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Posts Tagged ‘ecology’

Room Needed on the Ark

Startling StoriesImagine in the not-so-distant future an asteroid is on a direct course to hit the Earth. It’s large enough to destroy most life as we know it. NASA, the European Space Agency and China’s National Space Administration are scrambling to launch teams that will attempt to deflect the asteroid, but there is no guarantee that they will be successful.

Meanwhile a team of scrappy and resourceful aerospace engineers and biologists put into motion a plan meant to rescue at least a few species – including humans – from extinction. A spacecraft that will carry genetic material, along with live plants and animals, is readied for launch.

The hope is that after escaping the cataclysmic effects of the asteroid strike, the space ark would travel long enough for the Earth’s dust to settle (literally) so that the ship could return and restore life on our planet. Or perhaps the ship would continue on to a distant solar system, and the life it carries would be used to start a new settlement on a habitable planet.

This would obviously be a technically complex operation that would require substantial advance planning. One of the big tasks for the biologists on the team would be to decide how the genetic material and live travelers on the space ark would be selected and collected.

An obvious source of genetic material would be gene banks that collect and store samples of a wide range of genetic material. Such repositories exist today. The Millenium Seed Bank Partnership, for example, is an international project meant to save seeds from wild plants around the world. There are a number of other more agriculture-focused gene banks around the world that preserve seeds from a variety of crops.

Animal genetic material is a bit more difficult to archive than plant seeds. Projects like the US Department of Agriculture’s national Animal Germplasm Program primarily focuses on collecting and storing semen and eggs, not embryos.

There is also a current push to sequence the genomes of as many different species as possible. Perhaps in the future will have the technology to start from a raw DNA sequence to create a living breathing animal. There have been recent proposals to use DNA sequences along with reproductive cloning technology to restore wild animal populations on the verge of extinction.

But whether an “archived” animal is grown from germ plasm or from a synthesized DNA sequence, there still must be at least one female for the fetuses to grow in. Not a simple proposition.

But it would not be enough for our space ark to carry a male and female of each species. There must be a minimum number of genetically distinct individuals to allow a population to survive and thrive.  Conservation biologists estimate that such a “minimum viable population” would require anywhere from a hundred to several thousand members to survive at least a century. The lower estimates usually assume that there would be minimal environmental changes and human intervention to keep the population going.

Even with human intervention a lack of genetic diversity in a population puts it at serious risk for being completely destroyed by disease or unexpected environmental changes. That’s already a problem today. Disease outbreaks have put agricultural “monocultures” of some crops (like the Cavendish banana) at risk of extinction.

If samples from many individuals of a species are required for genetic diversity, our hypothetical space ark might not have enough space to carry every known species. So how would a biologist decide which critters are most important to save? That turns out to be a complicated question.

Restoring – or creating – a stable ecosystem needs to have a wide variety of different species from microbes to large vertebrates and algae to trees. The exact needs would depend on the local climate, soil and atmospheric conditions, among other factors. So far, we humans haven’t been very successful in creating an ecosystem from scratch. And the less that’s known about the environment where the ecosystem is going to be established, the longer the list of potentially necessary species.

So for the space ark scenario to work, it would not only need to carry a variety of species, but a variety of individuals in each species. And that is, of course, in addition to the humans – not just an Adam and Eve, but a large mixed group of people with enough genetic variation to start a healthy human colony. Throw in the complex social and political considerations in selecting who gets rescued and the population would probably have to number in the thousands.

Our hypothetical space ark would have to be huge to carry them all!

The space ark scenario is admittedly pretty implausible, at least with present-day technology. Even so, I think it’s worth seriously considering how it might be done. That’s not just because catastrophe is always a possibility, but because I’d like to think that some day self-sufficient extraterrestrial colonies will be a reality. We need to start thinking about how we might do that now so that the genetic material can be saved and reproductive technologies can be developed before they become a necessity.

But there are many questions that need to be considered:

If we are going to collect and archive seeds and animal germ plasm and genomic DNA sequences should the focus be on agricultural species? or should we cast our species net as far and wide as possible?

Should we seriously consider setting up a gene bank on the Moon, just in case something terrible happens to the Earth? or would it be better to have our archives closer at hand so that they can be more easily maintained and added to? How much redundancy should there be between different seed and germ plasm repositories?

Or should we focus more of our resources on developing synthetic biology techniques, in the hope that they will eventually become advanced enough so that collections of physical specimens will become unnecessary?

And if Earthly life is destroyed, would it be worth trying to restore Earth’s ecosystems or better to start over elsewhere among the stars?

What do you all think?

Technical Reading 

Blackburn HD “Genebank development for the conservation of livestock genetic resources in the United States of America” Livestock Science 120:196-203 (2009) (pdf)

Holt WV et al “Wildlife conservation and reproductive cloning” Reproduction 127:317-324 (2004) (text)

Traill LW et al “Minimum viable population size” a meta-analysis of 30 years of published estimates” Biological Conservation 139:159-166 (2007) (pdf)

Shaffer ML “Minimum Population Sizes for species Conservation” BioScience 31(2):131-134 (1981) (pdf)

Zhu et al “Genetic diversity and disease control in rice” Nature 406:718-722 (2000) doi:10.1038/35021046 (text)

 

Sinking in the Deep Blue Sea

In last week’s news, there was a story about a businessman who dumped large quantities of iron into the ocean off western Canada after convincing the locals that it would improve salmon fisheries. The resulting algae bloom can be seen from space.

Peggy Kolm:
This sounds like a science fiction story all by itself: geoengineering, apparently unscrupulous businessmen, deceit, science. I asked the regular SiMF contributors what they thought: Is this going to be the future: private individuals taking large projects on themselves in hopes they won’t get caught? Or should government or international organizations take over? Or should we not mess with things we don’t understand?

If this were a science fiction story, the guy who proposed the iron dump would probably be the hero, who proves the nay-sayers in the scientific establishment wrong with his bold move.

In real life I think it’s especially a concern when there is potential for long-term damage of the environment on an international scale, like this ocean dump.

My gut feeling is that there should be consequences of some sort if such projects without adequate small-scale testing cause massive damage, but it would be better if they could be stopped before the damage was done.

I’m not sure how that could be managed. Seems like governments are as likely to be complicit in the problem as they are to effectively regulate it.

I suspect we’ll be seeing more stunts(?) like this in the future.

Paul Schroeer-Hannemann:
He was incredibly reckless. Global warming might cause major long-term damage to the environment but algae blooms have been known to cause immediate damage to aquatic ecosystems. One can only hope we don’t get another well-intentioned but foolhardy businessman doesn’t do something worse like spraying sulfur aerosols into the upper atmosphere.

Athena Andreadis:
The other mind-boggling point in all this is that the Haida village did something that 1) they knew would affect the entire area, 2) solely on this con-man’s word, 3) with their salmon restoration fund. Surely they could have spent some of that money to get a second opinion? Notified others in their nation? Spoken to the government? Spoken to scientists?

Ryan Anderson:
I am always extremely skeptical of geoengineering projects because they inevitably claim to solve a problem by changing one single thing. But planets don’t work like that. There are so many interconnected factors that go into determining the climate that you can’t just drastically change one without having potentially catastrophic
consequences when other things change in response. And it’s not a linear system by any means, so you might cause a small change in one factor that is completely swamped by a resulting larger change where you least expect it.

Heather McDougal:
What would be the consequences, for example, if some rich sod decided to start terraforming the moon? Who would stop him? Or other planets — regardless of whatever ecosystems might be there? There is no interplanetary law, and probably wouldn’t be for a very long time — it would be like the old West, only weirder.

Or creating land masses/undersea kingdoms in the middle of the Pacific Ocean? Or doing something in the fragile Antarctic? Who has jurisdiction in those areas?

On another note, there is an Ursula Le Guin short story about a planet that some anthropologists land on that is incredibly infantile in its culture — cheap sex, food and drink that are awfully similar to milkshakes and hot dogs — and by the end of the story the anthropologists are beginning to have this uncomfortable belief that the planet is actually the product of an adolescent boy’s imagination (luckily the natives are beginning to move beyond that). Along the lines of individuals doing things in a loose cannon-ish way, what I keep wondering is, what happens if someone with bad ideals, or even simply cheesy or prurient ones, decides to do something drastic, based on those ideals?

What do you think?

Old McDonald Had a Planet

Old McDonald had a planet*,
And on this planet he had a…

Maybe it all starts with a planet: big, small, hot, cold, wet, dry. But a planet needs things living on it, right?

Or maybe it starts with the creatures: plants, animals, something else entirely, and they need a place to live.

Possibly you’re reading some interesting science fiction aliens, and want to know if they make sense.

It’s all about the biology. All three scenarios can be looked at for biological plausibility. We don’t yet# have any non-terrestrial biologies to examine, so I’m extrapolating a bit, but there’s a lot of physical and chemical properties involved that will have to be the same for any physical biological life forms##.

If I’m thinking about whether a fictional ecology can work, I look at three questions.

1. Where does the stuff come from? Can the living creatures get enough basic building blocks to maintain their bodies? Terrestrial life absolutely requires six elements: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur (abbreviated CHNOPS), and while it’s possible that one or more of those might be swapped for something else, those six are likely to be important to any other biologies we encounter. They are simply the most effective and appropriate elements for their roles in metabolism and genetics.

If one or more is scarce, the organisms might not be able to get very large or grow very fast, and competition for resources could be extreme. (Biology driving plot, perhaps, something I love to see in my science fiction.)

2. Where does the energy come from? The sun? Chemistry? Heat? How is it processed? Our planet runs mostly on photosynthesis, converting solar energy into usable biochemical forms. Gas giants like Jupiter radiate more heat than they receive from the Sun. This could fuel an ecology that doesn’t rely on solar energy.

Does the amount of energy available match the activity and speed of the species? Photosynthetic organisms are either small, immobile, or both, because that’s what the energy available to them supports. Terrestrial animals almost all rely on plants to concentrate energy into a more efficient form so that they can move quickly. Large fast terrestrial animals all need to breathe oxygen. Anaerobic organisms are very small and slow, and that’s likely to be universally true.

3. Do the evolutionary antecedents make sense? Could this system have developed gradually? (And if not, how was it created? Here’s another good place for story to develop.) Are there obvious relatives, and not organisms that seem entirely unlike everything else on the planet? The movie Avatar was bad at this: every animal had six legs. except the Na’vi. So how’d they lose their other pair of limbs? And why?

I don’t expect every story to meet all three points^. Sometimes that level of detail is irrelevant; sometimes it actively impedes telling the story the author intends. But a little bit of thought about how the whole ecosystem works will help avoid any glaring errors in biology, and choosing to depart from known science is a whole lot different in effect than doing through ignorance.

What do you think? Any fictional biologies that particularly annoy you, or that you think are wonderful?


* EIEIO! I had all sorts of stupid titles for this post, including: “Dammit Jim, I’m a doctor not an ecologist,” and “It’s aliiiiiveee!” Sorry**.

** Not really.

# Yet. I hope I get to see it.

## Leaving out energy-only life, and mechanical life, and some of the wilder Star Trek creatures.

^ I love Sheri Tepper’s Grass, even though it fails at least one of these.

Building the Dragon II

Part II (Part I is here)

Continuing the question: will it breathe fire?

I threw out the idea of fire-breathing being a mating display, as there isn’t any biological need for a creature to breathe fire. Let’s put aside the question of why and look at how.

Hydrogen

One commenter brought up hydrogen gas, which has the double advantage of being both flammable and lighter than air — it can be used to lighten your dragon for easier flying, whether by storing it on hollow bones or a gasbag (like a bullfrog’s throat pouch, or perhaps by going all the way to designing a zeppelin-like dragon).

However, hydrogen gas isn’t as common in nature as one might hope. Generating it by splitting water is simple — if you have electricity. Electricity-generating organs do exist in nature, of course, but most of them generate only mild fields. A small, specialized organ generating enough current to split water into component gasses could work, given a ready supply of water and enough metabolic energy to generate enough gas.

Hydrogen can be produced by some forms of algae (there has been some research on that in the bio-fuels field) but those require sunlight and the inside of a dragon is notoriously dark (or can you fix that?) Some sort of symbiotic microbe in the dragon’s gut, generating hydrogen from yesterday’s lunch, may be your best bet — your dragon gets his gas with minimal effort.

One more side note: no need for your dragon to eat rocks. Hydrogen is everywhere. It’s just a matter of separating it out.

Methane

Far less sexy than hydrogen, admittedly, but methane has the advantage of being easy to generate using existing microbes. It’s generated in the gut by bacteria which require neither light nor air, and could be accumulated in a specialized organ for siphoning back toward the head for ignition.

Or, you could be really brave and let the methane continue on its way to be expelled in the usual manner with a less-than-usual ignition organ under the tail… so that both ends of your dragon are equally dangerous… hey, it could still be a heck of a mating display.

And a non-flammable option

Acid

Hydrochloric acid, as produced in the stomachs of meat-eating animals, is quite able to burn exposed skin and eat through fabrics. More potent acids like sulfuric or nitric acid aren’t produced biologically but if one can invent a tough enough organ to store the stuff, I think it could be made quite plausible.

Unlike fire being a mating display, acid spraying makes more sense as a defensive mechanism along the lines of secreting surface poisons or explosive defecation. An acid-spraying dragon may well be short on the fangs and claws and other armaments, eat things that don’t need intensive hunting and killing, and be subject to predation by bigger, scarier monsters.

Which could be just as interesting as your standard-issue dragon, of course.

Building the Dragon

Part I (Part II is here)

Everybody loves dragons. And while wingless ones built along the lines of Komodo dragons or alligators can be a viable part of your fantasy ecosystem, let’s admit it. We want them up in the air and breathing fire or electricity or something fun.

A quick survey of existing flying creatures: the flying fox can get as large as 2.5 to 3 pounds and a wingspan of nearly four feet. The harpy eagle‘s wingspan can be 6 to 6.5 feet and they top out at 20 pounds or so.

Mind you, I would not want to meet a 20-pound dragon with a 6.5-foot wingspan, or be on the wrong side of its talons. And a hero would look really bad-ass when his pet swooped down to land on his (steel-reinforced) falconing glove.

Quetzalcoatlus scale comparison, by Matt Martyniuk (Dinoguy2), Mark Witton and Darren Naish, courtesy of Wikimedia Commons

In green, the Quetzalcoatlus northropi, with a human for comparison. Modified from a diagram featured in Witton and Naish (2008).

Let’s aim higher.

Quetzalcoatlus is the largest flying dinosaur discovered so far. Estimates vary, but it seems safe to assume a wingspan of 30 to 35 feet (9-10.5 m). Weight estimates have varied from as light as 150 to over a thousand pounds (68-453+ kg) (in a 2010 estimate generated mathematically). The first question is, of course, can this creature get into the air? Ostriches are the only current birds of similar weight — and they top out at 300 pounds.

Will it fly?

The issue was addressed by Witton and Habib in a 2010 paper on giant pterosaur flight dynamics. Their analysis of existing fossils and reconstructions of musculature led to some interesting possibilities. For their analysis, they settled on a Quetzalcoatlus of 32-36 foot (10-11 m) wingspan and 400-550 pound (180-250 kg) weight. Witton and Habib assert that these giant pterosaurs had sufficient bone strength and muscle for flying — with some mild caveats.

  • Assisted launching. The pterosaurs may have launched themselves with a strong jump followed by vigorous flapping. You can find a wide variety of birds using this strategy, especially larger ones like eagles. Others have suggested that pterosaurs may have used the running-start approach to launch or jumped off cliffs to get that initial burst of speed. Witton and Habib lean toward the jumping method, though.
  • Soaring. Rather than flapping constantly, pterosaurs may have done most of their flying by finding thermals and winds to soar on. Albatrosses and vultures do this a lot — it saves a great deal of energy, and when you’re big you need to save energy.
  • Moving on land. Pterosaurs were not built for it. But the authors theorize that they may have been able to get about by hopping/jumping (saltation, as sparrows do) and possibly bipedal walking (many birds do this — ducks, robins, hawks…).

What does it eat?

Witton and Naish wrote a 2008 paper on morphology, in which they addressed some of the questions of the morphology and ecology of giant pterosaurs, including Quetzalcoatlus. It’s good reference material, but chances are you aren’t building a dragon with a stork-like beak and a neck that’s long like a stork but less flexible — like a lizard. They lay out some reasonable options for such creatures, but a traditional dragon with a shorter muzzle, teeth, and greater neck flexibility will have more predatory options.

Bearing in mind the three rules of predators as formulated by me (and only me): 1. Don’t get hurt. 2. Don’t work too hard. 3. If it gets you food, do it. Also bear in mind that while an earth-bound predator can gorge on a kill and then slink away to digest, a flying predator can’t eat so much at once that he can’t fly away if threatened. Many small meals throughout the day are probably the best strategy.

  • Fishing. This is a perfectly good way to acquire a relatively large amount of calories with a reasonable amount of work. Given the general structure of a Quetzalcoatlus-based dragon, I would think that divebomb-style fishing (as done by ospreys and eagles) could work.
  • Carrion. It’s not glamorous, but it fulfills rules 2 and 3.
  • Traditional airborne hunting. This could be hunting birds, other dragons, or earth-bound prey, as falcons and hawks do. But bear in mind the stipulation about over-eating and the fact that it’s easier for a rabbit to hide in a forest than for a fish to hide in a lake. Hunting animals that congregate in large groups in meadows (or other open terrain) will make hunting easier… but also remember that we’re talking about a 30-foot wingspan dragon blotting out the sun. It’s difficult to miss that flying overhead, one would think. Or can you find a work-around for that?

Will it breathe fire?

Scientifically, the problem with breathing fire has always been the question why does it need to? Anne McCaffrey came up with one of the best answers (we bred them to do it) but in strict ecological terms, teeth and talons are quite sufficient for all your hunting needs. And if a feature isn’t useful to a creature’s survival, it isn’t done. Right?

Well, except for things that the opposite sex finds attractive. Such as peacock tails, silly dances, and the ability to compose sonnets.

Your mission, should you choose to accept it: imagine fire-breathing (or lightning bolts, what-have-you) as a mating display. We will get back to this in Part 2.

Leaf it to me

I live in the northeastern United States, so this time of year I think about leaves a lot. The color changes are the most obvious reason to be thinking about leaves, of course. In the autumn, the trees slow down and then stop producing chlorophyll, the green pigment needed for photosynthesis, so the yellow pigments also in the leaf become more prominent.

DSC08161

But it’s probably more complicated (and more interesting) than that: yellow leaves are a sign of disease during most of the year, so some insects are attracted to plants with yellow leaves. If a tree is already ill, it might be more vulnerable as insect food. It appears that some trees actually produce red pigments to hide the yellow pigments since the green pigments are no longer doing so, and it’s all to protect themselves from insects.

DSC08259

And it’s probably really even more complicated than that, too.

(I love science: it’s always more complicated, and we’re always wrong, but it’s so much fun to try to figure it out.)

So there’s one thing to think about when world-building: does your local plant-equivalent have seasonal changes in the coloration of its leaf-equivalents? If so, why? Does that have any other effects that matter in the ecology of the world, like attracting or repelling other organisms?

For that matter, are they green to start with? Most planets with life will need some way to convert solar energy into biochemical energy, which is what photosynthesis does. There are organisms that use geothermal energy or non-biological chemical energy, but most energy comes from the sun through photosynthesis. It seems likely that other planets will have the same energetic basis (but there’s plenty of room for speculation here).

And what else do leaves do? They’re flat so they can maximize sun exposure, and they’re thin so they can maximize gas exchange.

Except where conditions are less than ideal.

Desert plants have all sorts of leaf adaptations to make sure that they don’t lose too much moisture from that flat surface. Waxy coatings hold moisture inside, and hairs cut down on air movement across the surface of the leaf, reducing evaporation. Smaller leaves help reduce water loss too.

(Leaves have to take in carbon dioxide for photosynthesis, but that creates a way that water can be lost. Grasses and cacti have evolved different physiologies to deal with that problem, but I want to stick to shape instead of biochemistry.)

Very cold can be a lot like very dry, and some of the same leaf adaptations show up in arctic climates: hairs, waxy coatings, and especially having small leaves such as like pine needles.

Leaves in wet climates tend to have fewer teeth on the edges, while leaves from cold areas have more teeth.

In places where it’s warm and wet year-round, there isn’t usually a season when most plants lose their leaves simultaneously. In temperate climates, it’s cheaper for the plant to shed them than it is to maintain them through the winter. In seasonally-dry areas, plants might drop their leaves for the dry season, again to save resources. But in very hard environments, especially if they are low in nutrients, plants often keep their leaves year-round, even through the winter, because resources might not be available to replace them.

These are broad generalizations, and there are lots of exceptions, but for the world-builder matching leaf shape to climate can provide a quick hook for a realistic world. We’re used to certain kinds of plants in certain places, even if we don’t think about it.

Putting spruce tree-equivalents in cold areas, plants with small hairy leaves in deserts and plants with large leaves in jungles makes those areas feel right to the reader, so you can save the weird stuff for where it matters. Getting the little subtle things correct keeps from jarring the reader out of your world, and makes the big things seem more believable.

DSC08390

Spiders In Space: Our Constant Companions

Last week, I suggested a few likely inspirations for Science in My Fiction Contest entries:

  • Far-future fabrics that block radiation, clean the air and water, and deflect meteors.
  • Replacing personal items on spaceships with virtual possessions.
  • And the inevitability of man-made mischief during long journeys through space.

Here are a few more fun scientific sparks for all you Science in My Fiction contestants:

I don’t know about everyone else, but I like to get out of the city once in a while. The same will certainly be true about at least some of our space-faring descendants, and we will need systems in place to accommodate that impulse. Specifically, ecosystems. In fact, there is nothing to indicate that humans can survive in the absence of earthly ecosystems. Sure, we may travel in tin cans to the moon, asteroids, and maybe even Mars, but it’s bad for our physical and mental health. Extrapolate that over the course of generations, and the absence of natural cycles bodes ill for our chances of surviving past the edges of our original solar system, let alone reaching new stars.

Because the boundaries between different ecosystems are blurry and interdependent, it’s unlikely that we’ll be able to just select one living system to pack up and take with us. Hopefully we’ll be able to fill in the natural gaps technologically by that time, and while we’re at it, we should take care to remember that all terrestrial environments possess a soundtrack. Different species move through a given territories at different times of day and year; they have mating calls and warning cries, and those sounds have an effect on their environments. The absence of a natural soundtrack has an adverse impact on an ecosystem, including its humans, so we’d better not omit it from our packing list when the time comes to prepare for lift-off.

In spite of how often writers portray spaceships and space stations as austere, hyper-sanitary environments, they’re not. Real astronauts must take their cleaning duties very seriously, or else everyone might get sick and their instruments could fail. Part of the problem is the absence of the sort of biological checks and balances that exist on earth. It’s a bit harder for microbes and other species to run rampant on Earth because everything on the planet undergoes population control, mainly in the form of predation (with the notable exception of humans, and we’ve spread so far we’re trying to swarm new planets). Which means that as part of the ecosystems we’ll need in order to survive long space missions, we will need to bring some predators with us. Spiders are likely candidates because they have already adapted to live everywhere humans do – and many places we don’t – and depending on the species of arachnid aboard, they can prey upon pests ranging in size from gnats to sparrows.

There will be more suggestions like these as we approach the contest deadline. In the mean time, what are some of your ideas for good-but-overlooked ideas for humans making their way in the far future?

Co-Dependency, the Natural Way

Species don’t exist in a vacuum. That is, if you go nearly anywhere on this planet, you’re not going to find just one form of life. You’re going to find several, all filling different niches and frequently interacting with each other. (I say nearly because I don’t know whether the extremophile bacteria in the Earth’s crust are one species or several. I’m betting there are a range of them in any given location, given how resilient and diverse life is.)

The most familiar relationship between species is probably that of predator and prey. There’s the lion and gazelle, the wolf and the caribou, the anteater and the ant. We’re familiar with parasitism too—one species feeding off another without killing them first. It’s as easy to cast Earth parasites as villains as it is to cast predators. Parasites are often widely known, affect humans, have historical impact, or get handy evil-sounding names. Examples of the first three categories are fleas, mosquitoes, intestinal worms, ringworm, lice, and insect-born diseases such as malaria. Examples of the last one include strangler figs, vampire bats, and the zombie ant fungi that have been in the news lately.

Stargate’s Goa’uld, Spider-man’s Venom, and the xenomorph from Alien are examples of fictional parasitic antagonists. There’s a list of other made-up parasites on Wikipedia, though it’s probably incomplete. That said, I think we could go further. I’m not sure I’ve seen a bio-apocalypse or bio-thriller with protozoa or insects as a vector, though I’ve seen them with bacteria and viruses. And we shouldn’t forget the parasites that don’t affect humans. Some insects, such as wasps, lay eggs in other animals. A number of vines choke the life out of their supporting plants. Who knows what other kinds of parasites might evolve on other planets? Or if an alien parasite could use the strangling or egg-seeding techniques on humans?

Discussion of parasites leads us into other types of symbiotic relationships. (Yes, parasitism is a form of symbiosis.) There’s mutualism, where both species benefit. There’s commensalism, where one species benefits and the other is neither helped nor harmed. There’s also amensalism, where one species inhibits or kills off another but isn’t affected itself. Penicillium mold does this with some bacteria, for instance, and some plants produce substances that kill off competing plant life.

Mutualism can involve trading resources (think of nitrogen-fixing bacteria in plants), trading a service for a resource (pollinators, remora and sharks, animals dispersing seeds), or trading services (clownfish and anemones, ants nesting in trees). Humans are in mutually beneficial relationships with the bacteria in their intestines, and with domesticated animals.

Examples of commensalism include the cattle egret, which feeds off the insects stirred up by grazing cattle; barnacles, which attach to animals and plants as well as rocks and ships; plants that use other plants for support, such as orchids or moss; and hermit crabs, which use shells as housing.

Of course, the plants, animals, fungi, protozoa, and bacteria that engage in symbiotic relationships continue to evolve. They become better parasites, or better killers of parasites, or better nitrogen producers, or better protectors of their symbiotes. They’ll change size or shape or color or biochemistry. A change in one often means a change in the other. Symbiotes may even suffer a disability if their counterpart is removed. Lichen wouldn’t even exist if you separated the fungi and algae that form it, and removing a symbiote from an ecosystem could cause a cascade of species deaths and ultimately destroy the ecosystem.

Some questions that may spark a story or two:

  • What happens if you introduce an alien (let’s say, truly alien) species that becomes a parasite or other symbiote to a native organism?
  • Could you bioengineer a lifeform to enter into a symbiotic relationship with a plant/animal that needed a boost? Could you turn parasitism into mutualism?
  • Could you alter a symbiote’s genes to give it freedom? Would there ever be a circumstance where you’d want to do that?
  • What if one intelligent species was oppressing its equally intelligent symbiote for, say, eating insects instead of plant matter or having a strange physiology?
  • Since symbiotes tend to co-evolve, pick a possible resource or service that a species could provide, the crazier the better, then create a species that would make use of it. Remember that it will likely also be providing a service or resource for the other species. (E.g., a mollusk that feeds off electricity produced by electric eels; a plant that grows on a herbivore’s head and acts as a sound amplifier; an insect that cultivates a particular plant so that its eggs can hitch a ride on the seeds)