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.

• 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)

http://www.krisweb.com/krissheepscot/krisdb/html/krisweb/stream/algae.jpg

• 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

• 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.

http://www.biology.iastate.edu/Courses/201L/Prot/Chlorophyta/chlamydo40X

• 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.

http://www.kidsbiology.com/images/protist.jpg

• 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.

http://www.funsci.com/fun3_it/protisti/prot_13.jpg

• 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.

http://vigen.biochem.vt.edu/site_images/cyano1.jpg

• Evolved mutualistic relationship.• 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.

• Why mitochondria have own DNA.

http://www.life.umd.edu/labs/delwiche/Strp/Chlorophyta/charophyceae/cscu-fluor-plastids.jpg

• Secondary endosymbiosis -heterotrophic protist engulfed algae containing plastids.

• Led to diversification of plastids (including chloroplasts).

• Domain Archaea - more closely related to eukaryotes than prokaryotes.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

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

http://www.bio.mtu.edu/the_wall/phycodisc/EUGLENOPHYTA/gfx/EUGLENA.jpg

• Kinetoplastids - single large mitochondrion.

• Symbiotic; include pathogenic parasites.

• Trypanosoma - African sleeping sickness.

• Alveolata - flagellated protists (dinoflagellates), parasites (apicomplexans), ciliated protists (ciliates).

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 - 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.

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 - 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

• 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 - 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.

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.

• 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