Population Life Tables

A life table is a record of survival and reproductive rates in a population, broken out by age, size, or developmental stage (e.g., egg, hatchling, juvenile, adult). Ecologists and demographers (scientists who study human population dynamics) have found life tables useful in understanding patterns and causes of mortality, predicting the future growth or decline of populations, and managing populations of endangered species. Types of life tables include:

• Age-specific, Cohort, or Dynamic life tables: data are collected by following a cohort throughout life. This is rarely possible with natural populations of animals. 
• Static or time-specific tables: age-distribution data are collected from a cross-section of the population at one particular time or during a short segment of time, such as through mortality data.
• Composite tables: data are gathered over a number of years and generations using cohort or time-specific techniques. This method allows the natural variability in rates of survival to be monitored and assessed. 

So, why do we care about life tables? The main value of a life table lies in what it tells us about the population's strategy for survival. So, life tables help us to understand the dynamics of populations. For example, time-specific life tables are valuable to a manager of exploited populations because they show the existence of strong year classes or help identify weak age classes.

Here is an example of a population life table for a Darwin finch: 

Life table for one Darwin finch, the Galapagos cactus finch (Geospiza scandens)*
age class** (x)	probability of surviving to age x  (lx)	average number of fledgling daughters (mx)	product of survival and reproduction (Σlxmx)
0	1.0	0.0	0.0
1	0.512	0.364	0.186
2	0.279	0.187	0.052
3	0.279	1.438	0.401
4	0.209	0.833	0.174
5	0.209	0.500	0.104
6	0.209	0.833	0.174
7	0.209	0.250	0.052
8	0.209	3.333	0.696
9	0.139	0.125	0.017
10	0.070	0.0	0.0
11	0.070	0.0	0.0
12	0.070	3.500	0.245
13	0	—	—
			R0 = 2.101
Net reproductive rate = R0 = Σlxmx = 2.101 Mean generation time = T = (Σxlxmx)/(R0) = 6.08 years Intrinsic rate of natural increase of the population = r = approximately 1nR0 / T = 2.101/6.08 = 0.346

Biodiesel and Bioethanol in the Making

In lab 10, we focused on making biodiesel and bioethanol.. pretty cool! So, for my blog assignment, I decided to do some deeper digging about the two biofuels. 

• Biodiesel: is a renewable, cleaner-burning biofuel that is primarily produced from a chemical reaction of alcohol (usually methanol) and a range of fats that include vegetable or animal oils and plant extracts like corn, sunflowers, soybeans, canola, etc. This reaction gets rid of the by-product glycerin which is not suitable for the engines through a refinery process called "transesterification". During the transesterification process, other byproducts like methyl esters are also left behind. Biodiesel is then free from sulfur and aromatics which are contained in regular fuels that will facilitate in the reduction of harmful emissions from diesel engines. Biodiesel is non-hazardous, simple, renewable, sustainable, nonflammable, affordable and cleaner!
• Bioethanol: is an alcohol fuel derived from sugars found in crops such as rice, potato skins and sugarcane and it is commonly made from corn, sorghum and wheat. Corn is commonly the base material in the United States because it is affordable and available. But in Brazil, sugarcane is widely used. Since it is produced from plants, it is biodegradable and renewable. It is a clear, colorless alternative alcohol. So, how do we make it? The fermentation of sugars and starch in corn with the use of yeast is the most frequently method used. From starch, it is fermented into sugar, afterwards it is fermented again into alcohol. The dry mill method seems to be the most popular making method! 
• For instructions on making biodiesel and bioethanol one can visit http://journeytoforever.org/ethanol.html for more info!

Mitochondrial Eve

We hear lots about "Mitochondrial Eve" but what does that term exactly refer to? Is Mitochondrial Eve an actual woman? I found this blog assignment to be possibly the most intriguing I have researched all semester! Mitochondrial Eve refers to matrilineal "MRCA" (most recent common ancestor) in the study of human genetics. Basically, this "Eve" was the woman from whom all living humans descended from their mother's side, through the mother's of mother's and so on. Mitochondrial Eve is the female counterpart of Y-chromosonal Adam, the patrilinial MRCA- even though the two lived thousands of years apart. Each ancestor of people now living in the line back to the matrilineal MRCA had sisters, female cousins, etc. and some of these females may have descendants living now. But none of the female contemporaries of the "Mitochondrial Eve" has descendants living now in an unbroken female line. Mitochondrial Eve is thought to have lived around 200,000 years ago in East Africa. 

There are a few misconceptions that are widely believed about Eve that include:

• That Eve was a contemporary of Adam: Not true! It is thought that Eve lived BEFORE Adam.. perhaps 50,000-80,000 years earlier. 
• She was the only woman: One of the misconceptions of mitochondrial Eve is that since all women alive today descended in a unbroken female line from her that she was the only woman alive at the time. There may have been many other women alive at Eve's time with descendants alive today, but sometime in the past, those lines of descent included at least one male, who do not pass on their mother's mitochondrial DNA, thereby breaking the line of descent.
• She is the MCRA shared by all humans: Mitochondrial Eve is the most recent common matrilineal ancestor, not the most recent common ancestor. 

Amphioxus (The Lancelets)

Amphioxus or also known as "the lancelets" and are representatives from the subphylum Cephalochordata. They can be found buried in sand in shallow parts of temperate or tropical seas. In parts of Asia, they are produced as food for humans and domesticated animals. So the question is, why should we study these lancelets?! Because they provide us with indications about the origin of vertebrates! Lancelets serve as a interesting point of how vertebrates have evolved and adapted over time. Although lancelets split from vertebrates more than 520 million years ago, their genomes hold clues about evolution and how vertebrates have employed old genes for new functions!

Macon Dog Park- Ruff ruff!!

The Macon Dog Park is a safe, natural environment where dogs and their owners can run and play without leashes! The purpose of the park is to promote responsible dog ownership by providing a beautiful, well-maintained greenspace where pets and people can enjoy a healthy, active lifestyle. MDP is located conveniently near Mercer University Campus- It is one block north of Tatnall Square at the corner of Chestnut and Adams Street. 
I think that Macon Dog Park is a wonderful amenity for the Bibb County area. It allows for leisure, neighborhood fellowship, and a safe haven for man and his best friend! I'm not particularly a dog person myself, BUT if I had one- I would definitely take him/her to MDP! For more information about hours, rules and regulations, etc. you can visit http://www.macondogpark.org/

Darwin's Dilemma

Charles Darwin was an English naturalist who firmly believed that all species of life have descended over time from common ancestry. He proposed his scientific theory that this branching pattern of what is known as evolution resulted from a process known as natural selection. Darwin composed his thoughts along with solid evidence in his work, On the Origin of Species. His book became widely accepted as did the principle of evolution. However, in 1886 in Canada, Charles Walcott discovered the fossils of the Burgess Shale. the Burgess fossils were largely regarded as evidence that the familiar phyla of animals appeared very rapidly in the Early Cambrian, in what is often called the Cambrian explosion. This view was already known to Darwin, who regarded it as one of the greatest difficulties for the theory of evolution- we call this "Darwin's Dilemma." Darwin hoped that as time moved along, more evidence would come forth that supported his theory. However, with more and more fossil discoveries in the past 150 years, Darwin's theory has become more aggravated that resolved. 

Hitchiti Lab

http://www.srs.fs.usda.gov/compass/issue13/05hitchiti.html