By Hannah Reagan

1. Chapter 20.4 By Hannah Reagan

2. Red Algae • Phylum Rhodophyta –means red plants • Able to live in great depths • Chlorophyll a • Phycobilins are reddish accessory pigments, good at absorbing blue light • Can be red, green, purple, or reddish black • Grow anywhere from the ocean surface to depths of 260 meters • Multicellular with complex life cycles • No flagella or centrioles • Help maintain equilibrium in the aquatic ecosystem by supplying nutrients through photosynthesis that promote coral animals • Coralline red algae provide calcium carbohydrate that helps to stabilize the maturing of the coral reef

3. Brown Algae • Phylum Phaeophyta-meaning dusky plants • Chlorophyll a and c • Have brown accessory pigment, fucoxanthin and chlorophyll c give it dark throw-up color • Largest and most complex • Multicellular • Mostly marine found in shallow oceans in temperate or arctic areas • Giant kelp is the largest alga and can grow too 60 meters in length • Common brown algae is Fucus, rockweed, found in our rocky east coast • Holdfast-structure that attaches the algae to the floor, rock, bottom, etc. • Stipes- flattened stem like structure • Blades- leaflike • Bladders- gas-filled swellings that float and keep algae upright

4. Green Algae • Phylum Chlorophytameaning green plants • Photosynthetic pigments and cell wall are similar to a plant’s • Chlorophyll a and b • Contain cellulose in their cell wall • Food is stored as starch • Scientists hypothesize that plant ancestors looked like some present living green algae • Found in fresh and salt water and even moist places on land • Mostly single celled but others form colonies and even a few multicellular • The ones in groups contain similar cells, but show few specialized structures

5. Green • Unicellular Chlamydomonasgrows in ditches, ponds, and wet soil. It is a small egg with two flagella and one large, cup-shaped chloroplast.no on large vacuole, but instead two small contractile vacuoles. • Colonies filaments-long threadlike colonies which cells are stacked end to end. Volvoxlive in fresh water and have 500 to 5,000 cells arranged in hollow spheres connected by cytoplasm. It can move by the cells “pushing” and “pulling.” Has a few gamete-producing cells • Multicellular Ulvais “sea lettuce” because of it’s bright green color. Has many specialized cell types. Lives in marine rocky seacoasts

6. Green Algae Reproduction • Life cycles of many algae include both haploid and diploid generations; switching between haploid and diploid stages is known as alternation of generations • Also often switch back and forth between sexual and asexual reproduction

7. Ex 1. Chlamdomonas • Most of the time is in the haploid stage and reproduces asexually producing cells called zoospores through mitosis • In unfavorable conditions, it reproduces sexually and releases gametes instead of zoospores • Negative and positive identical gametes pair up and fuse together to form one diploid zygote • Has a brief diploid stage when it is a zygote and during the rest of the cycle, the algae is going through the haploid stage

9. Ex 2. Ulva • Involves alteration of generations too • During haploid stage of this reproduction, male and female gametes are known as gametophytes (gamete-producing plants) • Male and female gametes fuse to make one diploid zygote cell, similar to Chlamdomonas • After that, the diploid Ulva goes through meiosis to produce haploid reproductive cells called spores • This spore-producing organism is known as a sporophyte • Each spore manufactured is able to grow to become a new individual without fusing with another cell

11. Similarities Between Algae • Can be multicellular (green can form colonies or be single celled) • Rarely form fossils • Found in water

12. Human Uses of Algae • Food • Produces much of our oxygen • Can be used to treat stomach ulcers, high blood pressure, arthritis, and other health problems • Contains a lot of vitamin C and iron • Chemicals from algae are used in making plastics, waxes, transistors, deodorants, paints, etc. • Used in scientific laboratories: agar is derived from seaweeds and is used to grow bacteria as we know 