Protists

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Protists

• Chapter 18

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What are protists?

• Common features

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Endosymbiosis/ Lynn Margulis

• Theory of endosymbiosis proposes that
  mitochondria originated as symbiotic, aerobic
  bacteria.
• Each mitochondrion has its own genome in a
  circular, closed molecule of DNA.
• divide by simple fission
• directed by nuclear genes

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Theory of Endosymbiosis
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The Protists

• The kingdom Protista is the most diverse kingdom
• Historically, organisms that do not fit
  comfortably into the other kingdoms have been
  placed within this kingdom.
• The junk drawer of the classification system.

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The Protists

• All protists are eukaryotes. This is the extent
  of their similarities.
• There have been movements in recent years to
  further divide the kingdom Protista into more
  kingdoms. This has had some success. There have
  been some regroupings at the phyla level.

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General Characteristics

• Mostly aerobic respirators
• Mostly motile during at least some stage
• Mostly chemoheterotrophs (algae excepted)
• Mostly aquatic (or at least favoring moist
  conditions
• Reproductively diverse
• All are eukaryotic

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Motility

• Most protists possess a flagella, cilia, or
  pseudopods during at least some portion of their
  life histories.
• Rhodophyta are an exception. This is in contrast
  with nearly all fungi which never possess
  flagella or cilia

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Chemoheterotrophic

• Most protists are chemoheterotrophs.
• Exceptions include the various algae.
• There are protists, the mixotrophs, that combine
  chemoheterotrophy with photoautotrophy using
  chloroplasts when light is available and
  absorbing nutrients when light is not available.
  Euglena is an example
• Animals and fungi are also chemoheterotrophs

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Aquatic

• Attach to non-floating aqueous surfaces (rocks or
  sand on the bottom of a body of water). These
  are described as benthic.
• Float within bodies of water. These are
  described as planktonic.
• Inhabit the body fluids of animals or plants.
  These are described as non-free living as well as
  parasitic.

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Aquatic Producers

• Phytoplankton (planktonic algae) and the
  prokaryote cyanobacteria are the bases of most
  marine and freshwater food webs.
• They account for at least half of the
  photosynthetic production of organic material
  globally.

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Reproduction

• Asexual reproduction solely via mitosis
• Sexual with no mitosis in the diploid state
• Alternation of generations
• Sexual protists display syngamy (two haploid
  cells fuse to form a diploid cell) and the life
  histories of many protists are further
  complicated by an ability to differentiate into
  cysts

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The Protists

• One way to artificially group the protists, or at
  least something to keep in mind as you study the
  protist kingdom, is by nutrient acquisition.

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The Protists

• Engulfers Obtain nutrients by engulfing
  particles of food. These are often called the
  protozoa. Also called phagotrophs.

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The Protists

• Nutrient absorbers non-fungus, non-animal
  eukaryotes that obtain their nutrients by
  absorption across their cell membrane. These are
  often referred to as the fungus-like protists.
  Also called osmotrophs.

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The Protists

• Photosynthesizers non-plant photosynthetic
  eukaryotes. Also called phototrophs.

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Aerobic Respirators

• Most protists are aerobic respirators, possessing
  mitochondria.
• Two examples are Pelomyxa palustris and Giardia
  lamblia.

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Protists

• Monera 3.5 billion years ago
• Protists 1.5 billion years ago
• Total of 9 phyla

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Protist Classification
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Animal Like

• Ciliophora
• Zoomastigina
• Sporozoa
• Sacrodina (amebas, heliozoans,radiolarians,
  foraminiferas)

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Plant like

• Euglenophyta
• Pyrrophyta
• Chrysphyta
• Slimemolds Acrasiomycota, Myxomycota

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Ciliophora

• Most members have large number of cilia
• About 8,000 species
• Live mostly in fresh water
• Use of a gullet to engulf food which is then
  encased in a vacuole to be digested.
• Solid waste is expelled via a cyotproct.

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Ciliophora

• Reproduction is both asexual and sexual
• Have two different nuclei
• Micronuclei contain normal chromosomes and
  function like the nuclei of other organisms
• Macronuclei DNA is divided into smaller pieces
  equivalent to single genes

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Ciliophora

• Asexual reproduction consists of transverse
  fission where the cell divides across its short
  axis
• This type of reproduction occurs for a limited
  number of generations, then the cells die if
  sexual reproduction has not occurred.

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Ciliophora

• The macronucleus controls the cell and contains
  over fifty copies of the cell's genes.
• The micronuclei are used in sexual reproduction
  where conjugation is used to increase the genetic
  variation of the organisms produced.

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Paramecium
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Paramecium
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Zoomastigina

• What does the name suggest?

Characteristics? Flagella Obtain food through
cell membrane Some can make gametes Some are
parasitic
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Phylum Zoomastigina

• Famous Flagelate
• Trichonympha

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Sporozoa

• All are parasitic
• Nonmotile
• Reproduction by means
• of spores

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Plasmodium
In the first stage of malaria infection,
mosquitoes inject worm-like sporozoites into
their human hosts as they feed on blood. When
the sporozoites invade liver cells, they mature
into merozoites. In the third stage, merozoites
infiltrate red blood cells and mature into
egg-like gametocytes. These then burst out of
blood cells and are sucked out of infected
individuals by feeding mosquitoes. Finally, the
gametocytes mature in mosquitoes and produce new
sporozoites, which the insect injects the next
time it feeds.
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Plasmodium Life Cycle
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Sacrcodina

• Protists with fake teeth
• Pseudopods
• Binary fission
• Amebas, Heliozoans, Radiolarians, Foraminifers

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Amoebas
Draw an Amoeba and identify its parts page 389,
figure 18-2
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Sarcodina/ Radiolarians

• Check Haeckel's Kunstformen der Natur (1904)
  Illustrations!!

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Heliozoans
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Foraminers
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Written activity

• Read and answer questions on page 391
• 14 points, please complete sentences.

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Plant Like Protists

• Eugenophyta
• Pyrrophyta
• Chysphyta
• Acrasiomycota
• Myxomycota

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Eugenophyta

• Flagellates with chloroplasts

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Euglenozoa

• Some members photosynthesize, but are not
  classified with the algae.
• Some sources have made this group a kingdom level
  group.

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Euglenozoa

• Euglenoids
• most are freshwater
• about one-third are autotrophic
• pellicle lies within membrane
• stigma - light sensitive organ that aids in
  orienting toward light
• Euglena
• two flagella attached to reservoir
• contain numerous chloroplasts

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Euglenozoa
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Euglenozoa

• Kinetoplastids
• unique, single mitochondrion in each trypanosome
• Trypanosomes are kinetoplastids that cause many
  serious human diseases.
• African sleeping sickness
• Chagas

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Pyrrophyta

• The fire protists
• Their DNA do not contain the common protein
  histone
• They have bioluminescence
• One such group is the Dinoflagellates

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Dinoflagellates
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Dinoflagellates
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Dinoflagellates

• Typically photosynthetic
• Some non-photosynthetic parasitic forms exist
• Typically Planktonic
• Typically unicellular
• Two flagella that beat within perpendicular
  grooves.
• Cause red tides, an explosive growth. These
  dinoflagellates produce a neurotoxin that is
  concentrated by shellfish.

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ChrysophytaGolden Protist

• Yellow green algae
• Golden brown algae
• diatoms

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Bacillariophyta

• Diatoms
• Photosynthetic and planktonic
• Have chlorophylls a and c as well as carotenoids.
  Have a yellow to brown color
• Have overlaping glass like walls of hydrated
  silica
• Exhibit either radial or bilateral symmetry
• Asexual and sexual reproduction. Read about
  shell formation.

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Diatoms
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Diatom
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Diatom
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Diatom
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Phaeophyta

• Brown Algae
• Largest and most complex of the algae
• Same photosynthetic pigments as Bacillariophyta
• All are multicellular, most are marine
• Kelp is a brown algae
• Many seaweeds are brown algae along with
  Rhodophyta and Chlorophyta

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Phaeophyta

• Used as food in many parts of Asia
• Used as thickeners for processed food
• Agar extracted from brown algae and used as a
  growth medium for bacteria

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Phaeophyta

• Life cycle involves alternation of generations,
• Sporophyte the large, dominant, diploid form.
  Gametophyte haploid and is much smaller.
• Sporangia produce haploid spores. These spores
  undergo mitosis to produce gametophytes. One
  type of gametophyte produces sperm, another
  produces eggs.
• After fertilization, the zygote grows into the
  mature sporophyte

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Sargassum
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Rhodophyta

• Red Algae
• Primarily warm, tropical, marine inhabitants
  although some are found in fresh water and soil
• Photosynthetic have chlorophyll a, carotenoids,
  and phycobillins.
• Lack flagella throughout life cycle

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Rhodophyta

• Phycobillins are adept at absorbing green,
  violet, and blue light. These wavelengths
  penetrate into deep water.
• Reproduction involves alternation of generations
  similar to the Phaeophyta

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Chlorophyta

• Green algae
• Photosynthetic
• Chloroplasts contain chlorophylls a and b and
  carotenoids. Similar to the chloroplasts of
  plants.
• Adapted to shallow water
• Marine and freshwater species

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Chlorophyta

• Green algae are the ancestors of the plant
  kingdom.
• extensive fossil record dating back 900 million
  years
• mostly aquatic
• Chlamydomonas well-known genus
• probably represents primitive state
• Chlorophyta did not give rise to land plants.

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Chlorophyta

• Most Chlorophyta have complex life histories with
  both sexual and asexual reproductive stages.
• Nearly all reproduce sexually by way of
  biflagellated gametes.
• Most, but not all display alternation of
  generations.
• Gametophyte form (haploid) is dominant

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Chlamydomonas Life Cycle
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Choanoflagellida

• Choanoflagellates are most like the common
  ancestor of the sponges.
• contain a single emergent flagellum surrounded by
  a funnel-shaped, contractile collar

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Rhizopoda(Amoebas)

• All are unicellular, some are parasites
• Found in fresh water, marine environments and
  soil
• Lack cell walls, flagella, meiosis
• Reproduction is solely by fission
• All employ pseudopodia to move or to obtain food.
  Protista that have pseudopods are amoebas and
  foraminifera. Slime molds have amoeboid stage
  but are not rhizopods

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Foraminifora

• All unicellular
• Mostly marine
• Most benthic but some planktonic
• Calcium carbonate shells
• Complex cycle consisting of alternation of
  generations.

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Forams
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Mycetozoa

• Acrasiomycota New name is Dictyostelida
  (cellular slime molds)
• Myxomycota New name is Myxogastrida (Plasmodial
  slime molds)

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Acrasiomycota

• About 70 Species. Common in fresh water, damp
  soil, rotting vegetation
• Individual organisms behave as separate amoebas.
  Move through soil ingesting bacteria and other
  small organisms.
• When the food runs out the amoebas aggregate and
  form a moving mass that eventually transforms
  into a spore containing mass called a sorocarp.

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Acrasiomycota

• The amoebas become encysted as spores.
• Some amoebas fuse sexually to form macrocysts
  which have diploid nuclei in which meioses
  occurs. Haploid amoebas are then released
• Single amoebas are haploid.
• The sorocarp is considered multicellular.

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Myxomycota

• Plasmodial slime molds
• Some scientists have started to group these with
  the cellular slime molds
• Feeding stage consists of a motile,
  multinucleated, amoeboid mass called a plasmodium
  (don't confuse plasmodium with Plasmodium, the
  genus that causes malaria)

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Myxomycota

• The feeding stage of the life cycle consists of
  solitary cells that function individually.
• When there is no more food, the cells form an
  aggregate that functions as a unit.

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Myxomycota

• Although the mass of cells resembles a cellular
  slime mold, the important distinction is that the
  cells of cellular slime molds retain their
  identity and remain separated by their membranes.
• Plasmodial slime molds form a multinucleate mass.

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Summary of the Kingdoms

• Archaezoa
• Diplomonads
• Parabasalid
• Microsporidians
• Euglenozoa
• Euglenoids
• Zoomastigina

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• Alveolata
• Dinoflagellates
• Apicomplexans (Sporozoa)
• Ciliates
• Rhizopoda
• Amoebas
• Foraminifera
• Mycetozoa
• Acrasiomycota
• Myxomycota

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• Stramenopila
• Oomycota
• Bacillariophyta
• Phaeophyta
• Rhodophyta
• Rhodophyta
• Chlorophyta
• Chlorophyta