Скачать или смотреть Identify Common Disease-Causing Organism 12th bio practical no -14 cbse, gseb

Procedure
Observe the preserved specimens/slides/photographs and note down the
features in the practical record book. Take care to observe all the minute
details and draw labelled diagrams of the pathogens.
Observation
A. Entamoeba
Observe the following features of the parasite in the slide or photograph:
(i) It is unicellular.
(ii) Shape of the cell is irregular due to
pseudopodia.
(iii) A single nucleus is present eccentrically in
the cell.
(iv) *In the nucleus a peripheral ring of granule
of nucleoprotein and central karyosome are
observed. Rest of the space in the nucleus
looks empty (Fig. 14.1).
(v) A few food vacuoles may be seen in the
cytoplasm. Contractile vacuoles are absent.
(vi) *Mature quadrinucleated cysts may be
present.
Fig.14.1 An Entamoeba
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Note: Entamoeba is an intestinal parasite in humans and causes amoebic
dysentery. The symptoms of the disease are frequent loose, mucus filled
watery stools, abdominal pain and spasms.
Systematic position
Phylum – Protozoa
Class – Rhizopoda
Type – Entamoeba histolytica
Distinctive feature of the pathogen
B. Plasmodium vivax
C. Ascaris
The external features of round worm are as follows:
(i) Body long (20 to 40 cm), cylindrical (5 to 6 mm
diameter) with no segmentation (Fig. 14.3).
(ii) Sexes are separate; the females are longer than
the males.
(iii) Both the ends are pointed; posterior end of male
is ventrally curved.
(iv) Mouth is situated at the anterior end, and is
surrounded by three lips, one present middorsally
and rest two lips are situated
ventrolaterally (for viewing these lips a magnifying
lens is needed).
(v) Single longitudinal lines are present on the dorsal,
ventral and on the two lateral sides, all along the
length of the body. Out of these the lateral lines
are comparatively more distinct than the others
lines.
(vi) Excretory pore is present on the ventral surface
slightly behind the anterior end.
(vii) In addition to the ventrally curved posterior tip,
the male worm has a pair of penial spicules very
close to the cloacal opening.
(viii) In case of female specimen a female genital
aperture is present mid-ventrally about one third
distance from the anterior end.
Systematic position
Phylum – Aschelminthes
Class – Nematoda
Type – Ascaris lumbricoides
Note: Round worm or Ascaris is one of the common parasite found in the
intestine of human beings.
Symptoms: (a) Irregular bowel, (b) Occasional vomiting, (c) Anaemia
(i) It is an intracellular endoparasite seen easily within the RBC of the
infected person.
(ii) It is unicellular.
(iii) The most diagnostic stage of the parasite is "signet ring" stage in the
erythrocytes, within which it appears as a rounded
body (Fig. 14.2).
(iv) It has a big vacuole inside, and the cytoplasm is accumulated at one
place containing the nucleus. Because of the above mentioned features,
the parasite appears as a ring.
Search the stage in the blood film slide, find the signet-ring stage, and
draw its labeled diagram.
Note: It is a protozoan parasite causing malaria in humans. When an infected
female anopheles mosquito bites a healthy person, it injects the infective
stage, sporozoite, into the peripheral blood vessels. The infective stage
undergoes several rounds of multiplication in liver and erythrocytes.
Symptoms: Intermittent high fever with chills followed by profuse sweating
at an interval of alternate days.
Systematic position
Phylum – Protozoa
Class – Sporozoa
Type – Plasmodium vivax
Trichophyton (Ringworm fungus)
It is a fungus that feeds on keratin of the skin of human beings. The features
as observed under the microscope are:
1. Texture of hyphae is waxy, glabrous to cotton like.
2. Unstained hyphae are white, yellowish brown to reddish brown in colour.
Systematic position
Kingdom – Fungi
Class – Deuteromycetes
Type – Trichophyton rubrum
Symptoms
Ringworm is a contagious fungal infection of the skin. Infected area of skin
is itchy, red, raised, scaly patches (with sharply defined edges). It is more
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