Transcript Kingdom Protista

Kingdom Protista
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• Protists are a diverse group of organisms,
comprising those eukaryotes that cannot be
classified in any of the other kingdoms as
fungi, animals, or plants. Either they are
unicellular, or they are multicellular without
highly specialized tissues.
• Protists were traditionally subdivided into
several groups based on similarities to the
"higher" kingdoms: the one-celled animal-like
, the plant-like (mostly one-celled algae),
and the fungus-like .
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Obtaining nutrients
• Protists obtain nutrients and digest
nutrients in a complex acquirement
and assimilation system.
Most protists also feed on bacteria.
• Protists acquire their food material
through internal digestion.
• They extend their cell wall and cell
membrane around the food material
to form a food vacuole in exocytosis
and cytoplasmic metabolic ingestion,
also sometimes pinocytosis.
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• The food vacuole is used to paralyze
the food material.
• It contains a grana-like texture that
can support the use of toxins to
paralyze organisms.
• The food vacuole extends from the
prey to inside the protist's cytoplasm
and the food material basically falls
through the vacuole through gravity
(similar to tropism in plants) and
enters the cell
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• A protist cell generally has an intestinal tract that is
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considerably small and is around the Golgi Apparatus.
Once the food is into the cell, it can be used by
ribosomes in the rough endoplasmic reticulum to be
manufactured into proteins.
Nutrition in some different types of protists is variable.
In flagellates, for example, filter feeding may
sometimes occur where the flagella find the prey.
In other multicellular protists, elements like nitrogen
and oxygen is acquired by constant beating of the
flagella.
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• Protists often occur in hydrophilic
conditions and thus have large
amounts of oxygen within them, which
is necessary for them to conduct
respiration and photosynthesis to
desirable levels.
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Organization
• Protozoa, the animal-like protests
• Protozoa are mostly single-celled, motile protists that feed by
phagocytosis, though there are numerous exceptions. They
are usually only 0.01–0.5 mm in size, generally too small to
be seen without magnification. Protozoa are grouped by
method of locomotion into:
•Flagellateswith long flagellae.g., Euglena
•Amoeboid with transient pseudopodia., Amoeba
•Ciliates with multiple, short ciliae.g., ParameciumSporozoa non-mobile
parasites; some can form sporese.g., Toxoplasma
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• Algae, the plant-like protists
• They include many single-celled organisms that are
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also considered protozoa, such as Euglena, which
many believe have acquired chloroplasts through
secondary endosymbiosis.
Others are non-motile, and some (called seaweeds)
are truly multicellular, including members of the
following groups:
Chlorophytesgreen algae, are related to higher
plantse.g., Ulva
Rhodophytesred algaee.g., Porphyra
Heterokontophytesbrown algae, diatoms, etc.e.g.,
Macrocystis
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• The green and red algae, along with a
small group called the glaucophytes,
appear to be close relatives of other
plants, and so some authors treat them as
Plantae despite their simple organization.
Most other types of algae, however,
developed separately.
• They include the haptophytes,
cryptomonads, dinoflagellates, euglenids,
and chlorarachniophytes, all of which have
also been considered protozoans.
• Note some protozoa host endosymbiotic
algae, as in Paramecium bursaria or
radiolarians, that provide them with
energy but are not integrated into the cell.
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• Fungus-like protists
• Various organisms with a protist-level
organization were originally treated as
fungi, because they produce sporangia.
These include chytrids, slime moulds, water
moulds, and Labyrinthulomycetes Of these,
the chytrids are now known to be related to
other fungi and are usually classified with
them.
• The others are now placed among the
heterokonts (which have cellulose rather
than chitin walls) and the Amoebozoa
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(which do not have cell walls).