Figure 28.0x A ciliated protozoan

1
Figure 28.0x A ciliated protozoan
Chp. 28 - Protists (simple eukaryotes)
2
Figure 28.1a Too diverse for one kingdom Amoeba
proteus, a unicellular "protozoan"
Animal like protist!
3
Figure 28.1b Too diverse for one kingdom a
diatom, a unicellular "alga"
Plant like protist!
4
Figure 28.1c Too diverse for one kingdom a
slime mold (Physarum polychalum)
Fungus like protist!
5
Figure 28.1d Too diverse for one kingdom
Australian bull kelp (Durvillea potatorum)
Multicellular protist!
6
The Protist problem

• Protista - at structural level (mostly
  unicellular eukaryotes) and whatever did not fit
  the definitions of plants, fungi, or animals.
• Includes single-celled 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

7
Figure 28.2 The kingdom Protista problem
8
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 Eyespotdetector - light reception
  (eyes) contractile vacoule - osmoregulation
  (kidneys) chloroplast flagellum - movement

9
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.

10
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

11
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

12
Protistan Habitats

• Aquatic organisms
• Damp soil, leaf litter
• Oceans, ponds, lakes
• Bottom dwellers
• Surface drifters - plankton
• Phytoplankton (algae and cyanobacteria)
• Symbiontsbody fluids, tissues, or cells of hosts

13
Central concept ENDOSYMBIOSIS - The Origin and
Early Diversification of Eukaryotes
1. Endomembranes contributed to larger, more
complex cells 2. Mitochondria and plastids
evolved from endosymbiotic bacteria 3. The
eukaryotic cell is a chimera of prokaryote
ancestors 4. Secondary endosymbiosis increased
the diversity of algae 5. 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
14
Whats 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)?
15

• 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
16
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)

17
(No Transcript)
18

• 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

19
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

20

• Proteins in organelles may derive from
  nuclear/organelle genome or combination ------gt
  gene transfer has occurred

21
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

22
Figure 28.4 A model of the origin of eukaryotes
23
Figure 28.5 Secondary endosymbiosis and the
origin of algal diversity
24
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?

25

• Each endosymbiotic event adds a membrane layer
  derived from the vacuole membrane of the host
  cell.

Fig. 28.5
26
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?
27
Fig. 28.8
28
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

29
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
30
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
31
Figure 28.9 Giardia lamblia, a diplomonad
DIPLOMONAD and PARABASILID

• NO/Reduced Mitochondria multiple flagella, 2
  nucleii
• -Giardia -intestinal parasite - dyssentry

32
Figure 28.10 Trichomonas vaginalis, a parabasalid
DIPLOMONAD and PARABASILID

• NO/Reduced Mitochondria multiple flagella, 2
  nucleii
• -Trichomonas - female vaginal infections

33
Figure 28.11x Trypanosoma, the kinetoplastid
that causes sleeping sickness
KINETOPLASTID (EUGLENAZOA)

• Have flagella, and kinetoplasts - multiple DNA
  loops inside mitochondria
• -Trypanosoma - African sleeping sickness

34
Figure 28.03x Euglena
35
Figure 28.12 A dinoflagellate
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

36
Figure 28.13 The two-host life history of
Plasmodium, the apicomplexan that causes malaria
APICOMPLEXANS (ALVEOLATA)

• Parasites causing serious diseases like
  Plasmodium - that causes malaria
• -Needs an intermediary host - the mosquito

37
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
38
Figure 28.15 Conjugation and genetic
recombination in Paramecium caudatum
CILIATES (ALVEOLATA)
Meiosis and conjugation (syngamy - exchange of
micronuclei) are separated from reproduction
39
Figure 28.15x Paramecium conjugating
40
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

41
Figure 28.16 The life cycle of a water mold
(Layer 1)
42
Figure 28.16 The life cycle of a water mold
(Layer 2)
43
Figure 28.16 The life cycle of a water mold
(Layer 3)
44
Figure 28.16x1 Zoospore release
45
Figure 28.16x2 Water mold Oogonium
46
Figure 28.x2 Powdery mildew
47
Figure 28.17 Diatoms Diatom diversity (left),
Pinnularia (left)
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

48
Figure 28.17x Diatom shell
49
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

50
Figure 28.20x1 Kelp forest
BROWN ALGAE (STRAMENOPILA)

• Brown algae - kelp forests
• Grows rapidly - 60m or gt
• Has structures analogous to plants like the
  holdfast (root), stipe (stem), blade (leaf).
  Floats help leaf raise to surface.
• -Source of algin - used as a gel to stabilize
  baked goods /ice cream

51
Figure 28.20x2 Kelp forest
52
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.

53
Figure 28.22 Red algae Dulse (top),
Bonnemaisonia hamifera (bottom)
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

54
Figure 28.23 Colonial and multicellular
chlorophytes Volvox (left), Caulerpa (right)
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

55
Figure 28.x3 Spirogyra conjugating
56
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.

57
Figure 28.25 A hypothetical history of plastids
in the photosynthetic eukaryotes
58
Figure 28.26 Use of pseudopodia for feeding
59
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
60

• 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
61
Figure 28.27x Radiolarian skeleton
62

• 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
63
Figure 28.28 Foraminiferan
64

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
65
Figure 28.29 The life cycle of a plasmodial
slime mold, such as Physarum
66

CELLULAR SLIME MOLD (MYCETOZOA)

• The dominant stage in a cellular slime mold is
  the haploid stage.
• Aggregates of amoebas form fruiting bodies that
  produce spores in asexual reproduction.
• Most cellular slime molds lack flagellated stages.

Fig. 28.30
67
Figure 28.29x1 Plasmodial slime mold
68
Figure 28.29x2 Slime mold Sporangia
69
Figure 28.30 The life cycle of a cellular slime
mold (Dictyostelium)
70
Figure 28.30x1 Dictyostelium life cycle
71
Figure 28.30x2 Stages of Dictyostelium
72
Table 28.1 A Sample of Protistan Diversity
73
(No Transcript)
74
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.