CLASS GASTROPODA

Question 1

What are the characteristics of class Gastropoda?

Answer 1

Uni-valved, a-symmetrical, cephalisation

Question 2

Describe the a-symmetrical shell

Answer 2

Coiled and torted

Question 3

What are the tentacles?

Answer 3

They are chemoreceptive

Question 4

What are statocysts?

Answer 4

A small organ for balance and orientation

Question 5

What is an osphradium?

Answer 5

An organ that tests the incoming water

Question 6

What is the planispiral?

Answer 6

An unstable, asymmetrical shell

Question 7

Describe the consequences and solutions of an asymmetric shell

Answer 7

The lengthened shell and cone shape resulted in a stability problem, coiling and torsion solved this

Question 8

What is torsion?

Answer 8

The visceral mass turning 180 degrees

Question 9

Describe the gut shape

Answer 9

‘U’ shape

Question 10

What is the problem with the gonoduct openings, kidney and anus being above the head?

Answer 10

A sanitary problem

Question 11

What is the solution to the gonoduct openings, kidney and anus being above the head and restricted waterflow?

Answer 11

Tthere’s an opening for an exhalent current. Water goes into the mantle cavity & out the opening. e.g. keyhole limpets

Question 12

Describe the shell

Answer 12

Whorls wrapped around central columella, oldest are smallest

Question 13

What secretes the new shell?

Answer 13

The mantle margin around aperture

Question 14

What is the function of the operculum?

Answer 14

Closes the aperture

Question 15

What is the orientation of some shells?

Answer 15

Most are dextral (right coiled), few are sinistral (left coiled)

Question 16

What organism is the excretion, respiration and circulation like?

Answer 16

The generalised mollusc

Question 17

What are the exceptions to the similarities between the generalized mollusk and gastropoda?

Answer 17

The right metanephridium, gill and atrium are lost

Question 18

Explain the changes of the pulmonates as a result of moving onto land

Answer 18

Both gills are lost, the mantle cavity is heavily vascularized and there’s a lung

Question 19

Name the structure in a grazer

Answer 19

Radula

Question 20

Name the structure in a hunting carnivore

Answer 20

Proboscis and a simplified gut

Question 21

Name the structure in deposit, filter and suspension feeders

Answer 21

Modified gills, mucus nets and parasites

Question 22

What is the flexible structure or water intake and how is it made?

Answer 22

The siphon, made by the anterior left mantle margin being rolled

Question 23

In what kind of gastropods is the siphon well developed?

Answer 23

Predatory or scavenger snails

Question 24

What other organism is the nervous system in gastropoda like and exceptions?

Answer 24

The generalized mollusk. Exceptions are torsion and cephalisation.

Question 25

Explain the process of torsion

Answer 25

The visceral mass is twisted which brings the mantle cavity and anus to an anterior position above the head

Question 26

Describe the reproduction process in early gastropods

Answer 26

Dioecious and external fertilization

Question 27

What are some other reproduction traits of gastropoda?

Answer 27

Hermaphrodites, internal fertilization and behavior patterns are more complicated

Question 28

What is simultaneous hermaphroditism?

Answer 28

Male and female at the same time

Question 29

What is protandric hermaphroditism?

Answer 29

The individual changes sex at some point in its life, male to female

Question 30

Name the groups of organisms that are simultaneous hermaphrodites

Answer 30

Pulmonata and Opisthobranchia

Question 31

Name the groups of organisms that are protandric hermaphrodites

Answer 31

Prosobranchia (slipper snails

Question 32

Name the groups of organisms that are protandric hermaphrodites

Answer 32

Prosobranchia (slipper snails

Question 33

What kind of larva does archaeogastropoda have?

Answer 33

Planktonic trocophore larva

Question 34

What kind of larva do most other gastropods have?

Answer 34

Derived veliger larva

Question 35

How do veliger larva swim?

Answer 35

Using a ciliated velum

Question 36

What does the veliger larva have before it settles?

Answer 36

A shell and torsion

Question 37

What kind of development does the class Pulmonata have?

Answer 37

Direct