Transcript Eukaryotic Diversity Chapter 28 Protists

Eukaryotic Diversity
Chapter 28
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.
• Protists diverse; few
characteristics that all have in
common.
• Some heterotrophs, some
autotrophs, some both.
• Euglena use light (if available) to
produce food or find food
themselves (if no light)
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Protists divided into 3 categories.
1Protozoa- ingestive, animal-like.
2Absorptive, fungus-like protists.
3Algae -- photosynthetic, plant-like
protists.
• Most move with flagella, cilia at
some time in life cycle.
• Flagella - extensions of cytoplasm.
http://www.krisweb.com/krissheepscot/krisdb/html/krisweb/stream/algae.jpg
• Cilia shorter, more numerous than
flagella.
• Both move cell with rhythmic power
strokes, like oars of boat.
• Reproduction and life cycles highly
varied among protists.
http://sja.ednet.ns.ca/fixed%20protista%20worksheet_files/image006.gif
• Some reproduce asexual; can
shuffle genes through syngamy
(union of 2 gametes.
• Others primarily asexual; can
reproduce sexually occasionally.
• Many protists form resistant cells
(cysts) - can survive harsh
conditions.
http://www.biology.iastate.edu/Courses/201L/Prot/Chlorophyta/chlamydo40X
• Protists found wherever there is
water (oceans, ponds, lakes); also
damp soil, leaf litter, moist
terrestrial habitats.
• Protists - important parts of
plankton, communities of organisms
that drift passively or swim weakly
in water.
http://www.kidsbiology.com/images/protist.jpg
• Many protists symbionts that
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
• Evolution of eukaryotic cell led to
development of unique cellular
structures and processes.
• Smallness of prokaryote limited
amount of metabolic activity.
• Evolution of multicellular
prokaryotes - cells specialized for
different functions.
http://www.funsci.com/fun3_it/protisti/prot_13.jpg
• Some form groups that had
specialty or have compartments for
each activity (evolution of
eukaryotes)
• Plasma membrane infolded, creating
organelle membranes in eukaryotes.
• Chloroplasts, mitochondria evolved
from endosymbiotic relationships.
• Serial endosymbiosis - mitochondria
and chloroplasts - small prokaryotes
living within larger cells.
• Ancestors of mitochondria aerobic heterotrophic prokaryotes.
• Ancestors of chloroplasts photosynthetic prokaryotes.
http://vigen.biochem.vt.edu/site_images/cyano1.jpg
• Evolved a mutualistic relationship.
• Over time - became more
interdependent.
• Close similarity between bacteria
and chloroplasts + mitochondria of
eukaryotes.
http://io.uwinnipeg.ca/~simmons/1116/images/bactloco.gif
• Mitosis/meiosis - result of
evolution.
• Mitosis - could reproduce large
genomes in eukaryotic nucleus.
• Meiosis - essential process in
eukaryotic sex.
http://img.search.com/d/db/Mitosis-flourescent.jpg
• Mitochondria, plastids contain DNA
- not genetically self-sufficient.
• Some protein encoded by
organelles’ DNA.
• Some of genome got transferred as
relationship went from parasitic to
interdependent.
http://www.life.umd.edu/labs/delwiche/Strp/Chlorophyta/charophyceae/cscu-fluorplastids.jpg
• Plastids diversified because of
endosymbiotic relationships.
• Secondary endosymbiosis heterotrophic protist engulfed
algae containing plastids.
• Led to diversification of plastids
(including chloroplasts).
• Domain archaea - more closely
related to eukaryotes than
prokaryotes.
• Modern archaea have genes of
bacterial origin.
• 3 domains arose from ancestral
community of primitive cells that
swapped DNA.
• Every diversification allowed for
future ones.
• Range from very simple to very
complex.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
1Flagellates
• Diplomonads have multiple flagella,
2 separate nuclei, simple
cytoskeleton, no mitochondria or
plastids.
• Parabasalids include trichomonads.
• Spread through sexual contact.
2Euglenoids
• Euglenoids (Euglenophyta) characterized by anterior pocket
from which 1 or 2 flagella emerge.
• Most autotrophic; can be
heterotrophic or mixotrophic.
http://www.bio.mtu.edu/the_wall/phycodisc/EUGLENOPHYTA/gfx/EUGLENA.jpg
3Kinetoplastids
• Kinetoplastids (Kinetoplastida) have
single large mitochondrion
associated with unique organelle
(kinetoplast)
• Kinetoplastids symbiotic, include
pathogenic parasites.
• Trypanosoma causes African
sleeping sickness.
4Alveolata
• Alveolata - flagellated protists
(dinoflagellates), parasites
(apicomplexans), ciliated protists
(ciliates).
• Members have aveoli, small
membrane-bound cavities, under
cell surface.
http://biology.unm.edu/ccouncil/Biology_203/Images/Protists/Trichonympha1.jpg
• Example – dinoflagellates - big
components of phytoplankton.
• Each dinoflagellate species has
characteristic shape, reinforced by
internal plates of cellulose - hardshelled.
• 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.
http://www.niwa.co.nz/pubs/wa/13-2/images/bloom1_large.jpg
• Some dinoflagellates form
mutualistic symbioses with
cnidarians, animals that build coral
reefs.
• Some are bioluminescent.
http://www.elenas-vieques.com/stars/pbbburst.jpg
5Apicomplexans
• Apicomplexans - parasites of
animals; some cause serious human
diseases.
• Spores (sporozoites) - infectious.
• Plasmodium - protist that causes
malaria; spends part of life cycle in
mosquitoes, part in humans.
http://plantphys.info/organismal/lechtml/images/merozoite.jpg
6Ciliates
• Ciliophora (ciliates) 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.
http://alpha1.fmarion.edu/~bio106lab/Resources/dinoflag.jpg
• 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 (Phaeophyta) - largest
and most complex algae.
• Most multicellular, unlike other
members of group.
• Brown or olive color - accessory
pigments in plastids.
• Found in temperate waters.
http://www.coralreefnetwork.com/marlife/stepath/images/Chnoospora_implexa.jpg
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.
http://www.deeknow.com/images/200603-Nelson/Mapua/Seaweed.jpg
• Some brown algae have floats to
raise blades toward surface.
• Algae - many uses including
thickener for foods.
• Seaweed popular food item in Asian
countries.
• Multicellular brown, red, and green
algae show complex life cycles with
alternation of multicellular haploid
and multicellular diploid forms.
• Evolved convergent in life cycle of
plants.
http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/brightfield/images/polysiphonia.jpg
• 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 phycoerythrin.
• Red algae (Rhodophyta) - most
common seaweeds in warm coastal
waters of tropical oceans.
http://www.sonoma.edu/users/c/cannon/Bio314AlgaeInvertsVertsImages/Rhodophyta_Rhodymenia.JPG
• 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.
http://www.botany.hawaii.edu/faculty/webb/BOT311/Rhodophyta/PorphyraLifeCycle-3-300Lab.jpg
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.
http://www.microscopy-uk.org.uk/micropolitan/marine/algae/Polysiphonia_nigrescens450.jpg
• 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.
http://www.sanger.ac.uk/Info/Press/gfx/050223_E_histolytica_300.jpg
• 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
• Plasmodial slime molds
(Myxogastrida) brightly pigmented,
heterotrophic organisms.
• 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.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings