Category: Environment and Ecology

recommended for UPSC preparation:

These books provide solid foundational knowledge on environmental issues, biodiversity, ecology, and sustainable development, all of which are crucial for UPSC exams.

When we think of the savanna, we envision a dynamic ecosystem of grasslands and scattered trees, teeming with wildlife. Yet, beneath the surface, a less visible but equally vital force silently contributes to the health of the ecosystem: earthworms. In this blog post, we’ll dig into the fascinating world of earthworms in the savanna and explore their role as underground engineers shaping the very foundation of this diverse landscape.

1. Biodiversity Beneath the Surface:

While the charismatic megafauna and iconic trees of the savanna capture our attention, it’s essential to recognize the incredible biodiversity beneath our feet. Earthworms, belonging to various species, are crucial players in the intricate web of life. Their presence influences soil structure, nutrient cycling, and even the abundance of certain plant species.

2. Soil Aeration and Structure:

Earthworms are known for their ability to burrow through the soil, creating a network of channels that enhance aeration and water infiltration. In the savanna, where dry and wet seasons alternate, this natural aeration is crucial for maintaining soil health. By loosening the soil, earthworms create spaces for roots to grow, facilitating the movement of water, air, and nutrients through the ecosystem.

3. Nutrient Cycling and Soil Fertility:

Earthworms are masters of nutrient cycling. As they consume organic matter like fallen leaves and plant debris, they excrete nutrient-rich castings, often referred to as “black gold.” These castings are loaded with essential nutrients like nitrogen, phosphorus, and potassium, providing a natural fertilizer for the surrounding vegetation. In the savanna, where nutrient availability can be a limiting factor, earthworms play a critical role in sustaining the fertility of the soil.

4. Ecosystem Interactions:

The presence of earthworms influences various aspects of the savanna ecosystem. Their activities affect the distribution and abundance of plant species, as some plants are more dependent on the nutrient-rich environments created by earthworms. Additionally, the burrows and castings of earthworms serve as microhabitats for other organisms, contributing to overall biodiversity in the soil.

5. Adaptations to Savanna Conditions:

Earthworm species in the savanna have evolved specific adaptations to cope with the challenges of the environment. Some species are more resilient to the alternating dry and wet seasons, exhibiting behaviors such as burrowing deeper during dry periods and surfacing during wetter conditions.

List of Earthworms in Savanna

1. Eudrilus eugeniae: The Composting Earthworm

Known for its composting prowess, Eudrilus eugeniae, also called the African Nightcrawler, is a common inhabitant of the savanna. These earthworms are adept at breaking down organic matter, converting it into nutrient-rich castings that enhance soil fertility. Their activity is particularly crucial in regions with fluctuating moisture levels, such as the savanna.

2. Millsonia omodeoi: The Savanna Specialist

Endemic to the savanna ecosystems of Africa, Millsonia omodeoi is a burrowing earthworm species that has adapted to the specific conditions of these landscapes. Its burrows help aerate the soil, promoting better water infiltration and nutrient distribution, making it a key player in maintaining soil health.

3. Drawida willsi: The Deep Digger

In savannas where the soil can be compacted, Drawida willsi, or the African Blue Worm, stands out as a deep-digging earthworm. With a remarkable ability to burrow into harder soils, these worms contribute to soil structure improvement and provide pathways for water movement, crucial during both dry and wet seasons.

4. Amynthas gracilis: The Topsoil Transformer

Amynthas gracilis, commonly known as the Asian Jumping Worm, has made its way to various parts of the world, including some savanna regions. These invasive earthworms are known for their voracious appetite for leaf litter, transforming the topsoil by accelerating the breakdown of organic matter. While their impact can be complex, they are undeniably a part of the savanna earthworm community.

5. Polypheretima elongata: The Giant Savanna Earthworm

As the name suggests, Polypheretima elongata is a large earthworm species found in savannas. These giants contribute significantly to the ecosystem by creating extensive burrow systems, facilitating water movement, and enhancing the overall aeration of the soil.

Conclusion:

As we explore the wonders of the savanna, let’s not forget the hidden heroes beneath the surface—earthworms. These unsung underground engineers play a vital role in maintaining soil health, fostering biodiversity, and contributing to the resilience of the entire ecosystem. The savanna, with its diverse tapestry of life, owes much of its vitality to the silent, persistent work of these remarkable creatures.

When we think of savannas, we envision vast grasslands dotted with acacia trees and teeming with a diverse array of wildlife. However, hidden beneath the surface and often overlooked, there exists a fascinating and lesser-known world – the realm of mushrooms in the savanna. In this blog post, we will delve into the intriguing relationship between these enigmatic fungi and the unique ecosystems of the savanna.

The Challenge of Survival:

Savannas are characterized by their distinct dry and wet seasons, with a climate that can be harsh and unforgiving. The prevalence of grasses and scattered trees doesn’t immediately conjure images of mushroom-covered landscapes. Yet, mushrooms, being resilient organisms, have found ways to adapt and thrive even in these seemingly inhospitable conditions.

Seasonal Emergence:

One of the remarkable aspects of mushrooms in the savanna is their seasonal emergence. During the wet season, when the rains transform the landscape, the increased moisture provides an opportune environment for certain fungi to bloom. The mycelium, the underground network of fungal threads, responds to the changing conditions and gives rise to the fruiting bodies we recognize as mushrooms.

Hotspots of Fungal Activity:

While mushrooms might not be as abundant as in more traditionally fungal-friendly environments like forests, there are specific hotspots in the savanna where fungal activity is more pronounced. Areas around the bases of trees, where organic matter accumulates, and locations enriched with animal dung become fertile grounds for mushroom growth. These pockets of life showcase the adaptability and resourcefulness of fungi in the face of challenging surroundings.

Biodiversity of Savanna Mushrooms:

The mushrooms found in savannas vary widely, depending on the local climate, soil composition, and the types of vegetation present. Some species are well-adapted to the specific conditions of savannas, playing crucial roles in nutrient cycling and ecosystem dynamics. Exploring the biodiversity of savanna mushrooms unveils a rich tapestry of colors, shapes, and ecological interactions that contribute to the overall health of these ecosystems.

Types of mushrooms in the savanna

1. Termitomyces titanicus: The Termite Mound Mushroom

One of the most fascinating mushrooms found in savannas is the Termitomyces titanicus. As its name suggests, this colossal fungus often emerges near termite mounds. These mushrooms have a mutually beneficial relationship with termites, forming a mycorrhizal association that aids both organisms. The termites provide a conducive environment for the fungus to grow, and in return, the fungus helps break down organic matter, recycling nutrients for the benefit of the entire ecosystem.

2. Amanita jacksonii: The Savanna Caesar

Recognizable by its striking orange to red cap and white warts, Amanita jacksonii is a mycorrhizal mushroom that forms symbiotic relationships with trees in the savanna. This species is not only aesthetically pleasing but also serves an essential ecological role in nutrient exchange with its host plants.

3. Psilocybe cubensis: The Magic Mushroom

In some savanna regions, particularly those with higher humidity levels, you might encounter Psilocybe cubensis. Known for its psychoactive properties, this mushroom has been used in cultural practices for centuries. It’s crucial to approach such mushrooms with caution, respecting their cultural significance and understanding the potential risks associated with their consumption.

4. Laccaria bicolor: The Beneficial Mycorrhizal Partner

Laccaria bicolor is a mycorrhizal fungus commonly found in savannas. It forms symbiotic relationships with various trees, aiding in nutrient uptake and enhancing the trees’ ability to withstand stress. The delicate, colorful caps of Laccaria bicolor add a touch of beauty to the savanna floor while silently contributing to the health and resilience of the ecosystem.

5. Panaeolus africanus: The Dung-loving Mushroom

In savannas, where large herbivores roam, mushrooms like Panaeolus africanus thrive in areas with animal dung. These saprophytic mushrooms play a vital role in breaking down organic matter, recycling nutrients, and contributing to the nutrient cycle in the savanna ecosystem.

Conclusion:

Mushrooms in the savanna may not steal the spotlight from the charismatic megafauna or the iconic baobab trees, but they play an essential role in the intricate web of life in these environments. As we continue to explore and understand the diversity of life on our planet, let’s not forget to marvel at the hidden wonders beneath our feet, where mushrooms in the savanna quietly contribute to the magic of these remarkable landscapes.

• The food chain is disrupted. Primary consumers eat plants, and secondary consumers eat primary consumers. When primary and secondary consumers die, there is no one to eat the plants, which can lead to a decrease in plant populations. This can have a cascading effect on the entire ecosystem, as other animals that depend on plants for food may also die.
• The nutrient cycle is disrupted. When primary and secondary consumers die, their bodies decompose and their nutrients are released back into the soil. These nutrients are then available for plants to absorb, which helps to keep the soil healthy. When primary and secondary consumers die, these nutrients are not released back into the soil, which can lead to soil degradation.
• The ecosystem becomes less diverse. As primary and secondary consumers die, the number of species in the ecosystem decreases. This can make the ecosystem more vulnerable to changes, as there are fewer species to help maintain the balance of the ecosystem.

It is important to note that the effects of the death of primary and secondary consumers will vary depending on the specific ecosystem. In some ecosystems, the effects may be more severe than in others.

Ecological Pyramid

The ecological pyramid is a graphical representation to show the relationship between various organisms at various trophic levels in an ecosystem.

The concept of the ecological pyramid was first introduced by Charles Elton in 1927.

The base of a pyramid is broad and its apex is narrow. The shape is the same for the food or energy relationship between organisms at different tropic levels. The relationship between food and energy between organisms at various trophic levels is expressed in terms of number, biomass or energy.

The base of the pyramid represents producers (First tropic Level). The apex represents tertiary consumers (top-level consumers).

Usually, 3 Types of Pyramids are studied they are:

• Pyramid of Number
• Pyramid of Biomass
• Pyramid of Energy

Pyramid of Number

A pyramid of numbers is a graphical representation of the number of organisms at each trophic level in an ecosystem. The base of the pyramid represents the producers, which are the organisms that make their own food, such as plants. The next level of the pyramid represents the primary consumers, which are the organisms that eat the producers, such as herbivores. The next level represents the secondary consumers, which are the organisms that eat the primary consumers, such as carnivores. The pyramid can continue to higher levels, but the number of organisms typically decreases at each level.

There are three main types of pyramids of numbers:

• Upright pyramid: This is the most common type of pyramid of numbers, and it shows that there are typically more producers than primary consumers, more primary consumers than secondary consumers, and so on.
• Inverted pyramid: This type of pyramid of numbers is less common, and it shows that there are fewer producers than primary consumers, fewer primary consumers than secondary consumers, and so on.
• Partially upright pyramid: This type of pyramid of numbers is the most common in terrestrial ecosystems, and it shows that there are typically more producers than primary consumers, but fewer primary consumers than secondary consumers.

The shape of a pyramid of numbers can be affected by a number of factors, including the size and reproductive rate of the organisms at each trophic level, the efficiency of energy transfer between trophic levels, and the environmental conditions in the ecosystem.

Here is an example of a pyramid of numbers for a grassland ecosystem:

Producers: 100,000
Primary consumers: 10,000
Secondary consumers: 1,000
Tertiary consumers: 100

• Only three top carnivores could be supported in an ecosystem of nearly 6 Million plants.

Pyramid of Biomass

• In the Pyramid of Biomass, there is a sharp decrease in biomass at higher trophic levels.

A biomass pyramid is a graphical representation of the total mass of living organisms at each trophic level in an ecosystem. Biomass is typically measured in grams or kilograms per square meter or per cubic meter.

The base of the pyramid represents the producers, which are the organisms that make their own food, such as plants. The next level of the pyramid represents the primary consumers, which are the organisms that eat the producers, such as herbivores. The next level represents the secondary consumers, which are the organisms that eat the primary consumers, such as carnivores. The pyramid can continue to higher levels, but the total biomass typically decreases at each level.

There are three main types of pyramids of biomass:

Upright pyramid: This is the most common type of pyramid of biomass, and it shows that there is typically more biomass at lower trophic levels than at higher trophic levels. This is because only a small fraction of the energy that is captured by the producers is actually transferred to the next trophic level.

Inverted pyramid: This type of pyramid of biomass is less common, and it shows that there is more biomass at higher trophic levels than at lower trophic levels. This is typically only seen in marine ecosystems, where the producers, such as phytoplankton, are very small and very efficient at capturing energy from sunlight.

Partially upright pyramid: This type of pyramid of biomass is the most common in terrestrial ecosystems, and it shows that there is typically more biomass at lower trophic levels than at higher trophic levels, but the difference is not as great as in an upright pyramid.

The shape of a pyramid of biomass can be affected by a number of factors, including the size and reproductive rate of the organisms at each trophic level, the efficiency of energy transfer between trophic levels, and the environmental conditions in the ecosystem.

Here is an example of a pyramid of biomass for a grassland ecosystem:

Producers: 10,000 g/m^2
Primary consumers: 1,000 g/m^2
Secondary consumers: 100 g/m^2
Tertiary consumers: 10 g/m^2

As you can see, there is more biomass at lower trophic levels than at higher trophic levels. This is an example of an upright pyramid of biomass.

Pyramids of biomass are a useful tool for understanding the relationships between different trophic levels in an ecosystem. They can also be used to identify potential problems in an ecosystem, such as an overpopulation of a particular species.

Inverted Pyramid of Biomass

• In the inverted pyramid of biomass, a very small crop of phytoplankton supports large zooplankton.

In contrast to the typical pyramid of biomass, where the biomass of producers at the base of the food chain is greater than the biomass of consumers at higher levels, an inverted pyramid of biomass occurs when the biomass of consumers exceeds the biomass of producers. This phenomenon is most commonly observed in aquatic ecosystems, particularly in marine environments.

Several factors contribute to the occurrence of inverted pyramids of biomass in aquatic ecosystems:

1. Rapid Growth and Short Lifespan of Producers: Phytoplankton, the primary producers in marine ecosystems, have a rapid growth rate and a short lifespan. They efficiently capture energy from sunlight and quickly convert it into biomass. This rapid turnover of phytoplankton contributes to a large standing stock of biomass despite their small size.
2. Efficient Energy Transfer: Zooplankton, the primary consumers in marine ecosystems, are highly efficient at capturing and utilizing the energy from phytoplankton. They consume a significant portion of the phytoplankton biomass, leading to a relatively high biomass of zooplankton compared to phytoplankton.
3. Detritus-Based Food Webs: Marine ecosystems often have a substantial detritus-based food web, where organic matter from dead organisms serves as a food source for detritus feeders. Detritus feeders, such as crustaceans and worms, contribute to the overall biomass of consumers in the ecosystem.
4. Biomass Accumulation in Long-Lived Consumers: In some marine ecosystems, top predators, such as large fish or sharks, can have a long lifespan and accumulate substantial biomass over time. This can contribute to an inverted pyramid of biomass, as the biomass of these top predators may exceed the combined biomass of all lower trophic levels.

Examples of inverted pyramids of biomass include:

• Upwelling Ecosystems: In upwelling ecosystems, nutrient-rich water from deeper ocean layers rises to the surface, stimulating phytoplankton growth. This leads to a large abundance of phytoplankton, which supports a high biomass of zooplankton and other consumers.
• Coral Reef Ecosystems: Coral reefs provide a complex habitat that supports a diverse array of organisms, including a large biomass of zooplankton and fish. The rapid growth and turnover of coral reef organisms contribute to an inverted pyramid of biomass.

Inverted pyramids of biomass highlight the unique characteristics of aquatic ecosystems and the importance of efficient energy transfer within these systems. They also demonstrate the role of detritus-based food webs and the impact of long-lived top predators on the overall structure of the ecosystem.

Pyramid of Energy

• The primary producers utilize and convert only 1% of the energy in the sunlight into NPP.

An energy pyramid, also known as an ecological pyramid, is a graphical representation of the flow of energy within a food chain or ecosystem. It depicts the transfer of energy from one trophic level to the next, starting with the primary producers at the base of the pyramid and moving up to secondary consumers, tertiary consumers, and apex predators at the top.

The energy pyramid illustrates the fundamental principle of ecology that energy cannot be created or destroyed, only transferred and transformed. As energy moves up the pyramid, a significant portion is lost at each level due to respiration, excretion, and other metabolic processes. Therefore, the amount of energy available to higher trophic levels diminishes as we move from the base to the top of the pyramid.

Characteristics of Energy Pyramids:

1. Uni-directional flow: Energy flows in one direction, from producers to consumers.
2. Decreasing energy: The amount of energy available decreases at each trophic level.
3. Limited transfer efficiency: Only a small fraction of energy (typically 10-20%) is transferred from one level to the next.
4. Ecological stability: Energy pyramids reflect the stability and balance of an ecosystem.

Types of Energy Pyramids:

1. Upright Pyramid: The most common type, representing the general pattern of energy flow in most ecosystems.
2. Inverted Pyramid: Less common, typically found in marine ecosystems where phytoplankton are highly efficient energy capturers.
3. Partially Upright Pyramid: Combines features of upright and inverted pyramids, often seen in terrestrial ecosystems.

Significance of Energy Pyramids:

1. Understanding energy flow: Energy pyramids provide a visual representation of energy transfer within ecosystems.
2. Predicting ecological impacts: Changes in energy pyramid structure can indicate ecological disturbances or imbalances.
3. Guiding human interventions: Energy pyramids inform sustainable resource management and conservation practices.
4. Demonstrating ecological principles: Energy pyramids illustrate the concept of energy flow and the interconnectedness of organisms within an ecosystem.

Calculation of Energy Content

When calculating the energy content, the numbers of biomass. One needs to include all the organisms at that particular tropic level. If we take only a few individuals at any tropic level or generalisation will not give current values.

The important thing is trophic level represents a functional level, not a species.

Species with multiple tropical levels

For example, Sparrow is a primary consumer, when it consumes fruits, peas etc. The same sparrow becomes a secondary consumer when it consumes insects and worms. Similarly, humans are part of multiple trophic levels.

Many species occupy multiple trophic levels within an ecosystem, meaning they derive sustenance from different sources across various levels of the food chain. This adaptability and flexibility allow them to thrive in diverse environments and contribute to the stability of ecological systems.

Here are some examples of species that occupy multiple trophic levels:

1. Giant Panda: Primarily herbivorous, consuming bamboo as their main food source, giant pandas occasionally scavenge for small mammals, insects, and eggs, placing them in both primary and secondary consumer roles.
2. Salmon: Salmon undergo a remarkable transformation throughout their life cycle. As juveniles in freshwater, they feed on plankton as primary consumers. Upon migrating to the ocean, they transition to a predatory diet, consuming fish and crustaceans as secondary consumers.
3. Omnivores: By definition, omnivores occupy multiple trophic levels, consuming both plant and animal matter. Humans, raccoons, bears, and many birds are examples of omnivores.
4. Parasitic Organisms: Parasites extract nutrients and energy from their hosts, effectively occupying two trophic levels simultaneously. Tapeworms, leeches, and fleas are examples of parasites.
5. Detritivores: Detritivores derive sustenance from decaying organic matter, breaking down detritus and recycling nutrients back into the ecosystem. Earthworms, vultures, and many insects are detritivores.

These examples demonstrate the diverse strategies employed by species to occupy multiple trophic levels. These adaptations allow them to exploit various food sources, enhance their survival, and contribute to the complex web of interactions within ecosystems.

The ecological pyramid is always upright

In most ecosystem, the Pyramids of Biomass, energy, and number is always upright. For example,

• Producers are more in number and biomass than the herbivores,
• Herbivores are more in number and biomass than carnivores.

But importantly, there are exceptions. Such as insects feeding on trees. The number of insects is very high.

Also, the pyramid of biomass in the sea is generally inverted. The biomass of fishes exceeds the phytoplankton.

Pyramid of Energy is always Upright

The pyramid of energy is always upright and it is never inverted. This is because the energy flows from a particular trophic level to the next trophic level. As a result, some energy is always lost as heat at every step.

Each bar in the energy pyramid indicates the amount of energy present at each trophic level at a given time or annually per unit area.

Conclusion

However, there are some limitations of ecological pyramids. As it does not take into account the same species belonging to two or more trophic levels.

Also, the ecological pyramid assumes a simple food chain that never exists in nature and it does not accommodate a food web.

Also, saprophytes are not given any place in ecological pyramids even though
they have an important role in the ecosystem.

References

• https://ncert.nic.in/textbook/pdf/lebo114.pdf

Aquatic Zone definition

An aquatic zone is a region of a body of water that is characterized by its physical and biological features. Aquatic zones can be divided into a number of different types, based on factors such as depth, sunlight availability, and substrate type.

Some of the most common types of aquatic zones include:

The littoral zone

The littoral zone, also referred to as the litoral or nearshore zone, is the area of a sea, lake, or river situated close to the shore. In coastal ecology, this zone encompasses the intertidal region, stretching from the high water mark rarely submerged to areas that remain permanently underwater, known as the foreshore. While the terms “littoral zone” and “intertidal zone” are sometimes used interchangeably, the geographical definition of the littoral zone extends beyond the intertidal region, including all neritic waters within the limits of continental shelves.

• The pelagic zone: This is the open water of a lake or ocean. It is characterized by a lack of sunlight and a high abundance of plankton.
• The benthic zone: This is the bottom of a lake or ocean. It is characterized by a lack of sunlight and a high abundance of benthic organisms, such as worms, clams, and fish.

Aquatic zones are important habitats for a wide variety of organisms. They provide food, shelter, and breeding grounds for many different species of fish, algae, and invertebrates. Aquatic zones also play an important role in the global water cycle and the regulation of the Earth’s climate.

Here are some of the factors that can affect the characteristics of an aquatic zone:

• Depth: The depth of a body of water affects the amount of sunlight that reaches the bottom. This, in turn, affects the types of organisms that can live in the zone.
• Sunlight availability: The amount of sunlight that reaches a body of water affects the types of plants that can grow in the zone.
• Substrate type: The type of substrate at the bottom of a body of water affects the types of organisms that can live in the zone. For example, sandy substrates are more likely to support burrowing organisms, while rocky substrates are more likely to support sessile organisms.
• Turbidity: Turbidity is the amount of suspended particles in a body of water. Turbid water blocks sunlight, which can affect the types of organisms that can live in the zone.
• Temperature: The temperature of a body of water affects the types of organisms that can live in the zone. For example, cold water is more likely to support fish species that are adapted to cold temperatures.

Aquatic zones are important and diverse ecosystems that play a vital role in the Earth’s environment. By understanding the different types of aquatic zones and the factors that affect them, we can better understand the importance of these ecosystems and how to protect them.

Fresh

Mangroves

Here are 5 food chain examples:

1. Grass → Rabbit → Fox → Wolf

This is a simple food chain that can be found in many different ecosystems. The grass is the producer, the rabbit is the primary consumer, the fox is the secondary consumer, and the wolf is the tertiary consumer.

2. Kelp → Krill → Fish → Seal → Killer whale

This is a food chain that can be found in the ocean. The kelp is the producer, the krill are the primary consumers, the fish are the secondary consumers, the seal is the tertiary consumer, and the killer whale is the quaternary consumer.

3. Tree → Caterpillar → Bird → Snake → Hawk

This is a food chain that can be found in forests. The tree is the producer, the caterpillar is the primary consumer, the bird is the secondary consumer, the snake is the tertiary consumer, and the hawk is the quaternary consumer.

4. Cacti → Insects → Lizard → Hawk

This is a food chain that can be found in deserts. The cacti are the producers, the insects are the primary consumers, the lizards are the secondary consumers, and the hawk is the tertiary consumer.

5. Plankton → Small fish → Large fish → Shark

This is a food chain that can be found in the ocean. The plankton are the producers, the small fish are the primary consumers, the large fish are the secondary consumers, and the shark is the tertiary consumer.

Energy flow in an ecosystem

Energy flow in an ecosystem refers to the transfer of energy through various trophic levels, from producers to consumers and decomposers. It starts with solar energy captured by plants through photosynthesis, which is then passed on to herbivores and carnivores through feeding relationships.

Decomposers break down organic matter, returning essential nutrients to the soil, completing the cycle. Understanding energy flow is crucial to studying ecosystem dynamics, as it helps explain how organisms interact, maintain balance, and sustain life. In this blog, we’ll explore the various stages of energy flow and its importance in maintaining ecological equilibrium.

Photosynthetically Active Radiation

Except for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth. Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR). We know that plants and photosynthetic bacteria (autotrophs), fix Sun’s radiant energy to make food from simple inorganic materials.

Plants capture only 2-10 per cent of the PAR and this small amount of energy sustains the entire living world. So, it is very important to know how the solar energy captured by plants flows through different organisms of an ecosystem. All organisms are dependent for their food on producers, either directly or indirectly.

So you find unidirectional flow of energy from the sun to producers and then to consumers. Is this in keeping with the first law of thermodynamics?

Further, ecosystems are not exempt from the Second Law of thermodynamics. They need a constant supply of energy to synthesise the molecules they require, to counteract the universal tendency toward increasing disorderliness.

The green plant in the ecosystem are called producers. In a terrestrial ecosystem, major producers are herbaceous and woody plants. Likewise, producers in an aquatic ecosystem are various species like phytoplankton, algae and higher plants.

Starting from the plants (or producers) food chains or rather webs are formed such that an animal feeds on a plant or on another animal and in turn is food for another. The chain or web is formed because of this interdependency. No energy that is trapped into an organism remains in it for ever.

The energy trapped by the producer, hence, is either passed on to a consumer or the organism dies. Death of organism is the beginning of the detritus food chain/web.

All animals depend on plants (directly or indirectly) for their food needs. They are hence called consumers and also heterotrophs. If they feed on the producers, the plants, they are called primary consumers, and if the animals eat other animals which in turn eat the plants (or their produce) they are called secondary consumers. Likewise, you could have tertiary consumers too.

Obviously the primary consumers will be herbivores. Some common herbivores are insects, birds and mammals in terrestrial ecosystem and molluscs in aquatic ecosystem. The consumers that feed on these herbivores are carnivores, or more correctly primary carnivores (though secondary consumers). Those animals that depend on the primary carnivores for food are labelled secondary carnivores. A simple grazing food chain (GFC) is depicted
below:

These producers and consumers can be organized into the food chains and food web. These food chains are organized into trophic pyramids

Energy flow is The detritus food chain (DFC) begins with dead organic matter. It is made up of decomposers which are heterotrophic organisms, mainly fungi and bacteria. They meet their energy and nutrient requirements by degrading dead organic matter or detritus.

These are also known as saprotrophs (sapro: to decompose). Decomposers secrete digestive enzymes that breakdown dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them.

In an aquatic ecosystem, GFC is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the GFC. Detritus food chain may be connected with the grazing food chain at some levels:

some of the organisms of DFC are prey to the GFC animals, and in a natural ecosystem, some animals like cockroaches, crows, etc., are omnivores. These natural interconnection of food chains make it a food web.

How would you classify human beings! Organisms occupy a place in the natural surroundings or in a community according to their feeding relationship with other organisms.

Based on the source of their nutrition or food, organisms occupy a specific place in the food chain that is known as their trophic level. Producers belong to the first trophic level, herbivores (primary consumer) to the second and carnivores (secondary consumer) to the third.

The important point to note is that the amount of energy decreases at successive trophic levels. When any organism dies it is converted to detritus or dead biomass that serves as an energy source for decomposers.

Organisms at each trophic level depend on those at the lower trophic level for their energy demands.

Each trophic level has a certain mass of living material at a particular time called as the standing crop. The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area. The biomass of a species is expressed in terms of fresh or dry weight. Measurement of biomass in terms of dry weight is more accurate.

Why? The number of trophic levels in the grazing food chain is restricted as the transfer of energy follows 10 per cent law – only 10 per cent of the energy is transferred to each trophic level from the lower trophic level. In nature, it is possible to have so many levels – producer, herbivore, primary carnivore, secondary carnivore in the grazing food chain (Figure 14.3) .

Do you think there is any such limitation in a detritus food chain?

This framework illustrates the unidirectional flow of energy, governed by the laws of thermodynamics, ensuring the continuous functioning of ecosystems.

Download

1.Energy flow in ecosystem upsc pdf