1. Protists

2. What is a Protist? A protist is any organism that is not a plant, an animal, a fungus, or a prokaryote.  The 1 st eukaryotic organisms on Earth, appearing nearly 1.5 billion years ago, were protists.  Protists are a diverse group that may include more than 200,000 species.  Most protists are unicellular, aquatic organisms, including both freshwater and marine species.  Protists can reproduce sexually or asexually, depending on the species.

4. A Sample of Protistan Diversity Most protists are classified by their method of obtaining nutrients:  Animal-like protists  are heterotrophs – absorb or ingest food  Plant-like protists  Photosynthesize – contain chloroplasts for photosynthesis  Fungus-like protists  are parasites or decomposers

5. The 4 phyla of animal-like protists (called PROTOZOA) are distinguished from one another by their means of movement: 1. Zooflagellates swim with flagella 2. Sarcodines move by extensions of cytoplasm 3. Ciliates move by means of cilia 4. Sporozoans do not move on their own The Protozoans: Animal-Like Protists

6. Zooflagellates Animal-like protists that swim using flagella are referred to as zooflagellates.  Most have either 1 or 2 flagella (although some species have many).  Absorb food through their cell membranes  Most live in lakes and streams, although some live in the bodies of other organisms  Most reproduce asexually by means of binary fission, although some have a sexual life cycle

7. Sarcodines Sarcodines are animal- like protists that use pseudopods for feeding and movement.  Pseudopods (false feet) are temporary projections of cytoplasm.  The best known sarcodines are amoebas.  Amoeboid movement involves the cytoplasm of the cell streaming into the pseudopod allowing the rest of the cell to follow.

8. Ciliates Animal-like protists that move and feed by means of cilia are known as ciliates.  Cilia are hair-like projections similar to flagella. Most ciliates are free living (non parasitic). Some of the best known ciliates belong to the genus Paramecium.

9. Sporozoans Members of the group Sporozoa are animal-like protists that do not move on their own and are parasitic.  The sporozoan Plasmodium, which causes malaria, is carried by the female Anapheles mosquito.  As many as 2 million people die from malaria each year.  Other diseases caused by animal-like protists include:  African Sleeping Sickness – trypanosoma parasite is transmitted by tsetse fly.  Giardia - diarrheal illness caused by a microscopic parasite, Giardia intestinalis – a sporozoan.

10. Figure 28.11 Inside mosquitoInside human Sporozoites (n) Oocyst MEIOSIS Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) FERTILIZATION Gametes Zygote (2n) Key Haploid (n) Diploid (2n) Merozoite Red blood cell Apex 0.5 µm Life Cycle of Plasmodium An infected Anopheles mosquito bites a person, injecting Plasmodium sporozoites in its saliva. 1 The sporozoites enter the person’s liver cells. After several days, the sporozoites undergo multiple divisions and become merozoites, which use their apical complex to penetrate red blood cells (see TEM below). 2 The merozoites divide asexually inside the red blood cells. At intervals of 48 or 72 hours (depending on the species), large numbers of merozoites break out of the blood cells, causing periodic chills and fever. Some of the merozoites infect new red blood cells. 3 Some merozoites form gametocytes. 4 Another Anopheles mosquito bites the infected person and picks up Plasmodium gametocytes along with blood. 5 Gametes form from gametocytes. Fertilization occurs in the mosquito’s digestive tract, and a zygote forms. The zygote is the only diploid stage in the life cycle. 6 An oocyst develops from the zygote in the wall of the mosquito’s gut. The oocyst releases thousands of sporozoites, which migrate to the mosquito’s salivary gland. 7

11. Ecology of Animal Like Protists Not so Good: Can be parasitic/cause disease  Malaria, African Sleeping Sickness, Cryptosporidium Good: Symbiosis  Termites have beneficial animal-like protists called Trichonympha in their stomachs  Break down cellulose in wood so termites can use it as food

12. Main Characteristic: Chlorophyll  Green pigment that traps light, carries out photosynthesis  Evolved from symbiosis of photosynthetic bacteria and larger, heterotrophic bacteria Plant-like protists are commonly called “Algae” Can contain cell wall like plants Unicellular (4 types)  Euglenophytes, Dinoflagellates, Chrysophytes, Diatoms Multi-cellular (3 types)  Red Algae, Brown Algae, Green Algae Plant-Like Protists

13. The 4 phyla of plant-like protists that are grouped together as unicellular algae are: 1. Euglenophytes 2. Dinoflagellates 3. Chrysophytes 4. Bacillariophytes Unicellular Algae

14. Euglenophytes

15. Algal Blooms

16. Dinoflagellates Dinoflagellates are plant-like organisms that can be photosynthetic or heterotrophic.  Abundant components of both marine and freshwater phytoplankton  Many species are luminescent.

17. Red Tides Great blooms of the dinoflagellates have occurred in recent years on the east coast.  These blooms are known as “red tides”.  These species release a potentially harmful toxin that infect certain shellfish.  Eating these infected shellfish can be harmful or fatal.

18. Dinoflagellates & Bioluminescence

19. Chrysophytes Members of the phylum Chrysophyta are a diverse group of plantlike protists that have gold-colored chloroplasts.  includes yellow-green algae and golden-brown algae  reproduction can be sexual or asexual

20. Diatoms Diatoms are plant-like protists that produce thin, delicate cell walls rich in silicon (the main ingredient in glass).  Diatoms are among the most abundant organisms on Earth!  Diatoms are beautiful!

21. Ecology of Plant-Like Protists Most unicellular species beneficial Act as producers in the marine food chain  Form Phytoplankton for consumer organisms to eat  Approx. ½ of the photosynthesis on earth!!!  Produce large amount of oxygen Symbiosis: Coral Reefs, Clams  Provide food via photosynthesis, receive a home

22. The 3 phyla of algae that are largely multicellular are commonly known as:  red algae  brown algae  green algae  A major difference among these phyla are their photosynthetic pigments. Multicellular Algae

23. Red Algae (a) Bonnemaisonia hamifera. This red alga has a filamentous form. Dulse (Palmaria palmata). This edible species has a “leafy” form. (b) A coralline alga. The cell walls of coralline algae are hardened by calcium carbonate. Some coralline algae are members of the biological communities around coral reefs. (c)

24. Brown Algae Giant kelp

25. Green Algae Chlamhydomonas unicellular green algae Volvox colonial green algae Ulva multicellular green algae Spirogyra Multicellular green algae

26. Food for humans Food for invertebrates and fishes in mariculture Animal feed Soil fertilizers and conditioners in agriculture Treatment of waste water Diatomaceous earth (= diatoms) Chalk deposits Phycocolloids (agar, carrageenan from red algae; alginates from brown algae) Drugs Model system for research Phycobiliproteins for fluorescence microscopy Beneficial Aspects of Algae

27. Blooms of freshwater algae Red tides and marine blooms Toxins accumulated in food chains Damage to cave paintings, frescoes, and other works of art Fouling of ships and other submerged surfaces Fouling of the shells of commercially important bivalves Detrimental Aspects of Algae

28. Fungus-Like Protists Fungus-like protists are heterotrophs that absorb nutrients from dead or decaying organic matter.  Unlike true fungi, however, funguslike protists have centrioles and lack chitin in their cell wall. The fungus-like protists include:  Cellular slime molds  Acellular slime molds  Water molds

29. Slime Molds Slime molds are fungus-like protists that play key roles in recycling organic material.  They are found in damp places that are rich in organic matter, such as forest floors. The 2 groups of slime molds are:  Cellular slime molds: individual cells remain distinct – BUT – when food becomes scarce, cells join with others to reproduce in a multicellular unit with a distinct cell membrane  Acellular (Plasmodial) slime molds: cells fuse to form larger cells called plasmodium during some life cycle phases – this is the feeding stage of the organism

30. CELLULAR SLIME MOLDS

31. ACELLULAR SLIME MOLDS

32. Cellular v/s Acellular Slime Molds What is the difference between the large slug- like colony formed by cellular slime molds and the plamodium formed by acellular slime molds?  The slug-like colony is a mass of cells that is multicellular (made up of many individual cells) EACH WITH A DISTINCT CELL MEMBRANE.  The plamodium is a mass of cytoplasm that contains many nuclei but NO CELL WALLS OR MEMBRANES

33. Oomycetes (Water Molds and Their Relatives) Oomycetes  Include water molds, white rusts, and downy mildews  Were once considered fungi based on morphological studies Most oomycetes  Are decomposers or parasites  Have filaments (hyphae) that facilitate nutrient uptake

34. Ecology of Fungus-Like Protists The ecological impact of oomycetes can be significant  Phytophthora infestans causes late blight of potatoes – Irish Potato Famine  Overgrowth of water mold caused by wet and cool conditions Slime molds and water molds are the MOST important recyclers of organic material Why is the earth not littered with dead organisms?  Tissues broken down by Fungi Like Protists and other decomposers