User:ASmartKid

Amazing biological fact of the day! (hopefully an acceptable use of my user page!)

31st March '10 - 1 I mentioned sex determination earlier. But I hadn't realised that our genetic sex determination system (which has apparently independently evolved several times) is special in that neatly ensures a balanced male/female ratio (female infanticide excluded). Our (for any male readers) Y chromosome stopped being autosomal maybe 100-200 million years ago and has clearly diverged somewhat from its X-partner and some recombination inhibition prevents most (but not all) crossover. The disadvantage is degradation of the chromosome and possibly even an eventual need for a new sex system. The Dunnart is a marsupial with only 4 genes on its Y chromosome (we have 86 or so?)! Temperature-dependent sex determination has its own problems, however: "Global temperature change can skew the sex ratio of TSD animals and might have played a significant role in the demise of long-extinct species, notably the dinosaurs... Current global warming also represents a risk for extant TSD species."

24th August '09 Prion diseases were things I'd often heard of but for some reason I'd never looked them up. My loss! Turns out they seem to be, in a way, diseased proteins capable of passing on that disease (a different conformation) to other proteins (of the same kind). But these self-replicating states of proteins are resistant to proteases so the body can't break them down and they build up to do serious damage. Another amazing thing is just how little is known about them: even the basic description I've just given might be wrong! Also take a look at Kuru (disease) which was maintained by ritual cannibalism in Papua New Guinea. The way these prion diseases affect behaviour (before causing death) is also very interesting (as with dementias caused by protein build-up - for example, DLB causing hallucinations of animals).

23rd August '09 Take a look at this article for a description of some parasites that alter the behaviour of their hosts. Along with Toxoplasmosis in humans, it describes such gems as Hymenoepimecis argyraphaga, Glyptapanteles, Sacculina and Acanthocephala. It's a little shop of horrors!

20th August '09 Female spotted hyenas have fused labia and instead use their huge clitoris (or pseudo-penis) for urination, intercourse and child birth! And if the cub survives this (not to mention the mother), the newborns tend to fight "from the moment they are born".

Hopefully, all the facts I've given so far support the idea that you could pick almost any species at random and see in it remarkable and unique behaviour and attributes, developed over millions of years. Not to mention that their genes, chemicals and behaviours can be useful to us. Many of these are now disappearing forever as biodiversity is lost. :(

18th August '09 Various facts today. Check out Honeypot ants. Demodex mites live in your hair follicles but come out to roam your skin for food. You can see them "by removing an eyelash or eyebrow hair and placing it under a microscope." "The mite's digestive system is so efficient and results in so little waste that there is no excretory orifice." Naegleria fowleri also known as "the brain-eating amoeba" is simply horrible. Another amoeba, Amoeba dubia has a genome over 200x larger than humans', while Jack jumper ants have n=1 chromosomes.

17th August '09 Platypus have venemous ankle spurs and use Electrolocation. Definitely aliens.

10th August '09 Eusociality is, of course, amazing. German wasp colonies - that may contain 3,000 wasps - "usually last only one year, all but the queen dying at the onset of winter." Also take a look at Naked mole rats.

The life of a queen honey bee would make a good film. Chosen from amongst the worker eggs, she is fed only royal jelly in a special queen cell to become a virgin queen. But she is not alone. Upon emerging, she must kill off any virgins still in their cells and fight any emerged ones to the death (though workers may prevent fighting at times to allow some to join 'after-swarms' to new locations). The victor then flies out to collect a lifetime's supply of sperm in a several day gang-bang with her brothers. I could go on, but the whole article is full of wonder ("cuddle death" and "more than her own bodyweight in eggs every day" for example). Drones (haploid and hapless) have the sole task of mating with the queen (and helping to heat the hive if it gets cold!) but, if one does, "it will soon die because the penis and associated abdominal tissues are ripped from the drone's body". Drones seem unnecessary - a circuitous route for the queen to convert eggs into lots of sperm with which to fertilise herself! The female, diploid workers have lots to do and could even produce drones were it not for the effect of the queen's pheromones.

(I have mentioned ants elsewhere, while termites have their share of quirks. They often have kings too which provide sperm as needed, mating for life. Workers have great symbiotic relationships with bacteria for breaking down cellulose and then feed all the other members of the colony. Some species also have fungi farms! And of course their nests, both the ones on the ground and those in trees, are simply amazing.)

8th August '09 Komodo dragons sometimes/often prey on the young of the species. This is effectively a way to send out small, agile collectors of small insects, lizards, mammals etc. and then harvest them. This presumably causes a great selective pressure to growing big and growing fast. Perhaps it is also one of the reasons why females can parthenogenetically produce litters of males. "The Komodo dragon has also been observed intentionally startling a pregnant deer in the hopes of a miscarriage whose remains they can eat, a technique that has also been observed in large African predators." These interesting facts are in addition to their being huge venomous reptiles that can smell carrion 9.5km away, can't suck water as they don't have diaphragms and can live on as few as 12 meals a year. (Another article today reminded me that kissing is not 'native' to every culture. It is a bizarre behaviour!)

7th August '09 Mammalian red blood cells, as you may know, don't have nuclei but - except for a few species - other vertebrates do. I wonder if we needed this because of our energetic warm-bloodedness. The most interesting point to me here is how consistently different Classes can be. Another example is the ZW sex-determination system found in birds and others (inc. Komodo dragons! Also, males are the homogametic sex - ZZ.). My rather loose point is that I never realised there are such low-level differences between vertebrates and I wonder what isolation and evolution (and extinction of intermediate species) must have created these divisions.

Summer '09 2 I was a bit worried to hear that my DNA is full of transposons and possibly retroviruses. Not only is our body full of 'foreign' organisms but our DNA is too! I knew about 'junk DNA' but I thought any viral DNA was long dormant. Reading about these genetic antics reminds me of the computer virus/AI development in the Hyperion series of books. It's all a bit sinister, though possibly very important for evolution and our biology. I thought this was pretty clever: "The transposons which only move by cut and paste may duplicate themselves if the transposition happens during S phase of the cell cycle when the "donor" site has already been replicated, but the "target" site has not."

There are even viruses that use other viruses for replication (see satellites and the Sputnik virophage), as well as lots of mixing of genes (like with different mutants of HIV effectively mating when found in the same cell).

The rabbit hole continues down through this world of genes. Intragenomic conflict catalogues more gene selfishness, while a 'green-beard' gene in Red imported fire ants makes them kill any egg-bearing queens that lack it. I hope, but find it unlikely, that our own opinions of others are unbiased by the genes (therefore phenotypes) we share with them or don't. Also check out Medea genes and their potential use in fighting disease.

Summer '09 X-inactivation. I wonder how the randomness happens.

22nd July '09? I'd never considered it, but there are many sex determination systems. I shan't repeat what's on the page except to point out the dominant clownfish becoming female and bacterial infection determining sex in some species! I wonder if we could engineer other exotic systems - perhaps in humans - such as having more than two sexes, or using a third individual as a host.

11th July '09 There are such things as 'supercells' - plasmodial slime molds - that many nuclei and one massive membrane. If that wasn't crazy enough, Physarum polycephalum is studied for its intelligence. Of further interest is how this single cell can be compared to a memristor.

(I also remember a documentary from my childhood that was possibly about an abandoned shed and was possibly narrated by David Attenborough that possibly showed a pseudoplasmodium moving along (Dictyostelid?). If anyone else recalls this, please let me know!)

10th July Isn't it amazing how cells organise themselves? http://davislab.med.arizona.edu/bbb.ht2.gif

5th July If one has compound eyes, one can increase their size by simply adding new lenses at the edges. Because of the small lense size, diffraction decreases resolution ability.

3rd July Genes, genes everywhere. I watched a video in which Craig Venter said (as Dawkins perhaps did) that we should think of the biological world in terms of genes or gene families rather than organisms. Viruses 'living' inside bacteria (called Bacteriophages) are common - in fact, probably the most common 'organism' on the planet! "ASmartKid now sees the planet as completely covered in genes and, for some reason, finds it disturbing. Could 'grey goo' ever compare to these molecular masters of self-replication?"

3rd July Apparently there are ants classed as 'slaver ants' that survive by taking over the workers/food/habitat/queen of other species. http://everything2.com/node/1026941

3rd July We have two (or more?) kinds of sweat glands. The underarm/perineal ones, unlike the usual skin ones, release proteins and fats in addition to water (like mammary glands). This is a throwback to pheromone production (or maybe still is). Bacteria digest these delicious foods and release smelly waste. Maybe they could be genetically engineered to use less smelly reactions or, ultimately, we could replace our apocrine sweat glands with eccrine ones.

1st July Wharton's Jelly in umbilical cords seals the cut as it is exposed to the air. If not cut, the cord and placenta will simply dry up and fall off. It is amazing that the newborn body can switch from one set of vital systems to another so rapidly.

(Also, sleepwalking etc. do not take place during REM sleep. Movement during REM is a problem. It is very intriguing that our brains can be working perfectly well in N3 sleep - walking around, finding food, driving! - without us being conscious. It is believed that nocturnal penile tumescence is caused by the lack of distraction and ability to inhibit erection that we usually have while awake. Women have a similar arousal.

There could be an endless list of interesting facts about sleep!: horses sleeping standing up, monks doing the same, varying amounts of sleep and REM sleep between species, half-brain sleep, newborn whales not sleeping, fatal familial insomnia...)

??th June '09 Naked mole rats seem not to have certain kinds of pain receptors. (Also - for any creationists out there - why did God give eyes to a creature that can't use them? As with the blind cave fish.)

29th June '09 When the Maori arrived in New Zealand they would have discovered the Moa and the Haast's Eagle - a land ruled by giant birds! The birds were then, of course, driven to extinction between 1300-1400. And these are just some of the giant birds to have gone extinct in the last 1000 years. http://en.wikipedia.org/wiki/File:Moa_mock_hunt.jpg

26th June '09 Annelids are a much more diverse phylum that I had realised. "'Barry' the [4ft long] sea worm had been nestling under coral reef, attacking it and fish, at Newquay's Blue Reef Aquarium in Cornwall". Also, Spirobranchus giganteus. http://commons.wikimedia.org/wiki/File:Haeckel_Chaetopoda.jpg

25th June '09 Girl who doesn't age: http://abcnews.go.com/print?id=7880954 Though perhaps the more remarkable thing is that most of us do grow.

24th June '09 See picture. Enough said. http://en.wikipedia.org/wiki/File:Pharyngeal_jaws_of_moray_eels.svg

Thank you Wikipedia Reference Desk!

Data transmission speeds http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Computing/2009_July_2#Data_transmission_speeds

This question had quite a few responses.

My other question didn't go quite as well.

References