Biological Foundations 112, Lecture 22

Algae (Kingdom Protista)

Chapter 26, pages 532-541
Basic Botany-1 4:22-19:26
Five Kindgoms-3 0:00-19:45

I.   Alternation of Generations

II.  Characteristics of Kingdom Protista

      A.   Eukaryotic cells

      B.   About 200,000 extant and extinct species

      C.   Structure

             1.   Size varies from single cells to the giant brown algae that is up to 200 feet long

             2.   Most are microscopic and single-celled

             3.   Some are colonial

             4.   Some are filamentous

             5.   Some are coenocytic (multinucleated)

      D.   All metabolic processes must be carried on within one cell not different cells as in          
             multicellular organisms

      E.   Methods of obtaining nutrients

            1.   Autotrophic species contain chlorophyll and photosynthesize like plants

            2.   Heterotrophic species obtain food by digestion and then absorption of the substrate

            3.   Some species can be both autotrophic and heterotrophic depending upon                

            4.   Most have aerobic respiration, utilizing mitochondria

      F.   Living arrangements

            1.   Some single-celled

            2.   Some colonial

            3.   Some filamentous

            4.   Some symbiotic with other organisms

                  a.   Mutualism - one end of the spectrum where both organisms that live together    

                  b.   Parasitism - the other end of the spectrum where one living organism absorbs  
                                             nourishment from the other at the latter organism's expense            
                                            (can be pathogenic)

            5.   Most are aquatic or marine and are part of the plankton

            6.   Terrestrial forms are in damp to wet places

      G.   Reproduction

             1.   All reproduce asexually

             2.   Many reproduce sexually with syngamy (union of gametes)

             3.   Most do not develop multicellular sex organs

             4.   None form embryos like higher plants

      H.   Locomotion

             1.   Most are motile at some time in their life cycle

             2.   Methods of movement:

                   a.   Amoeboid motion

                   b.   Flexing individual cells

                   c.   Waving flagella or cilia

                   d.   Many species use two of these motions in the various cells of their life cycle

             3.   Cilia and flagella structure:  9 + 2 arrangement of microtubules (9 outer doublets      
                                                             encircling two single inner microtubules)

III. Division Bacillariophyta - Diatoms

      A.   Structure

             1.   Cell wall

                   a.   Pectin with silica embedded in a very regular pattern

                   b.   No cellulose

                   c.   Contains two valves that surround the cell

             2.   Mostly unicellular

             3.   Some colonial

             4.   Pigments

                   a.   Chlorophyll a and c

                   b.   Carotenes

                   c.   Xanthophylls

             5.   Food reserves

                   a.   Never starch

                   b.   Oil

                   c.   Leucosin - monosaccharide polymer

             6.   Distribution

                   a.   75% of the species are aquatic

                   b.   25% of the species are marine

                   c.   Main component of phytoplankton in both aquatic and marine habitats

      B.   Classification

             1.   Order Centrales - circular in morphology

             2.   Order Pennales - elongate in morphology

      C.   Life-cycle

             1.   Sporophyte generation

                   a.   The visible dominant generation

                   b.   Asexual reproduction of the sporophyte

                         (1)  Nucleus divides

                         (2)  Entire cell increases slightly in diameter

                         (3)  Valves separate

                         (4)  Each daughter cell takes one of the valves with open side bounded by the    
                                cell membrane

                         (5)  Each daughter cell grows a new valve on the open side, inside of the old

                               (a) One daughter cell is the same size as the parent cell

                               (b) Other daughter cell is smaller than the parent cell

                   b.   Meiosis in the sporophyte

                         (1)  Meiosis in Order Pennales

                                (a)  Triggered when a diatom cell reaches a certain critical minimal size or
                                       when certain environmental conditions exist

                                (b)  Each diatom cell that undergoes meiosis will produce 4 isogametes                                                    within the valves of the parent cell

                                (c)  Each isogamete is haploid

                                (d)  Isogametes are gametes that look alike, are the same size, and are

                         (2)   Meiosis in Order Centrales

                                 (a)  Triggered when a diatom cell reaches a certain critical minimal size or
                                        when certain environmental conditions exist

                                 (b)  Each diatom cell that undergoes meiosis will produce either one egg
                                       or four sperms within the valves of the parent cell 

                                 (c)  Each egg and each sperm are haploid

                                 (d)  Eggs and sperms are considered heterogametes because they look      
                                       different and act different

             2.   Gametophyte generation

                   a.   Order Pennales

                         (1)  The valves separate and release the isogametes

                         (2)  The isogametes find each other in the water and conjugate (fuse) to form a  

                         (3)  The zygote is diploid and differentiates into an auxospore

                         (4)  The auxospore is the zygote without valves that grows to full size and then  
                                differentiates into a mature diatom by forming two valves

                   b.   Order Centrales

                         (1)  The egg remains within the valves of the parent cell

                         (2)  The valves of the cells producing sperm separate and the sperm are            
                                released into the water

                         (3)  The sperm find the egg cells by a chemotactic response

                         (4)  The sperm enters the cell with the egg through the girdle band to form a    
                                zygote by fertilization

                         (5)  The valves of the zygote separate releasing the zygote into the water which  
                                differentiates into an auxospore

                         (6)  The auxospore differentiates into a mature diatom by forming two valves

IV. Division Chlorophyta - Green Algae

      A.   Dominant pigment is chlorophyll

      B.   Cell characteristics

             1.   Chloroplasts have unique shapes

             2.   Nucleus is suspended in the central vacuole by strands of cytoplasm

      C.   Some unicellular

      D.   Some filamentous

      E.   Some colonial

      F.   Food reserves

            1.   Starch stored in the pyrenoids

            2.   Some oil

      G.   Both aquatic and marine forms

             1.   Aquatic forms

                   a.   Spirogyra

                   b.   Chlorella

             2.   Marine forms

                   a.   Ulva

                   b.   Codium

V.  Division Rhodophyta - Red Algae

      A.   Pigments

             1.   Chlorophyll a

             2.   Phycocyanin

             3.   Phycoerythrin

      B.   Distribution

             1.   Mostly warm water marine habitats, down to 300 feet deep

             2.   Some (very few, less than 1%) are aquatic

             3.   Some are parasitic on other red algae

      C.   Food Reserves:  Floridean Starch, a starch similar to glycogen where the starch grains
                                      are free in the cytoplasm

      D.   Cell Wall

             1.   Cellulose with pectin embedded

             2.   Other mucilaginous polysaccharides are embedded in the cell wall

                   a.   Have commercial value

                   b.   Agar is one of them that is gelatin-like in nature

                   c.   Carrageenan is one of them that is used as an emulsifier

      E.   Thallus

             1.   Most forms are essentially filamentous where the filaments bind together into            
                   leaf-like structures

             2.   Some forms are unicellular or colonial

             3.   Can be a few inches to six feet long

             4.   No air bladders

      F.   Coraline Algae: secretes calcium carbonate

VI. Division Phaeophyta - Brown Algae

      A.   Pigments

             1.   Chlorophyll a and c

             2.   Carotenoids

             3.   Fucoxanthin - special yellow-brown pigment

      B.   Distribution

             1.   Mostly marine in temperate and polar regions

             2.   Seaweeds of rocky coasts in tidal and shallow subtidal zones to 300 feet deep

             3.   Largest of all the protists

                   a.   Up to 200 feet long

                   b.   Macrocystis

      C.   Cell walls

             1.   Cellulose

             2.   Algin

                   a.   A mucilaginous polysaccharide embedded in the cell wall

                   b.   Cements cell walls together

                   c.   Used as an emulsifier commercially

      D.   Food Reserves

             1.   Laminarin

                   a.   A starch

                   b.   Most abundant of the food reserves

            2.   Mannitol - an alcohol

            3.   Fat droplets

      E.   Thallus structure

             1.   Morphology

                   a.   Holdfast - root-like structure that is used for anchorage

                   b.   Stipe - stem portion of the plant

                   c.   Blade - leafy part

                   d.   Bladders

                         (1)  Usually in the blade

                         (2)  Used for buoyancy

                   e.   Receptacle - the region right around the margin of the blade where the            
                                               reproductive structures are located

             2.   Anatomy of the stipe

                   a.   Epidermis

                   b.   Meristoderm

                         (1)  Just under the epidermis

                         (2)  Cells that remain meristematic and contain chlorophyll

                   c.   Cortical region

                         (1)  Broad region of parenchyma cells

                         (2)  Contain "sieve tube members"

                                (a)  Inner cortex cells

                                (b)  Function like sieve tube members

                                (c)  Structure and function

                                      i)   Contains sieve plates

                                      ii)  Forms callose

                                      iii) Forms continuous tubes

                                      iv) Transports mannitol

                         (3)   Contains no xylem

      F.   Example:  Fucus and its reproductive cycle

            1.   Sporophyte Generation

                  a.   The dominant visible generation

                  b.   No asexual reproduction of this generation

                  c.   Meiosis

                        (1)  Conceptacles are hollow bulbous structures that form within the receptacle 

                        (2)  Haploid gametes are form inside the conceptacles by meiosis

                               (a)  Megasporangia = female gametangia = oogonia

                                      i)   8 eggs form in each oogonium as a result of one meiosis and one      

                                      ii)   Each egg cell is haploid

                                      iii)  Each oogonium is on a stalk cell

                               (b)  Microsporangia = male gametangia = antheridia

                                      i)   Microsporangium produces 4 microspores

                                      ii)  4 microspores under go 4 mitoses to produce 64 sperm cells

                        (3)  Some conceptacles contain both antheridia and oogonia in the same            
                              conceptacle (monoecious)

                        (4)  Other conceptacles contain only antheridia and others contain only oogonia  

                        (5)  Ostiole - opening of the conceptacle

            2.   Gametophyte generation

                   a.   Begins when meiosis is complete in the sporophyte generation

                   b.   Asexual reproduction of the gametophyte generation

                         (1)  Oogonia - after the four megaspores are formed by meiosis they undergo  
                                                 one mitotic division each to make a total of eight eggs

                         (2)  Antheridia - after the 4 microspores are formed by meiosis they; each      
                                                     microspore undergoes four mitotic divisions to produce a      
                                                     total of 64 microspores that mature into 64 sperm cells

                   c.   Fertilization

                         (1)  Eggs and sperms forced into the open water when sea water floods the      

                         (2)  Eggs and sperms unite in the ocean to form a zygote

                         (3)  The diploid zygote develops into a pear-shaped embryo that develops into  
                                a new thallus

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