Raymond W. Brooks
Begin the unit by having the students write a paragraph on what the term “ecosystem” means to them. Save these papers for comparison of ideas at the end of the unit. You might also want to have a list of terms that will be used in the unit and ask the student to write a short definition of each to see if they are: familiar—somewhat familiar—no idea—about the meanings of the terms.
A walk around the school might be of interest at this time. Have the students take notes on what they like, do not like or are afraid of and keep them for comparison on follow up walks. Also have them write a short paragraph from their notes about the reasons for these conditions.
We will now begin our study of ecology by defining an ecosystem.
An ecosystem is defined as a system consisting of all the living (biotic) and nonliving (abiotic) factors that interact with one another in a given area. The size of the ecosystem depends on the person who is doing the investigating. After discussing these terms, show pictures to the class and have them group the biotic factors in one column and the abiotic factors in another column. By doing this exercise the student will better understand the term ecosystem.
Communities are the living parts of the ecosystem that interact with one another. This topic provides an opportunity to introduce Field Ecology. An exercise in field mapping can be introduced at this time. Break the class into groups and have each group set up a group study area outside 10 meters by ten meters. Have them draw a map of the area designating where trees, grass, paths, etc. are located. Have them look for animals or evidence of animal life in each study area and make a list of what they find. Make a list of things in the physical environment such as sun, shade, soil type, etc. and do not forget to include any human factors that affect the group study area. This will also set the stage for each group to set up a “Bottle Biology” experiment from materials in their group study area. On return trips to the group study area changes over time can be observed by recording new observations such as plant growth, insects, soil surface and any other observable change. Have the student compare them to their earlier findings.
Populations are groups of organisms of the same type, living in the same area. Activities with population density can be performed by using the number of students in the classroom and changing the dimensions of the room and having them stay within the new boundaries. Another activity would be to plant from one to seven seeds in seven different cups of the same size and observe the growth of the seeds in each container. Population densities generally vary among species living in the same area and are classified as clumped, (most common), random or uniform.
Some of the variables that affect population size are births, deaths, immigration and emigration.
Habitats are the places in which organism lives. Because different organisms have different needs there are different kinds of habitats but each must furnish food, shelter and other needs for survival.
Organisms can be producers, consumers or decomposers. The classification of the organism indicates how it will obtain its energy and interact with the other parts of the environment.
The producers are the source of the food in the ecosystem, consumers use the food directly or indirectly, and finally decomposers break down the dead organisms into simple substances.
The most important types of interactions in a community are energy flow, biogeochemical cycles and tropic levels.
Energy Flow
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ENTERS
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THROUGH
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LEAVES
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SUNLIGHT
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FOOD WEB
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—
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HEAT
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In most ecosystems, photosynthesis is the beginning of the energy flow.
chlorophyll
6CO2 + 6H2O + sunlight ——————> C6H12O6 + 6O2
This equation shows that water and carbon dioxide are used to produce sugar, where the energy is locked in to be used by the plant for its own life processes and oxygen which most organisms need to live. Oxygen gets into the atmosphere by photosynthesis of land and sea plants.
The process of photosynthesis is important as an ecosystem is not a closed system and needs this new energy to replace the energy that is lost by respiration.
Respiration is the process that takes the products of photosynthesis and uses them to produce energy.
C6H12O6 + 6O2————> 6CO2 + 6H2O + ENERGY
Biogeochemical Cycles Movement of water, carbon, + other nutrients such as nitrogen and phosphorus within the ecosystem.
Elements essential for life tend to move in cycles that move them from the environment, to organism, then back to the environment.
Nitrogen, being the most abundant gas in the atmosphere might be a good example to use for discussing cyclic behavior.
The nitrogen cycle is important to living things to make protein which is used for growth and repair/replacement of body cells.
Although 78% of our atmosphere consists of nitrogen, it cannot be used by most organisms in the free state. A process called nitrogen fixation must take place.
The nitrogen cycle allows this process to take place. If you look in most any science textbook you will find a diagram of this cycle. I suggest that you find a diagram in a text for your grade level as the diagrams can become confusing to the student because of the terminology.
The student should notice that there are many paths that can be taken during a cycle but they eventually end up back at their starting point.
Trophic Levels Number of transfer steps away from the energy input into an ecosystem.
(position in food web)
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Primary Producers
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Sunlight
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(Plants)
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Primary Consumers
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Primary Producers
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(Herbivores)
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Secondary Consumer
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Herbivores
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(Primary Carnivore)
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Teriary Consumer
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Carnivore
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(Secondary Carnivore)
We can now talk about some important types of biotic interactions that take place in a community: Mutualism—Competition—Predation—Parasitism
Mutualism
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Facultative—Both species benefit but each can live without the other.
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b.
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Obligate—Cannot survive long without the other.
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Competition
a.
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Exploitation—Equal access by all individuals to resources but differ in speed and efficiency of using the resource.
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b.
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Interference—Limit or prevent others from using the resource.
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Predation
a.
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Stable Coexistence—Predation keeps the prey population in check.
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b.
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Oscillations—Predators reproduce more slowly than their prey regardless of amount of prey available.
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Parasitism
a.
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Parasitoids—Kills host by consuming its soft tissues. Natural control over other insect populations.
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b.
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Social Parasitism—One species depends on the social behavior of another to complete its life cycle.
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After discussing the background material for this unit, we will break up into smaller groups for investigations. Each group will make a report and give recommendations on their area of study.
Water Biomes “Water, water everywhere,/Nor a drop to drink.”
After completing this section, we will be more aware of preventive measures that we can use to conserve water and reduce pollution in our everyday life.
We know water is a substance that can exist in all three phases at the same time and in the same place. We also know that water covers about 75% of the earth’s surface with about 4% being fresh water that we as humans and many other organisms need to survive. Because we live in a closed system we must learn to use this resource wisely to protect our environment and way of life.
To start this topic the group (if possible) should be allowed to do the hydrolysis of water activity to reinforce the formula H2O.
This exercise is being done so that the student can visually see and test these two gases that make up water.
After completing this activity, we will begin talking about the water cycle. To start this area of investigation, have the student do a distillation activity. Have them set up the apparatus and use a salt water solution for distillation. After completing this activity have them relate the activity to what is happening in nature. (Bottle Biology?)
We must realize that there is no “typical” aquatic ecosystem as environmental influences vary from area to area.
Before going into the field, we should locate the three major oceans and differentiate a sea from an ocean and define a sound and estuary.
It might be fun to take a water sample from the reservoir and an equal volume from Long Island Sound and let them evaporate naturally and compare the evaporite. You can also have your class make a hydrometer from a test tube and glass rod. Have Schooner Inc., bring water samples from various parts of the Sound and from different depths and have the students measure their specific gravity and try to explain why they differ. You can also add tap water to the list for testing.
Have the student realize the zones of ocean water are separated mainly by temperature. They should be able to place these zones in order starting at the surface zone, to the thermocline and finally the deep zone. They should give an example of a life form that lives in each zone and tell how it survives in that zone.
It might be of interest to them that oceanfloor topography is different than continental topography by most features being higher, deeper, and larger than features found on earth.
Ocean life can be classified into three major groups by their habits and the depth of ocean water they reside. The plankton float at or near the surface of the ocean where sunlight can penetrate. The nekton are the swimmers and finally we have the benthos that live on the ocean floor.
After we have become familiar with certain basic information about water, we should begin to look at the water biomes in our area. Because the group will be small you might want to ask another teacher or parent to help you transport your students to the various available sites.
Lentic ecosystems would probably be the best to do our fresh water ecosystem investigation. Arrangements can be made to visit the water treatment plant and sewage treatment plant for on site investigations and information. The information we should try to convey to our students is that many human activities such as the dumping of raw sewage into lakes and streams disrupt the balance but with education and commitment, harmful practices can be stopped and the balance restored.
The marine environment can be studied with the aid of Schooner Inc. They offer educational programs for studying life along the shore and in Long Island Sound. A three hour educational experience on the schooner “Quinnipiack” is very worthwhile. The students get to participate in gathering life forms and learning about their habitats and life cycles. If you are unable to get funding for some of these activities through the school or with the school partnership try having the Sound School give a lesson or two to your students.
When doing this group activity, have the students:
1.
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Research the average rainfall for this area.
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2.
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Find out who are the large consumers of water.
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3.
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Trace local sources of water pollution.
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4.
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Suggest ways to conserve water.
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5.
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Suggest ways to lower water pollution.
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6.
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Make oral or written class report.
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