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#niche

2 public questions tagged with this topic.

Stem Cell -l

Which of the following is an example of a stem cell niche?

A functional niche must provide structural support, adhesive contacts, and signaling milieu that maintains stemness. The intestinal crypt exemplifies this model: Paneth cells intercalated with Lgr5-positive stem cells at crypt base secrete Wnt3, EGF, and Notch ligands DLL1 and DLL4, creating high Wnt environment. Stromal telocytes and basement membrane contribute R-spondin and BMP inhibitors. This arrangement promotes proliferation and suppresses differentiation upward along villus. Mature red blood cells, trophoblast, and apoptotic cells lack stem-supporting signaling capacity, thus not considered niches. Crypt architecture demonstrates niche control of division mode and lineage output.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Intestinal crypt as niche example.

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Habitat Niche

Realized niche accurately described as:

“Conditions actually used in presence of competitors” for realized niche accurately described as. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. A niche is the multidimensional set of abiotic conditions, resources, and biotic relationships under which a population can persist. The fundamental niche reflects physiological and resource limits, while the realized niche is modified by competitors, consumers, mutualists, and dispersal barriers. The remaining alternatives—“Conditions used without competition”, “Ideal conditions for survival”, “Hypothetical conditions only”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Niche differentiation reduces overlap by separating species along resource, space, or time axes. Such partitioning can stabilize coexistence when each species performs relatively better under the conditions it uses most strongly. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates.

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 13

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