Archive for the ‘Evolucija’ Category
Embedded in mudstones deposited during the Cambrian period 520 million years ago in what today is the Yunnan Province in China, the approximately 3-inch-long fossil, which belongs to the species Fuxianhuia protensa, represents an extinct lineage of arthropods combining an advanced brain anatomy with a primitive body plan.
Hardwickeovi vunasti šišmiši žive u vrčevima karnivore Nepenthes hemsleyana – svojom veličinom tako savršeno pristaju u vrčeve da se ne moraju pridržavati. Šišmiši sami borave u šupljinama od kojih su neke dovoljno velike za ženku s mladim.
Jasna je korist koju imaju šišmiši, gdje je korist za biljku? Otkriveno je da je izmet šišmiša bogat dušikom. Krasan primjer koevolucije.
Why evolution is true objavio je odličan članak o ginandromorfnim kardinalima:
This, by the way, is a very graphic demonstration of the differences between males and females, with the brighter color of the male almost certainly reflecting sexual selection (with bright colors presumably advantageous in males because they attract females, but disadvantageous in females because they attract predators).
Now how does this happen? I used to see this sometimes in my Drosophila flies, and we?ve long known how a half-male, half-female fly forms. In flies the sex is determined by the ratio of X chromosome to autosomes. Flies, like all diploid species, have two copies of every autosome. If you also have two X chromosomes, you?re a female because the ratio of autosomes to Xs is 1:1. If you have one X chromosome and one Y chromosome, your ratio is 2:1 and you?re male. The Y doesn?t matter here: if you lose a Y chromosome, and hence are XO, you still look like a male, although you?re sterile (the Y carries genes for making sperm).
If one compares the DNA “letters” in the sequences of all three species, there is only a 1.3% difference between humans and their ape cousins.
The separation between the bonobo and the chimp is smaller still. Only four letters in every thousand is changed.
But as similar as their genomes are, bonobos and chimps do display some quite diverse behaviours.
Chimps are very territorial and resort to aggressive actions to resolve conflicts, whereas bonobos are more placid and will use sex as a tool to settle their differences.
“That’s the great hope,” said Dr Prufer. “If you look at bonobos, chimpanzees and humans, what you can see is that there are some specific characteristics that we share with both of them.
“So, for instance, the non-conceptive sexual behaviour is a trait that is certainly shared with bonobos, while the aggressive behaviour unfortunately is also a trait that is shared with chimpanzees.
Mjesto: Atapuerca špilja u sjevernoj Španjolskoj
Nađeno: 28 ljudskih tijela.
Starost: Znanstvenik Arsuaga i kolege iz Sime: 600,000 godina
Starost: Chris Stringer iz Natural History Museuma UK: 400,000 godina
Vrsta: Arsuaga tvrdi – to je Homo heidelbergensis, predak Neandertalaca
Vrsta: Stringer tvrdi – to je Neandertalac,
Problem: osim 200,000 godina razlike u datiranju, profesor Stringer tvrdi da je Homo heidelbergensis predak današnjeg čovjeka.
…. the remains of 28 bodies have been dug up, the world’s greatest single haul of ancient human fossils. During this time, Arsuaga and his team pushed back the dates of their finds to 600,000 years ago and assigned them as belonging to Homo heidelbergensis.
But Britain’s leading expert on human evolution, Professor Chris Stringer, of the Natural History Museum, has warned in the journal Evolutionary Anthropology that the team in charge of La Sima has got the ages of its fossils wrong by 200,000 years and has incorrectly identified the species of ancient humans found there.
Sima scientists argue that the fossils must be older. They say the 28 bodies were thrown into the pit as an act of reverence for the dead and that the stalagmite grew over the sediment containing the bones.
However, this interpretation is controversial. No one has found any other evidence of ceremonial behaviour in humans of that antiquity. In addition, there is a deficit of small finger and toe bones. “If complete bodies were thrown in there, you would expect to see every piece of human anatomy down there,” said Stringer. “But you don’t. A lot of skeletal parts seem to be missing.”
This dating and identification has caused increasing upset among other palaeontologists. The scientists at La Sima believe H heidelbergensis is an ancestor of Neanderthals but not of Homo sapiens. However, others, including Stringer, believe it is indeed an ancestor of our species.
Gen za plavu kosu pojavio se više puta i zato se razlikuje. Najveća učestalost plave kose izvan Europe je kod ljudi koji su izrazito tamne kože.
Bustamante thinks the Melanesian mutation might have arisen between 5,000 and 30,000 years ago. 10587.jpg” alt=”"
koji gen je mutirao:
…revealed that the islanders’ blonde hair was strongly associated with a single mutation in the TYRP1 gene.
T-portal donosi članak o stvorenoj DNA koja evoluira.
Britanski su znanstvenici danas objavili da su u laboratoriju po prvi put u povijesti uspjeli stvoriti umjetne verzije molekule DNA i RNA koje su se potom kopirale i nastavile proces evolucije
‘Uspjeli smo pokazati da se kako nasljeđivanje ? pohranjivanje i prenošenje informacija, tako i evolucija, dva kamena temeljca života, mogu reproducirati i primijeniti u alternativnim polimerima drugačijim od DNA i RNA’, objasnio je Holliger i dodao: ‘Ne postoji ništa jedinstveno u DNA i RNA ? ne postoje nadmoćni funkcionalni imperativi prema kojima bi genetski sustavi ili biologija morali biti utemeljeni na ove dvije nukleinske kiseline.’
Objavljeno u Scienceu.