Homeostasis is the tendency of the body to seek and maintain equilibrium, a state of balance, within its internal environment. Endotherms are “warm blooded” animals that produce and maintain their own internal body heat. Most mammals and a few birds, are endotherms; this is beneficial because the enzymes in the body that carry out metabolic processes have an optimum temperature at which they function, having the body constantly be, or be close to, this optimum internal temperature means life processes never have to cease.
The opposite of endotherms are ectotherms, animals such as reptiles and amphibians who do not regulate their own internal temperature and are ordinarily considered “cold blooded” because they do not produce their own body heat, although their blood can be warm due to external conditions. Instead of the physiological corrective methods that endotherms have due to negative feedback, ectotherms rely on behavioural adaptations like laying in the sunshine to warm themselves and burrowing into the ground or lying in the shade to cool down.
They also have an optimum temperature at which their enzymes function, and while they do not have to thermoregulate, their metabolic rate slows or ceases when they are out of the optimum range of temperature. They also are, unlike endotherms, lacking in stamina because they cannot regenerate their energy as quickly as homeothermic endotherms can. Endotherms, such as penguins, are able to thermoregulate without knowing, as the physiological processes happen automatically.
Furthermore, they are able to use behavioural adaptations as well to aid them in surviving comfortably in their icy habitat. temperatures vary with latitude, elevation, and distance from the ocean. Emperor penguins: Emperor penguins (Aptenodytes forsteri) are the largest and heaviest of the penguin species, being found living only on the continent of Antarctica. They live constantly on the ice during the summer, swimming and fishing around the edges, however, during the mating season in winter, they migrate inland to breed.
After the females have laid their eggs they return to the sea, having lost more than a third of their body weight built up over the summer period by creating the egg, they need to feed soon or they will starve and die. However, the journey home is longer than the one to the breeding grounds as new winter ice has formed around the edges, forcing them to walk miles more to reach the sea. The males are left behind to incubate the eggs, they too have eaten much over the summer months and use these fat reserves to sustain them during the harsh winter period of over 3 months.
The egg is tucked between the male’s’ legs, up beneath the layers of soft, insulating, feathers and a flap of warm skin designed to protect and warm the egg, it is also rested on their feet to keep it off the ice. In both cooler and warmer temperatures, for example winter and summer, even small variations away from the ‘normal can lead to the emperor penguin suffering hypothermia or hyperthermia. To prevent this, the emperor penguin has to regulate its internal temperature via both physiological responses in a negative feedback loop and behavioural responses to the external temperature change.
The components of a normal homeostatic system: Emperor penguins are endothermic homeotherms, meaning that they are able to physiologically thermoregulate; a process that allows their bodies to monitor and adjust their core internal temperature, to return them to their ‘set point’ or normal of around 39 degrees Celsius. When their external environment changes or they exert great amounts of energy (heating themselves up), thermoregulation takes place through a negative feedback loop.
Negative feedback is the body’s corrective mechanism in which a ‘stimulus’ causes an internal reaction to counter the effect of the stimuli and maintain an ideal, the set point. Firstly, changes in external temperature, ‘stimuli’, are detected by temperature sensors such as ‘receptors’ in the skin, which then transmit the data via nerve impulses to the central nervous system, the hypothalamus, in the brain (‘control system’). The hypothalamus will then coordinate a response, working in conjunction with the pituitary gland which produces hormones that initiate corrective responses, the ‘effectors’.
These hormones cause vasodilation of the capillaries, directing the blood to the more exposed areas of skin of the body and fluttering of feathers when hot. When cold, they cause feather raising/puffing and vasoconstriction of the capillaries. Each component of the ‘normal homeostatic system’ in emperor penguins, stimuli, receptors, control system and effectors, link in together to return the body to the internal temperature of around 39 degrees Celsius (norm. is reached); thus completing the negative feedback loop and preventing the body going into a state of hypothermia or hyperthermia.
Extreme cold environments: Hypothermia occurs when the core internal temperature of the body drops due to external stimuli and cannot be re-established via internal physiological thermoregulation processes. When the body temperature is lowered, the metabolic rate (the rate at which all life processes are carried out) slows and movement is restricted. This eventually can lead to death if behavioural methods are not engaged to re-warm the body. When in the winter period of Antarctica temperatures can drop as far down s -80 degrees Celsius, during which time the emperor penguins have to maintain their steady internal temperature of 39 degrees celsius as well as the males having an egg each to keep warm. This winter period is when the emperor penguins are at their most vulnerable towards the cold, the female penguins, after laying the eggs, journey back to the sea to fish and leave the males to incubate their eggs. Moving inland protects them and their eggs or hatchlings from the unstable edge ice, and moreover protects them from predators such as leopard seals that could easily pick off the young penguins.
This is a behavioural adaptation that ensures the survival of the penguins and their offspring. To prevent their bodies going into hypothermia, corrective responses; both physiological and behavioural, are initiated in these colder temperatures. The physiological responses include the puffing out of feathers which allows a layer of air to be trapped and warmed close to the skin, creating insulation; vasoconstriction, the thinning of the capillaries (reducing surface area) prevents a lot of blood flowing under the skin and becoming cool.
Instead the blood is kept closer to the core of the body, to protect the organs and retain as much heat as possible; and countercurrent blood flow. Furthermore, the dark coloured feathers on the emperor penguins’ backs allows for some heat from the sun to be absorbed and they have blubber, a large amount of fat on their body to aid in retaining heat. Behavioural responses to the cold include huddling together and all facing their backs to the sunshine; this is applied greatly during winter where hundreds of emperor penguins can be found huddled together, particularly the males incubating their eggs, in inland breeding colonies.
Moreover, this method is so effective at warming the penguins that the ones in the middle of the group can often become too hot and so will switch places with those on the edges of the group where they are more exposed to the cold. Extreme heat environments: Hyperthermia occurs when an uncontrolled increase in internal temperature exceeds the body’s ability to lose heat. This occurs when the external temperature is very hot, either from physical exertion or over exposure to natural heat.
Summer in Antarctica reaches temperatures of up to 15 degrees Celsius, however most of the time remains below 0 degrees Celsius. As the heat increases, the metabolic rate of the individual also increases, meaning the body will need more energy, ie. food, and liquid to maintain this faster rate of metabolism. This explains why during the summer emperor penguins live on the edges of the ice, diving for fish. However, if the temperature continues to rise, the body’s cells cannot function and enzymes carrying out life processes denature, ceasing metabolic activity.
The individual will soon after die if the internal body temp is not reduced. To counter high temperatures and prevent themselves from suffering hyperthermia, emperor penguins have varying methods of reducing their internal body temperature. These methods include physiological responses such as gular fluttering, the fluttering of the throat to stimulate panting, which allows cool air to enter the lungs and cool them and the blood surrounding, as well as expelling warm air to give off heat.
Vasodilation is another physiological response that allows a penguin to lose heat; the capillaries near the skin expand (dilate), increasing surface area, and warm blood is focused to the more exposed areas like around the mouth and the throat, or the feet. This allows heat to be lost to the surrounding environment and cools the blood. Countercurrent blood flow is also used to cool the blood this way, rather than warming it, as previously explained, heat is exchanged to the blood going to the skin, ie. he feet, and is lost into the ice or to the cool air this way. To reduce internal temperatures, emperor penguins also apply behavioural methods in cooling themselves, such as swimming – being surrounded by cool water is the fastest way the body can lose heat as it is incredibly effective at conducting it away from the body. They can also shiver, opening the layers of their feathers to allow cool air to pass through, as ventilation. As they do this, they also hold out their flippers, increasing surface area for heat to be lost. Conclusion:
As homeotherms, animals that maintain a steady internal temperature, emperor penguins are able to occupy a large ecological niche. This is because their enzymes that carry out metabolic processes have an optimum functioning temperature which they are able to internally maintain constantly through homeostasis and the process of negative feedback. They are among the few creatures that occupy the harsh, dry, continent of Antarctica and are able to survive there because of the effectiveness with which their bodies carry out homeostatic processes.
During both the winter and summer periods of Antarctica where the temperature can change drastically between its extremes of -80 to 15 degrees Celsius, the emperor penguins apply both physiological and behavioural responses to temperature changes that allow them to thermoregulate, and prevent themselves suffering from either hypothermia (becoming too cold to function internally) or hyperthermia (becoming too hot to function internally).
Each component of a normal homeostatic system; the stimulus, receptors, control system and effectors trigger and lead into each other creating a negative feedback loop which returns the body’s internal temperature to its normal, the set point.
