Objective: Chapter 28- Protists

Overview: Living Small Even a low-power microscope can reveal a great variety of organisms in a drop of pond water Protist is the informal name of the kingdom of mostly unicellular eukaryotes Advances in eukaryotic systematics have caused the classification of protists to change significantly Protists constitute a paraphyletic group, and Protista is no longer valid as a kingdom

What’s in a junk drawer? Kingdom Protista is very diverse and where scientists place eukaryotes that are not animals, plants, or fungus.

Basic Characteristics of Protists Have eukaryotic cells (has a nucleus and organelles) Most are unicellular, algae is multicellular Very diverse kingdom

Protist Complexity Protists are unicellular, so thought to be simple, but… The protist’s one cell must carry out many processes (consume food, excrete waste, reproduce, respond to stimuli), so considered to be the most complex of eukaryotic cells

Protists are grouped by how they get nutrition 1. Animal-like protists (protozoans) are heterotrophs that ingest food 2. Fungus-like protists are heterotrophs that feed on decaying organic matter 3. Plant-like protists (algae) are autotrophs that make their own food like plants

Protists, the most nutritionally diverse of all eukaryotes, include: –Photoautotrophs, which contain chloroplasts –Heterotrophs, which absorb organic molecules or ingest larger food particles –Mixotrophs, which combine photosynthesis and heterotrophic nutrition

Endosymbiosis in Eukaryotic Evolution There is now considerable evidence that much protist diversity has its origins in endosymbiosis Mitochondria evolved by endosymbiosis of an aerobic prokaryote Plastids evolved by endosymbiosis of a photosynthetic cyanobacterium

Fig Cyanobacterium Heterotrophic eukaryote Over the course of evolution, this membrane was lost. Red alga Green alga Primary endosymbiosis Secondary endosymbiosis Secondary endosymbiosis Secondary endosymbiosis Plastid Dinoflagellates Apicomplexans Stramenopiles Plastid Euglenids Chlorarachniophytes

The plastid-bearing lineage of protists evolved into red algae and green algae On several occasions during eukaryotic evolution, red and green algae underwent secondary endosymbiosis, in which they were ingested by a heterotrophic eukaryote

Fig a Green algae Amoebozoans Opisthokonts Alveolate s Stramenopiles Diplomonads Parabasalids Euglenozoans Dinoflagellates Apicomplexan s Ciliates Diatoms Golden algae Brown algae Oomycetes Excavata Chromalveolata Rhizaria Chlorarachniophytes Forams Radiolarians Archaeplastida Red algae Chlorophytes Charophyceans Land plants Unikonta Slime molds Gymnamoebas Entamoebas Nucleariids Fungi Choanoflagellates Animals

Fig h 50 µm

Fig i 20 µm

Fig j 20 µm 50 µm

Fig l 100 µm

Protozoans (Protozoa = “little animal”) 1. Heterotrophs 2. Can move like most animals Different because they are unicellular Animal-like protists, resemble animals in 2 ways

1. Protozoans With Flagella Zooflagellates: Move by flagella Reproduce asexually by binary fission Free-living in water, some are parasites

Specific Zooflagelletes 1. Trichonympha: live in the gut of termites, enzymes digest cellulose in wood 2. Trypanosoma: a parasitic zooflagellate causes African Sleeping sickness spread by tsetse fly 3. Giardia: a parasitic zooflagellate, lives in intestines, found in contaminated drinking water

2. Protozoans With Pseudopodia Protozoans that move by extending lobes of cytoplasm

Pseudopod Pseudopod: Extensions of cytoplasm Pseudopod = “false foot” v=7pR7TNzJ_pA Ex: Amoeba

3. Protozoans With Cilia Ciliates: Found free-living in freshwater envts. Short hair-like projections called cilia to move and feed

3. Protozoans With Cilia Paramecium : A ciliate with many rows of cilia for movement v=fmwN_mD7TvY

Paramecium

3. Protozoans With Cilia Some ciliates have just clusters of cilia in tufts like Stentor who uses its cilia “tuft” to capture food v=pds8w7C9FEw

4. Protozoans Lacking Motility (Apicomplexans) Spore-forming parasites (Sporozoans) No structure for movement Spore = reproductive cell

4. Protozoans Lacking Motility (Apicomplexans) Plasmodium The organism that causes malaria in humans, spread by infected mosquitoes v=JwsoK8O0lXE&list=PL0BFC0 2A301F673F3&index=3&feature =plpp_video v=RxZ7pdKqwZw&feature=bf_n ext&list=PL0BFC02A301F673F 3&lf=plpp_video v=4aVUrGO97Zg&feature=bf_n ext&list=PL0BFC02A301F673F 3&lf=plpp_video v=DPv0VstforY\

Two flagella make them spin as they move through the water Dinoflagellate blooms are the cause of toxic “red tides”

Zooxanthellae -A dinoflagellate -Photosynthetic algae, mutalistic with reef- building coral -Provide oxygen to coral

Fig µm Inside human Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) Haploid (n) Diploid (2n) Key Merozoite Apex Red blood cell

Fig µm Inside human Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) Haploid (n) Diploid (2n) Key Merozoite Apex Red blood cell Zygote (2n) FERTILIZATION Gametes Inside mosquito

Fig µm Inside human Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) Haploid (n) Diploid (2n) Key Merozoite Apex Red blood cell Zygote (2n) FERTILIZATION Gametes Inside mosquito MEIOSIS Oocyst Sporozoites (n)

Fungus-like protists: Live in damp environments and help break down organic matter (decomposers)

Plasmodial Slime Molds Mass of cyoplasm, no individual cells Found on decomposing matter v=GScyw3ammmk

Cellular Slime Molds Moves as a mass of independent cells

Algae Algae: Plant-like protists that perform photosynthesis and live in water

Unicelllar Algae (single-celled) Euglenoids (Euglena): Algae with a flagella Can do photosynthesis with light and w/out can be heterotrophs

Unicellular Algae Dinoflagellates Algae with 2 flagella that spin the cells through water (salt water) Ex: fire algae causes red tides that produces a toxin Some are bioluminescent, glow when disturbed

Diatoms No cilia or flagella Have glass like cell walls containing silica Create Diatamaceous Earth

Diatoms are a major component of phytoplankton and are highly diverse Fossilized diatom walls compose much of the sediments known as diatomaceous earth

Zooxanthellae Plant-like single celled algae in coral Provides coral (animal) with food and oxygen Coral provides habitat and CO2 for photosynthesis

Multicellular Algae (many cells)

Green Algae Grows in ponds, moist soil, fish tanks Ancestor of modern plant

Brown Algae Most common seaweed Include Giant Kelp, important habitat, area of fish spawning

Red algae Found in warmer water B/c of red pigment can photosynthesize at deeper depths

Golden Algae Golden algae are named for their color, which results from their yellow and brown carotenoids All golden algae are photosynthetic, and some are also heterotrophic Most are unicellular, but some are colonial

Giant seaweeds called kelps live in deep parts of the ocean The algal body is plantlike but lacks true roots, stems, and leaves and is called a thallus The rootlike holdfast anchors the stemlike stipe, which in turn supports the leaflike blades

Fig Blade Stipe Holdfast

Alternation of Generations A variety of life cycles have evolved among the multicellular algae The most complex life cycles include an alternation of generations, the alternation of multicellular haploid and diploid forms

Fig cm Haploid (n) Diploid (2n) Key Sporangia Sporophyte (2n) Zoospore MEIOSIS Female Gametophytes (n) Egg Male Sperm

Fig cm Haploid (n) Diploid (2n) Key Sporangia Sporophyte (2n) Zoospore MEIOSIS Female Gametophytes (n) Egg Male Sperm FERTILIZATION Zygote (2n) Developing sporophyte Mature female gemetophyte (n)

Fig. 28-UN6