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SS1: BIOLOGY - 1ST TERM

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  1. Introduction to Biology | Week 1
    6 Topics
    |
    1 Quiz
  2. Recognizing Living Things | Week 2
    3 Topics
    |
    1 Quiz
  3. Organisation of Life | Week 3
    3 Topics
  4. Classification of Living Organisms | Week 4
    7 Topics
    |
    1 Quiz
  5. Kingdom Prokaryotae / Monera & Kingdom Protista | Week 5
    3 Topics
    |
    3 Quizzes
  6. Kingdom Fungi & Kingdom Plantae | Week 6
    9 Topics
    |
    2 Quizzes
  7. Kingdom Animalia I | Week 7
    6 Topics
    |
    1 Quiz
  8. Kingdom Animalia II | Week 8
    5 Topics
    |
    1 Quiz
  9. The Cell | Week 9
    3 Topics
    |
    1 Quiz
  10. The Cell Structure and Functions | Week 10
    4 Topics
    |
    1 Quiz
  11. The Cell and its Environment | Week 11
    4 Topics
    |
    1 Quiz
  12. Nutrition in Plants | Week 12
    4 Topics
    |
    1 Quiz



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Phylum Mollusca consists of a large group of animals with sizes ranging from microscopic organisms to organisms 20 metres long. They are a source of jewellery as well as food for human beings.

Snail
Snail (Phylum Mollusca)

Characteristics of Phylum Mollusca:

Phylum Mollusca have the following Characteristics;

1. They are soft-bodied animals.

2. Many are aquatic and mostly found in marine and freshwater. Few are terrestrial and found in moist soil.

3. The body is usually protected by a calcareous shell (a covering mostly made up of calcium carbonate). 

4. They have non-segmented bodies.

5. They possess serrated tongues (radula) for tearing food. Example: snails 

6. They have reduced coelom. (Coelomates)

7. There is a special fold of the body wall, called a mantle, which secretes the shell.

8. They are bilaterally symmetrical.

9. There is a ventral muscular foot which is usually used for crawling or swimming.

10. Digestive track is complete.

11. Circulatory system is complete. It has a three-chambered heart.

12. Respiration is by gills, others through the lungs on the mantle cavity.

13. They have sensory organs, tentacles and eyes.

14. Sexual reproduction is shown. The sexes are separated.

15. The snails and slugs include hermaphroditic as well as dioecious species.

16. Many are aquatic and some are terrestrial.

17. They are of economic importance:

  • They supply food and other materials.
  • They damage and destroy our crops.
  • They serve as an intermediate host for some flatworms.

18. Examples are:

  • Garden Snails (Helix aspersa)
  • Giant African Snails (Achantina fulina)
  • Clamps, Octopus, Oysters, Squids, Slugs, Scallops, and Mussels. 

Classification of Phylum Mollusca:

Phylum Mollusca can be classified as follows;

a. Polyplacophora e.g. Mussels
b. Gastropoda e.g. Snails and Slugs
c. Cephalopoda e.g. Octopus, Spirula

Diagram of a snail
Diagram of a snail.
Octopus
Octopus.
Mussels
Mussels.

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