AQUATIC ANCESTORS OF LAND PLANTS
DISTINGUISHING CHARACTERISTICS:
Photosynthetic
 Live in aqueous environments (ie. In or near water)
 Lack internal tubes to move water and materials
from one part of the plant to another
 Unicellular or multicellular
 Cells have a cell wall
 Contain chlorophyll a (sometimes other forms of
chlorophyll also)
 Complicated alternating sporophyte &
Gametophyte reproduction cycles

WHAT KINGDOM ARE THEY?
Unicellular
algae = Kingdom Protista
Multicellular algae = Kingdom Plantae
PRO’S & CON’S OF AN AQUATIC ENVIRONMENT
Pros

don’t need protection from drying out
 can
have very thin leaf-like structures
 these
thin structures can exchange O2, CO2, & nutrients
directly with the H2O
 no specialized tissues for carrying
2. don’t need stem-like structures for
support

3. reproductive cells can swim through water

Cons

water absorbs much of the suns energy that
chlorophyll needs as it passes through it
 particularly,
sea water absorbs large amounts of red and
violet wavelengths
ACTION SPECTRA = THE RATE OF A
PHYSIOLOGICAL ACTIVITY PLOTTED AGAINST
WAVELENGTH OF LIGHT.




1881, the German plant physiologist T. W. Engelmann
placed a filamentous green alga under the microscope and
illuminated it with a tiny spectrum of visible light.
In the medium surrounding the strands were motile, aerobic
bacteria.
After a few minutes, the bacteria had congregated around
the portions of the filament illuminated by red and blue light.
Assuming that the bacteria were congregating in regions
where oxygen was being evolved in photosynthesis,
Engelmann concluded that red and blue light are the most
effective colors for photosynthesis.
With modern instruments, a plot of the rate of photosynthesis
as a function of wavelength of light produces a graph like this.
More precise than Engelmann's but telling the same story .

because sea water absorbs most of the red &
violet wavelengths, the deeper you get, the
dimmer and bluer the light gets

dim blue light contains very little energy that
chlorophyll a can use
GOOD NEWS!

Algae has evolved two mechanisms to help
 Additional
types of chlorophyll
 Chlorophyll
b
 Chlorophyll c
 Chlorophyll d
 Accessory
 Absorb
pigments
different wavelength of light than chlorophyll and
pass the energy they absorb on for photosynthesis
 Reflect different wavelengths of light than chlorophyll 
wide range of algae color
ASSIGNMENT

1. Write a paragraph explaining how the following
adaptations contribute to the survival of algae in
water and might not contribute to the survival of
algae on dry land





Thin leaf like structures
No waterproof covering
No stem like structures
No system of internal tubes
2. Write a paragraph explaining the restriction that
aquatic life places on algae’s photosynthetic
ability, the proof of this theory, and the
adaptations it has resulted in
CLASSIFIED ACCORDING TO TYPES OF CHLOROPHYL &
ACCESORY PIGMENTS THEY HAVE
GROUPS OF ALGAE
UNICELLULAR PROTISTA

Colonies: Assemblage of individual cells
with variable or constant number of cells
that remain constant throughout the
colony life

Coenobium: Colony with constant
number of cells, which cannot survive
alone; specific „tasks“ among groups of
cells is common
FILAMENTS: DAUGHTER CELLS REMAIN
ATTACHED AFTER CELL DIVISION AND FORM A
CELL CHAIN; ADJACENT CELLS SHARE CELL
WALL
PLANT EVOLUTION
•Single
Celled – Chlamydomonas
•Colonial
– Volvox
•Multicellular
– Ulva
GREEN ALGAE = PHYLUM CHLOROPHYTA
CONTAIN CHOROPHYLLS a
&b
 STORE FOOD AS STARCH
 Believed to give rise to
land plants
 Found in shallow water

BROWN ALGAE = PHYLUM PHAEOPHYTA
CONTAIN CHLOROPHYLLS a & c
 ALSO CONTAIN ACCESORY PIGMENT

RED ALGAE = PHYLUM RHODOPHYTA
CONTAIN CHOROPHYLL a & sometimes d
 ALSO HAVE ACCESORY PIGMENTS
 LIVE DEEPER IN THE OCEANS BECAUSE IS
VERY EFFICIENT AT ABSORBING BLUE LIGHT

ALGAE USES


Algae, the major food of fish (and thus indirectly of many other
animals), are a keystone in the aquatic food chain of life; they
are the primary producers of the food that provides the energy
to power the whole system.
They are also important to aquatic life in their capacity to
supply oxygen through photosynthesis.
MORE USES



Seaweeds, e.g., the kelps and
the red algae (nori), have long
been used as a source of
food, especially in Asia.
Kelp are also much used as
fertilizer, and kelp ash is used
industrially for its potassium
and sodium salts.
agar and carrageen, used as a
stabilizer in foods, cosmetics,
and paints.