REVIEW QUESTIONS:

To my environmental science MWF (7-8) class, we cannot meet on Monday, June 30 because I will be attending a seminar for new teachers but you are to do the things written below and to my envi sci TTh class (8:30-10) please read the blog and answer the following questions and submit your answers or attached documents to my email add : wftorre07@gmail.com

1. How is an ecosystem different from a community?
2. Describe, in detail, the niche of a human.
3. What is the role of energy in the ecosystem?
4. What are some different trophic levels in an ecosystem?
5. Analyze an aquarium as an ecosystem. Identify the major abiotic and biotic factors. List the members of the producer, primary consumer, secondary consumer, and decomposer trophic levels.

ENERGY FLOW IN ECOSYSTEMS

Photosynthesis explains how energy from the sun is captured by green plants and used to make food. Most of this energy is used to carry on the plant's life activities. The rest of the energy is passed on as food to the next level of the food chain.






The figure at right shows energy flow in a simple food chain. At each level of the food chain, about 90% of the energy is lost in the form of heat. The total energy passed from one level to the next is only about one-tenth of the energy received from the previous organism. Therefore, as you move up the food chain, there is less energy available. Animals located at the top of the food chain need a lot more food to meet their energy needs.

The most fundamental law governing our planet's finite resources states that matter can neither be created nor destroyed. However, it can be reshaped or transformed. In converting matter from one form to anotherm energy is needed. Much human activity is devoted to the taming and transformation of matter from its "raw" or natural form into products which human beings find more convenient for their use, survival and pleasure. Such conversion has impacts on man himself, including negative impacts.

The material of the planet stays on the planet and undergoes continuous transformations through the energy provided by the earth and the sun. No form of life and no human technology can create something out of n othing and neither can anything discarded become nothing.

The laws of thermodynamics govern energy processes in biological systems. The first law of energy or thermodynamics, also known as the law of conservation of energy, states that the total amount of energy in all its forms remains constant. Thus energy is neither created nor destroyed; it can only be transformed.
Example:

When a goat eats a garden plant, the plant vanishes from sight. But the matter and chemical energy of the plant is converted to chemical energy and different forms of matter in the goat's body. In this case, matter and energy have been changed to different forms, but no matter or energy has been created or destroyed.

The second law of thermodynamics also known as the law of degradation of energy quality states that each time energy is transformed, it tends to go from a more organized and concentrated form to a less organized or more dispersed form. In this case the energy transfers are never 100% efficient. In any conversion of energy from one form to another, some of the initial energy input is always degraded to lower quality, less useful energy, usually low temperatures heat that flows into the environment. Energy can be changed in only one direction - from usable to unusable.

Example: When a car is driven, only about 10% of the high-quality chemical energy available in its gasoline fuel is converted to mechanical energy to propel the vehicle and electrical energy to run its electrical systems. The remaining 90% is degraded to low-quality heat that is released into the environment and eventually dissipated or "lost" to space.

FEEDING RELATIONSHIPS

Energy in the form of energy-rich molecules stored by the producers is taken in or eaten by a series of consumers. Ultimately any energy fixed by producers or accumulated by consumers and not used by them is released by decomposers. This feeding relationship is either by a FOOD CHAIN or a FOOD WEB.

Food chain in an ecosystem refers to the transfer of food energy from the source (e.g. plants) through a series of organisms, in a process of sequential or repeated eating and being eaten. Each time one organism eats another in the food chain, energy is transferred. For every transfer about 90% of the potential energy is lost as heat. The transfer or movement of energy is in one direction only- usually from plants to a series of animals eating each other. Man is ultimately at the highest trophic level.

Trophic level - each step in the flow of energy through an ecosystem. Producers (plants) constitute the first trophic level, and hervibores constitute the second trophic level. Carnivores that eat hervibores are the third trophic level, and carnivores that eat other carnivores are the fourth tropic level. Omnivores, parasites and scavengers occupy different trophic levels, depending on what they happen to be eating at the time. If we eat a piece of beef steak, we are at the third trophic level; if we eat rice, we are the second trophic level.

IMPORTANT POINTS:

In our last lecture we examined the creation of organic matter by primary producers. Without autotrophs, there would be no energy available to all other organisms that lack the capability of fixing light energy. However, the continual loss of energy due to metabolic activity puts limits on how much energy is available to higher trophic levels (this is explained by the Second Law of Thermodynamics). Today we will look at how and where this energy moves through an ecosystem once it is incorporated into organic matter.
Most of you are now familiar with the concept of the trophic level (see Figure 1). It is simply a feeding level, as often represented in a food chain or food web. Primary producers comprise the bottom trophic level, followed by primary consumers (herbivores), then secondary consumers (carnivores feeding on herbivores), and so on. When we talk of moving "up" the food chain, we are speaking figuratively and mean that we move from plants to herbivores to carnivores. This does not take into account decomposers and detritivores (organisms that feed on dead organic matter), which make up their own, highly important trophic pathways.

Figure 1: Trophic levels.

Food chains can be classified into two types:

• Grazing Food Chain - this starts from a green plant base from which the chain goes to grazing hervibores (the organisms eating living plants), and then to carnivores (the organisms eating animals).
• Detritus Food Chain - this goes from dead organic matter into microorganisms and then to detritus-feeding organisms (detrivores) and their predators.

Food webs - refer to the interconnected or interlocking relationships among various food chains in an ecosystem. In a food web, an organism may feed on several members of the web. In complex natural communities, organisms whose food is obtained from plants by the same number of steps are said to belong to the same trophic level.

The food pyramid constitutes the over all structure of dependency among the biotic or living elements in the ecosystem. At the lowest level of the food pyramid are the food sources (generally plants). One may even go further down and say that the base of the food pyramid constitutes organic matter that serves fertilizer or food sources.

SUMMARY:

The concepts of food chains, food web and food pyramid are important to consider in monitoring effects of activities in ecosystems. Any activity not naturally or originally part of the ecosystem would certainly cause disruptions in interactions related to taking in food.

Example: Construction of a bridge may result in river siltation that damages marine plants which are used as food by fishes. Sometimes these activities even poison fishes due to the toxic construction materials, which eventually leads to human food poisoning as man takes in fish from the food chain.

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.