Ecology 4.1 & 4.2 Notes
It is expected that you will be able to define and connect the below-listed vocabulary words:
ecosystem, population, community, organism, species, autotrophs, heterotrophs, saprotrophs, producers, consumers, decomposers, omnivores, detritivores and herbivores.
The best way to understand how these terms connect is to construct a flow chart and/or create either a food chain or food web.
When discussing energy flow, always start with sunlight. Plants (which are producers) absorb sunlight and use photosynthesis to convert the sunlight to chemical energy in the form of glucose. Addition of minerals from the soil allows plants to also produce cellulose, proteins and lipids. Animals (including humans) consume plants and digest them, which breaks molecular bonds and releases the energy animals need to function. By feeding on producers, consumers utilize the energy to grow and stay healthy.
Page 196-97 details how a food chain works. IB uses an arrow to illustrate which organisms consume others. For example, herring --> seal means that the seal eats the herring. Food chains are sequences showing the feeding relationships and energy flow between species. The direction of the arrow shows the direction of energy flow.
Interpret this food chain: algae-->krill-->penguin-->leopard seal
Interpret this food chain: acacia leaves-->giraffe-->lion
**Ask yourself: Where do detritivores fit into these chains?
The glucose produced by producers is converted into energy via cellular respiration. Heat generated by cellular respiration is typically lost to the environment. If an organism is eaten, some of the chemical energy in its body (in the form of protein, for example) is passed on to the organism that consumed it. If the organism dies, detritivores and decomposers will consume the available energy.
Heat energy cannot be recycled. Once heat leaves an organism, it can't be used as a biological energy resource; therefore it is lost (which means it has been converted into another form). As a result, heat is lost from an ecosystem when it is radiated into the environment. It passes from one trophic level to the next and when it leaves the ecosystem, it is not reusable. But as long as the sun shines, ecosystems will continue to get the energy they need.
Only chemical energy can be used by the next trophic level, and only a small amount of energy that an organism absorbs is converted into chemical energy. No organism can use 100% of the energy present in organic molecules of the food it eats. Only about 10-20% of the energy present is used from the previous step in a food chain. Basically, 90% of energy is lost at each level.
Page 198 explains why not all of the energy can be used by another organism in the next trophic level.
Pyramids of energy show how much and how fast energy flows from one trophic level to the next. Make sure you know the units for the energy pyramid. The below image on the right is an example of a pyramid of energy. Notice how the base of the pyramid (the producers) is wide and how the top carnivore base is extremely narrow. Ninety percent of heat is lost at each trophic level, which is why the pyramid looks the way it does.
Food chains typically have four trophic levels. The number of levels is limited by how much energy enters the ecosystem. Because so much is lost, the energy at the start will quickly be lost. Abundant energy at the start can sustain several trophic levels. So the number of organisms in the chain as well as the quantity of light available at the start will determine how long the chain is.
The image on the below left is an example of an ecological pyramid.
ecosystem, population, community, organism, species, autotrophs, heterotrophs, saprotrophs, producers, consumers, decomposers, omnivores, detritivores and herbivores.
The best way to understand how these terms connect is to construct a flow chart and/or create either a food chain or food web.
When discussing energy flow, always start with sunlight. Plants (which are producers) absorb sunlight and use photosynthesis to convert the sunlight to chemical energy in the form of glucose. Addition of minerals from the soil allows plants to also produce cellulose, proteins and lipids. Animals (including humans) consume plants and digest them, which breaks molecular bonds and releases the energy animals need to function. By feeding on producers, consumers utilize the energy to grow and stay healthy.
Page 196-97 details how a food chain works. IB uses an arrow to illustrate which organisms consume others. For example, herring --> seal means that the seal eats the herring. Food chains are sequences showing the feeding relationships and energy flow between species. The direction of the arrow shows the direction of energy flow.
Interpret this food chain: algae-->krill-->penguin-->leopard seal
Interpret this food chain: acacia leaves-->giraffe-->lion
**Ask yourself: Where do detritivores fit into these chains?
The glucose produced by producers is converted into energy via cellular respiration. Heat generated by cellular respiration is typically lost to the environment. If an organism is eaten, some of the chemical energy in its body (in the form of protein, for example) is passed on to the organism that consumed it. If the organism dies, detritivores and decomposers will consume the available energy.
Heat energy cannot be recycled. Once heat leaves an organism, it can't be used as a biological energy resource; therefore it is lost (which means it has been converted into another form). As a result, heat is lost from an ecosystem when it is radiated into the environment. It passes from one trophic level to the next and when it leaves the ecosystem, it is not reusable. But as long as the sun shines, ecosystems will continue to get the energy they need.
Only chemical energy can be used by the next trophic level, and only a small amount of energy that an organism absorbs is converted into chemical energy. No organism can use 100% of the energy present in organic molecules of the food it eats. Only about 10-20% of the energy present is used from the previous step in a food chain. Basically, 90% of energy is lost at each level.
Page 198 explains why not all of the energy can be used by another organism in the next trophic level.
Pyramids of energy show how much and how fast energy flows from one trophic level to the next. Make sure you know the units for the energy pyramid. The below image on the right is an example of a pyramid of energy. Notice how the base of the pyramid (the producers) is wide and how the top carnivore base is extremely narrow. Ninety percent of heat is lost at each trophic level, which is why the pyramid looks the way it does.
Food chains typically have four trophic levels. The number of levels is limited by how much energy enters the ecosystem. Because so much is lost, the energy at the start will quickly be lost. Abundant energy at the start can sustain several trophic levels. So the number of organisms in the chain as well as the quantity of light available at the start will determine how long the chain is.
The image on the below left is an example of an ecological pyramid.