Visit to a local area to document environmental assets river/forest/grassland /hill/mountain, Visit to a local polluted site-Urban/Rural/Industrial/Agricultural, Study of common plants, insects, birds, Study of simple ecosystems-pond, river, hill slopes, etc.
8.1. Introduction
Practical work, seen in a broader sense as laboratory and field work, is an essential element of science teaching. This is particularly important on what concerns Natural Science, such as the study of the environment. Theoretical approaches are limited to reading of books and relevant reference materials and only when one goes out into Nature to verify the book knowledge, the learning becomes perfect. Practicals through field and laboratory work contribute to understand many less clear conceptions, and one who does the same establishes a close relationship with the Natural Science.
The development of practical work with investigative characteristics involves the total or partial definition of the problem and/or of the variables under investigation, the design and selection of suitable observation/investigation procedures, data collection and analysis and finally, the drawing of conclusions. In an investigative activity it is necessary to consider three types of concepts:
Those which are necessary to know and comprehend in order to be able to undertake the activity,
The concepts necessary to the realization of the task and
The concepts, which are developed during the investigation itself.
The field and lab work should be developed in an articulate way such that they should not be considered totally independent but, despite some level of specificity and autonomy, they should complement each other. Each type of work can be amplified and complemented, contributing to more coherent results.
Field activities should address a specific and relevant practical problem, the participants should be organized in groups and the work should be developed as a series of well-defined activities. Initial activities should allow the participants to acknowledge their own prior considerations, provide information on the issues and the work system which will be undergone, allow the definition of basic problems and bring forth some answers/proposals that may encourage and orient subsequent work.
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The role of the teacher is to guide the discussion, to clarify unclear aspects, to provide opportunities to verify different concepts as suggested by the participants. The lab work is an area, which concerns the development of both specific activities and those, which are received through field work. In the lab/classroom, activities, which enable to simulate, reproduce and/or deepen aspects, observed outdoors might be developed. Once the activities begin, new field activities may be designed.
During field work, materials will be collected and all information on what is being observed, including new questions and possible solutions, will be retained. These will be analyzed in a broader context in which it is possible to continue, complement and/or redefine field observations. The results may even lead to further field activities. It is always possible to address issues and offer explanation to students during the field work which could not have been possible during classroom teaching.
8.2. Learning about an ecosystem
The following example reveals the way in which the lab/field activities may be designed. It relates to a project developed with a group of Students. The proposal consists of a study of a specific ecosystem – a pond. The diversity of life forms provided by the earth environment is an unquestionable and easily observable reality. Existing living beings (algae, planktons, etc.), as in every other earth environment, interact among themselves and even contribute to the evolution and changing of their habitats. Therefore, the pond is an excellent example of an ecosystem to be considered in the study. The following work proposal may be suggested to a group of students:
The study of an ecosystem (pond) through the planning and development of a group of field and lab activities. The work will include (a) collection of data on biotic and abiotic factors, (b) classification and identification of the animals and plants that constitute the ecosystem, (c) establishing interactions among the members of this biocenosis (a community of biologically integrated and interdependent plants and animals) as well as the characterization of the way in which the latter is influenced by abiotic factors.
The field work should include activities which allow the best characterization possible of the pond. Necessary observations should be recorded and relevant samples collected. A small pond may even be created in the lab, as similar as possible to the real one. The work should be followed through this simulator, enabling the collection of data complementing the field research and also the experiencing of trials, which would lead to the drawing of some conclusions concerning what might have happened in the natural environment.
During the field work, students may be encouraged to measure several crucial lab parameters such as pH, nitrates, dissolved oxygen, etc., which are considered fundamental for the ecosystem. Each group of students, with full autonomy, should be allowed to develop a location map of the study area on a topographic chart, to draw a sketch of the place indicating houses, paths, orientation, nearby vegetation areas, etc., the identification of animal and vegetable species, physical and chemical parameters measured by them. Each of the participants should be asked to record the relevant information on a field notebook on the spot. Students may collect some materials like plants, etc., and bring them to the Institution and keep them in the aquarium.
The field work may reveal the lack of consistency and validity of some measurements as well as the difficulties in characterizing systematically all observations. For example, some vegetable species might be identified in an isolated way and many of them might be hard to identify. Sometimes, it may be necessary to make a second visit to the field for verification of some of the inconsistencies of the first trip and new supporting materials may have to be collected and documentary proof in the form of photographs/videos may have to be taken. The students should be told that the understanding of the great diversity of living species that constitute the ecosystem could only be accomplished when its reality is studied in situ.
The teacher is supposed to provoke new ideas among the student groups by intentionally putting either difficult or chilly questions and ideas. Sometimes, the teachers may plan and perform activities like
The effects of the variation of nitrate concentration,
The effect of the pH in the development of zooplanktons and
The impact of an increase of the environment’s temperature on the small fish of the pond for the benefit of the students,
on the simulated pond at the institution and ask the students to record observations carefully.
At the end of every activity, the students may be asked to modify their first results on the basis of the new observations that may include the characterization of the real pond (location, living species and possible trophic relationships between them, other elements, physical and chemical parameters); the characterization of the simulated lab pond (living species and possible trophic relationships between them, other elements and physical and chemical parameters); the resemblances of both ponds, the opportunities to exert influence on the pond deduced from the results obtained by the changes imposed on the simulated pond.
8.3. Learning about Soil
Everyone knows what soil is. It will be interesting if students are asked to go to an open field and fine out for themselves about soil. A few basic questions in the process may be:
What do we use soil for? (grow food, grass, trees, flowers)
Why do we need soil? (to grow food)
What happens to the soil when there is a great amount of rainfall? (washes away into ditches, etc.)
What is it called when a large amount of soil is washed away? (erosion).
Students can then be asked to find out the causes and results of soil erosion. List the three things that may happen to rain when it hits the ground:
It may evaporate,
It may sink into the ground, and
It may flow over the land surface as runoff.
Runoff is the major cause of erosion. Whether runoff is detrimental or not depends on the plant growth in an area. Plant roots hold soil particles in place. The shape of the land also affects the amount of runoff.
The students can be asked to find out the agricultural practices that cause excessive run-off. When farmers till the land before planting, they destroy all plant growth. At this point the soil is particularly vulnerable to erosion. A drought could cause the wind to dry the soil and blow it away, or a heavy rain could wash soil away before plant growth occurs. Even after crops begin to grow, farmers cultivate rows by plowing between the rows to prevent weeds from growing, thus leaving a part of the soil exposed to the elements. Any activity that causes plant cover to be lost, leaves soil vulnerable. When a farmer cuts down trees to till the soil or when industry cuts trees for land use or when logging itself occurs, land is left unprotected and subject to erosion. Plant life can also be lost to factors such as drought, frost, pest epidemics, wind, and improper methods of irrigation which cause plants to die of salinity (waste evaporates and leaves too many minerals which cause plants to die) and water logging (too much water accumulating). Another man-caused loss of plants is due to mining. When water is allowed to flow over unprotected soil, sediments are picked up and carried with it to rivers, lakes, and reservoirs. Here the sediments filter out and cause navigation problems, decrease water holding capacity and if nutrients are in the sediment the process of eutrophication will begin. Accelerated soil erosion and the dumping of wastes that are rich in plant nutrients will speed up the filling-in process in lakes and ponds.
Sediment from farms that have used harmful pesticides and herbicides also run into the rivers and lakes. These pollutants destroy fish spawning areas, stimulate weed growth, pollute drinking water, and make water unsafe for boating, swimming, and fishing.
The annual loss for erosion damage is estimated to be thousands of rupees. On-farm damage from erosion includes lower yields of crops, higher fertilizer requirements, more difficult tillage, and higher bills for farm maintenance.
Students may be taken on a field visit to an area where erosion is a major problem and then asked to list all possible causes that make the soil there vulnerable and create other problems for the environment. Local farmers may be requested to join the students to discuss erosion problems and even an official from the Soil Conservation Department may be involved with the students to explain soil conservation measures taken up in the area and success and/or failure of the same.
The field work can be further enriched by dividing the students into three groups. Group I will prepare a simulated area of soil at a slight incline with no growth, Group II will prepare a similar area of soil with minimal vegetation (small patches of grass and weeds transplanted to simulate bushes and trees), and Group III will prepare soil with dense cover (fast growing grass seed or prepared sod). With the three types of soil tilted, pour water at the top of each and students may be asked to record what happens to the soil in each case.
8.4. Learning about damages due to logging and agricultural practices
Students may be asked to enlist things that come from the forests and that we use everyday. The lists may be divided into sub-lists based on different forest products such as wood, coal, sand and gravel, stone, clay, copper, iron ore. Wood, rocks and minerals, and food come from the soil. Taking away these from the forests can cause problems if not properly done.
As more and more wood is needed, the logging practices create problems. Loggers clear areas inside the forests. Young seedlings then grow in these patches. Such patches are not particularly disruptive to wildlife; in fact, many animals thrive on the lush new growth that sprouts up. However, much soil is lost when vegetation is removed and logging roads are built. People usually do not look for areas where the danger of erosion is minimal. Selective cutting happens when loggers harvest only those mature trees and leave the rest of the forest untouched. This approach minimizes ecological disruption. If loggers move into an area and cut selectively every twenty years or so, the most valuable commercial timber can be harvested and at the same time the quality of the natural system be preserved. However, this technique is seldom followed. Open cast mining where minerals, particularly coal are extracted by methods of surface mining disrupts landscape most extensively as the process leaves behind huge piles of rubble. The dirt piles erode and cause pollution.
Students should be asked to find out ways to prevent such damages even in open cast mining such as:
To ensure that the land can be restored before starting
To use the best available technology to minimize water pollution and disruption of streams, lakes, and flow of ground water
To restore the land so that it is useful for the same purpose for which it was used before mining and
To enquire whether the miners have paid tax that can be used to reclaim land that is destroyed.
There are many methods farmers can use to help stop erosion. Soil erosion can be reduced and soil fertility can be maintained by planting two or more different kinds of crops in a single area. This process is known as rotation. There are two basic types of rotation. Alternate year rotation involves planting crops that require nitrogen, such as corn, one year and then planting nitrogen-fixing crops in the same field the next year. Another type of rotation scheme involves the use of alternate bands of different crops in a single year. Certain crops such as hay, alfalfa, and many cereals are generally grown as cover crops in bands between row crops.
Fallowing is a method of leaving a field unplanted – resting – every few years. This helps the moisture and nutrient content of the field. Farmers are very reluctant to use this method. A method that helps prevent soil erosion on hillsides is terracing. This involves building terraces and layering on the hillside. Even if farmers are reluctant to do this, most resort to plowing along the contours of the land so each furrow becomes its own small dam or terrace. There are several different types of tillage that help control erosion.
Students may be taken on a field visit to an area where terrace cultivation is being practiced and may be asked to find out all the merits and demerits of the system relating to environmental conservation and prepare a report. They may interact with the farmers and find out from them the actual processes, difficulties and benefits.
8.5. Sampling vegetation using quadrates
A quadrate is a square frame used for sampling an area. Quadrates can be used to sample an area either systematically or randomly. The sampling strategy chosen will depend on the hypothesis being investigated. Random sampling is particularly useful if two habitats are being compared. For random sampling, every point in the sample area has an equal chance of being sampled. Systematic sampling is used to investigate changes in a habitat caused by environmental factors. The best way to measure these types of changes is to use a transact. Random sampling means that every part of the sample area has an equal chance of being sampled. If enough samples are taken, the results should be representative of the whole sample area.
The simplest way to process the results of a quadrate survey is to count the number of plants that they find in each quadrat. Where each plant is a discrete individual, such as dandelions and daisies, this is acceptable. When all the results have been collected, calculate the mean number of plants per quadrat for each of the sample areas. For a greater challenge, transform the figure for mean number per quadrat into mean number of plants per square meter.
Many grasses and other grassland plants, such as white clover, speedwell and creeping buttercup, cannot easily be counted in this way, because the edges of each plant are not immediately obvious. Instead it is easier to calculate the local frequency of the plant in each quadrat. This is more challenging. Frequency is easier to measure using a gridded quadrat. The quadrat may be divided into 100 squares. Pupils count the number of squares in which the plant is found. If a particular plant is found in 56 squares, the local frequency of the plant is 56%. Once the frequency of plants has been calculated for each quadrat, the mean frequency can be calculated in the usual way for the whole sample area. Assuming a class of 8 groups of 3 or 4 students, if each group takes 10 random samples, the total number of samples taken by the class will be 80. If you choose a 20m x 20m area to sample, and pupils take samples using 0.5m x 0.5m quadrates, this means that approximately 4%, or 20 square metres of the total sample area of 900 square metres is sampled. Although ready-made quadrates can be purchased from educational suppliers, they can easily be constructed from ropes, canes or plastic tubes. Make sure that any sharp corners are removed before use.
A useful strategy for using quadrates in the field work is outlined below.
Prepare two sets of numbered pieces of paper from 1-30. Put these into a bucket, or similar.
Put the pupils into groups of 3 or 4.
Lay two 20m measuring tapes perpendicular to each other in the study area.
Invite a pupil from one group to take a piece of paper out of the bucket. Once the paper has been replaced, he/she should walk along the tape until reaching the distance, e.g. if 14 is chosen, walk to 14m.
Invite a second pupil from the same group to do the same for the other tape.
Then they turn into the plot at a right angle to the tape and walk into the plot until they meet. They should place the quadrat here.
The pupils should wait in a queue for random numbers, and to return to the back of the queue when they have finished sampling.
8.6. Measuring Soil Hardness
Soil hardness (or soil compaction) can be measured in the field by using a metal stake or pin. These can easily be made by using knitting needles. Hold the stake out at arm’s length above the centre of the quadrat and let it fall through the fingers. Measure the depth of entry into the soil. This may seem unscientific, but it really does work if pupils take care to let the stake fall from the same height above the quadrat each time. A knitted needle is long enough to measure most soil depths. It may be useful to use indelible ink to mark depths on the side of the needle.
Alternatively, after a dry period when the soil is hard, ask pupils to apply uniform pressure to the stake at each measuring site and measure the depth it reaches into the soil. Clean the stake of soil before it is used for the next measurement.
Fig. 8.1. Soil permeability
8.7. Measuring Infiltration Rate
Infiltration rate is the speed at which water soaks down from the soil surface into the soil below. It can be measured by using an infiltration tube, which is easily constructed from simple materials.
Fig. 8.2. Infiltration tube
Use a 30 cm length of 10 cm diameter plastic pipe as the infiltration tube. Other things needed are a 30 cm ruler, a jug of water, a mallet and a piece of wood.
It is important to maintain the same ‘head’ of pressure when pouring water into the infiltration tube. Press the plastic tube down into the soil until it is buried by at least 10 cm. You may need to use a mallet and a piece of wood to hammer it into the soil. Pour enough water into the plastic tube to reach the 10 cm mark. Start the stopwatch. Stop the stopwatch when the water level has dropped to 9 cm. Now you know the time taken by that soil to allow water to infiltrate into it by 1 cm. Different soils will require different times for the same amount of infiltration.
8.8. Identifying Plants and animals
The accurate identification of plants and animals can be an obstacle to fieldwork. It is useful to restrict the number of choices to a small number. For sampling plants, sometimes it is useful with classes to spend a few minutes creating a ‘species board’. Choose the 5 commonest grassland plants (not grasses) growing at the time of sampling, and ask each group of pupils to attach with sticky tape a labelled sample of each plant (including flowers and leaves) to a wooden board. They can use this board for reference while collecting data from quadrats.
8.9. Investigating air pollution
It is often difficult to measure air pollution in the field, as often sophisticated equipment and long-term monitoring are needed to obtain worthwhile data. One way to overcome this problem is to choose an aspect of air pollution which can easily be measured and combine it with secondary data available on the Internet.
Particulate pollution (i.e. soot) adhering to tree bark can rapidly be measured using nothing more complicated than sticky tape. Immediately this introduces a number of variables, which could be investigated, such as the direction in which the bark is facing, its height off the ground and its distance from a point source of pollution.
Press the sticky side (2 cm length) of tape firmly onto the bark of the tree; leave for 10 seconds, and then remove it. Soot and other particles from the air will have adhered to the tape, along with debris such as loose bark and moss from the tree. Take two samples of particles at 1 meter above the base of the tree. Stick the samples onto the individual results sheet for the correct site.
Fig. 8.3. Sticky tape method for measuring air pollution
The sticky tape on the slides can be examined under the microscope. Make mini-quadrats by photocopying graph paper onto acetates. Lay an acetate grid over the pollution sample (sticky tape). Use random co-ordinates to locate a quadrat. Estimate and record the percentage frequency of black particulates in the chosen quadrat.
Fig. 8.4. Measuring air pollution
Repeat this estimation of particulates between 15-20 times for different quadrats, and calculate an average percentage cover of particulates for the sample site. Only soot particles should be recorded; ignore bark and moss. A hand lens may be useful.
8.10. Measuring light levels on land
It is useful to be able to measure light levels. Ideally students need a measurement of long-term variations in the amount of sunlight reaching the ground surface. However, it is to be noted that short-term variations in light levels during sampling (such as the clouds moving in front of the sun) can introduce some uncertainty into the measurements. The proportion of the sky, which is visible from the ground surface, needs also to be noted. Completely open ground with no trees will have a measurement of 100% visible sky, whereas the amount of visible sky will be almost 0% at ground level in a dense conifer plantation.
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Use a gridded 0.5 square meter quadrat. Hold the quadrat above the head, and then count the number of squares, which are mostly occupied by sky. Alternatively, make a ‘light tube’ by taping a gridded piece of acetate to the end of a tube (a cardboard toilet roll tube will do, as long as it is not raining) and look through it to measure the % visible sky.
8.11. Measuring transparency of water
Secchi disk depth is a measure of water transparency. Higher the Secchi readings are the more transparent is the water to sunlight. Lower readings indicate turbid or colored water. Clear water lets light penetrate more deeply into the water body than does murky water. This light allows photosynthesis to occur and oxygen to be produced. The rule of thumb is that light can penetrate to a depth of 1.5 to 1.7 times the Secchi disk depth.
Fig. 8.5. The Secchi Disc
The Secchi disc can be easily made and may be attached to a long rope for lowering into water. Water clarity is affected by algae, soil particles, and other materials suspended in the water. Secchi disk depth can also be used as an indicator of algal abundance and general productivity. Although it is only an indicator, Secchi disk depth is the simplest and one of the most effective tools for estimating the productivity of the water body such as a lake.
Secchi disk readings vary seasonally with changes in photosynthesis rate and, therefore, algal growth. In most lakes, Secchi disk readings begin to decrease in the spring, with warmer temperature and increased growth, and continue decreasing until algal growth peaks in the summer. As cooler weather sets in and growth decreases, Secchi disk readings increase again.
Rainstorms may also affect readings. Erosion from rainfall, runoff, and high stream velocities may result in higher concentrations of suspended particles in inflowing streams and therefore decreases in Secchi disk readings. The natural color of the water also affects the readings. Pollution tends to reduce water clarity. Watershed development and poor land use practices cause increases in erosion, organic matter, and nutrients, all of which cause increases in suspended particulates and algae growth.
To measure, lower the Secchi disc into the water until you lose sight of it, then slowly let it go a little deeper. Pull it slowly back out, watching closely for when the disc re-appears. Measure the length of the string or nylon twine to from the water surface to the disc, and use this as a measure of turbidity. The greater the length of string, the lower the turbidity – i.e. the deeper the disc is visible, the less ‘murky’ the water is.
8.12. Study of common plants, insects, birds
It is very fascinating to look into the world of the insect. The students will meet tiny creatures with tremendous strength and speed, see insects that undergo startling changes in habits and form as they grow, and learn how insects see, hear, taste, smell, and feel the world around them. The students may be asked to record the following observations:
Tell how insects are different from all other animals.
Show how insects are different from centipedes and spiders.
Point out and name the main parts of an insect.
Describe the characteristics that distinguish the principal families and orders of insects.
The students may also be given work to do the following:
Observe 20 different live species of insects in their habitat.
Make a scrapbook of the 20 insects observed in the above.
Include photographs, sketches, illustrations, and articles.
Label each insect with its common and scientific names, where possible. Share your scrapbook with your counselor.
For additional materials on the insects, the students may be advised to do Internet browsing and find out the details about each of the insects.
The following additional work can also be done:
From the scrapbook collection, three species of insects helpful to humans may be identified and similarly, five species of insects harmful to humans may be shown separately.
Find out the food and its source for each of the 20 species.
Describe some general methods of insect control.
Compare the life histories of a butterfly and a grasshopper. Tell how they are different.
Raise an insect through complete metamorphosis from its larval stage to its adult stage (e.g., raise a butterfly or moth from a caterpillar).
Students may find out which the social insects are and which are the solitary insects and distinguish between the two. Students may observe an ant colony or a beehive, and document the following:
Things that make social insects different from solitary insects.
Tell how insects fit in the food chains of other insects, fish, birds, and mammals.
Find out about three career opportunities in insect study. Pick one and find out the education, training, and experience required for this profession. Discuss this with your counselor, and explain why this profession might interest you.
It is to be noted that some insects are endangered species and are protected by federal or state law. Every species is found only in its own special type of habitat. Be sure to check in advance to be sure that you will not be collecting any species that is known to be protected or endangered, or in any habitat where collecting is prohibited. In most cases, all specimens should be returned to the location of capture after the requirement has been met.
8.13. Hiking to learn about Nature
Use your senses to explore the living and nonliving parts of an ecosystem. Students will have a chance to see trees, listen to birds, feel nature’s textures, and smell herbs in the garden. Some of the sample activities, which can be undertaken, are:
Look at and feel nature shapes, colors, and textures,
Look for animals,
Listen for nature sounds,
Smell herbs, plants, trees, decomposition
Optional: taste nature (garden herbs and veggies, edible wild plants)
The students may be asked to draw something interesting that they see in the field.
Birds and Insects
Students may be asked to discover the similarities and interdependent relationships between these two types of winged animals. The following may be taken up for observations:
Observe birds and insects feeding and flying on the trail.
Learn how both birds and insects can help control garden pests.
A few sample activities may include:
Looking for Predators and prey games
Bird watching and identification
Learning about bird and insect adaptations and behavior
Insect hide and seek
Caterpillar camouflage
Looking for soil insects
Discussions of biological pest control (birds eat insects and rodents, insects eat other insects)
Discussions of the effects of pesticides on bird and insect populations and health
Additional activities may include:
Discovering what owls eat by dissecting owl pellets. Learn about the habits and habitats of these amazing birds and how they help us to control rodent populations.
Observe birds and identify them with binoculars and field guides. Find out how to attract these feathered friends to your backyard, and which birds to look for each season.
Learn how plants, insects, and birds interact with each other. Discover which plants provide excellent bird habitat and how to design an attractive, bird-friendly garden.
8.14. Native Plants and Animals
The purpose of observing natural plants and animals is to
Become familiar with how plants and animals adapt in order to survive.
Find out the role you may play in a food chain and the food webs that exist around you in nature.
Learn the natural history behind many of our native species.
A few sample activities in this case may include:
Adaptation demonstrati
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