Multicellular Algae

1. Multicellular Algae Kingdom Protista Developed by Adam F Sprague & Dave Werner

2. Characteristics of Algae: • Plantlike members of the kingdom Protista • Eukaryotes • Most unicellular, but some multicellular • Autotrophic – contain chlorophyll & make food by photosynthesis • Planktonic • Produce oxygen • microscopic to seaweeds hundreds of feet in length • Do not have true roots, stems, nor leaves • Form gametes (eggs & sperm) in single-celled gametangia (chambers) instead of multicellular gametangia like true plants • Found in freshwater, marine, and moist soil habitats • Most have flagella at some time in life cycle • Algae cells contain organelles called pyrenoids organelles that make & store starch

3. Structure of Algal Cells: • The body of algae is called the thallus  • Algae may  be unicellular, colonial, filamentous, or multicellular • Unicellular algae are single-celled & make up phytoplankton (a population of photosynthetic organisms that begins many aquatic food chains) • Phytoplankton make much world's carbohydrates & are the major producers of oxygen

4. Structure of Seaweeds • Filamentous algae have slender, rod-shaped thallus arranged in rows joined end-to-end • Holdfasts are specialized structures in some filamentous algae that attaches the algae so it can grow toward sunlight at the surface

5. Structure of Seaweeds: • Multicellular algae often have a large, complex leaf-like thallus & may have stem-like sections and air bladders called pneumatocysts • Macrocystis is among the largest multicellular algae

6. Structure of algae vs. seagrass

7. Filamentous algaeEnteromorpha

8. Multicellular algaeMacrocystis

9. Classification: • Algae are classified into 3 phyla, based on color, type of chlorophyll, form of food-storage substance, and cell wall composition • All phyla contain chlorophyll a • Many species of algae reproduce sexually and asexually • Sexual reproduction in algae is often triggered by environmental stress

10. Chlorophyta (green Algae): 7000 species • May be unicellular, multicellular, or colonial • Include Spirogyra, Ulva, & Chlamydomonas • Contain chlorophyll a & chlorophyll b and carotenoids (orange & yellow pigments) as accessory pigments • Store food as starch • Cell = cellulose, some add CaCO3 • Habitat -freshwater, moist surfaces, or marine environments • Some have whip-like flagella for movement • May live symbiotically as lichens • Thought to have given rise to terrestrial plants

12. Phaeophyta (brown algae): 1500 species • Contain chlorophyll a & chlorophyll c and fucoxanthin (brown pigment) as accessory pigments • Most multicellular- growing in cooler marine habitats • Includes kelps & seaweeds • Largest protists • Specialized rootlike holdfasts • Specialized air bladders • Stemlike structures are called the stipe • Store food as a carbohydrate called laminarin • Include Laminaria & Fucus

14. Rhodophyta (red algae):4000 species • Multicellular algae that mainly grow deep in warm marine waters • Some freshwater species exist • Highly branched thallus • Contain chlorophyll a & phycobilins (red pigments) to trap sunlight • Store food as starch • Cell walls contain cellulose and agar (used as a base in culture dishes to grow microbes) • Some species contain carageenan in their cell walls used for gelatin capsules & in some cheeses

16. Common Marine algae of Barnegat Bay

17. Enteromorpha

18. Ulva lactuca(Sea Lettuce)

19. Agardhiella

20. Fucus(rockweed)

21. spongomorpha

22. Sargassum A closeup of a small mass of sargassum weed. The numerous small round spheres are floats filled with carbon dioxide. These provide buoyancy to the algae.

23. There are numerous types of marine algae found throughout our back bay areas, this has just been a sample of what you will find.

24. Diatom Reproductionfig. 5.6 Asexual = Cell Division into Auxospores • Produces Blooms Sexual = Egg & Sperm

25. Reproduction in Unicellular AlgaeBio book p.528 Asexual Phase • Algae absorbs its flagellum • Haploid algal cell then divides mitotically from 2 to 3 times • From 4 - 8  haploid flagellated cells called zoospores develop in this parent cell • Zoospores break out of the parent cell & eventually grow to full size

26. Sexual Phase • Haploid cells dividing mitotically to produce either “plus” or “minus” gametes • A plus gamete and a minus gamete come into contact with one another, shed their cell walls, and fuse to form a diploid zygote • This resting stage of a zygote is called a zygospore & can withstand bad environmental conditions • When conditions are bad, the thick wall opens and the living zoospore emerges

27. Chlamydomonas

28. Reproduction in Multicellular Algae: • Oedogonium is a multicellular, filamentous green algae with specialized cells called gametangia that form gametes • The male gametangia or antheridium makes sperm, & the female gametangia or oogonium makes eggs • Sperm are released into the water & swim to the egg to fertilize them • The fertilized egg or zygote is released from the oogonium & forms thick-walled zoospores • Zoospores undergo meiosis so one cell attaches to the bottom & develops a holdfast while the other zoospores divide & form a filament

30. Spirogyra, another filamentous green algae, reproduces by conjugation

31. Two filaments align side by side, their adjacent cell walls dissolve, & a conjugation tube forms between themFertilization occurs when a + gamete cell moves through the tube & fuses to the - gamete cell Zygote forms a thick walled spore (sporangium) that breaks away from the parent & forms a new filamentConjugation Tube between Spirogyra

32. Ulva fig.6.11 • The leaflike algae Ulva has a sexual reproductive cycle characterized by a pattern called alternation of generations •  Alternation of generations has two distinct multicellular phases- a haploid, gamete-producing phase called a gametophyte and a diploid, spore-producing phase called a sporophyte • Alternation of Generation also occurs in more complex land plants, but the gametophyte & sporophyte do not resemble each other