Name: ______________ Planarian Lab

Date: _______________ Asexual/sexual reproduction

 

A. Introduction

The purpose of this lab is to introduce the topic of reproduction. We will look at an organism called a planarian and observe how it reproduces. The objectives of this lab are to:

        Examine your background knowledge on reproduction

        Develop new understanding of reproduction

        Compare predictions to observations

 

 

B. Pre-lab Questions

On your own, answer the questions below.

 

1.      What do you think asexual reproduction is?

 

 

2.      What do you think sexual reproduction is?

 

 

3.      How many parent cells do you think are needed for asexual reproduction? Sexual reproduction?

 

 

 

C. Class Discussion:

Please write the definition given to you by the teacher.

 

Asexual reproduction

 

 

 

 

 

 

 

 

Sexual reproduction

 

 

 

 

 

D. Group Discussion

 

In your groups, please answer the following questions:

 

1.          Name 5 organisms that reproduce asexually?

 

 

2.          What might be some advantages and disadvantages of reproducing asexually?

 

Advantages:

 

 

 

 

 

Disadvantages:

 

 

 

 

 

3.          Why might it be beneficial for plants to reproduce asexually? How might this be done? Where?

 

 

 

 

 

 

 

 

 

4.          What are planarians?

 

 

 

 

5.          Where do they live?

 

 

 

 

6.          What are considered their anterior and posterior ends?

 

 

 

E. Lab Exercise:

 

Materials:

        Petri dish

        Planarian

        Spring Water (The planarian should come with bottle of spring water)

        Eye dropper or pipette

        Dissecting knife

        Graph paper

 

 

Please list 3 characteristics of the planarian without touching it. (Use full sentences)

 

A._________________________________________________________

 

___________________________________________________________

 

.___________________________________________________________

 

 

B._________________________________________________________

 

___________________________________________________________

 

.___________________________________________________________

 

C._________________________________________________________

 

___________________________________________________________

 

.___________________________________________________________

 


 

1.          Observe your planarian using the microscope. Sketch the planarian below. Label the anterior and posterior ends.

 

 

 

 

2.          Measure your planarian by removing some of the water from the dish and waiting for the planarian to stretch out. Measure the length of the planarian in millimeters. (Always replace the water; you can use the dish lid to transfer water to and from the planarian environment.)

 

Length: __________.

 

 

3.          Observe the planarian for five minutes. Does the planarian seem

active or passive? How does it move? Where in the dish does it spend most of its time? Make a current in the water with a pipette. How does the planarian react? Fill out the table below.

 

Description

Movement

 

Worm Location

 

Reaction to Current

 

 

 

 

 

 

 

 

4. Pour out some of the water, so that the planarian is mostly out of the water.

When it stretches out, use a razor blade to cut it cleanly in half. Replace the water and put the lid on it. Observe the two pieces of the planarian under the microscope. ****Group #1 will cut the planarian in the middle. Group #2 will cut just the tip of its tail off. Group #3 will cut right below the eye spots.

 

Group#____________

 

 

 

 

Fill in the table with your results:

 

 

Movement (observations)

Length (mm)

Sketch

Anterior End

 

 

 

Posterior End

 

 

 

 

 

F. Predicting

 

How long do you think that it will take the planarian (in days) to completely regenerate?

 

 

 

What do you think the planarian will look like after it regenerates?

 

 

 

 

 

 

 

 

 

 

 


G. Daily Logs

In your daily log please record your observations and length of the anterior and posterior ends.

 

H. Conclusion

1. Please draw below what your planarian looked like.

 

 

 

 

 


 

 

2. How does this compare to your picture in the Predicting section? Was it the same? What is different?

 

 

 

 

 

3.   What was the final length of you anterior and posterior ends? How does this compare to the initial length of the planarian in Lab Exercise question #2?

 

 

 

 

Evaluation: (The following guidelines will be used to determine your grade).

 

Each criterion is based on a point system from 1-5, 1 being the lowest possible score and 5 being the highest possible score.

 

Is the lab complete? ______

Neatness ______

 

Completed on time ______

 

Pictures were accurately

drawn and parts were labeled ______

 

Thoughtfulness of prediction

and conclusion ______

 

Total points ______