Protists
Protists
• eukaryotic organisms that cannot be classified
as fungi, plants, or animals.
• Most are unicellular
• Offer clues about the evolution of fungi,
plants, and animals
• http://biology.unm.edu/ccouncil/Biology_203
/Summaries/Protists.htm
Reproduction
Asexual Reproduction:
gametes- reproductive cells required during
sexual reproduction.
*haploid cells that join together to form a
diploid zygote.
• Protists can reproduce asexually by binary
fission, budding, and fragmentation.
• Protists can also reproduce sexually by fusion
of gametes.
Types of Asexual Reproduction
• Binary fission- occurs when a unicellular organism
reproduces by splitting in half after replicating its DNA.
• Budding- a form of asexual reproduction in which part
of the parent organism pinches off and forms a new
organism.
• Fragmentation- part of a multicelluar organism breaks
off and starts a new organism.
**the difference between budding and fragmentation is
that fragmentation can occur on accident, budding is
performed by the organism itself.
Sexual Reproduction
• Zygospore- secretion from the zygote that provides a tough
outer coating allowing the zygote to survive freezing, drying,
and UV radiation.
• Sexual Reproduction in Unicelluar Protists- a haploid cell
divides by binary fission to produce haploid cells. Two
gametes fuse to form a diploid zygote, which becomes a
zygospore.
• Sexual Reproduction in Multicellular Protists:
• Alternation of generations- within the life cycle of an
organism, the occurrence of two or more distinct forms that
differ from each other in method of reproduction.
• diploid, spore producing phase = sporophyte generation.
• haploid, gamete producing phase = gametophyte generation.
Classifying Protists
*the classification of organisms currently grouped
in the kingdom Protista is likely to change as
scientists learn more about how these organisms
are related to each other and to members of
other kingdoms.
• molecular studies suggest that protists could be
classified into up to 20 kingdoms.
• the characteristics that protists share with plants,
animals, and fungi provide information about the
evolution of these organisms.
Grouping Protists
• Grouping protists by the way they obtain
nutrients helps us understand the ecological
roles.
• Group by source of nutrition.
• 3 Groups:
1. Photosynthesis (plant-like)
2. Heterotrophic (animal-like)
3. Absorb from environment (funguslike)
Animal-like Protists
• Ingest other organisms to obtain energy.
1.
Amoeboid
–
2.
Ciliates
–
3.
Cilia – short, hair-like structures that aid in movement.
Flagellates
–
4.
Pseudopodia – extension of cell that functions in food ingestion and
movement.
Flagella – whip-like structure that aids in movement.
Sporozoans
–
–
–
Form spore-like cells when they reproduce
Do not move
Parasitic and cause disease
Plant-like Protists
• Plant-like protists obtain energy from the sun.
1. Diatoms
–
2.
Unique double shells
Euglenoids
–
Have one or two flagella
•
3.
Dinoflagellates
–
4.
Found in warm ocean waters
Grow at greater depths
Brown Algae
–
6.
Spin through the water with their two flagella
Red Algae
–
–
5.
Example: Euglena
Large Kelp
Green Algae
–
Make up most marine kelp
Funguslike Protists
• Funguslike Protists absorb nutrients from their environment
and reproduce by releasing spores.
1. Slime Molds
– Plasmodium – the multinucleate cytoplasm of a slime
mold that is surrounded by a membrane and moves as a
mass
2. Water Molds and Downy Mildews
– Decompose dead organisms
– Parasites of aquarium fish
– One type of water mold caused the 1846 potato famine
in Irelad
– One type of downy mildew almost wiped out the wine
industry in France in 1879
Protists and Disease
• Protists cause a number of human diseases,
including giardiasis, amebiasis, toxoplasmosis,
trichomoniasis, cryptosporidiosis, Chagas
disease, and malaria.
Giardiasis
•
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•
•
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Infectious agent: Giardia intestinalis
Transmission: Drinking water or recreational
water.
Symptoms: Diarrheal disease.
Fact:
– Affect 1/3 of the world’s developing population.
Amoebic Dysentery
• Infectious agent: Amoeba: Entoamoeba
histolytica (found in feces)
• Transmission: Eating cysts in contaminated
food or water; person to person contact.
• Symptoms: Fever, nausea, mild diarrhea,
vomiting. Pain in upper right portion of abs.
• Facts:
– 40, 000 – 100,000 people die annually (world).
– Most common symptom is diarrhea
Toxoplasmosis
• Infectious agent: Toxoplasma gondii.
• Transmission: eating infected meat, feces of a
cat, mother-fetus.
• Symptoms: mild flu-like illness, muscle aches, etc.
for a month or longer. Affects heart, liver, inner
ears and eyes.
• Facts:
– 1/3 of world population carries a toxoplasmic infection
– Toxoplasmosis is not harmful to healthy people,
people with immune deficiencies are at risk.
Trichomoniasis
•
•
•
•
•
Infectious agent: Trichomonas vaginalis
Transmission: STD (STI)
Symptoms: Inflammation of cervix, urethra.
Itching/burning. Discomfort during urination.
Facts:
– Most common curable STD.
– Causes pre-mature birth/low birth weight.
Cryptosporidiosis
• Infectious agent: Cryptosporidium muris (and
other Cryptosporidium)
• Transmission: contaminated water/food.
Undercooked food, cross-contaminated.
• Symptoms: stomach pain, diarrhea (2-10 of
infection)
• Facts:
– 10% of people in developing countries
– 1993 in Milwaukee 100 deaths due to this parasite
Chagas Disease
• Infectious agent: Trypanasoma cruzi
• Transmission: Triatomine bug (Kissing bug),
blood transfusions
• Symptoms: fever, swelling around bite site,
fatigue, diarrhea, vomiting.
• Facts:
– No vaccine
– Can cause rhythm abnormalities and sudden
death.
Malaria
• Infectious agent: Plasmodium falciparum
• Transmission: bite from anopholes mosquito
(female)
• Symptoms: fever, chills, headache, coma/death.
• Facts
– Children and pregnant women at higher risk
– 3.3 billion are susceptible to malaria
– Some forms will not show for 4 years after infection