Chapter 28 - Protists Flashcards
How far back in time do eukaryotes go?
2.7 billion years (educated guess)
- some microfossils are believed to be 1.5 billion years old
- nucleus and ER may have evolved from infoldings of membranes
Endosymbiotic Theory
“Condition of living together within”
- a relationship between 2 species in which one organism lives inside the cell or cells of another organism (the host)
Endosymbiosis Theory
- Evidence & Examples
- Mitochondria may have evolved from aerobic bacteria by a larger cell - endosymbiosis
- Chloroplasts/plastids may have evolved from photosynthetic bacteria that were engulfed - endosymbiosis/secondary endosymbiosis
- several organelles contain their own DNA
“Kingdom Protista is paraphyletic and not a kingdom at all…”
- run along side each other
* they have been lumped together for lack of knowledge of evolutionary relationships that could sort them out
By what means do protists move?
- Flagella/Cilia
- Pseudopodia (axopodia/filopodia)
- other means of propulsion
Phototrophs
- rely on light for energy
* can and do make their own nutrients
Heterotrophs
• Get their nutrients from another source
• Cannot make their nutrients
- osmotrophs ingest food in soluble form
- phagotrophs bring visible food particles into food vacuoles
Mixotrophs
Both heterotrophic and phototrophic
Protists means of reproduction
Asexual: Budding, mitosis, & schizogeny
Sexual: meiosis allows for genetic recombination
Budding
A new organism develops from an outgrowth or bud due to cell division at one particular site
Schizogony
Nucleus undergoes division preceding cell division - produces daughter cells called merozoites
Genetic Recombination
Exchange of genetic material between different organisms which leads to production of offspring with a combination of traits that differs from those found in either parent
What are the four supergroups of eukaryotes?
- Excavata
- Sar
- Archaeplastida
- Unikonta
Excavata
- Diplomonads
- Basalids
- Euglenozoans
SAR
- Diatoms
- Golden Algae
- Brown Algae
Chromalveolata • Dinoflagellates • Apicomplexans • Ciliates • Radiolarians • Forams • Cercozoans Oomycetes
- Stramenopila
- Alveolata
- Rhizaria
Archaeplastida
- Red algae
- Chlorophytes
- Charophytes
- Plants
- Green Algae
Unikonta
- Slime molds
- Tubulinids
- Entamoebas
- Gymnamoebas
- Nucleariids
- Fungi
- Choanoflagellates
- Animals
- Amoebozoans
- Opisthokonts
Basic characteristics of diplomonads
- 2 nuclei
- unicellular
- move w/multiple flagella
- modified mitochondria called mitosomes
- Giadaria intestinalis causes diarrhea; parasite found in contaminated water & can pass from human to human
Basic characteristics of parabasalids
- have undulating membranes
- move w/ flagella
- reduced mitochondria called hydrogenosomes
- Trichonympha species: lives in the gut of termites and digest cellulose
Basic characteristics of euglenoids
- Free living eukaryotes
- Pocket at one end w/one or 2 flagella
- have mitochondria
- flexible pellicle can change shape
- 1/3 of euglenoids have chloroplasts & are fully autotrophic; may become heterotrophic in the dark
- others lack chloroplasts & are heterotrophic
- reproductive by mitosis
- no known sexual reproduction
- Euglena is photosynthetic
Trichomonas vaginalis
STD in humans
- parabasalids
Basic characteristics of kinetoplastids
- 2nd major group in Euglenozoa
- refers to unique, single mitochondria in each cell
- Evade immune response w/bait and switch defense; surface proteins are changed frequently
- Trypanosomes are disease-causing kinetoplastids
African Sleeping sickness
- disease caused by kinetoplastids
* transmitted by tsetse fly
Leishmaniasis
- Caused by kinetoplastids
* transmitted from sand flies
Chagas disease
- caused by kinetoplastids
* transmitted by trypanosoma; small mammals carry the parasite
Basic characteristics of dinoflagellates
- photosynthetic unicells
- have two flagella located in grooves in the cellulose plate
- both marine & freshwater (majority in salt water)
- some are luminous
- “red tides” result from “blooms” of dinoflagellates - reproduction is crazy & can kill other animals/people if ingested
- “red tides” are detrimental to fishing industry
- they produce powerful toxin that inhibits diaphragm causing respiratory failure in vertebrates
- abundance of toxic dinoflagellates may result in death of marine mammals, fish, and birds which eat fish
- reproduce primarily by asexual reproduction (no sexual)
Basic characteristics of apicomplexans
- Spore-forming parasites of mammals
- have apical complex of organelles, vacuoles, fibrils, microtubules at one end of the cell
EX. Plasmodium causes malaria
- vector for plasmodium is the anopheles mosquito
Plasmodium Life Cycle - Step One
Mosquito bites person/animal & injects sporozoites into mammals system
Plasmodium Life Cycle - Step Two
The sporozoites travel to the liver via bloodstream
Plasmodium Life Cycle - Step Three
Sporozoites become merozoites and gametocytes
Plasmodium Life Cycle - Step Four
Liver cells burst (lyse) releasing more merozoites and gametocytes
Plasmodium Life Cycle - Step Five
Mosquito bites infected person picking up female & male gametocytes
Plasmodium Life Cycle - Step Six
Fertilization occurs in digestive tract of mosquito forming a zygote
Plasmodium Life Cycle - Step Seven
Zygotes undergo meiosis
Plasmodium Life Cycle - Step Eight
An oocyst releases a haploid sporozoites that migrate to the mosquitoes salivary glands
Basic characteristics of ciliates
- have large #’s of cilia arranged in longitudinal rows or spirals
- Some cilia May be fused into sheets, spikes, or rods that function as mouths, paddles, teeth, or feet
- has a pellicle
- Unicellular heterotrophs
- micro nucleus may only be needed for sexual reproduction
- Macro nucleus divided by mitosis & is involved w/physiological function
- vacuoles for ingesting food & maintaining water balance
- conjugation involves exchange of micro nuclei
Conjugation
Process by which one bacterium transfers genetic material to another through direct contact
Conjugation in Paramecia
- long way divided (looks like a mustache) - mitosis
- paramecium are parallel to each other & trade DNA
- 3 of 4 haploid cells disintegrate & 1 is kept - the one that stays goes through mitosis a second time
- once traded paramecia goes off
- 1 diploid micro nucleus
- this diploid goes through mitosis; making eight diploid cells - 4 macro nuclei & 4 micro
- divided until there are 4 paramecia each w 1 macro nuclei and 1 micro
4 types of stramenopila
- Brown algae
- Golden Algae
- Diatoms
- Oomycetes
Brown Algae
• most conspicuous seaweeds in northern regions (kelps)
• Thallus (the whole body) is a blade, stipe, and holdfast
• Algin: gel-forming substance used to thicken puddings, salad dressings, etc
• undergoes alterations of generations
- Sporophyte (spore planet diploid) goes through meiosis to produce spores
- Gametophyte (gamete plant) are smaller, filamentous individuals
Golden algae
- biflagellate
- freshwater or marine (plankton)
- All are photosynthetic; some mixotrophic
- Most unicellular; some colonial
- many species can form protective cysts if environmental conditions deteriorate
Diatoms
- unicellular; photosynthetic organisms
- phytoplankton
- double shells (looks like a box w/lid)
- made w/opaline silica
- live diatoms can withstand pressures as great as 1.4 mil kg/m^2 (equal to the pressure under each leg of a table supporting an elephant)
- Vibrating fibrils line grooves (raphes)
- Diatomaceous earth - filtering medium
Oomycetes
- water molds
- all are parasites or saprobes
- used to be categorized as fungi
- have motile spores (zoospores) w/2 unequal flagella
- sexual reproduction via male and female gametes
- zoospores reproduce asexually
- most live in water but terrestrial forms are plant pathogens
Phytophthora Infestans
- causes late blight of potatoes
* Irish potato famine
Saprolegnia
- fish pathogen
* can infect amphibians and kill amphibian eggs
Basic characteristics of radiolarians
- Glassy exoskeleton of silica
- bilateral or radial symmetry
- pseudopodia extend outward through small openings in the exoskeleton
- forms most of the ooze on sea floor
Basic characteristics of foraminiferans
- heterotrophic & marine protists
- many can derive nourishment from photosynthesis of symbiotic algae living within their tests
- fossils created limestone deposits (White cliffs of Dover)
- have tests (shells) of organic substances w/grains of calcium carbonate, sand, bits of echinoderm shells or, sponge spicules
- have podia (cytoplasmic projections) for gathering food and materials for their test and for swimming
Basic characteristics of cercozoans
- contains most of the amoeboid & flagellated protists that feed w/threadlike pseudopodia
- found in marine & freshwater; also in soil
- most are parasites or predators
Basic characteristics of red algae
- no centrioles, no flagella
- aka rhodophytes
- reproduce by alternation of generations
- produce pigments that give them a red color
- Porphyra is Japanese nori used to wrap sushi
Basic characteristics of green algae
• divided into two groups; charophytes & chlorophytes
• charophytes most related to land
• most chlorophytes have complex life cycles w/ both asexual and sexual reproduction
- biflagellated gametes w/cup-shaped chloroplasts
Unicellular chlorophytes
- 7000+ species mostly found in freshwater (some marine & terrestrial forms)
- chlamydomonas are simple, unicellular, resemble gametes or zoospores of more complex chlorophytes
- habitats include water (phytoplankton), damp, soil, inside eukaryotes (symbiosis), and snow
Colonial & multicellular chlorophytes
• Volvox is colonial as are filamentous forms of algae that form pond scum
• ulva forms true multicellular bodies by cell division and differentiation
- (sea lettuce) has developed alternation of generations
• Caulerpa shows repeated division of nuclei w/no cytoplasmic division so it is one big super cell
Amoeboids
- Plasmodial slime molds
- Cellular slime molds
- Tubulinids
- Entamoebas
Plasmodial Slime Molds
- multinucleate, moving mass of cytoplasm - feeding phase
- usually yellow or orange color
- feed on bacteria, yeast, & other organic material
- undergoes synchronous mitosis
- form sporangium under adverse conditions
Cellular Slime Molds
- individuals act like amoebas
- eat bacteria
- if food is scarce they aggregate to form a moving slug
Tubulinids
- used to be gymnamoebas
- large and varied group
- free living
- found in soil, freshwater, saltwater
- heterotrophs that feed on bacteria, other protists, & detritus
Entamoebas
• parasites of vertebrates & some invertebrates
• E. Histolytica causes amebic dysentery & is spread via contaminated food, water, or eating utensils
- May sometimes get to the brain and cause abscesses
Choanoflagellida
- most common ancestor of the sponges
- have single flagellum surrounded by collar of shorter filaments
- feed by straining bacteria from water w/their collar
