1.
BY
MUHAMMAD USMAN ZAKI

2.
Evolution and Economic Importance
of Bacillariophyta

3.
Bacillariophyta (Diatoms)
“ Bacillariophyta are unicellular organisms that are
important components of phytoplanktons as primary
sources of food zooplanktons in both marine and fresh
water habitats.”

4.
*Except for their gametes diatoms lack flagella
*A unique feature of diatom anatomy they are surrounded by by a Cell Wall made of
Silica (hydrated Silicon dioxide) called frustule
*A sexual and sexual reproduction occur in them
*May be single celled or in colonies, photosynthetic
*Base of the food chain .
*Planktonic and Benthic foome
*Can move on and within the sediment with mucus streamers associated with a groove
called the raphe

5.
*Can live heterotrophically in the clark
*Diversity of the Benthic forms is highly worldwide
*Diatoms are “ golden brown algea”
*Some classify them in the phyllum Bacillariophyta
*Other workers, put them, with the coccolithophores, in the phyllum,choysophyta
* Frustule shape vary greatly, so there is no simple summary of morphology

6.
Two major sub- divisions are recognized .
Centrales:.
Centric =Circular Oblong, hemicircular, triangular or quadrangular, with
surface features arranged around a central point.
Pennates:.
Pennate = Elongate with major features at sight angels to the median line.

7.
EVOLUTION
The diatoms are one algal groups. Despite this little is known of the evolution of the group from
ecoliest cell to the myrlad of taxa known today.
Relationship among taxa at the family or generic level have been recognized in some diatoms . How
ever relationships at higher taxonomic levels are poorly understood and have been strongly
influenced by the appearance of key taxa in the fossil record. An independent assessment of
relationship among the diatoms at these .Higher taxonomic levels has been made by using RNA
sequence data to infer phylogenetic relationships Ribosomal RNA data indicate that both the Centric
and pennate lineages may not be monophyletic.

8.
Economic importance of Bacillariophyta(Diatoms)
*Producer
 Diatoms are primary procedure. They are phytoplanktons most of the
photosynthesis is carried out by diatoms in marine environment.
 Diatoms are estimated to be responsible for 20% to 25% of all the organic
carbon fixation.
*As Food
 food Diatoms are food source for many types of animals in marine and
freshwater environment. Many fishes depend on diatoms for their food.
 Base of the food chain because they are called “ Grass of the sea”.

9.
*Petroleum Products
 The body of diatoms contains about 11% oil. Their oil contents are
 fossilized into petroleum products.
*Diatomaceous earth
Dead diatoms deposits on the surface of ponds, lakes and sea. These deposits
are called diatomaceous earth. It has following uses;
 It is used to polish metal and automobile
 it is used in tooth and tooth paste

10.
 It is used as fire proof material
 It is used as absorbent in dynamites
 it is used to filter oils and syrup in sugar industries
 it is used to prepare light weight bricks . These bricks are used for building
fire proof houses.