Kingdom PROTISTA: What are protists?
 Domain Eukarya
 Eukaryotes have a Nucleus and many organelles!
 Defined by exclusion –
Cannot be classified as plants, animals or fungi
 Diverse in body, obtaining food, and movement
How did eukaryotes evolve?
 Probably evolved 2 billion years ago
 Arose through endosymbiosis
 One organism lives inside another organism
 Photosynthetic prokaryote lived inside another
prokaryote
chloroplast
 Aerobic prokaryote lived inside another
prokaryote
mitochondrion
 cDNA and mDNA is similar to Bacteria DNA
How did eukaryotes evolve?
PROTISTA characteristics: body plans
 Most are unicellular (example, Paramecium)
 Some small multicellular colonies (example, Volvox)
 Some large multicellular colonies (example, kelp)
paramecium
volvox
kelp
PROTISTA characteristics: obtaining food
Some protists are autotrophs
 Absorb energy of sun through pigments
 Make their own food through photosynthesis
light energy + 6H20 + 6CO2
C6 H1206 + 6O2
PROTISTA characteristics: obtaining food
Other protists are heterotrophs
 Get their food by eating other organisms
 Release energy by cellular respiration
C6 H1206 + 6O2
6H20 + 6CO2 + energy(ATP)
PROTISTA characteristics: motility
 Some move with long, whip-like flagella
 Others move with shorter cilia
 Others move by extended pseudopodia
pseudopodia
flagella
cilia
PROTISTA asexual reproduction
 Most protists reproduce asexually
 Binary fission  1 cell divides into 2 equal size cells
 Multiple fission  1 cell divides into more than 2
 How do the offspring compare?
 Offspring are genetically identical to parent
 Similarity is created by the process of mitosis
PROTISTA sexual reproduction
 Some protists can reproduce sexually
 Protist conjugation  2 cells join, exchange DNA
 How do the offspring compare?
 Resulting offspring are genetically unique
 Uniqueness is created by the process of meiosis
Animal-like PROTISTA
 Move like animals
 Heterotrophic: obtain food like animals
 NOT closely evolutionarily linked to animals
Animal-like PROTISTA
Phylum Protozoa
 Body plan: unicellular
Motility: form pseudopodia
 Heterotrophic: absorb food by endocytosis
pseudopod
Animal-like PROTISTA
Phylum Protozoa
Animal-like PROTISTA
Phylum Ciliophora
cilia
 Body plan: unicellular
Motility: cilia beat in waves
 Heterotrophic: cilia sweep food into mouth
Animal-like PROTISTA
Phylum Sarcomastigophora
 Body plan: unicellular
 Motility: one or more flagella
Heterotrophic or parasitic
 Some cause disease
 Trypanosoma causes sleeping sickness
 Giardia contaminates water
Epimastigotes reproduce by
mitosis in the salivary gland and
transform → trypanosomes
Fly takes up blood and
injects trypanosomes
Trypanosomes
enter bloodstream
Trypanosomes
reproduce by mitosis in
blood and spinal fluid
Promastigotes leave the
fly gut and transform →
epimastigotes
Fly takes up blood
and trypanosomes
In fly gut, trypanosomes
transform → promastigotes
and reproduce by mitosis
Trypanosomes spread in
circulatory and nervous systems
Animal-like PROTISTA
Phylum Apicomplexa
 Body plan: unicellular
 Motility: no means of locomotion
All are parasitic
 Some cause disease
 Plasmodium causes malaria
 Cryptosporidium contaminates water
Oocysts grow, rupture,
release sporozoites
Mosquito takes up blood
and injects sporozoites
Schizonts
transform →
merozoites.
Liver cells
rupture
Sporozoites
transform →
schizonts
Ookinete invades mosquito
gut, transforms → oocyst
Mosquito takes in ♂
and ♀ gametocytes
Zygote transforms
→ ookinete
In mosquito stomach,
♂ gamete penetrates
♀ gamete → zygote
Sporozoites
invade liver cells
Asexual route:
merozoites →
schizonts →
merozoites →
blood cells rupture
Merozoites
invade
blood cells
Sexual route:
some merozoites
transform →
gametocytes
Fungus-like PROTISTA
Often called molds but NOT in Kingdom Fungi
 Protist cell walls are composed of cellulose
 Fungi cell walls are composed of chitin
Fungus-like PROTISTA
Phylum Myxomycota (plasmodial slime molds)
 Body plan: unicellular or multicellular
 Mobile and stationary life stages
Fungus-like PROTISTA
Phylum Myxomycota (plasmodial slime molds)
Mobile stage of life cycle
 Forms plasmodium: mass of cytoplasm
 Creeps by amoeboid-like streaming
 Consumes decaying plants by endocytosis
Fungus-like PROTISTA
Phylum Myxomycota (plasmodial slime molds)
Stationary stage of life cycle
 Reproduces when food is scarce
 Forms sporophores: spore-bearing structures
Fungus-like PROTISTA
Phylum Oomycota (water molds)
 Body plan: unicellular and multicellular
 Motility: flagella
Parasitize fish and many crop plants
Plant-like PROTISTA
 Autotrophic: obtain food like plants
 Lack true roots, stems, and leaves
Plant-like PROTISTA
Four basic body plans
1 unicellular
known as phytoplankton
2 colonial
coordinated group of cells
3 filamentous
slender, stringy
4 multicellular
often large and complex
Plant-like PROTISTA
Types of pigments
chlorophyll
phycobilin
fucoxanthin
carotenoid
 Chlorophyll absorbs red and blue light
 Other pigments absorb other wavelengths
√ Efficient photosynthesis
Pigments
Chlorophyll – green
Phycobilin – blue-green, yellow, and red
Fucoxanthin – brown and olive-green
Carotenoid – red, orange, and yellow
Plant-like PROTISTA
Phylum Chlorophyta (green algae)
 Diverse body forms: all four
Diverse habitats: aquatic, moist terrestrial,
symbiotic relationships
 Pigments: chlorophyll and carotenoids
 Share common ancestor with plants?
(same pigments and cell wall composition)
Plant-like PROTISTA
Phylum Phaeophyta (brown algae)
 Body form: multicellular
 Pigments: chlorophyll and fucoxanthin
 Habitat: cold, nutrient-rich, rocky coasts
Some of the largest algae known
Plant-like PROTISTA
Phylum Rhodophyta (red algae)
 Body form: multicellular
 Pigments: chlorophyll and phycobilin
 Phycobilin can absorb deep-penetrating light
Rhodophyta can live at great depths
Plant-like PROTISTA
Phylum Bacillariophyta (diatoms)
 Body form: unicellular or colonial
 Pigments: chlorophyll, carotenoids, fucoxanthin
 2-piece shells have radial or bilateral symmetry
Important role as producers in food web
Plant-like PROTISTA
Phylum Dinoflagelleta (dinoflagellates)
 Body form: unicellular
 Pigments: chlorophyll and carotenoids
Some species produce a red tide
 Turn water reddish during population explosion
 Red tide toxin can kill large numbers of fish
Plant-like PROTISTA
Phylum Chrysophyta (golden algae)
 Body form: unicellular and colonial
 Pigments: chlorophyll, carotenoids, fucoxanthin
 Resistant cysts allow survival beneath frozen lakes
in winter and dry lakes in summer
Store surplus energy as oil
Plant-like PROTISTA
Phylum Euglenophyta (euglenoids)
 Body form: unicellular
 Pigments: chlorophyll, carotenoids
Autotrophic (photosynthetic) and
heterotrophic (eyespot and flagellum)