The Brilliant Chain: How Energy Is Transferred in Ecosystems with Precision

Energy transfer in an ecosystem is a fundamental process that sustains life and drives
ecological interactions. It occurs through the interconnected food web and food chain
within an ecosystem. It follows the first law of thermodynamics (Law of Energy
Conservation), specifically the laws of energy conservation and entropy, which state that
“energy cannot be created or destroyed but can be transformed from one form to another”

New to ecosystems? Start with our beginner-friendly article on what an ecosystem is, so you can better understand how energy flows within it.

Energy transfer occurs through the interconnected food web and food chain within an
ecosystem. Let’s examine how energy flows through these systems and discuss their
critical aspects.

Food Chains: A food chain is a linear sequence that illustrates how energy is transferred from one organism to another within an ecosystem. Energy in most ecosystems originates from the sun through solar radiation. This solar energy is first captured by primary producers such as green plants, algae, and phytoplankton through photosynthesis. These producers form the base of the food chain and pass energy on to herbivores, which are then consumed by carnivores and other higher-level consumers.
In ecosystems, energy transfer begins when producers like green plants convert sunlight into chemical energy through the process of photosynthesis. This stored energy is then passed on to primary consumers, which are herbivores such as deer, antelopes, zebras, giraffes, squirrels, caterpillars, and rabbits that feed on these plants. From there, energy flows through the food chain to secondary and tertiary consumers—typically carnivores that hunt and feed on herbivores and other predators. At the top of this chain are apex predators, powerful organisms with no natural enemies, playing a vital role in maintaining the balance of ecosystems

Table of Contents

EXAMPLES OF FOOD CHAIN

The following are examples of a food chain;

i. Sun → Grasses (Producer) → Grasshoppers (Primary Consumer) → Frogs
(Secondary Consumer) → Snakes (Tertiary Consumer) → Owl (Quaternary
Consumer): In a grassland ecosystem, the primary producers are grasses. They capture sunlight through photosynthesis, converting it into chemical energy. Grasshoppers, as primary consumers, graze on the grass, obtaining energy from the plants.

In a typical grassland ecosystem, herbivores such as grasshoppers feed on plant material, serving as primary consumers. Frogs act as secondary consumers, feeding on grasshoppers and absorbing the stored plant energy. Snakes, as tertiary consumers, prey on frogs, continuing the energy transfer up the food chain.

At the top, owls function as quaternary consumers, hunting snakes and completing the energy flow within the ecosystem. This structured sequence of feeding relationships highlights how energy moves through each trophic level, sustaining life in the grassland environment.

ii. Trees → Caterpillar → Yellow-billed Shrike → Kestrels: In a forest ecosystem, trees are the primary producers, converting sunlight into energy through photosynthesis. Caterpillars act as primary consumers by feeding on the leaves of trees, utilizing the energy stored in the plant tissues.

In the forest food chain, energy is passed through various trophic levels. Birds like the Yellow-billed Shrike (Corvinella corvina) act as secondary consumers, feeding on energy-rich caterpillars. Kestrels (Falco tinnunculus), as tertiary consumers, occupy a higher position in the food web by preying on the Yellow-billed Shrike. This flow of energy—from trees (producers) to caterpillars (primary consumers), then to birds and finally to predatory birds like kestrels—illustrates how energy is transferred in a forest ecosystem.

iv. Algae → Daphnia (Water Flea) → Small Fish → Heron: In a wetland ecosystem like the ITU wetlands, algae are the primary producers, harnessing energy from sunlight through photosynthesis. Daphnia, or water fleas, as primary consumers, consume the algae, obtaining energy from the plant matter.

Small fish such as the Banded Tilapia (Tilapia zillii) serve as secondary consumers in aquatic ecosystems, feeding on primary consumers like Daphnia. These energy-rich organisms pass on the nutrients they acquired from algae to the fish. Tertiary consumers, like the Grey Heron (Ardea cinerea), then prey on the small fish, completing the food chain in a pond ecosystem.

This step-by-step energy transfer in aquatic ecosystems—from algae (primary producers) to Daphnia (primary consumers), then to Tilapia, and finally to herons—demonstrates how energy flows through various trophic levels. The continuous flow of energy in the ecosystem supports the survival, growth, and reproduction of all organisms involved, ensuring the stability and balance of the ecosystem.

CRITICAL ASPECTS OF FOOD CHAINS

(a) Energy Loss in Ecosystems: One of the major factors affecting energy transfer efficiency in ecosystems is energy loss. At each trophic level, a large portion of energy is lost as heat during metabolic processes such as respiration and digestion, as well as through waste. This energy loss reduces the amount of energy available to organisms at higher trophic levels. For example, when a grasshopper (a primary consumer) feeds on plant material, it undergoes metabolic activities to extract energy. However, a significant portion of that energy is lost as heat, highlighting the inefficiency of energy transfer in food chains.

A significant portion of energy in ecosystems is lost as heat during biological processes, and only a small fraction is utilised by organisms like the grasshopper for growth, movement, and reproduction. As energy flows through trophic levels, additional losses occur due to waste production. For instance, when a grasshopper excretes, it releases energy-rich waste materials that were not absorbed or used by its body. These organic waste products still contain usable energy, which could have supported organisms at higher trophic levels in the food chain.

(b) Trophic Efficiency: Trophic efficiency refers to the percentage of energy transferred between trophic levels in a food chain. On average, only about 10% of energy is passed on to the next trophic level, while approximately 90% is lost. This energy loss occurs due to various metabolic processes such as respiration, digestion, movement, and heat production. Understanding trophic efficiency is essential in ecosystem energy flow studies, as it highlights the limits of energy transfer and the sustainability of different trophic levels in ecosystems.

(c) Biomagnification in Food Chains: Biomagnification occurs in certain food chains when toxins or pollutants accumulate at higher trophic levels. As organisms at higher trophic levels consume a larger quantity of organisms from lower levels, any toxins present in those organisms become increasingly concentrated. This process can pose significant risks to higher-level consumers, disrupting the balance of the ecosystem. Understanding biomagnification is essential for comprehending the impact of pollution on ecosystem health and species survival.

Food Web: A food web is a complex network of interconnected food chains within an ecosystem, illustrating the multiple feeding relationships among organisms. Unlike a simple food chain, which only shows linear energy flow, the food web provides a more accurate and realistic representation of energy transfer by accounting for the fact that organisms can have various feeding relationships. This interconnectedness highlights how organisms may consume multiple types of prey, offering a more comprehensive view of energy flow in ecosystems. The food web is a critical concept, as it offers a broader and more intricate understanding of ecosystem dynamics than the food chain alone.

EXAMPLES OF FOOD WEB

In a food web, multiple food chains overlap and form a complex web-like structure. This reflects the reality that most organisms have multiple food sources and can occupy different trophic levels simultaneously. Here are examples of a food web:

(i.) Grassland Food Web: In a typical grassland ecosystem, energy flows through a complex network of feeding relationships. Herbivores such as the grasshopper and rabbit feed directly on grass, serving as primary consumers. The frog, a secondary consumer, preys on grasshoppers and other small insects. Moving up the trophic levels, the snake consumes frogs or small mammals like mice, while the fox, a top predator, feeds on rabbits, mice, or other small animals. Each step in this grassland food web illustrates the direction of energy flow, with arrows indicating how energy is transferred from one organism to another.

(ii.) Ocean Food Web: The ocean food web is a highly intricate network of feeding relationships and energy transfer among marine organisms. At the base of this marine ecosystem are phytoplankton and algae, which act as primary producers. Through the process of photosynthesis, these microscopic plants convert sunlight into energy-rich compounds, forming the essential foundation of the marine food chain. Their role is critical in sustaining life in the oceans and supporting biodiversity across multiple trophic levels.

Primary consumers in the ocean ecosystem, such as small fish and zooplankton, feed on energy-rich phytoplankton, gaining essential nutrients to support their survival. Secondary consumers—including predatory fish, squids, and marine mammals—rely on these smaller organisms to fulfill their energy requirements. At the top of the trophic levels, tertiary consumers like sharks and orcas prey on the secondary consumers, maintaining balance in the marine food web.

Decomposers, such as bacteria and other microorganisms, play a vital role by breaking down dead organisms and recycling nutrients back into the ecosystem. In every marine food web, the arrows represent the flow of energy, clearly illustrating how energy is transferred from one organism to another across different levels of the aquatic ecosystem.

CRITICAL ASPECTS OF THE FOOD WEB IN THE ECOSYSTEM

(a.) Energy Pathways in Ecosystems: Food webs illustrate the complex and interconnected energy transfer pathways within an ecosystem. Because organisms at various trophic levels are interdependent, energy flow can occur through multiple routes, contributing to ecosystem stability and resilience. If one energy pathway is disrupted, such as a drop in the population of a specific prey species, predators can adapt by feeding on alternative prey. This flexibility in the food web structure helps maintain ecological balance and prevents cascading effects that could destabilise the entire ecosystem.

However, because organisms at various trophic levels are closely interconnected, alternative energy sources in the ecosystem help maintain ecological balance. In a wetland ecosystem, when the population of small fish declines, wading birds like herons and egrets can adapt by feeding on other available prey such as frogs, crayfish, or larger aquatic insects. This flexibility in feeding behaviour allows these birds to continue obtaining the energy needed for survival while also helping to prevent disruptions in the energy flow and maintaining the overall stability of the ecosystem.

Keystone Species: This can be defined as a species that plays a crucial role in maintaining the balance and stability of an ecosystem. The term “Keystone” is derived from architecture and refers to the central, wedge-shaped stone placed at the top of an arch that locks all the other stones in place. It is called the keystone because it plays a crucial role in maintaining the structural integrity and stability of the arch.

Keystone species play a critical role in maintaining ecosystem balance, even though they may not be the largest or most abundant organisms. Their removal can cause dramatic changes to the structure and function of entire ecosystems. For instance, in wetland ecosystems such as the Itu Wetlands in Nigeria, the loss of a single keystone species can disrupt food chains, water regulation, and biodiversity stability, highlighting their ecological importance.

Crocodiles in West Africa, including the West African slender-snouted crocodile (Mecistops cataphractus), West African crocodile (Crocodylus suchus), and West African dwarf crocodile (Osteolaemus tetraspis), are considered keystone species. As top predators in their ecosystems, these crocodiles play a crucial role in maintaining ecological balance by…

(i.) Habitat Engineering: Crocodiles modify their habitat by creating nests and burrows along the water’s edge. These structures provide nesting sites for other reptiles and birds, contributing to the overall biodiversity of the wetland.

(ii.) Population Control: Crocodiles help in controlling the populations of prey species, such as fish, amphibians, reptiles, and small mammals. By preying on these species, they help prevent their overpopulation, maintaining a balance in the ecosystem.

(iii.) Influencing Behaviour: The presence of crocodiles in wetlands affects the behaviour and distribution of other species. This can lead to changes in feeding patterns, habitat selection, and overall community dynamics.

(iv.) Carcass Recycling: Crocodiles scavenge and consume carcasses, playing an important role in nutrient recycling. By consuming dead animals, they prevent the accumulation of decaying matter, which could lead to negative impacts on water quality and other organisms in the ecosystem.

C. Energy Pyramids in Ecosystems
Energy pyramids are graphical representations that illustrate the flow of energy across various trophic levels within a food chain or food web in an ecosystem. Shaped like a pyramid, they feature a broad base and a narrow apex, reflecting the decreasing energy available at higher levels. At the base of the energy pyramid are the primary producers—such as plants and algae—which convert solar energy into chemical energy through photosynthesis.

As we move up the energy pyramid in an ecosystem, the second level is made up of primary consumers—herbivorous animals such as rabbits, deer, and various insects that feed directly on plants (primary producers) to obtain energy. Above them are the secondary consumers, which include carnivores and omnivores that prey on herbivores. The energy pyramid continues through additional trophic levels, with each level consisting of organisms that derive energy by consuming those below them.

As energy flows through an ecosystem, both the number of organisms and the available energy decrease at each successive level of the energy pyramid. At the top of this pyramid are apex predators—organisms that occupy the highest trophic level. These top predators play a vital role in ecosystem stability and typically have few or no natural enemies.

Conclusion

Energy transfer in ecosystems occurs through interconnected food chains and food webs, forming a complex system of ecological relationships. By exploring key concepts like energy loss, trophic efficiency, biomagnification, energy pathways, keystone species, and energy pyramids, we gain deeper insight into how energy moves from one organism to another.

This understanding helps us recognize the ecological interdependence that maintains ecosystem stability, identify the roles of critical species like keystone predators, and emphasise the need to preserve natural habitats, protect biodiversity, and reduce human impact on ecological balance.

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