Transcript Nerve activates contraction

Figure 28.0x A ciliated protozoan
Chp. 28 - Protists (simple eukaryotes)
Figure 28.1a Too diverse for one kingdom: Amoeba proteus, a unicellular
"protozoan"
Animal like protist!
Figure 28.1b Too diverse for one kingdom: a diatom, a unicellular "alga"
Plant like protist!
Figure 28.1c Too diverse for one kingdom: a slime mold (Physarum polychalum)
Fungus like protist!
Figure 28.1d Too diverse for one kingdom: Australian bull kelp (Durvillea potatorum)
Multicellular protist!
The Protist problem
 Protista - at structural level (mostly unicellular eukaryotes)
and whatever did not fit the definitions of plants, fungi, or
animals.
 Includes singlecelled microscopic
members, simple
multicellular forms,
and complex giants
like seaweeds.
 Protists are paraphyletic -can be split into 20 Kingdoms!
 Some members more closely related to animals/plants/fungi
than other protists
Figure 28.2 The kingdom Protista problem
Protists - like a single cell?
Most diverse of all eukaryotes! 60,000 species
Plants and animals have specialized cells - neurons,
muscles, …; protist - one cell has to perform all the
functions.
Euglena: Eyespot+detector - light reception (eyes);
contractile vacoule - osmoregulation (kidneys);
chloroplast; flagellum - movement
Protists -nutrition
 Diverse! Not a reliable way to classify.
Most protists are aerobic (mitochondria)
The same group may include photosynthetic
species, heterotrophic species, and mixotrophs.
3 categoriesProtozoa- -- ingestive, animal-like protists ex. amoeba
Absorptive, fungus-like protists ex. slime-molds
Algae -- photosynthetic, plant-like protists.
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Protists - movement
 Flagella or cilia
 The eukaryotic flagella are not homologous to prokaryote
flagella.
 The eukaryotic flagella are like ‘oars’ - extensions of the
cytoplasm with a support of the 9 + 2 microtubule system.
Prokaryotic flagella - solid protein flagellin - no
microtubules; not covered by plasma membrane;
movement is like a spinning ‘propeller’
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QuickTime™ and a
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Prokaryotic and Eukaryotic flagella
 Prokaryotic - solid core of protein, no membrane, spinning propeller
 Eukaryotic - microtubules, covered by plasma membrane, oar like
with a power stroke
Protistan Habitats
 Aquatic organisms
 Damp soil, leaf litter
 Oceans, ponds, lakes
 Bottom dwellers
 Surface drifters -
plankton
 Phytoplankton (algae
and cyanobacteria)
 Symbionts—body
fluids, tissues, or cells
of hosts
Central concept: ENDOSYMBIOSIS - The Origin and
Early Diversification of Eukaryotes
1.
2.
3.
4.
5.
Endomembranes contributed to larger, more complex cells
Mitochondria and plastids evolved from endosymbiotic bacteria
The eukaryotic cell is a chimera of prokaryote ancestors
Secondary endosymbiosis increased the diversity of algae
Research on the relationships between the three domains is changing ideas
about the deepest branching in the tree of life
6. The origin of eukaryotes catalyzed a second great wave of diversification
What’s unique about eukaryotes?
- Membrane-enclosed
nucleus, the
endomembrane system,
mitochondria,
chloroplasts, the
cytoskeleton, 9 + 2
flagella, multiple
chromosomes of linear
DNA with organizing
proteins (ex: histones),
and life cycles with
mitosis, meiosis, and
sex. (KNOW THIS!)
Compartmentalization is a key event in the eukaryotic cell! How did the
eukaryotic cell get all these organelles (compartments)?
 The endomembrane system of eukaryotes (nuclear
envelope, endoplasmic reticulum, Golgi apparatus,
and related structures) may have evolved from
infoldings of plasma membrane.
 Another process, called endosymbiosis, probably led
to mitochondria, plastids, and perhaps other
eukaryotic features.
Fig. 28.4
Mitochondria and plastids evolved by
PRIMARY SERIAL ENDOSYMBIOSIS from
bacteria
 1) Ingestion of a heterotrophic aerobic prokaryote by a
simple eukaryote using a plasma membrane infolding/vacuole
(mutual advantage/symbiosis: glucose source for
prokaryote/cell resp for eukaryote (+/+); future
‘mitochondria’)
 2) Ingestion of an autotrophic prokaryote by this eukaryote
(photosynthesis; future ‘chloroplast’)
 Evidence supporting endosymbiosis of bacteria
to form organelles (important).
 1)Mitochondria/chloroplast and bacteria are similar is size.
 2) All 3 contain their own circular genome without
histones/other proteins; organelles have full transcription
machinery with ribosomes similar to prokaryotes
 3)Enzymes and transport systems in the inner membranes
of chloroplasts and mitochondria resemble those in the
plasma membrane of modern prokaryotes.
 4)Replication by mitochondria and chloroplasts resembles
binary fission in bacteria.
 5)Double membrane of the
organelles suggests
endocytosis/engulfing
Closest relatives of eukaryotes based on RNA
analysis?
 The eukaryotic cell is a chimera of prokaryotic
ancestors:
mitochondria from one bacteria (alpha
proteobacteria group)
plastids from another (cyanobacteria)
nuclear genome from the host cell
 Proteins in organelles may derive from
nuclear/organelle genome or combination
------> gene transfer has occurred
Secondary endosymbiosis increased
the diversity of algae
 Plastids vary in ultrastructure.
The chloroplasts of plants and green algae have
two membranes.
The plastids of others have three or four
membranes ex: Euglena
Figure 28.4 A model of the origin of eukaryotes
Figure 28.5 Secondary endosymbiosis and the origin of algal diversity
Secondary endosymbiosis increased
the diversity of algae
Algal groups with more than two plastid
membranes were acquired by secondary
endosymbiosis.
Primary endosymbiosis - protist engulfed
cyanobacteria - the ancestors of chloroplasts
Secondary endosymbiosis occurred when a
heterotrophic protist engulfed an algae
containing chloroplast. So triple membrane
around plastid. GET IT?
 Each endosymbiotic event adds a
membrane layer derived from the
vacuole membrane of the host cell.
Fig. 28.5
Web like and not tree like phylogeny
 Three domains arose from an ancestral community of
primitive cells that swapped DNA promiscuously.
 This explains the chimeric genomes of the three domains.
 Gene transfer across species lines is still common among
prokaryotes.
Archaea is
more
closely
related to
eukaryotes was the host
cell an
Archaean?
Fig. 28.8
Reproduction and Life Cycles
 Mitosis
 Asexual, meiosis and
syngamy (to produce
variation)
 Haploid stage: main
vegetative stage
 Diploid: zygote
 Cysts - tide over harsh
conditions
 Alternation of generation
CHAPTER 28 THE ORIGINS OF
EUKARYOTIC DIVERSITY
A Sample of Protistan Diversity
1. Diplomonadida and Parabasala: Diplomonads and parabasilids lack
mitochondria
2. Euglenozoa: The euglenozoa includes both photosynthetic and
heterotrophic flagellates
3. Alveolata: The alveolates are unicellular protists with subsurface cavities
(alveoli)
4. Stramenopila: The stramenopile clade that includes the water molds and
heterokont algae
CHAPTER 28 THE ORIGINS OF
EUKAYOTIC DIVERSITY
A Sample of Protistan Diversity (continued)
6. Some algae have life cycles with alternating multicellular haploid and
diploid generations
7. Rhodophyta: Red algae lack flagella
8. Chlorophyta: Green algae and plants evolved from a common
photoautotrophic ancestor
9. A diversity of protists use pseudopodia for movement and feeding
10. Mycetozoa: Slime molds have structural adaptations and life cycles that
enhance their ecological roles as decomposers
11. Multicellularity originated independently many times
DIPLOMONAD and PARABASILID
-NO/Reduced Mitochondria; multiple flagella, 2 nucleii
--Giardia -intestinal parasite - dyssentry
Figure 28.9 Giardia lamblia, a diplomonad
DIPLOMONAD and PARABASILID
-NO/Reduced Mitochondria; multiple flagella, 2 nucleii
--Trichomonas - female vaginal infections
Figure 28.10 Trichomonas vaginalis, a parabasalid
KINETOPLASTID (EUGLENAZOA)
-Have flagella, and kinetoplasts - multiple DNA loops inside
mitochondria
--Trypanosoma - African sleeping sickness
Figure 28.11x Trypanosoma, the kinetoplastid that causes sleeping sickness
Figure 28.03x Euglena
DINOFLAGELLATE (ALVEOLATA)
-Found in phytoplankton - plates of cellulose, 2 flagella in armor,
--Some cause red tides
--Some symbiotic (helpful) with coral reefs (bleaching if expelled!)
--Some bioluminiscent
Figure 28.12 A dinoflagellate
APICOMPLEXANS (ALVEOLATA)
-Parasites causing serious diseases like Plasmodium - that causes
malaria
--Needs an intermediary host - the mosquito
Figure 28.13 The two-host life history of Plasmodium, the apicomplexan that causes
malaria
CILIATES (ALVEOLATA)
-Have cilia; Ex: Paramecium, Stentor
--2 nucleii - macronucleus and micronucleus (sexual process)
-Oral groove - ingestion of food by phagocytosis
-- Contractile vacoule - pump excess water/ions (osmoregulation)
Figure 28.14c Ciliates: Paramecium, Stentor
CILIATES (ALVEOLATA)
Meiosis and conjugation (syngamy - exchange of micronuclei) are
separated from reproduction
Figure 28.15 Conjugation and genetic recombination in Paramecium caudatum
Figure 28.15x Paramecium conjugating
WATER MOLDS (STRAMENOPILA)
-Have hair like projections on flagellum (reproductive cells);
-Include oomycota - water molds, powdery mildew, rusts
--Have absorptive hyphae (like fungi)
--Some parasitic/disease causing in plants
Figure 28.16 The life cycle of a water mold (Layer 1)
Figure 28.16 The life cycle of a water mold (Layer 2)
Figure 28.16 The life cycle of a water mold (Layer 3)
Figure 28.16x1 Zoospore release
Figure 28.16x2 Water mold: Oogonium
Figure 28.x2 Powdery mildew
DIATOMS (STRAMENOPILA)
-Glasslike walls made of silica with 2 parts - shoebox and lid!
--Photosynthetic - called heterokont algae (2 typs of flagella)
-Makes the gritty stuff in toothpaste (diatomaceous earth)
--Has 3 layers surrounding the chloroplast (secondary endosymbiosis)
--This group includes golden algae and brown algae
Figure 28.17 Diatoms: Diatom diversity (left), Pinnularia (left)
Figure 28.17x Diatom shell
GOLDEN/BROWN ALGAE (STRAMENOPILA)
Like Leaf
Like Stem
Like Root
--Photosynthetic - called heterokont algae (2 typs of flagella)
--Includes golden (yellow and brown carotene pigment) algae and
brown (fucoxanthin) algae
BROWN ALGAE (STRAMENOPILA)
-Brown algae - kelp forests
-Grows rapidly - 60m or >
-Has structures analogous to plants like the holdfast (root), stipe (stem),
blade (leaf). Floats help leaf raise to surface.
Figure 28.20x1
Kelp forest
--Source of algin - used as a gel to stabilize baked goods
/ice cream
Figure 28.20x2 Kelp forest
Figure 28.21 The life cycle of Laminaria, Brown algae: an example of alternation of
generations
Alternation of
generations.
The diploid
individual, the
sporophyte,
produces haploid
spores (zoospores)
by meiosis.
The haploid individual,
the gametophyte,
produces gametes by
mitosis that fuse to
form a diploid zygote.
RED ALGAE (RHODOPHYTA)
- NO flagella
-Red algae -phycoerythrin
is the red pigment
--Primary endosymbiosis
produced the chloroplast
like plants and green algae
--Source of carageenin and
agar- used as a gel to
stabilize baked goods /ice
cream, culture medium
--Sushi wraps!
-Absorb blue and green
pigment - grow deeper in
the ocean waters
Figure 28.22 Red algae: Dulse (top), Bonnemaisonia hamifera (bottom)
GREEN ALGAE (CHLOROPHYTA and
CHAREOPHYCEANS)
-Green algae -chlorophyll is the green pigment
--Primary endosymbiosis produced the chloroplast
-Closest relative to all land plants (important)
-Unicellular and multicellular (Ulva/seaweed)
-Solitary (Chlamydomonas) and colonial forms (Volvox)
--Lichen has unicellular green algae symbiotically living with fungi
Figure 28.23 Colonial and multicellular chlorophytes: Volvox (left), Caulerpa (right)
Figure 28.x3 Spirogyra conjugating
Figure 28.24 The life cycle of Chlamydomonas
Most green algae have both sexual and
asexual reproductive stages.
Most sexual species have biflagellated gametes
with cup-shaped chloroplasts.
Figure 28.25 A hypothetical history of plastids in the photosynthetic eukaryotes
Figure 28.26 Use of pseudopodia for feeding
AMOEBA (RHIZOPODA) - uncertain phylogeny
 Rhizopods (amoebas) are all unicellular and use
pseudopodia to move and to feed.
 Pseudopodium (microtubules) emerge from
anywhere in the cell surface.
 To move, an amoeba extends a pseudopod, anchors
its tip, and then streams more cytoplasm into the
pseudopodium.
Fig. 28.26
 Actinopod (heliozoans and radiolarians), “ray foot,”
refers to slender pseudopodia (axopodia) that radiate
from the body.
 Each axopodium is reinforced by a bundle of microtubules
covered by a thin layer of cytoplasm.
 Radiolarium - skeleton makes ooze - thick layer at the
bottom of oceans
Fig. 28.27
Figure 28.27x Radiolarian skeleton
 Foraminiferans, or forams, are almost all
marine.
Most live in sand or attach to rocks or algae.
Some are abundant in the plankton.
Forams have multichambered, porous shells,
consisting of organic materials hardened with
calcium carbonate (deposit on the ocean floor).
Fig. 28.28
Figure 28.28 Foraminiferan
PLASMODIAL SLIME MOLD (MYCETOZOA)
 Like fungus - decomposers.
 The feeding stage is an amoeboid mass, the
plasmodium, that may be several
centimeters in diameter.
The plasmodium is
not multicellular,
but a single mass
of cytoplasm with
multiple nuclei.
Fig. 28.29
Figure 28.29 The life cycle of a plasmodial slime mold, such as Physarum
CELLULAR SLIME MOLD (MYCETOZOA)
The dominant stage in
a cellular slime mold is
the haploid stage.
Aggregates of amoebas
Fig. 28.30
form fruiting bodies that
produce spores in
asexual reproduction.
Most cellular slime
molds lack flagellated
stages.
Figure 28.29x1 Plasmodial slime mold
Figure 28.29x2 Slime mold Sporangia
Figure 28.30 The life cycle of a cellular slime mold (Dictyostelium)
Figure 28.30x1 Dictyostelium life cycle
Figure 28.30x2 Stages of Dictyostelium
Table 28.1 A Sample of Protistan Diversity
Multicellularity originated
independently many times
 The origin of unicellular eukaryotes
permitted more structural diversity than
was possible for prokaryotes.
 This ignited an explosion of biological
diversification.
 The evolution of multicellular bodies and
the possibility of even greater structural
diversity triggered another wave of
diversification.