17.2 Energy Flow in Ecosystems
4 min read•august 7, 2024
Energy flow in ecosystems is all about how organisms get and use energy. It starts with like making food from sunlight, then moves up through consumers eating each other. Each step loses some energy, shaping how ecosystems work.
Food chains show this energy flow simply, while food webs show it more realistically. Energy pyramids and help us see how much energy and living stuff is at each level. This helps explain why there are fewer top predators than plants in nature.
Food Chains and Food Webs
Trophic Relationships in Ecosystems
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- Food chains depict the linear flow of energy from producers to consumers in an ecosystem
- Consist of producers (plants) at the base, followed by (), (), and (top predators)
- Energy is transferred from one trophic level to the next, with some energy lost as heat at each level (approximately 10% of energy is transferred)
- Food webs illustrate the complex network of feeding relationships within an ecosystem
- Include multiple interconnected food chains
- Demonstrate how species can occupy multiple trophic levels and have various food sources (omnivores consume both plants and animals)
- Trophic levels represent the position of an organism in the or web
- Producers (autotrophs) make up the first trophic level, converting sunlight into chemical energy through (plants, algae, cyanobacteria)
- Consumers (heterotrophs) occupy higher trophic levels, obtaining energy by consuming other organisms
- Primary consumers (herbivores) feed on producers (rabbits, caterpillars, zooplankton)
- Secondary consumers (carnivores) eat primary consumers (birds, spiders, small fish)
- Tertiary consumers (top predators) consume secondary consumers (hawks, wolves, sharks)
- Decomposers break down dead organisms and waste products, releasing nutrients back into the ecosystem (bacteria, fungi)
Ecological Roles of Organisms
- Producers, also known as autotrophs, are organisms that convert inorganic compounds into organic compounds using energy from the sun (photosynthesis) or chemical reactions (chemosynthesis)
- Photosynthetic producers include plants, algae, and cyanobacteria
- Chemosynthetic producers, such as certain bacteria, use chemical energy to produce organic compounds in extreme environments (deep-sea hydrothermal vents)
- Consumers, or heterotrophs, obtain energy and nutrients by feeding on other organisms
- Primary consumers (herbivores) feed exclusively on producers (plants)
- Secondary consumers (carnivores) eat primary consumers
- Tertiary consumers (top predators) consume secondary consumers
- Omnivores feed on both producers and consumers (humans, bears, crows)
- Decomposers, including bacteria and fungi, break down dead organisms and waste products
- Recycle nutrients back into the ecosystem, making them available for producers
- Play a crucial role in maintaining the flow of energy and matter within ecosystems
Energy Flow and Biomass
Energy Pyramids and Trophic Levels
- Energy pyramids represent the flow of energy through trophic levels in an ecosystem
- The base of the pyramid represents producers, with each successive level representing consumers
- The width of each level indicates the amount of energy available at that trophic level
- Energy is lost as heat at each trophic transfer (approximately 10% efficiency), resulting in a narrowing of the pyramid
- Biomass refers to the total mass of living organisms in a given area or ecosystem
- Biomass pyramids depict the amount of biomass at each trophic level
- Producers typically have the highest biomass, followed by primary consumers, secondary consumers, and tertiary consumers
- Biomass pyramids can be inverted in some aquatic ecosystems where producers (phytoplankton) have a rapid turnover rate and support a larger biomass of consumers
Ecological Efficiency and Energy Transfer
- Ecological efficiency is the percentage of energy transferred from one trophic level to the next
- Typically, about 10% of the energy is transferred, while 90% is lost as heat, used for metabolic processes, or undigested
- This low efficiency limits the number of trophic levels in an ecosystem (usually 4-5)
- Ecosystems with higher ecological efficiencies can support more trophic levels and a greater abundance of organisms
- Energy transfer between trophic levels is inefficient due to several factors
- Heat loss during metabolic processes
- Undigested material in waste products
- Energy used for growth, reproduction, and other life functions
- Incomplete consumption of organisms by predators
Bioaccumulation
Accumulation of Toxins in Food Chains
- Bioaccumulation is the gradual buildup of toxic substances, such as heavy metals or persistent organic pollutants, in an organism's tissues over time
- Occurs when the rate of intake exceeds the rate of excretion or metabolic breakdown
- Toxins are often stored in fatty tissues and can persist for long periods
- Bioaccumulation can be amplified through food chains, a process called biomagnification
- Toxins are transferred from producers to consumers, with concentrations increasing at each trophic level
- Top predators, such as birds of prey or large fish, tend to have the highest levels of accumulated toxins
- Bioaccumulation and biomagnification can have detrimental effects on organisms and ecosystems
- High levels of toxins can cause health problems, reduced fertility, and increased mortality rates
- Persistent organic pollutants (POPs) and heavy metals (mercury, lead) are common bioaccumulative substances
- DDT, a pesticide, is a well-known example of a POP that bioaccumulated in birds of prey, causing eggshell thinning and population declines
Key Terms to Review (23)
10% rule: The 10% rule refers to the principle in ecology that, on average, only about 10% of the energy from one trophic level is transferred to the next level in a food chain or food web. This energy transfer is significant because it highlights the inefficiencies of energy movement through an ecosystem and helps explain why there are fewer organisms at higher trophic levels compared to lower ones.
Biomass: Biomass refers to the total mass of living matter within a specific area or volume, often measured in terms of dry weight. This term is crucial for understanding the distribution of energy and matter within ecosystems, highlighting the relationship between different levels of organization, such as populations and communities, as well as energy flow and transfer in food webs. The concept of biomass plays a vital role in ecological studies, especially when examining productivity and the efficiency of energy use among organisms.
Carnivores: Carnivores are organisms that primarily consume other animals for their nutritional needs. They play a critical role in ecosystems by controlling prey populations and contributing to energy flow within food webs. As secondary or tertiary consumers, carnivores obtain energy by preying on herbivores or other carnivores, highlighting their importance in maintaining the balance of various ecological communities.
Cellular Respiration: Cellular respiration is a biochemical process through which cells convert glucose and oxygen into energy, carbon dioxide, and water. This process is essential for generating ATP, the energy currency of the cell, and it plays a crucial role in maintaining cellular functions and supporting life.
Competition: Competition is the interaction between organisms or species that vie for limited resources such as food, space, and mates. This rivalry can drive natural selection and influence population dynamics, ultimately shaping community structures and ecological interactions.
Energy loss: Energy loss refers to the decrease in energy as it moves through an ecosystem, primarily due to the laws of thermodynamics and metabolic processes. As energy flows from producers to consumers, a significant portion is lost at each trophic level, mainly as heat due to respiration and other biological functions. This concept highlights the inefficiency of energy transfer within food webs and emphasizes the need for a continuous input of energy from the sun to sustain ecosystems.
Energy pyramid: An energy pyramid is a graphical representation that illustrates the flow of energy through different trophic levels in an ecosystem, showcasing how energy decreases as it moves from producers to top predators. This concept highlights the inefficiency of energy transfer, with only about 10% of the energy at one level being passed to the next, emphasizing the importance of producers in sustaining the ecosystem.
Food chain: A food chain is a linear sequence of organisms where each organism serves as food for the next in the chain, illustrating how energy and nutrients flow through an ecosystem. This concept helps to highlight the relationships between producers, consumers, and decomposers, demonstrating how energy from the sun is converted into food and then passed along through various trophic levels.
Food web: A food web is a complex network of interconnected food chains that illustrates how energy and nutrients flow through an ecosystem. It highlights the feeding relationships among various organisms, showing how they are linked together through different levels of consumption, from producers to primary consumers, secondary consumers, and beyond. By mapping these interactions, food webs provide insight into ecosystem dynamics and stability.
G. Evelyn Hutchinson: G. Evelyn Hutchinson was a prominent ecologist known for his pioneering work in the field of ecology, particularly concerning energy flow in ecosystems. He is often referred to as the 'father of modern ecology' due to his significant contributions to understanding ecological relationships and the concept of niche differentiation, which illustrates how different species coexist and utilize resources in their environments.
Herbivores: Herbivores are organisms that primarily consume plants and plant-based materials as their main source of energy and nutrients. These animals play a vital role in ecosystems as they help in the transfer of energy from producers, like plants, to higher trophic levels in the food web. By feeding on plants, herbivores not only contribute to energy flow but also influence plant population dynamics and ecosystem structure.
Kinetic Energy: Kinetic energy is the energy an object possesses due to its motion. This energy is dependent on both the mass of the object and its velocity, following the formula $$KE = \frac{1}{2}mv^2$$, where 'm' is mass and 'v' is velocity. In biological systems, kinetic energy plays a crucial role in processes such as ATP production and energy transfer within ecosystems, demonstrating how movement at the molecular level fuels life and contributes to ecological interactions.
Lindeman's Trophic Dynamic: Lindeman's Trophic Dynamic is a concept that describes the flow of energy through an ecosystem and how it is transferred between different levels of the food web. It emphasizes the relationships among producers, consumers, and decomposers, highlighting how energy diminishes at each trophic level due to metabolic processes and inefficiencies. This framework helps explain ecosystem structure and function by illustrating how energy is acquired, utilized, and lost in ecological interactions.
Photosynthesis: Photosynthesis is the biological process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. This process not only produces the organic compounds that serve as food for these organisms but also releases oxygen as a byproduct, which is crucial for the survival of aerobic organisms.
Plants: Plants are multicellular organisms that belong to the kingdom Plantae and are characterized by their ability to perform photosynthesis, using sunlight to convert carbon dioxide and water into glucose and oxygen. They play a vital role in ecosystems as primary producers, forming the base of food chains and contributing to the energy flow in ecosystems.
Potential Energy: Potential energy is the stored energy in an object due to its position or arrangement. It plays a crucial role in energy transformations, indicating the potential for doing work based on an object's state. In biological systems, this energy can be harnessed through biochemical processes and ecological interactions, influencing both cellular functions and ecosystem dynamics.
Predation: Predation is the biological interaction where one organism, the predator, hunts and consumes another organism, the prey, for nourishment. This relationship is crucial for regulating populations within ecosystems, influencing the structure of communities, and driving evolutionary adaptations among species.
Primary consumers: Primary consumers are organisms that feed directly on producers, primarily plants and algae, forming the second trophic level in an ecosystem. They play a crucial role in energy flow, as they convert the energy stored in producers into forms that can be used by higher trophic levels, such as secondary consumers. By consuming producers, primary consumers help maintain the balance within ecosystems and are essential for the transfer of energy through food webs.
Producers: Producers are organisms that can make their own food through processes like photosynthesis or chemosynthesis, forming the foundation of the food web in ecosystems. They convert sunlight or chemical energy into organic compounds, which serve as the primary energy source for all other organisms in an ecosystem, linking together levels of ecological organization, nutrient cycles, and energy flow.
Secondary consumers: Secondary consumers are organisms that primarily eat primary consumers, which are herbivores that feed on plants. These organisms play a crucial role in the food chain and energy flow within ecosystems, helping to maintain the balance of populations and transferring energy from lower trophic levels to higher ones. By consuming primary consumers, secondary consumers facilitate nutrient cycling and energy distribution throughout the ecosystem.
Symbiosis: Symbiosis is a biological term that describes the interaction between two different organisms living in close physical proximity, often for an extended period. This relationship can be mutualistic, commensalistic, or parasitic, and it plays a critical role in shaping ecosystems, influencing everything from nutrient cycling to population dynamics.
Tertiary consumers: Tertiary consumers are organisms that occupy the top tier of the food chain, primarily consuming secondary consumers. These animals are typically carnivorous and play a crucial role in maintaining the balance of ecosystems by regulating the populations of species they prey upon. Their position reflects an important aspect of energy flow within ecosystems, as they represent one of the final stages in the transfer of energy from primary producers through various trophic levels.
Trophic efficiency: Trophic efficiency is the percentage of energy that is transferred from one trophic level to the next in an ecosystem. This concept helps explain how energy diminishes as it moves up the food chain, influencing the structure and dynamics of ecosystems. Understanding trophic efficiency is crucial for studying energy flow and the limitations on the number of trophic levels that can exist within a given ecosystem.