PROTISTS

What is a protist?

- A one or many celled organism that lives in moist or wet surroundings.

  • Eukaryotic
  • Nucleus
  • Internal membrane-bound membranes
  • Some are plant like & contain chlorophyl
  • Some are animal like & get their food from capturing other organisms

Reproduction:

  • Asexual: mitosis & cell division
  • Sexual: meiosis

Plantlike Protists

  • Many have cell walls
  • No roots
  • ALGAE

Groups of Plantlike Protists

Diatoms: extremely large populations, glass-like skeletons

Dinoflagellates - "spinning flagella" Flagella - long, thin, whiplike structure used for movement, Bioluminescent

Euglenoids - have characteristics of both plants & animals, some have chloroplasts, feed on bacteria when light isn't present, no cell wall but has a strong, flexible layer inside the cell membrane, many have a flagella, many have an eyespot sensitive to light

Red Algae - many celled, "seaweed", contain chlorophyll & lots of red pigment, can live up to 200m deep in the ocea

Green Algae - 7,000 species, lots of chlorophyll, 1 or many celled, most plant-like, many environments including water & anywhere damp

Brown algae - chlorophyll & brown pigment, usually in cool, saltwater environments, food source for many fish & invertebrates, kelp

ANIMAL-LIKE PROTISTS

  • PROTOZOAN - one-celled, animal-like protists.
  • Classed by how they move.
  • Live on or in other living or dead organism
  • Water & soil
  • Specialized vacuoles for digesting food & getting rid of excess water

Ciliates

  • Cilia = short, threadlike structures that extend from the cell membrane
  • Can be covered in cilia or have cilia grouped in specific areas
  • Work like rowboat oars
  • 2 nuclei:
  • Micronucleus - used in reproduction
  • Macronucleus - controls feeding & exchanged of oxygen & carbon dioxide, amount of water & salts entering & leaving
  • Feed on bacteria
  • Food is digested in a vacuole & excreted through the anal pore.

Flagellates

  • Move by whipping a long flagella
  • Many freshwater species
  • Some parasites
  • Some live in colonies

Pseudopods

  • Move using a "false foot"
  • Appear to flow
  • Fresh & salt water environments
  • Some are parasitic
  • Some may have hard shells

Other Protozoans: Plasmodium

FUNGUSLIKE PROTISTS

Slime Molds

  • Form delicate web-like structures on their food source
  • Have some protozoan characteristics
  • Move by means of pseudopods & behave like amoebas during part of their life cycle
  • Found on decaying logs, dead leaves, moist, cool, shady environments

Water Molds & Downy Mildews

  • Live in water or on moist places
  • Grow as a mass of threads over plants or animals
  • Digestion takes place outside the protist then they absorb the oragnism's nutrients
  • Have a flagella
  • Cell walls resemble fungi
  • Some are parasites, some are scavengers
  • Downy mildews on plants (Irish potato famine)

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