Some fantastic jelly-fish answers

Do you think that the polyp form or the medusa form was the common stage in the cnidarian ancestor? Explain your answer.

-Ancestors must have come up with a plan where conditions were tough to avoid extinction- produce medusa
-Polyps come up with a very clever plan
-Scientifically it is more ethical to say the polyp stage is common to the ancestor cnidaria.

Compare and contrast the feeding behaviour of Hydra and Planaria.

-Hydra-hostile, Planaria-gracile
-Planaria are autotrophic
-Planaria embark on a journey for food.
-Planaria have a blood circulatory system.
-They have a blood transport system so that you can live on land.
-In conclusion the feeding behaviour has been compared and contrasted and a summary (in table form) has been made for convenience.
-The planarians outer layer is very choosy in allowing diffusion of gases.

Instead of having pluripotent cells, would it have been better for these phyla to have specialised cells or a blood transport system? Justify your answer (5 marks)

-Pluripotent cells might forget about producing sex cells
-The cells will able to focus in their function if they are for protection and wont have to sense as pluripotent cells would to know what’s wrong they just perform the function immediately after realising the problem,.

When tests go wrong

20% of my students misinterpreted the essay question on "Taxonomy as destiny" and wrote pages of crap about "Taxonomy as DENSITY".


*Slaps forehead in dispair*


There is only so much you can help them (the essay counted 60% of the test mark allocation too...)

Read the question? NEVER!

Recently, I gave the following questions to some of my first year students. Bear in mind that all of the content had been covered in the lectures and so should not have evoked some of the bizarre responses that I received...Below each question are the correct answers and the mark allocation.

Answer the following questions.


a) Some species of fish have evolved a modified muscle which permits them to generate electrical charge. What are these cells called? (1 mark)
Electrocytes (1)


b) Suggest two characteristics of these modified muscles which allow these tissues to generate electrical charge. (2 marks)
They possess little to no sarcoplasmic reticulum (SR) (1), they occur in a stacked arrangement like electrical cells in series (1), they respond to action potentials (AP’s) by altering their membrane potential (1).


c) What functions do these electrical charges serve for the fish? (3 marks)
Defence (1), Navigation (1), Communication (1), Hunting (1).


This is what the students wrote. Apparently reading the question is entirely optional:

a) Because the ventricular system is not fully developed, they have a ventricular septum that separates the right and left ventricles.

a) Electroreceptors [not entirely retarded, but certainly not the kind of question you should be messing up...but things then plummeted downhill; the next two answers were from the same person]

b) They have sphincters that contract and expand. They have axons that stimulate hormone production

c) They allow water to enter into the body, surrounding all cells and achieving homeostatis

b) More fibres. Higher contraction.

c) They help them to survive in water and be able to live under extreme conditions.

c) O2 transport. Nutrient and waste transport. Hormonal transport.

c) Defence; clear murky water by electrolysis and thermoregulation. [Emphasis added]