1. Protists

2. Protists
Eukaryotic organisms that cannot be classified as fungi, plants, or animals
Many important characteristics evolved in protists
Membrane-bound organelles
Allow cells to perform a variety of functions
Complex cilia and flagella
Found in organs of other organisms (lungs)
Sexual reproduction with gametes
Allows greater genetic diversity
Multicellularity
Allows cells to be able to specialize

3. Protists Reproduction
Protists can reproduce in two ways:
Asexual reproduction
Results in offspring genetically identical to parent
Sexual reproduction
Results in offspring genetically different from parents

4. Asexual Reproduction
Binary Fission—occurs when a unicellular organism reproduces by splitting in half after copying its DNA
Similar to mitosis in multicellular organisms
Budding—occurs when part of the parent organism pinches off to form a new organism
New organism is smaller than parent organism
Can occur in unicellular & multicellular organisms
Fragmentation—similar to budding; occurs only in multicellular organisms, and happens by accident

5. Sexual Reproduction Occurs as a response to environmental stress
Unicellular organisms (called zygospores) reproduce through meiosis and release haploid cells that mature
Multicellular organisms have an alternation of generations
Diploid, spore-producing phase called sporophyte generation
Produce haploid spores by meiosis

6. Sexual Reproduction, cont.
Haploid, gamete-producing phase called gametophyte generation
Produces gametes through mitosis
Two gametes fuse to form a diploid zygote which is the first stage of the new sporophyte generation

7. Classifying Protists
Organisms classified as protists likely to change as scientists learn more about how they are related to each other and members of other kingdoms
Molecular studies provide lots of information about relationships
Characteristics shared with plants, animals, and fungi provide evolutionary information
New classification system for protists being developed

8. Groups of Protists Grouped by the way they obtain nutrition
Divided into three groups:
Plant-like (photosynthetic)
Animal-like (heterotrophic)
Fungus-like (absorb nutrients from the environment & reproduce by releasing spores)

9. Animal-Like Protists Called protozoa which means first animal
All are unicellular, most can move, and most reproduce asexually by binary fission
Four groups:
Amoeboid Protists
Ciliates
Flagellates
Sporozoans

10. Amoeboid Protists
Move using pseudopodia which are also used to surround and engulf food
Live in fresh water, salt water, and soil
Can be parasitic
Some form tests
Outer shells made from protein, calcium carbonate, silica, or mineral particles

11. Ciliates
Have a tough, flexible covering and short, hair-like structures called cilia
Move and hunt food by beating cilia
Live in fresh water and salt water
Reproduce sexually through conjugation

12. Flagellates Have whip-like structures called flagella
Can have cilia or form pseudopodia
Many free-living, but can be parasitic (Leishmania)

13. Sporozoans Do not move Parasitic and cause disease
Reproduce asexually and sexually
Form spore-like cells

14. Plant-Like Protists
Include organisms commonly called phytoplankton and algae
Vary in types of pigments used for photosynthesis and types of molecules used to store energy
Six groups:
Diatoms
Euglenoids
Dinoflagellates
Red Algae
Brown Algae
Green Algae

15. Diatoms Unicellular protists with double shells
Shells made of silica or calcium carbonate
Diploid and reproduce asexually
Get smaller each generation
At a certain size, they go through sexual reproduction to produce full-size offspring

16. Euglenoids Freshwater protists with one or two flagella
Most photosynthetic; some photosynthetic and heterotrophic; some others completely heterotrophic
Some have eyespots
Light-sensitive organs that help them move toward light

17. Dinoflagellates Unicellular protists that typically have two flagella
Most photosynthetic, but some are heterotrophic
Most have protective cellulose coats that become encrusted with silica
This gives the unusual shapes
Flagella beat in two grooves
One around organism like a belt; one perpendicular
Causes the organism to spin like a top

18. Red Algae Multicellular, found in warm ocean waters
Absorb blue light, allows them to grow at greater depths
Some have calcium carbonate in their cell walls
Play important role in the formation of coral reefs

19. Brown Algae Multicellular, found in cool ocean waters
Kelp with root-like structure (holdfast), stem-like structure (stripe), and leaf-like structures (blades)
Only algae that form more than one tissue type

20. Green Algae
Closest to plants and are believed to have given rise to the first true plants
Do not have complex tissue layers
This is why they are not classified as plants now
May be classified as plants in the future

21. Fungus-Like Protists
Once classified as fungi, but molecular information proved that to be false
Broken into two groups:
Slime Molds
Water Molds & Downy Mildews

22. Slime Molds Exist as single-celled amoebas under normal conditions
Form colonies and release spores in harsh conditions
Help researchers understand how cells interact and how cytoplasm moves within cells

23. Water Molds & Slimy Mildew
Form multicellular filaments that resemble fungi
Many decompose dead organism
Others are parasitic
Water mold responsible for the Great Potato Famine of 1846
Downy mildew responsible for the poor grape harvest in the French wine country in 1879 (almost wiped out the industry)

24. Protists & Disease
Parasitic protists cause many diseases, sometimes death, in humans
Giardiasis
Amebic Dysentery
Toxoplasmosis
Trichomoniasis
Cryptosporidiosis
Chagas Disease
Malaria

25. Giardiasis Causes severe diarrhea & intestinal cramps
Contracted by drinking contaminated water
Lasts 2-6 weeks; rarely fatal

26. Amebic Dysentery Caused by parasite Entamoeba histolytica
Amebiasis—mild form, lasts a couple weeks
Amebic dysentery—sever form; causes pain, bloody diarrhea, & fever
In rare cases, amoebas travel to liver, lungs, or brain & can be fatal
Transferred in contaminated water & raw fruits/vegetables washed in contaminated water

27. Toxoplasmosis Causes flu-like symptoms
Spread by cats & by eating undercooked meat
Healthy adults usually not affected
Can cause nerve, brain, or eye damage in rare cases
Babies of pregnant women more susceptible
Can cause nerve, brain, or eye damage in fetus
Wash hands & cook meat thoroughly

28. Trichomoniasis Most common STD; caused by Trichomonas vaginalis
Infects about 7.4 million people each year
Causes discolored urine, itching, and sometimes vaginal secretions
Not fatal; can be treated with medicine

29. Cryptosporidiosis Causes severe cramps & diarrhea
Lasts about two weeks
Spread by contaminated water/objects & uncooked food
People with weak immune systems can suffer longer

30. Chagas Disease Also called American trypanosomiasis
Occurs in South & Central America
Early stage has few or no symptoms
Chronic stage can cause heart disease, abnormal heartbeat, heart failure, heart attack, & enlargement of the esophagus & large intestines

31. Malaria Caused by sporozoans of the genus Plasmodium
Infects the liver and red blood cells
Can cause rupture of the spleen, kidney failure, coma, brain damage, & death if left untreated

32. Protists & the Environment
Plant-like protists produce oxygen & take up carbon dioxide during photosynthesis
Others help decompose dead organisms which helps to recycle nutrients
Photosynthetic protists form the base level of almost all aquatic food chains
Protists produce algal blooms that can be harmful to humans & other organisms
About 15% of species on Earth are symbiotic protists

33. Protists & Industry Used in food production
Ice cream, salad dressings, gelatin
Used for industrial & consumer products
Agar, paint, fire-fighting foam, toothpaste, makeup
Used in scientific research
Used to study ribosomes, cell aging, & cell cycle control
Used to study cell movement & signaling
Help researchers understand how white blood cells fight disease