STANDARD 17_INTERDEPENDENCE
SC.912.17.9 Food chains, Food Webs, and Energy Transfer
You must be able to:
- Identify and distinguish producers, consumers, and decomposers.
- Explain the pathway of energy transfer through trophic levels and the reduction of available energy at the successive trophic levels.
An ecosystem consists of all the organisms living (biotic) in a community, as well as all the abiotic factors with which they interact with.
Regardless of an ecosystem’s size, its dynamics involve two main processes:
Regardless of an ecosystem’s size, its dynamics involve two main processes:
- energy flow and
- chemical cycling
- Energy flows through ecosystems while matter cycles within them
- Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) and then to secondary consumers (carnivores)
Food Chains
All living things require food to survive. A food chain illustrates a possible pathway that energy and nutrients can move through the ecosystem.
- A food chain is a linear network of links in a food web starting from producer organisms and ending at apex predator species, detritivores, or decomposer species. Each step or link in the food chain is a trophic level.
- Organisms in food chains are grouped into categories called trophic levels. These levels are divided into producers (first trophic level), consumers (second, third, and fourth trophic levels), and decomposers.
Trophic Levels
Trophic levels are the feeding positions of all organisms in a specific ecosystem, so that will depend on the organisms' role in the environment:
Producers:
Producers are always the first trophic level in a food chain. They are autotrophs, organisms capable of making its own organic food from inorganic molecules. These include:
Trophic levels are the feeding positions of all organisms in a specific ecosystem, so that will depend on the organisms' role in the environment:
Producers:
Producers are always the first trophic level in a food chain. They are autotrophs, organisms capable of making its own organic food from inorganic molecules. These include:
- Photosynthetic producers like plant, phytoplankton, algae, and some bacteria.
- Chemosynthetic producers such as some bacteria leaving in hydrothermal vents that produce their own food in the absence of light.
Consumers:
The second trophic level consists of organisms that eat the producers. These are called primary consumers, or herbivores. Deer, turtles, and many types of birds are herbivores. Secondary consumers eat the herbivores. Tertiary consumers eat the secondary consumers. There may be more levels of consumers before a chain finally reaches its top predator. Top predators, also called apex predators, eat other consumers.
Consumers can be carnivores (animals that eat other animals) or omnivores (animals that eat both plants and animals). Omnivores, like people, consume many types of foods. People eat plants, such as vegetables and fruits. We also eat animals and animal products, such as meat, milk, and eggs. We eat fungi, such as mushrooms. We also eat algae, in edible seaweeds like nori (used to wrap sushi rolls) and sea lettuce (used in salads).
Detritivores and decomposers are the final part of food chains. Detritivores are organisms that eat nonliving plant and animal remains. For example, scavengers such as vultures eat dead animals. Dung beetles eat animal feces.
Decomposers like fungi and bacteria complete the food chain. They turn organic wastes, such as decaying plants, into inorganic materials, such as nutrient-rich soil. Decomposers complete the cycle of life, returning nutrients to the soil or oceans for use by autotrophs. This starts a whole new food chain.
The second trophic level consists of organisms that eat the producers. These are called primary consumers, or herbivores. Deer, turtles, and many types of birds are herbivores. Secondary consumers eat the herbivores. Tertiary consumers eat the secondary consumers. There may be more levels of consumers before a chain finally reaches its top predator. Top predators, also called apex predators, eat other consumers.
Consumers can be carnivores (animals that eat other animals) or omnivores (animals that eat both plants and animals). Omnivores, like people, consume many types of foods. People eat plants, such as vegetables and fruits. We also eat animals and animal products, such as meat, milk, and eggs. We eat fungi, such as mushrooms. We also eat algae, in edible seaweeds like nori (used to wrap sushi rolls) and sea lettuce (used in salads).
Detritivores and decomposers are the final part of food chains. Detritivores are organisms that eat nonliving plant and animal remains. For example, scavengers such as vultures eat dead animals. Dung beetles eat animal feces.
Decomposers like fungi and bacteria complete the food chain. They turn organic wastes, such as decaying plants, into inorganic materials, such as nutrient-rich soil. Decomposers complete the cycle of life, returning nutrients to the soil or oceans for use by autotrophs. This starts a whole new food chain.
Food Webs
Food webs are many interconnected food chains, representing feeding relationships within a community.
Energy Pyramids and Energy Transfer
The laws of physics and chemistry apply to ecosystems, particularly in regard to the flow of energy.
- Energy is conserved
- But degraded to heat during ecosystem processes
- Only about 10% is passed on to the next trophic level
- About 90% is lost as heat (not really lost, but not available to use again)
Energy Pyramids:
- Shows the amounts of energy available at each trophic level of an ecosystem
- The higher in the pyramid, the less energy available