Types of Life Cycle in Algae
What is a Life Cycle?
Alternation of Generations
www.bio.miami.edu
Isogamy
Wikipedia
Anisogamy
Wikipedia
Oogamy
Wikipedia
The Life Cycle of Chlamydomonas,
a green alga
Isogamy
The Life Cycle of Ulva, a green
alga
Isogamy; Isomorphic
www.resnet.wm.edu
The sporangial and gametangial thalli are
morphologically alike; they are called Sporophytes and
Gametophytes, respectively. The diploid adult plant
(sporophyte) produces haploid spores by meiosis
that settle and grow on a substrate to form haploid
male and female plants (gametophytes)
morphologically similar to the diploid sporophytes.
Gametes produced by mature haploid “+” and “–”
gametophytes fuse, through fertilization, to produce
zygotes which germinate, and grow to produce
diploid sporophytes.
The Life Cycle of Laminaria, a
brown alga
www.resnet.wm.edu
The Life Cycle of Polysiphonia, a
red alga
Anisogamy
www.resnet.wm.edu
DIATOMS
Characteristics of Cyanophyta, Chlorophyta,
Phaeophyta and Rhodophyta
Economic Importance of Algae
The Chlorophyta
The Green Algae are mostly (i) photosynthetic
organisms that contain chlorophylls a and b, (ii)
they store their photosynthetic products as starch
inside their double-membrane-bounded
chloroplasts in which it is produced, and (iii) have
cell walls made of cellulose
They are mostly freshwater, marine and terrestrial,
with unicellular and colonial forms that are mostly
biflagellated. There are also filamentous forms and
macroscopic seaweeds. There are about 7,000
species of green algae.
From the order Charales of the
Division Charophyta of the Green
Algae, the land plants evolved!!!
General Characteristics of the Chlorophyta
1. Major pigments are chlorophyll a and b found
in chloroplast, as well as accessory pigments β-
Carotene and Xanthophyll.
2. Stored food is starch
3. There are apical flagella present
4. Cell wall is made of cellulose
The Rhodophyta
The Red Algae (Rhodophyta) are distinct because
they uniquely characterized by (i) photosynthetic
accessory pigments namely, Phycoerythrin, phycocyanin
and allophycocyanin that are arranged in
phycobilisomes, and (ii) the absence of flagella and
centrioles.
They are mostly marine algae of about 670 genera,
with between 2500 and 6000 species, found mostly
along tropical, temperate and cold water regions of
major continental shelf areas.
Ecologically, they’re very significant in the
following ways: (i) they are primary producers, (ii)
They serve as primary structural habitats for other
marine organisms, and (iii) they play important
roles in the establishment and maintenance of
coral reefs.
Economically, they serve as food and gels, for
which reason the red algae are extensively farmed
and naturally harvested around the world.
www.tolweb.org
General Characteristics of the Rhodophyta
There is absence of flagella and centrioles
They contain phycoerythrin, phycocyanin, and
allophycocyanin as accessory pigments
There is no chloroplast endoplasmic reticulum
Floridean starch as a storage product and the
storage of starch in the cytoplasm
C = Chloroplast
S = Starch
Presence of
unstacked thylakoids
in plastids
unstacked photosynthetic lamellae
Granules, called Phycobilisomes
The Phaeophyta
Saccharina latissima
The Brown Algae (Phaeophyta) are a large group of
mostly marine, benthic algae. They are
multicellular, macroalgae that may reach 60 m in
length. There are between 1500 – 2000 species of
the brown algae.
General Characteristics of the Phaeophyta
Read about this as an independent study!
Economic Importance of Algae
Algae play important roles on earth,
ecologically and economically.
To begin with, algae produce almost 50%
of the Earth’s Oxygen
• They serve as food
• They are used in Food,
Pharmaceutecal, Oil and
Manufacturing industry
• They play important role in
environmental bioremediation
• They are actively involved in nitrogen-
fixation
Algae as Food
Marine algae are used for food in Asia
(also called the Orients) as vegetable in
preparing salad and soup
They are rich in vitamin B and C,
Carbohydrate, and Minerals
They have between 20 – 30% protein
content
Algae as Food
www.guardian.co.uk
Because of their rich nutrient content,
and high Nitrogen content, algae are
used as manure by farmers along many
coastal regions around the world
Algae as Industrial Player
Brown algae produce Alginic acid which is used
extensively in industries - Food,
Pharmaceutical, Chemical, Textiles and
Cosmetics – as polishing agent, as an
emulsifier, a thickener, as an impression
material in dentistry, and in toothpaste,
ointments, fabrics, etc.
Algae are important also to industrially produce
agar, which is used as follows:
• The preparation of microbial culture/growth
media for microbiological research
• Jelling agent to thicken jellies, sauces, ice creams,
canning fish and meat, and in the cosmetics
industry to stiffen creams, soap, shoe polish.
• Algae are also used for blood clotting
Fungus culture, Penicillium sp (left) and bacteria culture
(right) growing on agar media
Yafetto Yafetto
Algae are useful agent of Nitrogen-fixation, a
process by which atmospheric nitrogen (N2) is
converted into Ammonia (NH3), to produce
biofertilizers
