 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

 Unicellular algae = Kingdom Protista  Multicellular algae = Kingdom Plantae

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

 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

 Algae has evolved two mechanisms to help  Additional types of chlorophyll  Chlorophyll b  Chlorophyll c  Chlorophyll d  Accessory pigments  Absorb 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

 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

 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

Single Celled – Chlamydomonas Colonial – Volvox Multicellular – Ulva

 CONTAIN CHOROPHYLLS a & b  STORE FOOD AS STARCH  Believed to give rise to land plants  Found in shallow water

 CONTAIN CHLOROPHYLLS a & c  ALSO CONTAIN ACCESORY PIGMENT

 CONTAIN CHOROPHYLL a & sometimes d  ALSO HAVE ACCESORY PIGMENTS  LIVE DEEPER IN THE OCEANS BECAUSE IS VERY EFFICIENT AT ABSORBING BLUE LIGHT

 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.

 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. agar