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The African Wild Dog
Thermal Relations
Homeostasis is the body’s attempt to regulate a constant and balanced internal environment to maintain a stable equilibrium, which requires persistent monitoring and adjustments as conditions change.
Homeostatic regulation is monitored and adjusted by the receptor, the command center, and the effector (i.e. muscle, organ, etc. that can respond to a stimulus from a nerve). The receptor receives information based on the internal environment; the command center receives and processes the information; and the effector responds to the command center, opposing or enhancing the stimulus.
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To recollect, controlled variables in a system are the components kept rather constant at a set point by the system. In any control system, the controlled variable is the property that is being kept constant or relatively constant by the system’s activities. The constant set point is the level at which the controlled variable is to be kept.
When a system uses data on the controlled variable in a manner of governing itself, that is known as feedback.
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Feedback occurs if the system uses information on the controlled variable itself to govern its actions.
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When a system responds to changes in the controlled variable by sustaining it at the constant set point, that is known as negative feedback.
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When a system establishes differences in the controlled variable away from the constant set point, that is known as positive feedback.
In physiological systems, negative feedback is much more common than positive feedback and occurs in all systems of homeostasis.
Homeostasis
The African wild dogs are considered homeotherms, in which they are endothermic thermoregulators. Endothermy is a synapomorphy of Mammalia, where evidence shows historical relationships and their associated hierarchical structure. Thermoregulation occurs by physiological means and is the difference in body temperature of an individual, whether it be from two different points in time (temporal) or between separate areas in the body (spatial). Homeotherms maintain a constant internal body temperature, within a narrow range of varying temperatures. Endothermy can provide animals with distinct advantages. Endothermic animals warm their tissues through the production of metabolic heat.
Essentially, homeotherms regulate internal temperatures through physiological means rather than by behavior. The dogs are able to thermoregulate their body temperatures by adjusting how rapidly metabolic heat is produced and retained via endothermy.
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In an observation comparing different classes of animals, it is believed that a significant step in mammalian (and avian) evolution was the divergence of endothermy. Non-avian reptiles don’t have the capability to warm their bodies by producing metabolic heat. Mammals and birds are capable of endogenous, internal regulation of body warmth due to endothermy. Along with their physiological processes, they can regulate a rather constant tissue temperature over exceedingly wide ranges of environmental conditions.
FIGURE
Conformity and regulation These examples from the study of temperature illustrate the general principles of (A) conformity: animal permits internal and external conditions to be equal, and (B) regulation: animal maintains internal constancy in the face of external variability.
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Temperatue Regulation:
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​disadvantage: it is energetically costly
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advantage: animals benefit by permitting cells to function in steady conditions, independent of variations in external conditions
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​Temperature Conformity:
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disadvantage: cells within the body are subject to changes in their conditions when outside conditions change
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advantage: it is energetically cheap and avoids the energy costs of keeping the internal and external environment separate
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Homeotherms maintain a constant internal body temperature, with a small window of temperature fluctuations. When homeostasis is maintained, the body aims to keep the internal temperature at equilibrium.
Regulation of homeostasis is monitored and tailored by a receptor, command center, and an effector. It accomplishes this by the following:
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Receptor: receives stimulus information from the internal environment
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Command center: takes and processes the information
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Effector: a muscle, organ, etc. that responds to input from command center, where it then gives feedback in response to the stimulus
This process carries on in order to restore and regulate homeostasis.
Figure.
Animals fall into four categories of thermal relations based on whether they display endothermy and whether they display thermoregulation
African wild dogs have evolutionary adaptations that tolerate or dissipate heat generated by fast running, along with morphological adaptations (i.e. long, slender limbs to run fast; large, vascularized ears to cool off).
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The dogs have distinct nasal glands which contribute moisture for evaporative cooling while panting, which is the primary means of heat loss in canids. Canids only have sweat glands in their footpads, which doesn’t contribute much to releasing heat. Their fur (known as pelage) is controlled by cutaneous muscles which play a big role in thermoregulation. Molting may occur when seasonal climates change by extremes, where the dogs lose their fur over time and it eventually doesn’t grow back.
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Larger canids, like the African wild dog, have adapted their bodies for their life on the run. They’ve developed significant aerobic and anaerobic abilities suited for thermoregulation and high-speed runs over the course of long distances in the pursuit of prey.
Thermal regulation
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