Math 151 - Fall 2015
References Discussed in Class
August 19, 2015: Intro to Statistics
Biosynthesis of monoterpene scent compounds in roses
by Jean-Louis Magnard et al.
Full paper as a PDF file - Science 349:81-83 (July 3, 2015)
Comments: This paper addreses the general issue of how breeding programs for certain flower traits in roses, such as color, has led to a loss of fragrance. This is a common complaint about cut flowers. Monoterpene alcohols are compounds that are important in floral scents and this paper focuses on the genetic control of the production of these compounds. Figure 2 in the paper is a good illustration of the use of the bar charts we discuss in Chapter 2 of the text, in this case to show data on how expression of a certain gene related to monoterpene production varies across different parts of a rose plant (leaves, sepals, petals, etc.) and how this varies as a flower develops.
August 24, 2015: Histograms
Whole-body endothermy in a mesopelagic fish, the opah, Lampris guttatus
by Nicholas C. Wegner, Owyn E. Snodgrass, Heidi Dewar, John R. Hyde
Full paper as a PDF file - Science 348:786-789 (May 15, 2015)
Comments: You have long heard about cold-blooded and warm-blooded organisms, with mammals such as humans having physiological mechanisms to maintain their body temperatures above ambient temperature. This paper provides data to show that the assumption that all fishes are cold-blooded is not correct. It has long been knowmn that a very small number of fishes are able to raise the temperature of some specific organs or tissues (called regional endothermy) - some tunas and sharks have this ability. This paper shows that a large fish, the opah, is able to maintain whole-body ectothermy through heat production arising from flapping of pectoral musculature during comntinuous swimming and this tissue is isolated from the water by a thick layer of fatty tissues. They describe the detailed physiology that allows this fish species to circulate warmed, oxygenated blood through its gills. They include histograms describing the differences between activity at different depths during day and night for the opah and for albacore tuna.
August 26, 2015: Allometric relations
Exceptionally low daily energy expenditure in the bamboo-eating giant panda
by Yonggang Nie et al.
Full paper as a PDF file - Science 349:171-174 (July 10, 2015)
Comments: Giant pandas eat a diet that is essentially only bamboo, and yet they have a digestive system that is not very efficient. They feed for very long time periods and do not move a great deal. This paper calculates the daily energy expenditure of giant pandas and compares this to a wide variety of other mammals. They find that there is not great deal of difference in daily energy expenditure of pandas in the fields as compared to those in captivity. These animals have almost 38% lower energy expenditure than similar sized mammals would be expected to have based on the allometric relationship between daily energy expenditure and body mass. They argue that no single factor allows giant pandas to survive on a bamboo diet, but that it is a mixture of morphological, physiological and behavioral traits that contribute. These include very low physical activity levels and reduced sizes of some high metabolism organs.
August 31, 2015: Log-log scatter plots
Variation in cancer risk among tissues can be explained by the number of stem cell divisions
by Cristian Tomasetti and Bert Vogelstein
Full paper as a PDF file - Science 347:78-81 (January 2, 2015)
Comments: It has long been known that there are quite different rates of cancer for different tissues in humans. While some of these differences arise clearly from environmental factors, such as the strong evidence that cigarette smoking leading to incraeses in lung cancer, many of the observed differences in lifetime risk of cancer between different tissues do not appear rto be strongly related to external environmental factors. The authors collected data from literature searches on total stem cell divisions over tissue lifespan and show that there is a very strong relkationship between this and lifetime risk of cancer in that tissue. They argue that about 65% of the differebnces in cancer risk between tissues can be explained by the total number of stem cell divisions in the tissues. That is, errors in DNA replication in tissues stem cells are stochatsic factors that impact the chance that a tumor develops. The more stem cell divisions, the higher the chance that cancer arises. They go on to group cancer tumors into two types depending upon the relative effect on cancer risk in different tissues of environmental and hereditary factors vs. cell division errors.
Description of analysis of Fig 1 log-log plot in this paper (September 9, 2015)
September 2, 2015: Log-scaling and scatter plots
The ecology of microscopic life in household dust
by Albert Barberán et al.
Full paper as a PDF file - Proc. Royal Soc. B 282:DOI: 10.1098/rspb.2015.1139 (August 26, 2015)
Comments: This is the first major analysis of the fungal and bacterial content of household dust taken across many houses. It provides a comparison of the fungal and bacterial communities inside 1200 houses across the US to those communities sampled outside the houses. It also analyzes the impact on these microbe communities of factors such as whether dogs or cats are present and the human female:male ratio. It presents maps of the US illustrating that regional factors, such as climate, affects these communities. Many of the data plots use log-scaling. Some basic conclusions are that the presence of either dogs or cats increases the density of many bacterial genera and that there are certain bacteria that are more prevalent in houses with more females than males and others more prevalent in houses with less females than males.
September 14, 2015: Log-log scaling and trophic analysis
The predator-prey power law: Biomass scaling across terrestrial and aquatic biomes
by Ian A. Hatton et al.
Full paper and introductory summary - Science 349,6252 - DOI: 10.1126/science.aac6284 (September 4, 2015)
Comments: There authors have collected published data from over 2000 mammal, invertebrate, plant and plankton communities and investigated the relationship between predator biomass (measured as kg of predators per square kilometer) and prey biomass. They found a very strong power-law relationship between these variables that was present across a vast array of different natural systems. They also analyzed the relationship between individual body mass and maximum individual production (measured as mass growth and offspring production per year) and found a strong power-law that held across many taxa. Analyzing data from a large number of different protected areas in African savannas, they again found a very strong power law relationship. They discuss the potential problems with using the standard least squares method to find linear regressions.
Return to Math151 Home Page
Return to L. Gross Home Page <