Reptiles and facultative parthenogenesis

If you understand the title of this post, you have my undying respect. Most people wrongly assume  that asexual reproduction only occurs in prokaryotes and plants, by binary fission or runners for example, however animals can also reproduce in this manner, and not via divine impregnation. Seriously, if you are a devout catholic I suggest you leave this page and maybe read the Bible instead. In parthenogenesis an embryo develops from an unfertilised egg and the process occurs perfectly naturally in invertebrates like scorpions, and also in a select few vertebrates, like the Komodo Dragon (yes, it deserves capital letters). A normal egg cell produced by meiosis has the haploid number of chromosomes, as the other half of the offspring's genome is made up by the father's haploid sperm cell. However in parthenogenesis such haploid individuals are non-viable (may die during embryonic development or have a low zygote hybrid vigour) , and the parthenogenic offspring must often be diploid. Therefore full clones produced by parthenogenesis develop without the need for meiosis to manufacture haploid gametes in parents. But how is an embryo produced without without fertilisation? I hear you scream. Well, a mature egg cell is produced from mitotic oogenesis, which then develops directly into an embryo. This process is known as apomitic parthenogenesis, and is the less complex branch of the phenomenon. When parthenogenesis does occur with meiosis, offspring may be haploid, like the male ant, however there is often a complicated chain of processes which occur to restore diploidy to the offspring, in order to make them viable. However these offspring are only half clones of the parent organism, so they are genetically in-identical. But what I really want to talk about are the facultatively parthenogenic Komodo Dragons, which usually reproduce sexually, but can occasionally reproduce asexually. Therefore, when no viable males are present in a habitat, a female can ensure the survival of the species via parthenogenesis, making them more resistant to extinction than most species. What I particularly like about the Komodo Dragon, apart from its totally awesome name, is its ZW-sex determination, in which ZZ genotypes create males, ZW creates females, and in rare cases the WW genotype creates a female, however it is mostly unviable. Komodo Dragons are just too awesome for the XY sex determination system, although that may be a rather subjective analysis. In conclusion, the fact that an intelligent organism can clone itself in a pinch, to ensure the continued evolution of its species, is an incredible feat of mother nature. Imagine if we could induce parthenogenesis in humans? I mean, we've done it in fish...Actually, I don't like what I'm imagining. Bye!

Is this the Matrix?

Have you ever had a sudden panicked moment when you believe you've experienced something before? A conversation, a person or anything really. I know I certainly have, but thanks to science, I'm pretty sure that we are not all living in a computer generated world whilst robots harvest our body heat for energy. Deja Vu is not a glitch in the Matrix. The simplest, memory based, definition of Deja Vu is that a stimulus that triggers the feeling is linked to a similar memory that is already stored within the hippocampus, but which the person cannot remember. So if an event in the present has strong associations to a forgotten event in the past, then the feeling of Deja Vu is triggered. In 1941 researchers attempted to recreate the feeling in a laboratory, using hypnosis to induce post-hypnotic amnesia on volunteers. They were then shown a stimulus they had encountered before the hypnosis, yet only 3/10 people experienced Deja Vu. Spooky right? Although this test is of limited reliability given it's small sample size... so I wouldn't trust it implicitly. Recent virtual reality studies indicate that Deja Vu is more often triggered by the degree of familiarity felt in a certain situation, and so when a similar, familiar situation is encountered again, a person believes they have already lived through it. Location also appears to be important in this effect, as the degree of similarity between the spatial layouts of the previously experienced scene (which the person has forgotten) and the present scene increased the instance of Deja Vu in the VR test subjects. Cryptomnesia is another possible explanation for the phenomenon. I would like to take this moment to apologise to my readers who look down in haughty derision at the social sciences. Whilst I often do that myself, I thought this was too interesting a concept to pass up. Anyway brace yourselves, more unsupported conjecture coming your way. Cryptomnesia is essentially when information learnt is 'forgotten', but is still stored somewhere in the depths of the hippocampus, and is vaguely recalled based on more established concepts. The original memory is therefore distorted, and parts are omitted entirely. When this 'butchered' memory matches a current situation, Deja Vu is triggered. Each time we recall that 'memory' we are recalling our last construction of it. Deja Vu could therefore be a means of reconstructing and repurposing forgotten information to suit current needs. Although that theory does sound rather frivolous given its lack of scientific grounding. In truth, we don't fully understand the human brain, and researchers aren't really sure why Deja Vu like events are so different from person to person. Personally I think social conditioning has a part to play, as the populous are so aware of the phenomenon that they assume every half formed memory is Deja Vu. But then again, who doesn't want a little supernatural in their life?