The document provides an in-depth study of diatoms, covering their classification, occurrence, cell structure, reproduction, and economic importance. Diatoms, classified into centric and pennate types, inhabit various environments and possess unique cell structures made of siliceous walls. The document also highlights their significance in industries and their role as pollution indicators.

1. Presented By:
Inchara R
1st Semester
Molecular Biology
30/10/2017
Guided By:
Dr. N. S. Devaki
Course Coordinator
Dept. of molecular
Biology
DIATOMS

2. CONTENTS Introduction
 Occurrence
 Classification
 Differences and Examples Of Diatoms
 Cell Structure
 Reproduction
 Economic Importance
 Conclusion
 References
 Acknowledgement

4. OCCURENCE
There are about 16,000 species grouped under 200
genera.
They occur in various habitats like fresh water, saline
water and also in terrestrial condition.
They occur as epiphytes.
There are epizoic also.

5. CLASSIFICATION
Class: Bacilloriophyceae
Order: Centrales Order: Pennales

6. DIFFERENCES BETWEEN
CENTRIC DIATOMS PENNATE DIATOMS
1. Shape and size varies. 1. Boat shaped.
2. Radial symmetry. 2. Bilateral symmetry.
3. Discoid chloroplast. 3. Elongated chloroplast.
4. Raphe is absent. 4. Raphe is present.
5. Radiantly arranged
striations.
5. Pinnate striations.

7. Corethron Clyclotella
Centric diatoms
Fig 1: Fig 2:

8. Fig 9: Tubellaria fenestrata
PennateDiatoms
5. 6.
Fig 7. Fig 8: Cocconies
placentula

9. Structure of cell wall consists of two parts.
1.Cell Wall 2.Protoplast
1.Cell Wall
Cell wall is made up of pectic substances impregnated
with silica.
Cells are covered by siliceous wall, the frustule.
These consists of two overlapping halves, the theca.
CELL STRUCTURE

10. A.Valve view B.Girdle view
Fig10: Cell
structure of
Pinnularia
virids.
C.Transverse
section

11. STRAITIONS
Fig 11: Cyclotella
bodanica Fig 12: Navicula
acumtaina

12. 2. Protoplast
• The entire content present inside the cell wall is
protoplast.
• The cytoplasm contains single nucleus and other cell
organelles.
• Reserve food material is chrysolaminarin, volutin and oil
droplets.
• The photosynthetic pigment chlorophyll a, chlorophyll
chlorophyll C2, beta-carotene, fucoxanthin etc.
• Diatoms are colour due to the presence of carotenoids
and an accessory brown pigment called a diatomin.

13. Fig 13:
Chromatophores in
Pinnularia virids
(Pennales) (A-B)
and valve view of centric
diatoms (C)

14. REPRODUCTION
There two types of reproduction.
Vegetative reproduction
Sexual reproduction

15. Vegetative REPRODUCTION
Fig 14: Navicula halophila

16. SEXUAL REPRODUCTION
Auxospore formation in Pennales are of
different types:
Production of one auxospore by two conjugating cells.
Production of two auxospore by one conjugating cells.
Production of one auxospore by a single cell.
Production of auxospore by autogamy.
Production of auxospore by parthenogenesis.
Production of auxospore by oogamy.

17. Production of two auxospore by two conjugating
cells
Cymbella lanceolataFig 15:

18. ECONOMIC IMPORTANCE
Diatomite: Very much useful in Industries.
Fig 16. A Fig 17: B

19. Testing of microscopic lenses.
Fig 18: Pinnularia dactylus Fig 19: Pictinfra

20. Used as food.
Fig 20.

21.  Petroleum is considered to be diatom origin.
 It is used as Pollution Indicators.
 Diatom is used in tooth paste.

23. REFERENCES B. R. Vashishta, A. K. Sinha, V. P. Singh. 1960. Botany For Degree
Students Algae. S. Chand $ company Ltd., Ram Nagar, New Delhi,
544pp.
 F. E. Fritsch. 1965. Structure $ Reproduction of Algae. Cambridge
University Press, New York, 791pp.
 www.biologydisscussion.com/algae/diatoms-charecteristics-
occurrence-and-reproduction/46940.
 Cals.Arizona.edu

24. ACKNOWLEDGEMENT
I would like to thank the dept. of Molecular Biology for
providing this opportunity to present this seminar.
I would also like to thank my guide DR. N.S. Devaki ma’am for
her valuable guidance.
Thank you one and all.

25. THANK YOU