Characteristics Of Eukaryotic Algae
Eukaryotic Algae
I. General Characteristics
II. Reproduction and Life History Patterns
III. Photosynthetic Pigments
IV. Chloroplast types
V. Major Polysaccharide Reserves
VI. Flagellated stages and Flagella types
• true nucleus
• well developed organelles
mitochondria
chloroplasts - surrounded by 2 or 3+
membranes
• more complex reproductive cycles
asexual reproductive spores
sexual reproduction
Sexual Reproduction
Reproduction
Two steps in sexual reproduction:
1. meiosis (reduction division)
2. syngamy (fusion of sex cells)
Asexual
1. mitosis (cell division)
2. zoospores (flagellated)
3. Fragmentation (filaments)
Zygote - diploid cell resulting from
gamete fusion
Three Basic Life History patterns:
differ in when and where meiosis occurs
Diplontic
(2n thallus)
Haplontic
(zygote)
Haplontic life History
Sexual (production of gametes)
Gametes - types:
• isogamous (gametes
identical, flagellated)
+
-
gametes
• vegetative phase
is haploid (thallus)
mi
(n)
• anisogamous
• zygote only
diploid cell
(2n)
zygote
(gametes differ in size,
flagellated)
• oogamous (flagellated
sperm and nonflagellated egg)
Diplohaplontic
(sporophyte)
• meiosis occurs in
zygote
(zygotic meiosis)
meiosis
(n)
zoospores
1
gametes
Diplontic Life History
• vegetative phase
in diploid (2n)
meiosis
Volvox aureus
(2n)
Spirogyra
(2n)
Hydrodictyon
reticulatum
zygote
mitosis
Diplohaplontic Life History
gametes
• meiosis in (2n) thallus
sporophyte
(sporic meiosis)
mi
zy (2n)
mi
(n)
(2n)
me
zoospores
Fucus gardneri
(gametic meiosis)
• gametes are only
haploid stage
Chara excelsa
(n)
• meiosis occurs
in diploid
thallus
• gametes produced
by mitosis
• zoospores grow into
(n) thallus
(gametophyte)
Alternation of
Generations
Some General Distinguishing Features
photosynthetic pigments
Chl a - all have
Chl b – Green, some Cyanobacteria
Chl c1, c2, c3 - found in Brown Algae
(Ochrophyta), Dinophyta,
Cryptophyta & Haptophyta
carotenoids - excess energy
dissipation? Xanthophyll cycle
Ulva fenestra
Antithammnion occidentale
2
1.0
0.8
chlb
chla
abs
0.6
carotenoids
0.4
0.2
400
500
600
700
Wavelength (nm)
Carotenoids cont.
ca. 60 different carotenoids
fucoxanthin
major carotenoids:
• β-carotene – major yellow pigment in
ochrophytes
• fucoxanthin e.g. Browns
• peridinin e.g. Dinoflagellates
• siphoxanthin e.g. Greens
(light absorption in deep water?)
siphonoxanthin
peridinin
phycobilins (Phycobiliprotiens)
Cyanobacteria and Red Algae (Rhodophyta)
C
hl
a
&
1.0
0.8
abs
• phycobiliproteins are a phycobilin
(pigment) and associated protein
• water soluble
• organized in phycobilisomes
ca
ro
te
n
oi
ds
More photosynthetic pigments
0.6
in
n
hr
n
ni
yt
ni
r
ya
e
c
ya
o
o
c
c
o
y
yc
yc
ph
ph
ph
o
l
al
0.4
0.2
400
500
600
700
Wavelength (nm)
3
Model of a Phycobilisome
Energy Transfer Sequence
4 types of
Phycobiliproteins
Chl a
phycocyanin
phycoerythrin
(555-636 nm)
(545-575 nm)
green
1. Phycoerythrin
4. Allophycocyanin
2. Phycoerythrocyanin
thylakiod
red
3. Phycocyanin
chloroplast structure
allophycocyanin
(650-660 nm)
chloroplast origin
number
varies (one in
Chlamydomonas to many)
shape
•
•
•
•
disk shaped (most)
star shaped (Zygnema)
spiral (Spirogyra)
reticulate (Microspora)
1° endosymbiont
position
• parietal
• axial
• central
chlorophyte 1°
2° endosymbiont
cryptomonad 2°
Polysaccharide Reserves
polysaccharide reserves - glucose
chains (Glucans), side branching
varies between groups and
species
– two basic groups
rhodophyte 1°
chromophyte 2°
(ochrophyte)
α-1,4 linked glucose
β-1,3 linked glucose
4
Some Storage Products
α-1,4 linked glucose (starch)
α-1,4 linked
glucose
β-1,3 linked
glucose
• Starch
• Cyanophytan starch (glycogen)
• Floridean starch
• paramylon
• chyrsolaminaran
• lipids
β-1,3 linked glucose (laminaran)
flagella
9+2 organization (eukaryotic,
however no prokaryotic algae are
flagellated)
no flagellated cells in the Rhodophyta
• number of flagella
• position (anterior, posterior,
transverse)
Flagellar Appendages
• smooth (fine hairs) “whiplash”
• tinsel (stiff hairs - mastigonemes)
Flagallated Cell Types
• isokontous – flagella identical in
shape and structure
• heterokontous - (two unequal
length flagella usually one smooth
one tinsel)
isokont
heterokont
5