Notes on Chapter 19
Protists are usually classified by what they are not: they are not animals, plants, or fungi.
They belong to the Kingdom Protista which was created to include this diverse group of over
200,000 organisms
All protists are eukaryotes. Eukaryotic cells contain membrane-bound organelles
Like all eukaryotes, the DNA of protists is found within the membrane-bound nucleus.
Some protists reproduce asexually by mitosis, while others exchange genetic material during
meiosis.
Because they are such a diverse group of organisms, some scientists classify protists by their
method of obtaining nutrients.
Protists are divided into three groups using this method:
Animal like protists, Plant like protists, and Fungus like protists
The protozoan is an example of an animal-like protist because it is a heterotroph
An amoeba is an example of a unicellular animal-like protist or protozoan. Protozoans are
heterotrophs and usually ingest bacteria, algae, or other protozoans
A giant kelp is an example of a plantlike protist that makes its own food through
photosynthesis. Plantlike protists are commonly referred to as algae.
The water mold is an example of a funguslike protist that can absorb nutrients from a dead
salamander.
Funguslike protists are similar to fungi because they absorb their nutrients from other
organisms.
Fungus and funguslike protists differ in the composition of their cell wall, and funguslike
protists contain centrioles (small, cylindrical organelles.
Animal-like protists (Protozoan)
Ciliates, amoebas, apicomplexans, and zoo flagellates
Plantlike protists (Algae)
Euglenoids, diatoms, dinoflagellates, green algae, red algae, brown algae, yellowgreen algae, and golden-brown algae
Funguslike protists
Slime molds, water molds, and downy mildews
Animal-like protists (Protozoan)
Considered animal-like because they consume other organisms for food
Some are parasites
Plantlike protists (Algae)
Considered plantlike because they make their own food through photosynthesis
Some consume other organisms or are parasites when light is unavailable for
photosynthesis.
Funguslike protists
Considered funguslike because they feed on decaying organic matter and absorb
nutrients through their cell walls.
Some slime molds consume other organisms and a few slime molds are parasites
Protists typically are found in damp or aquatic environments such as decaying leaves, damp
soil, ponds, streams, and oceans.
Protists also live in symbiotic relationships (a close ecological relationship)
Microsporidia are microscopic protozoans that cause disease in insects
The theory of endosymbiosis suggests that eukaryotes, including protists, formed when a
large prokaryote engulfed a smaller prokaryote.
The two organisms lived symbiotically and eventually the organisms evolved into a single,
more highly developed organisms.
Ciliphora
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Members of the phylum Ciliphora, also known as ciliates, are animal-like protists that have
numerous short, hairlike projections called cilia.
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Some ciliates have cilia covering their entire plasma membrane, while others have groups of
cilia covering parts of their membrane.
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Ciliates are abundant in most aquatic environments such as ocean waters, lakes, and rivers.
Paramecia
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Some of the most commonly studied ciliates are found in the genus Paramecium.
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The paramecium lives symbiotically with green algae.
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The green algae undergo photosynthesis, providing nutrients to the paramecium.
A paramecium is a unicellular protozoan. It is enclosed by a layer of membrane called a pellicle
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Directly beneath the pellicle is a layer of cytoplasm called ectoplasm.

Embedded in the ectoplasm are the trichocysts, which are elongated, cylindrical bodies that
can discharge a spine like structure.
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The function of the trichocysts is not completely understood, but they might be used for
defense, as a reaction to injury, as an anchoring device, or to capture prey.

The cilia on the paramecium are used for movement and feeding. Cilia completely cover the
entire organism, including the oral groove.

The cilia around the oral groove (collects food) are used to guide food, primarily bacteria into
the gullet.
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Once the food reaches the end of the gullet (little tube where the food goes down), it is
enclosed in a food vacuole (storage pocket for food).

Enzymes within the food vacuole break down the food into nutrients that can diffuse into the
cytoplasm of the paramecium.

Waste products from the paramecium are excreted through the anal pore.
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The paramecium has two nuclei; the macronucleus which operates as the director of the cells
activities, and the micronucleus which is used for reproduction. The paramecium reproduces
by fission.
Contractile Vacuoles
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Because freshwater paramecia live in a hypotonic environment (lower concentration of solute
outside the cell than inside the cell), water constantly enters the cell by osmosis.
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The contractile vacuoles collect the excess water from the cytoplasm and expel it from the
cell.
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Paramecia often have two or three contractile vacuoles that help to maintain homeostasis in
the cell.
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Ciliates reproduce asexually by binary fission. During this process, the macronucleus
elongates and splits rather than undergoing mitotic division.
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Most ciliates maintain genetic variation by undergoing conjugation – a sexual process in which
genetic information is exchanged.
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Genetic variation is increased in paramecia through conjugation.
Sarcodina
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Members of the phylum Sarcodina, also called sarcodines, are animal-like protists that use
pseudopods for feeding and locomotion.
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A pseudopod is a temporary extension of cytoplasm. These extensions surround end envelop
a smaller organism, forming a food vacuole.
Some of the most commonly studied sarcodines are found in the genus Amoeba
Amoebas
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Most amoebas are found in salt-water, although some freshwater species live in streams, in
the muddy bottoms of ponds, and in damp patches of moss and leaves.
Some amoebas are parasites that live inside an animal host

Amoebas are enveloped in an outer cell membrane and an inner thickened cytoplasm called
ectoplasm.

Inside the ectoplasm, the cytoplasm contains the nucleus, food vacuoles, and occasionally a
contractile vacuole (which regulate the water in amoeba).

Waste products and undigested food particles are excreted by diffusion through the cell
membrane.
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Foraminiferans and radiolarians are types of amoebas that have tests.

A test is a hard, porous covering similar to a shell, which surrounds the cell membrane.
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Most of these amoebas live in marine environments although there are some freshwater
species.

Foraminiferans have tests made of calcium carbonate (CaCO3), grains of sand, and other
particles cemented together.

Geologists used the fossilized remains of foraminiferans to determine the age of some rocks
and sediments, and to identify possible sites for oil drilling.
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Radiolarians have tests made mostly of silica (SiO2).
Apicomplexa
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Animal-like protists that belong to the phylum Apicomplexa are also known as sporozoans.
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They are called sporozonas because they produce spores at some point in their life cycle.
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Spores are reproductive cells that form without fertilization.
Sporozoans lack contractile vacuoles and methods for locomotion
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Respiration and excretion occur by diffusion through the plasma membrane.
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All sporozoans are parasitic. Parasites are organisms that get their nutritional requirements
from a host organism. Sporozoans infect vertebrates and invertebrates by living as internal
parasites.
Organelles at one end of the organism are specialized for penetrating host cells and tissues
•
The life cycle of sporozoans has both sexual and asexual stages. Often two ore more hosts are
required for an organism to complete a life cycle.
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Plasmodium is a sporozoan which causes Malaria (which infects and destroys red blood cells
which leads to fever and flu-like symptoms). Malaria is transmitted by a female Anopheles
mosquito.
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Sporozoans cause a variety of illnesses in humans, some of which are fatal.
Zoomastigina
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Protozoans in the phylum Zoomastigina are called zooflagellates.
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Zooflagellates are animal-like protozoans that use flagella for movement.
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Flagella are long whiplike projections that protrude from the cell and are used for movement.
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Some zooflagellates are free living, but many are parasites

At least three species of zooflagellates from the genus Trypanosoma cause infectious diseases
in humans that are often fatal because of limited treatment options.
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One species found in Central and South America causes Chagas’ disease, sometimes called
American sleeping sickness (an inflammatory, infectious disease which can lead to serious
heart and digestive problems).
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The zooflagellate that causes Chagas’ disease is similar to the sporozoan that causes malaria.
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The reduviid bug serves as one host for the protist in Central and South America.
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The reduviid bug gets its nutrients from sucking blood from a human host. During the feeding
process, the zooflagellate pass out of the reduviid body through its feces.
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The zooflagellates enter the human body through the wound site or mucus membranes. Once
it enters, it multiplies in the bloodstream and can cause heart, liver, and spleen damage.
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Also causes African Sleeping Sickness carried by the tsetse fly, the Zoomastigina reproduces in
the gut of the fly then migrates to the salivary gland. Once the tsetse fly bites the human the
zooflagellate causes fever, inflammation of the lymph nodes and damage the nervous system.
Algae-Plantlike Protists
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Autotrophic producers for aquatic ecosystems
Use pigments to produce food by using the energy of the sun.
Pigments found in chloroplasts
o Primary pigment is chlorophyll
o Secondary pigments allow algae to absorb sunlight in deeper water
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Can be unicellular or multicellular
Unicellular algae referred to as phytoplankton and provide the base of the food web
Provide much of the oxygen in the atmosphere
Classification of Algae
o Type of chlorophyll and secondary pigments
o Method of food storage
o The composition of the cell wall
Diatoms
o Unicellular
o Phylum Bacillariophyta
o Shape two unequal halves fit together to form small box
o Autotrophic
o Primary pigment chlorophyll and secondary pigment: carotenoids which give them their
golden-yellow color
o Store their food as oil instead of carbohydrates which gives them buoyancy
o Main source of food for marine animals
o Reproduce sexually and asexually
 Asexual reproduction occurs when two separated halves each create a new half
that can fit inside the old one.
 Produces smaller diatoms, when one-third size triggers
 Sexual reproduction
 Gametes are produced
 Gametes fuse to form a zygote that develops into a full sized diatom
 Reproduction cycle repeats
o Diatoms have hard silica walls
 Silica walls accumulate on ocean floor to form sediment known as
diatomaceous earth
 This is collect and used as an abrasive and a filtering agent
 Found in tooth polishes, metal polishes
Dinoflagellates
o Phylum Pyrrophyta
o Unicellular
o Have two flagella at right angles to each other spin and beat and are used to move
through the water
o Cell walls made of thick cellulose plates that resemble helmets or sheets of armor
o Some members are bioluminescent which means that they omit light
o Few are freshwater most live in salt water
o Photosynthetic
o Major component of photoplankton
o Some are photosynthetic autotrophs
o Some are heterotrophic which can be carnivorous, parasitic or mutualistic
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Mutualistic dinoflagellates have relationships with organisms such as jellyfishes,
mollusks, and corals
o Algal Bloom
 Occurs when food is plentiful and environmental conditions are favorable,
reproduce in great numbers
 Can be harmful when food is depleted they die in great number and as they
decompose the oxygen supply in the water is depleted suffocating fish and
other marine organisms
o Red Tides
 Occurs when dinoflagellates with red pigments goes through an algal bloom it
produces this
 Threat to humans because they produce a potentially lethal nerve toxin which
affects people when they eat shell fish that filtered water in which these algal
bloom occur.
Euglenoids
o Phylum Euglenophyta
o Unicellular
o Most shallow freshwater
o Have characteristics of both plant and animal
o Most contain chloroplasts but lack a cell wall
o They can be heterotrophs, when light in not available, they absorb dissolved nutrients
from their environment, or other smaller organisms
o Few species parasitic
o Instead of cell wall they have a flexible tough outer membrane called a pellicle, which
allows them to crawl through mud when water level to low
o Flagella used to propel toward light or food
o Eyespot is a light-sensitive receptor that helps orient them toward light for
photosynthesis
o Contractile vacuole serves the same purpose as it does in the paramecium which expels
excess water from the cell to maintain homeostasis inside the cell
Yellow-green and Golden Brown Algae
o Phylum Chrysophyta
o Called Chrysophytes
o Secondary pigment are yellow and brown carotenoids
o Most unicellular
o Some members form colonies: a group of cells that join together to form a close
association
o Contain two flagella attached at one end
o All are photosynthetic but some can absorb dissolved organic compounds through their
cell walls or ingest food particles
o Reproduce asexually and sexually though sexually is rare
o Components of fresh and salt water plankton
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Brown Algae
o Phylum Phaeophyta
o Largest multicellular plantlike algae
o Secondary pigment called fucoxanthin
o Live along rocky coasts in cool areas
o Kelp is example
o Thallus is the body of the kelp
o The blades are the flattened portions
o The stipes is the stalklike part
o The holdfast is the rootlike structure
o The bladder is the bulging portion of the algae, which is filled with air and keeps the alga
floating near the surface of the water where light is available for photosynthesis
Green Algae
o Phylum Chlorophyta
o Contains more than 7000 species
o Contain chlorophyll as primary pigment
o Have cell walls
o Store food as carbohydrates
o Evolutionary link between protists and plants kingdom
o Most species found in freshwater, but 10% are salt water
o Also found on rock, trees, snow and fur of some animals
o Unicellular algae called Desmids are characterized by their symmetrically divided cells
that resembles a bridge
o Spirogyra is a multicellular green algae characterized by its long, thin filaments,
o Volvox is an algae that has a colonial growth held together by a gelatin like secretion
called cytoplasmic strands
 Each cell has a flagella that beat in unison to move the colony
 Colonies can by hundreds to thousands
 Smaller colonies inside the larger ones are called daughter colonies and when
they mature they digest the parental cell and become free swimming
Red Algae
o Phylum Rhodophyta
o Multicellular
o Secondary pigment called phycobilins which allows them to absorb green, violet, and
blue light
o This allows them to live in deeper waters than other algae
o Some also contribute to the formation of the coral reefs. The cell wall of the red algae
Coralline contains calcium carbonate which binds together the bodies or other
organisms called stony coral to form coral reefs
Uses of Algae
o Major source of food for animals and people, food supplement for farm animals,in
processed foods
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o
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Algae are high in protein and minerals, trace elements, and vitamins
Also used to stabilize or improve texture of processed foods, without adding fat to the
products
o Look on page 559 for uses in chart
Life Cycles of Algae
o Alternate between spore-producing forms and gamete-producing forms
 Haploid (n)
 Diploid (2n)
o Green algae can reproduce asexually through fragmentation, a process by which a
multicellular individual breaks into separate pieces and each grows into an individual
organism
o Haploid form is called the gametophyte generation because it produces gametes
 Generation begins with spores and ends with male and female gametes
 Gametes from two different organisms combine to form a zygote with two
complete sets of chromosomes
o Diploid form begins with fertilization and ends when the sporophyte creates spores
 The zygote develops into the sporophyte (2n)
 Some cells divide by meiosis and become haploid spores (n)
 Spores are reproductive cells that develop into gametophytes