Ecosystem

The ecosystem is the structural and functional unit of ecology where living organisms interact with each other and the surrounding environment. In other words, an ecosystem is a network of interactions between organisms and their environment. The term "ecosystem" was first coined by A.G. Tansley, an English botanist, in 1935.

The organisms in an ecosystem are usually well balanced with each other and with their environment. An ecosystem may be natural or artificial, land-based or water-based. Artificial systems may include a cropland, a garden, a park or an aquarium. Introduction of new environmental factors or new species can have disastrous results, eventually leading to the collapse of an ecosystem and the death of many of its native species. Some of the major non-living factors of an ecosystem are: Sunlight, Water, Temperature, Oxygen, Soil, Air.

Types of Ecosystem

An Ecosystem can be as small as an oasis in a desert, Or as big as an ocean, spanning thousands of miles.

Ecosystems can be classified into three main scales:-

• Micro: A small scale ecosystem such as a pond, puddle, tree trunk, under a rock etc.
• Messo: A medium scale ecosystem such as a forest or a large lake.
• Biome: A very large ecosystem or collection of ecosystems with similar biotic and abiotic factors such as an entire Rainforest with millions of animals and trees, with many different water bodies running through them.

There Are Two Types Of Ecosystem:-

1. Terrestrial Ecosystem
2. Aquatic Ecosystem

Terrestrial Ecosystem

Terrestrial ecosystems are exclusively land-based ecosystems. There are different types of terrestrial ecosystems distributed around various geological zones. They are as follows:-

1. Forest Ecosystems
2. Grassland Ecosystems
3. Tundra Ecosystems
4. Desert Ecosystem

Forest Ecosystem

A forest ecosystem consists of several plants, animals and microorganisms that live in coordination with the abiotic factors of the environment. Forests help in maintaining the temperature of the earth and are the major carbon sink.

Grassland Ecosystem

In a grassland ecosystem, the vegetation is dominated by grasses and herbs. Temperate grasslands, savanna grasslands are some of the examples of grassland ecosystems.

Tundra Ecosystem

Tundra ecosystems are devoid of trees and are found in cold climates or where rainfall is scarce. These are covered with snow for most of the year. The ecosystem in the Arctic or mountain tops is tundra type.

Desert Ecosystem

Deserts are found throughout the world. These are regions with very little rainfall. The days are hot and the nights are cold.

Aquatic Ecosystem

Aquatic ecosystems are ecosystems present in a body of water. These can be further divided into two types, namely:-

1. Freshwater Ecosystem
2. Marine Ecosystem

Freshwater Ecosystem

The freshwater ecosystem is an aquatic ecosystem that includes lakes, ponds, rivers, streams and wetlands. These have no salt content in contrast with the marine ecosystem.

Marine Ecosystem

The marine ecosystem includes seas and oceans. These have a more substantial salt content and greater biodiversity in comparison to the freshwater ecosystem.

Structure of Ecosystem

The structure of an ecosystem is characterized by the organization of both biotic and abiotic components. This includes the distribution of energy in our environment. It also includes the climatic conditions prevailing in that particular environment.

The structure of an ecosystem can be split into two main components, namely:

1. Biotic Components
2. Abiotic Components

The biotic and abiotic components are interrelated in an ecosystem. It is an open system where the energy and components can flow throughout the boundaries.

Biotic Components

Biotic components refer to all life in an ecosystem. Based on nutrition, biotic components can be categorised into autotrophs, heterotrophs and saprotrophs (or decomposers).

Producers include all autotrophs such as plants. They are called autotrophs as they can produce food through the process of photosynthesis. Consequently, all other organisms higher up on the food chain rely on producers for food.

Consumers or heterotrophs are organisms that depend on other organisms for food. Consumers are further classified into primary consumers, secondary consumers and tertiary consumers.

• Primary consumers are always herbivores that they rely on producers for food.
• Secondary consumers depend on primary consumers for energy. They can either be a carnivore or an omnivore.
• Tertiary consumers are organisms that depend on secondary consumers for food. Tertiary consumers can also be an omnivore.
• Quaternary consumers are present in some food chains. These organisms prey on tertiary consumers for energy. Furthermore, they are usually at the top of a food chain as they have no natural predators.

Decomposers include saprophytes such as fungi and bacteria. They directly thrive on the dead and decaying organic matter. Decomposers are essential for the ecosystem as they help in recycling nutrients to be reused by plants.

Abiotic Components

Abiotic components are the non-living component of an ecosystem. It includes air, water, soil, minerals, sunlight, temperature, nutrients, wind, altitude etc.

• Sunlight: Sunlight is the primary source of energy for all living things. It provides light and heat, which is essential for plants to make their food through a process called photosynthesis.
• Air (Atmosphere): The air around us is made up of different gases like oxygen, nitrogen, and carbon dioxide. Living organisms, especially animals, need oxygen from the air to breathe and survive.
• Water: Water is vital for life. It is used by plants and animals for various purposes, such as drinking, bathing, and supporting plant growth. Without water, life cannot exist.
• Soil: Soil is the layer of earth where plants grow their roots. It provides nutrients and support to plants. The soil is made up of small pieces of rock, minerals, organic matter (like dead plants and animals), and water.
• Temperature: Temperature refers to how hot or cold the environment is. Different living things thrive in different temperature ranges, and extreme temperatures can affect their survival.
• Climate: Climate is the long-term pattern of weather conditions in an area. It includes factors like temperature, humidity, and precipitation. Climate influences the types of plants and animals that can live in an ecosystem.

Functions of Ecosystem

• Ecosystems regulate essential ecological processes, such as nutrient cycling and energy flow, which support life systems and maintain stability within environments.
• They facilitate the cycling of nutrients between biotic and abiotic components, ensuring the availability of essential elements for living organisms.
• Ecosystems maintain a balance among various trophic levels by regulating population dynamics and resource availability.
• They play a crucial role in the cycling of minerals through the biosphere, contributing to the overall nutrient balance and ecosystem functioning.
• Abiotic components within ecosystems contribute to the synthesis of organic matter, facilitating energy exchange processes essential for sustaining life.

Ecological Succession

Ecological succession refers to the process by which the structure and composition of a biological community change over time in response to changing environmental conditions. It is a natural and gradual process that occurs in ecosystems, leading to the establishment of a stable and diverse community. Succession typically begins in areas where there is no existing community, such as bare rock or barren land, and progresses until a climax community is reached. A climax community is the “endpoint” of succession within the context of a particular climate and geography.

The area in which the order of communities undergoes a specific change is called sere. Each changing community is therefore called a seral community. All communities around us have undergone ecological succession ever since their existence was identified. Evolution thus is a simultaneously occurring process along with ecological succession. Also, the initiation of life on earth can be considered to be a result of this succession process.

Five Stages of Ecological Succession

• Nudation: Nudation is the initial stage of ecological succession where a bare, uninhabited substrate becomes available for colonization by pioneer species due to disturbances such as volcanic eruptions, landslides, or glacial retreat.
• Invasion: Invasion occurs as pioneer species, typically characterized by rapid growth and reproduction rates, colonize the newly available habitat. These pioneer species, often including lichens, mosses, and fast-growing grasses, begin to establish themselves in the environment.
• Competition and Co-action: As more species colonize the area, competition for resources such as light, water, nutrients, and space intensifies. Competitive interactions between species shape community composition, leading to the coexistence of species that can tolerate similar environmental conditions.
• Reaction: The reaction stage involves further changes in community structure and composition as species interactions, such as predation, herbivory, and mutualism, become more pronounced. These interactions influence the abundance and distribution of species within the ecosystem.
• Stabilization or Climax: The final stage of ecological succession, stabilization or climax, occurs when the ecosystem reaches a relatively stable state known as a climax community. In this stage, species composition and environmental conditions remain relatively constant over time, with the community achieving a dynamic equilibrium. The climax community is adapted to the prevailing environmental conditions and represents the endpoint of succession under those conditions.

Characteristics of Ecological Succession

1. Directional Change: Ecological succession involves a gradual shift in species composition and community structure over time.

2. Response to Environmental Changes: Succession occurs in response to environmental disturbances, such as fires, floods, or human activities, creating opportunities for new species to establish.

3. Pioneer Species: Pioneer species are the first to colonize a newly available habitat or disturbed area, initiating succession by adapting to harsh conditions and facilitating soil development.

4. Facilitation: Pioneer species modify the environment, making it more suitable for the growth of other species through processes like soil improvement and habitat creation.

5. Competition: Competitive interactions among species intensify as succession progresses, influencing community composition and successional trajectories.

Types of Ecological Succession

Primary Succession

Primary succession occurs in environments where there is no pre-existing community, such as on newly formed volcanic islands, bare rock surfaces left by retreating glaciers, or after a severe disturbance like a landslide.

In primary succession, the process starts with the colonization of pioneer species, which are often hardy, fast-growing organisms such as lichens and mosses. These pioneer species help to break down rocks and organic matter, gradually creating soil. Over time, more complex plants like grasses and shrubs establish themselves, followed by trees.

As the ecosystem matures, the diversity of plant and animal species increases, eventually leading to the development of a stable and self-sustaining climax community.

Secondary Succession

Secondary succession occurs in environments where a pre-existing community has been disturbed or partially destroyed, such as after a forest fire, flood, or human activities like logging or agriculture.

Unlike primary succession, where soil formation is the starting point, secondary succession begins with a layer of soil already present. The process involves the re-establishment of vegetation and the gradual recovery of the ecosystem. Pioneer species, often seeds and spores present in the soil or dispersed from nearby areas, colonize the disturbed area and begin to rebuild the community.

Over time, as the ecosystem regenerates, more complex plant and animal species return, leading to the eventual restoration of a diverse and stable community similar to the pre-disturbance state.

Differeence Between Primary And Secondary Succession

Ecological Pyramids

An ecological pyramid is a graphical representation illustrating the relationship among different living organisms at various trophic levels. It was originally proposed by G. Evelyn Hutchinson and Raymond Lindeman.

These pyramids typically take the shape of actual pyramids, with the broadest base representing the lowest trophic level - comprising producers. Successive levels then ascend, representing higher trophic levels such as primary consumers and so forth.

From the producer level to the consumer level, there is a gradual decrease in the number, biomass, and energy of organisms.

In essence, an ecological pyramid serves to showcase the relative amount of energy or matter contained within each trophic level.

Types of Ecological Pyramids

There are three main types of ecological pyramids, each representing different aspects of energy flow and biomass within an ecosystem:-

Pyramid of Numbers

This type of ecological pyramid depicts the number of individual organisms present at each trophic level in an ecosystem. The base of the pyramid represents the primary producers, and successive layers represent the various consumer levels, with the tertiary consumers at the top. In detritus food chains or ecosystems, such as decomposer-based ecosystems or ecosystems centered around dead organic matter, the pyramid of numbers can be inverted. This occurs when a large number of decomposers feed on a single dead plant or animal, resulting in a higher number of organisms at higher trophic levels compared to the producers at the base of the pyramid.

Pyramid of Biomass

The pyramid of biomass serves as a graphical representation of the total biomass present at each trophic level within an ecosystem. In a grassland ecosystem, for instance, the pyramid of biomass is typically upright. At the base of the pyramid are the primary producers, such as grasses, which boast the highest biomass. As we ascend the pyramid, successive layers represent various consumer levels, including primary consumers (herbivores), secondary consumers (predators of herbivores), and tertiary consumers (top predators). Each higher trophic level tends to contain less biomass than the one below it, reflecting the energy loss that occurs as energy is transferred up the food chain.

Conversely, in a marine ecosystem, the pyramid of biomass may be inverted. This inversion occurs due to the high biomass of primary producers, such as phytoplankton, which forms the base of the pyramid. Successive trophic levels, including primary consumers (zooplankton) and secondary consumers (small fish), may have lower biomass than the primary producers. This inversion is often observed in ecosystems where the rate of reproduction and turnover of primary producers is exceptionally high, resulting in a substantial biomass despite being consumed rapidly by higher trophic levels.

Pyramid of Energy

The pyramid of energy represents the flow of energy through different trophic levels in an ecosystem. At the base of the pyramid are the primary producers, which capture energy from external sources such as sunlight through photosynthesis. Successive layers depict various consumer levels, with each layer containing less energy than the one below it due to energy loss. This energy loss occurs as heat at each trophic level, reducing the amount of energy available to the next level.

Importance And Limitations of Ecological Pyramids

Importance

• Ecological pyramids depict the feeding relationships among organisms in diverse ecosystems.
• They offer insights into the efficiency of energy transfer between trophic levels.
• Ecological pyramids aid in monitoring ecosystem health, enabling timely intervention to prevent further degradation.

Limitations

• These pyramids do not account for variations in food availability and energy flow caused by seasonal changes and climatic fluctuations.
• Despite their significant contribution to ecosystem dynamics, saprophytes are often omitted from ecological pyramids.
• Ecological pyramids are primarily applicable to simple food chains, which may not accurately represent natural ecosystems.