Respuesta :
When one of the levels in a food chain is altered, it changes the anterior and the posterior levels too. The immediately anterior level increases, and the immediately posterior level decreases.
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The trophic web is a relationship process between different organisms, through which occurs transference of energy. The ones placed at lower levels pass energy to the ones at the higher levels.
Organisms at each level feed on the preceding one and become food for the next one.
- The first link corresponds to a producer organism -autotroph-.
- The following links are the consumers -heterotrophs-: herbivores and carnivores.
- The last links are the decomposers that degrade organic matter from dead organisms.
As it is a web, all organisms are equilibrated until a change occurs. When the change affects any of the involved links, there can be a cascade effect on the web. A change in a link population size (increasing or decreasing) will affect the superior links and the immediately anterior link.
Now I will provide you with a simple example of a food chain that includes the crayfish. This is only to exemplify the previously mentioned framework. You can make the same reasoning with your food web (Figure 4-3).
- Crayfish feeds on aquatic plants, algae, small invertebrates, and organic debris.
- Large fish species feed on crayfishes
- Ospreys feed on large fishes
- Producer/Autotroph → aquatic plants, algae
- Primary consumer → Crayfish
- Secondary consumer → Large fish
- Tertiary consumer → Ospreys
- Decomposer → Not mentioned in the chain.
If there is a sudden decrease in the number of crayfishes, there will be
- An increase in aquatic plants, algae, invertebrates, and debris. This is because crayfish used to feed on these species, so their natality and mortality rates were constant. However, since the crayfish number is decreasing, the reproductive rate of their prey increases, and their mortality rate decreases.
- A decrease in the number of large fishes. This is because crayfish were the prey of large fishes. Since there are no crayfishes, large fishes have no food. Their mortality rate increases, and hence their natality rate decreases. The large fishes population decreases in size.
- Ospreys population also decrease. This is because ospreys feed on large fish. But large fishes decreased their number, so there is no food for ospreys. Their mortality rate increases and their natality rate decreases.
Note: This is a simple example, however, there are many more interactions that involve other chains and the same links.
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Related link: https://brainly.com/question/10056813?referrer=searchResults
