an introduction

by Jason Buchheim
Director, Odyssey Expeditions


ECOLOGY- The science that treats the spectrum of interrelationships existing between organisms and their environment and among groups of organisms.
Ecology is the science that is concerned with how individual organisms and populations of organisms live together and with their environmental surroundings. 

The reason environmentalism and ecology get mixed up in the media is that the scientific basis of an endangered species problems come from studies ecologists have conducted determining the ecological relationship between the species and its deteriorating environmental conditions. The environmentalists use these studies as the backbone for reasons to protect and preserve our natural environments.

GENERAL ECOLOGY- basics and definitions
Basics of ecological understanding. 

I. Living things do not exist as isolated individuals or groups of individuals. II. All organisms interact with others of their own species, with other species, and with the physical and chemical environments that surround them. III. All organisms have an effect on each other and their surroundings. 

No living organisms exists entirely by itself, it is a part of a community organisms which interact and have effect on each other and their environment.

The organisms in an environment are grouped together at different levels.
A. Species- a natural group of actually or potentially interbreeding individuals reproductively isolated from other such groups. A species is the smallest taxonomical group of organisms that can actually breed with each other and have fertile offspring. A donkey and a mule are different species because their offspring are sterile. A miniature poodle and a great dane are the same species because their offspring would be fertile, although possibly ugly.
B. Population- all the individuals of a given species in a defined area. We are members of the population of humans on this boat, the population of humans in the British Virgin Islands, and the population of humans on this planet.
C. Community- The group of the species populations that tend to occur together in a particular geographical area. We are members of the community of species populations that live on this boat, along with the population of cockroaches under your mattresses, and funguses in your marine head, etc.
D. Ecosystem- The community or series of communities and their surrounding environment. This includes both the physical and chemical environment; that is the rocks, metals, perfumes (pheromones), water, and air.
ECOSYSTEM- Functional unit of variable size composed of living and nonliving parts, which interact. Component parts of the whole system function through a sequence of operations involving energy and the transfer of energy.
In an ecosystem, the organisms composing the populations and communities all require energy for survival. That energy can come from the sun in the case of the plants, or from food, in the case of the animals. The original source of energy in most ecosystems is the sun; the plants use the light for photosynthesis, which converts the light energy into basic sugars, which the plant uses as its food and stores in the form of sugars, starches, and other plant material. The animals derive all of their energy from the energy from plants stored in their bodies. The animals are divided into different trophic levels depending on if they eats the plants for their energy supply, if they eat the animals that ate the plants, or if they eat the animals that ate the animals that ate the plants. 

Sun-original source of energy. Captured by autotrophs {from latin, self-food}, that's plants, the primary producers. The energy is stored as food, which drives the heterotrophs {latin, different-food}, the consumers. 

Trophic Levels Producers-the plants storing the energy as food. Herbivores-the animals which eat the plants. i.e., Cows, Parrotfish, Humans. Carnivores-the animals which eat the animals which ate the plants. i.e., Coyotes, Barracuda, Humans. Second Level Carnivores- the animals which ate the first level carnivores. i.e., Bears, Sharks, Humans. Third Level Carnivores- very rare Fourth Level Carnivores- some do exist Decomposers- break down the complex organic molecules of dead organisms from all trophic levels. Mostly Bacteria, also Hagfish, funguses, etc. 

In communities worldwide, the same trophic levels exist. The species constituting each level differs geographically, and in some areas each level may have a greater or fewer number of species constituting that level. Ecologically equivalent species replace each other geographically, the species structure is variable. The trophic structure, in contrast, is a constant. 

    There once was a lady who swallowed a fly. I don't know why she swallowed the fly, I guess she will die. There once was a lady who swallowed a frog, she swallowed the frog to swallow the fly. I don't know why she swallowed the fly, I guess she will die. There once was a lady who swallowed a snake, she swallowed the snake to swallow the frog, she swallowed the frog to swallow the fly. I don't know why she swallowed the fly, I guess she will die. There once was a lady who swallowed Riki Tiki Tavi, need I go on, I bet she dies.
As energy is transferred from trophic level to trophic level, the majority is lost through heat and metabolic use. The loss is around 80% to 95%. This loss of energy explains why third level carnivores are very rare, not enough energy remains to sustain another trophic level. 

**Take home message: The closer our food source comes to the bottom trophic levels, the more Earth friendly we are. 

This is because much less grain would have to be grown if we ate cereal as our food source rather than steak. The cow supplying the steak must convert the energy from the grains into its own flesh, as well as support its body heat, walking around, and in general 'cowness'. Five to ten times as much grain must be grown if we are going to get our energy source from a grain fed cow then if we just ate the grain itself. Grain, and the land it is grown on, are not an unlimited resource. 

I. The transfer of energy through an ecosystem may follow several pathways. 
II. Each pathway transfers energy from a given source plant or plants through a given series of consumers called a "food chain". 
III. The combination of all food chains in a given ecosystem is a "food web". The food web is a summary of all the pathways by which energy moves from one level to another through an ecosystem.
In an ecosystem, there is a continual cycling back and forth between organisms and the physical environment of biologically required chemicals elements and compounds. Of these, carbon, nitrogen, and phosphorous are extremely important. 

Pool- A major receiver of an element or compound. There is continuous movement of the element or compound in and out of the pool.  

Sink- A depository of an element or compound that is not recycled. A certain amount of the chemical passes in and is not recycled. A sink can become a limiting agent on the continued growth or health of an ecosystem, unless it can be tapped again. The retapping of a sink is usually through geological action such as movement or erosion. 

Two examples of biochemical cycles: 

    A: Carbon Cycle 

    Carbon is a vital element in all life systems, it is the basis of organic chemistry and is a major part of all sugars, proteins, fats, etc. Carbon Dioxide is abundant in water in the forms of carbonic acid and bicarbonate. Plants "fix" the carbon from the water into organic compounds through the process of photosynthesis. This carbon is transferred to animals by herbivory and predation. Respiration and bacterial action return the carbon to the pool. When carbon is deposited into the skeletons of corals or the shells of mollusks, it does not return to the pool. The coral skeletons and shells are a "sink". 

    B: Nitrogen Cycle 

    Nitrogen is also a major constituent in organic chemistry found in many of the basic amino acids and a required element in photosynthesis. Air is the major pool reserve of nitrogen, but in its raw form it is unusable to most organisms. Nitrogen must first be converted into a nitrogen compound, "fixing" by plants. This is done through a symbiotic relationship between bacteria and plants. Once the bacteria and plants have "fixed" the nitrogen, the nitrogen compounds are available for all the other organisms to use in their biological processes. Community Structure- General Ecology

The species that make up the communities in ecosystems varies tremendously worldwide. While there are always the same trophic levels in every ecosystem, the species that constitute those trophic levels vary both regionally and temporally (in time). The individuals of the species are in constant competition for the limited resources in their environment. All the species in an ecosystem must deal with each other and the local environmental stresses placed upon them such as floods or droughts, changing weather patterns, fires, earthquakes, and all the other natural disaster we can think of. The different species have their particular strengths and weaknesses in regard to dealing with these environmental stresses. The group of species that are the best suited for dealing with a particular ecological stress are generally those that survive to face the next environmental stress. If a particular species survives in an environment for a long enough period of time, natural selection of its best suited individuals will make the species better adapted for its local environment. Natural selection does not remember past successes though; if the individuals of a species face changing environmental conditions that they are not adapted for, they may not survive, and the species may go extinct, to be replaced by a species that is better suited at that time for the environment. 

Two general ecological success strategies have evolved for the continued propagation of species. These strategies are known as Equilibrium and Opportunistic, and they are most concerned with how frequently the species will face environmental disturbances.  

    The Equilibrium success strategy is best suited for ecosystems with few environmental disturbances. The species which follow the equilibrium success strategy are usually the larger organisms. They have few reproductive periods per year, slow development, low death rate, are highly mobile, but they have low recruitment into and later colonization time of newly disturbed environments. As they survive in an environment for a long time, natural selection of the individuals can make the species highly adapted to their environment. In the oceans, these species are usually Lecithotrophic, with larger, fewer, more costly and less dispersed eggs. The problem with the equilibrium success strategy is when environmental stress or change does occur, its followers are not able to adapt to the stress through natural selection of the best suited individuals. The infrequent reproductive periods and slow development slows down the evolution process. The species may become extinct before it has had the opportunity to adapt to the new environment.  

    The Opportunistic success strategy is best suited for ecosystems with frequent environmental disturbances. The opportunistic species are usually small compared to the equilibrium species. They have many reproductive periods, a fast development time, a high rate of recruitment into new environments, and are the first to colonize a freshly disturbed environment. These species also face high death rates, low mobility, and have small body sizes. The high rate of reproduction and development allows these species to quickly become better adapted to new environments. In the oceans, these species are usually Planktotrophic, with smaller, more numerous, easy to produce and highly dispersed eggs. The opportunistic species are the first to find and colonize a freshly disturbed environment and enjoy early success in the environment. With their high rate of evolution, they are able to continually survive in environments which face frequent environmental stresses. If the environment does not face another environmental stress for a long time after the opportunistic species have settled, then equilibrium species will usually gain the upper hand and soon crowd out the opportunistic species. Opportunistic species have much lower juvenile and adult death rates so they are the better competitors in a non-changing environment. As soon as there is environmental stress, the opportunistic species gain the upper hand, and the battle for species survival continues.

Ecological Success Strategies
Equilibrium  Opportunistic 
Reproductive Periods -few/year +many
Development -slow +rapid
Death Rate  +low -high
Recruitment  -low +high
Colonizing Time  late early
Adult Size large small
Mobility +high -low 
Disturbance Rate  low high
In an ecosystem, each species making up the communities of organisms must deal with the other species in the communities. The individual organisms in the communities may be competing with each other for food, shelter, sunlight or other resources necessary for survival. The way that each species happens to go about getting its necessary resources and how it deals with other organisms it encounters is known as the species Niche. A Niche is the role an organism plays in a community, the sum of the characters that determine the position of an organism in its ecosystem. This includes all chemical, physical, spatial, and temporal factors required for survival of that species and which limits its distribution and growth. A niche is characteristic of a species, and no two species occupy the same niche in the same environment in the presence of each other. However, a different species may occupy the same niche in the absence of the normal occupant from that habitat. The Fundamental Niche is the range within which a species can exist. Whereas the Realized Niche is the actual distribution of the species in the real world. The Habitat is the part of the environment occupied by an animal. 
    Leibig's Law of the Minimum Each species in a community has certain tolerances with respect to environmental factors. If the limit of tolerance is exceeded in some are by a given factor (i.e.. Temperature) the species will be absent in the community.  Each species requires a certain minimum amount of materials. If the concentrations of these necessities (i.e.. Nitrate) falls below the minimum then the species disappears. The above is true even if all other factors and substances are favorable for the species. 
      **If you were living on the most beautiful sailboat in the world, full of the best food and drink available, and there were members of the opposite sex waiting on your every whim, you still could not survive if the sailboat had sunk to the bottom of the ocean and you had no scuba tank. Your minimum requirement would not be met, no air; the environment would be exceeding your bodily tolerances of relative humidity.
Generalists and Specialists 

A species fundamental niche can be wide or narrow, meaning that it can have great latitude in what kind of actual environment it can exist in, or it can have very specific needs that the environment must posses in order for the species to exist in that environment. A Generalist has a very wide fundamental niche, and can exist in many different local environments. Generalists make great opportunistic species, as their widely dispersed eggs can settle and succeed in many of the new environments they may reach. A Specialist has a narrow fundamental niche. The number of environments a specialist can occupy is much lower than that of a generalist. Specialists are often equilibrium species; a long period without environmental disasters allows them to become very well adapted to a particular environment, which can enable them to out-compete the generalists in resource allocation as long as the environmental conditions remain constant. 

    A generalist is a 'Jack of All Trades' and can do many things. 

    A Specialist is an 'Airline Pilot' who can do one thing very well.

Sometimes the 'Jack of All Trades' is better suited to a particular environment, such as being shipwrecked on a deserted island. He may be able to build a shelter and find food much better than the 'Airline Pilot', but if the 'Airline Pilot' found an airplane on the island, he would be much better suited to flying away to safety.  

There is room and need in the world for both generalists and specialists.

Some communities have only a few resident species, such as the tundra on a high mountain top. Other communities have literally hundreds of species per square meter, such as a rainforest or a coral reef. Most communities have a characteristic species structure that consists of a few numerically abundant species, known as the Dominants, and many rare species. 

Species structure in ecological communities can be measured by: 

    Species Richness: the total number of species in a community. Species Diversity: combines into a single index a measure of both the number of species [Richness] and the distribution of the total number of individuals among the species [Evenness]. 

    Richness= r= Total number of different species in a community  

    Diversity= H'= - S Pi loge Pi i=1"for all species (species 1 through species S), multiply the relative proportion of that species (Pi) times the logarithm of Pi, then add the products together and change the sign"Evenness= J= H'/ H'max= H'/ loge S, max would be 1 [perfect evenness]

Knowing an ecosystems richness and diversity is very important for understanding its complexity and health. These indexes can be compared from location to location, and a great deal of information can be inferred about the frequency and severity of the stresses placed upon the ecosystem just from the indexes. By following the indexes for a location temporally [through time] we can judge the general health change of the ecosystem.
There are two major competing schools of thought on how high species diversity can be maintained for an environment. 

EQUILIBRIUM: Species composition in a community is usually in a state of equilibrium. 

    I. High diversity is due to a large number of habitats and/or finely divided narrow niches maintained by various feedback mechanisms (i.e., Niche Diversification) 

    II. Stable nature of the physical environment allows equilibrium to be maintained.

INTERMEDIATE DISTURBANCE: Communities and species are rarely in a state of equilibrium. 
    I. High species diversity is maintained through continual or gradual environmental change and disturbance. 

    II. Promotes a changing species composition through the presence of many species that are not highly specialized.

Predictions of Intermediate Disturbance Model: 
    I. Communities which experience very frequent disturbances that kill most or all of the resident species would tend to be colonized by only those few species that happen to have the ability to attain maturity and reproduce quickly before the next catastrophic event. 

    II. Areas experiencing infrequent or small disturbances on long time intervals would also have low diversity; the most efficient competitors have had time to eliminate most or all other species and take over the community. 

    III. Only when the disturbances are intermediate in frequency does species diversity increase; enough time is available to permit establishment of a variety of slower growing and reproducing species, and the interval between disturbance events is short enough to avoid competitive exclusion. 

    **Ample evidence exists for both schools of thought, depending on the particular environment and the methods used to investigate the models. 

    ** On a global scale, our biospheres richness and diversity indexes have started into a major downward trend as we loose many species to extinction and cover vast areas with monoculture crops [crops of the same species]. This has happened five previous times in the Earths history, and is known as a major extinction event, such as the way the dinosaurs departed. Models of Community Succession.

Communities of organisms are not static units, they change in structure and composition with season and over longer periods of time. Some communities change in an orderly fashion over periods of many years until they reach a stage that perpetuates itself indefinitely as long as the climate does not change or there is no disturbance. 

There are three major models as to how this community change takes place. 

    Facilitation Model of Succession: Each community modifies the environment in turn making it suitable for the next community. Orderly change to the physical environment is known as Ecological Succession, and the terminal, persistent community is the Climax community. 
      An example of this is in a pine forest, where an area has been opened up due to fire. The first trees to settle in the opening are the aspens, which can tolerate a lot of sunlight. As the aspens grow, they provide shade for the new pine trees, which don't tolerate direct sunlight well. As the pines grow, they will out compete the aspens for the sunlight as they grow taller then them, and soon there will be only pines.
    Inhibition Model of Succession. No species is competitively superior, whichever species gets to a site first holds it against later settlers. The succession is not an orderly predictable process, and generally proceeds from short lived to long lived species. There is no climax community 

    Tolerance Model of Succession. This model is intermediate between the other two. Early colonizing species are not necessary, any species can start succession. Community change occurs as species that are more tolerant, or more competitively superior, prevail. 

    **Marine Environments tend to follow the second and third models. In many cases the initial occupier does not modify the environment to make it unsuitable for them and more suitable for subsequent organisms. They may even prevent the occupation of an area by more competitively superior organisms, and their is no climax community.

The makeup of populations, communities, and ecosystems are all regulated by various factors. 

-Environment [Climate]  
-Interactions among component species  
-Tolerance limits on population ranges  

All systems on earth are limited by the amount of energy available from the sun. This is the greatest limitation of all.  

Limits on populations 

All species possess the reproductive potential to produce much larger populations than are observed under natural conditions. Given unlimited resources, a population could quickly grow to exponential proportions. Nature has control mechanisms so that if a population explosion occurs, it is quickly reduced. 

     POPULATION CONTROLS: I. Competition II. Predation III. Parasitism IV. Disease 

    Competition: interaction among organisms for a necessary resource that exist in short supply. I. Intraspecific- among individuals of the same species II. Interspecific- among individuals of different species, usually two closely related species 
      The organisms could be competing over light, food, nutrients, water, or space, etc. 

      A. Share limited resource, both individuals are hampered, which inhibits their growth, development, and reproduction. 
      B. One excludes the other, controlling population. Competition Exclusion Principle: No two species with the same requirements can coexist in the same place at the same time. Complete competitors cannot coexist. This leads to niche diversification, where the competitors will diverge on their similar needs, a major factor in the formation of additional species. 

      As population increases, competition increases as a limited resource becomes scarcer. Increased competition increases the stress on organisms, absorbing energy used for growth and reproduction, effectively limiting populations. Population Regulation

    Predation: The consumption of one species by another. Consumer is the predator, victim the prey. 
      I. Predator may be most important factor in regulating the #'s of prey species. Removal or the predator will have a marked effect on prey population, causing it to increase dramatically. 
        i.e., The removal of coyotes from rangeland has been shown to dramatically increase the rodent population. The coyotes were the main predator limiting the rodents population; the rodents had an almost unlimited supply of food and quickly underwent a population explosion. 
      II. Predator may have little effect on prey population. The predator was not the main factor limiting the preys population. The prey may be missing other elements in its environment that prevent a population explosion. 
        In some communities, the existence of Keystone species has been shown. A keystone species is one of the most important species populations in a community; its affects are felt by most of the other populations in the community. Removal of the keystone species can cause great changes in the community structure even though most species are not the prey of the keystone species. An example of a keystone species is the seastar Pisaster ochraceus, which feeds on mussels. The removal of the seastar from the intertidal zone causes a population explosion in the mussels, which soon crowd out all the other species in the intertidal, lowering the overall species diversity.
    Parasitism and Disease: As populations expands, the opportunity for parasitism and disease greatly increases as the organisms will be living closer together, polluting their local environment with waste and competing strongly over resources. They will become weakened and highly susceptible to the effects of parasitism and disease, lowering their populations. Little is known about the specifics of these effects in the marine environment, but we all know how it is affecting man. 

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