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World of micro-life; Aliens at dawn of complex life
Topic Started: Feb 24 2009, 04:19 PM (617 Views)
KayKay
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This is just a side-thing I'm working on. It won't be updated very often.

Details:

The planet is second from the sun, a young yellow dwarf star. It is slightly closer to the sun in relation to Earth from our own star. The planet is covered in approximately 60% salt water, and about 4% liquid fresh water. The sea water is full of dissolved limestone which prevents it from becoming over acidic in the presence of acid rain and high C02 levels. Certain metals are in high amounts such as iron, zinc, nickel, copper, titanium and magnesium. Seas are generally rich enough to support plenty of life forms.

The planet is about 30% larger than Earth. The gravity is ever so slightly stronger, but barely enough to affect microscopic life any differently than Earth's gravity. The atmosphere is slightly thicker and denser. Extreme weather is common worldwide, particularly thunderstorms, hurricanes and tornados. Cold weather conditions such as snow and frost are extremely rare and confined to very high altitudes. Very high altitudes are rarer due to the high gravity weighing mountains down into the mantle.

Atmospheric composition resembles early Earth, with high levels of CO2 (15%), N2 (80%), O2 (3%) and others (2%).

Photosynthetic organisms evolved late on this planet. It appears a disaster similar to the oxygen catastrophe on Earth has just occured in the oceans a few hundred million years prior to the discovery of the planet, with the recent boom in oxygen levels. Now many surviving life forms utilize the oxygen for respiration. Before then, it is believed that life forms that used photosynthesis did so poorly and produced little to no oxygen as a waste. It's estimated life has been evolving for about 4 billion years.

The planet is within close proximity to an asteroid belt, so it has become the blame for the delay of the development of complex life. A popular idea as that asteroids killed off complex life forms before they could get a chance to radiate and speciate. There have been a good 30 or so large craters discovered on the planet's surface so far, ranging between a billion and 45 million years old. At the current going rate, the planet is overdue for another strike, though the spread of strikes over time may be irregular, and at one point it's thought the planet had a quiet period of about 200 million years without any major strikes, opposed to a 100 million year period with several. However, there may be a crater lying undiscovered from within this time.

The planet appears to be volcanically active and has all of the tell-tale signs of tectonic movement. This means there is the high probability of life existing in volcanic conditions, such as underater hot vents or black smokers.

Samples of some major plant and animal groups are being retrieved. The first samples returned were of simple microscopic organisms, as of yet no complex multicellular life has been found.

Life forms known to exist on the alien planet:

Animal Equivalents

The equivalents of animals on this planet is a little hard to define. Even though most life forms have a very Earth-like cellular structure, the seperation between animal and fungus is hard to distinguish, so this large group will be referred to as animal-like, but may include species with fungus-like features.

In the samples recovered from the alien planet there was a varied mixture of organisms.

One large group had replicating nuclei. A master cell would copy its nuclei to produce other cells for various functions, rather than copying itself by mitosis and then differentiating the new copy. Decomposers with a single master cell were placed in a detritus environment with material from their own planet. They were then observed to settle down onto the detritus. The nucleus was copied and the new nucleus travelled down the cell towards the detritus where it exited the cell in a packet of cytoplasm, carrying a membrane and mitochondra with it. Still attached to its parent cell, the new cell differentiated into a hypha and began to grow and divide into more branching hyphae, which were then used to digest and channel the detritus nutrients up to the master cell.

Unlike fungi on our planet, only the hyphae of these creatures have a cell wall of chittin. The master cell lacks a cell wall.

Out of the samples species, there was very little variation in this basic design of forming hyphae. However, we now know that there are at least two major groups seperated by their method of reproduction.

Asexual reproducing decomposers

Once a decent network of hyphae have formed the master cell's nucleus divides once again. However this time it copies itself in large numbers and the nuclei travel up the cell. The nuclei exit the cell in the same way as the undifferentiated hypha did, this time detaching from its parent cell and being carried off in the current or settling on the detritus somewhere near by as a new master cell. This process is slow but while there is a steady stream of nutrients coming from the parent's hyphae, the process is constant.

'Sexually' reproducing decomposers

These have a slightly more complex life cycle. The master cell is observed usually to be larger in this group of species. The nucleus replicates itself but this time is sent to an empty pocket within the cytoplasm, surrounded by a membrane. By entering the pocket the nucleus forms its own membrane and begins to divide at a very small size until it has taken up one side of the pocket. This row of new cells then divides further without copying its DNA, forming haploid cells.

This process repeats itself, with more nuclei being used to form more diploids to make more haploids until the cell can no longer support the bulging pocket of zygotes. The pocket travels to the edge of the cell where all of the new zygotes are dumped by exocytosis.

New zygotes are carried in the water currents or whip their flagella to find another zygote from a different parent. Different antigens attract, while zygotes that secrete the same antigens will not fuse. So there really are no sexes as such, which makes this form of reproduction hard to define with just one term.

It is not yet known exactly how antigens differ so much between generationas and individuals. All that is known is that there is just as much difference in antigens between parents and offspring as there are between random, unrelated individuals.
Edited by KayKay, Mar 5 2009, 02:28 PM.
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Venatosaurus
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Very nice so far, looks promising :)



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KayKay
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Thanks. The part on life forms is updated, but still isn't finished.
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Venatosaurus
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Very nice. I hope some drawings of these lifeforms are uploaded soon.



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