This document provides information about protozoa, helminths, and parthenogenesis. It discusses the characteristics, morphology, nutrition, reproduction, diseases caused by, and treatments for protozoa. It also covers the classification, characteristics, diseases caused by, and treatments for helminths. Finally, it defines and describes different types of parthenogenesis such as natural vs artificial and apomictic vs automictic parthenogenesis. It notes some organisms that commonly exhibit parthenogenesis and the significance of this reproductive strategy.
2. Index
1. Protozoa
Characteris
tics and
Morpholog
y of
protozoa
Other
Morpholog
ical
Character
Nutrition
Classificati
on of
Protozoa
Reproducti
on of
Protozoa
Diseases
Caused by
Protozoa
Antiprotoz
oal Drug
2. Helminths
Some
other
classes
Taxonmical
Classificati
on of
Helminthes
Characteris
tics of
Helminthes
Diseases
caused by
Helminthes
Antihelmint
ics Drugs
Classificati
on of
Anthelminti
cs Drugs
1.Parthenogenesis
Other features
Classification of parthenogenesis
Natural parthenogenesis
Natural occurrence
Artificial Parthenogenesis
Apomictic and Automictic parthenogenesis
Some other types
Only single way of reproduction
Significance of parthenogenesis
3. Protozoa
Protozoan, organism, usually single-celled and
heterotrophic (using organic carbon as a source of energy),
belonging to any of the major lineages of protists and, like
most protists, typically microscopic. All protozoans
are eukaryotes and therefore possess a “true,” or
membrane-bound, nucleus. They also are nonfilamentous
(in contrast to organisms such as molds, a group of fungi,
which have filaments called hyphae) and are confined to
moist or aquatic habitats, being ubiquitous in
such environments worldwide, from the South Pole to
the North Pole. Many are symbionts of other organisms,
and some species are parasites.
4. Characteristics and Morphology of Protozoa
Characteristics
Mostly unicellular organism with fully
functional cell.
Protozoa is mainly chemo-hetrotophs.
Live freely, may be symbiotic or parasitic.
They are motile having locomotive organelles
e.g., flagella and cillia, etc.
Morphology
Protozoa are Eukaryotic resemble to animal cell,
contain major cell organelle (including Nucleus
and Mitochondria).
There organelle are highly organized for feeding,
reproduction and movement.
The cytoplasm of protozoa are divided into an
outer layer ectoplasm and inner layer endoplasm
respectively.
Freshwater protozoa have Contractile vacuoles
To pump out excess water.
5. Other Morphological Character
• The size of protozoa is range between 3 to 300 micrometer.
• Few cilliate and Amoeba are large enough to be seen with
naked eyes (4-5 mm in size).
• Ectoplasm help in movement, feeding and protection.
• Endoplasm houses Nucleus, Mitochondira and Food.
• Their shape remain constant (specially in Cilliate) and change
constantly (Amoeba).
• Except Sporozoates, all type of protozoa are motile either
flagella, cillia and pseudopodia.
• Some have eyespot that can detect change in light.
6. Nutrition
Mostly protozoa feed on dead plants and
animal debris while some trophozoites
feed on Bacteria and Algae.
Parasitic protozoa feed on the fluid and
tissue of their hosties e.g., Plasma and
Blood cells.
Some protozoa live in Symbiotic
relationship with other plant and animals.
7. Classification of Protozoa
Protozoa are classified information the basis of
motility and it’s method of reproduction. There are
four main types –
1. Flagellate
2. Cilliate
3. Sarcodina
4. Sporozoate
8. Reproduction in Protozoa
Protozoa reproduce by both asexual and sexual means, though sexual reproduction is less common and
occurs in certain groups. Most protozoa reproduce asexually by cell division producing two equal or
sometimes unequal cells.
Asexual methods of reproduction are:
1. Budding
2. Binary Fission
3. Multiple Fission or Schizogony
Sexual methods of reproduction are:
1. Conjugation
2. Gametogony
11. Antiprotozoal Drug
Antiprotozoal drug: Something that destroys protozoa or inhibits their growth and
ability to reproduce.
A few of the protozoa of medical importance include Plasmodium (the cause
of malaria); Entamoeba histolytica (the cause of amebiasis, amebic dysentery) and
Trichomonas vaginalis (a cause of vaginal infection); and Pneumocystis carinii (a
common cause of pneumonia [PCP] in immunodeficient persons).
Some antiprotozoal drugs include the antimalarials Aralen (chloroquine),
Daraprim(Pyrimethamine), Lariam (Mefloquine), and Plaquenil
(hydroxychloroquine), Flagyl (Metronidazole) which is active against. Entamoeba
histolytica and Trichomonas vaginalis; and Mepron (atovaquone) for Pneumocystis
carinii.
13. Helminths
Helminths are worm-like parasites that survive by feeding
on a living host to gain nourishment and protection,
sometimes resulting in illness of the host. There are a
variety of different helminths from the very large to the
microscopic.
Their motile movement is accomplished by wriggling
movement. The helminths of medical importance belong to
three classes:
1. Nematoda
2. Termatoda
3. Cestoda
Study of parasitic worm and their effect on host is termed
as Helminthology.
14. Some Other Classes
Geohelminths: The helminths which complete their life cycle not requiring
the process of the development of intermediate host.
They have only one host and simple life cycle such as ascarid, hookworm,
pinworm, etc.
Biohelminths: It refers to those, who undergoes into the development in
intermediate host to complete their life cycle, such as filaria, liver fluke, pork
tapeworm, etc.
17. Mode of entry
Parasitic mode of entry
1. Ingestion
2. Arthropod Bites
3. Direct pentration of intact skin or mucous membrane
Spread and Tropisms
Some parasite must migrate to certain location within the host in order to complete their
life cycle.
Non-human parasite, in humans, often fails to migrate properly and become “dead-
end-infection”.
19. Anthelmintics Drugs
Anthelmintics are drugs that are used to treat infections with parasitic worms. This
includes both flat worms, e.g., flukes and tapeworms and round worms, i.e., nematodes.
They are of huge importance for human tropical medicine and for veterinary medicine.
The World Health Organization estimates that a staggering 2 billion people harbour
parasitic worm infections.
Parasitic worms also infect livestock and crops, affecting food production with a resultant
economic impact. Also of importance is the infection of domestic pets.
20. Anthelmintics Drugs
Classification of Anthelmintics Drugs: Anthelmintics
are separated into classes on the basis of similar
chemical structure and mode of action.
1. Piperazine
2. Benzimidazoles
3. Levamisole, pyrantel and morantel
4. Paraherquamide
5. Ivermectin (macrocylic lactones and milbemycins)
6. Emodepside (cyclodepsipeptides, PF1022A)
7. Nitazoxanide
22. Parthenogenesis
Parthenogenesis is a form of
reproduction in which an egg
can develop into an embryo
without being fertilized by a
sperm. Parthenogenesis is
derived from the Greek words
for “virgin birth,” and several
insect species including
aphids, bees, and ants are
known to reproduce
by parthenogenesis.
23. Other features
Parthenogenetic reproduction requires a
mechanism to circumvent the normal halving
of ploidy that results from gametogenesis. In
insects, many mechanisms for the preservation
or restoration of diploidy have evolved. Either
meiosis is eliminated (apomixis) or diploidy is
restored (automixis) during or after meiosis.
The study of parthenogenesis can illuminate
one of the central problems in biology, that of
explaining the ubiquity of sex and
recombination, and the adaptive significance
of the laws of genetics, by revealing when and
where in nature the laws of genetics are
suspended or overthrown.
24. Classification of
Parthenogenesis
On the basis of occurrence: There are
two types of parthenogenesis on the
basis of occurrence:
1. Natural Parthenogenesis
2. Artificial Parthenogenesis
On the basis of method of division:
There are two types of parthenogenesis
on the basis of method of division:
1. Apomictic Parthenogenesis
2. Automictic Parthenogenesis
25. Natural Parthenogenesis
In some animals, parthenogenesis occurs naturally in their life cycles. This is known as natural
parthenogenesis.
Natural parthenogenesis can be further divided into:
1. Complete Parthenogenesis: A few insects have no males and no sexual phase. Such organisms
depend upon self-reproduction. This is known as complete parthenogenesis.
2. Incomplete Parthenogenesis: The life cycle of a few insects involves two generations:
Sexual generation
Parthenogenesis generation
In this, the unfertilised eggs produce males and the diploid eggs produce females. This type of
parthenogenesis is called partial or incomplete parthenogenesis.
26. Natural occurrence
Parthenogenesis is seen to occur naturally
in aphids, Daphnia, rotifers, nematodes and some
other invertebrates, as well as in many plants.
Among vertebrates, strict parthenogenesis is only
known to occur in lizards, snakes,birds and
sharks, with fish, amphibians and reptiles
exhibiting various forms of gynogenesis and
hybridogenesis (an incomplete form of
parthenogenesis.
Some sexual species may occasionally
reproduce parthenogenetically; the Komodo
dragon and hammerhead and blacktip
sharks are recent additions to the known list
of spontaneous parthenogenetic vertebrates.
27. Artificial
Parthenogenesis
Physical Means
1. Temperature induces parthenogenesis in eggs. For eg.,
parthenogenesis is induced if an egg is transferred from -30 to
-10°C.
2. Parthenogenesis is caused by ultraviolet light.
3. Electrical shocks cause parthenogenesis.
4. When an egg is pricked by a needle, the development occurs
parthenogenetically.
Chemical Means: The chemicals that are responsible for the
parthenogenesis of eggs are:
1. Chloroform
2. Urea and Sucrose
3. Strychnine
4. Fat solvents
5. Acids
6. Chlorides
The fertilised eggs might
sometimes develop
parthenogenetically by
various chemical and
physical means. This is
known as artificial
parthenogenesis.
28. Apomictic and Automictic Parthenogenesis
Apomictic Parthenogenesis
Parthenogenesis can occur without meiosis through
mitotic oogenesis. This is called apomictic
parthenogenesis. Mature egg cells are produced by
mitotic divisions, and these cells directly develop
into embryos. In flowering plants, cells of
the gametophyte can undergo this process. The
offspring produced by apomictic parthenogenesis
are full clones of their mother. Examples include
aphids.
Automictic Parthenogenesis
automictic parthenogenesis) is a
postmeiotic process in which a haploid
cell may either duplicate its
chromosomes or join with another
haploid cell. In both cases, diploid
zygotes develop and grow into diploid
adults. Such organisms are not true
clones of the mother
29. Some Other Types
1. Facultative parthenogenesis: It is the term for when a female can produce offspring either sexually or
via asexual reproduction. Facultative parthenogenesis is extremely rare in nature. Facultative
parthenogenesis is often used to describe cases of spontaneous parthenogenesis in normally sexual
animals. many cases of spontaneous parthenogenesis in sharks, some snakes, Komodo dragons and a
variety of domesticated birds were widely attributed to facultative parthenogenesis.
2. Obligate parthenogenesis: It is the process in which organisms exclusively reproduce through asexual
means. Many species have been shown to transition to obligate parthenogenesis over evolutionary time.
Well documented transitions to obligate parthenogenesis have been found in numerous metazoan taxa,
albeit through highly diverse mechanisms. These transitions often occur as a result of inbreeding or
mutation within large populations.
30. Parthenogenesis has become almost a single way of reproduction
In some species parthenogenesis have played
a main role in maintaining their biological
race generation to generation, which are:
1. Oomycetes
2. Velvet worm
3. Rotifer
4. Flatworms
5. Snail
31. Significance of Parthenogenesis
Parthenogenesis is important for the few crucial reasons,
which are:
1. Parthenogenesis helps in determining the sex of an
individual in honey bees, wasps, etc.
2. It supports the chromosomal theory of inheritance.
3. Variations from populations are eliminated by
parthenogenesis.
4. It is the simplest, most stable and easy process of
reproduction.
5. Polyploidy in organisms is caused by parthenogenesis.
6. It helps in the development of advantageous mutant
characters.
7. Non-adaptive combination of genes is controlled.
8. There are no sterile races.
However, the organisms produced by parthenogenesis
cannot survive for long due to no recombination of
genetic material.
