Sunday, 15 July 2012

Biology stuff from the week 9-15/7/12

Say Goodbye To All The Bananas
I've already written a mini-essay on the merits of GM, which should be referred to as GE (genetic engineering), and it seems it will be necessary in this case.
Bananas have become so inbred, that they are treading the boundary of extinction!
"It has been kept in evolutionary limbo for so long that it is losing the battle against against fast-mutating threats. In fact, half of the world's edible bananas are derived from a single variety called Cavendish."
"Up to 50 pesticide treatments a year are required in large plantations against black leaf streak disease, a recent pandemy caused by Mycosphaerella fijiensis."
"In the 1950s, the prevailing commercial variety of the time, Gros Michel, was wiped out by Panama disease. It was replaced on farms by Cavendish, a southern Chinese variety that at the time was resistant to the fungus."
Cross-breeding between the sterile varieties is impossible, so to transplant genes will require genetic engineering.
If Gros Michel can go extinct, so can Cavendish; and every time a variety goes, the remaining gene pool shrinks.

It's known that sensory deprivation in one sense leads to brain remoulding, leading to an increase in sensitivity with other senses.
People born deaf have noticeably better peripheral vision and movement detection. This study finds that they also have superior touch sensitivity.
The blurry nature of brain activity means that sensory inputs can overlap, leading to phenomenon like where hearing people see two flashes when perceived simultaneous with two bleeps; and vice versa. Deaf people are found to perceive two flashes, when subject to only one, but simultaneous with two puffs of air applied to the top of the cheek.

Cows, it seems, produce less milk when the climate starts hotting up. It's already known that plants decline in productivity when overheated - this research simply extends the knowledge base to animals.

Salmon are also changing with warming temperatures - they are evolving to spawn earlier in the year.
"Because genetic samples of the fish have been taken on a regular basis since the 1970’s, the team was able to see that the late spawning marker showed a decrease from 20% of the fish population on average to just 10%; a clear sign that genetic change over just a few decades had occurred."

'Fossil egg links dinosaurs to modern birds'
Reptiles have leathery eggs, birds have hard eggs -- but another characteristic of eggs has linked dinosaurs to the evolutionary tree's birdy branch.
Reptilian and dinosaur eggs tend to be symmetrical along the major axis (pointy at both ends) whereas birds have a pointy end and a blunt end.
These eggs are avian in shape - hinting at common ancestry. But then, there are so many 'hints' at common ancestry between dinosaurs and birds, is this one really necessary? LOL

Another extinct reptile...
'Fossil turtle from Colombia round like car tire'
"The new turtle species is named Puentemys mushaisaensis because it was found in La Puente pit in Cerrejón Coal Mine, a place made famous for the discoveries, not only of the extinct Titanoboa, the world's biggest snake, but also of Carbonemys, a freshwater turtle as big as a smart car."

"the turtle's round shape could have discouraged predators, including Titanoboa, and aided in regulating its body temperature. The width of the turtle's shell probably exceeded the maximum expansion of the Titanoboa's mouth. Its circular, low-domed shape would have increased the area of the body exposed to the sun, helping the cold-blooded turtle warm to a temperature at which it was more active."

Bacteria sense salt using spring-like proteins that decline in springyness with increasing salt concentrations.

Speciation usually happens when one species divides into more than one. Occasionally, two species can interbreed, and produce a new species, but their offspring are usually infertile (think of donkeys+horses->mules)
In this case, two species of monkey flower have hybridised (A and B, in the picture), to produce C, which is infertile, and D, which is fertile.

The reason hybrids are usually infertile, is that they have different amounts of DNA, and so the haploid forms (in sperm and ova) do not match up well, to produce the diploid genome of the offspring.
In the case of this new monkey flower hybrid, polyploidization, which involves a doubling of the entire genomes of both species, took place.
This process balances the amount of DNA, and permits reproduction to happen. And hence the development of a new species, in Scotland.

Salmon exposed to copper, even in very small amounts of 5 ppb (parts per billion), are behaviourally compromised. Instead of halting, and 'playing dead', rendering them invisible to predators, they just carry on swimming.
When bound up in organic matter, copper is not a problem, but in tiny granules, it causes trouble.

Some organic compounds, however, can cause problems of their own.
Bisphenol A (BPA) disrupts the functioning of the endocrine system, which controls hormone release.
In BPA-polluted waters, the sexual dimorphism of fish breaks down, and they start engaging in bestiality - inter-species sex.
As we've already read, hybridisation usually results in infertile populations - potentially disastrous when bestiality is the norm rather than the exception.

'Prey pay a steep price to elude predators'
Small animals, such as caterpillars and tadpoles, grow faster, at first, when under predatory pressure, in order to outsize their predators.
However, their enhanced efficiency at converting food to body does subside, meaning they have to eat more food than their less-stressed counterparts in order to maintain the same growth rates.

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