THE ENVIRONMENT

Everything that affects an organism during its lifetime is collectively known as its environment. Environment is a very broad concept. For example, during its lifetime an animal such as raccoon is likely to interact with millions of other organism (bacteria, food organisms, parasites, mates, predators), drink copius amounts of water, breathe huge quantities of air, and respond to daily changes in temperature and humidity. This list only begins to describe the various components that make up the raccoon's environment. Because of this complexity, it is useful to subdivide the concept of environment into ABIOTIC (non-living) and BIOTIC (living) factors. Page 48 of ENVIRONMENTAL SCIENCE by Eldon D. Enger.

To understand more about Biotic factors visit the site below:
http://www.bcgrasslands.org/grasslands/bioticcomponents.htm

To learn more about Abiotic factors go to the link below:
http://www.usoe.k12.ut.us/curr/Science/core/earth/sciber9/Stand_2/html/2A.HTM

In a more particular sense "environment" is the general term for everything that surrounds man. It thus includes the:

• Bio-physical environment, i.e., the plants and animals as well as land and water bodies and the air around us;


• Socio-cultural environment or evryhting with which people interact; and


• Politico-economic environment in which people exchange goods and ideas.
  

The so-called environmental impacts are effects generated by activities undertaken within a certain environment. These activities may be formal, as in development projects or may be informal as in day-to-day chores of certain communities or households like grazing animals.

To appreciate more of the importance of the enviroment, an understanding of the BASIC PRINCIPLES OF ECOLOGY is highly encouraged.

ECOLOGY is the study of the relationship of organisms and their environment. It is the study of the household, taken in its most encompassing sense - including the plants, animals, microbes and people that live together as interdependent beings on earth.

WHAT IS AN ECOSYSTEM?

An ecosystem is the basic unit in ecology, and includes organisms, populations and communities, each influencing the properties of the others. It is a "complex web linking animals, plants, air, water and every other life form in the BIOSPHERE".

Visit the page below by clicking it.

http://www.abheritage.ca/abnature/Ecosystems/intro.htm

Ecosystem is a dynamic network of biological, chemical and physical interactions that sustain a community and allow it to respond to changes in environmental conditions. It connotes obligatory relationships, interdependence and causal relationships between and among the different HABITATS and NICHES of organisms.

Habitat - the place or type of place wherethe organism naturally lives within a community. Within its defined habitat, it fulfills an obligatory role or niche contributory to the total ecosystem function.

Example: Mindanao island may be reffered to as an ecosystem itself because it harbors organisms interacting within its tropical environment. It has a distinct tropical trophic structure, biotic diversity and material cycles which may be disinguishable from other islands. Inside Mindanao are tropical rainforests, savannas, grasslands, streams, ponds, lakes, mangroves and the like. By their own right, these too are ecosystems. We may refer to the whole Philippines as an ecosystem. page 21 of Environmental Education for Sustainable Development.

The niche of an organism is the functional role it has in its surroundings (its profession). An organism's niche includes everything that affects the organism and everything affected by the organism during its lifetime.

The concept of the ecological niche is an important one; it helps us to understand how organisms in an ecosystem interact with each other. The concept is described by Odum as follows:

The ecological niche of an organism depends not only on where it lives but also on what it does. By analogy, it may be said that the habitat is the organism's "address", and the niche is its "profession", biologically speaking.
Odum - Fundamentals of Ecology - W B Saunders 1959

Here are a few examples to help you understand what we mean when we (ecologists) use the term "ecological niche":
Oak trees live in oak woodlands; that's common sense. The oak woodland is the habitat. So if Odum was writing a letter to an oak tree he would address the letter to:

Sir Deciduous Oak Tree,

The Oak Forest,England,

U.K.

What do oak trees do? If you can answer that question you know the oak trees "profession" or its ecological niche. Perhaps you think that oak trees just stand there looking pretty and not doing vey much, but think about it.

Oak trees:
1. absorb sunlight by photosynthesis;
2. absorb water and mineral salts from the soil;
3. provide shelter for many animals and other plants;
4. act as a support for creeping plants;
5. serve as a source of food for animals;
6. cover the ground with their dead leaves in the autumn.

These six things are the "profession" or ecological niche of the oak tree; you can think of it as being a kind of job description. If the oak trees were cut down or destroyed by fire or storms they would no longer be doing their job and this would have a disastrous effect on all the other organisms living in the same habitat.

The Realm of Ecology

@ Ecosystem - the community of organisms and populations interacting with one another and with the chemical and physical factors making up their environment.

@ Community - populations of different plants and animals living and interacting in an area at a particular time.

@ Population - group of organisms of the same species living within a particular area.

@ Organism - any form of life including all plants and animals.

The earth has several major parts that play a role in sustaining life. We are part of what ecologists call the BIOSPHERE -organisms found near the earth's surface in parts of the athmosphere, hydrosphere and lithospohere. This collection of organisms interacting with one another and their non living environment (energy and chemicals) throughout the world is also called the ecosphere. It is composed of 2 major factors:

ABIOTIC Component:

The non living, or abiotic, components of an ecosystem include various physical and chemical factors such as:

• inorganic susbstances (involved in material cycles like nitrogen, carbon, water, etc.)
  
• organic compounds (like carbohydrates, proteins, humic substances, lipids, etc.
  
• climate regime (like rainfall, temperature, wind and other physical factors)
  
• latitude (distance from the equator)
  
• altitude (distance above sea level)
  
• nature of soil (for terrestrial ecosystems)
  
• fire (for terrestrial ecosystems)
  
• amount of suspended solid materials (for quatic ecosystems)
  

Major chemical factors affecting ecosystems are:

• level of water and air in soil


• level of plant nutrients dissolved in soil water in terrestrial ecosystems and in the water in aquatic ecosystems


• level of natural or artificial toxic substances dissolved in soil water in terrestrial ecosystems and in the water in aquatic ecosystems.


• salinity of water for aquatic ecosystems


• level of dissolved oxygen in aquatic ecosystems
  

The BIOTIC component :

The major types of organisms that make up the lving, or biotic, components of an ecosystem are usually classified as producers, consumers and decomposers. This classification is based on organisms' general nutritional habits.

PRODUCERS

Producers sometimes called autotrophs (meaning self-feeders), are organisms that can manufacture the organic compounds they use as sources of energy and nutrients. Most producers are green plants that make the organic nutrients through photosynthesis.

Check the animated process of photosynthesis at this site: Click the link below:

http://earthguide.ucsd.edu/earthguide/diagrams/photosynthesis/photosynthesis.html

The complex series of chemical reactions involved in photosythesis can be summarized as follows

Carbon Dioxide + Water -------> Glucose + Oxygen

In essence this complex process converts radiant energy from the sun into chemical energy stored in the chemical bonds that hold the atoms of glucose and other carbohydrates together. This stored chemical energy produced by photosynthesis is the direct or indirect source of food for most organisms. Most of the oxygen in the atmosphere is also a byproduct of photosynthesis. An estimated 59% of the earth's photosynthesis takes place on land and the remaining 41% in the oceans and other aquatic ecosystems.

Some producer organisms, mostly specialized bacteria, can extract inorganic compounds from their environment and convert them to organic nutrients in the absence of sunlight in the process called chemosynthesis, i.e., conversion of inorganic hydogen sulfide into the nutrients they need.

CONSUMERS

Organisms that get the nutrients and energy they require by feeding either directly or indirectly on producers are called consumers, or heterotrophs (meaning other-feeders). Some consumers feed on living plants and animals, and others feed on small fragments of dead plant and animal matter, called detritus.

Depending on their food sources, sonsumers that feed on living organisms fall into 3 major classes:

• Herbivores (plant eaters) - primary consumers, which feed directly and only on all or part of living plants. Click the link below to see photos of herbivores : http://www.qrg.northwestern.edu/projects/marssim/simhtml/info/whats-a-herbivore.html


• Carnivores (flesh eaters) - secondary consumers, which feed only on plant-eating animals (herbivores). Click the link below to se photos of carnivores: http://www.qrg.northwestern.edu/projects/marssim/simhtml/info/whats-a-carnivore.html


• Omnivores - tertiary or higher-level consumers, which feed on plants, herbivores and carnivores. Click the link below to see photos of omnivores: http://www.qrg.northwestern.edu/projects/marssim/simhtml/info/whats-an-omnivore.html
  

Consumer organisms that feed on detritus, or dead organic plant and animal matter, are known as detrivores.

There are two major classes of detrivores:

detritus feeders and decomposers:

Detritus feeders ingest fragments of dead organisms and their cast-off parts and organic wastes, e.g. crabs, earthworms and clams.

Decomposers digest dead tissue or wastes and absorb their soluble nutrients. They consist of two classes of organims:

Bacteria and Fungi

Microscopic, single- celled Bacteria and Fungi.

Bacteria and Fungi decomposers in turn are an important source of food for organisms such as worms and insects living in the soil and water.

Fungi are the foremost decomposers in wood, while bacteria do well in places or substrates where even oxygen may be limiting, such as in dead animal matter and in aquatic benthos.

ECOSYSTEM FUNCTIONS :

There are three main functions in the ecosytem based on its trophic structure, that of
a) Production - deals with the buildup of organic structures using materials from the non living environment

b) Consumption -aids in the buildup of organic structures in the body of the consumer, using materials from preformed food
c) Decomposition - deals with the degradation of organic structures.

RESPIRATION:

All organisms have the common ability to break down food (chemical energy) so the energy can be released for use. The process of unleashing bound energy for utilization is called respiration. With the aid of enzymes and oxidants, the chemical bonds in the food (glucose) snap to give off energy.
Summary chemical equation for respiration is:
CH2O + O2 (g) ---------→ CO2 + H2O + Energy released

Out of this total release energy (Et) is energy utilized (Eu) to fuel all essential functions in the organism (e.g. protoplasm buildup, reproduction, photosynthesis, locomotion, ingestion,etc.). The energy not utilized from the total energy released in dissipated from the system as heat (Enu). Expelled from the system with heat is carbon dioxide (CO2). The byproduct CO2 serves as index for decomposition in the ecosystem.

PRODUCTION:

Production is the function responsible for the accumulation of organic structures in the ecosystem. The process involves :
1. Energy is fixed from some energy source such as solar energy (photosynthesis) by autotrophs or phototrophs and from chemical compounds (chemosynthesis) by chemotrophs.
2. The byproducts of respiration, CO2 and H2O, are the raw materials used in production.
3. After the free energy is fixed, these raw materials are transformed into the the energy-rich glucose material (CH2O) resulting to the evolution of oxygen gas (O2).

CO2 + H2O ----------> CH2O + O2

CONSUMPTION -
It is the function which balances production and decomposition. It acts as the regulator, careful that production woulod not be too much and decomposition too little, or vice versa.

The chemical process in consumption involves the digestion of the ingested food material with the aid of digestive enzymes. The digestive enzymes simplify, rearrange and absorb the food materials such that animal protoplasm would thereafter synthesized.

DECOMPOSITION
It is the function responsible for the breakdown of complex structures in the ecosystem. The process of decomposition involves the presence of substrates (e.g. fallen leaves, twigs, logs, animal matter, and feces) and the secretion of degradation enzymes into the specific substrate.

In terrestrial ecosysten, aerobic decomposers such as fungi are responsible fo most of wood decomposition, while anaerobic decomposers, such as bacteria, are responsible for degradation of succulent plants and animals.

Aquatic ecosystems are expected to harbor mostly anaerobic decomposers, mainly because such habitats are limiting to oxygen.