Please enable JavaScript.
Coggle requires JavaScript to display documents.
The Effect of Increased Lifespan in Mammals on their Mass-Specific Basal…
The Effect of Increased Lifespan in Mammals on their Mass-Specific Basal Metabolic Rate
Discussion
Key Findings
The data supports the original hypothesis. The lifespan and mass-specific BMR in mammals display a negative exponential relationship.
Secondary Findings
Limitations
: There were only 167 mammalian species available for examination for mass, BMR, and lifespan.
Other findings
: Birds displayed a negative linear relationship between lifespan and mass-specific BMR.
Previous Studies
In a previous study conducted in 2005, researchers found that mass-specific resting metabolic rate (RMR) scaled with an exponent between -0.2 and -0.33 (Speakman 2005)
Significance
Metabolism is affected by numerous factors and plays a role in the bodies of every organism on Earth. Greater knowledge about these processes can shed light on increasing lifespan for humans and other species.
Next Steps
Further research into the relationships between lifespan and mass-specific BMR should involve significantly more data in order to analyze if a pattern emerges across many species.
Introduction
Background
Metabolism, much like everything else, has evolved through time from species to species. For example, mammals, who are endothermic, experience higher standard metabolic rates than reptiles, who are exothermic (Brand et al. 1991).
Unknown/ Problem
How does lifespan affect a mammal's metabolic rates?
In what ways can we alter metabolism in order for humans to live longer?
Question & Hypothesis
Does lifespan affect mass-specific BMR?
Hypothesis
: If mammals have a longer lifespan, then their mass-specific BMR will be lower than mammals with a shorter lifespan.
As mammals live longer, their activity levels decrease with age, therefore leaving them in a basal metabolic state for greater lengths of time, ultimately affecting their average BMR, and mass specific BMR. I predict that my hypothesis will be supported by the data.
Approach
To determine whether or not there is a relationship between lifespan and mass-specific BMR in mammals, data will be analyzed in order to see if any correlations exist.
Abstract
Background
Average mass and average basal metabolic rate (BMR) in mammals show a positive linear relationship, in which, as mass increases, so does the BMR.
Hypothesis
: If mammals have a longer lifespan, then their mass-specific BMR will be lower than mammals with a shorter lifespan.
Basal metabolic rate can be understood as the rate of energy expenditure per unit of time by endothermic animals at rest.
Methods
Animal diversity data was extracted from the University of Michigan Museum of Zoology for data sets of over 200 mammals
This data was then analyzed using excel to produce graphs and statistics
Results
Due to the t-Stat value being significantly greater than the critical value, the null hypothesis was rejected (14.31>1.97). Mass-specific BMR and average lifespan in mammals displayed a negative nonlinear relationship (slope 0.0055e-0.07x).
Methods
Design
Dependent variable
: mammal mass-specific BMR
Independent variable
: mammal lifespan
Subjects
Data values of mass, BMR, and mass-specific BMR were examined from 296 mammal species. When analyzing mammal lifespan data sets, 167 species were used. Additionally, data sets were based on an average of males and females within each species.
Procedures
Data values were put into excel, separated by individual columns. In order to calculate mass-specific BMR, BMR was divided by mass for each species. A scatter-plot was then composed comparing average lifespan and mass-specific BMR for the 167 mammalian species. Finally, a two-sample (assuming unequal variances) t-test statistical analysis was performed on the data expressed in the scatter-plot.
Results
Due to the t-Stat value being significantly greater than the critical value, the null hypothesis was rejected (14.31>1.97). Mass-specific BMR and average lifespan in mammals displayed a negative nonlinear relationship (slope 0.0055e-0.07x). The greatest mass-specific BMR value was seen in mammals with a life span ranging from 0-5 years, and the lowest mass-specific BMR values were seen in mammals with a greater life span than 5 years.
Literature Cited
Brand MD, Couture P, Else PL, Withers KW, and Hulbert AJ. 1991. Evolution of energy metabolism. Proton permeability of the inner membrane of liver mitochondria is greater in a mammal than in a reptile.
The Biochemical Journal
275 (1): 81–86.
https://portlandpress.com/biochemj/article-abstract/275/1/81/26960
. Accessed 2020 Feb 19.
Glazier DS. 2008. Effects of metabolic level on the body size scaling of metabolic rate in birds and mammals.
Proceedings: Biological Sciences
275(1641): 1405-1410.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2602708/
. Accessed 2020 Jan 29.
Speakman JR. 2005. Review: body size, energy metabolism and lifespan.
The Journal of Experimental Biology
208(9): 1717-1730.
https://jeb.biologists.org/content/208/9/1717
. Accessed 2020 Jan 29.
