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Tag Archives: selection

Evolution Animated

I just stumbled upon this cartoon for the first time today and I’m totally blown away. Sure, there are some things that could be explained better. There are a couple of moments when the illustrations could be a bit more accurate. But, overall, it’s a very good summary of the basic elements of evolution and pretty funny. (I wish I had made this!)

Have a watch and enjoy.

also, check out Kurzgesagt’s other animations on the Big Bang Theory, et al.

 
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Posted by on March 6, 2014 in Uncategorized

 

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The Question of Death

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Death’s Dance

In the film, Questioning Darwin, it is asked of ‘Darwinists’, “How does evolution deal with death?”

I have to admit, I don’t know what this question really means.  Is he asking why there is death? What happens after death?

Several people texted just this question during the live broadcast of the Nye / Ham debate and I didn’t understand it then either. In that context, they had posed this question as something of an experimental challenge to evolutionists and I interpreted it as meaning … ‘ Just wait until you die, heretic. Then you’ll see who’s right.’ Perhaps I had been to quick to this conclusion ?

If there is anyone out there who can explain just what this means, please let me know. Right now it’s nothing but an inside joke that I don’t get.

 
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Posted by on February 24, 2014 in Uncategorized

 

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RadioLab’s Inheritance Podcast

Screen Shot 2012-11-30 at 9.41.46 AMMy son and I just listened to a completely engrossing podcast on inheritance from RadioLab. The episode had three stories about different aspects of inheritance and genetic control. The first didn’t capture my interest nearly as much as the next two, so I won’t discuss it here.

The second story proposed and interesting idea of Lamarckean inheritance based on the extraordinary record-keeping of a far-north town in Sweden. In this town, the church kept amazingly detailed records about births, deaths, disease, health and even crop production year to year. When all these data were analyzed, researchers found a strong correlation between the availability of food to men in the village and the health and wellbeing of that man’s children. What might seem unintuitive is that contrary to what you might think, the children of men who suffered through years of starvation when they were ~9-12 years old fared the best. If dad ate well, your health prognosis was poor. If dad ate poorly, your prognosis was better. The effect even seemed to trace down two generations.

The explanation for this was that at this time in a man’s life he is making the cells that will go on to make sperm. Somehow, these cells can receive genetic imprinting that improves the fitness of the offspring.

Let me stop here. I have to say, I think this is entirely unconvincing. I can think of at least one simpler explanation for these data. Further, I can easily imagine how if it was possible to turn on these beneficial changes, evolution would make this the norm rather than the exception.

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Example data. A) Population lifespan following feast years, 100% survival. B) Population lifespan following famine years, 50% survival.

Consider a population of 100 kids in the target age group during a year of ‘feast.’ 100% of these kids survive and have children. These children have an average lifespan of 50yrs. Given the same group during a year of ‘famine.’ 50% of the kids survive and have children. The children live to an average age of 75 yrs. It appears that the famine during the elder generation improved the fitness of the younger.

But, if we examine the ‘feast’ population again, we might see that they can be broken up into two natural groups, one with a 75yr lifespan (the healthier 50%) and one with a 25yr lifespan (the less healthy). If the famine year selectively kills the weaker kids, then we are simply selecting our way to better health rather than causing it.

Because this is published research I expect that this simple answer was excluded somehow and I hope to find the original work to see that, but the burden of proof rests on the group proposing the more complex explanation.

I’ll see if I can research this a little and write again later, but I wanted to comment right away because I thought that it was an interesting example of how numbers can sometimes lead you astray if you’re not careful.

Oh, and very quickly, the last story…

The last story was about a woman who had adopted a baby girl, Destiny, from a mother who was addicted to drugs and couldn’t support the child. Amazingly, the next three years after that, the same mother gave birth to three more addicted babies that were all adopted by the same family. Because of her frustration about how this woman was so casually bringing more children into the world, one a year, each addicted to heroin et al. at the time of birth, the adoptive mother tried to pass a law to somehow prevent this from happening. When that failed, she worked directly to set up a fund to pay addicted women to undergo surgical sterilization or get long term birth control.

Many saw this as eugenics in action. Personally, I see no convincing connection to eugenics whatsoever based on the fact that the procedure was voluntary and based on a behavior rather than an innate characteristic of the women. Nevertheless, the conversation went places I never expected – mostly because I thought Jad and Robert would not get drawn into such ridiculous speculations and extensions of logic as they did. It was still good listening though.

I highly recommend checking out this episode.

 
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Posted by on November 30, 2012 in Uncategorized

 

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Cell Cycle and Cancer

Cell Cycle in intimately connected to cancer because, in essence, cancer is a disease of cell cycle dysregulation. The purpose of regulating the cell cycle is to maintain genomic integrity, therefore the checkpoints of cell cycle progression specifically interrogate the DNA’s suitability to replicate, to divide and to be assorted into new, ‘daughter’ cells.

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If a cell replicates DNA when there is damage to the DNA, then poor copies are perpetuated. If a cell commits to division when there is DNA damage, the same result might ensue – i.e. daughter cells may receive poor copies of the DNA. If a cell divides when chromosomes are not properly assorted then neither cell is healthy.

All three mechanisms have the same goal: ensure high fidelity copying.

With cell cycle checkpoints intact, cells can only pass when their DNA is in good condition or when chromosomes are being handled properly. The result is one healthy cell gives rise to two healthy cells. If a cell reaches a checkpoint and damage is detected, then the cell ‘arrests’ cycle progression for a short period of time. During this arrest, the cell has the opportunity to rescue the DNA and resume cycling. If this does not happen, then the cell is triggered to commit apoptosis –  cellular suicide. In this was, the cell gives its life for the good of the organism.

In this way, the cell is very analogous to a bee stinging an intruder. Although the bee will die now, it has contributed to the good of the colony in its sacrifice. After all, the worker bee cannot reproduce herself, her genetic heritage is intimately tied to the fate of the colony and its queen. Similarly, the cell dies to preserve the organism against what might be a harmful alteration / mutation. And, like the bee, this cell likely could not reproduce by itself anyway, it’s genetic heritage is tied to that of a larger body where only the gonads produce reproductive cells.

When cell cycle checkpoints are not functional, poor copies of DNA / cells get through. Furthermore, these cells are now inherently unstable because they have a compromised checkpoint, and additional errors may accumulate. Sometimes these errors disrupt other regulators of cell cycle, leading to a compounded problem. Over time, these cells may develop into cancerous cells.

The other point of cell cycle regulation is in the midst of mitosis, during metaphase. At this time, the cell has bound the chromosomes with spindle fibers that attempt to shorten and pull the chromosomes to a flat plane in the middle of the cell called the metaphase plate. The checkpoint here is to find out whether every single chromosome has attached to each side and each daughter cell will get the correct number. If this fails, cells will have incorrect distributions of the chromosomes and are unlikely to survive. Further, if these cells did survive, they would never be able to correct the error.

Here, the bee analogy would be too strained to continue, but it is not too difficult to see that when a cell disentangles itself from preserving the health of the body and instead looks only after its own short-sighted interests that these cells will grow and compete directly against the rest of the body for space and resources. Initially, when a tumor is small, this may have little consequence, but as a tumor becomes larger or more dispersed in the body, this selfishness can severely impact the larger organism, ironically (for the cancer cell) undermining even the tumor’s self interest.

 
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Posted by on October 14, 2012 in Education, Uncategorized

 

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