Relationship between basal metabolic rate and body size comparison

Metabolic rate (article) | Khan Academy

relationship between basal metabolic rate and body size comparison

Body size and metabolic rate both fundamentally constrain how species interact .. the resting metabolic rate was taken as the fitted line of oxygen consumption with .. We found no significance difference between the residuals representing . The relationship between mammalian basal metabolic rate (BMR, ml of O2 per h) . Relationship between body mass (M, g) and body temperature (Tb, °C) for an established benchmark for comparing metabolic intensity between species. The difference between and is not large but the law suggests that the Figure 2: Histograms of resting metabolic rates normalized to wet weight.

relationship between basal metabolic rate and body size comparison

According to our assumption above, the energy is removed through the surface at a constant rate, and thus the total energy produced should be proportional to A, i. Does this simple scaling result based on simple considerations of energy transfer also hold for biological systems? The resting energy demand of organisms has recently been compared among more than different organisms spanning over 20 orders of magnitude in mass!

In contrast to the Kleiber law prediction, this recent work found a relatively small range of variation with the vast majority of organisms having power requirements lying between 0. Further evidence for breaking of Kleiber scaling was provided recently for protists and prokaryotes J.

Body size, energy metabolism and lifespan.

The metabolic rate of an organism is condition dependent, and thus should be strictly defined if one wants to make an honest comparison across organisms. The most extreme example we are aware of is that bees in flight increase their oxygen consumption and thus their energy consumption by about fold in comparison to resting conditions BNID Similarly, humans taking part in the strenuous Tour de France consume close to 10, kcal a day, about five times the normal resting value.

relationship between basal metabolic rate and body size comparison

It is most common to refer to the resting metabolic rate, which operationally means the animal is not especially active but well fed. As the alert reader can imagine, it is not easy to ensure rest for all animals, think of an orca killer whale as one example. The values themselves are often calculated from the energy consumption rate that is roughly equal to the energy production rate, or in other cases from the oxygen consumption. A famous illustration representing this relationship is shown in Figure 1.

The difference between Moreover, maximum lifespan is not a good marker of ageing and RMR is not a good measure of total energy metabolism.


Analysis of residual lifespan against residual RMR reveals no significant relationship. However, this is still based on RMR. A novel comparison using daily energy expenditure DEErather than BMR, suggests that lifetime expenditure of energy per gram of tissue is NOT independent of body mass, and that tissue in smaller animals expends more energy before expiring than tissue in larger animals.

Some of the residual variation in this relationship in mammals is explained by ambient temperature.

Metabolic rate

In addition there is a significant negative relationship between residual lifespan and residual daily energy expenditure in mammals. A potentially much better model to explore the links of body size, metabolism and ageing is to examine the intraspecific links. These studies have generated some data that support the original rate of living theory and other data that conflict.

relationship between basal metabolic rate and body size comparison

In particular several studies have shown that manipulating animals to expend more or less energy generate the expected effects on lifespan particularly when the subjects are ectotherms. However, smaller individuals with higher rates of metabolism live longer than their slower, larger conspecifics.

relationship between basal metabolic rate and body size comparison

An addition to these confused observations has been the recent suggestion that under some circumstances we might expect mitochondria to produce fewer free radicals when metabolism is higher--particularly when they are uncoupled. These new ideas concerning the manner in which mitochondria generate free radicals as a function of metabolism shed some light on the complexity of observations linking body size, metabolism and lifespan.