ALGAE
By Erica Gonzales
What are algae?

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Protists that use
photosynthesis
Classified by their
pigments:
Purple,
 Rusty-red,
 Olive-brown,
 Yellow,
 Golden Brown


Both unicellular and
multicellular
Characteristics
Unicellular Algae



Phytoplankton
Major producer of
nutrients and oxygen
in the world
Classified into 3 phyla:
 Euglenoids
 Diatoms
 Dinoflagellates
Multicellular Algae



Look like plants
No roots, stem or
leaves
Large and Green
Unicellular Algae
Euglenoids
• Diatoms
• Dinoflagellates
•
Euglenoids


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Unicellular aquatic protists
Plant AND animal characteristics
Made of cellulose; no cell wall
Have flagella to move towards
light or food
Have a flexible pellicle around
cell membrane
Parts of a Euglenoid
Notice that there are similarities between the Euglenoid
and a plant cell
Characteristics
Plant-Like


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Contain chlorophyll
Conduct photosynthesis
Autotrophic
Animal-Like

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Can eat food when
light is not available
Ingest food like
protozoa
Heterotrophic
Diatoms



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Unicellular photosynthetic
organisms
Have shells composed of silica
Abundant in fresh and
saltwater ecosystems
Box-shaped
Contain chlorophyll and
carotenoids (a pigment) for
golden color
Diatom Shells
Each
species of
diatoms
has its own
unique
shape,
differently
patterned
with
grooves
and pores.
Food




Use sunlight for food (photosynthesis)
Food is stored as oils, not starch
Gives them an oily taste to fish that eat them
Oil allows them to float near water’s surface for
sunlight
Reproduction
Asexually

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Two halves of the box split
Each pieces produces a
bottom half to fit inside it
Half of offspring are
smaller than parents
Stops when diatoms are ¼
original size
Then switches to sexual
reproduction
Sexually



Produce gametes (egg or
sperm)
Fuse to form zygotes
Zygote fully develops and
divides asexually for a
while
Diatom Reproduction
Death

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Shells sink to ocean
floor at death
Million-year-old
diatom deposits have
been found
Used for tooth or
metal polishes
Dinoflagellates

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Have cell walls made of thick cellulose plates
Contain chlorophyll, carotenoids & red pigments
2 flagella in grooves right angles to each other
Live in freshwater, but mostly saltwater
Can live symbiotically with jellyfish, mollusks and
coral
Some species emit light
Toxic Dinoflagellates

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Several species produce toxins
One species Pfiesteria piscicida can cause massive
fish kills
Gonyaulax catanella produces extremely lethal
nerve toxins
A
very numerous population of these cause a red tide
 Inhabited by 40 to 60 million dinoflagellates per liter
of seawater
 Can make humans ill
Red Tides
The yellow
and orange
spots in the
water are
red tides,
areas so
densely
infested by
toxic dinoflagellates.
Multicellular Algae
Red Algae
• Brown Algae
• Green Algae
•
Red Algae
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Multicellular marine seaweeds
Thallus – body of a seaweed: lacks roots, stem
and leaves
Uses structure called holdfasts to attach to rocks
Found in tropical waters or in cold waters on
rocky coastlines
Pigments

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Contain Chlorophyll and
phycobilins –
photosynthetic pigments
that absorb green, violet,
and blue light (the only
lights that penetrate water
past 100 meters)
Allows algae to deeper
than most seaweeds
Brown Algae
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Live in salt water along rocky
coasts in cooler areas
Contain chlorophyll and
fucoxanthin
Fucoxanthin – yellowish-brown
carotenoid (a pigment) that
gives them their brown color
Most species have air bladders
 Keep
them floating near the
surface for sunlight
Kelp
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Largest and most complex
brown algae
Thallus (body) is divided into
holdfast, stripe and blade
Holdfasts anchor them to
rocks or ocean floor
May grow to 60 meters long
Some giant kelps form
underwater forests
 Many
organisms live in them
Green Algae

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Most diverse algae; over
7000 species
Have many pigments
that give yellow-green
color
 Main

one is chlorophyll
Live in: freshwater,
saltwater, moist soil, tree
trunks, even the fur of
sloths
Unicellular
Multicellular
Colonies
Different Types of Green Algae
Colony: group of cells that lives together in close
association
Volvox Colony

Composed of hundreds of cells with flagella in one
layer to form a hollow ball
 Cells
are connected by strands of cytoplasm
 Flagella face outwards and beat in unison to spin the
colony in the water

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Smaller balls, “daughter colonies” form inside the
hollow space
Wall of larger colony eventually breaks to release
the daughter colonies
Reproduction
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Reproduce sexually AND asexually
Fragmentation – (asexual reproduction) an
individual breaks up into pieces and each piece
grows into a new individual
 Some

species use this method of asexual reproduction
Alternate from producing sexually and asexually
throughout lifecycle
 Produce
gametes for sexual reproduction
 Produce spores for asexual reproduction
Alternation of Generations
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Pattern of alternating between existing as a haploid
and diploid organism, creating 2 different
generations
Gametophyte – haploid form of organism; produces
gametes
 They

fuse to form a zygote
Sporophyte – diploid form of organism, also zygote
of previous generation; produces spores
 Cells
undergo meiosis and eventually become haploid
spores that can become gametophyte
Life Cycle of Green Algae
Throughout their lives, green algae switch from being a
diploid to a haploid.