Algae - 3

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• Algae - 3

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INTRODUCTION TO ALGAL CHARACTERISTICS AND
DIVERSITY

• PHYCOLOGYSTUDY OF ALGAE
• Phycology is the science (gr. logos) of algae
  (gr. phycos). This discipline deals with the
  morphology, taxonomy, phylogeny, biology, and
  ecology of algae in all ecosystems

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FOSSIL HISTORY OF ALGAE

• 3.5 billion yrs ago
• Cyanobacteriafirst algae
• Prokaryoteslack membrane bound organelles
• Later eukaryotes evolvedmitochondria,
  chloroplasts, and chromosomes containing DNA.

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Where do algae abound?

• Kelp  forest up to 50 m height are the marine
  equivalent to terrestrial forest mainly built by
  brown algae.
• Some algae encrust  with carbonate, building
  reef-like structures Cyanobacteria can from
  rock-like structures in warm tidal areas
  stromatolites.

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Where do algae abound?

• Algae grow or are attached to animals and serve 
  as camouflage for the animal
• Algae live as symbionts  in animals such as
  Hydra, corals, or the protozoan ciliate
  Paramecium in corals they are referred to as
  zooxanthellae

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Where do algae abound?

• Small algae live on top of larger algae
  epiphyton
• Algae in free water phytoplankton
• Terrestrial algae
• Algae have adapted to life on land and occur as
  cryptobiotic  crusts in desert and grassland
  soils or endocryptolithis algae in rocks 

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Where do algae abound?

• Algae live on the snow cover of glaciers and in
  the brine  channels of sea ice.
• A symbiosis  of algae and fungi produced the
  lichens, which are pioneer plants, help convert
  rock into soil by excreting acids, stabilize
  desert soil, are sensitive to air pollution
•  

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Where do algae abound?

• Algae can cover trees or buildings green or live
  in the hollow  hairs of ice bears

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Algal Blooms

• Algae can be so dominant that they discolor the
  water 
• Higher amounts of nutrients are usually the cause
• Algal blooms can have harmful effects on life and
  ecosystem
• Reduced water clarity causes benthic communities
  to die off
• Fish kills are common effects
• 50 of algal blooms produce toxins harmful to
  other organisms, including humans
• Algal blooms produce a shift  in food web
  structure and species composition
• Algal blooms can mostly be linked to sewage input
  or agricultural activities, leading to nutrient
  pollution Eutrophication

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Similarities

• Presence of cell wallmostly cellulosic.
• Autotrophs/Primary producerscarry out
  photosynthesis
• Presence of chlorophyll a

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Differences

• Algae lack the roots, stems, leaves, and other
  structures typical of true plants.
• Algae do not have vascular tissuesnon vascular
  plants
• Algae do not form embryos within protective
  coveringsall cells are fertile.
• Variations in pigments.
• Variations in cell structureunicellular,
  colonial and multicellular forms.

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PROKARYOTIC VS EUKARYOTIC ALGAE

• Prokaryote algal cell

• Prokaryotes
• ---No nuclear region and complex
  organelleschloroplasts, mitochondria, golgi
  bodies, and endoplasmic reticula.
• -- Cyanobacteria. Chlorophylls are on internal
  membranes of flattened vesicles called
  thylakoids-contain photosynthetic pigments.
  Phycobiliproteins occur in granular structures
  called phycobilisomes.

Source http//www.botany.hawaii.edu/faculty/webb/
BOT311/Cyanobacteria/Cyanobacteria.htm
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Prokaryotic and Eukaryotic Algae

• Eukaryotes
• ---Distinct chlorplast, nuclear region and
  complex organelles.
• --- Thylakoids are grouped into grana
• pyrenoids are centers of carbon dioxide fixation
  within the chloroplasts of algae and hornworts.
  Pyrenoids are not membrane-bound organelles, but
  specialized areas of the plastid that contain
  high levels of ribulose-1,5-bisphosphate
  carboxylase/oxygenase

granum with a Stack of thylakoids
pyrenoid
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Forms of Algae
Forms of algae
Multicellular
Unicellular

• Colonies
• 2. Aggregations
• Palmelloid (Tetraspora)
• Dendroid (Dinobryon)
• Amoeboid (Chlororachnion)
• 3.Filaments
• 4. Coenocytic / Vaucheria
• 5.Parenkematus/ Ulva
• 6. Psedoparenkematus / Batrachospermum
• 7. Erect thallus / Chara

Non motile(Chlorella)
Motile (Euglena)
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Forms of Algae

• BODY OF AN ALGATHALLUS
• DIVERSITY IN MORPHOLOGY
• ----MICROSCOPIC
• Unicellular, Colonial and Filamentous forms.

Source http//images.google.com/images
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Forms of Algae
MACROALGAE
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Forms of Algae
MICRO ALGAE
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Forms of Algae

• Unicells single cells, motile with flagellate
  (like Chlamydomonas and Euglena) or nonmotile
  (like Diatoms)

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• 2. Multicellular form the vegetation forms are
  in six forms
• Colonies
• Assemblage of individual cells with variable or
  constant number of cells that remain constant
  throughout the colony life in mucilaginous matrix
  (containing an extracellular matrix made of a
  gelatinous glycoprotein), these colonies may be
  motile (like Volvox and Pandorina) or nonmotile
  (like Scendesmus and Pediastrum).

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• Coenobium
• Colony with constant number of cells, which
  cannot survive alone specific tasks among
  groups of cells is common (is a colony containing
  a fixed number of cells, with little or no
  specialization)

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• b. Aggregations is aggregation of cells that
  have ability to simple division (so, its colony
  but unconstant in form and size), the
  aggregations are in several types
• Palmelloid form non-motile cells embedded in
  mucilage (like Tetraspora).

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• Dendroid form resembling a tree in form or in
  pattern of growth (Dinobryon).

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• Amoeboid or Rhizopodial form such as
  Chlorarachnion.

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• c. Filaments daughter cells remain attached
  after cell division and form a cell chain
  adjacent cells share cell wall (distinguish them
  from linear colonies!) maybe unbranched
  (uniseriate such as Zygnema and Ulthrix) or
  branched (regular mutiseriate such as Cladophora
  or unreguler mutiseriate such as Pithophora).

Cladophora
Pithophora
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• d. Coenocytic or siphonaceaous forms one large,
  multinucleate cell without cross walls such as
  Vaucheria

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• e. Parenchymatous (such as Ulva ) and algae
  mostly macro-scopic algae with tissue of
  undifferentiated cells and growth originating
  from a meristem with cell division in three
  dimensions

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pseudoparenchymatous (such as Batrachospermum)
pseudoparenchymatous superficially resemble
parenchyma but are composed of apprised filaments
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• f. Erect thallus forms Thallus, from Latinized
  Greek (thallos), meaning a green shoot or twig,
  is an undifferentiated vegetative tissue (leaves,
  roots, and stems) of some non-mobile organisms
  such as Chara and Nitella.

Chara
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CELLULAR ORGANIZATION

• Flagellaorgans of locomotion.
• Chloroplastsite of photosynthesis. Thylakoids
  are present in the chloroplast. The pigments are
  present in the thylakoids.
• Pyrenoid-structure associated with chloroplast.
  Contains ribulose-1,5-bisphosphate Carboxylase,
  proteins and carbohydrates.
• Eye-spotpart of chloroplast. Directs the cell
  towards light.

Source A Biology of the Algae By Philip Sze,
third edition, WCB MCGraw-Hill
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Variations in the pigment constitution

• Chlorophylls (green)
• Carotenoids (brown, yellow or red)
• Phycobilins (red pigment-phycoerythrin
• blue pigment phycocyanin)

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Growth in algae

• Diffuse or generalized growth (Ulva).
• Localized growth
• Apical growth (Chara, Cladophora).
• Basal growth (Bulbochaete).
• Intercalary growth (Laminaria, Oedogonium).
• Trichothallic growth (Ectocarpus)

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Growth in algae
Tricothallic
Apical and intercalary
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Reproduction in algae

• The reproduction of algae can be
  discussed under two types, namely, asexual
  reproduction and sexual reproduction. The former
  type refers to reproduction in which a new
  organism is generated from a single parent. In
  case of sexual type, two haploid sex cells are
  fused to form a diploid zygote that develops into
  an organism. Let's discuss in brief about the
  asexual and sexual reproduction in algae along
  with examples.

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• First Asexual Reproduction includes
• 1. Vegetation reproduction
• In unicellular algae simple cell division some
  time called binary fission (such as Gleocapsa).
• In multicellular (colonies, filamentous, thallus,
  etc) by
• Fragmentation such as Microsystis.
• Hormogonia A small, motile filament, formed by
  some Cyanobacteria, that detaches and grows by
  cell division into a new filament such as
  Oscillatoria.
• Propagules a structure capable of producing a
  new individual such as Sphacelaria.

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Vegetative reproduction
Cell Division A cell could not keep growing
bigger forever. Food molecules could not reach
the inside of a large cell fast enough to keep it
alive. So when a cell reached a certain size it
had to divide into two smaller cells called
daughters. The daughters grew and, when they
reached that certain size, they too divided, this
processes called binary fission. But this
caused a problem, Why?.
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Vegetative reproduction
Hormogonia in Oscillatoria
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Vegetative reproduction
Propagules
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• 2. Another method of asexual reproduction in
  algae is by formation of spores the algal
  species Ulothrix, Chlamydomonas and Chlorella
  reproduce by this method. Depending upon the
  algal species, the spores can be produced in
  normal vegetative cells or specialized cells
  called sporangia. They are either motile called
  zoo spores or non motile called akinete spores.

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Ulotrix
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• There are a lot of types of akinete spores such
  as
• Autospores immobile spores that cannot develop
  flagella such as Chlorella.
• Aplanospores immobile spores that may
  nevertheless potentially grow flagella.
• Hypnospores A thick-walled resting cyst.
• Tetraspores spores produced by a
  tetrasporophyte, characteristic of red algae.
• Statospores spores that are not actively
  discharged from the algal fruiting body
• Auxospores A spore in diatom algae that leads
  to reformation of an enlarged vegetative cell.

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Second Sexual Reproduction
As already mentioned, sexual reproduction takes
place by the union of male and female gametes.
The gametes may be identical in shape and size
called isogamy or different called heterogamy.
Some of the simplest forms of algae like
Spirogyra reproduce by the conjugation method of
sexual reproduction. In the process of
conjugation, two filamentous strands (or two
organisms) of the same algae species exchange
genetic material through the conjugation tube.
Among two strands, one acts as a donor and
another serves as a receiver. After exchanging
the genetic material, two strands separate from
each other. The receiver then give rise to a
diploid organism.
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Second Sexual Reproduction
Isogamy is the form of sexual reproduction in
which the gametes produced are identical in
shape, size and motility. There is no structural
distinction between "male" and "female" gametes.
Pairs of isogametes align themselves with their
flagellar poles touching and after several
seconds, the motile gametes fuse to form a
single, non-motile, diploid zygote.
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Second Sexual Reproduction
Isogametes, less commonly, may be non-motile
structures. A specific example exhibiting
non-motile isogametes is the reproductive process
known as conjugation, in Figure below, the
conjugating Spirogyra identify the four stages of
the process as outlined.
Isogamy in Spirogyra sp.
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A. Resting filaments of alga cells. B. Formation
of conjugation tubes between two adjacent
filaments. C. Cytoplasmic contents of each cell
form a compact mass, representing an isogamete.
The isogametes from one filament migrate through
the conjugation tubes into the adjacent
filament. The two isogametes unite to form a
zygote. Each zygote eventually undergoes meiosis
to form four haploid cells. One haploid cell will
form a new filament by mitosis, the other three
degenerate.
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Heterogamy In heterogamy, two different types of
gametes are produced. The male gamete, the sperm
cell, is typically very small, highly motile and
is produced in very large numbers. The female
gamete, the egg cell, is much larger and
non-motile, called Oogamy. Fewer female gametes
are produced but each is usually afforded some
protection. Heterogametes are also produced by
higher plants and animals.
Oedogonium sp. is a green alga that produces
heterogametes. The figure bellow illustrates the
life cycle of this alga. You can locate a mature
egg cell and the small male filaments, which are
the site of sperm production, the egg cells and
male filaments are usually adjacent to one
another on the same algal strand.
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Heterogamy in Oedogonium sp.
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SEXUAL REPRODUCTION

• ISOGAMY-Both gametes have flagella and similar in
  size and morphology.
• ANISOGAMY-Gametes have flagella but are
  dissimilar in shape and size. One gamete is
  distinctly smaller than the other one.
• OOGAMY-gamete with flagella (sperm) fuses with a
  larger, non flagellated gamete (egg).

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REPRODUCTION
Sexual-Gametes
Vegetative Cell divisions/Fragmentation part of
the filament breaks off from the rest and forms
a new one.
Asexual Reproduction Zoospores after losing their
flagella, form new filaments. No sexual fusion.
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a, b, and c are zoospores d, e, and f are
aplanospores g, and h are hypnospores K is
autospores. L is Isogamous, m is Anisogamous,
and n is Oogamous
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• Gametes look like vegetative cells or very
  different
• Isogamy both gametes look identical
• Anisogamy male and female gametes differ
  morphologically
• Oogamy One gamete is motile (male), one is
  nonmotile (female)
• Monecious both gametes produced by the same
  individual
• Diecious male and female gametes are produced by
  different individuals
• Homothallic gametes from one individual can fuse
  (self-fertile)
• Heterothallic gametes from one individual cannot
  fuse (self-sterile)

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The life cycles in algae

• Three different types of life cycle, depending on
  when miosis occurs, the type of cells produced,
  and if there is more than one free-living stage
  present in the life-cycle.

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The life cycles in algae

• Life-cycle I (haploid life cycle) major part of
  life-cycle (vegetative phase) in haploid state,
  with meiosis upon germination of the zygote
  (zygotic meiosis) also referred to as haplontic
  life cycle, a single, predominant haploid phase

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The life cycles in algae

• Life-cycle II (Diploid life cycle) vegetative
  phase is diploid, with meiosis upon formation of
  gametes (gametic meiosis) also referred to as
  diplontic life cycle, a single, predominant
  diploid phase

 
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The life cycles in algae

• Life-cycle III (Diplobiontic life cycle) three
  multicellular phases, the gametophyte and one or
  more sporophyte(s)
• Gametophyte typically haploid, produces gametes
  by mitosis Sporophyte typically diploid,
  produces spores by meiosis Isomorphic
  sporophyte and gametophyte look alike
  Heteromorphic sporo- and gametophyte look
  different

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Basis of algal Classification

• the different groups of algae can be classified
  on the basis of a number of characteristics.
• 1. Color has been an important means of
  classifying algae, and gives many groups their
  names. However, other characteristics, such as
  type of photosynthetic food reserve, flagella
  type, cell wall structure and composition, and
  life history, have been important in further
  distinguishing the algal divisions.

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Flagella

• Locomotion in algae is largely based on the
  action of flagella. The figure below illustrates
  the wide variety of flagella present in the
  algae. The primary distinctions used for
  classification are the number of flagella, their
  location on the cell, and their morphology. Two
  major types of flagella are recognized the
  smooth, or acronematic, and the hairy, or
  pleuronematic, types. The smooth flagella
  generally moves by whiplash motion and the hairy
  flagella moves by a pulling motion.

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ECOLOGICAL DIVERSITY

• LAND---WATER
• FRESH WATER---MARINE HABITATS
• FLOATING (PLANKTONIC)BENTHIC (BOTTOM DWELLERS)
• EPIPHYTES

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