PROTIST

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PROTIST

• These diatoms, with their beautiful glasslike
  walls, make up a small part of the diverse group
  known as protists

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PROTIST
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The Kingdom Protista

• On a dark, quiet night you sit at the stern of a
  tiny sailboat as it glides through the calm
  waters of a coastal inlet
• Suddenly, the boat's wake sparkles with its own
  light
• As the stern cuts through the water, glimmering
  points of light leave a ghostly trail into the
  darkness
• What's responsible for this eerie display?
• You've just had a close encounter with one group
  of some of the most remarkable organisms in the
  worldthe protists

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What Is a Protist?

• The kingdom Protista is a diverse group that may
  include more than 200,000 species
• Biologists have argued for years over the best
  way to classify protists, and the issue may never
  be settled
• In fact, protists are defined less by what they
  are and more by what they are not A protist is
  any organism that is not a plant, an animal, a
  fungus, or a prokaryote
• Protists are eukaryotes that are not members of
  the kingdoms Plantae, Animalia, or Fungi
• Recall that a eukaryote has a nucleus and other
  membrane-bound organelles
• Although most protists are unicellular, quite a
  few are not, as you can see in the figure at
  right
• A few protists actually consist of hundreds or
  even thousands of cells but are still considered
  protists because they are so similar to other
  protists that are truly unicellular

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Examples of Protists

• Protists are a diverse group of mainly
  single-celled eukaryotes
• Examples of protists include freshwater ciliates,
  radiolarians, and Spirogyra
• Spirogyra may form slimy floating masses in fresh
  water
• The organisms name refers to the helical
  arrangement of its ribbonlike chloroplasts

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Examples of Protists
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Evolution of Protists

• Protists are members of a kingdom whose formal
  name, Protista, comes from Greek words meaning
  the very first
• The name is appropriate
• The first eukaryotic organisms on Earth, which
  appeared nearly 1.5 billion years ago, were
  protists

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Evolution of Protists

• Where did the first protists come from?
• Biologist Lynn Margulis has hypothesized that the
  first eukaryotes evolved from a symbiosis of
  several cells
• Mitochondria and chloroplasts found in eukaryotic
  cells may be descended from aerobic and
  photosynthetic prokaryotes that began to live
  inside larger cells

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PROTISTA

• First eukaryotic cells found in fossils dated
  1.45 billion years ago
• Suggested they evolved from prokaryotes
• According to endosymbiosis, prokaryotic parasites
  once lived inside other prokaryotic cells
• The parasitic prokaryotes lost the ability to
  live independently of their hosts and evolved
  into various cell organelles
• Example
• Mitochondria arose from parasitic bacteria
• Chloroplast arose from parasitic blue-green
  bacteria
• Nucleus probably did not arose from endosymbiosis
  but came to exist as an organelle when DNA was
  enclosed within a double membrane

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EUKARYOTE EVOLUTION
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Classification of Protists

• Protists are so diverse that many biologists
  suggest that they should be broken up into
  several kingdoms
• This idea is supported by recent studies of
  protist DNA indicating that different groups of
  protists evolved independently from
  archaebacteria
• Unfortunately, at present, biologists don't agree
  on how to classify the protists
• Therefore, we will take the traditional approach
  of considering the protists as a single kingdom

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Classification of Protists

• One way to classify protists is according to the
  way they obtain nutrition
• Thus, many protists that are heterotrophs are
  called animallike protists
• Those that produce their own food by
  photosynthesis are called plantlike protists
• Finally, those that obtain their food by external
  digestioneither as decomposers or parasitesare
  called funguslike protists
• This is the way in which we will organize our
  investigation of the protists

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KINGDOM PROTISTA

• All are eukaryotes
• Most are microscopic and unicellular, though some
  form colonies in which cell specialization occurs
• Three types
• Protozoa animal-like
• Algae plant-like
• Fungus-like slime molds

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Classification of Protists

• It is important to understand that these
  categories are an artificial way to organize a
  very diverse group of organisms
• Categories based on the way protists obtain food
  do not reflect the evolutionary history of these
  organisms
• For example, all animallike protists did not
  necessarily share a relatively recent ancestor
• The protistan family tree is likely to be redrawn
  many times as the genes of the many species of
  protists are analyzed and compared using the
  powerful tools of molecular biology

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Animallike Protists Protozoans

• At one time, animallike protists were called
  protozoa, which means first animals, and were
  classified separately from more plantlike
  protists
• Like animals, these organisms are heterotrophs
• The four phyla of animallike protists are
  distinguished from one another by their means of
  movement
• Zooflagellates swim with flagella
• Sarcodines move by extensions of their cytoplasm
• Ciliates move by means of cilia
• Sporozoans do not move on their own at all

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CLASSIFICATION OF PROTOZOA

• Classification based on locomotion
• Four Phyla
• Phylum Sarcodina movement by using cytoplasmic
  projections called pseudopodia
• Phylum Ciliophora movement by the use of cilia
• Phylum Zoomastigina move by means of flagella
• Phylum Sporozoa immobile and parasitic

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PROTOZOA CLASSIFICATION
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Zooflagellates

• Many protists easily move through their aquatic
  environments propelled by flagella
• Flagella are long, whiplike projections that
  allow a cell to move
• Animallike protists that swim using flagella are
  classified in the phylum Zoomastigina and are
  often referred to as zooflagellates
• Most zooflagellates have either one or two
  flagella, although a few species have many
  flagella

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Zooflagellates

• Zooflagellates are generally able to absorb food
  through their cell membranes
• Many live in lakes and streams, where they absorb
  nutrients from decaying organic material
• Others live within the bodies of other organisms,
  taking advantage of the food that the larger
  organism provides
• Example termites

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Zooflagellates

• Most zooflagellates reproduce asexually by
  mitosis and cytokinesis
• Mitosis followed by cytokinesis results in two
  cells that are genetically identical
• Some zooflagellates, however, have a sexual life
  cycle as well
• During sexual reproduction, gamete cells are
  produced by meiosis
• When gametes from two organisms fuse, an organism
  with a new combination of genetic information is
  formed

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PHYLUM ZOOMASTIGINA

• Also called Mastigophora
• Characterized by the presence of one or more long
  flagella
• The undulations of whiplike flagella push or pull
  the protozoan through the water
• Most are free-living
• Some are parasites
• Genus Trypanosoma
• Live in the blood of their host (including
  humans)
• Transmitted by bloodsucking vectors
• Ultimately invades the brain and usually fatal
• Example trypanosomiasis (sleeping sickness)
• Genus Leishmania
• Vector sand flea
• Disfiguring skin sores and may be fatal
• Genus Giardia
• Carried by muskrats and beavers
• Transmitted by contaminated drinking water
• Symptons fatigue, diarrhea, cramps, and weight
  loss

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ZOOMASTIGINATRYPANOSOMA
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Sarcodines

• Members of the phylum Sarcodina, or sarcodines,
  move via temporary cytoplasmic projections known
  as pseudopods
• Sarcodines are animallike protists that use
  pseudopods for feeding and movement
• The best-known sarcodines are the amoebas
• Amoebas are flexible, active cells with thick
  pseudopods that extend out of the central mass of
  the cell
• The cytoplasm of the cell streams into the
  pseudopod, and the rest of the cell follows
• This type of locomotion is known as amoeboid
  movement

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PHYLUM SARCODINA

• 40,000 species
• Most have flexible cell membranes
• Many do not have any added protective covering
• Marine forms
• Genus Foraminifera have calcium carbonate shells
  with spikelike protrusions
• Genus Radiolaria have supportive silicon dioxide
  inside their shell
• Freshwater forms
• Genus Ameba (Amoeba)
• Bottom-dwelling scavengers
• Movement
• Pseudopodia cytoplasmic extension that function
  in movement
• Two regions
• Ectoplasm thin, slippery colloidal sol directly
  inside the cell membrane
• Endoplasm colloidal sol and gel found in the
  interior of the cell
• When movement begins, the endoplasm pushes
  outward, facilitated by the slippery ectoplasm,
  and becomes distinguishable as a pseudopodium
• At the same time, previously formed pseudopodia
  are retracted
• Move forward by ameboid movement
• Form of cytoplasmic streaming, the internal
  flowing of the contents of the cell

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Sarcodines

• Sarcodines use pseudopods for feeding and
  movement.
• The amoeba, a common sarcodine, moves by first
  extending a pseudopod away from its body
• The organism's cytoplasm then streams into the
  pseudopod
• This shifting of the mass of the cell away from
  where it originated is a slow but effective way
  to move from place to place
• Amoebas also use pseudopods to surround and
  ingest prey

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Sarcodines
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AMEBA
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AMOEBA
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AMEBA MOVEMENT
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Sarcodines

• Amoebas can capture and digest particles of food
  and even other cells
• They do this by surrounding their meal, then
  taking it inside themselves to form a food
  vacuole
• A food vacuole is a small cavity in the cytoplasm
  that temporarily stores food
• Once inside the cell, the material is digested
  rapidly and the nutrients are passed along to the
  rest of the cell
• Undigestible waste material remains inside the
  vacuole until its contents are eliminated by
  releasing them outside the cell
• Amoebas reproduce by mitosis and cytokine

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PHYLUM SARCODINA

• Contractile vacuole organelle that excretes
  water
• Freshwater organisms are usually hypertonic
  relative to their environment, and water diffuses
  into them
• In order to maintain homeostasis, many freshwater
  unicellular organisms have contractile vacuoles
  that excrete excess water
• Nutrients
• Absorbed by diffusion
• Ingested by phagocytosis
• Contacted food is surrounded with pseudopodia
• Portion of cell membrane pinches together and
  surrounds the food
• Food vacuole forms encasing the nutrients
• Enzymes from the cytoplasm enter the vacuole and
  digest the food
• Any undigested food leaves the cell in a reverse
  process that is known as exocytosis

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Sarcodines

• Foraminiferans, another member of Sarcodina, are
  abundant in the warmer regions of the oceans
• Foraminiferans secrete shells of calcium
  carbonate (CaCO3)
• As they die, the calcium carbonate from their
  shells accumulates on the bottom of the ocean
• In some regions, thick deposits of foraminiferan
  shells have formed on the ocean floor
• The white chalk cliffs of Dover, England, are
  huge deposits of foraminiferan skeletons that
  were raised above sea level by geological
  processes

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FORAMINIFERAL FOSSILS
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FORAMINIFERAN
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Sarcodines

• Heliozoans comprise another group of sarcodines
• The name heliozoa means sun animal
• Thin spikes of cytoplasm, supported by
  microtubules, project from their silica (SiO2)
  shells, making heliozoans look like the sun's rays

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RADIOLARIA
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PHYLUM SARCODINA

• Reproduction
• Binary fission (asexual) (mitotic)
• During poor conditions, can form cyst
• Dormant cells surrounded by a hard layer

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Ciliates

• The phylum Ciliophora is named for cilia
  (singular cilium), short hairlike projections
  similar to flagella
• Members of the phylum Ciliophora, known as
  ciliates, use cilia for feeding and movement
• The internal structure of cilia and flagella are
  identical
• The beating of cilia, like the pull of hundreds
  of oars in an ancient ship, propels a cell
  rapidly through water

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PHYLUM CILIOPHORA

• 8,000 species
• Referred to as ciliates
• Move by means of cilia
• Short, hairlike projections that line the cell
  membrane and beat in synchronized strokes
• Live in marine and freshwater environments
• Genus paramecium is the most studied

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Ciliates

• Ciliates are found in both fresh and salt water
• In fact, a lake or stream near your home might
  contain many different ciliates
• Most ciliates are free living, which means that
  they do not exist as parasites or symbionts

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Ciliates Internal Anatomy 

• Some of the best-known ciliates belong to the
  genus Paramecium
• A paramecium can be as long as 350 micrometers
• Its cilia, which are organized into evenly spaced
  rows and bundles, beat in a regular, efficient
  pattern
• The cell membrane of a paramecium is highly
  structured and has trichocysts just below its
  surface
• Trichocysts are very small, bottle-shaped
  structures used for defense
• When a paramecium is confronted by danger, such
  as a predator, the trichocysts release stiff
  projections that protect the cell

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PARAMECIUM TRICHOCYST
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Ciliates Internal Anatomy 

• A paramecium's internal anatomy is shown in the
  figure
• Like most ciliates, a paramecium possesses two
  types of nuclei a macronucleus and one or more
  smaller micronuclei
• Why does a ciliate need two types of nuclei?
• The macronucleus is a working library of
  genetic informationa site for keeping multiple
  copies of most of the genes that the cell needs
  in its day-to-day existence
• The micronucleus, by contrast, contains a
  reserve copy of all of the cell's genes

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Paramecium Anatomy    

• Ciliates use hairlike projections called cilia
  for feeding and movement
• Ciliates, including this paramecium, are covered
  with short, hairlike cilia that propel them
  through the water
• Cilia also line the organism's gullet and move
  its foodusually bacteriato the organism's
  interior
• There, the food particles are engulfed, forming
  food vacuoles
• The contractile vacuoles collect and remove
  excess water, thereby helping to achieve
  homeostasis, a stable internal environment

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Paramecium Anatomy    
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PARAMECIUM
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PHYLUM CILIOPHORA

• Structure
• Never changes shape like an ameba because it is
  surrounded by a rigid protein covering, the
  pellicle which is covered with thousands of cilia
  arranged in rows
• Cilia beat in waves
• Each wave passes slantwise across the long axis
  of the body of the paramecium, causing it to
  rotate as it moves forward
• Distinctive trait is the presence of two kinds of
  nuclei
• Large macronucleus controls such cell activities
  as respiration, protein synthesis, digestion, and
  sexual reproduction
• Small micronucleus is involved in sexual
  reproduction and heredity

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PARAMECIUM
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PARAMECIUM
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PHYLUM CILIOPHORA

• Responses
• Most ciliates exhibit avoidance behavior
• Movement away from a potentially harmful situation

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PARAMECIUM RESPONSE MOVEMENT
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VORTICELLA
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VORTICELLA
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STENTOR
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Ciliates Internal Anatomy 

• Many ciliates obtain food by using cilia to sweep
  food particles into the gullet, an indentation in
  one side of the organism
• The particles are trapped in the gullet and
  forced into food vacuoles that form at its base
• The food vacuoles pinch off into the cytoplasm
  and eventually fuse with lysosomes, which contain
  digestive enzymes
• The material in the food vacuoles is digested,
  and the organism obtains nourishment
• Waste materials are emptied into the environment
  when the food vacuole fuses with a region of the
  cell membrane called the anal pore

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PHYLUM CILIOPHORA

• Nutrition
• Numerous cellular structures adapted for feeding
  on bacteria and other protists
• Funnellike oral groove lined with cilia
• The beating cilia create water currents that
  sweep food down the oral groove to the mouth pore
  which connects with the gullet forming food
  vacuoles that circulate throughout the cytoplasm
• Contents of the food vacuoles are then digested
  and absorbed
• Indigestible matter remaining in the food vacuole
  moves to the anal pore, an opening where waste is
  eliminated

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Ciliates Internal Anatomy

• In fresh water, water may move into the
  paramecium by osmosis
• This excess water is collected in vacuoles
• These vacuoles empty into canals that are
  arranged in a star-shaped pattern around
  contractile vacuoles
• Contractile vacuoles are cavities in the
  cytoplasm that are specialized to collect water
• When a contractile vacuole is full, it contracts
  abruptly, pumping water out of the organism
• The expelling of excess water via the contractile
  vacuole is one of the ways the paramecium
  maintains homeostasis

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Conjugation

• Under most conditions, ciliates reproduce
  asexually by mitosis and cytokinesis
• When placed under stress, paramecia may engage in
  a process known as conjugation that allows them
  to exchange genetic material with other
  individuals
• The process of conjugation is shown in the figure

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Conjugation

• During conjugation, two paramecia attach
  themselves to each other and exchange genetic
  information
• The process is not reproduction because no new
  individuals are formed
• Conjugation is a sexual process, however, and it
  results in an increase in genetic diversity

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Conjugation
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Conjugation

• Conjugation begins when two paramecia attach
  themselves to each other
• Meiosis of their diploid micronuclei produces
  four haploid micronuclei, three of which
  disintegrate
• The remaining micronucleus in each cell divides
  mitotically, forming a pair of identical
  micronuclei
• The two cells then exchange one micronucleus from
  each pair
• The macronuclei disintegrate, and each cell forms
  a new macronucleus from its micronucleus
• The two paramecia that leave conjugation are
  genetically identical to each other, but both
  have been changed by the exchange of genetic
  information

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Conjugation

• Conjugation is not a form of reproduction,
  because no new individuals are formed
• It is, however, a sexual processbecause it uses
  meiosis to produce new combinations of genetic
  information
• In a large population, conjugation helps to
  produce and maintain genetic diversity

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PHYLUM CILIOPHORA

• Reproduction
• Asexual by binary fission
• Only the micronucleus divides by mitosis
• The macronucleus, which contains up to 500 times
  more DNA than the micronucleus, simply elongates
  and splits, each going to a daughter cell
• Sexual by process called conjugation
• Involves individuals from two mating strains
• Lie next to each other
• Each diploid micronucleus then undergoes meiosis,
  producing four haploid (monoploid) micronuclei
• In each cell, three of these disappear the
  fourth moves to the oral groove where it
  undergoes mitosis producing two haploid
  (monoploid) micronuclei of unequal size
• The smaller micronucleus from one paramecium then
  exchanges places with the smaller micronucleus
  from the other paramecium
• Each small micronucleus then fuses with each
  larger micronucleus, forming a diploid
  micronucleus
• The two paramecium separate, and macronuclei form
  again

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CONJUGATION
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CONJUGATION
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Sporozoans

• While many animallike protists are free living,
  some are parasites
• Members of the phylum Sporozoa do not move on
  their own and are parasitic
• Sporozoans are parasites of a wide variety of
  organisms, including worms, fish, birds, and
  humans
• Many sporozoans have complex life cycles that
  involve more than one host
• Sporozoans reproduce by sporozoites
• Under the right conditions, a sporozoite can
  attach itself to a host cell, penetrate it, and
  then live within it as a parasite

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PHYLUM SPOROZOA

• 6,000 species
• No means of locomotion
• All are parasitic
• Carried in the blood and other body fluids of
  their host
• Genus Plasmodium causes malaria
• Kills 2 million people a year
• Most prevalent in the tropics
• Life cycle
• Vector female Anopheles mosquito sexual stage
• Human asexual stage in liver, red blood cells
• Spore stage releases toxins

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SPOROZOA LAPTOTHECA
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ANOPHELES MOSQUITO
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MALARIA
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MALARIA
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Animallike Protists and Disease

• Unfortunately for humans and for other organisms,
  many protists are disease-causing parasites
• Some animallike protists cause serious diseases,
  including malaria and African sleeping sickness

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Malaria

• Malaria is one of the world's most serious
  infectious diseases
• As many as 2 million people still die from
  malaria every year
• The sporozoan Plasmodium, which causes malaria,
  is carried by the female Anopheles mosquito

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Malaria

• When an infected mosquito bites a human, the
  mosquito's saliva, which contains sporozoites,
  enters the human's bloodstream
• Once inside the blood, Plasmodium infects liver
  cells and then red blood cells, where it
  multiplies rapidly
• When the red blood cells burst, the release of
  the parasites into the bloodstream produces
  severe chills and fever, symptoms of malaria

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Malaria

• Although drugs such as chloroquinine are
  effective against some forms of the disease, many
  strains of Plasmodium are resistant to these
  drugs
• Scientists have developed a number of vaccines
  against malaria, but to date most are only
  partially effective
• For the immediate future, the best means of
  controlling malaria involve controlling the
  mosquitoes that carry it

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Other Protistan Diseases 

• Zooflagellates of the genus Trypanosoma cause
  African sleeping sickness
• The trypanosomes that cause this disease are
  spread from person to person by the bite of the
  tsetse fly
• Trypanosomes destroy blood cells and infect other
  tissues in the body
• Symptoms of infection include fever, chills, and
  rashes
• Trypanosomes also infect nerve cells
• Severe damage to the nervous system causes some
  individuals to lose consciousness, lapsing into a
  deep and sometimes fatal sleep from which the
  disease gets its name
• The control of the tsetse fly and the protist
  pathogens that it spreads is a major goal of
  health workers in Africa

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Other Protistan Diseases 

• In certain regions of the world, many people are
  infected with species of Entamoeba
• The parasitic protist Entamoeba causes a disease
  known as amebic dysentery
• The parasitic amoebas that cause this disease
  live in the intestines, where they absorb food
  from the host
• They also attack the wall of the intestine
  itself, destroying parts of it in the process and
  causing severe bleeding
• These amoebas are passed out of the body in feces
• In places where sanitation is poor, the amoebas
  may then find their way into supplies of food and
  water
• In some areas of the world, amoebic dysentery is
  a major health problem, weakening the human
  population and contributing to the spread of
  other diseases

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Other Protistan Diseases 

• Amebic dysentery is common in areas with poor
  sanitation, but even crystal-clear streams may be
  contaminated with the flagellated pathogen,
  Giardia
• Giardia produces tough, microscopic-size cysts
  that can be killed only by boiling water
  thoroughly or by adding iodine to the water
• Infection by Giardia can cause severe diarrhea
  and digestive system problems

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Ecology of Animallike Protists

• Many animallike protists play essential roles in
  the living world
• Some live symbiotically within other organisms
  (termites)
• Others recycle nutrients by breaking down dead
  organic matter
• Many animallike protists live in seas and lakes,
  where they are eaten by tiny animals, which in
  turn serve as food for larger animals (Food Chain)

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Ecology of Animallike Protists

• Some animallike protists are beneficial to other
  organisms
• Trichonympha is a zooflagellate that lives within
  the digestive systems of termites
• This protist makes it possible for the termites
  to eat wood
• Termites do not have enzymes to break down the
  cellulose in wood
• Incidentally, neither do humans, so it does us
  little good to nibble on a piece of wood
• How, then, does a termite digest cellulose?
• In a sense, it doesn't. Trichonympha does

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Ecology of Animallike Protists

• Trichonympha and other organisms in the termite's
  gut manufacture cellulase
• Cellulase is an enzyme that breaks the chemical
  bonds in cellulose and makes it possible for
  termites to digest wood
• Thus, with the help of their protist partners,
  termites can munch away, busily digesting all the
  wood they can eat

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Plantlike Protists Unicellular Algae

• Many protists contain the green pigment
  chlorophyll and carry out photosynthesis
• Many of these organisms are highly motile, or
  able to move about freely
• Despite this, the fact that they perform
  photosynthesis is so important that we group
  these protists in a separate category, the
  plantlike protists
• Plantlike protists are commonly called algae

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KINGDOM PROTISTA

• Algae diverse group of eukaryotic, plantlike
  organisms
• Autotrophic
• Have chloroplasts and produce their own food by
  photosynthesis
• Not classified with Plants because they have
  different methods of reproduction
• Algae have gametes that are formed in and
  protected by unicellular gametangia, or
  single-celled gamete holders
• Plants have gametes formed in multicellular
  gametangia
• Often have pyrenoids
• Organelles that synthesize and store starch
• Almost all are aquatic,and even the terrestrial
  forms require water for reproduction
• Many aquatic algae possess flagella

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Plantlike Protists Unicellular Algae

• Some scientists place those algae that are more
  closely related to plants in the kingdom Plantae
• In this Text, we will consider all forms of
  algae, including those most closely related to
  plants, to be protists
• There are seven major phyla of algae classified
  according to a variety of cellular
  characteristics
• The first four phyla, which contain unicellular
  organisms, are discussed in this section
• These four phyla are
• Euglenophytes
• Chrysophytes
• Diatoms
• Dinoflagellates
• The last three phyla include many multicellular
  organisms and will be discussed in the next
  section

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ALGAE

• Structure
• Thallus body of an alga
• Can be unicellular mostly aquatic (plankton)
• Photosynthetic plankton are called phytoplankton
• Generate enormous amounts of oxygen we breathe
• Provide food for numerous aquatic organisms in
  the food chain
• Colonial groups of independent cells that move
  and function as a unit
• Groups of individual cells that act in a
  coordinated manner
• Cell specialization movement,feeding, and
  reproduction
• Filamentous consist of cells in a linear
  arrangement
• Row of cells
• Some have structures that anchor them to the
  bottom of the aquatic environment
• Some have branching filaments
• Thalloid organisms in which cells divide in many
  directions to create a body that is multicellular
  and often modified into rootlike, stemlike, or
  leaflike parts
• Not organized into specialized tissues but can
  often be very large and complex
• Referred to as seaweeds

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ALGAE CLASSIFICATION

• Six Divisions based on
• Color distinctive colors depending on the
  photosynthetic pigments in their cells
• All contain the pigment chlorophyll a
• Different Divisions contain other forms of
  chlorophyll (b,c,d), each absorbing a different
  wavelength of light
• Food storage substances
• Composition of cell walls
• Method of reproduction

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ALGAE CLASSIFICATION
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ALGAE CLASSIFICATION
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Chlorophyll and Accessory Pigments

• One of the key traits used to classify algae is
  the type of photosynthetic pigments they contain
• As you will remember, light is necessary for
  photosynthesis, and it is chlorophyll and the
  accessory pigments that trap the energy of
  sunlight

90
Chlorophyll and Accessory Pigments

• Life in deep water poses a major difficulty for
  algaea shortage of light
• As sunlight passes through water, much of the
  light's energy is absorbed by the water
• In particular, sea water absorbs large amounts of
  the red and violet wavelengths
• Thus, light becomes dimmer and bluer, in deeper
  water
• Because chlorophyll a is most efficient at
  capturing red and violet light, the dim blue
  light that penetrates into deep water contains
  very little light energy that chlorophyll a can
  use

91
Chlorophyll and Accessory Pigments

• In adapting to conditions of limited light,
  various groups of algae have evolved different
  forms of chlorophyll
• Each form of chlorophyllchlorophyll a,
  chlorophyll b, and chlorophyll cabsorbs
  different wavelengths of light
• The result of this evolution is that algae can
  use more of the energy of sunlight than just the
  red and violet wavelengths

92
Chlorophyll and Accessory Pigments

• Many algae also have compounds called accessory
  pigments that absorb light at different
  wavelengths than chlorophyll
• Accessory pigments pass the energy they absorb to
  the algae's photosynthetic machinery
• Chlorophyll and accessory pigments allow algae to
  harvest and use the energy from sunlight
• Because accessory pigments reflect different
  wavelengths of light than chlorophyll, they give
  algae a wide range of colors

93
Euglenophytes

• Members of the phylum Euglenophyta, or
  euglenophytes, are closely related to the
  animallike flagellates
• Euglenophytes are plantlike protists that have
  two flagella but no cell wall
• Although euglenophytes have chloroplasts, in most
  other ways they are like zooflagellates

94
Euglenophytes

• The phylum takes its name from the genus Euglena
• Euglenas are found in ponds and lakes throughout
  the world
• A typical euglena, such as the one shown below,
  is about 50 micrometers in length
• Euglenas are excellent swimmers
• Two flagella emerge from a gullet at one end of
  the cell, and the longer of these two flagella
  spins in a pattern that pulls the organism
  rapidly through the water
• Near the gullet end of the cell is a cluster of
  reddish pigment known as the eyespot, which helps
  the organism find sunlight to power
  photosynthesis
• If sunlight is not available, euglenas can also
  live as heterotrophs, absorbing the nutrients
  available in decayed organic material
• Euglenas store carbohydrates in small storage
  bodies

95
Euglena Anatomy  

• Euglenophytes are plantlike protists that have
  two flagella but no cell wall
• The green structures inside the euglena shown are
  chloroplasts, which allow the organism to carry
  on photosynthesis
• Like paramecia, euglenas expel excess water
  through a contractile vacuole.

96
Euglena Anatomy  

• Euglenas do not have cell walls, but they do have
  an intricate cell membrane called a pellicle
• The pellicle is folded into ribbonlike ridges,
  each ridge supported by microtubules
• The pellicle is tough and flexible, letting
  euglenas crawl through mud when there is not
  enough water for them to swim
• Euglenas reproduce asexually by binary fission

97
Euglena Anatomy  
98
DIVISION EUGLENOPHYTA

• Euglenoids
• Approximately 1,000 species
• Unicellular
• Characteristic similar to algae and protozoa
• Contain chlorophyll a and b
• Store food as starch
• No cell wall
• Not completely autotrophic
• Placed in the dark will become heterotrophic
• Genus Euglena
• Freshwater
• Changes shape because of the presence of a
  pellicle, a flexible proteinaceous covering
• Flagella
• Long for locomotion
• Short in the reservoir (opening to the outside
  that contains a contractile vacuole )
• Eyespot light detector

99
EUGLENOID MOVEMENT
100
EUGLENA
101
EUGLENA
102
EUGLENA CONTRACTILE VACUOLE
103
FLAGELLUM 9 2 STRUCTURE
104
Chrysophytes

• The phylum Chrysophyta includes the yellow-green
  algae and the golden-brown algae
• The chloroplasts of these organisms contain
  bright yellow pigments that give the phylum its
  name
• Chrysophyta means golden plants
• Members of the phylum Chrysophyta are a diverse
  group of plantlike protists that have
  gold-colored chloroplasts

105
Chrysophytes

• The cell walls of some chrysophytes contain the
  carbohydrate pectin rather than cellulose, and
  others contain both pectin and cellulose
• Chrysophytes generally store food in the form of
  oil rather than starch
• They reproduce both asexually and sexually
• Most are solitary, but some form threadlike
  colonies

106
Diatoms

• Members of the phylum Bacillariophyta, or
  diatoms, are among the most abundant and
  beautiful organisms on Earth
• Diatoms produce thin, delicate cell walls rich in
  silicon (Si)the main component of glass
• These walls are shaped like the two sides of a
  petri dish or flat pillbox, with one side fitted
  snugly into the other
• The cell walls have fine lines and patterns that
  almost seem to be etched into their glasslike
  brilliance

107
DIVISION CHRYSOPHYTA

• Approximately 10,000 species
• Golden brown algae
• Majority are commonly called diatoms
• Contain chlorophylls a and c and the accessory
  pigment fucoxanthin
• Because of the pigment fucoxanthin, scientist
  suggest that the brown and golden-brown algae
  have a close evolutionary relationship
• Store food in the form of oil, not starch
• Diatoms are unicellular or colonial,
  nonflagellated, photosynthetic algae with
  silica-impregnated shells
• Both marine and freshwater
• Essential component of phytoplankton
• Marine forms are responsible for the bulk of
  worldwide photosynthesis
• Highly ornamented double walls containing silicon
  dioxide
• Two halves of the wall fit together like the two
  parts of a box
• Each half is called a valve
• Do not decompose
• Shells of dead diatoms sink and eventually form a
  layer of material called diatomaceous earth which
  is slightly abrasive (ingredient of many
  commercial products, such as detergents, paint
  removers, fertilizers, and insulators)

108
DIATOMS
109
DIATOMS
110
COMPARATIVE REPRODUCTION

• Unicellular reproduction
• Diatoms
• Asexual
• Two valves of the diatom shell split apart
• Each valve grows another valve within itself
• Sexual
• Diploid diatom undergoes meiosis to produce a
  gamete
• Plus and minus gametes unite to form a zygote
  that will grow into a mature diatom

111
Dinoflagellates

• Dinoflagellates are members of the phylum
  Pyrrophyta
• About half of the dinoflagellates are
  photosynthetic the other half live as
  heterotrophs
• Dinoflagellates generally have two flagella, and
  these often wrap around the organism in grooves
  between two thick plates of cellulose that
  protect the cell
• Most dinoflagellates reproduce asexually by
  binary fission

112
Dinoflagellates

• Many dinoflagellate species are luminescent, and
  when agitated by sudden movement in the water,
  give off light
• Some areas of the ocean are so filled with
  dinoflagellates that the movement of a boat's
  hull will cause the dark water to shimmer with a
  ghostly blue light
• This luminescent property gives the phylum its
  name, Pyrrophyta, which means fire plants

113
DINOFLAGELLATES
114
DINOFLAGELLATES
115
DIVISION PYRROPHYTA

• Fire algae (dinoflagellates)
• Approximately 1,100 species
• Most are marine and photosynthetic
• Important component of marine phytoplankton
• Cell walls are made of cellulose
• Most have two flagella
• Many have the ability to produce light
  (bioluminescence)
• Red Tide phenomenon Gonyaulax variety
• Discoloration of sections of the ocean caused by
  population explosion (algal blooms)
• Produce toxins that cause respiratory paralysis
  in vertebrates
• If people eat mussels that feed on these toxic
  dinoflagellates, they may suffer a severe
  neurotoxic reaction called mussel poisoning
  (potentially fatal)

116
BIOLUMINESCENT PYRROPHYTE
117
Ecology of Unicellular Algae

• Plantlike protists are common in both fresh and
  salt water, and thus are an important part of
  freshwater and marine ecosystems
• A few species of algae, however, can cause
  serious problems

118
Ecology of Unicellular Algae

• Plantlike protists play a major ecological role
  on Earth
• They are important organisms whose position at
  the base of the food chain makes much of the
  diversity of aquatic life possible
• They make up a considerable part of the
  phytoplankton
• Phytoplankton constitute the population of small,
  photosynthetic organisms found near the surface
  of the ocean
• About half of the photosynthesis that occurs on
  Earth is carried out by phytoplankton, which
  provide a direct source of nourishment for
  organisms as diverse as shrimp and whales
• Even such land animals as humans get nourishment
  indirectly from phytoplankton
• When you eat tuna fish, you are eating fish that
  fed on smaller fish that fed on still smaller
  animals that fed on plantlike protists

119
Algal Blooms 

• Many protists grow rapidly in regions where
  sewage is discharged
• These protists play a vital role in recycling
  sewage and other waste materials
• When the amount of waste is excessive, however,
  populations of euglenophytes and other algae may
  grow into enormous masses known as blooms
• These algal blooms deplete the water of
  nutrients, and the cells die in great numbers
• The decomposition of these dead algae can rob
  water of its oxygen, choking its resident fish
  and invertebrate life
• As a result, these microorganisms disrupt the
  equilibrium of the aquatic ecosystem

120
Algal Blooms 

• Great blooms of the dinoflagellates Gonyaulax and
  Karenia have occurred in recent years on the east
  coast of the United States, although scientists
  are not sure of the reason
• These blooms are known as red tides
• These species produce a potentially dangerous
  toxin
• Filter-feeding shellfish such as clams can trap
  Gonyaulax and Karenia for food and become filled
  with the toxin
• Eating shellfish from water infected with red
  tide can cause serious illness, paralysis, and
  even death in humans and fish

121
Plantlike Protists Red, Brown, and Green Algae

• Have you ever taken a walk along a rocky beach at
  low tide?
• As the water recedes, in many places it reveals a
  damp forest of green and brown plants clinging
  to the rocks
• These seaweeds have the size, color, and
  appearance of plants, but they are not plants
• They are actually algae
• Unlike the algae in the previous section, most of
  these algae are multicellular, like plants
• They also have reproductive cycles that are
  sometimes very similar to those of plants
• Many of them have cell walls and photosynthetic
  pigments that are identical to those of plants
• Many of these algae also possess highly
  specialized tissues

122
Plantlike Protists Red, Brown, and Green Algae

• The three phyla of algae that are largely
  multicellular are commonly known as red algae,
  brown algae, and green algae
• The most important differences among these phyla
  involve their photosynthetic pigments

123
Red Algae

• Red algae are members of the phylum Rhodophyta
  (roh-duh-FYT-uh), meaning red plants
• Red algae are able to live at great depths due to
  their efficiency in harvesting light energy
• Red algae contain chlorophyll a and reddish
  accessory pigments called phycobilins
• Phycobilins (fy-koh-BIL-inz) are especially good
  at absorbing blue light, enabling red algae to
  live deeper in the ocean than many other
  photosynthetic algae
• Many red algae are actually green, purple, or
  reddish black, depending upon the other pigments
  they contain
• Red algae are an important group of marine algae
  that can be found in waters from the polar
  regions to the tropics
• The highly efficient light-harvesting pigments in
  these algae enable them to grow anywhere from the
  ocean's surface to depths of up to 260 meters

124
DIVISION RHODOPHYTA

• Red algae
• Most of the approximately 4,000 species are
  marine and multicellular
• Multicellular forms are generally less than 1 m
  long
• A few unicellular species inhabit land and
  freshwater environments
• Survive at greater depths than any other algae
• Commonly grow at depths of 150 m
• Photosynthesis is capable at such depths because
  they contain chlorophylls a and d as well as
  accessory pigments called phycobilins
• Phycobilins absorb the violet, blue, and green
  light that penetrates the depths at which these
  algae grow
• Cell walls contain cellulose and are sometimes
  coated with a sticky substance called carageenan
• Carageenan is a polysaccharide used to produce
  cosmetics, gelatin capsules, and some cheeses
• Coralline algae deposit calcium carbonate in
  their cell walls
• Important component of coral reefs

125
Red Algae

• Most species of red algae are multicellular, and
  all species have complex life cycles
• Red algae lack flagella and centrioles
• Red algae also play an important role in the
  formation of coral reefs
• These microorganisms help to maintain the
  equilibrium of the coral ecosystem, providing
  nutrients from photosynthesis that nourish coral
  animals
• Coralline red algae provide much of the calcium
  carbonate that helps to stabilize the growing
  coral reef

126
RED ALGAE
127
Brown Algae

• Brown algae belong to the phylum Phaeophyta,
  meaning dusky plants
• Brown algae contain chlorophyll a and c, as well
  as a brown accessory pigment, fucoxanthin
• The combination of fucoxanthin and chlorophyll c
  gives most of these algae a dark, yellow-brown
  color
• Brown algae are the largest and most complex of
  the algae
• All brown algae are multicellular and most are
  marine, commonly found in cool, shallow coastal
  waters of temperate or arctic areas.

128
DIVISION PHAEOPHYTA

• Brown algae (pigment fucoxanthin)
• Multicellular and usually large
• Most of the approximately 1,500 species are
  marine
• Food produced is stored as laminarin, a
  carbohydrate with glucose units linked
  differently from those in starch
• Thallus composed of a holdfast, a stipe, and
  blades
• Holdfast anchors the thallus to rocks
• Stipe stemlike region
• Blade leaflike region modified for
  photosynthesis
• Cell walls contain alginic acid, a source of
  commercially important alginates
• Alginates are polysaccharides used to make gels
  for ice cream and other foods

129
Brown Algae

• The largest known alga is giant kelp, a brown
  alga that can grow to more than 60 meters in
  length
• Another brown alga called Sargassum forms huge
  floating mats many kilometers long in an area of
  the Atlantic Ocean near Bermuda known as the
  Sargasso Sea
• Bunches of Sargassum often drift on currents to
  beaches in the Caribbean and southern United
  States

130
Brown Algae

• One of the most common brown alga is Fucus, or
  rockweed, found along the rocky coast of the
  eastern United States
• Each Fucus alga has a holdfast, a structure that
  attaches the alga to the bottom
• The body of the alga consists of flattened
  stemlike structures called stipes, leaflike
  structures called blades, and gas-filled
  swellings called bladders, which float and keep
  the alga upright in the water
• The figure below shows the structures of a brown
  alga

131
Brown Algae

• Brown algae contain chlorophyll a and c, plus
  fucoxanthin, a brown pigment

132
Brown Algae
133
BROWN ALGAE
134
Green Algae

• Green algae are members of the phylum
  Chlorophyta, which means green plants in Greek
• Green algae share many characteristics with
  plants, including their photosynthetic pigments
  and cell wall composition
• Green algae have cellulose in their cell walls,
  contain chlorophyll a and b, and store food in
  the form of starch, just like land plants
• One stage in the life cycle of mossessmall land
  plants you will learn about in the next
  unitlooks remarkably like a tangled mass of
  green algae strands
• All these characteristics lead scientists to
  hypothesize that the ancestors of modern land
  plants looked a lot like certain species of
  living green algae
• Unfortunately, algae rarely form fossils, so
  there is no single specific fossil that
  scientists can call an ancestor of both living
  algae and mosses
• However, scientists think that mosses and green
  algae shared such a common algalike ancestor
  millions of years ago

135
DIVISION CHLOROPHYTA

• Green algae
• 7,000 species
• Can be unicellular, colonial, filamentous, or
  thalloid
• Most are aquatic
• Ancestors of plants in the Plant Kingdom
• Both have chloroplasts containing chlorophyll a
  and b
• Both store food as starch
• Both have cell walls made of cellulose

136
DIVISION CHLOROPHYTA

• Colonial algae
• Have some characteristics of multicellular
  organisms
• Gonium
• The simplest colonial green alga
• Colony one cell thick and shaped in a rectangle
• Volvox
• Round colony
• Containing up to 60,000 cells
• Exhibits division of labor
• Intercellular communication allows the
  coordination of the many cells
• Cells are connected by fine cytoplasmic strands
  that enable adjacent cells to chemically
  communicate with each other
• Spirogyra
• Filamentous green alga with unusual spiral
  chloroplasts that stretch from one end of the
  cell to the other
• Oedogonium
• Filamentous green alga
• Netlike chloroplasts
• Ulva
• Leaflike, photosynthetic body
• Thallus collapses during low tide to prevent
  water loss in the intertidal zone, the area
  between high and low tides

137
DIVISION CHLOROPHYTA

• Chlamydomonas
• Unicellular green algae
• Common in soil and freshwater
• Single cup-shaped chloroplast containing a
  pyrenoid where starch is synthesized
• Two anterior flagella
• Eyespot
• An area sensitive to light enabling the alga to
  move either toward or away from light

138
CHLAMYDOMONAS
139
DIVISION CHLOROPHYTA

• Desmids
• Unusual unicellular algae that live primarily in
  freshwater
• Presence can be used to indicate the degree of
  water pollution

140
DESMIDS
141
Green Algae

• Green algae are found in fresh and salt water,
  and even in moist areas on land
• Many species live most of their lives as single
  cells
• Others form colonies, groups of similar cells
  that are joined together but show few specialized
  structures
• A few green algae are multicellular and have
  well-developed specialized structures

142
Unicellular Green Algae 

• Chlamydomonas, a typical single-celled green
  alga, grows in ponds, ditches, and wet soil
• Chlamydomonas is a small egg-shaped cell with two
  flagella and a single large, cup-shaped
  chloroplast
• Within the base of the chloroplast is a region
  that synthesizes and stores starch
• Chlamydomonas lacks the large vacuoles found in
  the cells of land plants
• Instead, it has two small contractile vacuoles

143
CHLAMYDOMONAS
144
Colonial Green Algae 

• Several species of green algae live in
  multicellular colonies
• The freshwater alga Spirogyra forms long
  threadlike colonies called filaments, in which
  the cells are stacked almost like aluminum cans
  placed end to end
• Volvox colonies are more elaborate, consisting of
  as few as 500 to as many as 50,000 cells arranged
  to form hollow spheres
• The cells in a Volvox colony are connected to one
  another by strands of cytoplasm, enabling them to
  coordinate movement
• When the colony moves, cells on one side of the
  colony pull with their flagella, and the cells
  on the other side of the colony have to push
• Although most cells in a Volvox colony are
  identical, a few gamete-producing cells are
  specialized for reproduction
• Because it shows some cell specialization, Volvox
  straddles the fence between colonial and
  multicellular life

145
SPIROGYRA
146
MULTICELLULAR REPRODUCTION

• Spirogyra Division Chlorophyta filamentous
  green alga
• Sexual reproduction Conjugation
• Two filaments align side by side
• Walls between the adjacent cells then dissolve
  and a conjugation tube forms between the cells
• One cell is considered to be a plus gamete
• One gamete moves to the other through a
  conjugation tube between adjacent filaments
  fusing with the minus gamete
• Fertilization forms a zygote which develops a
  thick wall, falls from the parent filament, and
  becomes a resting spore
• Resting spore later produces a new filament

147
SPIROGYRA CONJUGATION
148
MULTICELLULAR REPRODUCTION

• Oedogonium Division Chlorophyta filamentous
  green alga
• Has cells specialized for producing gametes
• Modified cells that produce and hold the gametes
  are called unicellular gametangia
• Male unicellular gametangium antheridium
  produces sperm
• Female unicellular gametangium oogonium produces
  an egg
• Flagellated sperm are released from the
  antheridium into the surrounding water, swim to
  an oogonium, and enter through small pores
  fertilizing the egg and forming a zygote
• Zygote is released from the oogonium and forms a
  thick-walled, resting spore
• Diploid spore undergoes meiosis, forming 4
  haploid zoospores that are released into the
  water
• Each zoospore settles and divides
• One of the cells will become an anchoring
  holdfast the others will divide and form a new
  filament

149
OEDOGONIUM REPRODUCTION
150
Multicellular Green Algae 

• Ulva, or sea lettuce, is a bright-green marine
  alga that is commonly found along rocky seacoasts
• Ulva is a true multicellular organism, containing
  several specialized cell types
• Although the body of Ulva is only two cells
  thick,