READ ME FIRST - Wild Rose College of Natural HealingLesson 6 The Principles of Ecology All organisms...

I N T R O D U C T O R Y B I O L O G YI N T R O D U C T O R Y B I O L O G Y THE PRINCIPLES OF ECOLOGY L E S S O N 6L E S S O N 6

Wild Rose College of Natural Healing Martha J. McCallum ©2009

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The Sacred Balance: A vision of humanity’s place in nature by David Suzuki & Amanda McConnell* We are the air, the water, the soil, the sun What we do to the Earth = we do to ourselves Because we are part of the web of life The latest discoveries of science confirm The interconnectedness of all life We have been trapped in a series of false premises Believing that we are separate from nature That reason is the only route to truth That experimental science alone describes reality That spirituality is optional Let us re-examine those embedded ideas Let us re-discover a universe Where stars, clouds, forests, insects, and human beings are different aspects of a single system A universe where nothing exists alone Together we will regain the sustaining harmony Of human needs in balance With the sacred, self-renewing, living Earth. *from the animated website

Lesson 6Lesson 6 The Principles of EcologyThe Principles of Ecology

All organisms are connected, and ecology is the study of the web of relationships that connect us all together in nature. Our health depends on a healthy planet, yet our approach to science, dependence on technology, and growing urban populations are magnifying a sense of separation and lack of responsibility towards the natural world. It is from plant and animal species that we get the air we breathe, the food we eat, and the clothes we wear. Half of the oxygen in the atmosphere is replenished annually by photosynthetic plants and algae. Trees and plants protect our watersheds from soil erosion and flooding, and purify the air and water that we pollute. We are part of the web of life, and when the web is healthy, we are healthy. This philosophy has contributed to the widespread and growing interest in traditional healing methods. In “The



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Coming of Age of Ecological Medicine”, Kenny Ausubel describes this new interest and links it with a growing disillusionment with mainstream medicine as a cause of some illness. Over 100,000 deaths in the US each year are attributed to the use of properly prescribed drugs in hospitals. Incinerators of medical wastes are the largest producer of dioxin air pollution in the US. A known carcinogen, dioxins have been found in breast milk. Medical waste also includes radioactive waste and pharmaceutical pollution. Rising cancer rates are one of many indications that the web is not healthy. The first step toward a healthier future is ecological medicine – working to improve our environment as though we are a part of it.

ECOSYSTEM STRUCTUREECOSYSTEM STRUCTURE

T h e B i o s p h e r eT h e B i o s p h e r e Ecologists like to focus on systems, and the largest biological system is the biosphere. It is the thin skin of life on the planet, where air, water and land meet. In fact, all organisms consist of components of all three of these contributing spheres. Carbon found in proteins in all organisms is captured by plants from atmospheric carbon dioxide. Plants take up minerals from the soil, which find their way into our bones and other tissues. Water in our bodies comes from clouds, streams and lakes, and the moisture in our foods.

The biosphere exists from the bottom of the oceans to the tops of mountains. Life exists throughout the biosphere, but is rare at the extremes, where conditions are marginal.

The biosphere is a closed system, receiving no materials from the outside, with the exception of sunlight. This means that all materials are recycled across the planet and throughout time in endless cycles. You may have just breathed air that contained carbon molecules once exhaled by Charles Darwin. Your breath may contain carbon dioxide that will be used next week by a rice plant in Indonesia, and then the oxygen from that rice plant will be used by a small Indonesian boy.

The biosphere can be divided into distinct regions called biomes and aquatic life zones (Figure 6-1). A biome is a region with a distinct climate and characteristic plants and animals adapted to



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it. The North American continent contains seven major biomes; five are described below.

Fig 6.1 The Biomes

Starting in the frozen north is the tundra biome, a region of long, cold winters and short growing seasons. Grasses, mosses, lichens, wolves, musk oxen and other animals have adapted to the tundra. Trees cannot grow in the short growing season and because permafrost underlies the soil year round.

South of the tundra is the northern coniferous, or boreal forest. The milder climate and longer growing season allow a greater diversity and abundance of plant and animal species. This biome is characterized by coniferous trees, bears, moose, wolverine, and many more species.

East of the Mississippi River lies the temperate deciduous forest biome, characterized by an even warmer climate and more abundant rainfall. Broad-leafed trees, opossums, black bears, foxes and squirrels are some of the species found here.

West of the Mississippi, and including Calgary, Alberta, lies the grassland biome. Low rainfall and periodic drought prevent



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trees from growing here except near watercourses. Deep-rooted grasses that tolerate drought and grazing have evolved on the plains, together with coyotes, hawks, and voles.

Within the grassland biome are a number of more detailed classifications that are useful in describing the mountain park areas. These include the montane, subalpine, and alpine ecoregions. Banff and Canmore are mountain communities that lie within the montane ecoregion. The montane is characterized by open grassland hillsides with Douglas firs, trembling aspens, and lodgepole pines. The grassland communities are maintained by frequent wildfires. Wildlife species include elk, deer, bighorn sheep, wolves, cougars, fox and black and grizzly bears. This ecoregion comprises only 3% of Banff National Park, yet it supports the greatest number of wildlife species.

In the southwest, with even less rain, is the desert biome. This biome has a rich assortment of plants and animals adapted to the arid heat, including cacti, mesquite trees, rattlesnakes, and a variety of lizards.

The oceans are divided into aquatic life zones, the equivalent of biomes. Four major aquatic life zones are coral reefs, estuaries, the deep ocean, and the continental shelf.

People have adapted to life in every biome, using the natural resources and also benefiting from the microbes, plants, animal, soil, water, and air that compose the biome. Other species are also benefiting from each other.

E c o s y s t e m sE c o s y s t e m s An ecosystem consists of organisms and their environment. It could be as small as a rotting log, a pond or a grassy meadow, or as large as the biosphere. Even in a small ecosystem the number of organisms present and the number of interactions can be astounding.

Ecosystems can be divided into biotic, or living components and abiotic components. Abiotic components include the physical and chemical factors necessary for life, including sunlight, precipitation, temperature, and nutrients. To live in an ecosystem, a species must be able to survive within a range of abiotic conditions called its range of tolerance. Most individuals



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of a species live in their optimum range of tolerance, with less in the zone of ecological stress and none in the zone of intolerance. Human activity often changes these abiotic components so that some species no longer survive.

The limiting factor is the abiotic component that limits the size of a population. In dry biomes, precipitation is likely to be the limiting factor. For mountain goats in the Canadian Rockies, the cold winters keep their numbers low. When you are a practicing herbalist and a world class athlete comes to ask how she can be 1% faster in competitions, you might look for limiting factors in her nutrition!

In freshwater lakes and rivers, dissolved phosphate is a limiting factor. Phosphate concentrations are naturally low, and they are needed for plant and algae growth. When we add phosphates to water bodies from sewage treatment plants, human wastes and detergents, algae can proliferate and form dense surface mats, blocking sunlight to plants rooted to the bottom that may then die. This in turn can reduce deep oxygen levels and kill fish and other organisms.

A population is a group of organisms of one species that occupy a specific region. A population of grizzly bears would include all the normally solitary individuals that could come together to breed within their lifetimes. In any ecosystem, a network of plant, animal and microorganism populations come together to form a community.

H a b i t a t a n d N i c h eH a b i t a t a n d N i c h e An organism’s habitat is the place where it lives. An organism’s ecological niche describes its habitat and all of its relationships with its environment. This niche includes what the organism eats, what eats it, its range of tolerance for various environmental factors, and other key elements. Organisms in a community occupy the same habitat, but usually have different niches. This condition usually evolves by natural selection and limits competition within a community.

Niches often overlap, when two species in a community eat some of the same foods. Just as with humans, some competition in the natural world is a good thing that can lead to natural selection and evolution of new adaptations. The rule of



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competitive exclusion states that two species can’t occupy the same niche without one of them becoming extinct.

Understanding an animal’s niche is important because to protect the animal, we must protect the ecosystem it lives in. As human populations grow, we develop more and more land, and habitat loss is the number one cause of extinction. We have reached a level of widespread biological impoverishment, losing between 40 and 100 species each day. Humans compete with animals for many resources, such as the dwindling fish stocks in our oceans. Fish declines have reduced populations of seals, polar bears, and many other fish eating species.

E C O S Y S T E M F U N C T I O NE C O S Y S T E M F U N C T I O N Life on land and in water is possible because of one group, the producers. These are the algae and plants that capture the sun’s energy to synthesize organic foods from atmospheric carbon dioxide and water through photosynthesis, as well as some chemosynthetic organisms. These organisms feed themselves and all the organisms in the web of life.

All the rest of us are consumers. Herbivores such as deer, elk and cattle feed directly on plants. Carnivores such as cougars, wolves, and polar bears eat the herbivores, surviving on meat alone. Omnivores such as most humans and bears, subsist on a mixed diet of plants and animals. Detritivores or decomposers

feed on animal waste or the remains of plants and animals, and includes many bacteria, fungi and insects.

F o o d C h a i n s a n d F o o d W e b sF o o d C h a i n s a n d F o o d W e b s A food chain is a series of organisms that feed on the next organism in the chain (Figures 6-2 and 6-3). Grazer food chains begin with plants and algae, which are consumed by herbivores, or grazers. Herbivores may then be eaten by carnivores. Decomposer food chains begin with dead material. In ecosystems, decomposer and grazer food chains are tightly linked, with waste from the grazer food chain entering the decomposer food chain. Nutrients released by the decomposer food chain enter the soil and water and are taken up into plants at the base of the grazer food chain, creating links to each food chain.

Fig 6.2 Simplified food chain



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Food chains exist only in books and classrooms. In a community of living organisms, they are a part of a more complex network of interactions called food webs. Food webs present a complete picture of the feeding relationships in any given ecosystem.

An understanding of food webs can help predict the huge implications of a diminishing ozone layer on global food supplies. Declining ozone layers permit more ultraviolet radiation to enter the atmosphere, irradiating our skin as well as killing phytoplankton. Antarctic penguin researchers have identified dramatic declines in the populations of two penguin species, which they attribute to a decline in krill, their main food. Shrimp-like krill feed on phytoplankton, which is being damaged in the Antarctic regions where radiation is strongest. Over time or with continued ozone depletion, commercial fisheries could decline.

Trophic levels are a classification system that ecologists use to group organisms according to their feeding level. The producers are members of the first trophic level and grazers are in the second trophic level. Carnivores are in the third trophic level. Most food chains are limited to three or four trophic levels, because the food available diminishes with each higher level.

Biomass is the dry weight of living material in an ecosystem. The biomass at the first trophic level is the raw material for the second trophic level. Generally, only about 5-20% of the biomass at any one trophic level can be passed to the next level, resulting in a biomass pyramid. The number of species also declines with each level. The implication of this for humans is that we can feed a lot more people in the world with grain than with meat. If the bottom level of our food chain has 20,000 kilocalories of grains, this is enough cow feed to support one meat-eating human for one day.

N u t r i e n t C y c l e sN u t r i e n t C y c l e s Energy and nutrients both flow through webs in very different ways. Solar energy is captured by plants and algae and used to produce organic food molecules. This energy is stored in the covalent bonds of the molecules. Animals eat the plants, and break down these molecules in the mitochondria of their cells, releasing the stored solar energy to power numerous cellular

Fig 6.3 Biomagnification in food chains



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activities. During cellular respiration and other metabolic functions, this energy is lost as heat, which is radiated into the atmosphere and into outer space. This solar energy cannot be recycled.

In contrast, nutrients flow cyclically. Nutrients in the soil, air and water are first incorporated into plants and algae, then passed to animals in various food chains. Nutrients generally re-enter the environment through the excretion of wastes, the decomposition of dead organisms, or the decomposition of waste.

If the humans stay at the second level and eat the grain, then there is enough to feed ten humans for a day. Dozens of global nutrient cycles operate continuously, maintaining a balance between environmental (air, water or soil) and organismic phases. Human activities, however, can disrupt the balance of some nutrient cycles with profound implications to species survival. Two examples are the carbon and nitrogen

cycles, described below. The Carbon Cycle (Figure 6.4) describes the circulation of carbon dioxide in the environmental phase and as organic compounds in the organismic phase. Carbon dioxide is found in two reservoirs, or sinks, the atmosphere and the surface waters (oceans, lakes and rivers). Atmospheric carbon dioxide is absorbed by plants and photosynthetic protists, thus entering the organismic phase of the cycle. Organic food materials carry carbon as they travel from one trophic level up to the next. Carbon dioxide is released to the environment during cellular respiration by organisms of

the grazer and decomposer food chains.

Humans had little effect on the carbon cycle until the Industrial Revolution changed the scale of human activities. Global atmospheric carbon dioxide levels have increased 25% in the last century. Now, approximately six billion tons of excess carbon dioxide are added to the atmosphere each year. Three quarters of this is attributed to widespread combustion of fossil fuels and

Fig 6.4 Carbon cycle



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one quarter is due to deforestation. Tropical rainforest deforestation involves cutting the trees that were producing oxygen from carbon dioxide, and burning the cut trees, producing more carbon dioxide.

Global warming is the most significant result of increased carbon dioxide levels. Heat lost from the Earth’s surface is trapped by the carbon dioxide and radiated back to Earth.

The nitrogen cycle (Figure 6.5): Nitrogen is essential to all organisms as it is found in amino acids and the nucleic acids that make up DNA and RNA. The atmosphere has an abundance of nitrogen gas, N2. The only useable forms of nitrogen for most organisms are nitrates and ammonia.

Nitrogen fixation is the conversion of nitrogen gas to ammonia. This is carried out by cyanobacteria in the soil, and by a symbiotic bacteria that grows in root nodules of leguminous plants (peas, beans, clover, alfalfa, vetch, and more). Other soil bacteria convert ammonia to nitrites and then nitrates, which are used by plants to make amino acids and nucleic acids. All

consumers ultimately receive ammonia and nitrates from plants.

Decaying animal waste and remains are broken down by bacteria and fungi, providing another source of nitrates in the soil. Denitrifying bacteria in the soil convert nitrate to nitrite and then to nitrous oxide, which is released to the atmosphere as nitrogen gas.

Humans alter the nitrogen cycle in at least four ways: (1) by applying nitrogen-rich fertilizer on farmland, which can end up in waterways, (2) by disposing of nitrogen rich municipal sewage in waterways, (3) by raising cattle in feedlots adjacent to waterways, and (4) by burning fossil fuels, which release nitrogen oxides into the atmosphere. The first three activities upset the ecological balance of nitrogen in the soil and water. Nitrogen oxides from power plants, cars, and other combustion of fossil fuels are converted to nitric acid, which falls to the

Fig 6.5 Nitrogen Cycle



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ground with rain or snow as acid rain. Nitric acid changes the pH of water and soils and adds nitrogen as well.

Nitrogen, like phosphate, is a plant nutrient, stimulating the growth of aquatic plants and reducing sunlight and oxygen levels in waterbodies.

E C O S Y S T E M H O M E O S T A S IE C O S Y S T E M H O M E O S T A S I SS Human homeostasis is the internal balance that our bodies require for optimal health. We also require healthy external physical, chemical, social, and psychological environments to maintain our health. Ecosystem balance is a dynamic equilibrium that depends on the well being of many homeostatic mechanisms operating to maintain balance in the biosphere. In balanced ecosystems, populations may grow and decline, but from year to year they remain in a state of equilibrium. This balance comes from opposing forces that act on populations within an ecological system, growth factors and reduction factors.

P o p u l a t i o n G r o w t h a n d P o p u l a t i o n G r o w t h a n d E n v i r o n m e n t a l R e s i s t a n c eE n v i r o n m e n t a l R e s i s t a n c e Growth factors operate on populations to cause them to grow. They might include favourable weather, good food supplies, and a good reproductive rate. Reduction factors cause populations to decline, and might include adverse weather, lack of food, disease, and predation. These factors may also be called environmental resistance. A very large number of growth and reduction factors operate simultaneously in ecosystems.

Growth and reduction factors have abiotic and biotic components. This interaction is best illustrated by a simplified example. During wet years, grasses and other plants of the grassland biome grow well. Mice and other rodents thrive because of the abundance of food. Their increase in numbers results in an increase in the numbers of hawks and owls. With more rodents for food, more owl and hawk young will survive.

With favourable weather (abiotic growth factor), we see a shift in ecosystem balance towards more species. The rodent population



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is kept in check by the greater number of hawks and owls (biotic reduction factor). The increased number of mice may also deplete their own food supply (biotic reduction factor). A decline in the number of rodents will lead to a decline in hawks and owls (biotic reduction factor) as well as allow the over-harvested vegetation to regenerate (biotic growth factor). A harsh winter may follow, causing the mouse population to decline (abiotic reduction factor), which will in turn cause the owl and hawk populations to fall (biotic reduction factor).

This example illustrates some mechanisms that maintain balance within ecosystems. Changes in biotic and abiotic conditions and minor population fluctuations occur with great regularity in ecosystems, and they are able to maintain integrity.

Ecosystems can also show resilience to disruptions caused by human activity. For example, sewage emptied into a river increases organic nutrients, and leads to an increase in aquatic bacteria that are normally present in low concentrations. The bacteria carry out cellular respiration, taking oxygen from the water and giving off carbon dioxide. This reduces the oxygen levels in the water, and leads to a reduction in fish populations. Once the sewage nutrients have been consumed, and as long as there wasn’t so much sewage that fish populations were killed, the bacteria will decline in numbers and the fish will return to former levels.

Human populations are also susceptible to forces of nature, including avalanches, hurricanes, landslides, floods, earthquakes, drought, fire, and disease such as AIDS and influenza. Developed nations have more technology that can provide a buffer, reducing the effects of some events such as extremes of weather, drought and disease. Technology can also be seen as a double-edged sword, simultaneously providing a buffer and threatening our well-being.

D e n s i t yD e n s i t y Reduction factors are grouped as density-dependent or density-independent. Factors that are density-independent limit the growth of a population irrespective of its size or density, such as droughts, heat waves, floods, storms, tornadoes, or cold spells. A frost in the tropics will kill off whole butterfly populations, regardless of their population densities.



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Density-dependent factors cause a reduction in population size as densities rise. There are four major factors in this category, including competition, predation, parasitism, and disease. Predator-prey relationships are highly density dependent. As a prey population rises, there is increased competition for food and shelter, weakening some individuals, and forcing others to less suitable habitats. With greater numbers, predators have an easier time finding prey, and more are weakened or diseased. Thus, with more prey, there is more predation. Ecologists have also found that predators will shift their attention among prey species to the species with the densest populations.

Parasites feed on the bodies of their hosts, but it does not serve them well to kill their host. Many parasites lay eggs that are eliminated in the host’s feces. With large territories and low densities, host populations are not heavily affected. With dense populations, these parasites are quickly eaten from grass or water supplies, thus finding new hosts. Higher density populations are also more susceptible to parasitic infection since they are weakened or less healthy due to other factors, such as less food and marginal living conditions.

S u c c e s s i o nS u c c e s s i o n Ecosystem balance can be drastically upset by natural or human forces. Recovery may be possible but is usually slow. A deciduous forest that is cleared and planted with crops and then abandoned may take about 70 years to recover. This is an example of succession, a process of sequential change in which one community is replaced by another until a mature or climax ecosystem is formed. A mature ecosystem is one that has reached a state of long-term dynamic balance.

Primary successionPrimary succession occurs where no biotic community previously existed, such as when glaciers retreat or ocean floor volcanoes form new islands. A rich, tropical climax ecosystem takes tens of thousands of years to establish on a new volcanic island.

Secondary successionSecondary succession occurs where a biotic community previously existed, but was destroyed by human or natural forces, such as a forest fire. An abandoned pasture will first be invaded by hardy, sun-tolerant grasses such as crab grass. The



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diversity of grasses and other herbaceous plants will increase as seeds blow in or are carried by animals. After several decades, pine seedlings will take root and begin to grow. These sun-loving conifers will eventually provide some shade for shade-tolerant hard wood species to grow, and after they have grown large they will out-compete the pines. Seventy years later a climax hardwood forest is formed and has developed a state of dynamic equilibrium.

The above example illustrates the principal of colonizer species, such as crab grass, transitional species, such as pines, and climax species, the hardwoods. The colonizer and transitional species face low environmental resistance from competition, and favourable growth factors. The climax species change the conditions to the extent that transitional species can no longer grow.

Damaged ecosystems do not always repair themselves. In Viet Nam, Americans used Agent Orange to destroy thousands of acres of tropical forest to reduce the likelihood of ambush. The trees died and were replaced by hardy bushes that appear to prevent mature trees from establishing. Clear-cutting large areas of tropical rain forest exposes the soil to the hot sun, baking the soil in some places to the consistency of brick, and preventing colonizer species from establishing. Clear-cutting can also erode soil cover, making secondary succession impossible.

Primary succession begins with bare rock, so it requires up to 1000 years or more. On the island of Krakatoa, a volcano destroyed a tropical rain forest about a century ago. Today a forest has regrown, but contains only 80 tree species instead of 800 to 1000 tree species as found in nearby forests. Thousands of years may be required to achieve the original level of diversity.

S p e c i e s D i v e r s i t yS p e c i e s D i v e r s i t y Species diversity, the number of different species in a given community or ecosystem, is thought to contribute to the stability of an ecosystem. This theory is supported by several facts. First, extremely stable ecosystems, such as tropical rain forests, have remarkably high species diversity. In the tundra, where species diversity is very low, populations show wide oscillations. Monocultures, such as large farm fields growing one crop, are much more vulnerable to pests and disease than fields



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containing several different crops. These heteroculture fields are more vulnerable than natural grasslands that support many more species of plants and animals. The example presented earlier in this chapter about the decline in the ozone layer damaging phytoplankton and reducing krill populations is particularly threatening since there is low species diversity in Antarctica.

Some ecologists do not agree with the above arguments, and state that the tropical ecosystem is stable because climatic conditions are more constant. Similarly, the tundra and Antarctic ecosystems are exposed to a volatile climate. Despite these disagreements, we can still draw the conclusion that reducing species diversity can lead to unstable ecosystems.

T H E H U M A N E C O S Y S T E MT H E H U M A N E C O S Y S T E M

T h e H u m a n B o d y a s a n T h e H u m a n B o d y a s a n E c o s y s t e mE c o s y s t e m In mammals, our internal tissues such as our blood, brain, kidney, muscle, etc. are normally free of microorganisms. In contrast, all of our tissues that are in contact with the external environment have a mixture of microorganisms referred to as the normal flora. We live with dynamic interactions with these microorganisms, mostly of mutual benefit. We derive some nutritional benefits, but the most significant benefit for us is that these bacteria preclude colonization by harmful microorganisms.

The normal flora are specifically adapted to certain host tissues, and have developed individual mechanisms to enable them to adhere to the various surfaces. In some cases the bacteria are the ligands for receptors at the colonization sites.

The normal flora for humans varies with factors such as age, diet, and gender, but is relatively constant. It has been calculated that the normal human is host to about 1012 bacteria on the skin, 1010 in the mouth, and 1014 in the gastrointestinal tract. The respiratory and urinary tracts are also sites of an established normal flora.



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N o r m a l F l o r a o f t h e S k i nN o r m a l F l o r a o f t h e S k i n An adult has approximately two square metres of skin, with greater concentrations of bacteria around orifices and locations with more moisture such as the underarms, groin and between the toes. Most skin microorganisms are bacteria that colonize the superficial layers of the epidermis and the hair follicles. They protect against colonization by harmful skin fungi. Metabolic waste products of some bacteria may contribute to the development of certain skin cancers.

N o r m a l F l o r a o f t h e N o r m a l F l o r a o f t h e G a s t r o i n t e s t i n a l T r a c tG a s t r o i n t e s t i n a l T r a c t The mouth is a favourable habitat for a great many bacteria due to the moisture and presence of food. The mouth is host to a series of successional ecological stages, with new bacteria colonizing with the eruption of teeth and with puberty. Oral bacteria synthesize vitamins and fatty acids that contribute to human nutrition, and their presence makes it more difficult for non-indigenous species to colonize. They also stimulate the immune system to maintain a level of antibodies in the mouth that can react with pathogens.

The normal oral bacteria are also responsible for dental plaque, caries, and periodontal (gum) disease. Dental plaque can be an accumulation of bacteria on the surface of teeth up to 300-500 cells thick.

In the esophagus, bacteria can be found that have been swallowed with saliva and food. The stomach contains only a few species of bacteria that can survive its highly acidic conditions.

The small intestine contains more species of bacteria, and the large intestine significantly more again. Bacteria begin to colonize here with the newborn’s first feed, and the flora develop new successional stages with the introduction of new foods. It has been shown that breast milk allows the growth of a high percentage of bifidobacteria, providing significant health advantages. It should also be noted that newborns born through vaginal birth are exposed to bacteria in the birth canal that give them some benefits over those born by Caesarian section.



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The normal flora of the gastrointestinal tract offers many health advantages to human hosts. They secrete vitamin K and certain B vitamins; those lacking E Coli may also be vitamin K deficient. They secrete substances that inhibit colonization by non-indigenous bacteria and fungi. They are thought to stimulate the development of the caecum and lymphatic tissues. Studies have shown that they also benefit lactose tolerance, blood lipids, and offer anti-tumour properties and gastrointestinal immunity.

The main strains of probiotics used for digestive therapies include Lactobacilli (GC, acidophilus, and salivarius), Bifidobacterium bifidum, Streptococcus thermophilus, Saccharomyces boulardii, and Escherichia coli. Lactobacilli are able to survive the acidic conditions of the upper GI tract much better than Bifidobacteria, and also have better immune regulating qualities. Bifidobacteria are better at destroying pathogenic bacteria.

People with Crohn’s disease have been found to have reduced Bifidobacteria, and reduced lactobacillus in ulcerative colitis. Some studies have shown that each of these bacteria are helpful therapies for these conditions.

L e s s o n S i x R e f e r e n c e sL e s s o n S i x R e f e r e n c e s Ausubel, Kenny. 2001. The Coming of Age of Ecological

Medicine. Utne Reader May-June 2001. Beale, Bob. 2002. Probiotics: Their Tiny Worlds Are Under

Scrutiny. The Scientist: vol 16, issue 5:20. Chiras, David. 1993. Biology: The Web of Life. Vol. I & III. St.

Paul, Minn.: West Publishing. Collins, M. David and Glenn R. Gibson. 1999. Probiotics,

prebiotics, and synbiotics: approaches for modulating the microbial ecology of the gut. Am. J. Clin. Nutr. 1999:69 (suppl): 1052S-7S.



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Levine, Joseph and David Suzuki. 1993. The Secret of Life, redesigning the living world. Toronto: Stoddart Publishing Co.

Silberman, Sara. 2000. Friendly Flora: Progress Reported in

Probiotics for IBD, CCFA Sponsors Study. Crohn’s and Colitis Foundation of America, Inc.

Suzuki, David with Amanda McConnell. 1999. The Sacred

Balance, rediscovering our place in nature. Mountaineers Books. www.sacredbalance.com.

Todar, Kenneth. 1997. The Normal Flora of Animals. University

of Wisconsin Department of Bacteriology, Bacteriology 330 lecture notes. From www.bact.wisc.edu/bact330/lecturenf.

Tortora, G. and s. Grabowski. 1993. Principles of Anatomy and

Physiology. 7th edition. New York: Harper Collins.

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