Question

You are a scientist interested in the processes by which planarians regenerate. You would like to test the effects of different environmental perturbations on regeneration (e.g. temperature). What environmental stimuli would you test? Design experiments to test two environmental stimuli on planarian regeneration. For each, state a hypothesis and a predicted outcome if your hypothesis is true.

Answer 1

Introduction:

Planaria belongs to phylum Platyhelminthes and are a type of flat worm. Planaria are hermaphrodite. They can conduct, both sexual and asexual reproduction. Planaria can regenerate or regrow almost the entire part of the body, from specific pluripotent or stem cells (neoblasts).

Planaria also can respond to stimuli, like chemicals, drugs or food, moisture, temperature, light, touch and other kinetics, taxis, etc.

Experiment 1:

Aim: To observe the effect of temperature as external stimuli, on planarian regeneration.

Null hypothesis: There will be no difference in time for regeneration in Planaria, with the difference in temperature.

Procedure:

1. Take 5 petri plates with fresh water with planarian. For each planarian, tails are cut with clean razor.

2. The plates are maintained at different temperatures ranging from 0°C to 24°C.

3. Temperatures are correctly measured with thermometer and regulated at that value for each plate.

4. For each plate at the specified temperature, the time for regeneration is observed, in terms of number of days to regenerate.

5. A table is prepared to compare the temperature and time of regeneration.

Observation:

It is observed that the time (days) taken by Planaria to regenerate is lesser for higher temperatures.

Thus, null hypothesis may be rejected, and alternative hypothesis may be accepted, based on observation, stating the “Planarian regeneration is faster in warmer temperatures”.

Experiment 2:

Aim: To observe the effect of light as external stimuli, on planarian regeneration.

Hypothesis: There will be negative effect of light on planarian regeneration.

Procedure:

1. Take 5 petri plates with fresh water with planarian. For each planarian, tails are cut with clean razor.

2. First petri plate is exposed to light constantly for 24 hours.

3. The second petri plate is kept in dark for 24 hours.

4. The third petri plate is kept for 12 hours in light.

5. The fourth petri plate is kept for 6 hours in light.

6. The fifth petri plate is kept for 2 hours in light.

7. The observation is made in degree of regeneration with the time of exposure to light.

Observation:

The plates exposed for 24 hours in light will show that the planarian have died. Similar result may be obtained for 12 hours of constant exposure. The regeneration will be faster for plate in dark than plates kept I light for few hours.

This proves that the hypothesis is correct, and planarian regeneration have negative result with light.