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Protists
• Protists – eukaryotes; more complex than prokaryotes.
• 1st – unicellular - called protists – in 1 big kingdom (Protista)
• Protista - unicellular eukaryotes that are not plants, fungi, or animals.
• Some heterotrophs, some autotrophs, some both.
• Euglena use light (if available) to produce food or find food themselves (if no light)
• Protists divided into 3 categories. • 1Protozoa- ingestive, animal-like.• 2Fungus-like protists. • 3Algae -- photosynthetic, plant-like
protists.• Movement - flagella, cilia (some
point in life cycle)
• Both move cell with rhythmic power strokes, like oars of boat.
• Reproduction and life cycles highly varied among protists.
• Asexual - can shuffle genes through syngamy (union of 2 gametes)
• Primarily asexual; can reproduce sexually occasionally.
• Many form resistant cells (cysts) - can survive harsh conditions.
• Protists found where water is (oceans, ponds, lakes); also damp soil, leaf litter, moist terrestrial habitats.
• Protists - part of plankton, communities of organisms that drift passively or swim weakly in water.
• Many protists symbionts - inhabit body fluids, tissues, or cells of hosts.
• Relationships could be mutualistic or parasitic.
http://www.hse.k12.in.us/staff/ethomas/HONORS%20FOLDER/HONORS%20BIO%20SECOND%20SEMESTER%20PPTS/CHAPTER%2040_files/slide0008_image010.jpg
Origin
• Prokaryote - limited amount of metabolic activity.
• Evolution of multicellular prokaryotes - cells specialized for different functions.
• Groups formed that had specialty or compartments for each activity (evolution of eukaryotes)
• Plasma membrane infolded, creating organelle membranes in eukaryotes.
• Chloroplasts, mitochondria evolved from endosymbiotic relationships (Endosymbiotic theory)
• Ancestors of mitochondria - aerobic heterotrophic prokaryotes.
• Ancestors of chloroplasts - photosynthetic prokaryotes.
• Evolved mutualistic relationship.• Became more interdependent. • Close similarity between bacteria
and chloroplasts + mitochondria of eukaryotes.
• Mitosis/meiosis - result of evolution.
• Mitosis - could reproduce large genomes in eukaryotic nucleus.
• Meiosis - essential process in eukaryotic sex.
• Mitochondria, plastids contain DNA - not genetically self-sufficient.
• Why mitochondria have own DNA.
• Secondary endosymbiosis -heterotrophic protist engulfed algae containing plastids.
• Led to diversification of plastids (including chloroplasts).
Flagellates Group
• Diplomonads: multiple flagella, 2 separate nuclei (double celled), no mitochondria or plastids.
• Includes Giardia.
• Euglenoids - anterior pocket from which 1 or 2 flagella emerge.
• Most autotrophic; can be heterotrophic or mixotrophic.
• Example - Euglena
• Kinetoplastids - single large mitochondrion.
• Symbiotic; include pathogenic parasites.
• Trypanosoma - African sleeping sickness.
• Alveolata - flagellated protists (dinoflagellates), parasites (apicomplexans), ciliated protists (ciliates).
• Example – dinoflagellates - big components of phytoplankton.
• Each dinoflagellate species has characteristic shape, reinforced by internal plates of cellulose - hard-shelled.
• Red tides caused by dinoflagellates in bloom.
• Color comes from pigment they produce.
• Produce toxins deadly to predators and humans.
• 1 species - carnivorous; produces toxin to stun fish, then eats flesh.
• Some dinoflagellates form mutualistic symbioses with cnidarians, animals that build coral reefs.
• Some are bioluminescent.
5Apicomplexans
• Apicomplexans - parasites of animals; some cause serious human diseases.
• Spores - infectious.• Plasmodium - protist that causes
malaria; spends part of life cycle in mosquitoes, part in humans.
6Ciliates
• Named for use of cilia to move and feed.
• Most ciliates live as solitary cells in freshwater.
• Ciliates - 2 types of nuclei, large macronucleus, several tiny micronuclei.
• Paramecium - cilia along oral groove draw in food engulfed by phagocytosis.
• Paramecium expels accumulated water from contractile vacuole.
• Ciliates reproduce via conjugation -micronuclei that have gone through meiosis exchange genetic information.
7Stramenopila
• Includes heterotrophic and photosynthetic protists; presence of numerous fine, hairlike projections on flagella.
• Heterotrophic stramenopiles – oomycotes - water molds, white rusts, downy mildews.
• Water molds important decomposers, mainly in fresh water.
• Form cottony masses on dead fish.• Some water molds parasitic, growing
on skin, gills of injured fish.• White rusts and downy mildews
parasites of terrestrial plants.
8Heterokont algae
• Diatoms (Bacillariophyta) - glasslike walls composed of hydrated silica embedded in organic matrix.
• Reproduce mostly asexually; form cysts during certain parts of year.
• Golden algae named for pigments (yellow and brown carotene and xanthophyll)
• Some mixotrophic; can form cysts that will last decades.
• Brown algae - largest and most complex algae.
• Most multicellular, unlike other members of group.
• Brown or olive color - accessory pigments in plastids.
• Found in temperate waters.
9Seaweed
• Largest marine algae - brown, red, and green algae - seaweeds.
• Inhabit intertidal and subtidal zones of coastal waters.
• Body of seaweed – thallus - consists of rootlike holdfast + stemlike stipe - supports leaflike photosynthetic blades.
• Multicellular brown, red, and green algae show complex life cycles with alternation of multicellular haploid and multicellular diploid forms.
• Diploid individual (sporophyte) produces haploid spores (zoospores) by meiosis.
• Haploid individual (gametophyte)produces gametes by mitosis that fuse to form diploid zygote.
10Rhodophyta
• Red algae - no flagellated stages in life cycle.
• Red coloration visible due to accessory pigment.
• Red algae (Rhodophyta) - most common seaweeds in warm coastal waters of tropical oceans.
• Some species that live down deep have special pigments - allow them to absorb blue and green wavelengths (only ones that penetrate bottom).
• Most red algae multicellular - some reaching size large enough to be “seaweeds.”
• Life cycles of red algae especially diverse.
• In absence of flagella, fertilization depends entirely on water currents to bring gametes together.
11Chlorophyta
• Green algae (chlorophytes) named for grass-green chloroplasts - similar to plants.
• Most of the species chlorophytes live in freshwater.
• Most green algae have both sexual and asexual reproductive stages.
• 3 groups of protists use pseudopodia, cellular extensions, to move and feed.
• Most heterotrophic; some parasitic.
• Rhizopods (amoebas) - unicellular - use pseudopodia to move and feed.
• Amoeba extends pseudopod, anchors tip, streams more cytoplasm into pseudopodium.
• Pseudopodia activity not random - directed toward food.
• Amoebas inhabit freshwater and marine environments.
• Most free-living heterotrophs.• Some important parasites,
including dysentery in humans.
• Most heliozoans (“sun animals”) live in fresh water.
• Skeletons made of glass.• Foraminiferans, (forams) almost
all marine.• Shells have pores in them.• Pseudopodia extend through
pores for swimming, shell formation, feeding.
12Mycetozoa
• Mycetozoa (slime molds or “fungus animals”) neither fungi nor animals - protists.
• Slime molds feed and move via pseudopodia but comparisons of protein sequences place slime molds close to fungi and animals, not amoeba.
http://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Lycogala.epidendrum.2009.jpg/300px-Lycogala.epidendrum.2009.jpg
• Cellular slime molds (Dictyostelida) straddle line between individuality and multicellularity.
• Feeding stage consists of solitary cells.
• When food scarce, cells form aggregate (“slug”) - functions as unit.
• Dominant stage - haploid stage.