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  2. Catabolism - Wikipedia

    en.wikipedia.org/wiki/Catabolism

    Released from alpha cells in the pancreas either when starving or when the body needs to generate additional energy; it stimulates the breakdown of glycogen in the liver to increase blood glucose levels; its effect is the opposite of insulin; glucagon and insulin are a part of a negative-feedback system that stabilizes blood glucose levels ...

  3. Attenuator (genetics) - Wikipedia

    en.wikipedia.org/wiki/Attenuator_(genetics)

    The hybridization of strands 1 and 2 to form the 1–2 structure prevents the formation of the 2–3 structure, while the formation of 2-3 prevents the formation of 3–4. The 3–4 structure is a transcription termination sequence, once it forms RNA polymerase will disassociate from the DNA and transcription of the structural genes of the ...

  4. Biological life cycle - Wikipedia

    en.wikipedia.org/wiki/Biological_life_cycle

    In biology, a biological life cycle (or just life cycle when the biological context is clear) is a series of stages of the life of an organism, that begins as a zygote, often in an egg, and concludes as an adult that reproduces, producing an offspring in the form of a new zygote which then itself goes through the same series of stages, the ...

  5. Insulin signal transduction pathway - Wikipedia

    en.wikipedia.org/wiki/Insulin_signal...

    Different enzymes control this pathway. Some of these enzymes constrict the pathway causing a negative feedback like the GSK-3 pathway. Other enzymes will push the pathway forward causing a positive feedback like the AKT and P70 enzymes. When insulin binds to its receptor, it activates the glycogen synthesis by inhibiting the enzymes that slow ...

  6. Stabilizing selection - Wikipedia

    en.wikipedia.org/wiki/Stabilizing_selection

    Stabilizing selection (not to be confused with negative or purifying selection [1] [2]) is a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value. This is thought to be the most common mechanism of action for natural selection because most traits do not appear to change drastically over time. [3]

  7. Phototropism - Wikipedia

    en.wikipedia.org/wiki/Phototropism

    In biology, phototropism is the growth of an organism in response to a light stimulus. Phototropism is most often observed in plants, but can also occur in other organisms such as fungi. The cells on the plant that are farthest from the light contain a hormone called auxin that reacts when phototropism occurs. This causes the plant to have ...

  8. Perceptual control theory - Wikipedia

    en.wikipedia.org/wiki/Perceptual_control_theory

    Perceptual control theory (PCT) is a model of behavior based on the properties of negative feedback control loops. A control loop maintains a sensed variable at or near a reference value by means of the effects of its outputs upon that variable, as mediated by physical properties of the environment.

  9. Density dependence - Wikipedia

    en.wikipedia.org/wiki/Density_dependence

    Parasite-induced vector mortality is a form of negative density-dependence. The Onchocerciasis life cycle involves transmission via a black fly vector. In this life-cycle, the life expectancy of the black fly vector decreases as the worm load ingested by the vector increases.