Kingdom Protista Notes

 

1. Describe the characteristics used to classify protists.

 

Domain Eukarya

Kingdom Protista – eukaryotes

 

I.                    Plant-like Protists – Algae

Classified according to:

                                                            1.      pigment

                                                            2.      cell wall structure

                                                            3.      locomotion

                                                            4.      stored food

 

A.     Phylum Euglenophyta

Pigment: chlorophyll

Cell wall:  no cell wall

Locomotion: flagella

Stored food:  paramylon starch

Example:  Euglena

Fact to remember:  The euglena is unusual in that it is a photosynthetic autotroph in light, but if the environment becomes dark for an extended period of time it will become a heterotroph.

 

B.     Phylum Pyrrophyta – fire algae (protists)  dinoflagellates

Pigment:  chlorophyll

Cell wall:  cellulose

Locomotion:  2 flagella (dinoflagellates)

Example:  Noctilucans – a bioluminescent dinoflagellate

Example:  Gonyaulax – causes red tides

Fact to remember:  A red tide is an algal bloom, a population explosion of Gonyaulax.  Gonyaulax produces a neurotoxin that accumulates in shellfish which are filter feeders.  Shellfish are invertebrates and are unharmed by the neurotoxin.  Vertebrates that feed on the shellfish, including people, are poisoned by the neurotoxin and can even die.

 

C.     Phylum Chrysophyta – golden algae (protists)

Pigment:  chlorophyll and fucoxanthin (brown)

Cell walls:  pectin instead of cellulose

Stored food:  oil

Example:  Diatoms – the most abundant photosynthetic organisms in the ocean

Fact to remember:  Diatoms contain silicon in their cell walls.  The cell walls accumulate on the sea floor as diatomaceous earth.  Diatomaceous earth is used in cleansers, toothpaste, reflective paint and pesticides.

 

 

 

D.     Phylum Chlorophyta – green algae

Pigment:  chlorophyll

Cell walls:  cellulose

Stored food:  starch

Examples:  desmids and Chlamydomonas – unicellular

Volvox – colonial

Spirogyra – fiamentous

 

E.      Phylum Phaeophyta – brown algae

Pigment:  chlorophyll and fucoxanthin

Stored food:  oil

Example:  Kelp – Parts of Kelp:  holdfast, stipe, blade, air bladder

Sargassum – gives name to the Sargasso Sea in the Atlantic Ocean.  Sargassum forms marine habitat for young sea turtles and developing marine organisms and larval stages.

 

F.      Phylum Rhodophyta – Red algae

Pigment:  chlorophyll, phycobilins, and phycoerythrin

Example:  coralline algae – form marine habitat similar to coral reefs

Fact to remember:  Carageenans produced by red algae are used as thickening agents in food such as ice cream.

Red algae can survive at great depths because the pigments they contain allow them to use wavelengths of light that penetrate deeper into the water so they can carry out photosynthesis.

More than 70% of photosynthesis occurs on the ocean surface by phytoplankton which is composed of many of the plant-like protists, especially diatoms.

 

II.                 Animal -like Protists – Protozoans

Heterotrophic

            Classified by means of locomotion

 

1. Phylum Ciliophora – Ciliates – the fastest protists

Locomotion:  cilia – short, numerous, hairlike projections that work together

Example:  Paramecium

Feeding in the Paramecium:  Cilia sweep food into the oral groove. It passes into the gullet, then into a food vacuole at the base of the gullet.  The food is digested in the food vacuole and distributed throughout the paramecium.  Wastes leave through the anal pore.

Conjugation in the Paramecium:  Paramecia have two different types of nuclei; micronuclei and macronuclei.  During conjugation the micronucleus undergoes meiosis forming two haploid micronuclei.  Two paramecia join at the oral groove and exchange a haploid micronucleus.  The haploid micronucleus fuses with the other original haploid micronucleus to form a single diploid micronucleus.

 

2. Phylum Zoomastigina – flagellates

Locomotion:  flagella – long, whiplike structures that are few in number

Examples:  Trypanosoma – causes African sleeping Sickness; vector: tsetse fly

Trichonympha – symbiotic relationship with termites to digest cellulose

 

3. Phylum Sporozoa

Locomotion:  none – all are internal parasites

Example:  Plasmodium – causes malaria; vector: Anopheles Mosquito

 

4. Phylum Sarcodina

Locomotion:  pseudopodia – false feet, extensions of cytoplasm

Example:  amoeba – feeds by phagocytosis, wastes exit by exocytosis

Facts to remember:  fossilized foraminiferans are used to locate oil

Entamoeba causes amoebic dysentery

 

III.               Fungus-like Protists – Slime Molds

Protozoan-like feeding stage

Fungus-like reproductive stage

Classified by the reproductive stage

Function as saprophytes and recycle nutrients

 

A.     Phylum Acrasiomycota – cellular slime molds

Reproduction:  Under unfavorable conditions myxamoebae (unicellular) release acrasin.  Acrasin attracts other myxamoebae.  Myxamoebae join together to form a pseudoplasmodium.  The pseudoplasmodium is sessile.  It forms spores that produce myxamoebae.

 

B.     Phylum Myxomycota – plasmodial slime molds

Repoduction: A plasmodium is a multinucleate structure that is sessile and produces spores.  The spores germinate to form swarm cells which fuse to form myxamoebae.  The myxamoeba undergoes mitosis without cytokinesis to form the coenocytic plasmodium.

 

Medical and Economic Importance of Protists

 

            The medical importance of protists includes protozoans that cause diseases such as malaria, African Sleeping Sickness, and dysentery.  Dinoflagellates that cause red tides that harm marine vertebrates and become concentrated in shellfish which then can’t be harvested, which is also an economic importance.  Foraminiferans are used to locate oil, which is an economic importance.  Phytoplankton produce 70% of atmospheric oxygen.  Carageenans from red algae are used in food production.  Protists are at the base of many food chains, providing an essential link in the ecosystem as a whole.  Slime molds act as saprophytes returning nutrients to the various cycles.  Certain algae form marine habitat.  Diatomaceous earth is used in cleansers, toothpaste, reflective paint and as an organic pesticide.