Multicellular Algae

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Multicellular Algae

• Kingdom Protista
• Developed by Adam F Sprague
• Dave Werner

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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

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 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

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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

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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

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Structure of algae vs. seagrass
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Filamentous algae Enteromorpha
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Multicellular algae Macrocystis
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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

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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

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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

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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
  

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Common Marine algae of Barnegat Bay
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Enteromorpha
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Ulva lactuca(Sea Lettuce)
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Agardhiella
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Fucus(rockweed)
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spongomorpha
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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.
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There are numerous types of marine algae found
throughout our back bay areas, this has just been
a sample of what you will find.
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Diatom Reproductionfig. 5.6

• Asexual Cell Division into Auxospores
• Produces Blooms
• Sexual Egg Sperm

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Reproduction in Unicellular Algae Bio 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

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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

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Chlamydomonas
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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

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Spirogyra, another filamentous green algae,
reproduces by conjugation
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Two filaments align side by side, their adjacent
cell walls dissolve, a conjugation tube forms
between them Fertilization 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 filament Conjugation Tube between
Spirogyra
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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

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