What do you know about energy pyramids and how they relate to the the ocean ecosystem? In this lesson, you will learn what an energy pyramid is as well as what the energy pyramid of the ocean looks like.
On the Hunt
A group of killer whales has been swimming for the last hour. They have been communicating by sending out sound waves, all in an effort to find a suitable lunch. Finally, one of the group members has something! He lets the group know, that about 100 meters east, there is a school of fish. The group plans their attack strategy, based on information they receive via the sound waves they bounce in the direction of the group of fish. As the group of killer whales approach the fish, they are spotted, but its too late.
The whales have attacked groups like these before and know what to do. The whales are lucky to get such a tasty lunch, and that all their efforts paid off, since this is not always the case.
A Very Costly Lunch
The killer whale and its group were described as lucky in the previous paragraph. They were described as such, because they successfully were able to obtain a meal. Sometimes, the great deal of energy they put into capturing prey pays off, and sometimes it does not.
Meals are not only expensive in regards to energy output for killer whales, but for all the organisms in the ocean. Unlike humans, a great white shark can’t go to his local fish market to purchase a box of fresh tuna! Great white sharks have to swim and hunt for their food. The killer whale and the great white shark expend quite a bit of energy to get a small return. Both organisms eat very costly meals.
Only Ten Percent?
The 10% Rule states that only ten percent of the energy contained in an organism is transferred from one trophic level to the next.
For example, lets remember the killer whales in our introductory paragraph. The group of killer whales were successful in feeding off of the school of fish. Before the fish became lunch for the whales, they did not know they were not going to make it through the day, so before their demise, the fish went about their normal activities. All of those activities required energy.
Some of the energy that was once contained in those fish was not passed onto the group of killer whales. Some of the energy contained in the fish was used to feed, swim, etc.Additionally, the killer whales used sound waves to locate the fish, communicated with one another, swam to find the fish, etc. All of that required energy. A lot of the energy the whales expended happened before they were even able to eat the fish.
After all of the effort put into obtaining his meal, the killer whales will only end up with a net gain of ten percent energy transfer from the group of fish.
Energy Pyramids ; Trophic Levels
An energy pyramid depicts the trophic levels of organisms in an environment and gives a visual representation of energy loss at each level.
Energy pyramids start with the sun as the source of all energy.
The energy pyramid also lists the trophic levels in order.
- Tertiary consumers: carnivores, or meat eaters (at the top)
- Secondary consumers: omnivores, or plant and animal eaters
- Primary consumers: herbivores, or plant eaters
- Producers: plants (on the bottom)
Again, as energy originates from the sun and travels through each trophic level, only ten percent of the energy will be carried on to the next level. Some of the energy is lost as heat, and each organism uses some of what it obtains for its life processes.
When an organism is eaten, it can pass on the energy that is left over. Any organism that depends on another source for energy also has to expend energy to get its food, thus continuing the pattern. View the examples of energy pyramids below. If you start with producers and move up the pyramid, the amount of available energy decreases.
The 10% Rule states that only ten percent of the energy contained is transferred from one trophic level to the next. An energy pyramid depicts the trophic levels of organisms in an environment and gives a visual representation of energy loss at each level.
The energy pyramid also lists the trophic levels in order:
- Tertiary consumers (meat eaters/carnivore)
- Secondary consumers (eat plants and animals/omnivores)
- Primary consumers (herbivores)
- Producers (plants)