Protists
Chapter 28
What you need to know!
• Protista is no longer considered an
independent kingdom. They are part of
the Eukaryotes doman and are very
diverse.
• How Chloroplasts and mitochondria
evolved through endosymbiosis
*Domain Eukarya
Kingdom Protista (includes):
• Phylum: Protozoa (euglena, amoeba,
paramecium, malaria)
• Phylum: Crysophyta (diatoms, golden
algae)
• Phylum: Pyrrophyta: (dinoflagellates)
*Metabolism
• Protists are the most nutritionally diverse of
all eukaryotes:
• Most protists are aerobic, with mitochondria
for cellular respiration.
• Some protists are photoautotrophs with
chloroplasts.
• Still others are heterotrophs that absorb
organic molecules or ingest larger food
particles.
• A few are mixotrophs, combining
photosynthesis and heterotrophic nutrition
Characteristics
• Protists are eukaryotes
• Can be unicellular, colonial, or multicellular
• Predecessor to other eukaryotes: plants,
fungi, and animals.
• Fossils date back 2.1 billion years
• Some of the most complex cell structures
found
– Special organelles: contractile organelle
(primitive excretion, H20 balance), eye spots
(primitive sight), anal pores (primitive waste
excretion)
Specifics
Types:
1.Absorptive, protists (fungus-like)
2.Protozoa - ingestive, animal-like protists
3.Algae - photosynthetic, plant-like protists.
Important Structures:
•Flagella: Protists have a flagella or cilia
during some time in their life cycles.
– The eukaryotic flagella are extensions of the
cytoplasm with a support of a microtubule
system (made from tubullin)
– Cilia are shorter and more numerous than
flagella.
Reproduction
•
•
•
1.
2.
3.
4.
5.
protists can reproduce asexually or
sexually
Many protists form resistant colonies
(cysts) that can survive harsh conditions.
Protists are the first group to show
“alternation of generation”:
Most protists are haploid organisms (n),
called gametophytes
Gametophytes produce gametes
Gametes fuse to form a zygote
The Zygote develops into a sporophyte
(not the main organisms)
The Sporophyte produces haploid spores
that germinate into gametophytes
Habitat
Protists are found almost anywhere there is
water:
• Oceans, ponds, and lakes, but also damp
soil, leaf litter, and other moist terrestrial
habitats.
• Protists are also important parts of the
plankton, communities of organisms that
drift passively or swim weakly in the
water.
• Phytoplankton (including planktonic
eukaryotic algae and prokaryotic
cyanobacteria) are the bases of most
marine and freshwater food chains.
*Lifestyle
• Many protists are symbiots that inhabit the
body fluids, tissues, or cells of hosts.
• These symbiotic relationships span the
continuum from mutualism to parasitism
(malaria, giardia)
*Evolution
• Endomembrane system of eukaryotes (nuclear envelope,
endoplasmic reticulum, Golgi apparatus, and related structures)
may have evolved from in-folding of plasma membrane.
• Mitochondria and chloroplasts were incorporated through
endosymbiosis
Euglena
• Freshwater microscopic algae,
single celled autotrophic
organism (phytoplankton)
• Contractile vacuole: bladderlike, pulsing structure that
pumps out excess water that
enters the cell due to the cell
being hyperosmotic in fresh
water
• Eyespot: detection of light
direction
• Flagellum: movement toward
light source
Amoebas
• Pseudopods: extensions
of the cytoplasm
– Capturing prey, locomotion
• Heterotrophic
• Movement by
pseudopods (false feet):
bulging out of plasma
membrane followed by
cytoplasm
Paramecium
• Coordinated movement
through ciliates
• Complex organelles:
contractile vacuole for
osmoregulation (pumping
out water), oral groove
(mouth), anal pore (duh)
Radiolarians
• Skeleton
pseudopods to
increase surface
area
Foraminiferans
• Beautifully shaped
calcium carbonate or
silica shelled protists
Malaria (protozoan)
• transmitted by infected
mosquito
Phylum Crysophyta/Diatoms
• Abundant in plankton and
sediments
• Have silica shells
• Top and bottom shells fit
together like boxes
*Well Known Members
• Infamous:
• Giardia
• Trypanosomes
• Malaria
• Cute
• Paramecium
• Amoeba
• Mistaken as other organisms
• Brown, green, and red algae
• Giant Kelp