Kingdom Protista
A very large and diverse group - comprising at least 16 phlya
A paraphyletic group - it does not contain all of the descendants
of the common ancestor of this group - some descendants are
multicellular - the fungi, plants, and animals
Many of the protists groups did not give rise to multicellular
organisms - at least 13 phyla have have remained single celled
Current classification is changing and likely to change greatly in
the near future.
Sixteen Phyla comprise the Kingdom Protista
classically grouped into 5 informal groups based on mobility and
nutrition - differs from evolutionary estimates of relatedness
Protistan Diversity
The Cell Surface
Amoebas lack a cell wall
Algae and slime molds encased in strong cell walls
Diatoms and Foraminiferans have shells of silica, calcium, debris
Locomotor Organelles
Many move by flagellar motions, or ciliary action, pseudopodial
movement - many are immobile
Nutrition
Phototrophs and Heterotrophs (phagotrophs (ingesters) and
saprobes)
Reproduction
Asexual reproduction by mitosis, fission, budding, spores
Sex by gametic meiosis, zygotic meiosis, or sporic meiosis
The Sarcodines - all can have pseudopodia
Phylum Rhizopoda - the amoebas
Phylum Actinopoda - actinopods, heliozoans
Phylum Foraminifera - forams
Phylum Rhizopoda - the amoebas
Heterotrophic
Fresh and salt water, abundant in soil, some parasitize animals
Reproduction by simple mitotic fission
No cell walls, flagella, sexual reproduction
Locomotion via pseudopodia
Pseudopodia also used for prey capture
Parasitic species may form resistant cysts
Entamoeba histolytica : Causes amoebic dysentery
Cysts resist digestion by host
Carriers exhibit no symptoms but can spread cysts
Spread through fecal contamination in food or water
may be dispersed by flies
Phylum Actinopodia - Actinopods silica (glass) skeletons covering most of cell
with many thin needlelike pseudopods that
project through pores
Phylum Foraminifera - Forams
Heterotrophic, marine organisms
Possess pore-studded shells called tests
tests: organic matter reinforced with inorganic
usually multichambered, often spiral shaped
material: often calcium carbonate, can use sand grains,
echinoderm plates, sponge spicules
Podia extrude through pores in test - used for swimming,
gathering material for test, feeding
White Cliffs of
Dover - chalk
formed from
deposited forams
Algae and other photosynthetic protists
Phylum Chlorophyta - green algae
Phylum Rhodophyta - red algae
Phylum Pheophyta - brown algae
Phylum Chrysophyta - golden algae
and diatoms
Phylum Pyrrophyta - dinoflagellates
Phylum Euglenophyta - euglenoids
Phylum Chlorophyta: Green Algae
Ancestors of all plants were multicellular green algae
green algae and plants use chlorophylls a and b, carotenoids
found in aquatic and semiterrestrial habitats
Unicellular and multicellular forms
Chlamydomonas is a
typical unicellular form
biflagellated
light sensitive eye-spot
zygotic meiosis with
zygospore resting stage
Some green algae are motile and
colonial like Volvox
Specialized reproductive cells give rise
to new colonies within the parent
colony
Has zygotic meiosis and zygospores
form within a parent colony.
Some green algae are
filamentous - like Spirogyra
named for its spiral
chloroplasts
Sex is through conjugation
of cells from + and - strains
Some green algae, like Ulva, form
multicellular sheets and have sporic
meiosis
Except for their ploidy,
the gametophytes and
sporophytes are very
similar
Phylum Rhodophyta - Red Algae
Most common coastal seaweeds - mostly multicellular, common in
warm waters
Chloroplasts have Chlorophyll a and phycobilins, like cyanobacteria
Absorb green, violet and blue light
Grow at greater depths than other algae
have sporic meiosis
Completely lack flagella
Body composed of interwoven filaments
An ancient group of eukaryotes
Economic importance
Some make sulfated polysaccharides like agar and carrageenan
Agar used as laboratory medium, a base for cosmetics, used in
baked goods and as a temporary preservative for meat and fish
Carrageenan used in paints, cosmetics and ice cream
Phylum Phaeophyta - Brown Algae
Mostly multicellular and marine
Conspicuous seaweeds, include kelps and Sargassum
Use chlorophylls a and c (like diatoms)
Photosynthetically productive - fast growing
Provide food for many animals
Some kelps grow up to 100 meters in length
Have sporic meiosis
sporophyte: large, conspicuous kelp-like form
gametophyte: small, filamentous form
separate male and female gametophytes
Phylum Chrysophyta - Diatoms and Golden Algae
Diatoms are photosynthetic, unicellular organisms
Double shells of silica - Resemble box with lid
Use chlorophylls a and c, and carotenoids
fossilize well - thick sediments of fossil
diatoms are called “diatomaceous earth”
Some move by secretions from shell
Asexual reproduction separates shell halves
each half produces new shell within old
one - become smaller with each division
Have gametic meiosis - cells are diploid
and produce sperm or eggs by meiosis
Golden Algae - use yellow and brown carotenoid pigments, and
xanthophyll accessory pigments
Unicellular, two flagella, often colonial, common in freshwater
Form resistant cysts when ponds dry out in summer
Phylum Pyrrhophyta - Dinoflagellates
Unicellular, photosynthetic, mostly marine, some bioluminescent
Distinctive flagella and coat
two flagella beat in grooves
coat composed of cellulose plates
Most use chlorophyll a & c and carotenoids
Some are symbiotic with animals
sea anemones, mollusks and corals
in corals - called “zooxanthellae”,
required for formation of coral reefs
Some forms cause “red tide”
large blooms result in red colored water
release toxins that kill fish and shellfish
consumption of poisoned fish can kill
Reproduce primarily asexually by longitudinal cell division with
nuclear mitosis - like fungi
Phylum Euglenophyta - Euglenoids
Mostly fresh water organisms
Group has characteristics of plants and animals
Some specimens are photosynthetic
use chlorophylls a and b, and carotenoids
Others lack chloroplasts and are heterotrophic
Some can transform from autotrophs to
heterotrophs and back, depending on
presence of light and food
Reproduction via nuclear mitosis and cell
division
No sexual reproduction known
Euglena is typical
Thin flexible pellicle lies within cell membrane - composed of
interlocking strips of protein
have two flagella - both
with bases in reservoir one is very small
Contractile vacuoles collect
and pump out excess
water at reservoir
have light sensitive stigma
paramylon granules are
for food storage
Heterotrophs with flagella or cilia Phylum Sarcomastigophora - Zoomastigotes
Unicellular, heterotrophic, highly variable in form
Possess one to thousands of flagella
Some free-living, some parasitic
Some reproduce asexually only
One group alternates between amoeboid and
flagellated stages
Some trypanosomes are human pathogens
cause sleeping sickness, East Coast fever,
Chagas' disease
many spread by insects, such as tsetse flies
Some inhabit guts of wood-eating insects
have enzymes capable of digesting cellulose
Choanoflagellates are similar to feeding cells of
sponges and are likely ancestors of all animals
Hiker's Diarrhea:
Caused by Giardia lamblia, found world-wide
Occurs in water, infects wild and domesticated animals, and
humans
Lives in small intestine of host
Spreads as cysts in feces, can survive for months in cool water
May appear in city water supplies
Resistant to treatment with chlorine and iodine, requires boiling
water to kill
Phylum Ciliophora - The Ciliates
Unicellular, heterotrophic, with many cilia
Coordinated beating provides motility
Outer pellicle is tough but flexible
Two types of nuclei
micronuclei - diploid - reserved for sex
macronuclei - polyploid - for normal
cellular metabolism
Specialized vacuoles ingest food and contractile
vacuoles regulate water balance
Food enters through gullet (cytostome) and
passes into vacuoles where it is digested
Asexual reproduction by transverse
fission
Sexual reproduction by conjugation
Two different mating types
exchange haploid micronuclei
Macronucleus in each individual
disintegrates
Multiple rounds of chromosomal
replications in micronuclei
reconstitutes macronucleus
Phylum Apicomplexa - Sporozoans
Nonmotile, spore-forming animal parasites
Have an “apical complex” at one end of cell - with fibrils,
microtubules, and vacuoles - used to enter host cells
Have complex life cycles with
sexual and asexual phases
Exhibit alternation of haploid and
diploid generations
Fusion of gametes produces a
thick-walled cyst, the oocyst
Meiotic divisions in oocyst
produce infective haploid
spores, sporozoites
Plasmodium causes malaria
Gametocytes
become
gametes in
gut of
mosquito
syngamy
forms zygote
and oocyst
meiosis in
oocyst forms
sporozoites
Malaria
estimated that 500 million infected, 200 million humans die
each year, most infected children die
symptoms include chills, fever, sweating, enlarged spleen,
confusion, thirst - repeating every 48 to 72 hours
Victims die of anemia, kidney failure, brain damage
Effects can be reduced with drugs
Focus is on eradication of malaria through elimination of
mosquito carriers
Vaccines against malaria may be available in near future
Slime Molds
Phylum Acrasiomycota - Cellular
Slime Molds
Phylum Myxomycota -Plasmodial
Slime Molds
Phylum Oomycota - water molds,
rusts, mildew
Phylum Acrasiomycota - Cellular Slime Molds
Once thought to be related to fungi
most closely related to amoebas
Common in fresh water, damp soil, rotting vegetation
Usually found as free
living amoebas
Sometimes cells aggregate
into motile slug
Slug transforms into
sorocarp,
within sorocarp some
amoebas fuse sexually
forming diploid
macrocysts
meiosis occurs in macrocysts - spores released form new amoebas
Phylum Myxomycota -Plasmodial Slime Molds
Consist of streaming multinucleate plasmodium
feeding phase may be yellow, orange or other color
Cytoplasm exhibits conspicuous streaming
Engulf and digest bacteria, yeast, bits of organic matter
forms sporangium under adverse conditions
Phylum Oomycota - water molds, rusts, mildew
Live in freshwater or soil, many are plant or animal parasites
Cell walls are composed of cellulose or similar polymers
Body consists of filamentous hyphae
Hyphae are diploid (unlike fungi) and produce gametes by meiosis
Exhibit normal mitosis (unlike fungi)
have unique life cycle
Diploid spores produced asexually in sporangium
Sex: female gametangium called oogonium with one to eight eggs
male gametangium called antheridium with many sperm
Fusion produces zygote that becomes thick-walled oospore
oospore germinates and forms new hypha