24Algae

📚
GENERAL FEATURES
▢ Study: Phycology / Algology
▢ Father of Phycology: Fritsch
▢ Terminology:
❖ Term Algae first coined by: Carolus Linnaeus
❖ Term Algae applied to algae by: A. L. de Jussieu
▢ Cell Wall: Cellulose
▢ Reserve Food Material: Starch
📚
HABITAT
▢ General Habitat: Usually aquatic

Table 1: Freshwater and Marine Algae

Feature
Freshwater Algae
Marine Algae
General Size
Generally smaller
Generally larger
Dominant Group
Chlorophyceae
Phaeophyceae
Example
◉ Chlorella — smallest algae:
Image 1
◉ Macrocystis pyrifera — largest algae:
Image 1
▢ Other Substrata:
❖ Endophytic Algae:
◉ Definition: Algae living inside plants
◉ Examples:
◈ Anabaena:
    Image 1
  • •
    Leaf of Azolla
    • ● Azolla:
    • •
      Smallest pteridophyte
    • •
      Leaf used as biofertilizer
  • •
    Coralloid root of Cycas
◈ Nostoc:
    Image 1
  • •
    Mycorrhizal root of Pinus
  • •
    Symbiotic association with Anthoceros
❖ Endozoic Algae:
◉ Definition: Algae living inside animals
◉ Examples: Zoochlorella and Zooxanthella in gastrodermis of Hydra
❖ Cryophytic Algae:
◉ Definition: Algae occurring in snow
◉ Example:
◈ Chlamydomonas nivalis: Causes red snow
◈ Cause of Red Colour: Hypnospores containing haematochrome pigment
Colour Phenomena
❖ Red Sea: Due to blue-green alga Trichodesmium erythraeum
❖ Red Tide: Due to dinoflagellates
📚
REPRODUCTION
▢ Vegetative Reproduction:
❖ Methods:
  • •
    Fragmentation
  • •
    Hormogonium formation in blue-green algae
  • •
    Cell division in unicellular algae
❖ Hormogonium Formation:
◉ Fragmentation Site: Necrotic cell or heterocyst may break the trichome
◉ Hormogonium: Multicellular fragment of a trichome
▢ Asexual Reproduction:
❖ Mechanism: Formation of asexual spores called mitospores

Table 1: Types of Asexual Spores

Feature
Zoospore
Aplanospore
Hypnospore
Akinete
Motility
Motile; flagella present
Non-motile
Non-motile
Non-motile
Wall/Covering
Absent
Thin
Thick
Very thick
Condition
Favourable
Favourable
Unfavourable
Highly unfavourable
Special Role
—
—
—
Perennation
Perennation = survival or conservation from one season to another.
▢ Sexual Reproduction:
❖ Isogamy:
◉ Meaning: Fusion of structurally similar gametes
◉ Example: Spirogyra
❖ Anisogamy: Fusion of dissimilar gametes
❖ Oogamy: Fusion of differentiated male and female gametes produced in reproductive cells
Evolutionary Trend
❖ Isogamy: Most primitive; very low genetic variation
❖ Oogamy: Most advanced; high genetic variation
📚
CLASSIFICATION
▢ Basis:
  • •
    Types of pigments
  • •
    Nature of reserve food material
▢ System: Fritsch divided algae into 11 groups.

Table 1: Major Algal Groups Described

Feature
Cyanophyceae / Myxophyceae / Blue-green algae / Cyanobacteria
Chlorophyceae / Green algae
Phaeophyceae / Brown algae
Rhodophyceae / Red algae
Pigments
  • •
    Chlorophyll-a
  • •
    \(\beta\)-carotene
  • •
    C-phycocyanin
  • •
    C-phycoerythrin
  • •
    Chlorophyll-a
  • •
    Chlorophyll-b
  • •
    \(\beta\)-carotene
  • •
    Chlorophyll-a
  • •
    Chlorophyll-c
  • •
    \(\beta\)-carotene
  • •
    Fucoxanthin
  • •
    Chlorophyll-a
  • •
    Chlorophyll-d
  • •
    \(\beta\)-carotene
  • •
    R-phycocyanin
  • •
    R-phycoerythrin
Reserve Food Material
Cyanophycean starch
Starch
Laminarin / Mannitol
Floridean starch
Examples
  • •
    Anabaena
  • •
    Nostoc
  • •
    Spirulina
  • •
    Trichodesmium erythraeum
  • •
    Chlamydomonas
  • •
    Volvox
  • •
    Spirogyra
  • •
    Ulothrix
  • •
    Oedogonium
  • •
    Chlorella
  • •
    Acetabularia
  • •
    Cephaleuros virescens
  • •
    Cephaleuros arabica
  • •
    Fucus
  • •
    Laminaria
  • •
    Sargassum
  • •
    Polysiphonia
  • •
    Batrachospermum
  • •
    Gelidium
  • •
    Gracilaria
  • •
    Gigartina
Special points
        1. Deepest algae found in deep sea due to ability to absorb blue-green light. CEE 2025
        ▢ Important Examples and Products:
        ❖ Cyanophyceae:
        ◉ Anabaena: \(N_2\) fixation
        ◉ Spirulina: Most proteinaceous algae
        Image 1
        Image 1
        ◉ Trichodesmium erythraeum: Causes red colour of the Red Sea
        Image 1
        ❖ Chlorophyceae:
        ◉ Chlorella:
        • •
          Second most proteinaceous algae
        • •
          Space algae
        • •
          Source of antibiotic chlorellin
          • Image 1
        ◉ Acetabularia:
        • •
          Largest plant cell
        • •
          Largest unicellular algae
        • •
          Sea umbrella
        ◉ Parasitic Algae:
        ◈ Cephaleuros virescens: Leaf of tea plant → red rust of tea
        ◈ Cephaleuros arabica: Leaf of coffee plant → red rust of coffee
        ❖ Phaeophyceae:
        • •
          Seaweeds
        • •
          Sea kelps
        • •
          Source of iodine
        • •
          Source of algin
        ❖ Rhodophyceae:
        ◉ Batrachospermum: Red alga appearing blue; not marine
        ◉ Carrageenin: Extracted from red algae
        ◉ Agar-Agar:
        ◈ Sources:
        • •
          Gelidium
          • Image 1
        • •
          Gracilaria
          • Image 1
        • •
          Gigartina
          • Image 1
        ◈ Use: Base of culture media
        📚
        NOSTOC
        Image 1
        ▢ Taxonomic Position:
        ❖ Class: Cyanophyceae
        ❖ Order: Nostocales
        ▢ Habitat:
        ❖ General: Usually aquatic; some species terrestrial
        ❖ Terrestrial or Symbiotic Sites:
        • •
          Rice fields
        • •
          Coralloid root of Cycas
        • •
          Leaf of Azolla
        ▢ Plant Body:
        ❖ Nature: Filamentous and colonial
        ❖ Colony Shape: Rounded or oval
        ❖ Formation: Aggregation of filaments
        ▢ Heterocyst:

        Table 1: Heterocyst Features and Functions

        Feature
        Significance
        Larger size
        Differentiation from vegetative cells
        Thick covering
        Perennation
        Polar nodules
        Hormogonium formation and asexual reproduction
        Nitrogen-fixing enzyme
        Nitrogen fixation
        ▢ Cell Structure:
        Image 1
        ❖ Type: Prokaryotic
        ❖ Centroplasm: Contains circular DNA or genophore associated with non-histone protein
        ❖ Photosynthesis: Occurs on photosynthetic lamellae
        ❖ ATP Synthesis: Occurs at structural granules
        ▢ Reproduction:
        Image 1
        ❖ Vegetative:
        • •
          Most common method
        • •
          Occurs in favourable conditions
        • •
          By hormogonium formation
        ❖ Asexual:
        • •
          Occurs in unfavourable conditions
        • •
          By akinete formation
        • •
          Thick-walled heterocyst may participate and assist in perennation
        ❖ Sexual: Absent
        📚
        CHLAMYDOMONAS
        Image 1
        ▢ General Characters:
        ❖ Organization:
        • •
          Unicellular
        • •
          Motile
        • •
          Biflagellate
        ❖ Flagella: Arise from blepharoplasts or basal granules
        ❖ Nutrition: Autotrophic
        ▢ Cell Structure:
        ❖ Chloroplast: Single, large, cup-shaped chloroplast
        ❖ Pyrenoid:
        ◉ Structure: Protein body surrounded by starch plates or starch grains
        ◉ Function: Centre of starch formation
        ❖ Stigma or Eyespot:
        ◉ Position: Anterior end
        ◉ Colour: Orange or reddish
        ◉ Pigment: Carotenoids
        ◉ Function: Photoreception and direction of movement
        ▢ Asexual Reproduction:
        • •
          Zoospores — biflagellate
        • •
          Aplanospores
        • •
          Hypnospores
        • •
          Palmella stage
        • •
          Akinetes
        ▢ Sexual Reproduction:
        ❖ Range: Isogamy → anisogamy → oogamy within the same genus
        ❖ Relative Sexuality:
        ◉ Definition: Production of two types of gametes by a unicellular organism
        ◉ Discovered by: Hertman
        ▢ Life Cycle:
        Image 1
        ❖ Type: Haplontic
        ❖ Zygospore Formation: Resting zygote develops a thick covering and becomes a zygospore
        ❖ Germination:
        1. Meiosis occurs in the zygospore
        2. Four haploid spores are formed
        3. Each spore develops into a new thallus
        📚
        VOLVOX
        Image 1
        ▢ Colony:
        ❖ Appearance: Ball-like colony, approximately 0.5 mm in diameter
        ❖ Coenobium: Hollow spherical plant body with thousands of cells arranged at the periphery
        ❖ Cell Types:
        • •
          Germ cells
        • •
          Flagellated somatic cells
        ❖ Extracellular Matrix: Glycoprotein
        ❖ Cell Connection: Adjacent cells connected by cytoplasmic strands formed during cell division
        ▢ Cell Structure:
        ❖ Shape: Spherical
        ❖ Chloroplast: Cup-shaped with pyrenoids
        ❖ Other Components:
        • •
          Nucleus
        • •
          Vacuoles
        • •
          Eyespot
        ❖ Flagella: Two equal-sized anterior flagella
        ❖ Movement: Coordinated flagellar movement propels the colony
        ❖ Metabolic Independence: Each cell independently performs respiration, photosynthesis and excretion
        ▢ Eyespot and Polarity:
        ❖ Polarity: Anterior cells possess larger eyespots than posterior cells
        ❖ Function: Light reception and phototaxis
        ▢ Ecological Importance:
        • •
          Contributes significantly to oxygen production
        • •
          Serves as food for many aquatic organisms
        ▢ Harmful Algal Bloom:
        ❖ Species: Volvox aureus
        ❖ Condition: Rapid multiplication may produce harmful algal bloom
        ❖ Favouring Factors:
        • •
          Warm water
        • •
          High nitrogen content
        ▢ Life Cycle:
        ❖ Type: Haplontic
        ❖ Dominant Stage: Free-living haploid \((n)\) gametophyte
        ❖ Sporophytic Stage: Represented only by diploid zygote \((2n)\)
        ❖ Cell Differentiation: Reproductive cells and somatic cells
        ❖ Environmental Pattern:
        ◉ Favourable Conditions: Asexual reproduction
        ◉ Unfavourable Conditions: Sexual reproduction
        ▢ Asexual Reproduction:
        ❖ Reproductive Cell: Gonidium
        ❖ Process:
        1. Gonidium undergoes multiple divisions
        2. Daughter colony of approximately 3200 cells is formed
        3. Daughter colony matures
        4. Mature daughter colony is released from the parent
        ▢ Sexual Reproduction:
        ❖ Type: Oogamous
        ❖ Sexual Condition: Coenobium may be monoecious or dioecious
        ❖ Male Reproductive Structure:
        ◉ Antheridium: Produces spermatozoa in a bunch
        ◉ Spermatozoa:
        • •
          Spindle-shaped
        • •
          Pair of apical cilia or flagella
        • •
          Released singly or in groups
        ❖ Female Reproductive Structure:
        ◉ Oogonium: Produces one ovum
        ◉ Ovum:
        • •
          Large
        • •
          Non-motile
        • •
          Green due to chloroplast
        • •
          Contains pyrenoids
        • •
          Contains stored food
        ❖ Fertilization:
        1. Antherozoids move chemotactically towards the oogonium
        2. Proteolytic enzymes break the oogonial wall
        3. Many sperms may enter, but only one fertilizes the egg
        4. Fusion forms a diploid zygote
        ❖ Zygote and Germination:
        1. Zygote forms a cyst
        2. Accumulation of haematochrome makes it red
        3. Zygote detaches after disintegration of the parent
        4. Zygote remains dormant for a long period
        5. Meiosis produces four haploid cells
        6. Repeated mitotic divisions form a new colony
        📚
        SPIROGYRA
        ▢ Habitat: Stagnant freshwater
        ▢ Common Names:
        • •
          Pond scum
        • •
          Pond silk
        • •
          Water silk
        • •
          Hair of princess
        ▢ Plant Body:
        Image 1
        ❖ Nature: Unbranched filament composed of cylindrical cells
        ❖ Slipperiness: Due to pectinous outer wall layer
        ❖ Chloroplast: 1–16 ribbon-shaped chloroplasts spirally coiled
        ❖ Pyrenoids: Numerous protein bodies surrounded by starch
        ▢ Reproduction:
        Image 1
        Fig.Life cycle of Spirogyra
        ❖ Most Common Method: Fragmentation
        ❖ Vegetative Reproduction:
        • •
          Occurs in favourable conditions
        • •
          By fragmentation
        • •
          Most common mode
        ❖ Asexual Reproduction:
        • •
          Occurs in unfavourable conditions
        • •
          Rare
        • •
          By akinete or hypnospore formation
        • •
          Zoospores absent
        ❖ Sexual Reproduction:
        ◉ Time: At the end of favourable conditions
        ◉ Type: Isogamy
        ◉ Scalariform Conjugation:
        Image 1
        ◈ Occurrence: Usually in heterothallic species
        ◈ Process:
        1. Positive and negative filaments come together under the influence of progammone hormone
        2. Conjugation tubes form with the help of cytase enzyme
        3. A ladder-like appearance develops
        4. Male gamete from the positive filament passes through the conjugation tube
        5. Fertilization occurs in the negative filament
        ◉ Lateral Indirect Conjugation:
        ◈ Occurrence: Homothallic species
        ◈ Process: A lateral tube forms between active and passive cells; male gamete passes into the passive cell
        ◈ Gamete Movement: Gametes are non-motile and move by activity of the contractile vacuole
        ◉ Lateral Direct Conjugation:
        ◈ Occurrence: Homothallic species
        ◈ Process: Membrane between active and passive cells dissolves; male gamete directly enters and fertilizes the passive cell
        ▢ Zygospore and Germination:
        1. Fertilization forms a diploid zygote \((2n)\)
        2. Under unfavourable conditions, the zygote develops a thick covering and becomes a zygospore
        3. Meiosis occurs during germination
        4. Four haploid spores are produced
        5. Three spores degenerate
        6. One spore develops into a new Spirogyra filament
        Nature of Sexual Reproduction
        ❖ Morphologically: Isogamous
        ❖ Physiologically: Anisogamous
        📚
        ULOTHRIX
        Image 1
        ▢ Plant Body:
        ❖ Nature: Unbranched filament
        ❖ Attachment: Attached to substratum by a holdfast
        ❖ Holdfast: Hyaline or colourless because chlorophyll is absent
        ▢ Cell Wall:
        ❖ Inner Layer: Cellulose
        ❖ Outer Layer: Protopectin; insoluble in water
        ❖ Texture: Filament is wet or slippery due to protopectin
        ▢ Cell Structure:
        ❖ Chloroplast: Single girdle-shaped chloroplast
        ❖ Pyrenoids: One or more
        ▢ Asexual Reproduction:
        ❖ Condition: Favourable
        ❖ Zoospores:
        • •
          Usually quadriflagellate
        • •
          May be microzoospores or macrozoospores
        • •
          Sometimes biflagellate microzoospores are produced
        • •
          All cells except the holdfast can produce zoospores
        ❖ Other Spores and Stages:
        • •
          Aplanospores — thin-walled
        • •
          Hypnospores — thick-walled
        • •
          Akinetes
        • •
          Palmella stage
        ▢ Sexual Reproduction:
        ❖ Type: Isogamous
        ❖ Thallism: Heterothallic
        ❖ Fertilization: External; occurs on the water surface
        ❖ Gametes: Motile and biflagellate
        ❖ Process:
        1. Positive and negative gametes fuse
        2. A quadriflagellate zygote is formed
        3. Zygote sinks to the bottom
        4. Flagella are lost
        5. A thick-walled zygospore is formed
        6. After a resting period, meiosis occurs
        7. Haploid meiospores are produced
        8. Under favourable conditions, each spore germinates into one new filament
        ▢ Life Cycle: Haplontic
        Q1.
        Spiral shaped chloroplast is found in: [MOE - 2008]
        📅MOE - 2008
        Q2.
        Spirogyra belongs to order:  [MOE-2063 Falgun]
        📅MOE-2063 Falgun
        Q3.
        Water bloom is caused by: [MOE-2060]
        📅MOE-2060
        Q4.
        Brown algae is found in: [MOE - 2003]
        📅MOE - 2003
        Q5.
        Reticulate type chloroplast is present in [MOE-2003 ]
        📅MOE-2003
        Q6.
        Nostoc belongs to:  [MOE-2002, 2058)
        📅MOE-2002, 2058)
        Q7.
        True nucleus is absent in:  [MOE-2057]
        📅MOE-2057
        Q8.
        Heterocyst are found in:  [MOE-2056
        📅MOE-2056
        Q9.
        Zygospore of Spirogyra is:  [MOE-2055]
        📅MOE-2055
        Q10.
        Nostoc reproduces by  [MOE-2053
        📅MOE-2053
        Q11.
        Zygospore is found in which of the following: [MOE-2060]
        📅MOE-2060
        Q12.
        Which one is biofertilizers:  [MOE - 2008)
        📅MOE - 2008)
        Q13.
        Which of the following causes red rust of tea ? [IOM - 1997]
        📅IOM - 1997
        Q14.
        Prokaryotic cell structure is found in: [IOM -1999
        📅IOM -1999
        Q15.
        Nutritious culture medium is obtained from: [IOM -2006]
        📅IOM -2006
        Q16.
        The parasitic algae is: [IOM 2002, 1999, 2010]
        📅IOM 2002, 1999, 2010
        Q17.
        The gametes of Chlamydomonas are: [IOM-200)
        📅IOM-200)
        Q18.
        Blue green algae is the name for: [IOM- 2060
        📅IOM- 2060
        Q19.
        All algae contain: [IOM - 1997, 1996]
        📅IOM - 1997, 1996
        Q20.
        During germination of zygospore in Spirogyra takes place: [IOM 199
        📅IOM 199
        Q21.
        Pyrenoids are: [BPKIHS 2005 )
        📅BPKIHS 2005 )
        Q22.
        The algae which helps in the fixation of nitrogen belongs to class. [BPKIHS 1997]
        📅BPKIHS 1997
        Q23.
        Algae is characterized by:[BPKIHS 1994]
        📅BPKIHS 1994
        Q24.
        Red colour of the red algae is due to the presence of [BPKIMS 1994)
        📅BPKIMS 1994)
        Q25.
        Algae found in thermal springs belong to [IE-2002)
        📅IE-2002)
        Q26.
        Although various types of gametes flow in water but particular gamete can fuse only with particular gamete. This is a kind of [IE - 2002]
        📅IE - 2002
        Q27.
        Chlamydomonas is  [IE - 2002]
        📅IE - 2002
        Q28.
        Among the followings, the most complete cellular structure is found in: [IE - 2002]
        📅IE - 2002
        Q29.
        Green alga belongs to  [IE - 2005]
        📅IE - 2005
        Q30.
        Organisms that fix nitrogen in aquatic habitat are [IE - 2009]
        📅IE - 2009
        Q31.
        Cyanobacteria are: [IE - 2002]
        📅IE - 2002
        Q32.
        Spores of true slime moulds are produced in structure is called:  [IE - 2007]
        📅IE - 2007
        Q33.
        Nostoc is found symbotic with [KUMET 2010]
        📅KUMET 2010
        Q34.
        Nutritive substance required for tissue culture is obtained from [BPKIHS - 2016]
        📅BPKIHS - 2016
        Q35.
        The parasitic green algae is: [BPKIHS - 2014]
        📅BPKIHS - 2014
        Q36.
        Culture media is extracted from [BPKIHS - 2014]
        📅BPKIHS - 2014
        Q37.
        Haplontic life cycle is present in [BPKIHS - 2012]
        📅BPKIHS - 2012
        Q38.
        Which of the following alga has heterotrichous habitat? [BPKIHS - 2011)
        📅BPKIHS - 2011)
        Q39.
        Agar agar and carageenin are obtained from [IOM-2014]
        📅IOM-2014
        Q40.
        Sexual reproduction in Spirogyra is  [MOE 2014]
        📅MOE 2014
        Q41.
        Chemical constituent of pyrenoid that stores starch is [MOE 2014)
        📅MOE 2014)
        Q42.
        Sexual reproduction in Spirogyra is [MOE 2013]
        📅MOE 2013
        Q43.
        Motile reproductive bodies are absent in [MOE 2012]
        📅MOE 2012
        Q44.
        How many species have been recorded on the earth? [MOE 2012]
        📅MOE 2012
        Q45.
        Sexual reproduction by conjugation is found in algae [MOE 2068)
        📅MOE 2068)
        Q46.
        Carl Linneaus is credited for introducing [MOE 2068]
        📅MOE 2068
        Q47.
        Nitrogen fixation is done by [MOE 2068]
        📅MOE 2068
        Q48.
        All living organisms of the earth belong to [MOE 2010]
        📅MOE 2010