I’ve just watched the sci-fi movie Life. Without spoilering, it concerns an alien life form taken on board a space station. Like the *Alien *franchise alien, it starts small but grows large and mean and people start dying. This takes place very quickly (a few days?) in the film universe.
My question: are there natural limits to the rate an organism can grow, or could it happen that fast?
Two assumptions - (1) it has to grow solid mass, so its not just ballooning and stretching with ingested goo or gas; (2) it can’t grow by magic but has to correlate with consumption, presumably a well-balanced diet of nameless red-shirts.
For vertebrates, I would guess that bone growth provides one limit to the speed of turning food into size, but is that true of other creatures?
I remember reading a science story once when I was a kid. They hashed out the science of what it would be like to a human if they were shrunk down to the size of a bug. I think I remember reading the a human would have to eat every 20 minutes just to stay alive.
So speaking to your OP, it seems like your hypothetical alien would need a constant food source 24/7 and have little or no time for sleep for fastest growth.
Bacterial colonies can double in size every 10 minutes if they have unlimited resources. In the case of a macroscopic organism, limitations are going to be placed by how fast nutrients can be absorbed and distributed to growth centers in the body. In addition, unlike bacteria a larger organism will need to expend energy in movement and maintenance.
Bacteria probably minimize their volume and genome size partially to be able to reproduce quickly–the fastest can do a cell division in around 10 minutes. Larger and more complex cells take longer. Moleculestake a finite amount of time to move through a cell. Any multicellular alien with complex cells based on molecules in a fluid medium would have similar growth restraints to life on Earth. To grow fast, the alien would have to be very, very different chemically from anything that we are familar with (at which point it would be able to digest redshirts as well as we can digest granite.)
Which demonstrates the constraints on macroorganisms vs bacteria. While impressive, that growth rate is trivial compared to bacteria. Baby blue whales have a very fast growth rate, but still take six months just to double in size.
The segments in a bamboo stem exist before the shoot emerges from the ground.
I imagine there are species of bamboo where the amount of stem growth might be approximately equivalent to the distance between nodes, but the nodes aren’t like the growth rings in a tree
Its probably not applicable, but baby blue whales can gain 9 lbs per hour while growing.
However I assume the rate of growth is also relative to starting weight. Thats about 3% of their birth weight per day which is a lot faster than human babies grow (I think they gain closer to 20% of their body weight in a month).
The rapid growth of things like bamboo or mushrooms is more a rapid redistribution of resources, like hydraulic inflation. It isn’t absorbing all the nitrogen, carbon, phosphorus, etc. for growth during the growth spurt - it absorbed all those things the previous year and stored them.
As mentioned, the first and foremost factor is food intake. To gain 200lb the average alien should eat a absolute minimum 100lb of red-shirts. They you get to nutrients and digestion. The human digestive tract is over 30 feet long and food takes 24 hours (give or take) to go through. There’s a whole science on how the body takes some intakes and synthesizes others - fat to sugars, etc. And, if the creature is warm-blooded, it needs a decent amount of nutrition to maintain body temperature, especially since alien monsters growing at a rapid pace forgo insulating clothing. Entropy - the creature can’t do a 100% conversion. Presumably a decent amount of fluid intake is also needed to ensure the material in the gut goes through the lining of the intestines easily. Now some humans appear very thin-waisted, but to pack a full gut containing 100lb of masticated human, assuming normal digestive processes, would mean a pretty chubby alien. The 3-foot version is not likely to be chowing down a whole human in one sitting, even if those are short sittings between runs to the toilet. (There will always be something to come out, even if it’s just the zippers, lycra, rubber shoe soles, and half-chewed communicator. Plus how clever is this alien? (not very, in most movies). Apparently 30% of our nutrient intake is used to keep our brains functioning. Also remember the square-cube law. A creature twice the size of a human and about the same shape (to fit in the rubber suit) would need to be 8 times the volume, so the station should be running out of red shirts running around solo well before the creature gets that big. So early on, size would dictate it takes a while to grow big due to intestinal volume and throughput speed; the little guy would have to lurk over the corpse for a while to finish it all off, making frequent bathroom trips. (How long would it take you to eat an entire goat or deer?) I assume baby whale is packing on the pounds because mama’s whale juice is high in fat which is going directly to junior’s epidermal layer with minimal processing.
Remember paleontologists tell a lot about a creature from his teeth. To properly digest your local space station resident, the creature must fully chew them to a pulp. Otherwise, digestive processes will take a lot longer. There was a suggestion in some recent book on evolution that herbivore apes spent far too much time chewing because of the low nutrition value of plants, and so homo sapiens has the biggest advantage because we are meat-eaters. Meat digests better, but still, less chewing means slower or less efficient digestion, so some of the food value of a full-sized human corpse would be lost without a lot of chewing. Does he have the teeth to grind your bones to make his bread, or would he chew away for hours on one bone like your favourite basset hound? This implies very strong jaw muscles, which also need food energy to operate…
Then there’s the matter of diet. Was this alien evolved (or designed) to eat humans? why is this a good diet? I guarantee the first alien life form a human might find on a distant planet would not be an ideal substitute for Gerber’s Baby Pablum…