27. LE 28-12a
FEEDING, WASTE REMOVAL, AND WATER BALANCE
Contractile
vacuole
Paramecium, like other freshwater
protists, constantly takes in water
by osmosis from the hypotonic
environment. Bladderlike contractile
vacuoles accumulate excess water
from radial canals and periodically
expel it through the plasma membrane.
Paramecium feeds mainly on bacteria.
Rows of cilia along a funnel-shaped oral
groove move food into the cell mouth,
where the food is engulfed into food
vacuoles by phagocytosis.
Oral groove
Cell mouth
Thousands of cilia cover the
surface of Paramecium.
50 µm
Food vacuoles combine with lysosomes.
As the food is digested, the vacuoles
follow a looping path through the cell.
Micronucleus
Macronucleus
The undigested contents of food
vacuoles are released when the
vacuoles fuse with a specialized
region of the plasma membrane
that functions as an anal pore.
28. LE 28-12
FEEDING, WASTE REMOVAL, AND WATER BALANCE
Paramecium, like other freshwater
protists, constantly takes in water
by osmosis from the hypotonic
environment. Bladderlike
contractile vacuoles accumulate
excess water from radial canals
and periodically expel it through
the plasma membrane.
Contractile
vacuole
Paramecium feeds mainly on bacteria.
Rows of cilia along a funnel-shaped oral
groove move food into the cell mouth,
where the food is engulfed into food
vacuoles by phagocytosis.
Oral groove
Cell mouth
Thousands of cilia cover the
surface of Paramecium.
Food vacuoles combine with lysosomes.
As the food is digested, the vacuoles
follow a looping path through the cell.
50 µm
Micronucleus
The undigested contents of food
vacuoles are released when the
vacuoles fuse with a specialized
region of the plasma membrane
that functions as an anal pore.
Macronucleus
CONJUGATION AND REPRODUCTION
Meiosis of micronuclei
produces four haploid
micronuclei in each cell.
Two cells of compatible
mating strains align side by
side and partially fuse.
Compatible
mates
Three micronuclei in each cell
disintegrate. The remaining micronucleus in each cell divides by mitosis.
Macronucleus
The cells swap
one micronucleus.
MEIOSIS
Haploid
micronucleus
Diploid
micronucleus
Diploid
micronucleus
MICRONUCLEAR
FUSION
The cells
separate.
Two rounds of
cytokinesis partition
one maccronucleus
and one
macronucleus into
each of four
daughter cells.
The original
macronucleus
disintegrates. Four
micronuclei become
macronuclei, while
the other four
remain micronuclei.
Micronuclei
Three rounds
of mitosis without fuse, forming
a diploid
cytokinesis
micronucleus.
produce eight
micronuclei.
Key
Conjugation
Reproduction
29. LE 28-12b
CONJUGATION AND REPRODUCTION
Meiosis of micronuclei
Three micronuclei in each cell
produces four haploid
disintegrate. The remaining micromicronuclei in each cell. nucleus in each cell divides by mitosis.
Two cells of compatible
mating strains align side by
side and partially fuse.
Compatible
mates
Macronucleus
The cells swap
one micronucleus.
MEIOSIS
Haploid
micronucleus
Diploid
micronucleus
Diploid
micronucleus
MICRONUCLEAR
FUSION
The cells
separate.
Two rounds of
cytokinesis
partition one
macronucleus and
one macronucleus
into each of four
daughter cells.
The original
macronucleus
disintegrates. Four
micronuclei become
macronuclei, while
the other four
remain micronuclei.
Three rounds
Micronuclei
of mitosis
fuse, forming
without
a diploid
cytokinesis
micronucleus.
produce eight
micronuclei.
Key
Conjugation
Reproduction
44. LE 28-21
C
I
C
L
O
Key
Haploid (n)
Diploid (2n)
Sporangia
D
E
esporangio
V
I
D
A
D
E
L
A
M
I
N
A
R
I
A
MEIOSIS
zoosporas
Zoospores
Esporofito
2n
Femenino
Esporofito en vías
De desarrollo
Gametophytes
(n)
Zygote
(2n)
Gametofito femenino
maduro
(n)
FERTILIZATION
Egg
oosfera
masculino
anterozoide
48. LE 28-20
El alga de mar se
cultiva sobre redes en
aguas costeras poco
profundas. Porphyra
( alga roja )
un operario
esparce las algas de
mar recolectadas
sobre pantallas de
bambú para que se
sequen
lasláminas satinadas de
nori, delgadas como un papel,
constituyen una envoltura rica
en minerales para el arroz,
mariscos y vegetales que
forman el sushi
49. LE 28-28
Dulse (Palmaria palmata). This
edible species has a “leafy” form.
A coralline alga. The cells walls of
corralline algae are hardened by
calcium carbonate. Some coralline
algae are members of the biological
communities called coral reefs.
Bonnemaisonia hamifera, a
filamentous red alga.
Palmaria palmata
51. LE 28-30
20 µm
50 µm
Volox, a colonial freshwater chlorophyte. The colony is a
hollow ball whose wall is composed of hundreds or
thousands of biflagellated cells (see inset LM) embedded in
a gelatinous matrix. The cells are usually connected by
strands of cytoplasm; if isolated, these cells cannot
reproduce. The large colonies seen here will eventually
release the small “daughter” colonies within them (LM).
Calperpa, an
inter-tidal
chlorophyte. The
branched filaments
lack cross-walls and
thus are
multinucleate. In
effect, the thallus is
one huge “supercell.”
Ulva, or sea lettuce. This edible seaweed has a
multicellular thallus differentiated into leaflike
blades and a rootlike holdfast that anchors the
alga against turbulent waves and tides.
52. LE 28-31
Flagella
1 µm
Cell wall
Nucleus
Zoospores
Regions
of single
chloroplast
Key
Haploid (n)
Diploid (2n)
ASEXUAL
REPRODUCTION
SYNGAMY
Mature cell
(n)
SEXUAL
REPRODUCTION
MEIOSIS
Zygote
(2n)