Kingdom Protista Protists. 50 m Even a low-power microscope – Can reveal an astonishing menagerie...
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Transcript of Kingdom Protista Protists. 50 m Even a low-power microscope – Can reveal an astonishing menagerie...
Kingdom Protista
Protists
50 m
Even a low-power microscope
–Can reveal an astonishing menagerie of organisms in a drop of pond water
•Protists are more diverse than all other eukaryotes
–And are no longer classified in a single kingdom
•Most protists are unicellular
–And some are colonial or multi-cellular
Protist Diversity
Protist Diversity
• Organisms that range in size from single cells to complex structures more than 100 meters long.
• They show a variety of reproductive and nutritional strategies.
Protist Diversity
•Protists, the most nutritionally diverse of all eukaryotes, include
–Photoautotrophs, which contain chloroplasts
–Heterotrophs, which absorb organic molecules or ingest larger food particles
–Mixotrophs, which combine photosynthesis and heterotrophic nutrition
100 m
100 m
4 cm
500 m
The freshwater ciliate Stentor, a unicellular protozoan (LM)
Ceratium tripos, a unicellular marine dinoflagellate (LM)
Delesseria sanguinea, a multicellular marine red alga
Spirogyra, a filamentous freshwater green alga (inset LM)
(a)
(b)
(c)
(d)
Protists are also diverse in habitat
•Including freshwater and marine species
•There is now considerable evidence
–That much of protist diversity has its origins in endosymbiosis
ProtistA Evolution
•The plastid-bearing lineage of protists
–Evolved into red algae and green algae
•On several occasions during eukaryotic evolution
–Red algae and green algae underwent secondary endosymbiosis, in which they themselves were ingested
ProtistA Evolution
Cyanobacterium
Heterotrophiceukaryote
Primaryendosymbiosis
Red algae
Green algae
Secondaryendosymbiosis
Secondaryendosymbiosis
Plastid
Dinoflagellates
Apicomplexans
Ciliates
Stramenopiles
Euglenids
Chlorarachniophytes
Plastid
Alv
eola
tes
2˚ Endosymbiosis
•Have modified mitochondria
–Are adapted to anaerobic environments
–Lack plastids
–Have mitochondria that lack DNA, an electron transport chain, or citric-acid cycle enzymes
•A tentative phylogeny of eukaryotes
–Divides eukaryotes into many clades
Diplomonadida and parabasala
Diplomonads
–Have two nuclei and multiple flagella
5 µm(a) Giardia intestinalis, a diplomonad (colorized SEM)
ZooflagellatesZooflagellates
· Move by flagella
· They may enter into symbiotic relationships with other organisms.
Parabasalids-include trichomonads
–Which move by means of flagella and an undulating part of the plasma membrane
Euglenozoa
•Have flagella with a unique internal structure
•Euglenozoa is a diverse clade that includes
–Predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites
•2 Types
–Kinetoplastids & Euglenids
Euglenozoa•The main feature that distinguishes protists in this clade
–Is the presence of a spiral or crystalline rod of unknown function inside their flagella
Flagella0.2 µm
Crystalline rod
Ring of microtubules
Kinetoplastids–Have a single, large mitochondrion that contains an organized mass of DNA called a kinetoplast
–Include free-living consumers of bacteria in freshwater, marine, and moist terrestrial ecosystems
Trypanosoma
9 m
–Causes sleeping sickness in humans
Tsetse fly
Euglenids
Figure 28.8
Long flagellum
Short flagellum
Nucleus
Plasma membrane
Paramylon granule
Chloroplast
Contractile vacuole
Light detector: swelling near thebase of the long flagellum; detectslight that is not blocked by theeyespot; as a result, Euglena movestoward light of appropriateintensity, an important adaptationthat enhances photosynthesis
Eyespot: pigmentedorganelle that functions
as a light shield, allowinglight from only a certain
direction to strike thelight detector
Pellicle: protein bands beneaththe plasma membrane that
provide strength and flexibility(Euglena lacks a cell wall)
Euglena (LM)5 µm
EuglenidsEuglenids
EuglenidsEuglenids
Only one third of the species of Euglenoids are photosynthetic.
· Euglena stores glucose in a polymer called Paramylon
·
An eyespot with a photoreceptor is capable of detecting the presence of light.·
Reproduction is asexual.
Alveolates
Members of the clade Alveolata
–Have membrane-bounded sacs (alveoli) just under the plasma membrane
FlagellumAlveoli0.2 µm
Includes:
•Dinoflagellates
•Apicomplexans
•Ciliates
Dinoflagellates–Are a diverse group of aquatic photoautotrophs and heterotrophs
–Are abundant components of both marine and freshwater phytoplankton
•Shape is reinforced by internal plates of cellulose
•Two flagella
–Make them spin as they
–move through the water
DinoflagellatesDinoflagellatesSome species are responsible for red tides that kill fish and shellfish
Toxins released can kill aquatic & terrestrial animals (aerosols)
Apicomplexans–Are parasites of animals and some cause serious human diseases
–Are so named because one end, the apex, contains a complex of organelles specialized for penetrating host cells and tissues
–Have a non-photosynthetic plastid, the apicoplast
ApicomplexansMost apicomplexans have intricate life cycles
–With both sexual and asexual stages that often require two or more different host species for completion
–Plasmodium causes malaria
PlasmodiumAnopheles mosquito
SporozoansSporozoans
• Parasitic
• Complicated life cycle that usually involves the formation of infective spores.
e.g. malaria - The parasite is injected into
a human by a mosquito. The parasite then invades red blood cells and ruptures them.
Ciliates–Are named for their use of cilia to move and feed
–Have large macronuclei and small micronuclei•The micronuclei
–Function during conjugation, a sexual process that produces genetic variation
•Conjugation is separate from reproduction
–Which generally occurs by binary fission
CiliatesCiliates• Example - Paramecium• The outer covering of paramecium is
covered with hundreds of cilia
• They have numerous organelles including a gullet (oral groove) and an anal pore
• The macronucleus controls the cell's activities.
• The micronucleus is involved in cell reproduction (sexual & asexual).
CONJUGATION AND REPRODUCTION
8 7
2
MICRONUCLEARFUSION
Diploidmicronucleus
Diploidmicronucleus
Haploidmicronucleus
MEIOSIS
Compatiblemates
Key
ConjugationReproduction
Macronucleus
The original macro-nucleus disintegrates. Four micronuclei become macronuclei, while the other four remain micronuclei.
Micronuclei fuse,forming a diploid micronucleus.
Three rounds of mitosis without cytokinesis produce eight micronuclei.
Meiosis of micronuclei produces four haploidmicronuclei in each cell. 3 micronuclei in each cell
disintegrate. The remaining micro-nucleus in each cell divides by mitosis
The cells swap one micronucleus
The cellsseparate
Two rounds of cytokinesis partition one macronucleus and one micronucleus into each of four daughter cells.
ParameciumParamecium
50 µm
FEEDING, WASTE REMOVAL, AND WATER BALANCE
Stentor (Type of ciliate)Stentor (Type of ciliate)
Stramenopila
•Stramenopiles have “hairy” and smooth flagella
•The clade Stramenopila Includes:
–Water molds
–Diatoms
–Golden algae
–Brown algae
Smoothflagellum
Hairyflagellum
5 µm
Oomycetes–Include water molds, white rusts, and downy mildews
–Were once considered fungi based on morphological studies
–Are decomposers or parasites
–Have filaments (hyphae) that facilitate nutrient uptake
–Have cell walls made of cellulose
Diatoms •Are unicellular algae
–With a unique two-part, glass-like wall of hydrated silica
–major component of phytoplankton
3 µ
m
DiatomsDiatoms· Most numerous unicellular algae in the oceans and are an important source of food and
oxygen. · Also important in freshwater environments.
· Glucose stored as polysaccharide laminarin (Same as golden & brown algae)
· Their remains form diatomaceous earth.
DiatomsDiatoms
50 µm
~ 100 000 species
•Or chrysophytes
–Are named for their color, which results from their yellow & brown carotenoids
•The cells of golden algae
–Are typically bi-flagellated, with both flagella attached near one end of the cell
Golden Algae
25 µm
Brown algae
•Or phaeophytes
–Are the largest and most complex algae
–Are all multicellular, and most are marine
–Include many of the species commonly called seaweeds
•Seaweeds
–Have the most complex multi-cellular anatomy of all algae
Brown AlgaeBrown AlgaePhotosynthetic & multicellular · Range in size. Many are 50-100 m long.· Found along rocky shores
The thalus (plant like body) contains:· Holdfasts for attachment· Blades and air bladders that function in floatation · A stem-like structure that holds the blades is called a stipe.FucusCommon "seaweed" found along the rocky coast.
Blade
Stipe
Holdfast
Brown AlgaeBrown Algae
•Kelps, or giant seaweeds
–Live in deep parts of the ocean
–Can grow as long as 60m
Cell walls are composed of cellulose and gel forming polysaccharides which cushion the algae in the intertidal zone
Brown Algae - Brown Algae - Macrocystis Macrocystis and Nereocystisand Nereocystis (Deep water (Deep water
Kelp)Kelp)
Macrocystis
Nereocystis
•The most complex life cycles include an alternation of generations
–The alternation of multi-cellular haploid and diploid forms
Sporophyte(2n)
Zoospores
Female
Gametophytes(n)
MEIOSIS
FERTILIZATION
Developing sporophyte
Zygote(2n)
Mature femalegametophyte
(n)
Egg
Sperm
Male
Sporangia
Key
Haploid (n)Diploid (2n)
A variety of life cyclesHave evolved among the multi-cellular
algae
Cercozoans
•Cercozoans and radiolarians have threadlike pseudopodia
•A newly recognized clade, Cercozoa
–Contains a diversity of species that are among the organisms referred to as amoebas
•Amoebas were formerly defined as protists
–That move and feed by means of pseudopodia
•Cercozoans are distinguished from most other amoebas
Foraminiferans, or forams
–Are named for their porous, generally multichambered shells, called tests
20 µm
Pseudopodia extend through the pores in the test
Radiolarians•Marine protists
–Whose tests are fused into one delicate piece, which is generally made of silica
–Phagocytize microorganisms with their pseudopodia
•The pseudopodia of radiolarians, known as axopodia
–Radiate from the central body
200 µm
Axopodia
RadiolariansRadiolarians
Marine plankton (float in marine environments) with a skeleton composed of silica, and numerous needle-like pseudopodia.
Amoebozoans• Have lobe-shaped pseudopodia
–rather than threadlike, pseudopodia
–Include gymnamoebas, entamoebas, and slime molds
ProtozoansProtozoans· Do not have a cell wall
· Heterotrophic
· Usually motile · Food vacuoles
· Contractile vacuole (water elimination)
Reproduction is usually asexual but many also reproduce sexually during some part of their life cycle.
Gymnamoebas
–Are common unicellular amoebozoans in soil as well as freshwater and marine environments
•Most are heterotrophic
–And actively seek and consume bacteria and other protists
Pseudopodia
40 µm
Entamoeba
–Are parasites of vertebrates and some invertebrates
•Entamoeba histolytica
–Causes amebic dysentery in humans
AmoeboidsAmoeboids
Amoeba
Move by cytoplasmic extensions called pseudopodia.
Feed by phagocytizing (engulfing) their prey.
Most amoeboids are marine organisms;
Amoeba proteus is found in freshwater
AmoeboidsAmoeboids
Slime molds, or mycetozoans
–Were once thought to be fungi
•Molecular systematics
–Places slime molds in the clade Amoebozoa
–Plasmodial & Cellular types
The plasmodium–Is undivided by membranes and contains many diploid nuclei
–Extends pseudopodia through decomposing material, engulfing food by phagocytosis
Protists that are Decomposers Protists that are Decomposers (Saprotrophs)(Saprotrophs)
· Slime molds play an ecological role similar to that of fungi. · They are decomposers, feeding on dead organic material. · They differ from fungi in that slime molds ingest their food.
· Slime molds are masses that creep along the substrate and phagocytize dead organic material and microorganisms.
· The mass is one large cell referred to as a plasmodium.
· Spores are resistant to environmental extremes (Food and moisture) and germinate when environmental conditions become favorable
· Saprotrophic; they live off of dead organic matter.
Slime MoldsSlime Molds
Feedingplasmodium
Matureplasmodium(preparing to fruit)
Youngsporangium
Maturesporangium
Spores(n)
Germinatingspore
Amoeboid cells(n)
Zygote(2n)
1 mm
Key
Haploid (n)Diploid (2n)
MEIOSIS
SYNGAMY
StalkFlagellated cells(n)
Plasmodial Slime mold life cycle
Cellular slime molds
•Form multicellular aggregates
–In which the cells remain separated by their membranes
–Has become an experimental model for studying the evolution of multi-cellularity
Cellular Slime Mold Life Cycle
Spores(n)
Emergingamoeba
Solitary amoebas(feeding stage)
ASEXUALREPRODUCTIONFruiting
bodies
Aggregatedamoebas
Migratingaggregate
SYNGAMY
MEIOSIS
SEXUALREPRODUCTION
Zygote(2n)
Amoebas
600 µm
200 µm
Key
Haploid (n)Diploid (2n)
Algae
The word algae refers to aquatic (freshwater or marine) protists.
Algae photosynthesize like plants. They produce much of the oxygen in the atmosphere.
· Algae provide food for aquatic food chains.
Red & Green Algae
•Are the closest relatives of land plants
•Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont
–And the photosynthetic descendants of this ancient protist evolved into red algae and green algae
Red Algae• Are reddish in color
–Due to an accessory pigment call phycoerythrin, which masks the green of chlorophyll
Red Algae
• Red algae are found mainly in warmer, tropical oceans.
• Accessory photosynthetic pigments are called phycobilins which allow some species to survive in deep waters where blue and green light predominates.
• Some species are filamentous but most have a complex pattern of branching.
• Some coralline forms deposit calcium carbonate in their cell walls, making coral reefs.
Green Algae–Are named for their grass-green chloroplasts
–Are divided into two main groups: chlorophytes and charophyceans
–Are closely related to land plants
Green AlgaeGreen Algae
Single-celled and multicellular forms.
·
Ancestors of the first plants, both have the following characteristics in common:
They have a cell wall that contains cellulose.They have chlorophyllThey store their food as starch inside the
chloroplast.
Chlorophytes (green algae)
•Include:
–Unicellular, colonial, and multi-cellular forms
(a)
)
20 µm50 µm
UlvaUlva
• Multicellular with a leaf-like body that is two cells thick but up to one meter long
• Common name: Sea lettuce
VolvoxVolvox
· Colonial green algae
· They divide asexually to produce a daughter colony.
Notice the daughter colonies within the larger colonies.
VolvoxVolvox
• Some cells are specialized to produce sperm and eggs for sexual reproduction which is a characteristic of multicellular organisms.
• Considered to be a colony because it appears to be intermediate between a group of individual cells and a multicellular organism.
SpirogyraSpirogyra
· Filamentous form of green algae.
· Has a ribbonlike spiral-shaped chloroplast.
· Sexual reproduction occurs by conjugation. ·
The zygote is resistant and overwinters.
SpirogyraSpirogyra
Conjugation
Flagella
Cell wall
Nucleus
Regionsof singlechloroplast
Zoospores
ASEXUALREPRODUCTION
Mature cell(n)
SYNGAMY
SEXUALREPRODUCTION Zygote
(2n)
MEIOSIS
1 µm
Key
Haploid (n)
Diploid (2n)
++
+
+
Chlorophyte Life CycleHarsh environmental conditions
Normal environmental conditions
Protists Compared to Plants, Protists Compared to Plants,
Animals, and FungiAnimals, and Fungi • Characteristics resemble plants, animals, or fungi.
• Photosynthetic protists differ from plants in that they do not have structures that protect the gametes or zygote.
• Plants and animals undergo a period of embryonic development but protists do not.
• Fungi have cell walls composed of chitin; protists do not have chitin in their cell walls
• Fungi do not have cilia or flagella. Many kinds of protists have cilia or flagella.
Trophic Levels
Autotrophs:· green algae· brown algae· red algae· diatoms·
dinoflagellates· euglenoids
Heterotrophs:· amoeboids· ciliates· zooflagellates· sporozoans· slime molds