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Protists Notes

Protistas

  • Informal name for a group of eukaryotic organisms that are difficult to classify.

  • Belong to the Domain Eucaria.

  • Mostly unicellular and microscopic.

  • Genetic evidence shows that some are more related to plants, animals, or fungi than to other protists.

  • The protist group is like the drawer where we put everything we don't know where it goes.

Diversity in Protists

  • The group with the greatest structural and functional diversity of eukaryotes.

  • Unicellular and multicellular organisms.

  • Some organisms form colonies.

  • Sexual, asexual, or both types of reproduction.

  • Can live in terrestrial or aquatic environments, inside other organisms, or in dead organic matter.

  • Nutritional diversity:

    • Photoautotrophs: Have chloroplasts and perform photosynthesis.

    • Heterotrophs: Need to feed on organic matter.

    • Mixotrophs: Combine photosynthesis with heterotrophic nutrition.

General characteristics of Eukaryotes

  • Nucleus: Contains the genetic material, separated from the cytoplasm by a membrane.

  • Organelles: Each performs specific functions.

  • Mitochondria: Organelle specialized in aerobic respiration.

  • Cytoskeleton: Allows the cell to alter its shape to move, eat, and grow.

  • Carry out Mitosis.

  • Chromosomes organized by histones.

Evolution of eukaryotic organisms

  • Endosymbiosis: Relationship between two species in which one organism lives inside the cells of the other organism (the host).

  • Mitochondria and chloroplasts are derived from prokaryotic organisms that were swallowed by the ancestor of eukaryotic cells.

  • Mitochondria: Endosymbiosis of an alpha proteobacteria (aerobic).

  • Chloroplasts: Endosymbiosis of a cyanobacteria (photosynthetic).

  • "Protoeukaryotic" host cell: Related to archaea.

Endosymbiosis

  • Folds in the plasma membrane give way to the first organelles in a proto-eukaryotic cell.

  • First endosymbiosis: the cell swallows an aerobic bacterium that will become the mitochondrion.

  • Second endosymbiosis: the eukaryotic cell swallows a cyanobacterium that will become the chloroplast.

Secondary endosymbiosis

  • Plastid

  • Green alga

  • Euglenids

  • Inner plastic membrane

  • Chlorarachniophytes

  • Nucleomorph

  • Outer plastid membrane

  • Nuclear pore-like gap

  • Dinoflagellates

  • Red alga

  • Plastid

  • Stramenopiles

Evidence for the theory of endosymbiosis

  • Mitochondria:

    • Have their own DNA, a circular chromosome.

    • Ribosomes and tRNA very similar to those of prokaryotes.

    • Their shape is the same as that of alpha-proteobacteria.

    • Double membrane.

    • Divide independently of the eukaryotic cell by binary fission.

    • Has lost genes, which explains why it cannot live independently.

  • Chloroplasts:

    • Have their own DNA, a circular chromosome.

    • Ribosomes similar to those of cyanobacteria.

    • Double membrane and some a layer of peptidoglycan between both membranes.

    • Divide independently of the eukaryotic cell by binary fission.

    • Has lost genes, which explains why it cannot live independently.

Four supergroups of Eukaryotes

  • Archaeplastida

  • Unikonta

  • SAR (Stramenopila, Alveolata, Rhizaria)

  • Excavata (Formerly called Discova)

Archaeplastida (Green and red algae)

  • Autotrophs.

  • Unicellular, unicellular that live in colonies, and multicellular.

  • Sexual and asexual reproduction.

  • Cell walls with cellulose.

  • Life cycle alternation of generations.

  • Group that includes terrestrial plants.

Amoebozoa

  • Heterotrophs.

  • Many show lobed pseudopods that they use to move and eat (phagocytosis).

  • Some are parasites.

  • Unicellular and multicellular.

  • Sexual and asexual reproduction.

  • Includes Slime molds.

  • Amoeba movement by pseudopods

    • This type of movement is possible thanks to the cytoskeleton that these organisms possess.

Opisthokonta

  • Heterotrophs.

  • Name comes from its single flagellum in the posterior part.

  • The protists in this group are unicellular and colonial.

  • Includes choanoflagellates.

  • Filters.

  • Sexual and asexual reproduction.

  • Aquatic.

Rhizaria

  • Heterotrophs and mixotrophs.

  • Some have gained organelles by secondary endosymbiosis.

  • Includes amoebas with fine pseudopods like needles or threads.

  • Some create calcium carbonate or silica armor.

  • All unicellular.

  • Sexual and asexual reproduction.

  • Aquatic and some parasitic.

Chromalveolates

  • Includes Alveolates and Stramenopiles.

  • Arise from secondary endosymbiosis with a red algae.

  • Some have lost this plastid.

  • Autotrophs, heterotrophs, and mixotrophs.

  • Unicellular and multicellular.

  • Sexual and asexual reproduction.

  • Complex life cycles.

  • Aquatic and some parasitic.

Alveolates

  • They are characterized by having membrane-bound sacs (alveoli) just below the plasma membrane.

  • This group includes:

    • Dinoflagellates

    • Apicomplexes

    • Ciliates

Alveolates: Dinoflagellates

  • red tide

  • Bioluminescent bays

Alveolates: Apicomplexes

  • All are parasites of animals and some cause serious diseases.

  • One end of the cell contains a complex of organelles specialized to penetrate host cells.

  • They have complex life cycles.

  • Require two or more hosts to complete it.

Life cycle of Plasmodium

  • Apicomplex that causes malaria.

  • It has two hosts: Mosquito of the genus Anopheles and Humans

Alveolates: Ciliates

Stramenopiles

  • Includes some of the most important photosynthetic organisms on the planet.

    • Diatoms

    • Golden algae

    • Brown algae

  • Important producers of O2O_2$$O_2$$ on the planet.

  • Sequester carbon at the bottom of the sea for a long time.

  • Unicellular and multicellular.

Stramenopiles: Brown algae

  • Pneumatocysts: air-filled vesicles that allow these algae to float in the water

Excavata

  • General characteristics

    • Feeding grooves (excavated).

    • Multiple flagella.

    • Autotrophs, heterotrophs, mixotrophs and some parasitic.

Excavata: Euglenozoas

  • Protists commonly found in pond waters.

  • They have two flagella that emerge from one side of the cell.

  • They are mixotrophs.

  • They have no cell wall.


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Protists Notes

Protistas

  • Informal name for a group of eukaryotic organisms that are difficult to classify.
  • Belong to the Domain Eucaria.
  • Mostly unicellular and microscopic.
  • Genetic evidence shows that some are more related to plants, animals, or fungi than to other protists.
  • The protist group is like the drawer where we put everything we don't know where it goes.

Diversity in Protists

  • The group with the greatest structural and functional diversity of eukaryotes.
  • Unicellular and multicellular organisms.
  • Some organisms form colonies.
  • Sexual, asexual, or both types of reproduction.
  • Can live in terrestrial or aquatic environments, inside other organisms, or in dead organic matter.
  • Nutritional diversity:
    • Photoautotrophs: Have chloroplasts and perform photosynthesis.
    • Heterotrophs: Need to feed on organic matter.
    • Mixotrophs: Combine photosynthesis with heterotrophic nutrition.

General characteristics of Eukaryotes

  • Nucleus: Contains the genetic material, separated from the cytoplasm by a membrane.
  • Organelles: Each performs specific functions.
  • Mitochondria: Organelle specialized in aerobic respiration.
  • Cytoskeleton: Allows the cell to alter its shape to move, eat, and grow.
  • Carry out Mitosis.
  • Chromosomes organized by histones.

Evolution of eukaryotic organisms

  • Endosymbiosis: Relationship between two species in which one organism lives inside the cells of the other organism (the host).
  • Mitochondria and chloroplasts are derived from prokaryotic organisms that were swallowed by the ancestor of eukaryotic cells.
  • Mitochondria: Endosymbiosis of an alpha proteobacteria (aerobic).
  • Chloroplasts: Endosymbiosis of a cyanobacteria (photosynthetic).
  • "Protoeukaryotic" host cell: Related to archaea.

Endosymbiosis

  • Folds in the plasma membrane give way to the first organelles in a proto-eukaryotic cell.
  • First endosymbiosis: the cell swallows an aerobic bacterium that will become the mitochondrion.
  • Second endosymbiosis: the eukaryotic cell swallows a cyanobacterium that will become the chloroplast.

Secondary endosymbiosis

  • Plastid
  • Green alga
  • Euglenids
  • Inner plastic membrane
  • Chlorarachniophytes
  • Nucleomorph
  • Outer plastid membrane
  • Nuclear pore-like gap
  • Dinoflagellates
  • Red alga
  • Plastid
  • Stramenopiles

Evidence for the theory of endosymbiosis

  • Mitochondria:
    • Have their own DNA, a circular chromosome.
    • Ribosomes and tRNA very similar to those of prokaryotes.
    • Their shape is the same as that of alpha-proteobacteria.
    • Double membrane.
    • Divide independently of the eukaryotic cell by binary fission.
    • Has lost genes, which explains why it cannot live independently.
  • Chloroplasts:
    • Have their own DNA, a circular chromosome.
    • Ribosomes similar to those of cyanobacteria.
    • Double membrane and some a layer of peptidoglycan between both membranes.
    • Divide independently of the eukaryotic cell by binary fission.
    • Has lost genes, which explains why it cannot live independently.

Four supergroups of Eukaryotes

  • Archaeplastida
  • Unikonta
  • SAR (Stramenopila, Alveolata, Rhizaria)
  • Excavata (Formerly called Discova)

Archaeplastida (Green and red algae)

  • Autotrophs.
  • Unicellular, unicellular that live in colonies, and multicellular.
  • Sexual and asexual reproduction.
  • Cell walls with cellulose.
  • Life cycle alternation of generations.
  • Group that includes terrestrial plants.

Amoebozoa

  • Heterotrophs.
  • Many show lobed pseudopods that they use to move and eat (phagocytosis).
  • Some are parasites.
  • Unicellular and multicellular.
  • Sexual and asexual reproduction.
  • Includes Slime molds.
  • Amoeba movement by pseudopods
    • This type of movement is possible thanks to the cytoskeleton that these organisms possess.

Opisthokonta

  • Heterotrophs.
  • Name comes from its single flagellum in the posterior part.
  • The protists in this group are unicellular and colonial.
  • Includes choanoflagellates.
  • Filters.
  • Sexual and asexual reproduction.
  • Aquatic.

Rhizaria

  • Heterotrophs and mixotrophs.
  • Some have gained organelles by secondary endosymbiosis.
  • Includes amoebas with fine pseudopods like needles or threads.
  • Some create calcium carbonate or silica armor.
  • All unicellular.
  • Sexual and asexual reproduction.
  • Aquatic and some parasitic.

Chromalveolates

  • Includes Alveolates and Stramenopiles.
  • Arise from secondary endosymbiosis with a red algae.
  • Some have lost this plastid.
  • Autotrophs, heterotrophs, and mixotrophs.
  • Unicellular and multicellular.
  • Sexual and asexual reproduction.
  • Complex life cycles.
  • Aquatic and some parasitic.

Alveolates

  • They are characterized by having membrane-bound sacs (alveoli) just below the plasma membrane.
  • This group includes:
    • Dinoflagellates
    • Apicomplexes
    • Ciliates

Alveolates: Dinoflagellates

  • red tide
  • Bioluminescent bays

Alveolates: Apicomplexes

  • All are parasites of animals and some cause serious diseases.
  • One end of the cell contains a complex of organelles specialized to penetrate host cells.
  • They have complex life cycles.
  • Require two or more hosts to complete it.

Life cycle of Plasmodium

  • Apicomplex that causes malaria.
  • It has two hosts: Mosquito of the genus Anopheles and Humans

Alveolates: Ciliates

Stramenopiles

  • Includes some of the most important photosynthetic organisms on the planet.
    • Diatoms
    • Golden algae
    • Brown algae
  • Important producers of O2O_2 on the planet.
  • Sequester carbon at the bottom of the sea for a long time.
  • Unicellular and multicellular.

Stramenopiles: Brown algae

  • Pneumatocysts: air-filled vesicles that allow these algae to float in the water

Excavata

  • General characteristics
    • Feeding grooves (excavated).
    • Multiple flagella.
    • Autotrophs, heterotrophs, mixotrophs and some parasitic.

Excavata: Euglenozoas

  • Protists commonly found in pond waters.
  • They have two flagella that emerge from one side of the cell.
  • They are mixotrophs.
  • They have no cell wall.