Advanced Biology

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Advanced Biology

• Chapter 26 Protozoa

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Chapter 26 Protozoa

• 26-1 Overview of Protozoa
• 26-2 Protozoan Diversity

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Section 26-1 Overview of Protozoa

• Characterisitcs of Protozoa
• Reproduction
• Classification
• Adaptations
• Evolution
• Great Discoveries

Paramecium
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Characteristics of Protozoa

• Single-celled, microscopic
• Eukaryotes
• Able to move independently
• 65,000 species identified

Stentor
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Characteristics of Protozoa

• Inhabit many environments
• Salt and fresh water
• Soil
• In bodies of other organisms (parasitic with
  complex life-cycles)
• Heterotrophic obtain nutrients by ingesting
  small molecules or cells and digest it in a food
  vacuole that contains digestive enzymes.

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Characteristics of Protozoa

• Zooplankton a population of organisms that
  constitute one of the primary sources of energy
  in aquatic ecosystems.

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Reproduction

• Asexual reproduction by binary fission divides
  into 2 essentially identical individuals
• Some by multiple fission cell division that
  results in a number of identical individuals

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Reproduction

• Sexual reproduction in the form of conjugation
  individuals from opposite mating strains pair and
  exchange genetic material.

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Classification

• Protozoa are members of Kingdom Protista along
  with algae, slime molds, and water molds

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Classification

• Research into evolutionary relationships is
  constantly yielding new information and altering
  Protistan classification

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Classification

• Sometimes classified into 4 phyla based on means
  of locomotion
• Sarcodina (Sarcodines) pseudopodia
• Ciliophora (Ciliates) cilia
• Zoomastigina (Zooflagellates) flagella
• Sporozoa (Sporozoans) non-motile adults

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Adaptations

• Many species have physiological mechanisms for
  monitoring conditions in their environment
• Eyespot localized region of pigment that detects
  changes in the quantity and quality of light.
• Others can sense physical and chemical changes or
  obstacles in their environment

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Adaptations

• Cyst a dormant form characterized by a hardened
  external covering in which metabolic activity has
  ceased.
• Form in response to nutrient deficiency, drought,
  and decreased oxygen concentration, or pH or
  temperature changes.
• Emerge when conditions improve

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Evolution

• First life forms 3.5 billion years ago were
  prokaryote (bacteria), then 1.5 billion years ago
  the first eukaryotic organisms evolved. Protozoa
  are the descendants of these early eukaryotes

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Evolution

• Probably evolved through endosymbiosis a process
  in which one prokaryote lives inside another and
  gradually both host and guest become dependent on
  one another.

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Great Discoveries The Origin of Eukaryotic Cells
p510-511

• Lynn Magulis -Symbiosis of Cell Evolution
• Animation/tutorial

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Mitochondria and chloroplasts are

• Self-dividing
• Approximately the same size as prokaryotes
• Able to make proteins and lipids
• DNA within are similar to bacteria DNA rather
  than eukaryotic DNA

• Ribosomes within are more similar to those in
  prokaryotes in size and are sensitive to
  antibiotics like bacteria
• Synthesize protein using metabolic steps that
  bacteria use
• Chloroplast produce energy in the same way that
  some bacteria produce energy

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Great Discoveries The Origin of Eukaryotic Cells
p510-511

• Kwang Jeon infected a species of amoeba with
  bacteria parasite. Cultured amoebas that survived
  infection, producing a line of amoebas dependent
  on the bacteria for survival.

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26-2 Protozoan Diversity

• Phylum Sarcodina
• Phylum Ciliophora
• Phylum Zoomastigina
• Phylum Sporozoa

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Phylum Sarcodina
Amoeba

• 40,000 species 100s of species of amoebas
• Inhabit fresh water, salt water, soil
• Ex. Pelomyxa carolinensis live on mud and rocks
  in shallow, slow-moving streams or ponds.

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Pseudopodia

• Large, rounded cytoplasmic extensions (flexible
  cell membranes) that function in movement.
• Forms when the endoplasm (inner portion of
  cytoplasm) pushes the ectoplasm (outer portion)
  forward to create a blunt arm-like extension.
• Other pseudopodia retract and cytoplasm flows in
  direction of new pseudopodium

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• Referred to as ameboid movement a form of
  cytoplasmic streaming
• Pseudopodia also used for feeding engulf other
  Protists by phagocytosis surrounds food with
  its pseudopodia and a portion of the cell
  membrane then pinches together and encloses the
  food vacuole in a process called endocytosis,
  then enzymes from the cytoplasm enter vacuole and
  digest the food.
• Wastes leave cell in reverse process called
  exocytosis.

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• Phagocytosis animation

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Contractile vacuole

• An organelle that expels fluid from the cell.
• Freshwater organisms are usually hypertonic
  relative to their environment so water
  continually diffuses into them.
• To maintain homeostasis, it must use contractile
  vacuole to rid cell of excess water.

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Ecological Role Foraminifera and Radiolarians

• Test protective shell made of calcium carbonate
  (foraminifera) or silicon dioxide (radiolarians).
  Slender pseudopodia extend through opening in
  test.

Foraminifera and Radiolarians
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• Existed since Precambrian times leaving an
  excellent fossil record. Tests of dead organisms
  have been sinking to the bottom of the ocean for
  millions and millions of years.
• Foraminifera have built up a calcium-rich layer
  of sediment that has created limestone and chalk
  deposits. Ex. White Cliffs of Dover, England and
  the Great pyramids of Egypt
• Radiolarians formed a type of rock called chert

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Human Diseases from Sarcodina

• Most are free-living, some live in the intestines
  of humans or other animals
• Entamoeba histolytica (amoebic dysentery)
• Enters body via contaminated food and water.
• Lives in the large intestine and secretes enzymes
  that attack the intestinal lining and cause deep
  ulcers.
• Affected individuals feel intense pain and
  complications arise when amoebas are carried by
  blood to the liver and other organs.

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Phylum Ciliophora
Paramecium

• 8,000 species
• Swim by means of cilia short, hair-like
  cytoplasmic projections that line the cell
  membrane.
• Example Paramecium abundant in ponds,
  slow-moving streams that contain plants and
  decaying organic matter

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Phylum Ciliophora
Zoothamnium

• Cilia beat in synchronized strokes that pass
  waves across the cell causing the protozoan to
  rotate on its axis.
• Feed on bacteria, algae, and other small
  organisms found in marine and fresh water
  habitats.

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Internal Structure

• Pellicle clear, elastic layer of protein
  surrounds the cell membrane
• Oral groove funnel-like depression lined with
  cilia. Beating cilia create water currents that
  sweep food down groove to mouth pore and gullet
  where food vacuole forms.

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• Anal pore where waste is expelled
• Multinucleated have at least one macronucleus
  and one micronucleus.
• Macronucleus contains multiple copies of DNA and
  is responsible for metabolic and developmental
  functions necessary for asexual reproduction.
• Micronucleus participates in exchange of genetic
  info during conjugation.

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Reproduction in Ciliophora

• Asexual reproduction by binary fission
• Only the micronucleus divides by mitosis.
• Macronucleus which has up to 500x more DNA than
  the micronucleus, simply elongates and splits in
  half. One goes into each new cell

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• Sexual reproduction by Conjugation
• Two organisms of opposite mating strains line up
  and join together.
• Macronucleus disintegrates
• Each diploid micronucleus undergoes meiosis,
  producing 4 haploid micronuclei. All but one
  disintegrates.
• Remaining micronuclei divides by mitosis
  producing 2 identical haploid micronuclei.
• Two paramecium exchange 1 micronuclei

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• The 2 micronuclei in each fuse to form one
  diploid micronucleus in each paramecium.
• Paramecium separate.
• Macronucleus forms in each from products of
  mitotic divisions of the micronucleus.
• Although genetic material was exchanged no new
  cells are produced.
• Following conjugation, each paramecium divides,
  producing a total of 4 genetically identical
  paramecia which are genetically different from
  either of the original paramecia.

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Phylum Zoomastigina
Trichomonas

• 2500 species
• Characterized by presence of one or more
  flagella long hair-like structures that are made
  up of microtubules and are used for movement.
• rapid whipping motion pushes or pulls protozoan
  through water

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Phylum Zoomastigina

• Many are free-living in ponds or lakes and feed
  on small organisms.

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Phylum Zoomastigina

• Example Giardia lamblia (giardiasis)
• Severe diarrhea, intestinal cramps.
• Several kinds of animal carry parasite and
  contaminate water with their feces.

Trichonympha live in the gut of termites and help
digest cellulose.
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Human Disease of Zoomastigina

• Genus Trypanosoma
• live in blood of fish, amphibians, reptiles,
  birds, and mammals.
• Carried from host to host by bloodsucking insects
  
• African trypanosomiasis sleeping sickness.
  Transmitted by tsetse fly. Causes fever,
  lethargy, mental disorientation, coma
• Trypanosoma cruzi Chagas disease. Transmitted
  by kissing bug. Fever and severe heart damage.

Trypanosoma
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• Leishmania donovani
• Transmitted by sand fleas.
• Causes leishmaniasis.
• Blood disease afflicts millions of people in
  Africa, Asia and Latin America.
• Disfiguring skin sores, can be fatal.

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Phylum Sporozoa
Plasmodium

• 6,000 species
• No means of locomotion in adults

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Phylum Sporozoa

• Most species are parasitic
• Have complex life cycles in which they develop a
  spore
• Infective form protected by a resistant coat
• Carried in the blood and other tissues of their
  hosts where they absorb nutrients and destroy
  host tissues.

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Example Toxoplasma gondii

• Found in birds, rodents, and domestic cats.
• Causes toxoplasmosis.
• Few to no symptoms in healthy adults but can
  cause damage to developing fetus or newborn.

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Example Plasmodium

• Causes malaria.
• Characterized by severe chills, fever, sweating,
  fatigue, and great thirst.
• Victims die of anemia, kidney failure or brain
  damage.
• Four species infect humans. All have life cycles
  that involve the female Anopheles mosquito.

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Life Cycle of Plasmodium

• When an infected mosquito bites a person,
  Plasmodium sporozoites enter bloodstream and
  travel to liver cells where they divide
  repeatedly.
• New spores called merozoites emerge and infect
  red blood cells where they reproduce asexually.
• At regular intervals, the merozoites burst out of
  the RBCs and release toxins into the blood.

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• Destruction of RBCs and release of toxins in
  blood causes fever, anemia, and other symptoms.
• Merozoites infect other RBCs and again reproduce
  asexually many times over a long period of time.
• Infected person can take antimalarial drugs and
  be cured of blood infection, but become ill again
  when merozoites leave liver cells. Other
  antimalarial drugs have been developed to kill
  the liver-stage parasites.
• Some merozoites in blood develop into specialized
  cells called gametocytes which are taken up by a
  female Anopheles mosquito that bites an infected
  person.

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• In mosquitos digestive system the sperm and eggs
  (of the gametocytes) combine to form a zygote.
• The nucleus of the zygote divides repeatedly to
  form more sporozoites.
• When zygote bursts, sporozoites migrate to the
  body cavity and salivary glands of the mosquito.
• When infected mosquito bites another person the
  cycle begins again.

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Treating Malaria

• An effective way to reduce human deaths from
  malaria is to control mosquito population and
  interrupt the parasites life cycle.
• Cured with drug derived from Cinchona tree,
  native to Americas. Quinine used for over 500
  years.
• Sporozoans resistance to antimalarial drugs is a
  significant worldwide problem. Possible
  vaccination developed in the future.

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