Monday, 11 June 2012

Biology stuff for the week 4-10/6/12

[video] Diane Kelly: What we didn't know about penis anatomy

[video] For several thousand years, horses have been bred by humans. Today, 95% of Thoroughbreds are descended from the same horse - Eclipse - and many of the medical conditions they suffer are caused by inbreeding.
Using DNA, archives, and even paintings of horses, the ancestry of particular horses such as Bend Or have been identified.

It seems that the evolution of reptiles into birds caused the demise of dinner-plate sized insects.
Like modern fishers, they selected in favour of smaller insects, which were more agile, more difficult to catch, and less worth catching.
So despite increasing atmospheric oxygen concentrations, which would have favoured larger insects, recorded maximum sizes actually decreased.

It seems hormones from farmed animals leach into the environment, potentially effecting surrounding wildlife that, due to their common ancestry, are responsive to those same hormones.
Whether this pollution marks a significant difference since domestication is matter for further investigation. What are the consequences really going to be?

New, more objective assessments of animal weight, formulated by biologists at the University of Manchester, have found that present estimates for dinosaurs are consistently too high.
Brachiosaurusm, for example, famous for being the "veggiesaurus" in Jurassic Park, was previously estimated at 80 tonnes. This new metric estimates a lighter 23 tonnes - far more manageable, physiologically speaking.

Homo Sapiens might have survived its heidelbergensis, cro magnon, and neanderthalensis cousins simply by having thinner builds, which are easier to sustain in food-poor environments, and better for running.

OK, listen up -- i'm including this article, not because i think it's true, but because i think it'll get completely misunderstood by the popular press, so this is a kind of "heads up"
What this story is about, is an experiment that found chilli plants growing faster when closed away in boxes than when exposed to sweet fennel, which is known to emit growth-suppressing chemicals.
Chillis exposed to sweet fennel germinated at the same rate as controls that weren't light blocked, chillis blocked from the fennel by smell but not light germinated faster than control, chillis blocked by smell and light germinated faster than control but slower than those blocked also by light, and the controls blocked by light germinated slowest of all.
Clearly, the central box must have cast a shadow, causing the light-blocked controls and light-blocked fennel-masked chillis to germinate slower. If the sweet fennel was really suppressing chilli growth, i would have expected the chillis exposed to the fennel to germinate slower than the equivalent controls. They did not - they germinated at the same speed. Blocking fennel did correlate with accelerated germination, however.
This is a curious result which must be further explored. The result could easily fade away in negative results, so it would not be wise to report "Plants can hear". D'ya hear? ;)

Arsenic, at conentrations currently considered safe, have been observed to inhibit the uptake of nutrients, and thereby growth, in offspring.
At 10 ppb (parts per billion), arsenic does not transfer to offspring through the mother's milk, but its effects clearly do - pups of mice fed water with arsenic at 10 ppb grow slower than the norm.
There are many other chemicals that are safe most of the time, but are dangerous during pregnancy.
Many medications have somethiong along the lines of "If you are pregnant or breastfeeding you should only take this medicine if your doctor has specifically recommended it" written in their info notes. Paracetomol, for example.

More evidence of horizontal gene transfer in complex eukaryotes. In this instance, parasitic plants.
I've added this link to my article on genetic modification:

'Channeling our ion past'
How do our cells work? On the cellular scale, they are nothing but chemical pumps, pumping ions across their boundaries (cell membranes) via active transport.
It is this pumping of ions that makes us classifiable as alive (MRS GREN - movement, respiration, sensitivity, growth, reproduction, excretion, nutrition - all contingent on ion flow). In a simplistic sense, it *is* life.
The CatSper2 protein in spermatozoa, for example, activates when the sperm experiences a high progesterone gradient and a drop in pH.
Basically, when the sperm gets close to the ovum, the race is on! The sperm massively increases in activity, as a kind of dive for the line. This involves an opening of the CatSper channel which releases Ca2+ ions
Now, ions are all charged, so, in a very real sense, our cells work by chemoelectricity - we are electric organisms!
But how do the ions get 'there' so that they can flow over 'there'?
Active transport. They are pushed up an energy gradient, into a position from where they will release their energy later on.
This is where the physics comes in -- to make an object move from a region of lower energy potential, to a region of higher energy potential, work has to be done (energy has to be put into the system)
Analogical examples: mechanical work to move a book from the bottom shelf to the top shelf; electrical work to pump heat out of fridges/freezers; mechanical work to accelerate a tennis ball from static to 150 kph; chemical energy (on a gas hob) to heat a pan of water from RT to 99C; solar energy to excite an electron into a higher energy state, for it to drop again and release a photon revealing the colour of the incident object.
For any process to occur in the human body (or the body of any other cellular organism, for that matter), work first has to be done, either within the cell, within the body but by other cells, or stolen from other bodies (think of food chains).
Due to the second law of thermodynamics, the energy needed to increase energy potentials, in order for them to fall again, is always greater than the energy let out when they do fall. This is why the third law of thermodynamics holds: overall entropy always increases.
If localised decreases in entropy never happened, we would not be here, because no chemoelectrical organism could have developed in the first place!
We are all, in the simplest sense, energy pumps, channeling energy from our sun. Whether we are in the form of 100m sauropods, or monocellular bacteria.

A brief history of human evolution
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