retreating glaciers or volcanic eruptions. Primary succession is initiated by pioneer species, which constitute the first category of living things that colonise these areas, which tend to be inhospitable.

These types of species, mainly lichens and mosses, are tolerant of harsh conditions and, start the rock breakdown into the soil. These pilot species eventually die and decompose, adding organic matter to the developing soil, thus allowing more diverse plant communities to become established. For example, lava flows following a volcanic eruption or after the retreat of glaciers when bare rock is exposed.

Secondary Succession

Secondary succession is the type of succession that occurs in an already existing but disturbed ecosystem where the soil and seeds for plants are intact. It happens more rapidly than primary succession as, here, the soil itself contains many nutrients and seed sources.

This kind of transition may happen after forest fires, abandoned agricultural land, or areas that have been swept away by hurricane-force winds. Compared with primary succession, starting with bare surroundings can result in the fairly swift re-establishment of plant and animal communities. Indeed, the series of species that constitutes secondary succession is generally quite predictable and usually comprises a series of stages from fast-growing species to the final stages, which lead to more stable diverse communities.

Cyclic Succession

Cyclic succession, also known as seasonal succession, is a repeated, predictable pattern of succession taking place over shorter timescales within specific ecosystems. This is driven by seasonal changes in abiotic environmental conditions, such as temperature, precipitation, and sunlight. Thus, the plant communities in temperate regions may undergo cyclic succession, where different species dominate throughout spring, summer, autumn, and winter. This type of succession does not involve drastic changes in the structure of the ecosystem but rather involves changes in dominant species under seasonal variation.

Seral Community Succession

Seral community succession, also known as linear succession, is a progression of communities where one stage makes the environment suitable for the next in a development leading to a climax. It is relatively common, especially in an aquatic environment, such as fish ponds or in any lake during eutrophication.

First, it is dominated by pioneer species like algae and floating plants, succeeded by submerged aquatic vegetation, and finally by terrestrial plants and shrubs. With every stage that the process goes through, the habitat is modified in such a way that it becomes more favourable for the establishment of the succeeding community. In other words, there is a net progression towards a more stable ecosystem state.

Examples of Ecological Succession

Examples of ecological succession are:

Volcanic Eruption (Mount St. Helens)

After the catastrophic eruption of Mount St. Helens in 1980, primary succession began immediately in the denuded landscape. The first to take over volcanic rock and ash were pioneer species such as lichens and mosses. After a couple of decades, the early colonizers died off and started building up some soil, which supported more complex plants like grasses and herbaceous species.

By the 2000s, young coniferous trees like lodgepole pine and western hemlock began to dominate, gradually building a forested ecosystem out of the landscape. This succession timeline exemplifies nature's incredible ability to regenerate and rebuild after catastrophes.

Pond Ecosystem Succession

One of the very impressive examples of ecological succession is the succession of a pond or lake ecosystem. Initially, almost every newly formed pond is colonized by algae and floating plants like duckweed. Sometime after this accumulation of organic matter and some sedimentation, emergent plants such as reeds and cattails may take hold along the edges. This makes the pond a marsh or wetland habitat.

Over time, once more filled in with organic material and sediment, shrubs and small trees may establish themselves, which can then more fully transition the ecosystem into a wooded wetland or swamp. This, therefore, shows the progress of succession from open water to a diverse mature wetland ecosystem.

Factors Influencing Ecological Succession

Succession is determined by a mixture of biological and physical properties.

Biological Factors

Competitive reasons related to species, which include competing for the same resources, like light and nutrients, are some of the reasons for community composition. Predation and symbiotic relationships, as in mycorrhizal association, affect population dynamics and nutrient cycling. If species diversity increases over time, it guarantees an increase in ecosystem complexity and resilience.

Physical Factors

The physical factors, such as climate, determine the species that may be favoured to occupy a particular area at any given time of the different succession stages. Soil characteristics, like pH and texture, ensure the availability of nutrients and water to plants for growth and establishment of plant communities. Other perturbations, such as fires or human activities added to these, may reset succession and thus alter community trajectories and diversity over time.

Human Activities

Human activities have a significant impact on ecological succession. Activities like deforestation, agriculture and industrialization can destroy communities present in the ecosystem. Pollution and climate change also alter the quality of soil, water and air, leading to secondary succession. On the other hand, some activities like reforestation and sustainable agricultural practices help in succession.

Ecological Succession and Ecosystem Services

Ecological succession is important for the maintenance of biodiversity in that it allows for an increase in habitat diversity and the varied existence of species. Succession thus confers resiliency against disturbance, increases productivity, and creates complex pathways of interactions and nutrient cycling. It is essential in sustaining healthy ecosystems that have inherent benefits such as habitat provision, water purification, and climate control.

Ecological Succession NEET MCQs (With Answers & Explanations)

Important topics that can be asked in NEET exam are:

• Types of Ecological Succession (Primary, Secondary, Cyclic, Seral Succession)

• Examples of Succession

• Impact of Human Activities (Deforestation, pollution, climate change)

Practice Questions for NEET

Q1. During the process of ecological succession the changes that take place in communities are:

1. Orderly and sequential

2. Random

3. Very quick

4. Not influenced by the physical environment

Correct answer: 1) Orderly and sequential

Explanation:

During ecological succession, communities undergo a series of stages, starting with pioneer species that modify the environment to make it more hospitable for other species. These changes include alterations in soil composition, nutrient availability, and habitat structures. As succession progresses, the community becomes more complex, with species diversity increasing until a stable climax community is formed, which is in equilibrium with the environment.

Hence, the correct answer is option 1) Orderly and sequentially.

Q2. Newly cooled lava, bare rock, and newly created pond or reservoir are the examples of areas where the succession occurs:

1. Primary succession

2. Secondary succession

3. Tertiary succession

4. Hydrarch succession

Correct answer: 1) Primary succession

Explanation:

Examples of places where primary succession takes place include recently formed ponds or reservoirs, bare rock, and freshly cooled lava.

In areas that were previously lifeless, such as following a volcanic explosion or the formation of a new body of water, primary succession takes place. To support increasingly complex ecosystems, the environment is first transformed by pioneer species like lichens and mosses.

Hence, the correct answer is option 1) Primary succession.

Q3. Recent studies on Archaea suggest that life could have originated

1. extraterrestrially and seeded through meteorite impacts.

2. in shallow coastal areas.

3. in deep hydrothermal vents.

4. in hot, terrestrial habitats.

Correct answer: 3) in deep hydrothermal vents.

Explanation:

Recent studies on Archaea have indeed provided evidence and support for the hypothesis that life could have originated in deep hydrothermal vents.

Archaea are a group of single-celled microorganisms that constitute one of the three domains of life, alongside Bacteria and Eukarya. They are known to thrive in extreme environments, including hydrothermal vents located deep in the ocean.

Hydrothermal vents are openings in the seafloor that release hot, mineral-rich water due to geothermal activity. These environments provide a unique combination of high temperatures, high pressure, and various chemical gradients, making them potential habitats for the origin of life.

Studies on Archaea, particularly those from deep-sea hydrothermal vents, have revealed several intriguing characteristics. These organisms possess unique metabolic capabilities and can utilize a wide range of energy sources, including hydrogen, sulfur compounds, and methane. They can also convert inorganic compounds into organic molecules through chemosynthesis.

Furthermore, hydrothermal vents contain mineral-rich chimneys composed of metal sulfides, which can serve as catalytic surfaces for chemical reactions and the formation of complex organic molecules. These chimneys could have provided a suitable environment for the emergence of early life forms.

Overall, the research on Archaea and the exploration of hydrothermal vent ecosystems have contributed to the hypothesis that life may have originated in these extreme environments. While further investigation is still needed, these studies have shed light on the potential habitats and processes that could have played a role in the origin of life on Earth.

Hence, the correct answer is option 3) in deep hydrothermal vents.

Also Read:

• MCQs on Ecological Succession

• Energy Flow in Ecosystem

• Biotic and Abiotic Components of Ecosystem

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