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The microbial food web refers to the combined trophic interactions among microbes in aquatic environments. These microbes include viruses, bacteria, algae, heterotrophic protists (such as ciliates and flagellates). [1] In aquatic ecosystems, microbial food webs are essential because they form the basis for the cycling of nutrients and energy.
Most of its life, this haploid social amoeba undergoes a vegetative cycle, preying upon bacteria in the soil, and periodically dividing mitotically. When food is scarce, either the sexual cycle or the social cycle begins. Under the social cycle, amoebae aggregate in response to cAMP by the thousands, and form a motile slug, which moves towards ...
A petri dish of Dictyostelium.. When food (normally bacteria) is readily available dictyostelids behave as individual amoebae, which feed and divide normally. However, when the food supply is exhausted, they aggregate to form a multicellular assembly, called a pseudoplasmodium, grex, or slug (not to be confused with the gastropod mollusc called a slug).
The mean chain length of an entire web is the arithmetic average of the lengths of all chains in a food web. [ 42 ] [ 14 ] In a simple predator-prey example, a deer is one step removed from the plants it eats (chain length = 1) and a wolf that eats the deer is two steps removed from the plants (chain length = 2).
Life cycle. Dictyostelium discoideum is a species of soil-dwelling amoeba belonging to the phylum Amoebozoa, infraphylum Mycetozoa.Commonly referred to as slime mold, D. discoideum is a eukaryote that transitions from a collection of unicellular amoebae into a multicellular slug and then into a fruiting body within its lifetime.
A simplified food web illustrating a three-trophic food chain (producers-herbivores-carnivores) linked to decomposers. The movement of mineral nutrients through the food chain, into the mineral nutrient pool, and back into the trophic system illustrates ecological recycling. The movement of energy, in contrast, is unidirectional and noncyclic.
There are two major food chains: The primary food chain is the energy coming from autotrophs and passed on to the consumers; and the second major food chain is when carnivores eat the herbivores or decomposers that consume the autotrophic energy. [16] Consumers are broken down into primary consumers, secondary consumers and tertiary consumers.
discoideum and other social amoeba differ from free living Acanthamoeba in that instead of encysting, they undergo a social cycle where individual D. discoideum cells aggregate together in a food scarce environment. This social cycle results in a differentiation between cells: ~20% are sacrificed to form a structural stalk, [10] some transform ...