Chapter 23: Protists Flashcards
Protists are found in a wide variety of → ____
habitats
• All require → water
• Most are free living and inhabit freshwater or marine
environments
Some act as saprophytes
obtain nutrients from dead
organic material (chemoorganoheterotrophs)
• Release degrading enzymes and absorb products
through osmotrophy
Others have holozoic nutrition, ___
which involves the
ingestion of solid nutrients through → phagocytosis
Protist morphology and physiology is the
same as ________
plants and animals
• But they are mainly unicellular,
so a lot of function occurs in
just a single cell
Plasmalemma
plasma membrane of protists
• Identical to multicellular organisms
• Ectoplasm (outer gel) and endoplasma
(inner fluid) are found under the
plasmalemma
Ectoplasm
(outer gel)
endoplasma
(inner fluid)
Pellicle
is a rigid layer beneath the plasmalemma
• Acts as a supportive layer or cuticle
Vacuoles are usually found in a
protist’s _____
cytoplasm
Contractile vacuoles
osmoregularity organelle for
freshwater protists
• Constantly expelling water
Phagocytic vacuoles
sites of food ingestion in protists that
perform phagocytosis
• Some phagocytes have a
cytosome (cell mouth) and a
cytoproct (anal pore) to aid
in the entrance and exit of
phagocytized materials
Cilia or flagella are found
on many _____ at some
point in their
→ life cycle
protists
• Allow for
→ motility
• Generate water
currents for feeding and
respiration
Trophozoites
actively growing and
reproducing protists
Encystsment
formation of a → dormant cyst
• Simple structure with a → cell wall
• Form in aquatic and parasitic protists
Cysts protect against
harmful changes in the environment
(pH, low O2, desiccation, loss of nutrients)
• Acts as sites for nuclear reorganization and cell division
• For parasitic species, a cyst is the infectious stage
Excystment
is the process where a protist escapes from
the cyst
• May be triggered by better environmental conditions
Protists have both ___ and ___ reproduction in
their life cycles
asexual ; sexual
Binary fission
is the most common method of asexual
reproduction
• Nucleus divides, then cytoplasm divides during
cytokinesis
• Two identical cells form
Sexual reproduction involves _____
gamete formation
• Gametes are called ____ in protists
gamonts
Haploid gamonts fuse in a process called → _____
syngamy
Conjugation
involves the exchange of genetic material
between two individuals
• Creates a genetically distinct nucleus
Classification of protists
was historically done
based on morphology
and locomotion into four
groups:
Flagellates, ciliates,
amoebae, and
stationary
Phylogenomics
involves the analysis of genes across
many species to determine evolutionary relationships
• Lead to the creation of → supergroups
Euglenozoa
• Primitive eukaryotes
• Free-living and parasitic flagellates
• Chemoorganotrophs or photoautotrophs
• Euglena spp.
• Elongated cell bound by plasmalemma
• Stigma – helps organism orient to → light
Stigma
helps organism orient to → light
Trypanosomes
– pathogenic Euglenozoa
• Leishmania causes → leishmaniasis
• Trypanosoma cruzi causes → Chagas’ disease
• Transmitted by “kissing bugs”
• T. brucei cause → African sleeping sickness
Metamonada
• Giardia intestinalis
• Diarrhea from contaminated water
• Members are flagellated and lack mitochondria
• Mitosomes – mitochondria-like double-bounded
membrane organelles
• Most metamonads are harmless symbionts with a few
exceptions
Mitosomes
mitochondria-like double-bounded
membrane organelle
Giardia – causes
diarrhea
• Hexamita salmonis
fish parasite
H. meleagridis
turkey pathogen
Pseudopodia
used for locomotion and
feeding
Lobopodia
rounded
Filopodia
long and narrow
Reticulopodia
netlike mesh
Naked amoebae
lack cell wall and are surrounded only
by a plasma membrane
Testate amoeba
plasma membrane is covered by →
material
Entamoebida
• Lack mitochondria but contain mitosomes
• May possess 20 mitochondrial proteins
• Parasites or commensals
• Entamoeba histolytica
• Causes amoebic → dysentery
• Third leading cause of parasitic death worldwid
Eumycetozoa “Slime Molds”
• Distinctive stage when the organisms exist as
streaming masses of colorful protoplasm
• Protoplasm creeps along in amoeboid fashion
over moist, rotting logs, leaves, and other
organic matter, which it degrades
Ciliophora
found in both benthic (sediments) and planktonic communities in water and soil systems
• Use many cilia as locomotory and feeding
(Paramecium)
• Cilia longitudinal rows or spirals around
the body
• Precisely coordinated movement
Apicomplexans
are distinguished by the apical complex at
one end of the cell
• Plasmodium genus in this group that causes → malaria
