Ecosystems: Videos & Practice Problems
Ecosystems consist of communities of organisms and their environments, where energy flows and matter cycles. Energy, primarily from the sun, is transferred through trophic levels, with only about 10% efficiency at each level, leading to a pyramid of net production. Matter, however, is recycled, as seen in biogeochemical cycles like the carbon and nitrogen cycles. Limiting factors such as nutrient availability and temperature affect productivity. Decomposers play a crucial role in returning nutrients to the ecosystem, while biomagnification highlights the concentration of toxins at higher trophic levels.
Ecosystems, Energy, and Matter
Producers and Consumers
Primary Production
Limiting Factors to Primary Production
Secondary Production and Trophic Efficiency
Biomagnification and Decomposers
Water Cycle
Carbon, Nitrogen, and Phosphorous Cycle
Dig Deeper into Introduction to Ecosystems
An ecosystem is a community of living organisms interacting with their abiotic environment in a specific area.
Key Terminology
- Ecosystem: A biological community of interacting organisms and their physical environment including both biotic and abiotic components.
- Abiotic: Nonliving chemical and physical factors in the environment, such as sunlight, temperature, and moisture.
- Autotrophs: Organisms that produce their own nutrients from inorganic sources, often through photosynthesis; also called primary producers.
- Heterotrophs: Organisms that obtain nutrients by consuming other organisms; also known as consumers.
- Primary producers: Autotrophs that form the base of the food chain by converting solar energy into chemical energy.
- Trophic level: The position an organism occupies in a food chain, such as primary producer, primary consumer, secondary consumer, etc.
- Grazing food chain: A food chain where primary consumers feed on living plants or autotrophs.
- Detritus-based food chain: A food chain where primary consumers feed on detritus, which is dead organic matter and waste.
- Detritus: Dead organic matter and waste material that serves as a nutrient source for decomposers and detritivores.
- Decomposers: Organisms, such as fungi and bacteria, that break down dead organic matter and recycle chemicals back into the ecosystem.
- Chemical cycling: The process by which nutrients and chemicals are recycled within an ecosystem through biogeochemical cycles.
- One-way energy flow: The movement of energy through an ecosystem in a single direction, from the sun to autotrophs and then through consumers, with energy lost as heat at each transfer.
- Primary consumers: Organisms that feed directly on primary producers, often herbivores in grazing food chains.
- Detritivores: Organisms that consume detritus, aiding in decomposition and nutrient recycling.
- Energy loss as heat: The inevitable loss of usable energy as heat during energy transfers, which drives the one-way flow of energy in ecosystems.
- Reservoir: A storage location for chemicals or nutrients, such as soil acting as a reservoir for nutrients used by plants.
Real-World Applications
- Understanding chemical cycling and energy flow helps in ecosystem management and conservation efforts, ensuring sustainable use of natural resources and maintaining biodiversity.
- Knowledge of decomposition rates influenced by temperature, moisture, and oxygen informs agricultural practices and waste management, optimizing nutrient recycling and soil health.
- Studying grazing and detritus-based food chains aids in ecosystem restoration projects by identifying key species that maintain nutrient cycling and energy flow.
Common Misconceptions
- Energy cycles through ecosystems like chemicals do — actually, energy flows in one direction and is lost as heat, so ecosystems need a constant energy input, usually from the sun.
- Only living plants serve as primary producers — in some ecosystems, like deep-sea hydrothermal vents, autotrophs use chemical energy instead of sunlight to produce nutrients.
- Decomposers are optional in ecosystems — decomposers are essential for recycling chemicals and completing nutrient cycles, without which ecosystems would accumulate waste and nutrients would be locked up.
- An organism can only occupy one trophic level — many organisms feed at multiple trophic levels depending on the food chain, such as an owl acting as both a primary and tertiary consumer.
Do you want more practice?
Here’s what students ask on this topic:
What is the difference between energy flow and matter cycling in ecosystems?
In ecosystems, energy flow and matter cycling are two fundamental processes. Energy flow refers to the transfer of energy through trophic levels, starting from the sun to primary producers (autotrophs) and then to various consumers. This process is inefficient, with only about 10% of energy being transferred to the next trophic level, and most energy is eventually lost as heat. In contrast, matter cycling involves the recycling of elements like carbon, nitrogen, and phosphorus through biogeochemical cycles. Matter is not lost but continuously reused within the ecosystem. For example, carbon cycles through photosynthesis and respiration, while nitrogen is fixed by bacteria and used by plants. Thus, energy flows through ecosystems and is lost, whereas matter is recycled.
What are trophic levels and how do they function in a food chain?
Trophic levels describe the hierarchical positions organisms occupy in a food chain based on their feeding habits. The primary producers, or autotrophs, form the base of the food chain by converting inorganic matter into biomass through photosynthesis or chemosynthesis. Primary consumers, usually herbivores, feed on these producers. Secondary consumers are carnivores that eat primary consumers, and tertiary consumers are carnivores that feed on other carnivores. Decomposers, or detritivores, play a crucial role by breaking down dead organic matter and returning nutrients to the ecosystem. This linear sequence of energy transfer from one trophic level to the next forms a food chain, which can interlink to form a more complex food web.
What is biomagnification and how does it affect higher trophic levels?
Biomagnification is the process by which certain substances, such as toxins, become more concentrated at higher trophic levels in a food web. These substances are often not easily digested or excreted, leading to their accumulation in organisms' tissues. As organisms at lower trophic levels are consumed by those at higher levels, the concentration of these substances increases. For example, if primary producers contain a small amount of a toxin, primary consumers that eat large quantities of these producers will accumulate more of the toxin. This process continues up the food chain, resulting in the highest concentrations of toxins in top predators, which can have harmful effects on their health and survival.
What are the main limiting factors for primary production in aquatic and terrestrial ecosystems?
In aquatic ecosystems, the main limiting factors for primary production are light penetration and nutrient availability. Light is essential for photosynthesis, and its penetration can be limited by water depth and turbidity. Nutrient availability, particularly nitrogen and phosphorus, is often the bottleneck for primary production in aquatic environments. In terrestrial ecosystems, temperature and water availability are the primary limiting factors. Soils also have limiting nutrients, usually nitrogen and phosphorus, which are crucial for plant growth. These factors influence the rate of photosynthesis and biomass production, thereby affecting the overall productivity of the ecosystem.
How do decomposers contribute to nutrient cycling in ecosystems?
Decomposers, such as bacteria, fungi, and detritivores, play a vital role in nutrient cycling by breaking down dead organic matter and waste products. They decompose complex organic materials into simpler inorganic compounds, which are then released back into the soil and water. This process returns essential nutrients like carbon, nitrogen, and phosphorus to the ecosystem, making them available for uptake by primary producers. Decomposers ensure the continuous recycling of matter, maintaining the balance of nutrients in the ecosystem and supporting the growth and survival of various organisms.
