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 asexual & sexual 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 for green algae
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 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
GROUPS OF ALGAE CLASSIFIED ACCORDING TO TYPES OF CHLOROPHYL & ACCESORY PIGMENTS THEY HAVE
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.