Page 134 - Biology_F5

Comparative studies of natural groups of organisms

Many are also found in the form of (g) Some protoctists are used in agriculture
plankton and some live in the bodies of as good sources or fertilizer. For
animals as parasites. Some members of example, liquid extracts from the
the kingdom Protoctista play an essential brown algae supply potassium and
role in the ecosystem that can benefit trace elements such as zinc.
humans and other creatures. However, (h) Some algae serve as a source of agar,
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some members are important pathogens used in the pharmaceutical industry
and can harm living organisms. In some in preparation of culture media for
cases, Protoctista might be a source of growing microbes, such as bacteria
pollution in lakes and coastal shores. and fungi.
(i) Some protoctists such as algae are
Advantages of kingdom Protoctista milled or ground to obtain powder
Protoctists have the following economic which is used as a thickener, binder,
importance: gelling or stabilising agents in the
(a) Algae are edible and nutritious to humans manufacture of various products such
and other animals. Some species are as cosmetics, paints, tooth paste, and
cultivated and harvested for consumption ice cream.
by human being. Red algae are rich in
vitamins and minerals. Carrageenan, a (j) Some protoctists such as Entamoeba
polysaccharide extracted from red algae, coli; a non-pathogenic species of genus
is used as thickening agent in ice cream Entamoeba, can exist as a commensal
and other foods. parasite in the human gastrointestinal

(b) Giant kelp forests (Large brown algae) tract and feed on pathogenic bacteria.
are rich ecosystems, providing food
and shelter for many organisms. Disadvantages of kingdom Protoctista

(c) Trichonymphs are flagellates that live (a) They cause pollution; the red algae
cause water pollution called the algal
in the intestines of termites. These bloom, which may hinder boating and
protozoans break down cellulose in recreation.
wood into carbohydrates that termites
can digest. (b) They cause diseases to human beings;
for instance, Amoebiasis is caused
(d) Algae and Euglena are primary by Entamoeba histolytica, malaria is
producers in aquatic ecosystems. Most caused by Plasmodium species (like
species are primary sources of food for Plasmodium malariae, Plasmodium
aquatic organisms such as fishes and vivax, and Plasmodium falciparum).
zooplanktons. (c) Some members of the kingdom
(e) Some Protoctists are used as fish baits. cause diseases to animals; for
(f) Algae species produce oxygen which example Trypanosoma brucei causes
is useful for aerobic respiration, Trypanosomiasis (sleeping sickness)
particularly in the aquatic environment, to humans, Trypanosoma vivax causes
which is utilised by other aquatic Nagana disease in cattle.
organisms.

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