Kingdom Protista

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Kingdom Protista

• The Catch-all Kingdom

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• Characteristics of Protists. . .
• They are a diverse group of eukaryotic organisms
• Have true nuclei and other membrane-bound
  organelles

• Their size varies from single-celled protozoa to
  60 meter kelps
• Most are single-celled some are colonial some
  are coenocytic (multinucleate but not
  multicellular) some are multicellular
• Many live in hypotonic conditions and regulate
  water by contractile vacuoles
• Others limit water absorption by having rigid
  cell walls

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• Various methods of obtaining nutrients. . .
• Autotrophic protists photosynthesize
• Some heterotrophic protists obtain food by
  absorption
• Other heterotrophic protists ingest their food
• Some (like Euglena) can alternate between
  autotrophism and heterotrophism
• Most protists are aerobic, utilizing mitochondria
  for food metabolism
• Most protists are free-living, but some are
  involved in symbiotic relationships like
  mutualism or parasitism

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• Most protists are aquatic, either floating freely
  as plankton, or attached to surfaces some are
  terrestrial living in damp places.
• Reproduction in protists. . .
• All reproduce asexually.
• Many can reproduce sexually with meiosis and
  syngamy (gamete fusion).
• Most do not form multicellular sex organs or
  embryos
• Locomotion - most are motile
• Some move by amoeboid motion
• Others move by flexing individual cells
• Others move by waving flagella or cilia
• Some are nonmotile

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Survey of Representative Protist groups

• The Protozoa

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• General characteristics of Protozoa. . .
• They are unicellular, but definitely not simple
• They are heterotrophic with most using ingestion.
• They are structurally complex

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• Phylum Sarcomastigophora (sometimes grouped
  separately as Zoomastigina - the flagellates and
  Sarcodina - the amoeboid protozoans)
• General characteristics. . .
• The Sarcomastigophora have flagella, pseudopodia,
  or both
• Have predominately one type of nucleus
• Do not form spores
• Primarily reproduce asexually, but gametes are
  sometimes formed.

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The Flagellates (Zoomastigina)

• The body shape is spherical or elongate
• Have a single central nucleus
• Have one to many flagella
• Some are amoeboid and eat by forming pseudopods
• Some have oral groove or cytopharynx and
  specialized organelles for processing food.

Flagellates such as Trypanosoma (above) may cause
sickness in humans.
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Amoeboid Protozoa (Sarcodina)

• Many have no definite body shape, changing as
  they move
• Reproduce asexually
• Move by means of pseudopods
• Use pseudopods to capture food - forming a food
  vacuole that receives digestive enzymes from
  lysosomes
• Some cause disease and infections in humans such
  as amoebic dysentery

http//wolfbat359.com/phagocytosis2.html
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Foraminifera

• Foraminiferans produce calcified shells(tests)
• Dead foraminiferans sink to the ocean floor and
  are eventually transformed into chalk
• These organisms are used as indicators of
  geophysical changes in the environment.
• The White Cliffs of Dover England are the
  result of foraminifera shells

Foraminifera test (shell)
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Actinopods

• Actinopods have long, slender projections called
  axopods that protrude through pores in their
  skeleton
• Axopods are used to capture prey
• Many contain symbiotic algae
• They produce elaborate skeletons of silica
• They eventually sink to the ocean floor and
  become sedimentary rock

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• Phylum Ciliophora
• They have a definite but flexible shape due to a
  flexible outer pellicle
• The surface of Paramecium is covered with cilia
  that extend through pores in the pellicle and
  permit movement
• Many ciliates possess trichocysts, organelles
  that can discharge filaments believed to aid in
  trapping and holding prey
• Most ingest their food
• They are not photosynthetic some have symbiotic
  algae within their cells
• Have at least two nuclei per cell - one or more
  micronuclei (controls reproduction) and a single
  macronucleus (controls metabolism)

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Paramecium
http//bio.rutgers.edu/gb101/lab6_protists/r6a2pa
ramec.html
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• Most ciliates are capable of conjugation (sexual
  reproduction)
• In Paramecium, two individuals of different
  mating types press their oral surfaces together
• The macronuclei disintegrates micronuclei
  undergo meiosis, forming in each organism four
  haploid nuclei, three of which disintegrate
• The remaining nucleus in each organism divides
  mitotically
• One nucleus from each individual crosses over
  into the other organism and fuses with the
  haploid nucleus already there
• The organisms separate and the fused micronuclei
  undergo three mitotic divisions to produce eight
  micronuclei
• Four of the micronuclei develop into macronuclei
  three micronuclei degenerate, and one remains
  functional
• Paramecium and micronucleus divides twice
  asexually

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Not all ciliates are motile some are stalked
some can swim but are more likely to remain
attached to the substrate. Examples of these
stalked ciliates would be Stentor and Vorticella.
Vorticella
Stentor
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Phylum Apicomplexa (Sporozoa)

• Nonmotile and parasitic

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• The sporozoa are a large group of parasites that
  associated with human diseases.
• They do not have organelles for locomotion or
  contractile vacuoles.
• They move by flexing.
• Many species form spores, the infective agent for
  the next host.
• They often spend part of their life in one host
  species, and part in another.

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• Plasmodium causes malaria
• sporozoites enter the human bloodstream through
  an Anopheles mosquito bite
• The sporozoites enter liver cells and divide to
  produce merozoites that infect red blood cells
• In the blood cells, the merozoites divide to form
  more merozoites, which infect more red blood
  cells. Some merozoites form gametocytes, which
  can be transmitted to another mosquito through a
  bite
• Gametocytes pulled into a mosquitos digestive
  tract, develop into gametes and fertilization
  occurs.
• The zygote embeds in the mosquitos stomach
  lining and produces sporozoites, which are
  released and migrate to the salivary glands where
  they will be injected into a human with the next
  bite.

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