Kingdoms Monera, Protista, and Fungi

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Kingdoms Monera, Protista, and Fungi

• The First Three Kingdoms

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KINGDOM MONERA

• These are the oldest, simplest and most numerous
  microorganisms. They are distinguished by the
  following characters
• I. They are prokaryotes. Prokaryotes do not have
  a nucleus enclosed by a membrane.

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• II. They are mostly single celled, but may be in
  the form of colonies or filaments of independent
  cells.
• V. Their reproduction is primarily asexual, by
  fission.

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• III. Their mode of nutrition is mainly
  absorptive, but some are photosynthetic or
  chemosynthetic.

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• IV. They are usually nonmotile, but some may have
  flagella and gliding movements. Cilia are absent.

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• Monera includes heterogenous microorganisms
  including archaebacteria, eubacteria,
  actinomycetes and cyanobacteria.

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• (a) Archaebacteria (Archaeos old)
• Archaebacteria
• These are ancient bacteria which probably evolved
  3 billion years ago. And are now known as "living
  fossils".

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• They are able them to tolerate the extremes of
  heat and pH. They are divided into two
  sub-groups
• (i) Methanogens
• These are strictly anaerobic bacteria which
  produce methane (CH4) from CO2 and formic acid,
  hence the name. They are present in salty, marshy
  places, in the stomach of cattle and in organic
  matter or sewage. Methane gas produced in biogas
  plants is due to these bacteria. They are also
  called halophiles as they have an affinity for
  salt. They can cause spoilage of salted fish.

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• ii) Sulphur- dependent bacteria
• These are aerobic bacteria which convert sulphur
  either into sulphuric acid (H2SO4) or into
  hydrogen sulphide (H2S). Hence, they are present
  in hot sulphur springs. They can tolerate highly
  acidic pH (pH2) and high temperature (about 80o
  C). Hence, they are also called thermoacidophiles.

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• (b) Eubacteria (Eu true)
• These are "true" bacteria and are found
  practically in all the environments, at all the
  attitudes and depths, in extremely low and high
  temperature, in fresh as well as in marine water
  and in bodies of plants and animals both living
  and dead. In fact, it is difficult to name any
  place where bacteria are not found.

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• These are the general shapes

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• Shape and size
• They are unicellular microorganisms of various
  shapes and accordingly, they are called cocci
  (spherical), bacilli (rod-shaped), spirilla
  (spiral) and vibrios (broken spirals or comma
  shaped).
• Locomotion
• They are generally non-motile, but motile
  bacteria may have flagella at one end, at both
  ends, or all around the cell.

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• Cell structure
• They have a cell wall.
• Their cytoplasm is does not contain endoplasmic
  reticulum, mitochondria, Golgi complex and true
  plastids but does contain ribosomes.
• However, there are photosynthetic bacteria that
  have their chlorophyll spread on a membrane
  rather than in a plastid.

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• Respiration
• They are aerobic or anaerobic.
• Nutrition
• They are either autotrophic or heterotrophic.

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• Reproduction
• They reproduce both asexually as well as
  sexually.
• Asexual reproduction is by binary fission which
  takes place in favorable conditions, or by
  endospore formation, which takes place in
  unfavorable conditions. Sexual reproduction is by
  conjugation.

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Conjugation

• In addition to binary fission, bacteria sometimes
  share genetic material by a process called
  conjugation. There is a special set of genes that
  governs this. 
• Plasmids
• small circles of DNA floating in the cytoplasm

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Gotcha! One of the  bacteria sends out a
"grappling hook" and catches the other one! This
little hook is called a pilus.
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• The pilus draws the bacteria close to each
  other.,

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• The pilus becomes a tube and some of the little
  plasmids (small independent loops of 'DNA) cross
  over from one cell to the other cell.

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• The tube closes and the bacteria go on their way
  with some genetic material that they did not have
  before.
• These genes may find their way into the main DNA
  loop.
• This really happens!  You have heard of
  infections that become resistant to penicillin
  and that then pass their resistance to other
  infections and diseases.  This is how they do it!

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• Advantages
• Widely dispersed populations can still reproduce.
  
• Cells are identical to parents and should survive
  well if conditions don't change.
• Disadvantages
• Cells are identical to parents and so are
  vulnerable to the same environmental stresses.
• The characteristics of the cells change very
  slowly
• there is very little innovation in survival
  strategies.
• Unchanging cells may be slow to take advantage of
  new energy sources.

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• Role of Monera
• 1. Role in cycling Monera are chiefly
  decomposers. Life on earth would have run out
  were it not for the decomposition of dead matter
  by bacteria.

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• 2. Role in symbiosis Some forms show symbiotic
  relationship such as Rhizobium in the roots of
  leguminous plants or Nostoc and Anabaena in
  coralloid roots of Cycas, which fix free
  atmospheric nitrogen into nitrates, and
  Escherichia coli which inhabit the colon of the
  human intestine and help in synthesizing Vitamin
  B.

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• 3. Pathogenic forms Some Monera are also
  pathogenic, producing common diseases like
  typhoid, cholera, diphtheria, tuberculosis and
  pneumonia in human beings.

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Kingdom Protista

• (Eukaryotic single celled organisms)
• Some Protista

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• Protista includes all eukaryotic unicellular
  microorganisms, either plant-like or animal-like
  or showing overlapping characters of both plants
  and animals.
• They are mainly aquatic and widely distributed
  all over the world, occurring in oceans, lakes,
  ponds and damp soils.

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• They are autotrophic or heterotrophic.
  Heterotrophs are free-living or parasitic
  organisms. They are distinguished by the
  following characters

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• (i) They are first eukaryotes, having a well
  organized nucleus and complex membranous
  organelles.

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• (ii) They are unicellular or colonial forms
  without distinct division of labor.

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• (iii) They are autotrophic or heterotrophic
  showing varieties of metabolic systems.

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• (iv) Locomotion is by pseudopodia, flagella or
  cilia.

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• (v) They show mitosis, meiosis and simplest type
  of sexual reproduction for the first time. Common
  examples are Ameba, Paramecium, Euglena, diatoms
  and dinoflagellates.

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1. Cilia and flagella
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• Cilia are short and numerous and beat in a
  coordinated manner simultaneously or one after
  the other, while flagella are long and whip-like,
  showing undulating movements.
• Their function is to move the cell through the
  surrounding liquid medium or move the surrounding
  medium past the cells, gathering food particles.

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• All living organisms start their life with a
  single cell (zygote). In unicellular animals,
  cell division means reproduction which results in
  the formation of new organisms. In multicellular
  organisms, however, this cell further divides and
  so allows the cell to grow.

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Evolutionary precursors of complex life forms

• Protista is a diversified assembly of different
  groups of organisms which includes
• (A) Unicellular algae-like protista, e.g.
  Diatoms, Dinoflagellates etc.
• (B) Fungi-like protista, e.g. slime molds
• (C) Animal-like protista, e.g. protozoa

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(A) Diatoms

• These are microscopic, usually single-celled or
  colonial forms. They are found both in fresh
  water and salt water. In ocean they occur in vast
  assembly as floating plankton. They show a
  variety of patterns showing extreme beauty and
  symmetry because of which they are sometimes
  called "jewels of the plant world."

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Diatoms
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• General account The cell is made up of two
  overlapping, ornamental halves fitting together
  like two petri dishes. The cell is composed of
  silica and manganese instead of cellulose. They
  store food as oil which decreases their density.

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• Economic importance
• (1) The diatoms play an extremely important role
  in the aquatic food web. They are the most
  abundant component of marine plankton forming the
  primary food source of marine animals.
• (2) Being abundant, they help in releasing oxygen
  and maintaining the oxygen cycle.

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• (3) The imperishable siliceous cells of diatoms
  are deposited in various habitats. When dead,
  they form thick deposits of diatomaceous earth
  which is used as an ingredient in many commercial
  preparations such as detergents, polishes, paint
  removers, insulators, for decolorizing and
  deodorizing oils and also as fertilizers.

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• Diatomaceous earth The imperishable, siliceous
  dead cells of diatoms do not disintegrate but
  form thick deposits called diatomaceous earth or
  diatomite. It is procured from exposed deposits
  and lake bottoms. The largest deposits of
  diatomaceous earth are found in California. It is
  extending miles long and with average depth of
  425 meters.

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• Dinoflagellates These are one celled,
  biflagellate organisms, mostly marine and are
  important photosynthesizers. Some species are
  bioluminiscent, often seen in ocean waters at
  nights. They are commonly called fire algae as
  they emit red light.

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Red Algae Pyrrophyta
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• General account Their cell wall is made up of
  cellulose. Most species have two unequal flagella
  hence called dinoflagellates. One flagellum runs
  lengthwise and extends behind like a tail and
  another encircles the body like a belt, in a
  transverse groove. The rotating or spinning
  movements of dinoflagellates are due to these
  flagella. The photosynthetic species have
  plastids chlorophyll. They store food in the form
  of oil.

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Dinoflagellates
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• Common life-cycle Asexual reproduction takes
  place by simple cell division (fission) or by
  zoospore formation.
• Economic importance They form an important
  constituent of marine plankton and thus play an
  extremely important role in the aquatic food web.
• A number of dinoflagellates are toxic, forming
  red tides killing a number of fish. Some species
  cause dermatitis in swimmers. They reproduce both
  sexually and asexually.

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Slime molds

• General account Slime mold is a mass of
  protoplasm without a rigid cell wall. It creeps
  along the leaf-covered ground by ameboid
  movements and engulfs spores, bacteria and
  particulate debris of the forest floor on which
  it grows. It commonly reproduces by structures
  called fruiting bodies which produce spores.

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Protozoans
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• These are the protists which are more like
  animals. They are unicellular organisms found in
  fresh water, salt or any moist surroundings. They
  may be free living or parasitic, solitary or
  found in loose colonies.

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• General account They are distinguished by the
  following characteristics
• (i) The body is covered by a membrane and
  contains one or many nuclei.

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• (ii) They are generally motile. Locomotion is
  carried out by flagella, cilia or pseudopodia.

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• (iii) Most of them are heterotrophic though some
  are saprophytic and others parasitic in
  nutrition.
• (iv) They show different organelles (cell organs)
  like food vacuoles, contractile vacuoles.
• (v) They are sensitive to various external
  stimuli like touch, temperature, light etc.

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The protozoans fall into following four groups

• 1. Sarcodina They have no definite shape, move
  by pseudopodia and reproduce by binary fission.

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• Example Entamoeba These are ameba-like animals
  with one or two pseudopodia, single nucleus but
  no contractile vacuole. It includes a number of
  species which are parasitic. The best known is
  Entamoeba histolytica, which causes amebic
  dysentery.

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• 2. Mastigophora or flagellata They move by one
  or two whip-like structures called flagella and
  reproduce by longitudinal binary fission.

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• 3. Ciliophora They have definite shape, move by
  cilia and mostly possess two nuclei.

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• Example Paramecium A fresh water protozoon
  with definite shape like the sole of a slipper.
  Locomotion takes place by cilia. The animal has
  usually two nuclei and two contractile vacuoles.
  It reproduces by simple type of sexual
  reproduction called conjugation.

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• 4. Sporozoa These are parasitic forms. The
  movement organelles, food vacuoles and
  contractile vacuoles are absent.

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• Example Plasmodium An intracellular blood
  parasite causing malaria. The life cycle is
  completed in two hosts, namely man and mosquito.
• Economic importance Most of the protozoa are
  harmless but there are a few parasitic forms,
  such as Plasmodium, which causes malarial fever,
  Trypanosoma which develops sleeping sickness, and
  Entamoeba histolytica which causes dysentery.
  Protozoa are useful in sewage disposal.

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Symbiotic forms of Protista

• These are the organisms of different species
  which live in intimate relationship for mutual
  benefit. Some symbiotic forms are lichen, and
  Trichonympha in the intestine of termites.

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• 1. Lichen It is an obligatory association
  between, and plant, which together form a closely
  integrated unit called a lichen. The body of the
  lichen is composed of branching hyphae of the
  fungus which harbor algal cells. The fungus gets
  food synthesized by the alga while the alga in
  return gets shelter, moisture and minerals from
  the fungal partner.

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• Economic importance Lichens are used as food by
  human beings. They are also used in medicine, as
  dye stuffs for tanning hide into leather, etc.
  some like Usnea, are responsible for skin
  diseases, respiratory allergy etc.

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• 2. Root tubercles An obligatory association
  between plants and microbes, i.e. leguminous
  plant and the bacteria called Rhizobium. The
  latter are nitrogen fixing bacteria living in the
  root modules of leguminous plants like pea, bean,
  etc. Rhizobium fixes free nitrogen in the form of
  nitrates and makes it available to the plant and
  in return gets food and shelter from the latter.

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• 3. Termites and flagellates Several species of
  flagellates (protozoa) are found in the gut of
  termites where they participate in the digestion
  of wood. Termites feed on wood but are unable to
  digest it due to absence of proper enzymes. The
  flagellates present in the intestine digest wood
  with specific enzymes they secrete. The termites
  cannot survive without their intestinal
  flagellates

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