Zoo Design Unit

September 30, 2005

 


TECHNOLOGY LESSON (circle one)    Yes  No

 

Title of lesson: Bacterial Prevalence and Disease

 

Length of lesson: Two fifty minute classes

 

Description of the class:

                     Name of course: Biology

                     Grade level: 9th

                     Honors or regular: regular

 

Source of the lesson:

            Parts of this lesson came from my old microbiology lab.

 

TEKS addressed:

¤112.43. Biology
(c) Knowledge and skills

(1) Scientific processes. The student, for at least 40% of instructional time, conducts field and laboratory investigations using safe, environmentally appropriate, and ethical practices. The student is expected to:

(A)  demonstrate safe practices during field and laboratory investigations

(4) Science concepts. The student knows that cells are the basic structures of all living things and have specialized parts that perform specific functions, and that viruses are different from cells and have different properties and functions. The student is expected to:

(D) identify and describe the role of bacteria in maintaining health such as in digestion and in causing diseases such as in streptococcus infections and diphtheria.

 

 

I.     Overview
Students will realize the prevalence of bacteria in and around our everyday environments by capturing, growing, and observing them.  This lesson will also provide a basis for learning safe and appropriate lab procedure.  Then, transmission and causes of disease will be discussed, among humans as well as animals, providing a foundation for the next lesson on viruses and viral transmission. 
 
II.  Performance or learner outcomes

            Students will be able to:

   

III. Resources, materials and supplies needed

                     Materials for each group:

á      Three Petri dishes with agar gel (instructor may need to prepare this ahead of time).

á      Three long cotton swabs

á      About a mL of distilled water

á      Permanent marker with which to label the dishes

                     Materials for the class:

á      Incubator

 

 

IV. Supplementary materials, handouts. (Also address any safety issues

      Concerning equipment used)

Each student will need a copy of the Disease Fact sheet. 

 

V.  Safety Considerations.  (may be N/A)

            

 

Five-E Organization

Teacher Does                    Probing Questions                                Student Does      

Engage:

Has anyone heard of the five second rule when food falls on the ground?  Do you think that is a good rule to go by?  What do we know about bacteria?     

Present the class with some fun facts about bacteria:

á    Most are minute, usually only 0.5-5.0 μm in their longest dimension.

á    Bacteria are the most abundant of all organisms

á    The name bacterium was introduced much later, meaning "small stick"

á    Overall, prokaryotes  weigh about as much as all the plants in the world -- roughly a gigaton

What are bacteria?

 

 

 

 

 

 

 

 

 

Where do bacteria live/grow?

 

Small prokaryotic organisms that lack nuclei, but have many of the other organelles—these organelles are not membrane bound like those in eukaryotes, however.  They reproduce asexually, and some are motile.

Quite literally, everywhere.  They have been found in the oceans, on land, underground, under the ocean floor, in jungles, in deserts, in houses, you name it.

**A common mistake among students is to confuse bacteria with viruses.  The teacher might take some time to mention that bacteria are very different from viruses and that viruses will be discussed in a couple of days.**

                                                   

Explore:

Divide students into groups of two or three and explain that during class we are going to see if we can discover bacteria in everyday places.  Ask students for suggestions on how they might search for bacteria.

After students have offered methods, draw them to the point that bacteria are obviously too small to be seen by the naked eye, unless there is a large quantity of them, that is, a colony, growing together.  So, to make it easy, we are going to try to grow some colonies of our own.  Give students instructions BEFORE passing out the materials.  Go over the technique of swabbing and applying to the agar gel, and ask students why such a gel maybe necessary.  (The technique is to simply dip the sterile swab in their distilled water, rub a selected area several times, and then immediately swab the agar gel in a zig zag fashion).  Tell the students that we are going to swab several common areas to see if we can discover any bacteria.  Ask them to discuss in their groups three places that might be apt to have bacteria.

***Before releasing the students to swab their areas, emphasize the fact that there are numerous bacteria and molds in the air, so they need to keep their dishes covered at all times.  This is imperative to avoid contamination.***  The teacher will need to monitor this closely throughout the activity.

 When they have written down these places, have them collect their materials and swab their three areas and transfer the bacteria to the trays (being sure to label the trays appropriately). After students have swabbed the trays, set them in the incubator overnight, and, if possible, over the weekend so that students can see the colonies developing.

 

If we donÕt have a microscope, how can we see bacteria?

 

 

 

How might you search for bacteria?

 

 

 

 

Where do you think bacteria are most prevalent? Least prevalent?

 

 

 

 

 

 

What is the purpose of the agar gel?        

 

 

 

 

How can we avoid contamination in this experiment?

We can see groups of bacteria in colonies.  They are rounded or flat colonies depending on the type of bacteria.

 

Hopefully, using this question, the students will be able to think their way into designing an experiment using the swabs and agar.

Bacteria are probably most prevalent in bathrooms and kitchens where water and food are plentiful.  Moist warm places are good for bacterial growth.  Therefore, cool dry places will probably be devoid of a lot of bacteria.

Not only does the agar gel provide nutrition for the bacteria, but it also provides a structure upon which the bacteria can grow.

Be careful with the agar plate once it is mixed, be careful not to rub the swab on surfaces besides the one being tested.  Do not sneeze, cough, etc. on the gel.  Also, keep the agar plate covered for as much of the time as possible, as there are airborne bacteria that could contaminate the experiment.

***Students may observe several different kinds of bacteria as well as mold on their plates and assume that all colonies are bacterial.  The teacher should advise the students that bacterial colonies are always rounded or flat, whereas mold colonies appear fuzzy (kind of like the mold on bread).  This should help them differentiate between the colonies present on their plates.***

    

Explain:

Begin by looking at the agar plates from the day before.  Ask students to describe what they see on the plates.  Just in case there is no noticeable growth, the teacher should bring photos of bacteria cultures.  (there are a couple of good photos-as well as several pointers on good laboratory technique- at http://faculty.uvi.edu/users/sratchf/141micro.htm )
The ensuing lecture should focus on the fact that bacteria are in fact, everywhere, and they are responsible for many of the diseases that affect human beings as well as animals.  Some diseases that result from bacterial infection are tetanus, typhoid fever, pneumonia, syphilis, cholera, foodborne illness and tuberculosis.  This is why it is important to keep zoo habitats as clean as possible, cleaning up waste, trash, not giving excess food, etc. 

Despite the many bad results of bacteria, there are some bacteria that are acutally beneficial to living things.  For example, there are many bacteria (like E. coli) that live in our digestive systems that help us break down the foods we eat. 

So, how are bacterial diseases transmitted? The mode of infection includes contact, air, food, water, and insect-borne microorganisms. 

What do you see on the agar plates?

What place had the most bacteria?  The least?

 

What are some diseases caused by bacteria?

 

Are all bacteria bad?  Can they be beneficial to life as well?

 

 

 

 

How are bacterial diseases transmitted?  What about viral diseases?

 

 

 

**The teacher might bring a poster about bacterial disease transmission from a local doctorÕs office.**

There may not be anything growing in the agar plates quite yet, but allow students to share their observations with the class.

Students could share some diseases that they have seen or even have had.

No. Bacteria are an important part of decomposing matter, making food products (cheese, yogurt, wine, etc.), and helping in our digestion.

The students will probably be familiar with most modes of transmission for both bacterial and viral diseases.

 

***Again, it might be suitable to remind students that we are discussing bacteria, not viruses, and that viruses will be covered in the next few days.***

                                               

Extend / Elaborate:

Bacteria and disease surround us.  How can we prevent them and/or cure ourselves (and our animals)?

This is a large part of what keeps doctors/pharmacies/ hospitals going.  There are a variety of ways to prevent bacterial infection, but the main one is just keeping clean.  Treating our injuries with antibiotics, treating our surroundings with antiseptics and disinfectants, and taking other antibacterial measures will decrease the risk of infection.  Once a person (or animal) is infected, it is best to treat bacterial diseases with simple antibiotics (like Penicillin).  Bacterial infections are fairly easy to treat because doctors can single out bacterial cells from our own (they are very different).

 

How do you prevent disease when bacteria is as prevalent as we have seen?

 

How can one prevent such disease in a zoo habitat?

 

 

 

 

How can these diseases be treated?

 

Careful cleaning of the surroundings and everyday items is necessary to keep the bacteria at a minimum. 

Cleaning of the zoo, picking up waste quickly, cleaning and circulating the water in the habitat, removing trash and extra food, etc.

 

Bacterial: with antibiotics, and careful observation of the animal to ensure that it is on the mend.

   

  Evaluate:

Ask the students to complete the Disease Fact Sheet for each of their animals.

Also, have the students write down the answers to two or three lessons from the lecture to turn in for a bit of extra credit.     

 

What are some of the major diseases caused by bacteria?

What are some benefits of bacteria?

What are ways to prevent and treat infections?

 

Students need to complete a Disease Fact Sheet for each of their animals.

 

Disease

Fact Sheet

 

Name:____________________________________ Date:____________________

 

Turn in one fact sheet for each of your animals.

 

Common name of animal:

 

Scientific name of animal:

 

Diseases common to this animal (take into account its home climate and surroundings):

 

 

 

 

 

 

Preventative measures for this animal:

 

 

 

 

 

History of species-wide disease (if available):

 

 

 

 

 

 

 

Costs of disease prevention and care: