1. Red tide—population explosion of
certain types of dinoflagellates.
Kills large amounts of fish.
Depletes water of oxygen and
releases toxins into the water.
Apicomplexans
• 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 nonphotosynthetic plastid, the
apicoplast
Flagellated Alveolates
• Apicomplexans
Plasmodium spp. Life cycle
Malaria
merozoites about to rupture a red blood cell
1

2. Plasmodium sp. life cycle
sporozoite
It takes two hosts
to complete sporozoites
merozoite
male gametocyte in red blood cell
Fig. 22-11, p.359
Stramenopiles
• Stramenopiles have “hairy” and smooth
flagella
• The clade Stramenopila
– Includes several groups of heterotrophs as
well as certain groups of algae
• Most stramenopiles
– Have a “hairy” flagellum paired with a
“smooth” flagellum during some part of
their life cycle
Hairy
flagellum
Smooth
flagellum
5 µm
2

3. Photosynthetic Stramenopiles
• Chrysophytes
Chrysophytes
Golden algae Yellow-green algae
coccolithophores
diatoms
p.351b
3

4. • Diatoms are unicellular algae
– With a unique two-part, glass-like wall of
hydrated silica
3 µm
• Diatoms are a major component of
phytoplankton
– And are highly diverse
50 µm
Photosynthetic Stramenopiles
Brown Algae
• Brown algae, or phaeophytes
– Are the largest and most complex algae
– Are all multicellular, and most are marine
4

5. Photosynthetic Stramenopiles
• Brown Algae
bladder
blade
stipe
holdfast
Kelp -- Macrocystis
Diversity of Kingdom Protista
Phylum Phaeophyta: brown algae
Underwater
forests—
habitats
Kelp—food,
habitats for
aquatic
organisms
Pectin—used to
make gelatin
Alternation of Generations
• A variety of life cycles
– Have evolved among the multicellular algae
• The most complex life cycles include an
alternation of generations
– The alternation of multicellular haploid and
diploid forms
5

6. Colorless Stramenopiles
• Oomycotes (egg
fungi)
Oogonium
Colorless Stramenopiles
•Oomycotes (egg fungi)
water molds
Phytophtora
Saprolegnia
Alternation of generations in Saprolegnia
6

7. Algae
Red algae and 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
• Red algae
– Are usually multicellular; the largest are
seaweeds
– Are the most abundant large algae in coastal
waters of the tropics
(b) Dulse (Palmaria palmata). This edible
species has a “leafy” form.
(c) A coralline alga. The cell walls of
coralline algae are hardened by calcium
carbonate. Some coralline algae are
members of the biological communities
around coral reefs.
(a) Bonnemaisonia hamifera. This red alga
has a filamentous form.
7

8. Red Algae
• Red algae are reddish in color
– Due to an accessory pigment call
phycoerythrin, which masks the green of
chlorophyll
Green Algae
• Two groups – Chlorophytes &
Charophytes
• All have chlorophylls a & b
• Some are symbionts
Green Algae
• Chlorophytes
8

9. • Most chlorophytes
– Live in fresh water, although many are
marine
• Other chlorophytes
– Live in damp soil, as symbionts in lichens, or
in snow
Ulva – sea lettuce
Fig. 22-19a1, p.364
Volvox colony
Fig. 22-19c, p.364
9

10. Chlamydomonas
Environment-resistant zygote
Fig. 22-20b, p.365
Green Algae
• Life Cycle Model
Alteration of generations in Chlamydomonas
e A thin-walled resistant
zygote f
zygote develops.
(cross-section)
d
Diploid Stage meiosis and
nuclear
germination
Haploid Stage
fusion
haploid cell
haploid cell
(+ strain)
(– strain)
g Mitosis occurs. Whether the resulting
c cells develop into spores or gametes will
depend on environmental conditions.
b
cytoplasmic
fusion SEXUAL ASEXUAL ASEXUAL
REPRODUCTION: REPRODUCTION: REPRODUCTION:
Mainly when
nitrogen levels are
low and light is of More spores
More spores
a certain quality a are produced.
are produced.
and intensity, the
+ cells develop into
_ gametes.
+
Gametes
of different
_
mating types
meet.
Fig. 22-20a, p.365
10

11. Amoebozoa
• Amoebozoans have lobe-shaped
pseudopodia
• Amoebozoans
– Are amoeba that have lobe-shaped, rather
than threadlike, pseudopodia
– Include gymnamoebas, entamoebas, and
slime molds
A. proteus
Fig. 22-21, p.366
Heterotroph
pseudopod
11

12. Amoebic dysentary
Entamoeba histolytica
Amoebozoa
• Slime Molds
• plasmodial (Myxomycetes)
Plasmodia --- multinucleated cytoplasmic mass
Fig. 22-22a, p.366
12

13. Hard times produce fruiting bodies
Good times, spores germinate
Produce ‘gametes’ – fusion of two
Fruiting bodies produce haploid spores
= new plasmodium
Fig. 22-22b, p.366
• At one point in the life cycle
– They form a mass called a plasmodium
3 The plasmodium erects
2 The plasmodium
1 The feeding stage stalked fruiting bodies (sporangia)
takes a weblike form.
is a multinucleate when conditions become harsh.
plasmodium that lives
on organic refuse.
Mature
Feeding
plasmodium
plasmodium
(preparing to fruit)
Zygote
(2n)
Young
sporangium
SYNGAMY
1 mm
Mature
Amoeboid cells
sporangium
(n)
Key
MEIOSIS
Spores
Germinating Haploid (n)
(n)
spore
Diploid (2n)
Flagellated cells
Stalk
(n)
7 The cells unite
6 These cells are
in pairs (flagellated 5 The resistant spores disperse
4
with flagellated through the air to new locations
either amoeboid or Within the bulbous
and amoeboid with and germinate, becoming active
flagellated; the two tips of the sporangia,
amoeboid), forming haploid cells when conditions
forms readily convert meiosis produces haploid
diploid zygotes. are favorable.
from one to the other. spores.
Amoebozoa
• Slime Molds
• cellular slime molds (Amoeba-like)
13

14. clip
Fig. 22-23f, p.367
• The life cycle of Dictyostelium, a cellular
slime mold
9 In a favorable 1 In the feeding 2 During sexual repro-
environment, amoebas stage of the life duction, two haploid
emerge from the spore cycle, solitary haploid amoebas fuse and
coats and begin feeding. amoebas engulf bacteria. form a zygote.
3 The zygote
8 Spores becomes a giant
SYNGAMY
are released. cell (not shown)
by consuming
7 Other Emerging
haploid amoebas.
cells crawl Zygote
Spores amoeba After developing a
up the stalk (2n)
(n) resistant wall, the
SEXUAL
and develop
giant cell undergoes
REPRODUCTION
into spores. Solitary amoebas meiosis followed by
600 µm MEIOSIS
(feeding stage) several mitotic
Amoebas divisions.
ASEXUAL
REPRODUCTION
Fruiting 4 The resistant
bodies wall ruptures,
releasing new
Aggregated
haploid amoebas.
amoebas
5 When food is depleted,
Migrating hundreds of amoebas
aggregate congregate in response to a
chemical attractant and form
a sluglike aggregate (photo
below left). Aggregate
6 The aggregate migrates for a
formation is the beginning
while and then stops. Some of the
of asexual reproduction.
cells dry up after forming a stalk that
supports an asexual fruiting body. Key
Haploid (n)
Figure 28.27 200 µm Diploid (2n)
14

15. 1 Stalked, spore-producing
structure releases spores.
MITOTIC
CELL
DIVISION
2 Spores give
rise to free-living
MATURE amoeboid cells
FRUITING that feed, grow,
BODY and reproduce
AGGREGATION
by mitotic cell
division.
CULMINATION
3 When food
gets scarce, the
cells will stream
together to form
an aggregate
that crawls like a
slug.
4 The slug may
either start developing
or
at once into a
MIGRATING
spore-bearing
SLUG STAGE
structure, or it
may migrate
elsewhere first.
Fig. 22-23a, p.367
a Life cycle of Dictyostelium discoideum.
midwife amoeba attracted to two
stuck-together daughter cells
p.367
LE 16-25
The evolution of multicellular organisms
Gamete
Locomotor
cells
Somatic
cells
Food-
synthesizing
cells
Colony Early multicellular organism Later organism that
Unicellular protist
with specialized, interdepen- produces gametes
dent cells
15