How Much Energy to Consumers Obtain When They Eat? What Happened to the Rest?
Life on the Nutrient Chain
Accept y'all ever wondered why nosotros tin can't seem to feed the world's hungry? It'south a complex issue, only information technology might surprise you to learn that it'southward not because there isn't enough nutrient; current agricultural capacity, based on electric current engineering science, exists to feed as many as ten billion people. The Globe's population is "just" almost 7 billion. The big question really is: If we want to feed anybody, what would everyone need to eat? To respond that question, download this excel spreadsheet and try plugging in some numbers.
Instance: One acre of a grain ingather could be used to feed cattle, and and so the cattle could exist used to feed people. If 50% of the energy is lost to the cattle, you lot could feed twice every bit many people if yous fed them the grain straight. Some other way of looking at it is that it would only take a half acre of land to feed the people grain, just a whole acre if you feed the grain to the cattle and the cattle to the people. A common practice to grow cattle faster is to feed them ground up animal protein. This ways that when we eat the meat from the moo-cow, we're at the third level or higher. The loss of free energy betwixt trophic levels may likewise be even higher. Recent studies suggest that merely ~10% of free energy is converted to biomass from one trophic level to the side by side!
The Food Chain: The answer has to do with trophic levels. As you lot probably know, the organisms at the base of the food chain are photosynthetic; plants on land and phytoplankton (algae) in the oceans. These organisms are called the producers, and they become their free energy directly from sunlight and inorganic nutrients. The organisms that eat the producers are the primary consumers. They tend to be small in size and there are many of them. The primary consumers are herbivores (vegetarians). The organisms that eat the primary consumers are meat eaters (carnivores) and are called the secondary consumers. The secondary consumers tend to be larger and fewer in number. This continues on, all the way up to the top of the food chain. About l% of the energy (possibly as much equally 90%) in food is lost at each trophic level when an organism is eaten, then it is less efficient to be a higher order consumer than a chief consumer. Therefore, the energy transfer from ane trophic level to the next, up the food chain, is like a pyramid; wider at the base and narrower at the top. Considering of this inefficiency, in that location is only enough food for a few top level consumers, simply there is lots of nutrient for herbivores lower down on the nutrient chain. There are fewer consumers than producers.
Land and aquatic energy pyramids
| Trophic Level | Desert Biome | Grassland Biome | Pond Biome | Ocean Biome |
|---|---|---|---|---|
| Producer (Photosynthetic) | Cactus | Grass | Algae | Phytoplankton |
| Primary Consumer (Plant eater) | Butterfly | Grasshopper | Insect Larva | Zooplankton |
| Secondary Consumer (Carnivore) | Cadger | Mouse | Minnow | Fish |
| Tertiary Consumer (Carnivore) | Snake | Snake | Frog | Seal |
| Fourth Consumer (Carnivore) | Roadrunner | Hawk | Raccoon | Shark |
Nutrient Web: At each trophic level, there may exist many more than species than indicated in the table to a higher place. Food webs can be very circuitous. Food availability may vary seasonally or by time of day. An organism like a mouse might play ii roles, eating insects on occasion (making information technology a secondary consumer), only also dining straight on plants (making it a primary consumer). A food web of who eats who in the southwest American desert biome might look something like this:
image source: http://iqa.evergreenps.org/science/biology/ecosystem_files/food-web.jpg
Keystone Species: In some food webs, there is one disquisitional "keystone species" upon which the entire system depends. In the aforementioned way that an arch collapses when the keystone is removed, an entire food concatenation can collapse if in that location is a decline in a keystone species. Often, the keystone species is a predator that keeps the herbivores in check, and prevents them from overconsuming the plants, leading to a massive die off. When nosotros remove top predators like grizzly bears, orca whales, or wolves, for instance, there is evidence that information technology affects not just the prey species, but even the physical environment.
Noon Predators: These species are at the top of the nutrient chain and the healthy adults have no natural predators. The young and old may in some cases be preyed upon, but they typically succumb to illness, hunger, the effects of aging, or some combination of them. The also suffer from competition with humans, who often eliminate the superlative predators in club to have sectional admission to the casualty species, or through habitat destruction, which is an indirect course of competition.
Decomposers: When organisms dice, they are sometimes eaten by scavengers just the remaining tissues are broken downwardly by fungi and bacteria. In this way, the nutrients that were part of the body are returned to the lesser of the trophic pyramid.
Bioaccumulation: In addition to being less energy efficient, eating college up the nutrient concatenation has its risks. Pesticides and heavy metals like mercury, arsenic, and lead tend to exist consumed in minor quantities by the principal consumers. These toxins get stored in the fats of the animal. When this animal is eaten by a secondary consumer, these toxins become more concentrated because secondary consumers consume lots of primary consumers, and frequently live longer too. Swordfish and tuna are near the height of the aquatic food chain and, when nosotros eat them, nosotros are consuming all of the toxins that they have accumulated over a lifetime. For this reason, significant women are advised confronting eating these foods.
Solve the following problems mathematically.
1. Given: 10 billion people can be fed a basic vegetarian nutrition that is nutritionally complete. How many people could we feed at the American standard-a tertiary level of consumption (3rd social club consumers?). l% of the energy is lost by each higher level.
ii. If there are 250 million people in the United states of america most of them eating at the Tertiary (tertiary) level of consumption, how many people could we feed at the Principal level?
3. Some animals like sharks are 5th order consumers! Sharks eat tuna that eat mackerel that swallow herring that consume copepods that eat diatoms. If we were to make the reasonable assumption that each of these animals eats 2 of its prey each day, how many organisms died to feed the shark in one day?
Source: https://www2.nau.edu/lrm22/lessons/food_chain/food_chain.html
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