BIOLOGY 11
ALGAE
General Characteristics:
 photosynthetic autotrophs
 organism that uses CO2 as the only or main source of carbon
 multicellular (usually)
 producers of food energy and oxygen
 cell walls of cellulose
 demonstrate alternation of generations
Classification of Kingdom Plantae
Alternation of Generation
 life cycle in which there are two vegetative forms that each plant has; these forms alternate and
each produces the other
 Sporophyte
 Diploid generation (2n)
 Stage that produces spores by meiosis
 Spore then undergoes mitosis to produce the gametophyte
 Gametophyte
 Haploid generation (n)
 Stage that produces the gametes (egg and sperm) by mitosis
 Sperm and egg fuse, then undergoes mitosis to produce the sporophyte
 depending on the type of plant, either the sporophyte or gametophyte form is dominant
 simple plants  gametophyte generation is dominant
 tracheophytes  sporophyte generation is dominant
Simple Plants
 aquatic or highly water dependant (e.g. require water for sperm to reach the egg)
 lack vascular tissue (xylem and phloem)
 therefore lack true roots, stems, and leaves
Algae
 a general term that refers to a group of organism that have some similarities but transcend the
kingdoms Protista, Monera, and Plantae
 algae are aquatic, (usually) multicellular, have thin tissues which allow nutrients to diffuse in and
wastes to diffuse out
 algae also often demonstrate alternation of generations and contain chlorophyll a
Phyla of algae
There are three phyla of multicellular algae that are classified based upon their types of pigments and
food storage.
1. Green Algae (chlorophyta)
 contain chlorophyll a and b
 food is stored as starch
 can occur as a single cell, as a colony, or as a multicellular organism

examples: chlamydomonas (unicellular)
volvox (colonial)
spirogyra (filamentous)
ulva (sea lettuce) (multicellular)
2. Phaeophyta (Brown Algae)
 marine plants (e.g. the sea weeds kelp, fucus, and Sargassum)
 have complicated specialized tissues which make up root-like structures called holdfasts, stemlike structures called stipes, and leaf-like structures called blades
3. Rhodophyta (Red Algae)
 a marine algae many of which may grow at extreme depths because they trap light that can
penetrate deeper into the water; this is due to the accessory pigments that trap this light energy
and pass it onto the chlorophyll molecule
 example: Porphyra (nori)
Importance of algae
 between 50 and 75 percent of the Earth's photosynthesis is estimated to be done by algae
 therefore they are important because they are producers of oxygen and food
 used as medicines for stomach ulcers high blood pressure and arthritis
 rich in vitamin C and iron
 there are numerous commercial uses including:
 manufacture of paper and textiles
 waterproofing and fireproofing fabrics
 thickening drinks, ice cream, cosmetics, jellies and soups
 medical industry (burn dressings, detoxify metals from blood, prosthetic casting)
 appetite suppressant
 food source
 pollution control
 fertilizer
 natural pigments for dyes
Reproduction in algae
Diagram of the Chlamydomonas Life Cycle
Diagram of the Ulva Life Cycle