Conformers and regulators
Whether an organism works with its environment to keep its metabolism going, or works against the environment to do the same, determines whether its metabolism regulating approach, physiologically speaking, falls in the conformer or regulator category.
Conformers such as the largemouth bass do not invest as much energy into maintaining their metabolic environment (homeostasis), overarchingly governed by temperature regulation i.e. thermoregulation. They save this energy, but the downside is that their environmental niche is quite narrow. If they are to follow the right environment to maintain their metabolism, it’s likely they can’t go far and wide.
Regulators such as humans use energy for homeostasis, but have far greater freedom of location because the environment doesn’t dictate their ability to survive as much. Hence, their environmental niches open up and have a wider selection compared to conformers.
Environmental factors that contribute to their ability to survive include temperature, salinity and pH, and are called abiotic factors. Biotic factors would be competition and predation between organisms.
Negative feedback and thermoregulation
The operation of an oven is an easy example of negative feedback acting both ways, which is how it usually acts. That means that there are deviations in two opposing directions. If an oven is set at 220°C, both a decrease and an increase in temperature is a deviation. So if the temperature drops or rises, a sensor picks that up and commands the heater to turn on or off.
This is negative feedback because it returns the system to its original state.
Sometimes completely separate sensors control a rise or fall in temperature. This separation gives a high level of control.
Not all organisms maintain their body’s core temperature the same way. Some control it internally like we do. We’re endothermic. Reptiles for example are not. They’re ectothermic. Two pennies for who guesses how these fine specimens maintain their temperature. Do they:
A) Run for heat?
B) Shiver for heat?
C) Sit where the sun shines?
They sit where the sun shines, ladies and gentlemen, they just sit there until it gets too hot. And what do they do when it gets too hot? Well, funny you should ask. They move their scaly little selves to a shady place. Why didn’t our monkey-faced ancestors think of that? (They did, long story.)
Needless to say, a lot of ectothermic organisms live in extremely stable regions where temperature doesn’t fluctuate wildly.
Fun fact: that bit in the brain, the hypothalamus, is responsible for temperature homeostasis. Thermoreceptors pick up increases and decreases in optimal body temperature and send signals via nerves to effectors to act. This is what happens:
Sweat cools down the body by producing water that upon evaporation removes heat energy. Vasodilation is the dilation of blood vessels. It results in the distance between them and the skin shortening so that excess heat can dissipate quicker. Flat hairs ensure that no air is trapped close to the skin. Air is a poor heat conductor so effectively this removes any potential insulation.
No sweat occurs. Vasoconstriction has the opposite effect to vasodilation, as the vessels tighten up instead of dilate to prevent heat loss. Raised hairs create a layer of air trapped between hairs and skin, minimising heat loss to the environment. Shivering causes muscles to do work, thus releasing more heat. Hormones like adrenaline may be released to increase metabolism.
Why, though, is it so important to keep a strict temperature and pH? From a physiological viewpoint, think of enzyme activity. Its sensitivity to both temperature and pH means that the only conditions of optimal function will be strictly defined. Lots of enzymes denature past 40°C and are inactivated below 35°C.
Similarly, extreme pH is detrimental to optimal enzyme function, so blood pH must be tightly regulated.
Temperature affects all chemistry so that higher temperature increases kinetic energy of molecules and therefore their probability of interaction as they move more. This has an effect on one of the main movement types in cells – diffusion – as it allows fast enough propagation of chemicals to undergo reactions and support metabolic function.