Plantlike Protists: Red, Green, and Brown Algae Ch. 20-4 Notes Plantlike Protists: Red, Green, and Brown Algae

Red Algae Members of the phylum Rhodophyta, meaning “red plants”. 1. Able to live at great depths due to their efficiency in harvesting light energy. 2. Contain chlorophyll a and reddish accessory pigments called phycobilins. Phycobilins- Accessory pigment found in red algae that is especially good at absorbing blue light. Many red algae are actually green, purple, or reddish black. Are multicellular with complex life cycles They also lack flagella, and centrioles.

Brown Algae Members of the phylum Phaeophyta, meaning “dusky plants”. 1. Contain chlorophyll a and c and a brown accessory pigment called fucoxanthin. - The combination of fucoxanthin and chlorophyll c gives most of these algae a dark, yellow-brown color. Largest and most complex of the algae. Brown algae are multicellular and mostly are marine The body of algae consists of flattened stemlike structures called stipes, leaflike structures called blades, and gas-filled swellings called bladders, which float and keeps the alga upright in the water.

Structures of Brown Algae

Green Algae Members of the phylum chlorophyta, meaning “green plants” in Greek. 1. Share many characteristics with plants, including their photosynthetic pigments and cell wall composition. Contain cellulose in their cell walls, contain chlorophyll a and b, and store food in the form of starch Green algae is found in both fresh and salt water. They can also grow on moist areas of land. Many species of Green algae live their lives as simple, unicellular organisms. Others group together into colonies; and a few even grow into specialized, multicellular structures.

There are three main types of Green Algae: 1. Unicellular Green Algae (Chlamydomonas)- A typical single-celled green alga, grows in ponds, ditches, and wet soil. It is a small egg shaped cell with 2 flagella and a single large, cup-shaped chloroplast. Within the chloroplast is a region that synthesizes and stores starch. Lacks the large vacuoles found in the cell of land plants, instead it has 2 small vacuoles. 2. Multicellular Green Algae (Ulva) – A bright-green marine alga that is commonly found along rocky seacoasts. “Sea Lettuce” is a multicellular organism, containing several specialized cell types. 3. Colonial Green Algae (Spirogyra) – Two Types: Spirogyra -Forms long threadlike colonies called filaments, in which the cells are stacked almost like aluminum cans placed end to end. Volvox - Colonies consist of as few as 500 to as many as 50,000 cells arranged to form hollow spheres. The cells in a Volvox colony are connected to one another by strands of cytoplasm, enabling them to coordinate movement. When the colony moves, cells on one side of the colony “pull” with their flagella, and the cells on the other side of the colony have to “push”.

Reproduction in Green Algae 1. The life cycles of many algae include both a diploid and a haploid generation 2. Alternation of generations- Process in which many algae switch back and forth between haploid and diploid stages of their life cycles. Haploid- A cell containing a single set of chromosomes Diploid- A cell containing a complete set of chromosomes

Reproduction in Chlamydomonas 1. Chlamydomonas spends most of its life in the haploid stage and as long as its living conditions are suitable, this cell reproduces asexually, producing cells called zoospores by mitosis. The 2 haploid daughter cells produced by mitosis are genetically identical to the single haploid cell that entered mitosis. 2. If conditions are unfavorable, Chlamydomonas can also reproduce sexually. The haploid cells continue to undergo mitosis, but instead of releasing zoospores, the cells release gametes. The gametes are of 2 opposite mating types, + (plus) and – (minus). The gametes gather in large groups, then + and – gametes form pairs that soon move away from the group. They soon form a zygote. When conditions are favorable, the zygote begins to grow and divides by meiosis to produce 4 flagellated haploid cells and these haploid cells can swim away, mature, and reproduce asexually.

Chlamydomonas Life Cycle

Reproduction in Ulva 1. The life cycle of Ulva involves an alternation of generations. The haploid and diploid stages of Ulva are extremely similar. In the haploid phase, the Ulva produces a diploid zygote cell, which then grows into a large, diploid multicellular Ulva. The diploid Ulva undergoes meiosis to produce haploid reproductive cells called spores. Each spore is able to grow into a new individual without fusing with another cell. Because the diploid Ulva produces spores, it is known as a sporophyte, or spore-producing organism.

Ulva Life Cycle

Human Uses of Algae Algae can be used for many things including: Medicine Food Sources Manufacturing Scientific Uses

Review!     1. Red Algae contains chlorophyll a and the pigment _________? Chlorophyll b Chlorophyll c Fucoxanthin Phycobilins 2. True or False: Brown algae is the largest and most complex algae. True False

Review! 3. Green algae shares many characteristics with _______? 4. What are the three main types of Green algae? 5. True or False: The life cycle of most algae contain just a diploid generation. A. True B. False Plants 1. Unicellular Green Algae (Chlamydomonas) 2. Multicellular Green Algae (Ulva) 3. Colonial Green Algae (Spirogyra)

Review! 6. Chlamydomonas spends most of its life in the ______ stage. 7. True or False: Ulva produce diploid reproductive cells called spores. True False 8. Algae is used in many processes except ________. Medicine Food Sources Waste Management Scientific Uses Haploid