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Ecology and medical parasitology

LEVELS OF BIOLOGICAL ORGANIZATION
Levels
Sciences
The biosphere
Macroecology, biogeography
Ecosystems
Ecosystem and landscape ecology
Communities
Community ecology
Populations
Population ecology
Organisms
Anatomy, physiology
Organs and organ systems
Anatomy, physiology
Tissues
Histology, physiology
Cells
Cytology, physiology
Organelles
Cytology, physiology
Molecules
Biochemistry, molecular biology

3.

4.

LEVELS OF BIOLOGICAL ORGANIZATION
• or the hierarchy of life, is the hierarchy of complex biological structures and
systems that define life.
The Biosphere
Ecosystem
Community
Species
Populations
Organism
Organs and organ systems
Tissues
Cells
Organelles
Molecules

5.

SPECIES
• … a population or group of populations whose members have
the potential to interbreed in nature and produce viable, fertile
offspring, but do not produce viable, fertile offspring with
members of other such groups.
• (biological species concept)

6.

7.

CLASSIFYING OF LIFE

8.

MEDICAL PERSPECTIVE
• The role of the human environment in preservation and
improvement of human health is studied by hygiene.
• The role of interspecies relationships in preservation and
improvement of human health is studied by medical
parasitology.

9.

ABIOTIC ENVIRONMENT
… is physical and chemical characteristics of organisms’
surroundings.
• Climate and microclimate (temperature, humidity, seasonality,
etc.)
• Chemical composition of air, water and soil, acidity, etc.
• Physical characteristics: noise, magnetic fields, radioactivity,
intensity of solar insolation, etc.

10.

BIOLOGICAL INTERACTIONS
• Interspecies relationships (or interactions between
species) are the effects organisms in a community have
on one another.
• Ecological community is a set of interacting species
within a particular habitat.

11.

CLASSIFICATION OF INTERSPECIES
RELATIONSHIPS
Interactions between species can be classified basing on their effects
which may be neutral (0), negative (-) or positive (+).
#
1
2
3
4
5
6
Interaction type
Mutualism
Commensalism
Antagonism
Competition
Amensalism
Neutralism
Effects
Species A
+
+
+
0
Species B
+
0
0
0

12.

STRENGTH AND DURATION OF SPECIES
INTERACTIONS
• The above-mentioned relationships can vary considerably in strength and
duration.
• Close and long-term interaction between two or more different
biological species is called symbiosis.

13.

MUTUALISM
• … is when two species live in association with each other
to the benefit of both.
• Example: mycorrhizal associations between
plant roots and fungi, flowering plant and pollinators,
human and domesticated animals.

14.

COMMENSALISM
• … is a class of relationship between two organisms where
one organism benefits but the other is neutral (there is no
harm or benefit).
• Quite difficult to demonstrate, can be just a case of
mutualism.
• Examples: birds eating insects scared off by cattle.

15.

COMPETITION
• two species use the same limited resource or harm
each other while seeking a resource.
• Examples: interspecies competition among plants for
sun light, intraspecies competition for mating, etc.

16.

AMENSALISM
• … is a relationship between two species in which the
individuals of one species negatively affect those of the
other and are unaffected themselves.
Example: sheep or cattle trample of grass.
Amensalism is often used to describe strongly asymmetrical competitive interactions.

17.

NEUTRALISM
• … describes the relationship between two species that
interact but do not affect each other.
• Examples: rabbits and soil frogs lliving together in a
grassland.
• The term is often used to describe situations where
interactions are negligible or insignificant.

18.

ANTAGONISM: TYPES
In antagonistic interactions one species benefits at the expense of another.
Several types of antagonistic relationships can be distinguished (mostly
basing of the type of interaction organisms):
• Predation: one animal species eats all or part of another animal species
(predator actively search for a prey, kills it for consumption and attacks
several preys in a lifetime).
• Herbivory: one animal species (herbivore) eats all or part of a plant species.
• Parasitism: one species, the parasite, benefits at the expense of the other,
the host, (similar to predation, but parasite normally does not kill its host and
attack one or two organisms). Parasite eats the cell contents, tissues, or
body fluids of its host. A host is an organism that harbours a parasite.

19.

HUMAN PARASITES
• “Humans are hosts to nearly 300 species of parasitic worms and over 70
species of protozoa, some derived from our primate ancestors and some
acquired from the animals we have domesticated or come in contact with
during our relatively short history on Earth .” Cox F.E.G. 2002. "History
of human parasitology". Clinical Microbiology Reviews 15 (4):
595–612.
• Medical Parasitology is the branch of medical sciences dealing with
organisms (parasites) which live temporarily or permanently, on or within the
human body (host).

20.

HUMAN PARASITES
• …belong to the following kingdoms of organisms:
• Kingdom Protists – mostly protozoa which single-celled
heterotrophic eukaryotes
(the area of medical protozoology).
• Kingdom Animalia – multicellular heterotrophic organisms
(Metazoa), mostly helminthes and insects (medical
helminthology and entomology).
• NOTE: bacteria and viruses also have characteristics of
parasitic behavior but they are not an object for medical
parasitology.

21.

MEDICAL PARASITOLOGY
• … is the subject which deals with the parasites that infect
humans, the diseases caused by them, clinical picture and the
response generated by humans against them. It is also
concerned with the various methods of their diagnosis,
treatment, prevention and control.

22.

KINGDOM OF PROTISTS
• Protozoa
• Phylum Sarcodina (Amoebae)
• Phylum Mastigophora (Flagellates)
• Phylum Apicomplexa (Sporozoa)
• Phylum Ciliophora (Ciliates)

23.

KINGDOM OF PROTISTS
Protozoa
• Phylum Sarcodina (Amoebae)

24.

KINGDOM OF PROTISTS
Protozoa
• Phylum Mastigophora (Flagellates)

25.

KINGDOM OF PROTISTS
Protozoa
• Phylum Apicomplexa (Sporozoa)

26.

KINGDOM OF PROTISTS
Protozoa
• Phylum Ciliophora (Ciliates)

27.

KINGDOM ANIMALIA
Metazoa
• Phylum Plathelminthes (Flatworms)
• Class Trematoda (Flukes)
• Class Cestoda (Tapeworms)
• Phylum Nemathelminthes (Round worms)
• Nematoda (Nematodes)
• Phylum Arthropoda (Arthropods)
• Crustacea
• Arachnida
• Insecta

28.

MAIN TYPES OF PARASITES
• Ectoparasite – a parasitic organism that lives on the outer
surface of its host, e.g. lice, ticks, mites etc.
• Endoparasites – parasites that live inside the body of their
host, e.g. Entamoeba istolytica.

29.

TYPES OF PARASITISM
• Obligate parasite – this parasite is completely dependent on the host
during a segment or all of its life cycle, e.g. Plasmodium spp.
• Facultative parasite – an organism that exhibits both parasitic and nonparasitic modes of living and hence does not absolutely depend on the
parasitic way of life, but is capable of adapting to it if placed on a host,
e.g. Naegleria fowleri.
• Accidental parasite – when a parasite attacks an unnatural host and
survives, e.g. Hymenolepis diminuta (rat tapeworm).
• Erratic parasite – is one that wanders in to an organ in which it is not
usually found, e.g. Entamoeba histolytica in the liver or lung of humans.

30.

HOST TYPES
• Final (Definitive) host – a host that harbours a parasite in the
adult stage or where the parasite undergoes a sexual reproduction.
• Intermediate host – harbours the larval stages of the parasite or
an asexual cycle of development takes place. In some cases,
larval development is completed in two different intermediate
hosts, referred to as first and second intermediate hosts.
• Transitory/accidental/paratenic hosts lodging parasitic stages
without further reproduction.

31.

HOST TYPES
• Reservoir host – a host that makes the parasite available for the
transmission to another host and is usually not affected by the
infection.
• Natural host – a host that is naturally infected with certain species
of parasite.
• Accidental host – a host that is under normal circumstances not
infected with the parasite.

32.

EFFECTS OF A PARASITE ON ITS HOST
The damage which pathogenic parasites produce in the tissues of the host
may be described in the following two ways:
Direct effects of the parasite on the host
• Mechanical injury - may be inflicted by a parasite by means of pressure
as it grows larger producing infraction.
• Harmful effect of toxic substances.
• Deprivation of nutrients, fluids and metabolites -parasite may produce
disease by competing with the host for nutrients.

33.

EFFECTS OF A PARASITE ON ITS HOST
Indirect effects of the parasite on the host
• Immunological reaction: Tissue damage may be caused by immunological response
of the host, e.g. nephritic syndrome following Plasmodium infections.

34.

ADAPTATIONS TO PARASITISM
• Morphological adaptations
• Reduction of some organ systems (CNS, sense organs, guts, locomotory
organs etc.)
• Elaboration of the reproductive organs, associated with increased
gamete production.
• Development of attachment organs

35.

ADAPTATIONS TO PARASITISM
• 2. Life Cycle Adaptations
Infection of secondary and tertiary hosts. This has three advantages:
• It increases the range of the parasite in space and time. That is infection
of more than one host can increase the geographical range of a parasite,
particularly if one host is say terrestrial and the other aquatic. By
infecting more than one host species the parasite can survive periods
when one host is temporarily scarce.
• An intermediate host can channel the parasite towards its definitive host
since the intermediate host is frequently part of the final host's food
chain or else closely related ecologically.

36.

ADAPTATIONS TO PARASITISM
• 2. Life Cycle Adaptations
reduce the extent of the free-living phase of the life cycle (this
avoids the variable external environment).

37.

ADAPTATIONS TO PARASITISM
• 3. Immunological Adaptations
• Absorption of host antigen
• Antigenic variation
• Occupation of immunologically privileged sites
• Disruption of the host's immune response
• Molecular mimicry
• Loss or masking of surface antigens

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