CHAPTER 19
Algae and the Origin
of Eukaryotic Cells
Topic's Outline
3
2
1
Origin of
Eukaryotes
Green Algae
Characteristics of
Various Groups of
Algae
5
Brown Algae and Their
Relatives: The Heterokonts
4
6
Dinoflagellates
Red Algae
7
Euglenoids
Eukaryotes
Eukaryote refers to any of the single-celled or
multicellular organisms whose cell contains a
distinct, membrane-bound nucleus. Organisms such
as animals, plants, fungi, and protists are examples of
eukaryotes because their cells are organized into
compartmentalized structures called organelles
Nucleus
The primary functions of the nucleus are to store the
cell's DNA, maintain its integrity, and facilitate its
transcription and replication.
Vacoule
A vacuole is a membrane-bound cell organelle. In
animal cells, vacuoles are generally small and help
sequester waste products.
Golgi apparatus
The Golgi apparatus, or Golgi complex, functions as a
factory in which proteins received from the ER are
further processed and sorted for transport to their
eventual destinations: lysosomes, the plasma
membrane, or secretion.
Lysosome
Lysosomes function as the digestive system of the
cell, serving both to degrade material taken up from
outside the cell and to digest obsolete components
of the cell itself.
Mitochondria
Mitochondria are membrane-bound cell organelles
that generate most of the chemical energy needed to
power the cell's biochemical reactions.
Centrioles
Centrioles are paired barrel-shaped organelles
located in the cytoplasm of animal cells near the
nuclear envelope. Centrioles play a role in organizing
microtubules that serve as the cell's skeletal system.
They help determine the locations of the nucleus and
other organelles within the cell.
Eukaryotic Cell
Prokaryotic Cell
Any cell that contains a clearly defined nucleus and
Do not posses a nucleus or membrane bound
membrane bound organelles
organelles
Belong to kingdom Protista, Planta, Fungi and
Belong to kingdom Monera
Animalia
Include bacteria and cyanobacteria
Include animals, fungi, protozoa and algae
0.2-2 micrometer in diameter
10-100 micrometer in diameter
Unicellular organisms
Multicellular organisms
Have a single, circular DNA molecule in the
Have multiple, linear chromosomes in the nucleus
nucleoid
Cell walls are made up of cellulose, chitin and
Cell walls are mostly made up of peptidoglycans
pectin
Contain primitive cytoskeleton without
Contain a complex cytoskeleton and cytoplasmic
cystoplasmic streaming
streaming
Cell division occurs through binary fission
Cell division takes place through mitosis
Sexual reproduction occurs by conjugation
Sexual reproduction occurs through the
production of gametes
Algae
Algae is an informal term for a large and diverse group
of photosynthetic eukaryotic organisms. It is a
polyphyletic grouping that includes species from
multiple distinct clades. Included organisms range
from unicellular microalgae, such as Chlorella,
Prototheca and the diatoms, to multicellular forms,
such as the giant kelp. Most are aquatic and
autotrophic and lack many of the distinct cell and
tissue types, such as stomata, xylem and phloem that
are found in land plants.
Endosymbiotic Theory
Endosymbiotic theory is a theory suggesting that the organelles such as
mitochondria and chloroplasts within the eukaryotic cell came about as a
result of the early endosymbiosis between prokaryotic endosymbionts and
eukaryotic host cell.
This form of symbiosis involves a larger cell that serves as a host and a smaller
cell that is referred to as an endosymbiont.
the host cell possess a nucleus
In endosymbiotic theory, it posited that the larger cell engulfed or took in the
smaller cell. The larger cell represents the eukaryotic cell of today whereas the
smaller cell is the prokaryotic cell.
Indications the Theory is
plausible:
Both mitochondria and plastids are capable of reproducing their own through
a process a kin to prokaryotic binary fission.
two or more bodies
Both mitochondria and plastids have single circular DNA similar to that of a
bacteria in terms of size and structure but different from that one of the
nucleus of the cell.
Porin in the outer membranes of mitochondria and chloroplasts are similar to
those in the bacterial cell membrane and inner mitochondrial membrane.
Various algae evolved
by means of primary and
secondary endosymbiosis.
primary endosymbiosis
Chloroplast
Chloroplasts have
evolved when a
two sets of cell
eukaryotic cell
membranes
containing
surrounding them,
mitochondria
one from the host
engulfed a
cell and one from
photosynthetic
the endosymbiont.
cyanobacteria cell.
Primary
Endosymbiosis
Red and green algae have evolved when
an early prokaryote has engulfed a
photosynthetic cyanobacterium
chloroplast are derived from primary endosymbiosis
Secondary
Endosymbiosis
This occurs when a eukaryotic cell engulfs
a cell that has already undergone primary
endosymbiosis.
Scientists believe brown algae evolved
through endosymbiosis of a red alga.
Stramenopiles have chloroplasts with four
membranes, which arose when the first
brown algae engulfed the red algae.
GREEN ALGAE
Significant Attributes
red algae cannot survive in vv unsurvivable place shshags
similar to chloroplast in true plants
Resilient
Aquatic and Terresrial
Have chlorophylls a and b
They have remarkable
developmental and metabolic
plasticity
Primarily aquatic, found in
freshwater and marine habitats;
but also terrestrial, growing on
soil, trees, or rocks
Have no trace of bacterial wall,
but instead have chlorophylls a
and b.
Chlorophyll a absorbs violet and orange light the
most. Chlorophyll b absorbs mostly blue and
yellow light.
6 Evolutionary Possibilities
FROM A MOTILE SINGLE CELL
Motile Colonies
If cells adhere loosely, the
resulting structure is a colony,
where cells are similar and none
is particularly specialized.
Nonmotile Colonies
This occurs when cells lose their
flagella or never develop them.
Nonmotile cell is simpler than
one with flagella.
Filamentous Body
This occurs if cells are held tightly
by a middle lamella and if all cells
divide transversely.
If occasionally cells undergo
longitudinal division, the filament
branches.
Membranous Body
This occurs if the orientation of
cell
divisions
is
controlled
precisely such that all new walls
occur in only two planes,
resulting to a sheet of cells that
can become more extensive but
remains thin.
Parenchymatous
Body
A
bulky,
three-dimensional
parenchymatous body occurs if
cell division occur regularly in all
three planes.
all cells are interconnected by plasmodesmata
Coenocytic or
Siphonous Body
This
occurs
is
karyokinesis
happens without cytokinesis, and
giant multinucleate cells results.
Life Cycles of Green Algae
Definition of Terms:
Mitosis
Meiosis
· cell division where the parent
nucleus and both daughter
nuclei have the same number
and
type
of
chromosomes.
Produces diploid cells.
· cell division that produces four
daughters with half as many
chromosomes as the parent cell
each. Produces haploid cells.
4 haploid cells
Syngamy
· the joining of two cells or their
nuclei for the purpose of
reproduction.
Definition of Terms:
Gametophyte
· the haploid, gamete-producing
stage that results in the zygote
from which the sporophyte arises.
Sporophyte stage of Derbesia
Sporophyte
· the asexual, often diploid phase
that results in the spores from
which the gametophyte arises.
Gametophyte stage of Derbesia
The life cycle of green algae was
modified due to the evolution of sex
on which meiosis segregates out a
haploid set of chromosomes and
syngamy brings two groups back
together.
In general:
Alternation of
Generations
The gametophyte phase produces
gametes from mitotically grown
spores.
Some time, there will be syngamy
of gametes which results in a
diploidic zygote.
At this point, the cycle is now at its
sporophyte phase.
In general:
Alternation of
Generations
The zygote self-grows via mitosis
and produces spores by meiosis
when mature.
And
the
circulate.
cycle
continues
to
Two Types of Life Cycles in Green Algae:
Monobiontic
· a life cycle in which only one
generation (phase) is capable of
undergoing mitosis
In most algae (left), the
haploid cell is dominant and
only one diploid cell occurs.
In a few algae (right), both are
equal and haploid cell acts as
gametes.
1 to none generation formed by this algae
Two Types of Life Cycles in Green Algae:
Dibiontic
· both sporophyte and gametophyte phases
are capable of growth, division, and
reproduction.
Two Types:
Isomorphic
- it is when the gametophyte and
sporophyte resemble each other strongly.
Heteromorphic
- it is when the gametophyte and
sporophyte are very different in appearance
and construction.
Representative Genera of Green Algae
Representative Genera of Green Algae
Unicellular
An example of unicellular algae is
Chlamydomonas.
It
is
one
of
the
simplest
chlorophytes.
Has a nucleus, chloroplasts, and two
alike anterior flagella.
Motile Colonial
Volvox is one example of this
type.
Colonies contain up to 50 000
Chlamydomonas-like cells.
Representative Genera of Green Algae
Filamentous
Genus Ulothrix is the simplest type
of this species.
Has a monobiontic life cycle
Consists of one row of cells that are
similar to each other except for the
basal part.
Free-floating attached to rocks,
debris, or other plants.
Laminar
An example of this species is
Ulva or sea lettuce.
Slightly more complex than the
Ulothrix.
Have quadriflagellated spores
and grows into a ulothrix-like
filament.
Have
dibiontic
life
cycle,
specifically isomorphic.
Representative Genera of Green Algae
Coenocytic
Example of this species are
Derbesia.
They have a dibiontic life cycle
which are heteromorphic.
Gametophyte structure was once
named Halicystis ovalis and was
eliminated after it grew back into
Derbesia.
Parenchymatous
An example of this species is
Chara.
Have a stem-like body divided
into nodes and internodes.
- Seen are wholes of branches
Several cell-thick bodies and are
composed of true parenchyma
tissues from cell division
The Red Algae
Porphyra
(right)
umbilicalis
Chondrus crispus (upper
left)
Gracilaria
(lower left)
salicornia
Constitute a large group of especially distinct and fascinating algae.
Mostly aquatic, with no flagella, and are grouped under the class
Rhodophyceae
The Red
Algae
Their red color is due to the presence of phycoerythrin, chlorophylls a,
and d.
Walls of red algae contain a thick layer of slimy mucilages called
sulfated galactans; lack plasmodesmata.
The Red Algae
Almost all red algae are multicellular; Porphyridium
and Rhodospora are the few known unicellular red
algae.
Palmaria palmata (top)
Corallina
(middle)
officinalis
Laurencia obtusa (below)
·Excess photosynthate is stored as floridean starch.
Largest Family of Red Algae: Corallinacea; used to
be recognized as corals until 1837. They were
classified as corals due to large amounts of calcium
carbonate deposited into their walls that they
become rock-like.
·Red algae are smaller and less complex than other
algae types, yet they can attain little differentiation
or specialization occurs among the cells.
The Red Algae
·Most are parasitic, usually on other red algae- basal cells
penetrate into the host, forming secondary pit connections
with host cells.
·Poorly known life cycles, but are extremely complex based
on those few studied.
· Sessile and thylakoids are unstacked
Plocamium cartilagineum (left)
Delesseria sanguinea (top)
Hynea musciformis (lower middle)
Nitophyllum punctatum (lower right)
Brown Algae and Their
Relatives: Heterokonts
Brown algae are almost exclusively marine;
only a few fresh-water species are known.
Over 1,500 species are known,
grouped into about 250 genera.
They prefer cold water that is very agitated and
aerated.
*(exposed to air)
They can be found most easily on rocky coasts
growing in the littoral zone or intertidal zone.
part of the sea or close to the shore
Brown Algae and Their
Relatives: Heterokonts
Anatomically and morphologically have the most
complex bodies of any algae such as mosses and
liverworts.
Distinct from embryophytes biochemically and
ecologically.
brown - marine, green - freshwater
Both brown and green algae are parallel in terms
of their bodies and life cycle that evolved.
FIGURE 19-26 Fucus is a
common brown alga you might
see on any cool, rocky coast, just
below the high tide level. It
tolerates being exposed to air for
several hours at low tide because
its thick cell walls are extremely
hydrophilic,
slowing
the
evaporation of water.
Features of Brown Algae
Brown algae have chlorophyll a and chlorophyll c
and large amounts of a variety of pigments such as
fucoxanthin, violaxanthin, and diatoxanthin (these
are xanthophyll pigments).
carry out photosynthesis
Membranes of brown algal chloroplasts associate
into grana-like stacks, always small, each consisting
of just two or three membranes.
2 to 20 thylakoids
- The storage product of brown algae is laminarin.
- Cell walls of brown algae contain
cellulose and
alginic acid, an unusual polymer of D-mannuronic
acid and L-guluronic acid not found in
other algae.
starch - green algae
Features of Brown Algae
Algae, especially marine species, live in stable
environment with regard to light, temperature and
nutrients that photosynthesis and growth occur
more or less continuously.
Brown algae that live on seasonal habitats needs an
energy reserve.
A Kelp is an example.
.
All are multicellular.
Diatoms
Easy to recognize because of their distinctive morphology;
Each cell has a wall composed of two halves or frustules that fit
together like a Petri dish and its lid
Diatomaceous earth
Frustules are extremely intricate.
The cells are either round in face view (centric diatoms) or
elongate (pennate diatoms).
Morphology of Diatom
FIGURE
19-30
Pennate
diatoms are elongated and
bilaterally symmetrical. The
numerous
holes
in
their
frustules allow nutrients to
be taken up from seawater
and wastes to be excreted
(×4,500).
Yellow Green
Algae
Occur mostly in fresh water.
Formerly thought as green
algae until chlorophyll C was
discovered in them.
Being
diverse;
some
are
unicellular, some filamentous
and some are forming giant
multinucleate cells.
Yellow Green Algae
Tribonema
Have walls like diatom frustules
Each cell having two half-walls, but each
of these frustule-like walls is firmly
attached to the adjacent half-wall of the
neighboring cell.
Vaucheria
An unusual body that consists of a long
tubular coenocyte with a single large
central vacuole.
A thin peripheral layer of cytoplasm, and
thousands of nuclei
Golden Brown Algae
Consist of about 70 genera and 325
species.
They are single cells covered with
numerous tiny siliceous scales that
develop within special vesicles in the
endoplasmic reticulum.
Cells may be either uniflagellate or
biflagellate
Photoautotrophic that can ingest by
phagocytosis.
FIGURE 19-32 Each cell of a goldenbrown alga is covered with many
minute scales that are formed within
vesicles
of
the
endoplasmic
reticulum.
Coccolithophorids
The living cells float in warm, sunny
surface waters, like diatoms, but
when they die, the lack of
swimming motion allows their
dense siliceous scales or frustules
to sink and accumulate on the
ocean floor as chalk.
The remains of both diatoms and
golden-brown algae, especially a
group known as coccolithopohrids.
Dinoflagellate
Their nuclear envelope and
nucleolus persist throughout mitosis,
and a typical spindle does not form
Characteristics of
Dinoflagellate
There are no histones
Almost exclusively motile and
unicellular.
They differ from heterokonts by not
having a tinsel flagellum
Most species are photosynthetic, but
many are completely heterotrophic.
90% of all dinoflagellates are found living in the ocean.
They are Bioluminescent.
The density of dinoflagellates can
be as high as 30,000 cells per
milliliter of sea water.
Red tides are becoming
increasingly frequent in the Gulf of
Mexico
These algae produce toxins, and
their large concentrations kill fish
and make other marine life
poisonous to humans.
For instance, Gonyaulax catenella
are potent neurotoxins.
Oomycetes
They have no chloroplasts.
Like
fungi,
they
are
never
photosynthetic.
Their bodies that consist of long,
slender multinucleate, coenocytic
tubes that have no cross walls, an
organization typical of fungi.
Their characters are more like those
of algae and plants but different from
true fungi.
They must be parasitic or saprophytic
Euglenoids
More than 800 species of euglenoids have
been discovered and placed into 36
genera.
Most euglenoids are unicellular, but in
some species, a few cells remain together
after cell division.
Euglenoids swim actively with two flagella
located at the cell’s anterior end.
They never have cellulose wall, instead
they have periplast.
Thank you!
Group 1:
Galacio, Marc Alexis
Jayona, Jayla
Rejas, Maryquinn
Virtudez, Samantha Nicole