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ECOLOGY
Derived from Greek oikos = house, logos = study, literally = study of our home
Ecology = study of organisms and their interactions with each other and with their environment.
Population - group of individuals of the same species that interact and interbreed with each other.
Habitat - place where an organism lives.
Niche - what an organism does, its role in the environment.
(habitat = address, niche = job)
Community - group of associated species sharing a common habitat.
Ecosystem - a large group of interacting organisms together with the non-living environmental factors with which they interact.
Biome - large terrestrial complex of communities of living organisms that are characterized by distinctive vegetation and climate.
A given habitat may support a number of populations, each with their own niche. Usually partition the habitat to reduce competition for scarce resources.
Communities may alter their habitat in such a way that it can support new populations, and may become less suitable for some of the established populations. This may lead to changes in communities over time.
ECOLOGICAL SUCCESSION
Succession - progressive changes in the composition of communities over time.
Primary succession - occurs where no life is present. Pioneering organisms move in and occupy an area such as rocky outcropping, newly deposited soil (landslide), lava flows, etc. Lichens and mosses tend to be pioneer species.
Secondary succession - changes in communities following disturbance of an ecosystem. May involve new species, or re-introductions of previous species.
Climax community - stable and self-maintaining. Here, climax community is the oak-hickory forest. Part of temperate deciduous forest biome. FOOD CHAINS AND FOOD WEBS
Life depends on flow of energy through communities. Energy is captured by producers who use the energy to produce food compounds. Photosynthetic autotrophs - plants.
Primary consumers - eat the producers Secondary consumers - eat the primary consumers, and so on. Forms a chain of trophic levels. (trophos = food/feeding)
Food chain is formed. Food chain - sequential linkage from plants (primary producers) to consumers (herbivores, then carnivores) to decomposers. It is the inter-related, associated trophic levels of producers and consumers. In nature, one is more likely to see food webs. Food web - system of associated and inter-related food chains. The greater is the extent of inter-relationships, the greater is the stability of the ecosystem. The greater is the diversity seen in the food web, the greater is the ecological stability!
Remember: DIVERSITY IS STABILITY!!!
POPULATION ECOLOGY
population - group of individuals of a single species that interact and interbreed with each other.
Population density - number of individuals per unit area or per unit volume.
Biotic potential - reproductive capacity of a population, when unrestricted. It is a potential of the intrinsic rate of growth, and when plotted, forms a J-shaped curve.
Environmental resistance - all physical and biological limiting factors that prevent a species from reproducing at its maximum rate.
Environmental resistance prevents populations from growing at their biotic potential, instead populations usually grow according to a logistic (S-shaped) curve.
The population usually levels off at its carrying capacity. The carrying capacity is the maximum number of individuals that can be supported by a given habitat without loss of quality to that habitat.
BIOMES: THE VALUE OF BIODIVERSITY
On the planet earth, there is incredible biological diversity. Perhaps 30 million species of organisms live on this planet. Because habitats are so diverse, the genetic diversity among those organisms is also very large.
That genetic diversity represents a vast warehouse of potential resources as well as offering a kaleidoscope of beauty and a sense of man's place in the world. Humans have expanded into every habitat in the world and may shepherd the planet or may ruin the planet. What we do in the next 30 years may well decide what will be left for your children and their children.
If we want this genetic diversity to persist, we must maintain the habitats that foster that diversity. Is habitat diversity and genetic diversity important to us, or should we have nothing but apartments, shopping centers, and corporate farms? If we overexploit a single part of a biome so that the structure of the biome is disturbed, because of the interconnections between organisms, we stand to lose the entire biome and many additional resources.
Yet there are economic and political pressures to drain and develop the wetlands, to open the remaining old-growth forests to logging, to mine the tundra for oil, coal and minerals, to use the oceans and deserts as dumping grounds. As one example, consider what has happened to watersheds and natural waterways. What is the result of channelization of natural waterways, the removal of forests from watersheds, and the covering of acres of land with pavement and buildings? Why do we see recurring flooding in developed areas? Why are so-called 100 year floods and 500 year floods occurring so regularly?
You don't have to make a choice between jobs and the environment. It is possible to have economic development while preserving the environment. Many would claim that it is a necessity that development occur in balance with environmental protection if we are to survive as a species. Today's biomes house all of tomorrow's natural products.
There is still another side to this we have not examined much. All of our discussion has been very anthropocentric. It is extremely egotistical and arrogant to think of the earth's life forms as being nothing more than potential products for human use. We should at least consider that these life-forms have an intrinsic right to life just as much as humans. With our ability to dominate events on this planet, we have a responsibility to shepherd and nurture the planet, not exploit and ruin.
These organisms add to the natural beauty of the world. They have been an inspiration to mankind for centuries. Artists, poets, architects, have all found inspiration in nature. We can find fulfillment in ourselves by helping to maintain the beauty of the natural world and in studying and trying to understand our part in a scheme that is far greater than ourselves. Humans have been developing their sense of the aesthetic ever since they stopped being hunter-gatherers. It is part of human culture and human nature. Are we losing that quality of our humanity?
You cannot save isolated parts of a system and save the system. Everything is interconnected ecologically. Biological diversity = ecological stability.
Aquatic Ecosystems
In addition to their importance as sources of food, as breeding grounds and homes for countless organisms, below are listed some of the unique attributes of these ecosystems which may be beneficial in terms of commercial development for human use.
Freshwater Ecosystems - Often subject to freezing, these ecosystems may hold important information about unique physiological adaptations. Animals that can survive freezing may provide answers as to how we may freeze organs and tissues. Cryogenic organ banks may reduce the pressure to find organ donors when people are in critical need of transplants.
Estuaries - Here is where freshwater runs into seawater. Here we find organisms that can tolerate salt, but can live in freshwater. We may find unique mechanisms for regulation of salt balance and maintenance of metabolism. Salt tolerance mechanisms may be transferable to crops.
Salt water marshes - We find lots of nitrogen-fixing bacteria that may be important as future food sources. There are other unique bacteria and fungi whose properties we are just beginning to examine.
Ocean – This extensive ecosystem is the home to fish, sponges, corals and algae, all of which are proving to be important sources of medicines. Also we are finding pigments, neuroactive agents for medicinal uses and potential cancer cures.
These are just a few examples of the resources that we can develop if, and only if, we protect the habitats that foster their survival.
Terrestrial Ecosystems
In Table 1 you will find listed the various terrestrial biomes with descriptions of their characteristics and a brief sampling of some of the unique qualities found there.
