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Biology 103
2003 Second Paper
On Serendip

The Diverse Landscapes of Life

Laura Wolfe

Living organisms have been found to exist in many diverse environments on this planet; places where perhaps no human had thought to look before. Sometimes life is found because of the wild imaginations of a few curious people other times it is stumbled upon nearly by accident. This paper will explore two seemingly unlikely landscapes of life, and will highlight the successes of discovering new living organisms in terms of expanding the array of possibility and our perception of the question "What is Life?"

One environment receiving a lot of attention from scientists is the bottom of the ocean. Earlier in history it was thought that no creature could survive under the immense pressure and the total darkness of the ocean. The landscape remained untouched by humans, because without that sense of possibility for life, the technology was not created to explore the area. Until finally, in 1972, studies conducted near the Galapagos Islands reported vents, or hot water plumes. Now that something unexpected had been found, curiosity, possibility and new questions arose. The search began to accelerate along with the technology. A deep-sea robot named Alvin was sent exploring and a whole array of bottom dwellers was found. There were giant worms, clams and mussels (1).

Once a community of living organisms has been found in a foreign environment, explanations will start rolling out. These hypotheses generally attempt to compare the system of life to our own systems grappling for similarities among the resources of the new landscape those we are already familiar with. For instance, in forests and jungles (environments which are very understandable to us) there are some animals that can climb or fly to the tops of the trees where the fruit is. Other animals must stay on the ground, and so they live off of fruit which has fallen out of the tree. When a few organisms were found in the depths of the sea, it was first conjectured that they ate food that floated down to them from the "lighted regions of the ocean" (1), which seems very similar to the configuration of the familiar woodland food-system. This story was adequate until it was discovered that entire "cities" of creatures were thriving down at the bottom of the ocean biologists had to come up with a new story.

There are hydrothermal vents called black smokers which let off heat and chemicals from the bottom of the ocean. Entire communities of creatures live around these vents, and it was soon discovered that chemoautotrophic bacteria use chemicals from these vents as energy, rather than sunlight which was previously thought to be essential to all living organisms and life systems. The bacteria use chemical energy from the breaking-down of hydrogen sulfide, and they are at the bottom of the food chain in this environment. Many species have been discovered in this warm underwater system including giant clams, crabs, and pink brotulid fish (2). Not only were these new species found, but entire categories had to be formed for certain creatures that fit into no pre-existing group. For instance, "a reddish worm known as vestimentiferan, which builds and lives in a tube up to 7.5 m (25 ft.) long, is so different from any other known animal that it has been classified in a phylum of its own" (2). By exploring this new landscape of life, the make-up of what we call "life" has been enhanced. The addition of new species and new categories of species means a wider spectrum of stories and explanations of life.

Even with all these discoveries, "less than 1% of the sea floor where hydrothermal vents are suspected has been investigated" (1). "One puzzle for scientists to figure out is why the chemistry of hydrothermal vents changes, not only among locations, but over temporal scales as well. Measurements of vent water taken from the time of a sea floor eruption indicate a change in the mineral composition being emitted. Scientists have also found that individual vents or entire vent fields can change anywhere from days to thousands of years" (1). So much remains to be understood about these systems, and there is an incredible probability that new creatures or new systems of life will be discovered in the depths of the seas. We simply have not been looking for very long; on the timeline of human history, these past few decades barely represent a noticeable mark, yet it embodies all we know of the bottom dwellers of the ocean.

Another set of landscapes which exist in the realm of unfamiliarity are caves. Caves seem dark, cold and lifeless to us, but to many species they provide an environment of perfect conditions. Organisms here are separated into four categories, troglobites, troglophiles, trogloxenes, and habitual trogloxenes. Troglobites are the only type that live entirely in the dark zone of a cave and cannot survive anywhere else. Troglophiles could actually live on the surface if the environment was comparable to that of a cave. Trogloxenes "occur in caves but don't complete their entire life cycles within a cave" (3), and habitual trogloxenes are only found in caves during certain periods of their life cycle.

For such a dark, unfamiliar landscape it is surprising to me how much is known about cave organisms and their life cycles. Many creatures live in puddles made by water dripping from the ceiling of a solution cave. A solution cave is actually created by water coursing through carbonate and sulfate rocks including limestone, dolomite, marble and gypsum (3). Stalactites and stalagmites can be found in these caves along with many unique species of animals. For instance, glowworms (otherwise known as fungus gnats) can be found on the ceilings and walls of some caves. When still in the larval stage, this creature glows because of a chemical called luciferin "which can be 'burned' with oxygen to produce water, carbon dioxide, and light---the exact opposite of photosynthesis" (4)).

There are creatures that survive only on the limited food sources inside the cave, however, some animals depend on outside sources being brought into the cave (especially in certain caves where plant-life is impossible). To survive in this environment, "sensory systems are adapted...Also since food is scarce in most of these caves, since plant life can't grow in the absence of light, there are metabolic changes to account for this deficit" (3). Sometimes organic matter flows into the cave when water flows in, or flows up from the ground. Other nutrients come from the guano of birds that nest in caves, such as the green-masked balaclava-bird. This "supports a thriving community of fungus and insect life, which in turn are eaten by larger organisms" (4). Bats also roost in caves, providing organic material rich in nitrates to many permanent cave-dwelling species. Therefore it seems that some connection with the outside world is necessary to many cave life-systems.

The ocean floor and the caverns of the earth have one major thing in common they are not practical environments for a human to live in. They remain mysterious although it seems that a lot of progress has been made in the exploration of these two environments, particularly caves. This is surprising because there are many different types of caves and generally they are hard to enter and explore. Perhaps we know more about caves because they incited curiosity before the bottom of the ocean ever did; we can see the entrances to caves, and we imagined what creatures might live inside them. Also, the technology did not need to come as far to begin exploring caves (not including sea caves and ice caves).

In conclusion, finding every living organism on this planet is probably impossible. Discovering every living species is probably impossible. But beginning to explore all available landscapes and accepting the possibility of finding life is an important undertaking. To find life one needs curiosity, technology, and continuous, collective observations over time. This is true in unfamiliar settings as well as familiar ones when our class explored the courtyards of the science building, treating them as foreign landscapes called Planet Nearer and Planet Farther, we were very successful with discovering living organisms and categorizing what we saw. The question "What is Life?" is better approached with a wider arena of understanding in terms of landscapes and habitats. The fact that we are discovering new organisms in unlikely places is a credit to the curiosity and the hypothesizing ability of human beings.

References

1)Information about black smokers, an in-depth site about underwater vents.
2)More information about black smokers.
3)Caves, a thorough look at caves and the different categories of cave-dwelling creatures.
4)Cave creatures, a guide to specific types of cave creatures in the Waitomo caves.


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