Walking through the woods, I certainly feel at home. It’s like being back in the real world. I’m comfortable with the habitat and feel like the woods and I know each other. Part of this familiarity stems from my recognition of the plant and animal names. Among plants, I can identify most of the members of the community by both common name and botanical genus and species names. I’ll have to admit among animals, I go by common names only.
When Carolus Linnaeus initiated the binomial nomenclature system in 1735, he proposed that all life forms could be placed in either the plant Kingdom or the animal Kingdom. Since his time, the invention of the microscope and, more recently, RNA/DNA molecular work have added more Kingdoms and as many as three super units called Domains. Currently, a major revision of these taxonomic categories has been proposed, but, for now, three Domains are generally recognized; Bacteria, Archaea, and Eukarya. The first two Domains include unicellular bacteria with one Kingdom each – of the same name as the Domain. The third Domain includes all multicellular life forms with a nucleus in each cell. The Kingdoms in this Domain include Protista, Chromista, Plantae, Fungi, and Animalia.
It’s human nature to categorize life forms and create an order to the nature of nature. Yet, it is clear that nature doesn’t make such classifications an easy process to fulfill. Do the little differences represent just a variation of the same species, or does it necessitate a new species? Thus, the struggle between the ‘lumpers’ versus the ‘splitters’. My generation grew up understanding that a species is unique when it is unable to produce fertile offspring with any other species. This is simple no longer acceptable. Numerous species of animals can – and do – interbreed forming interspecific hybrids. Coyotes, dingo, jackals and wolves, bison and domestic cattle, brown, black and polar bear, lions and tigers, and bobcats, lynx and leopards, are just a few of the different species that produce fertile offspring.
Plant species hybridize even more readily than animal species. Well known examples of natural hybrids exist among oaks, hickories, willows, hawthorns, violets and trillium, to name a few.
Successful hybrids can evolve into new species within 50-60 generations. Numerous identified species, which before human intervention were physically isolated, are now in contact with each other and breeding successfully. Isn’t it then logical to contend that life is a genetic continuum rather than a series of self-contained species?
Identification of species is a good way to learn about nature. But, the simple description of a species; it’s habitats, life style, size and ethnobotany (medical and culinary use to humans) does not begin to address the natural relationships that occur among the various species within the forest biome, and how they work together (or in competition with each other) to create the marvelous balance that each ecosystem sustains.
In 1965, James Lovelock proposed the Gaia Hypothesis. This theory suggests that all the life forms on Earth function like a super-organism, modifying the environment through growth and metabolism in ways that maintain, or regulate, the abiotic conditions (e.g., temperature, moisture, chemical content) of the world to be most favorable for their continued existence.
From this global perspective of regulatory balance, we can narrow our focus to our deciduous mixed-hardwood forest ecosystem, or even further, to, say, a stream, rock outcrop, or even the sphagnum moss ecosystem. Within each of these habitats, there are various relationships among the many species of the differing Kingdoms that work together to maximize energy consumption, species diversity, and maintain a natural homeostasis, or equilibrium – or balance – of life.
Perhaps the most prevalent example of ‘inter-Kingdom’ relationships is the lichen: a combination of an algae and a fungus working together for the benefit of both. The algae produce food for the fungus while the fungus provides a home and shelter for the algae. Another example are the mycorrhizal fungi, such as the Amanitas, Boletes, and Russelas, that grow on, or within, the vascular plant roots, extending the reach of the roots so that the plant gets added nutrients and water while the fungus receives nutrients and moisture from the plant roots.
But it gets more interesting. For example, it’s the bacteria in the termite’s gut that digests the wood for the termite. And, it’s the bacteria in the cow’s gut that helps digest the grasses, producing the methane gas as a waste product of its metabolism that we all smell so well. (These bacteria are the same found in anaerobic muds in swamps that produce methane gases, which allegedly ignite, creating the infamous swamp gases.)
Some trees, whose leaves are being eaten by insects, can release hormones that attract parasitic wasps that can parasitize the leaf-eating culprits.
Woolly bear caterpillars, if attacked by parasitic flies, can switch their diet to hemlocks. The toxins in hemlock needles help the woolly bear medicate itself and stay alive, enabling it to metamorphose into Isabella moths.
Lungworms spend their lives in the guts of deer, elk and cattle. When lungworm eggs are expelled in a cow patty, the host will not browse near the excrement, thus preventing re-entrance into the host’s system. The newly hatched lungworm will crawl up certain species of fungus that also grows in cow pies and wait for the fungus to catapult itself six feet in to the air, well beyond the ring of repugnance and into fresh grass where the likelihood of ingestation is more likely.
There’s a sea slug that has taken genes from chloroplasts found in the algae it’s eaten and incorporated them into the slug’s own DNA, allowing the animal to photosynthesize the sun’s energy directly. There’ also a bizarre little worm that has lost its mouth, guts and excretory organs. It relies on several species of bacteria that live under its skin to feed the worm and get rid of the worm’s waste.
And then there’s a grass that grows in hot geothermal soils, but only when protected by a fungus that is infected by a virus! This is the only known case of a virus, a fungus, and a plant living together cooperatively!
But perhaps the most amazing ecosystem of species from different Kingdoms working together is the human body. Of the 100 – 200 trillion cells inside the human body, only 10 percent are actually human; the rest belong to bacteria, fungi, and other microbes. There are well over 1,000 species of bacteria that call the human body home; some are beneficial, others parasitic, but all living together in balance. For example, various bacteria flourish between the toes, in the armpits and even in the mouth whose metabolism produces byproducts that account for the smell of sweaty feet, armpit body odor and bad breath (the byproduct of the teeth bacteria actually forms the basis of plaque). There are two to four pounds of bacteria in the colon, making up a third of human feces by weight. Mites live in the follicles of eyelashes, eating dead skin, mating and breeding throughout the human life span. 182 species of bacteria make their lives on our skin, with a population of over 1 trillion bacteria.
Despite the creepy notion of the human body teeming with exotic flora and fauna, these microbes are overwhelmingly harmless or beneficial. They trigger the immune system and out compete pathogens. In fact, certain viruses are found on human placentas, and are necessary in reproduction (8 percent of the human genome are made up of remnant viruses). Just how important are human bacteria can be illustrated by the recent success of fecal transplants. In such cases where antibiotics have been heavily relied on to treat infections, the beneficial as well as detrimental bacteria have been depleted to such a low level that the body can’t survive. Only after such fecal transplants, with the introduction of the natural compliment of bacteria into the patient, can the bacteria recolonize the colon and treat the symptoms.
Perhaps what we should do is to look at our bodies as a miniature ecosystem, much like our mother Earth, where various creatures interact and live out their lives. Instead of focusing on sterilizing ourselves and our environment, we should protect the germ population, keeping them, and ourselves, healthy. That may also be good logic to apply to ticks, rattlesnakes, poison ivy and mosquitoes. Every organism has a role; every organism is a part of the whole.