bio 205 chapter 3: the protists

protozoans

“original animals”, unicellular, eukaryotic, heterotrophic, motile, lack cell walls

contractile vacuoles

membrane-bound sac that can store water and can expel excess water

spongiome

a system of vesicles, tubules and sacs that collect water from the cytoplasm and deliver it to a contractile vacuole; the water is discharged from the vacuole through a pore on the outer cell surface

extrusomes

structures capable of ejectability and extend outwardly from the cell surface when activated

trichocysts

discharged long, thin filaments that are used to make contact (with another protozoan or prey)

toxicysts

discharged filaments that release toxins to paralyze prey

flagella

long, whip-like tails for locomotion, comprised of microtubules, anchored by basal bodies consisting of 9 triplet microtubules

cilia

short, hair-like extensions for locomotion that move like stiff oars, composed of microtubules, anchored by basal bodies consisting of 9 triplet microtubules

9+2 microtubule arrangement

9 outer (peripheral) doublets, 2 inner (central) singlets

dynein arms

extend from one doublet to another allowing for the doublets to slide against each other

pseudopods

cytoplasmic extensions from a cell that allow for slow movement and the engulfment of food through phagocytosis

lobopodia

pseudopods that are thick, blunt and rounded at the tip

axopodia

pseudopods that are thin and needle-like

reticulopodia

pseudopods that are thin and branching

kinetodesmata

an arrangement of protein fibers connecting together the basal bodies of cilia, allows for the cilia to beat in a rhythmic pattern

mastigont systems

palm-like arrangements of flagella that arise from a common point or area of the cell

binary fission

the nucleus is copied, cell grows in size then splits evenly resulting in two genetically identical cells of equal size

alveolate protozoans

possess membrane-bound sacs below the cell surface called alveoli that regulate water and ion balance and stabilize the cell surface

alveoli

membrane-bound sacs below the cell surface that regulate water and ion balance and stabilize the cell surface

excavate protozoans

possess a groove along the cell surface along which the absorption of nutrients can occur

amoebozoan protozoans

possess pseudopods for movement and feeding through phagocytosis

phylum ciliophora

free-living ciliated protozoans
use cilia for movement and feeding
oral groove
contractile vacuoles
dimorphic nuclei
members: Paramecium, Didinium, Stentor, Vorticella

oral groove

lined with cilia and draws in food

macronucleus

a polyploid nucleus that takes care of most of the cell functioning

micronucleus

a diploid nucleus that only takes care of reproduction

autogamy

performed by a single individual, allows for a change in the genetics, typically triggered by starvation

Paramecium autogamy

1) macronucleus begins to break down
2) 2 diploid micronuclei divide meiotically to form 8 haploid daughter nuclei
3) 7 out of the 8 haploid micronuclei degenerate randomly
4) remaining micronucleus divides through meiosis to produce 2 gamete nuclei
5) gamete nuclei fuse to form zygote nucleus
6) zygote divides twice to form 4 nuclei, with 2 becoming macronuclei and the other 2 becoming micronuclei
7) micronuclei and Paramecium body split to form 2 daughter Paramecia, each with 2 micronuclei and 1 macronucleus

Paramecium conjugation

1) two genetically different Paramecia fuse
2) the diploid micronucleus in each undergoes meiosis to produce 4 haploid micronuclei in each
3) 3 randomly degenerate and the remaining haploid micronucleus divides through mitosis
4) the Paramecia then exchange haploid micronuclei and separate

Paramecium reproduction

1) micronucelar fusion occurs in each Paramecium resulting in a diploid micronucleus
2) the diploid micronucleus undergoes 3 rounds of mitosis producing 8 diploid micronuclei
3) the old macronucleus breaks down and 4 of the diploid micronuclei become new macronuclei with the other 4 remaining diploid micronuclei
4) each Paramecium undergoes 2 rounds of cytokinesis resulting in 4 identical offspring each with its own macronucleus and micronucleus

phylum dinozoa (dinoflagellata)

bi-flagellated
flagella extend from perpendicular grooves
transverse flagellum → cingulum
longitudinal flagellum → sulcus
covered by cellulose plates
carotenoid pigments
mixotrophic
members: Peridinium, Ceratium, some species cause red tides

cingulum

used for rotational movement, transverse flagellum extend from

sulcus

used for uni-directional movement in phylum dinozoa, longitudinal flagellum extend from

Peridinium

mutualistic symbiont of coral reefs, zooxanthellae relationship

zooxanthellae

the relationship between coral and certain dinoflagellates; dinoflagellates produce glucose through photosynthesis and provide that glucose to the coral

phylum apicomplexa

parasites of vertebrate animals
apicoplast
complex life cycles
major species: Plasmodium vivax → malaria

apicoplast

a non-photosynthetic plastid used for fatty acid synthesis

Plasmodium vivax life cycle

1) sporozoites are held in the salivary glands of a female Anopheles mosquito and transmitted to a human via a bite
2) the sporozoites target liver cells
3) once inside the liver cells, the sporozoites undergo multiple rounds of asexual reproduction to produce merozoites
4) merozoites are released once liver cells rupture and target the red blood cells
5) once inside red blood cells, the merozoites undergo multiple rounds of asexual reproduction and produce gametocytes
6) the gametocytes remain in the blood plasma unless picked up by another female Anopheles mosquito
7) once inside the stomach of a female Anopheles mosquito, the gametocytes become gametes
8) gametes fuse through fertilization, each zygote swells and becomes an oocyst
9) oocyst cells undergo meiosis to produce haploid sporozoites that travel to female Anopheles mosquitos salivary glands

phylum parabasala

multiple flagella
mastigont systems
heterotrophic parasites or mutualistic symbionts
undulating membrane
non-functioning mitochondria (vestigial)
example: Trichonympha

phylum euglenozoa (euglenophyta)

mixotrophic
bi-flagellated, only one flagellum emerges from the body
body covered by pellicle
pyrenoids in their chloroplasts
chlorophyll pigments
photoreceptive eyspot
example: Euglena

pellicle

a covering of interlocking protein strips that promote flexibility

pyrenoids

synthesize paramylon, a polysaccharide carbohydrate, from glucose

phylum kinetoplastida

parasitic to animals
bi-flagellated → one runs along one side of cell surface creating an undulating membrane
kinetoplast
examples: Trypanosoma, Leishmania

kinetoplast

a highly organized mass of DNA housed within a mitochondrion

phylum gymnamoeba

free-living naked and shelled amoebas
possess lobopodia
examples: Amoeba proteus, Arcella vulgaris

phylum foraminifera

amoeboid bodies housed within multi-chambered test (shell) made of CaCO3
reticulopodia extend through test pores
example: forams

phylum radiolaria

body is divided into distinct intracapsular and extracapsular zones separated by a perforated membrane
axopodia
possess a rigid skeleton composed of silica or strontium sulfate
example: radiolarians

phylum heliozoa

body is divided into distinct medulla (inner zone) and cortex (outer zone), the zones are not separated from each other by a membrane
axopodia extend from the medulla
example: Actinosphaerium

phylum choanoflagellida

choanoflagellates
closest living ancestors to animals
consist of a colony of choanocyte cells that trap food on a mucus covered collar
same cell type exists in the body of sponges