Itty Bitty City:
The Microscopic World In A Drop Of Pond Water
Modified By Marguerite A Graham from a lab in the text Modern Biology by Holt, Rhinehart and Winston,Inc. 1991
Marguerite A. Graham
Gulliver Prep School
Type of Entry:
Lesson /class activity
Type of Activity:
Hands -on activity; inquiry lab
Advanced Placement Biology
I designed this lab as a way to show the applications and use of the microscope .It gives the student practice in the determination of size under the microscope ,scientific diagramming and labelling. It also focuses the student about life in a pond , the tile: ITTY BITTY CITY is to make the activity fun and excite the students as they hunt for the members that make up this micro city. In the hunt they see that the pond is made up of producers and consumers. They can usually determine the organisms that make up the food chain. This lab could be used as an introduction to an unit on ecology. I use this lab after teaching the use of the microscope in both 9th and AP classes , in my AP class I follow this with observations of pure cultures of autotrophic and heterotrophic protists and a real fun lab, observing the feeding skills of the giants of the micro world, Stentor and Pelomyxa.
This lab is usually successful if students have their own microscope so that they can search through their sample thoroughly. Sometimes the pond water is not good enough for them to see the food chain so you can order protists and make up your own sample. I have
obtained a good culture from Wards 87w1617, it also has algae so it represents pond water,if collection is impossible.
Apart from the pond water ,the only requirements are the microscope, slides, coverslips, Protoslo or Detain both are brand names of the slowing gel methylcellulose which helps to slow fast moving ciliates. A picture key of algae , protozoans , rotifers and worms should be available to help students identify what they see. This does not have to be the major focus however, as the students are observing characteristics of living things versus non -living in their pond city, it does however make it interesting when they can identify them.
Students are required to do the observations and make diagrams and notes including the size of the different organisms in the city. The conclusion of the lab is for the student to answer questions based on the interactions they observed.
Class time is 1 to 2 class periods for the basic lab, there is no major preparation time, it is mainly taking out equipment for the students, they do the work.
This is a basic lab, introducing the microscope as the tool of the biologist by observing the micro world in pond water: ITTY BITTY CITY. This lab was modified from a lab in the Modern Biology text "Life in a drop of Pond Water" by Holt .Rhinehart and Winston. The modification adds measuring and diagramming skills to the observations.It also makes the student aware of the interrelationships in a pond ecosystem.
Itty Bitty City : The Microscopic World In A Drop Of Pond Water
Purpose: To examine the variety of living organisms in pond water.
Make wet mounts of the living culture
Put one drop of culture on slide,this is usually sufficient unless specified differently
Squeeze the bulb of the pipette firmly,BEFORE inserting into culture. Pull from the bottom
Observe the drop of pond water under Low Power to scan and find the organisms.
High Power is useful once you have found something to determine details not clear in Low Power
If the organisms are moving too fast and therefore difficult to observe; add one drop of Protoslo or Detain to a drop of culture on the slide. If this is unavailable place 2or 3 strands of cotton on the slide first then the drop of pond water. These procedures will slow the organisms.
YOU MUST BE PATIENT FINDING THEM , IT IS WORTH WHILE
Put observations on blank sheets provided
Locate and diagram at least 4 organisms,put sketch in circles drawn from petri dishes
Each diagram must have a heading ,with name of organism, as well as:
a. Beside each sketch ,write a brief description of its color, shape, as it appears to you, movement pattern, is it by cilia or flagella? and feeding if observed.
b. For each organism that you observe : look for evidence that it responds to stimuli such as light ,obstacles in its environment and record
c. Determine its size (here you apply the rules of measurement learnt in the microscope lab) Record and place next to name
To aid in identification,use keys to protists and diagrams to help identify the organisms
Put answers on a separate sheet and turn in with lab drawings and observations
Why was it necessary to begin your observation using the low power objective first?
What life characteristics did you observe in living organisms in pond water? or How did you distinguish between living and non-living matter?
From what observation can you infer that pond water organisms expend energy?
What characteristics of pond water organisms are difficult to observe in this type of investigation ?
What characteristics might be used to distinguish between plant like and animal like organisms?
Most of the one cell organisms belong to the kingdom ?
Compare your observations with your classmates, and complile a list of generalizations about organisms found in pond water.
After your observations can you determine the food chain or chains in the sample. Construct a possible food chain.