Lecture 18 Study Guide: Ecology - End of Test 3 Material PDF

Ecosystem ecology is a branch of ecology that focuses on studying the interactions between organisms and their environment within a specific area or ecosystem. It aims to understand the flow of energy and materials through ecosystems, as well as the relationships and dynamics between the living (bio...

Ecosystem ecology is a branch of ecology that focuses on studying the interactions between organisms and their environment within a specific area or ecosystem. It aims to understand the flow of energy and materials through ecosystems, as well as the relationships and dynamics between the living (biotic) and non-living (abiotic) components. 1. **Energetics**: Energetics in ecosystem ecology refers to the study of energy flow within ecosystems. Energy is a fundamental aspect of ecosystems, as it drives all biological processes. In ecosystems, energy enters from the sun in the form of sunlight and is converted into chemical energy through photosynthesis by autotrophic organisms such as plants, algae, and some bacteria. This chemical energy is then passed on through the ecosystem's food web as organisms consume each other. - **Example**: In a terrestrial ecosystem, such as a forest, sunlight is absorbed by plants through photosynthesis. The energy stored in plant tissues is then transferred to herbivores when they eat the plants. In turn, carnivores obtain energy by consuming herbivores. This transfer of energy continues through the food chain until it eventually dissipates as heat. 1 2. **Energy Flow**: Energy flow refers to the movement of energy through an ecosystem. It involves the transfer of energy from one organism to another as they interact within the ecosystem. The flow of energy is unidirectional and follows a hierarchical structure, known as a trophic pyramid, where energy is lost at each trophic level. - **Example**: In a marine ecosystem, phytoplankton (primary producers) convert sunlight into chemical energy through photosynthesis. Zooplankton (primary consumers) feed on phytoplankton, transferring energy from one trophic level to the next. Small fish then consume zooplankton, followed by larger fish that consume smaller fish. At each trophic level, energy is lost through metabolic processes, heat production, and waste, resulting in a decrease in available energy as you move up the food chain. 3. **Energy Budgets**: Ecosystem energetics involves quantifying and understanding the energy budgets within ecosystems. Energy budgets represent the balance between energy inputs (such as sunlight) and outputs (such as respiration and heat loss) within an ecosystem. By studying energy budgets, ecologists can gain insights into the overall functioning and productivity of ecosystems. - **Example**: Ecologists studying a lake ecosystem might measure the amount of sunlight that penetrates the water surface and estimate the primary productivity of aquatic plants through photosynthesis. They would also measure the energy expended by organisms through respiration and metabolic processes. By comparing energy inputs with outputs, they can determine the overall energy balance of the ecosystem and understand its productivity. Understanding ecosystem energetics and energy flow is crucial for predicting the consequences of environmental disturbances, such as climate change or habitat destruction, on ecosystem dynamics and functioning. It also provides insights into the structure and functioning of ecosystems, helping to inform conservation and management strategies. 1 The methods used to estimate ecosystem production, both terrestrial and aquatic, are crucial for understanding the functioning and productivity of ecosystems. Here's an explanation of the methods and concepts mentioned: 1. **Light Bottle Method for Primary Producers**: - This method involves placing water samples containing primary producers (such as phytoplankton in aquatic ecosystems or plants in terrestrial ecosystems) in clear bottles. - One set of bottles is exposed to light (light bottles), while another set is kept in darkness (dark bottles). - Primary producers in the light bottles perform photosynthesis, converting light energy into chemical energy (organic matter), which can be measured. - In the dark bottles, primary producers respire but do not photosynthesize since they lack light. This respiration rate can also be measured. - The difference between the production measured in the light bottles and respiration measured in the dark bottles gives an estimate of net primary production (NPP), or more accurately, net ecosystem production (NEP) in some cases. 2. **Net Ecosystem Production (NEP)**: 2 - NEP represents the net carbon gain or loss in an ecosystem over a specific period. - It takes into account both primary production (photosynthesis) and ecosystem respiration (the sum of all living organisms' respiration in the ecosystem). - NEP can be positive (net carbon uptake, indicating the ecosystem is a carbon sink) or negative (net carbon release, indicating the ecosystem is a carbon source). 3. **Global Production in Ecosystems: Terrestrial**: - This refers to the total primary production occurring in terrestrial ecosystems worldwide. - It is estimated using a combination of methods such as satellite remote sensing, ground-based measurements of vegetation, and ecosystem modeling. - Satellite data can provide information on vegetation cover, density, and productivity over large spatial scales, while ground-based measurements and models help validate and refine these estimates. 4. **Global Production in Ecosystems: Aquatic**: - Similar to terrestrial ecosystems, global production in aquatic ecosystems refers to the total primary production occurring in lakes, rivers, oceans, and other aquatic environments. - Methods for estimating aquatic production include remote sensing techniques to measure chlorophyll concentrations (indicative of phytoplankton biomass), as well as in situ measurements of primary productivity and carbon uptake rates. 5. **Dynamic Nature of Ecosystem Production**: - Ecosystem production varies spatially and temporally due to factors such as climate, nutrient availability, and disturbance events. - Understanding these variations is essential for assessing ecosystem health, predicting responses to environmental changes, and managing natural resources sustainably. The provided animation, "The Heartbeat of Nature's Productivity," likely visualizes the dynamic nature of ecosystem productivity, showing how it fluctuates over time and space in response to environmental factors. This dynamic nature underscores the importance of continuous monitoring and research to understand and conserve ecosystems effectively. 2 3 4 5 6 Certainly! Understanding the factors that control aquatic and terrestrial production is crucial for comprehending ecosystem dynamics and productivity. Here's an in-depth explanation along with examples: **Controls on Aquatic Production:** 1. **Light Availability**: Light is a primary limiting factor for photosynthesis in aquatic ecosystems. Depths at which sufficient light penetrates water can vary depending on factors such as water clarity, turbidity, and the presence of shading organisms (e.g., aquatic plants). - *Example*: In clear, shallow waters, such as coral reefs or coastal areas, primary production can be high due to ample light penetration, supporting diverse communities of algae and other primary producers. 2. **Nutrient Availability**: Nutrients like nitrogen and phosphorus are essential for plant growth and primary production in aquatic ecosystems. Limiting nutrient availability can restrict photosynthetic activity and overall productivity. 7 - *Example*: In nutrient-rich environments like estuaries or areas affected by agricultural runoff, excessive nutrient inputs can lead to eutrophication, causing algal blooms and oxygen depletion, which can negatively impact aquatic life. 3. **Temperature**: Temperature influences metabolic rates and biochemical processes in aquatic organisms. Optimal temperatures vary among species, and extremes can limit productivity. - *Example*: In polar regions, where water temperatures remain near freezing, primary production is limited compared to warmer, temperate regions with more favorable temperatures. 4. **Water Flow and Mixing**: Water flow, currents, and mixing affect nutrient availability and light penetration in aquatic ecosystems. Areas with limited water flow may experience nutrient buildup or stratification, impacting productivity. - *Example*: Upwelling zones in oceans bring nutrient-rich waters to the surface, enhancing primary production and supporting thriving marine ecosystems. **Controls on Terrestrial Production:** 1. **Temperature and Climate**: Temperature influences metabolic rates, plant growth, and nutrient cycling in terrestrial ecosystems. Climatic factors such as temperature, precipitation, and seasonality determine the types of vegetation and overall productivity. - *Example*: Tropical rainforests experience high productivity due to warm temperatures, abundant sunlight, and consistent rainfall, supporting diverse plant and animal life. 2. **Water Availability**: Water availability is critical for plant growth and productivity in terrestrial ecosystems. Water availability varies with factors like rainfall patterns, soil moisture, and hydrological processes. - *Example*: Arid and semi-arid regions, such as deserts, have low productivity due to limited water availability, resulting in sparse vegetation adapted to drought conditions. 3. **Soil Fertility**: Soil nutrients influence plant growth and productivity in terrestrial ecosystems. Factors like soil pH, organic matter content, and nutrient cycling processes determine soil fertility. 7 - *Example*: Fertile soils in temperate grasslands support high productivity, sustaining dense vegetation and grazing animals. 4. **Disturbances**: Natural disturbances like fire, floods, and storms, as well as human activities such as logging and agriculture, can influence terrestrial productivity by altering vegetation composition and nutrient cycling. - *Example*: Forest fires play a vital role in nutrient recycling and ecosystem regeneration in fire-adapted ecosystems like certain types of temperate forests. **Question:** Feel free to ask any specific questions you may have about the controls on aquatic and terrestrial production, and I'll be glad to provide further clarification or examples! 7 The concept illustrated in the scenario of increasing net primary productivity (NPP) followed by reaching a climax and subsequent decrease is related to temporal variation in ecosystem energetics, specifically the "Year-to-year variability" aspect. 1. **Temporal Variation in Ecosystem Energetics**: Ecosystem energetics refers to the flow and transformation of energy within ecosystems over time. Temporal variation in ecosystem energetics examines how energy flow and productivity change over different time scales, such as seasons, years, or the age of an ecosystem. 2. **Year-to-Year Variability (Stochasticity)**: Year-to-year variability, also known as stochasticity, refers to the random fluctuations or unpredictability in ecosystem processes and productivity from one year to the next. These fluctuations can be influenced by various factors such as climate variability, weather events, disturbance events (e.g., fires, storms), and interactions within the ecosystem. - *Example*: In the scenario described, the decadal NPP (net primary productivity over a decade) increases initially, indicating a period of increasing productivity. This 8 could be due to favorable environmental conditions, such as optimal temperature, precipitation, and nutrient availability. However, after reaching a climax, the NPP starts to decrease. This decline could be attributed to factors like resource limitation, competition among species, or changes in environmental conditions such as drought or nutrient depletion. The fluctuations in NPP from year to year reflect the stochastic nature of ecosystem dynamics, where unpredictable events or interactions influence productivity over time. 3. **Seasonal Variation**: Seasonal variation in ecosystem energetics refers to the recurring patterns of energy flow and productivity within ecosystems over the course of a year. Seasonal changes in temperature, precipitation, and daylight hours influence processes such as photosynthesis, growth, and reproduction in plants and other organisms. 4. **Age of Ecosystem**: The age of an ecosystem can also influence its energetics and productivity. Newly established ecosystems may undergo rapid growth and succession, leading to changes in productivity over time. As ecosystems mature and reach a climax stage, productivity may stabilize or decline due to factors such as nutrient cycling, species interactions, and environmental constraints. In summary, the scenario of increasing NPP followed by a climax and subsequent decrease illustrates year-to-year variability or stochasticity in ecosystem energetics, where random fluctuations and unpredictable events influence productivity over time. This highlights the dynamic nature of ecosystems and the importance of considering temporal variation in understanding their functioning and dynamics. 8 Without the specific graphs provided, I can't directly interpret the relationship between hay yield and temperature. However, I can explain how temperature might affect hay yield and what different relationships might indicate: 1. **Positive Relationship**: - If there's a positive relationship between hay yield and temperature, it means that as temperature increases, hay yield also increases. This relationship suggests that warmer temperatures are beneficial for hay growth and production. - Possible explanations for a positive relationship could include increased photosynthesis rates, extended growing seasons, and improved nutrient availability associated with higher temperatures. 2. **Negative Relationship**: - Conversely, if there's a negative relationship between hay yield and temperature, it means that as temperature increases, hay yield decreases. This relationship suggests that warmer temperatures have a detrimental effect on hay growth and production. - Possible explanations for a negative relationship could include heat stress on plants, increased evapotranspiration leading to water stress, and enhanced susceptibility to pests and diseases associated with higher temperatures. 9 3. **Neutral Relationship**: - A neutral relationship between hay yield and temperature would imply that changes in temperature do not significantly affect hay yield. In this case, hay yield remains relatively stable regardless of variations in temperature. - Possible explanations for a neutral relationship could include temperature ranges within which hay growth is optimal, buffering effects of other environmental factors, or compensatory mechanisms within the ecosystem. To determine the specific relationship between hay yield and temperature, it's necessary to examine the data presented in the graphs. Factors such as the range of temperatures studied, the timeframe over which data is collected, and the presence of other environmental variables can all influence the observed relationship. Additionally, it's important to consider potential non-linear or threshold effects, where the relationship between hay yield and temperature may change at extreme temperature ranges. 9 In ecosystems, the terms "allochthonous carbon" and "autochthonous carbon" refer to sources of organic carbon that differ in their origin and entry into the food web: 1. **Allochthonous Carbon (External)**: - Allochthonous carbon refers to organic carbon inputs that originate from outside the ecosystem or from sources external to the local food web. - These external sources can include organic matter that is imported into the ecosystem from adjacent habitats, such as leaf litter, woody debris, or animal carcasses that are washed into streams or rivers from surrounding forests. - Allochthonous carbon inputs often play a crucial role in supporting food webs, particularly in ecosystems where primary production is limited or where certain consumer species rely heavily on external organic inputs. 2. **Autochthonous Carbon (Internal)**: - Autochthonous carbon refers to organic carbon that is produced within the ecosystem by primary producers (e.g., plants, algae) through photosynthesis. - This internal carbon production forms the basis of the local food web, as it provides energy and nutrients for primary consumers (herbivores) and subsequently higher trophic levels (carnivores, omnivores). 10 - Autochthonous carbon is generated from the fixation of carbon dioxide (CO2) during photosynthesis, primarily driven by sunlight and nutrient availability within the ecosystem. **Examples**: - **Allochthonous Carbon**: In a freshwater ecosystem like a river or stream, fallen leaves from surrounding trees can serve as allochthonous carbon inputs. These leaves are broken down by microbes and detritivores (organisms that feed on decaying organic matter), providing energy and nutrients to the aquatic food web. Many aquatic insects and fish rely on this external carbon source for their energy needs. - **Autochthonous Carbon**: In a marine ecosystem such as a coral reef, coral polyps and algae are primary producers that synthesize autochthonous carbon through photosynthesis. This autochthonous carbon supports a diverse array of organisms within the reef ecosystem, including herbivorous fish, predatory fish, and other invertebrates. Understanding the balance between allochthonous and autochthonous carbon inputs is crucial for comprehending the functioning and dynamics of ecosystems, particularly in aquatic habitats where external organic subsidies can play a significant role in supporting food webs. It also highlights the interconnectedness of different ecosystems and the importance of considering external inputs in ecosystem management and conservation efforts. 10 The terms "primary production" and "secondary production" are fundamental concepts in ecology, describing different aspects of energy flow and biomass accumulation within ecosystems: 1. **Primary Production**: - Primary production refers to the synthesis of organic matter by autotrophic organisms, primarily through photosynthesis. - Autotrophs, such as plants, algae, and some bacteria, capture energy from sunlight and convert inorganic substances (such as carbon dioxide and water) into organic compounds (such as sugars and carbohydrates). - Primary production forms the base of the food web, providing energy and nutrients for all other organisms within the ecosystem. - The rate of primary production is typically measured in terms of biomass or energy produced per unit area per unit time (e.g., grams of organic matter per square meter per year). 2. **Secondary Production**: - Secondary production refers to the formation of biomass by heterotrophic organisms, which obtain energy by consuming organic matter produced by 11 autotrophs. - Heterotrophs include animals, fungi, and many bacteria that cannot produce their own food and rely on consuming other organisms for energy. - Secondary production represents the energy assimilated by heterotrophs through feeding and growth, minus the energy lost through respiration and excretion. - The rate of secondary production is often measured as the increase in biomass of consumers (e.g., herbivores, carnivores) over a given period. **Example**: - In a terrestrial ecosystem, grasses and other plants are primary producers that convert sunlight into organic matter through photosynthesis. Grazing herbivores, such as rabbits or deer, consume these plants, assimilating the energy and nutrients stored in plant tissues. The growth and reproduction of these herbivores represent secondary production. If a carnivore, such as a fox or a hawk, preys on these herbivores, the energy assimilated by the carnivore for growth and reproduction would constitute another level of secondary production. Understanding primary and secondary production is essential for studying energy flow and trophic dynamics within ecosystems. It helps ecologists assess the productivity and sustainability of ecosystems, as well as understand the role of different organisms in nutrient cycling and ecosystem functioning. 11 Certainly! Secondary production, food web energy flows, and efficiency are key concepts in ecology that help us understand how energy is transferred and utilized within ecosystems. Assimilation efficiency and production efficiency are two important metrics used to quantify these processes: 1. **Secondary Production**: - Secondary production refers to the generation of biomass by heterotrophic organisms within an ecosystem. This includes animals, fungi, and certain bacteria that obtain energy by consuming organic matter produced by autotrophs. - Secondary production represents the energy assimilated by heterotrophs through feeding and growth, minus the energy lost through respiration and excretion. - It is an essential component of ecosystem dynamics as it drives the flow of energy through food webs and supports higher trophic levels. 2. **Food Web Energy Flows**: - Food webs depict the interconnected network of feeding relationships among organisms within an ecosystem. They illustrate the transfer of energy and nutrients as organisms consume each other. - Energy flows through food webs in a unidirectional manner, starting from primary 12 producers (autotrophs) and moving through various trophic levels (herbivores, carnivores, etc.) as energy is transferred from one organism to another. - Energy is continuously lost at each trophic level through metabolic processes (respiration), heat production, and waste, resulting in a decrease in available energy as you move up the food chain. 3. **Efficiency Metrics**: a. **Assimilation Efficiency**: - Assimilation efficiency represents the proportion of ingested food that is assimilated or absorbed by an organism's digestive system and utilized for growth and other physiological functions. - It is calculated as the ratio of assimilated energy to ingested energy, expressed as a percentage. - Assimilation efficiency can vary among different organisms and is influenced by factors such as digestive efficiency, food quality, and metabolic rate. - High assimilation efficiency means that a larger proportion of ingested food is effectively utilized, while low assimilation efficiency indicates that a significant portion of ingested energy is lost as undigested waste. b. **Production Efficiency**: - Production efficiency represents the efficiency with which assimilated energy is converted into new biomass or growth. - It is calculated as the ratio of secondary production (growth or biomass production) to assimilated energy, expressed as a percentage. - Production efficiency reflects the metabolic efficiency and growth rates of organisms within an ecosystem. - Higher production efficiency indicates that a larger proportion of assimilated energy is allocated towards growth and reproduction, while lower production efficiency suggests higher energy losses through respiration and other metabolic processes. **Example**: - In a food web, a herbivore consumes plant material, and assimilates a portion of the ingested energy through digestion. The assimilated energy is then used for growth and other metabolic processes. Assimilation efficiency measures how effectively the herbivore absorbs and utilizes the energy from its food. Production efficiency, on the other hand, measures how efficiently the assimilated energy is converted into new biomass or growth by the herbivore. Understanding assimilation efficiency and production efficiency helps ecologists quantify the efficiency of energy transfer and utilization within food webs, and provides insights into ecosystem functioning and trophic dynamics. 12 There are several reasons why production efficiency can vary among organisms within an ecosystem: 1. **Metabolic Rate**: - Organisms with higher metabolic rates tend to have lower production efficiencies because a larger proportion of assimilated energy is allocated towards meeting metabolic demands (e.g., maintenance, locomotion, thermoregulation) rather than growth and reproduction. Species with lower metabolic rates may allocate more energy towards growth and reproduction, resulting in higher production efficiencies. 2. **Feeding Strategy**: - Feeding strategies and dietary preferences can influence production efficiency. For example, herbivores generally have lower production efficiencies compared to carnivores. Plant material is often more difficult to digest and contains structural compounds (e.g., cellulose) that require additional energy for breakdown. Carnivores, on the other hand, may have higher production efficiencies because animal tissues are typically more energy-rich and easier to digest. 3. **Digestive Efficiency**: 13 - Variations in digestive physiology and efficiency can affect how effectively organisms extract nutrients and energy from their food. Species with more efficient digestive systems may have higher production efficiencies because they can assimilate a larger proportion of ingested energy. Conversely, species with less efficient digestive systems may have lower production efficiencies due to higher energy losses in the form of undigested waste. 4. **Life History Traits**: - Life history traits such as reproductive strategy, growth rate, and longevity can influence production efficiency. Organisms with fast growth rates and short lifespans may allocate more energy towards growth and reproduction, resulting in higher production efficiencies during their rapid growth phases. In contrast, organisms with slower growth rates and longer lifespans may invest more energy in maintenance and survival, leading to lower production efficiencies. 5. **Environmental Conditions**: - Environmental factors such as temperature, resource availability, and habitat quality can influence production efficiency. Optimal environmental conditions that promote growth, such as abundant food resources and favorable temperatures, may enhance production efficiency. Conversely, stressful or resource-limited environments may constrain growth and reduce production efficiency. 6. **Trophic Level**: - Production efficiency tends to decrease with increasing trophic level in food webs. Primary producers (plants, algae) generally have higher production efficiencies compared to herbivores, which in turn have higher production efficiencies than carnivores. This pattern reflects the energy losses that occur at each trophic transfer due to metabolic processes, heat production, and inefficiencies in energy transfer. Overall, variation in production efficiency among organisms is influenced by a combination of physiological, ecological, and environmental factors that determine how efficiently organisms assimilate and utilize energy for growth and reproduction within an ecosystem. 13 The terms "Green Food Web" and "Brown Food Web" refer to two different pathways of energy flow and nutrient cycling within ecosystems, particularly in aquatic environments. These pathways are based on the sources of organic matter that support the food web: 1. **Green Food Web**: - The Green Food Web primarily relies on the direct input of freshly produced organic matter from photosynthesis, typically by autotrophic organisms such as plants and algae. - In this pathway, energy flows directly from primary producers (plants or algae) to herbivores (primary consumers), and subsequently to higher trophic levels (carnivores, omnivores). - The energy and nutrients produced through photosynthesis are transferred directly to consumers, supporting a relatively short and efficient food chain. - Green food webs are common in ecosystems with high primary productivity, such as freshwater lakes, estuaries, and coastal marine environments where ample sunlight and nutrient availability support rapid plant growth. 2. **Brown Food Web**: 14 - The Brown Food Web, also known as the Detrital Food Web, primarily relies on the decomposition of organic matter derived from dead plant material, animal remains, and fecal matter. - In this pathway, energy flows from detritus (dead organic matter) to decomposers such as bacteria, fungi, and detritivores (organisms that feed on decaying organic matter). - Decomposers break down complex organic molecules into simpler forms, releasing nutrients back into the environment and making them available for uptake by primary producers. - Energy and nutrients stored in detritus are recycled through the ecosystem, supporting a diverse community of decomposers and detritivores. - Brown food webs are prevalent in ecosystems where primary productivity is lower or where organic matter input from external sources (e.g., leaf litter, woody debris) is significant, such as streams, rivers, wetlands, and deep-sea environments. **Key Differences**: - The main distinction between the Green and Brown Food Webs lies in the source of organic matter that fuels energy flow and nutrient cycling within the ecosystem. - In the Green Food Web, energy originates from freshly produced organic matter through photosynthesis, while in the Brown Food Web, energy originates from decomposing organic matter. - Both pathways are essential for ecosystem functioning and support different trophic interactions and species diversity within ecosystems. Understanding the dynamics of both Green and Brown Food Webs is crucial for comprehending energy flow, nutrient cycling, and ecosystem functioning in aquatic environments and provides insights into the structure and resilience of these ecosystems. 14 The concepts you mentioned - "Food Web Energy Flows & Trophic Efficiency," the "10% Rule," and the role of decomposers in energy storage - are fundamental principles in ecology that help us understand how energy flows through ecosystems and the constraints on trophic dynamics. Let's break down each concept and how they relate to each other: 1. **Food Web Energy Flows & Trophic Efficiency**: - Energy flows through ecosystems via food webs, starting with primary producers (e.g., plants, algae) converting solar energy into chemical energy through photosynthesis. - This energy is then transferred to herbivores (primary consumers), which are consumed by carnivores (secondary consumers), and so on, forming a series of trophic levels. - Trophic efficiency refers to the proportion of energy transferred from one trophic level to the next. It is typically low, with a significant portion of energy lost as heat or used for metabolic processes at each transfer. - Trophic efficiency determines the efficiency of energy transfer and biomass production within food webs, influencing the structure and dynamics of ecosystems. 15 2. **"10% Rule"**: - The "10% Rule" is a general guideline stating that approximately 10% of energy is transferred from one trophic level to the next in a food chain. - This rule highlights the inefficiency of energy transfer in ecosystems, with the majority of energy lost as heat or used for metabolic activities such as respiration. - For example, if 1,000 units of energy are available at the primary producer level, only around 100 units will be transferred to herbivores, 10 units to primary carnivores, and so on. - The 10% rule helps explain why food chains are typically limited in length and why ecosystems can support fewer individuals at higher trophic levels. 3. **Losses at Each Trophic Level**: - Losses of energy occur at each trophic level due to metabolic processes, heat production, and inefficiencies in energy transfer. - Organisms expend energy on activities such as movement, growth, reproduction, and maintaining homeostasis, leading to energy losses as heat. - These energy losses constrain the amount of energy available for transfer to higher trophic levels, ultimately limiting the number of trophic levels that can be supported in a food web. 4. **Decomposers and Energy Storage**: - Decomposers play a crucial role in energy cycling and nutrient recycling within ecosystems by breaking down dead organic matter (detritus) into simpler forms. - While decomposers do not contribute significantly to biomass production, they play a vital role in storing and releasing energy and nutrients back into the ecosystem. - Energy stored in decomposers' biomass is eventually released through decomposition, making it available for uptake by primary producers and supporting primary production in the ecosystem. **Example - Light Energy Input**: - In your provided example, light energy input into the ecosystem is 20,000 kcal/m^2. - As energy flows through trophic levels, it decreases by approximately 10% at each transfer. - Following the 10% rule, energy available to primary consumers would be around 2,000 kcal/m^2, to secondary consumers around 200 kcal/m^2, to tertiary consumers around 20 kcal/m^2, and so on. - The remaining energy is lost as heat or used for metabolic processes at each trophic level. In summary, understanding food web energy flows, trophic efficiency, and the role of decomposers is essential for comprehending the dynamics of energy transfer, biomass production, and nutrient cycling within ecosystems. These concepts provide 15 insights into the structure, functioning, and resilience of ecosystems and help inform conservation and management efforts. 15 The concept of "inverted pyramids" refers to a situation in ecological food webs where the biomass or energy at higher trophic levels exceeds that of lower trophic levels. This contrasts with the traditional pyramid-shaped trophic structure, where biomass or energy decreases at each higher trophic level. Let's compare the trophic structures of the grassland and pond ecosystems you provided to understand the concept of inverted pyramids: 1. **Grassland Ecosystem (Upright Pyramid)**: - In a grassland ecosystem, the trophic structure typically follows an upright pyramid shape, where biomass or energy decreases as you move up the food chain. - Primary producers in grasslands are plants, such as grasses, which convert sunlight into chemical energy through photosynthesis. - Primary consumers, like mice, feed directly on plants, utilizing the energy stored in plant tissues. - Secondary consumers, such as snakes, prey on primary consumers, and tertiary consumers like eagles may feed on secondary consumers. - In this upright pyramid structure, there is a large base of primary producers supporting fewer individuals at higher trophic levels, reflecting the loss of energy as it moves up the food chain. 16 2. **Pond Ecosystem (Inverted Pyramid)**: - In contrast, many aquatic ecosystems, including ponds, often exhibit inverted pyramid trophic structures. - In a pond ecosystem, primary producers are often phytoplankton, microscopic algae that float in the water and perform photosynthesis. - Primary consumers, such as zooplankton, feed on phytoplankton, utilizing the energy stored in algal cells. - Secondary consumers, like small fishes, prey on zooplankton, and tertiary consumers such as large fishes may consume smaller fish. - Inverted pyramid structures in aquatic ecosystems occur because phytoplankton populations can grow rapidly and support large populations of primary consumers. Additionally, energy transfer efficiencies may be higher in aquatic environments, allowing more energy to be transferred to higher trophic levels. **Explanation of Inverted Pyramids**: - In aquatic ecosystems like ponds, the high reproductive rates of primary producers (phytoplankton) can result in abundant biomass, supporting a larger number of primary consumers (zooplankton). - This abundance of primary consumers can then support a higher biomass of secondary and tertiary consumers, leading to an inverted pyramid structure where biomass or energy increases at higher trophic levels. - Factors such as efficient energy transfer, rapid growth rates, and high reproductive capacities of aquatic organisms contribute to the formation of inverted pyramids in many aquatic ecosystems. Understanding the trophic structure of ecosystems, whether upright or inverted, provides insights into energy flow, nutrient cycling, and the dynamics of species interactions within ecosystems. 16 Notes Sure, let's break down each of these concepts related to ecosystem energetics, productivity, and dynamics: 1. **Ecosystem**: An ecosystem refers to a community of living organisms interacting with each other and their physical environment. 2. **Closed/open systems; How do living systems avoid entropy?**: Closed systems do not exchange matter with their surroundings, while open systems do. Living systems maintain their organization and avoid entropy by constantly exchanging energy and matter with their surroundings. Through processes like metabolism, organisms take in energy and nutrients, which they use to maintain their structure and function, thus counteracting the tendency towards disorder (entropy). 3. **Energetics**: Energetics in ecosystems refer to the flow of energy through the system, including its capture, storage, and transfer among organisms. 4. **Gross Primary Productivity/Production (GPP)**: GPP is the total amount of energy that primary producers (like plants) capture through photosynthesis in an ecosystem. 17 5. **Net Primary Productivity/Production (NPP)**: NPP is the amount of energy that primary producers store in their tissues after subtracting the energy they use for respiration (R). 6. **Net Ecosystem Productivity/Production (NEP)**: NEP is the overall balance between GPP and ecosystem respiration, representing the net accumulation or loss of organic matter in the ecosystem. 7. **Respiration (R)**: Respiration refers to the process by which organisms release energy from organic molecules. Autotrophic respiration (Ra) is the respiration of primary producers, while heterotrophic respiration (Rh) is the respiration of consumers. Ecosystem respiration (ER) is the total respiration occurring within an ecosystem. 8. **Biomass; Secondary Productivity/Production**: Biomass refers to the total mass of living organisms in an ecosystem. Secondary productivity refers to the rate at which consumers convert organic matter into biomass. 9. **Methods used to estimate GPP, NPP, NEP in terrestrial and aquatic ecosystems**: These can include techniques such as measuring carbon dioxide exchange, biomass accumulation, and remote sensing methods. 10. **Controls on NPP, NEP in terrestrial and aquatic ecosystems**: Factors influencing NPP and NEP include temperature, moisture, nutrient availability, and disturbances like fire or grazing. 11. **Temporal variation in ecosystem energetics**: Ecosystem energetics can vary seasonally due to factors like temperature, light availability, and the phenology of plants. 12. **Autochthonous, Allochthonous**: Autochthonous refers to energy and nutrients produced within an ecosystem, while allochthonous refers to inputs from outside the ecosystem. 13. **Secondary Production**: Ingestion refers to the consumption of organic matter, assimilation is the incorporation of consumed energy into the consumer's biomass, egestion is the removal of undigested material, and respiration is the release of energy through metabolic processes. 14. **River Continuum Concept**: This concept describes how energy and nutrients flow through river ecosystems, from headwaters to larger rivers, influencing the 17 structure and function of aquatic communities. 15. **Food Web Energy Flows & Efficiency**: In food webs, energy flows from primary producers to consumers through ingestion, assimilation, and ultimately, respiration. Efficiency measures how much energy is transferred from one trophic level to the next. 16. **"Green Food Web" vs "Brown Food Web"**: The green food web refers to the flow of energy and nutrients through autotrophic organisms (plants), while the brown food web refers to the decomposition of organic matter by detritivores and decomposers. 17. **Trophic Efficiency**: Trophic efficiency is the percentage of energy transferred from one trophic level to the next, typically ranging from 5% to 20%. It is influenced by factors such as the efficiency of digestion and metabolic processes. 17