The second consumers (trophic level 3) in the desert food web include birds and scorpions, and tertiary consumers making up the fourth trophic level include bird predators and foxes. The remaining trophic levels include carnivores that consume animals at trophic levels below them. The second trophic level consists of herbivores. They convert inorganic chemical and use solar energy to generate chemical energy. Basal species occupy the lowest trophic level as primary producer. These feeding groups are referred as trophic levels. All species in the food webs can be distinguished into basal species (autotrophs, such as plants), intermediate species (herbivores and intermediate level carnivores, such as grasshopper and scorpion) or top predators (high level carnivores such as fox) (Figure 1). Food webs can be constructed to describe the species interactions. The fundamental purpose of food webs is to describe feeding relationship among species in a community. The most effective control was exerted by sea urchin Stronglocentrotus and the chiton Katharina (Ricklefs 2008). mitra in the community consume considerable food energy (energy flow web), but removal of these consumers has no detectable influence on the abundance of their resources (functional web). As shown in Figure 2, limpets Acmaea pelta and A. Functional webs (or interaction food webs) represent the importance of each species in maintaining the integrity of a community and reflect influence on the growth rate of other species' populations. Thickness of an arrow reflects the strength of the relationship. Energy flow webs quantify energy flow from one species to another. Connectedness webs (or topological food webs) emphasize feeding relationships among species, portrayed as links in a food web (Paine 1980). Based on different ways in which species influence one another, Robert Paine proposed three types of food webs based on the species of a rocky intertidal zone on the coast of Washington (Ricklefs 2008, Figure 2). Some connections are more influential on species population change. Some trophic relationships are more important than others in dictating how energy flows through ecosystems. Types of Food WebsFood webs describe the relationships - links or connections - among species in an ecosystem, but the relationships vary in their importance to energy flow and dynamics of species populations. The feeding interactions represented by the food web may have profound effects on species richness of community, and ecosystem productivity and stability (Ricklefs 2008). In 1927, he recognized that the length of these food chains was mostly limited to 4 or 5 links and the food chains were not isolated, but hooked together into food webs (which he called "food cycles"). The idea to apply the food chains to ecology and to analyze its consequences was first proposed by Charles Elton (Krebs 2009). For example, the predators of a scorpion in a desert ecosystem might be a golden eagle, an owl, a roadrunner, or a fox. While the food web showed here is a simple one, most feed webs are complex and involve many species with both strong and weak interactions among them (Pimm et al. In this food web, grasshoppers feed on plants scorpions prey on grasshoppers kit foxes prey on scorpions. Figure 1 shows a simplified food web in a desert ecosystem. In a detrital food chain, dead organic matter of plants and animals is broken down by decomposers, e.g., bacteria and fungi, and moves to detritivores and then carnivores.įood web offers an important tool for investigating the ecological interactions that define energy flows and predator-prey relationship (Cain et al. In a grazing food chain, energy and nutrients move from plants to the herbivores consuming them, and to the carnivores or omnivores preying upon the herbivores. There are two types of food chains: the grazing food chain, beginning with autotrophs, and the detrital food chain, beginning with dead organic matter (Smith & Smith 2009). Each food chain is a descriptive diagram including a series of arrows, each pointing from one species to another, representing the flow of food energy from one feeding group of organisms to another. Normally, food webs consist of a number of food chains meshed together. It also implies the transfer of food energy from its source in plants through herbivores to carnivores (Krebs 2009). Basically, food web represents feeding relationships within a community (Smith and Smith 2009). Food web is an important ecological concept.
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