Protists - Waterford Mott...
Transcript of Protists - Waterford Mott...
CHAPTER 28: PROTISTSAP Biology 2013
ProtistsSingle-celled (mostly - some colonial or multicellular)
Eukaryotes
Extremely diverse (more diverse than any other classification of eukaryotes)
Contain: photoautotrophs, heterotrophs, mixotrophs (both heterotrophic and autotrophic)
Diverse habitats (freshwater and marine species)
Both sexual and asexual life cycles
Figure 28.2a–d
100 µm
100 µm
4 cm
500 µm
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)
Table 28.1
Secondary EndosymbiosisCauses much of the diversity
Plastid-bearing lineages evolved into red algae and green algae
Cyanobacterium
Heterotrophic eukaryote
Primary endosymbiosis
Membranes are represented as dark lines in the cell.
1 2 3
One of these membranes was lost in red and green algal descendants.
Plastid
Red alga
Secondary endosymbiosis
Secondary endosymbiosis
Secondary endosymbiosis
Green alga
Dinoflagellates
Apicomplexans
Stramenopiles
Plastid
Euglenids
Chlorarachniophytes Fig. 28.2
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2
3
Eukaryotic Clades Diplomonads
Parabasalids
Euglenozoans
Dinoflagellates
Apicomplexans
Ciliates
Diatoms
Golden algae
Brown algae
Oomycetes
Cercozoans
Forams
Radiolarians
Red algae
Chlorophytes
Charophytes
Land plants
Slime molds
Gymnamoebas
Entamoebas
Nucleariids
Fungi
Choanoflagellates
Animals
Alveolates
Stramenopiles
Green
algae
Am
oebozoans O
pisthokonts
Excavata C
hromalveolata
Rhizaria
Archaeplastida
Unikonta
Fig. 28.3
Understanding of protists continues to change rapidly
One hypothesis divides all eukaryotes into five supergroups
Diatom diversity
50 µm
Volvox, a colonial freshwater green alga
20 µm 50 µm
A unikont amoeba 100 µm
Excavata
Characterized by its cytoskeleton
Have modified mitochondria that lack DNA, electron transport chain, and citric acid cycle enzymes
Adapted to anaerobic environments
Lack plastids
Diplomonads - two nuclei and multiple flagella
Parabasalids - move by means of flagella and undulating plasma membrane
Flagella
5 µ
m
Undulating membrane
Fig. 28.4
EugenozoansInclude predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites
Main distinguishing characteristic is a spiral or crystalline rod of unknown function inside the flagella
Kinetoplastids - single large mitochondrion (kinetoplast) (ex. Trypanosoma - parasitic causes sleeping sickness in humans)
Euglenids - have one or two flagella
Crystalline rod (cross section)
Flagella
Ring of microtubules (cross section)
8 µm
0.2 µm
Fig. 28.5
9 µm
Fig. 28.6
Long flagellum
Eyespot
Short flagellum
Contractile vacuole
Nucleus
Chloroplast
Plasma membrane
Euglena (LM) 5 µm Pellicle
Light detector Fig.
28.7
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5
6
ChromalveolatesMay be monophyletic and originated by a secondary endosymbiosis event
Like many protist clades, it is controversial.
Alveolates - membrane bound sacs (alveoli) under the plasma membrane
Dinoflagellates - aquatic photoautotrophs and heterotrophs that have a characteristic shape (reinforced by internal plates of cellulose), two flagella that make them spin as they move, and rapid growth causes “red tides” (can be toxic to humans)
Ciliates - use cilia to move and have macronuclei and micronuclei (use conjugation to exchange micronuclei)
Flagellum Alveoli
Alveolate
0.2 µ
m
Fig. 28.8
Flagella
3 µ
m
Fig. 28.9
Conjugation Asexual reproduction
Key
MEIOSIS
MICRONUCLEAR FUSION
Diploid micronucleus
Diploid micronucleus
Haploid micronucleus
Compatible mates
The original macronucleus disintegrates.
(b) Conjugation and reproduction
Fig. 28.11
ChromalveolatesApicomplexans - parasites of animals
Ex. Plasmodium is the parasite that causes malaria
Requires both mosquitos and humans to complete life cycle
900,000 people die each year from malaria
Sporozoites (n)
Oocyst
Zygote (2n)
Merozoite (n)
Gametes
Liver
Liver cell
Red blood cells
Gametocytes (n)
Merozoite
Apex
0.5 µm Red blood cell
Key
Haploid (n) Diploid (2n)
Inside mosquito Inside human
MEIOSIS
FERTILIZATION
Fig. 28.10
ChromalveolatesStramenopila - photoautotrophs and heterotrophs
Most have “hairy” flagellum paired with a “smooth” flagellum
Diatoms - glass-like wall of hydrated silica, reproduce both sexually and asexually (major component of phytoplankton)
Golden Algae - some unicellular some colonial
Oomycetes - water molds, downy mildews, and white rusts
Smooth flagellum
Hairy flagellum
5 µm
Fig. 28.12
40 µ
m
Flagellum
Outer container
Living cell
25 µm
Fig. 28.14
Apicomplexans Ciliates
Diatoms
Stramenopiles
Alveolates
Chrom
alveolata
Rhizaria Archaeplastida Unikonta
Dinoflagellates
Golden algae Brown algae Oomycetes
Excavata
Germ tube
Cyst
Hyphae ASEXUAL REPRODUCTION
Zoospore (2n)
Zoosporangium (2n)
Zygote germination SEXUAL
REPRODUCTION
Key
Haploid (n) Diploid (2n)
MEIOSIS
FERTILIZATION Zygotes (oospores) (2n)
Antheridial hypha with sperm nuclei (n)
Egg nucleus (n)
Oogonium
Fig. 28.13
Fig. 28.17
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8
9
ChromalveolatesBrown Algae - largest and most complex algae
Multicellular and mostly marine (commonly referred to as seaweeds)
Algal body is plant-like but lack true roots, stems, and leaves
Has a holdfast (rootlike), stipe (stemlike), and blades (leaflike)
Alteration of generations
Blade
Stipe
Holdfast
Fig. 28.15
10 cm
Mature female gametophyte (n)
Developing sporophyte
Zygote (2n)
Haploid (n) Diploid (2n)
Key
Sporangia
Gametophytes (n)
Zoospore
Female
Male
Sperm
MEIOSIS
FERTILIZATION
Sporophyte (2n)
Egg
Fig. 28.16
RhizariansDNA evidence supports this as a monophyletic clade
Amoebas - move and feed by pseudopodia
Radiolarians - pseudopodia radiate from central body
Foraminiferans - multichambered shells
Cercozoans - most are heterotrophic parasites and predators
Radiolarians Foraminiferans Cercozoans
Rhizaria
Excavata Chromalveolata
Archaeplastida Unikonta
Pseudopodia
200 µm
Fig. 28.18
Chromatophore
5 µm
Fig. 28.19
ArchaeplastidaLand plants are descended from the green algae
Includes red algae, green algae, and land plants
Red algae - most abundant large algae in tropics
Green algae - paraphyletic group that gave rise to land plants
Chlorophytes Charophytes
Archaeplastida
Excavata Chromalveolata Rhizaria
Unikonta
Red algae
Green algae
Land plants
20 cm
8 mm
Bonnemaisonia hamifera
Dulse (Palmaria palmata)
Nori
Fig. 28.20(a) Ulva, or sea lettuce
(b) Caulerpa, an intertidal chlorophyte
2 cm
Fig. 28.21
Flagella
Cell wall
Nucleus
Cross section of cup-shaped chloroplast
1 µm
(TEM)
Zoospore
ASEXUAL REPRODUCTION SEXUAL
REPRODUCTION
Gamete (n)
Mature cell (n)
Zygote (2n)
FERTILIZATION
MEIOSIS Key
Haploid (n) Diploid (2n)
-
-
-
- +
+
+
+
Fig. 28.22
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11
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Cercozoans and RadiolariansCercozonans (type of amoebas) - move by thread-like pseudopodia
Foraminiferans - named for porous, multichambered shells called tests (pseudopods extend through pores in tests)
Radiolarians (marine protists)
Tests fused into one delicate piece made of silica
Pesudopodia known as axopodia
Figure 28.22
20 µm
Figure 28.23 200 µm
Axopodia
Unikonts
Group that contains animals, fungi, and some protists
Amoebozoans - amoeba that include slime molds
Choanoflagellates Animals
Unikonta
Excavata Chromalveolata Rhizaria Archaeplastida
Amoebozoans
Nucleariids Fungi
Stalk
Zygote (2n)
FERTILIZATION
MEIOSIS
Amoeboid cells (n)
Germinating spore
Spores (n)
Flagellated cells (n)
Mature sporangium
Young sporangium
Feeding plasmodium
Mature plasmodium (preparing to fruit)
4 cm
1 mm
Key
Haploid (n) Diploid (2n)
Fig. 28.24
Spores (n)
600 µm
200 µm
Solitary amoebas (n)
Emerging amoeba (n)
Fruiting bodies (n)
Aggregated amoebas
Amoebas (n) ASEXUAL REPRODUCTION
SEXUAL REPRODUCTION
Zygote (2n)
Migrating aggregate
Key
Haploid (n) Diploid (2n)
FERTILIZATION
MEIOSIS
Fig. 28.25Plasmodial Slime Mold
Cellular Slime Mold
Role in EnvironmentSymbiotic protists
Dinoflagellates nourish coral polyps that build reefs, wood-digesting protists digest cellulose in the gut of termites
Parasites
Plasmodium causes malaria, Phytophthora ramorum causes sudden oak death
Producers
Photosynthetic protists and prokaryotes are the main producers in aquatic environments
Populations will explode when limiting nutrients are added
Biomass has declined as sea surface temperature increases
Herbivorous plankton
Other consumers
Carnivorous plankton
Protistan producers
Prokaryotic producers
Fig. 28.27
Higher Lower
SST SST
Growth Growth In regions between the black lines, a layer of warm water rests on top of colder waters.
In the yellow regions, high SSTs increase the temperature differences between warm and cold waters, which reduces upwelling.
Fig. 28.28
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