Conbiology: alternation of generations (plant-animals)

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greatbuddha
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Conbiology: alternation of generations (plant-animals)

Post by greatbuddha » 19 Jul 2013 21:51

After studying the reproductive cycle of ferns, I had an idea for the conbiology of shunozlo that would be a vegetarian's nightmare, animal-plants that reproduce by alternation of generations.
For those unfamiliar, it works like this
1: The tetraploid, sessile, usually photo-autotrophic "plant" stage of the organism produces many diploid offspring through meiosis, raising them to maturity in "womb-fruit", milky, fruitlike structures that hatch the second, mobile stage of the organism
2: the diploid, usually mobile "animal" stage of the organism hatches from the womb-fruit and goes about its business, either foraging on competing plant stage organisms, attacking competing animal stage organisms, protecting it's parent plant or animal-ish brothers and sisters, or immediately reproducing, depending on the species.
3: Two animal-stage organisms fuse to create another tetraploid plant-stage, their bodies becoming supports for the new seedling. Their brothers and sisters often protect them during the mating process, finding/making a suitable place for the new plant-stage to grow and reproduce.

Of course, not all reproduce in this cycle, but all complex multicellular organisms on shunozlo reproduce in some variation of the main theme, for example, in members of the phylum Muka, the plant stage is a parasitic growth on the animal stage, functioning only as a womb, rather than being an independent organism, allowing mukids to reproduce on the go.

This reproductive cycle makes for complex eusocial arrangements between plant and animal stages, the animal stages freqeuntly attacking competing plant-stages to make more space for groves of their own plant-stages, and so on. Shunozlo's forests are violent places, as the plants can actively battle eachother with their animal-stage children, rather than passively outcompete eachother by shading or quick growth.

What are your thoughts?
तृष्णात्क्रोधदुःखमिति उद्धो बुद्धः

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Re: Conbiology: alternation of generations (plant-animals)

Post by ol bofosh » 20 Jul 2013 09:25

It looks like a very interesting idea!

Not sure about the competitive thing, it's very easy for an animal to approach a plant and attack it. I imagine many would be destroyed before reproducing. Like you say, it's sound like it would be very violent, so there'd be all sorts of interesting combat adaptions. The other thing is that ecologically photo-autotrophes outnumber other trophes. Either there'd be plants that didn't have an animal stage or there'd be less offspring than parents.

How do the autotrophes collect nutrients? Though roots, or some other way? (I was just thinking of root growth rates).

Just some thoughts. [:)]

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Re: Conbiology: alternation of generations (plant-animals)

Post by Lambuzhao » 20 Jul 2013 18:34

This idea reminds me of three creatures:
1) Hydras
2) Xenomorphs from Alien
3) Farmer ants (various species)

I happen to like each of these animals for their own merits, so I hope it "bears fruit" for you.

You might even have "slaver" species (cf. ants) that take over groves of other species' sessiles to produce for them.

What a combination!
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Re: Conbiology: alternation of generations (plant-animals)

Post by basilius » 21 Jul 2013 15:51

Very cool idea!

The only bit I'd doubt is the stability of tetraploid chromosome set, especially for taxa above species level.

Haploid plant + diploid animal would look much more plausible.

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Re: Conbiology: alternation of generations (plant-animals)

Post by greatbuddha » 23 Jul 2013 02:51

Obviously, some of the aniimal-stage organisms (especially those of rapidly reproducing organisms like grass), would be no more than spores, but in regions that are k-selected (like tropical jungles), large/intellegent animal-stages that could outcompete for space to raise plant-stages would dominate.

Also, plants are tetraploid/diploid
animals are diploid/haploid (1/2 of plant stage), not the other way around, like in ferns.
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Re: Conbiology: alternation of generations (plant-animals)

Post by basilius » 23 Jul 2013 17:07

greatbuddha wrote:Also, plants are tetraploid/diploid
animals are diploid/haploid (1/2 of plant stage), not the other way around, like in ferns.
I don't think I understand you.

Tetraploid sets (and polyploid sets in general) are unstable.

In ferns, the diploid sporophyte dominates the haploid gametophyte, but in mosses it's the other way round.

The haploid gametophyte of ferns is autotrophic, thus hardly can be called an animal.

In more advanced organisms, the haploid form (gametophytes in vascular plants, males in hymenopteran insects) is basically busy with nothing but reproduction, and the diploid form is a more functionally full-fledged organism. That's not surprising since diploid is the default state in higher organisms in general.

That's why it seemed to me that with sentient animal phase and non-sentient plant phase, it would look more natural to have the animal phase diploid (and plant phase haploid).

If the plant phase is also sentient, and especially if it's somehow more advanced than the animal phase, their ploidy is better reverted.

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Re: Conbiology: alternation of generations (plant-animals)

Post by Omzinesý » 23 Jul 2013 18:03

Interesting idea!

All generations of the speacies X must have similar genes (of the species X). That means there must be many vain genes, e.g. ones that produce a cell wall for a plant but do nothing for an animal. Of course, humans and pears have 95% same genes.

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Re: Conbiology: alternation of generations (plant-animals)

Post by Salmoneus » 24 Jul 2013 15:20

basilius wrote:Very cool idea!

The only bit I'd doubt is the stability of tetraploid chromosome set, especially for taxa above species level.

Haploid plant + diploid animal would look much more plausible.
Why do you doubt tetraploids?
For one thing, tetraploids are common on Earth - any kind of salmon-like fish, for instance, plus apples, durum wheat, potatoes, cabbages, etc.
For another, these alien 'chromosomes' may work differently from Earth chromosomes, so different ploidies may be viable and/or stable than on earth (and even on earth it varies dramatically - ploidies come and go all the time in salamanders, but are stable at family level in fish, and almost entirely inviable and fatal in mammals).

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Re: Conbiology: alternation of generations (plant-animals)

Post by basilius » 24 Jul 2013 18:56

Salmoneus wrote:Why do you doubt tetraploids?
I didn't doubt tetraploids, I doubted their stability in the long run. Like, we don't see many families or orders where all species are tetraploids (it's more like we see some genera and families where ploidy varies a lot).

Compare:
greatbuddha wrote:Of course, not all reproduce in this cycle, but all complex multicellular organisms on shunozlo reproduce in some variation of the main theme <...>
There is a reason for this, I think. Like, our meiosis groups chomosomes in pairs (for recombination etc.), not triplets or quartets; with this mechanics, diploid sets are fundamentally more stable than other ploidies.

Also, chromosome sets are often slightly different in closely related species. This seems to mean that speciation often involves rearrangements of chromosome sets. It's no wonder that diploid sets are preserved/repaired in such rearrangements (there's little choice), but with tetraploid sets there's not much sense in repairing them as tetraploid ones (very little is lost if they are degraded to diploid sets, e. g. via breaking some quartets in two pairs).
For another, these alien 'chromosomes' may work differently from Earth chromosomes, so different ploidies may be viable and/or stable than on earth <...>
Grouping chromosomes in pairs is the simplest and easiest option.

But you are right, one can imagine various curious alternatives. Like, the alien (equivalent of) meiosis grouping chromosomes into triplets or quartets. The molecular mechanics has to be much more sophisticated, but I don't think it's impossible.

However, I think there must be some asymmetry involved for such alternative mechanics to be stable: like, triploid zygotes with diploid and haploid gametes, or tetraploid zygotes with triploid and haploid gametes. Because if we have tetraploid zygotes and diploid gametes, I suspect there'll be a way to spoil the refined control machinery so that it guarantees correctly grouping only pairs (within an incorrectly assembled quartet), and still allows for correctly separating those pairs - thus effectively degrading the whole into our familiar diploid-haploid alternation.

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Re: Conbiology: alternation of generations (plant-animals)

Post by AureusFulgens » 26 Jul 2013 15:31

I find this idea extremely fascinating. Have you ever read Speaker for the Dead by Orson Scott Card? He does something similar with his pequeninos; his mechanism was a virus, though, rather than alternation of generations.
<wild-speculation>
As to the question of ploidies (is that a word?): it seems to me that there wouldn't be a practical difference between tetraploid/diploid and diploid/haploid; at some point in the past, the species for some reason duplicated all of its genes, leaving it with a set of twice as many chromosomes that would reproduce just like before. It wouldn't be of much consequence that every pair of chromosomes would have a twin. The difference would be mostly historical.
Every gene appearing twice could create some interesting genetic patterns, though. A recessive gene would have to appear four times to be expressed, for example. I also imagine that the extra copies might gain new functions over millions of years: perhaps in 50 million years one pair of genes for fedora color are still genes for fedora color, but the other now governs a different feature (trench coat color, maybe).
</wild-speculation>
All this coming from someone with no formal qualifications in this subject beyond a high school class. Still, some things to think about.
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