Gastropod Torsion and Anatomy Quiz

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Questions and Answers

What is the orientation of organs like ctenidia and osphradia after torsion in gastropods?

They face backwards
They face forwards (correct)
They are completely reabsorbed
They remain in their original position

What is a characteristic feature of the pleuro-visceral connectives after torsion?

They are eliminated entirely
They elongate without twisting
They remain untwisted
They form a twisted loop (correct)

Which of the following statements about bilateral symmetry in gastropods is true?

It is enhanced after torsion
It is regained in adult stages
It is maintained throughout development
It is lost after torsion (correct)

Which of the following organs do most gastropods lose from their original left side after torsion?

Osphradium and hypobranchial gland (C) Signup and view all the answers

What advantage does torsion provide to larval gastropods?

Immediate selective advantage during shell withdrawal (B) Signup and view all the answers

In molluscs, which nervous system condition is characterized by a simpler, undifferentiated structure?

Protoneurous condition (C) Signup and view all the answers

What characterizes the streptoneurous condition in gastropods?

Twisting of the entire pallial complex (C) Signup and view all the answers

What structural change occurs to the foot of gastropods as a result of torsion?

It retracts faster for protection (D) Signup and view all the answers

Flashcards

Torsion in Gastropods

The process where a gastropod's body twists 180 degrees, resulting in a change in organ orientation and nerve pathways.

Chiastoneury

The twisting of the pleuro-visceral connectives during torsion, forming a loop. This affects the arrangement of the nervous system.

Loss of Bilateral Symmetry

The original bilateral symmetry of a gastropod is lost due to torsion, resulting in an asymmetrical body plan.

Protection in Torsion

Torsion allows for the faster retraction of the head and velum, providing protection from predators.

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Mantle Cavity Positioning

The mantle cavity, which houses the gills, is moved from a posterior to an anterior position during torsion. This placement allows for better water flow and oxygen uptake.

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Protoneurous Condition

A simple, undifferentiated nervous system found in chitons. It lacks distinct ganglia.

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Streptoneurous Condition

A more complex nervous system seen in many gastropods. Torsion causes the parietal ganglion to shift position, leading to alterations in nerve connections.

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