Protozoa
Animal like Protists- Zooflagelletes , Sarcodines, Ciliophorans and Spororzoans
Characteristics:
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Eukaryotes
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Found in kingdom Protista
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Most are unicellular
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Heterotrophs that ingest small food particles & digest it inside food vacuoles containing
digestive enzymes
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Classified by the way they move (cilia, flagella, pseudopodia...)
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Microscopic in size
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65,000 identified species with almost half extinct
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Found in freshwater, marine, and moist terrestrial habitats
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Make up part of the zooplankton & serve as food for animals in marine & freshwater systems
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First seen by Leeuwenhoek in 1675
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Many species are free living
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Some species are parasitic living in the bloodstream of their host & cause malaria, amebic
dysentery, or giardiasis
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Many serve as food for other organisms in aquatic habitats; called zooplankton
Reproduction:
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All reproduce asexually by binary fission (single protozoan divides into two individuals)
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Some species reproduce by multiple fission producing more than two individuals
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Some species reproduce sexually by conjugation (opposite mating strains join & exchange
genetic material)
Adaptations:
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Eyespots in some protozoans can detect changes in light
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Many can form harden covering called cyst when conditions become unfavorable (no water, pH
or temperature changes, nutrient deficiency, decreased oxygen supplies…)
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Metabolic activity of protozoans resumes when conditions become favorable again
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Some protozoans can detect & avoid obstacles and harmful chemicals in their environment
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Freshwater protozoa have contractile vacuoles to pump out excess water
Classification:
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Divided into 4 phyla based on their method of movement --- Sarcodina, Ciliophora,
Zoomastigina, & Sporozoa
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Found in the kingdom Protista along with algae, slime molds, & water molds
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Sarcodinians move by extending their cytoplasm or pseudopodia (fingerlike projections of the
cytoplasm)
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Zooflagellates move by whip like flagella
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Ciliophorans or ciliates move by hair like cilia move
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Sporozoans are nonmotile
Phylum
Sarcodina
Ciliophora
Common Name Locomotion
Type of Nutrition Examples
sarcodines
pseudopodia
heterotrophic;
some parasitic
Amoeba
Radiolaria
Naegleria
cilia
heterotrophic;
some parasitic
Paramecium
Tetrahymena
Balantidium
ciliates
Zoomastigina zooflagellates
flagella
heterotrophic;
some parasitic
Trypanosoma
Leishmania
Giardia
Trichonympha
Sporozoa
(None in Adults)
heterotrophic;
some parasitic
Plasmodium
Toxoplasma
sporozoans
Protozoan Evolution:
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First eukaryotic organism thought to have evolved about 1.5 billion years ago
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Protozoans possible evolved from the 1st eukaryotes by Endosymbiosis
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Endosymbiosis – process where one prokaryote lives inside another becoming dependent upon
each other
Phylum Sarcodina:
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Includes hundreds of species of amebas
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Found in freshwater, marine, & moist soil habitats
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Usually reproduce asexually
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Their cytoplasm consists of clear, outer ectoplasm and granular, inner endoplasm
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Move by extending cytoplasm (cytoplasmic streaming)
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Cytoplasm extensions are called “false foot” or pseudopods
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Pseudopods form when the inner cytoplasm or endoplasm pushes the outer cytoplasm or
ectoplasm forward to make a blunt, armlike extension
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Ameba move by cytoplasmic streaming to produce pseudopods; process called ameboid
movement
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Sarcodines also use their pseudopods for feeding by surrounding & engulfing food particles &
other protists; called phagocytosis
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Food is surrounded by a pseudopod & then this part of the cell membrane pinches together
forming a food vacuole; called endocytosis
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Cytoplasmic enzymes enter the food vacuole & digest the food
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Undigested food & wastes leave by exocytosis
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Most Sarcodinians have contractile vacuoles to pump out excess water
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Oxygen & carbon dioxide diffuse through the cell membrane
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Sarcodinians may form hard, protective, inactive cysts when conditions become unfavorable
(drought, lack of nutrients, heat…)
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React to stimuli such as light
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Some Sarcodinians have hard shells called the test made of silica or calcium carbonate
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Radiolarians found in warm, marine waters have a test made of silica & have sticky
pseudopodia to trap food
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Marine Foraminiferans have a test made of calcium carbonate with holes through which
pseudopodia extend
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Foraminiferan tests build up and form limestone or chalk (e.g. White Cliffs of Dover)
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Important food source in marine habitats
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Entameba histolytica cysts in untreated water supplies cause amebic dysentery which can be
fatal
Phylum Ciliophora:
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Called ciliates because they move by short, hairlike cilia lining the cell membrane
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Cilia may be modified into teeth, paddles, or feet
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Largest group of protozoans
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Most found in freshwater, but some are marine
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Called plankton & serve as a food source
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Form protective cysts to survive unfavorable conditions
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Members include the Paramecium, Vorticella, & Stentor
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Have 2 types of nuclei --- smaller micronuclei & larger macronuclei
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Macronucleus controls asexual reproduction by mitosis
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Can reproduce sexually by conjugation (two paramecia join together & exchange DNA)
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Gases diffuse across cell membrane
Stentor:
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Trumpet shaped protozoan with cilia around the top
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Attaches to feed & then detaches to swim around
Vorticella:
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Cup shaped protozoan with cilia at the top
Has a coiled stalk to raise & lower the organism
Can attach to surfaces
Paramecium caudatum:
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Slipper shaped protozoan found in freshwater
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Clear, elastic covering of cell membrane called pellicle
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Pellicle made of protein for protection
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Use cilia to swim & obtain food (algae & bacteria)
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Have 2 contractile vacuoles to pump out excess water
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Cilia sweep food into oral groove where mouth located at the bottom
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Food enters short tube called gullet into food vacuoles where it’s digested
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Wastes leave through anal pore
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Have trichocysts (tiny, toxic darts to help capture prey or anchor to a surface)
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Respond to light & learn by trial & error
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Reproduce asexually by mitosis & sexually by conjugation
Phylum Zoomastigina:
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Called Zooflagellates because have one or more whiplike flagella to move
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Flagella made of bundles of microtubules
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May be freshwater or marine
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Some are parasites such as Trypanosoma that destroy red blood cells & causes fatal African
sleeping sickness
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Trichonympha lives symbiotically inside termites & digests cellulose
Phylum Sporozoa:
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Adult sporozoans have no structures for movement
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Form spores
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Most are parasitic using one or more hosts
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Immature sporozoans are called sporozoites & live in body fluids of hosts
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Plasmodium is transmitted by mosquitoes & causes malaria
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Plasmodium sporozoites enter the bloodstream, travel to the liver, divide & form spores called
merozoites
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Merozoites attack red blood cells & later form eggs & sperm that fertilize
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New sporozoites migrate to the salivary glands of mosquitoes where they can be passed on to
another person
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Malaria can be controlled by controlling mosquito populations & it is treated with a drug called
quinine derived from the Cinchona Tree
Algal & Fungal-like Protists Copyright © by Holt, Rinehart and Winston
Kingdom Protista
Algal-Like Protists
Characteristics of Algae:
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Plantlike members of the kingdom Protista
Eukaryotes
Most unicellular, but some multicellular
Autotrophic – contain chlorophyll & make food by photosynthesis
Plankton = communities of organisms, mostly microscopic, that drift
passively or swim weakly near the surface of oceans, ponds, and lakes
Produce oxygen that is returned to the atmosphere
Range in size from microscopic to seaweeds hundreds of feet in length
Do not have true roots, stems, nor leaves
Form gametes (eggs & sperm) in single-celled gametangia (chambers)
instead of multicellular gametangia like true plants
Found in freshwater, marine, and moist soil habitats
Most have flagella at some time in life cycle
Algae cells contain organelles called pyrenoids organelles that make & store
starch
Structure of Algal Cells:
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The body of algae is called the thallus (1n)
Algae may be unicellular, colonial, filamentous, or multicellular
Unicellular algae are single-celled & make up phytoplankton (a population of
photosynthetic organisms that begins many aquatic food chains)
Phytoplankton make much world's carbohydrates & are the major producers
of oxygen
Chlamydomonas
Copyright © by Holt, Rinehart and Winston
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Colonial algae consist of groups of cells working together
Some colonial algal cells may specialize for movement, feeding, or
reproduction showing for division of labor
Volvox
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Filamentous algae have slender, rod-shaped thallus arranged in rows joined
end-to-end
Holdfasts are specialized structures in some filamentous algae that attaches
the algae so it can grow toward sunlight at the surface
Spirogyra
Copyright © by Holt, Rinehart and Winston
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Multicellular algae often have a large, complex leaf-like thallus & may have
stem-like sections and air bladders
Macrocystis is among the largest multicellular algae
Macrocystis
Copyright © by Holt, Rinehart and Winston
Reproduction in Unicellular Algae:
Asexual Phase
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Algae absorbs its flagellum
Haploid algal cell then divides mitotically from 2 to 3 times
From 4 - 8 haploid flagellated cells called zoospores develop in this parent
cell
Zoospores break out of the parent cell & eventually grow to full size
Sexual Phase
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Haploid cells dividing mitotically to produce either “plus” or “minus”
gametes
A plus gamete and a minus gamete come into contact with one another,
shed their cell walls, and fuse to form a diploid zygote
This resting stage of a zygote is called a zygospore & an withstand bad
environmental conditions
When conditions are bad, the thick wall opens and the living zoospore
emerges
Life Cycle of Chlamydomonas
Copyright © by Holt, Rinehart and Winston
Reproduction in Multicellular Algae:
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Oedogonium is a multicellular, filamentous green algae with specialized cells
called gametangia that form gametes
The male gametangia or antheridium makes sperm, & the female
gametangia or oogonium makes eggs
Sperm are released into the water & swim to the egg to fertilize them
The fertilized egg or zygote is released from the oogonium & forms thickwalled zoospores
Zoospores undergo meiosis so one cell attaches to the bottom & develops a
holdfast while the other zoospores divide & form a filament
Oedogonium Life Cycle
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Spirogyra, another filamentous green algae, reproduces by conjugation
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Two filaments align side by side, their adjacent cell walls dissolve, & a
conjugation tube forms between them
Fertilization occurs when a + gamete cell moves through the tube & fuses to
the - gamete cell
Zygote forms a thick walled spore (sporangium) that breaks away from the
parent & forms a new filament
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Conjugation Tube between Spirogyra
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The leaflike algae Ulva has a sexual reproductive cycle characterized by a
pattern called alternation of generations
Alternation of generations has two distinct multicellular phases- a haploid,
gamete-producing phase called a gametophyte and a diploid, sporeproducing phase called a sporophyte
Alternation of Generation also occurs in more complex land plants, but the
gametophyte & sporophyte do not resemble each other
Ulva Life cycle
Copyright © by Holt, Rinehart and Winston
Classification:
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Algae are classified into 7 phyla, based on color, type of chlorophyll, form of
food-storage substance, and cell wall composition
All phyla contain chlorophyll a
All algae live in water or moist areas (ponds, seas, moist soil, ice...)
Act as producers making food & oxygen
Many species of algae reproduce sexually and asexually
Sexual reproduction in algae is often triggered by environmental stress
SEVEN PHYLA OF ALGAE
Phylum
Structure
of Thallus
Pigments
Food
Cell Wall
Storage composition
Chlorophyta
(Green Algae)
Unicellular
Colonial
Filamentous
Multicellular
Chlorophyll a & b
Carotenoids
Starch
Mainly Cellulose
Multicellular
Chlorophyll a & c
Carotenoids
Fucoxanthin
Peridinin
Laminarin
Cellulose
Algin
Multicellular
Chlorophyll a
Phycobilins
Carotenoid
Starch
Cellulose
CaCO3
Unicellular
Some Colonial
Chlorophyll a & c
Carotenoids
Xanthophyll
Starch
Pectin
SiO2
Unicellular
Chlorophyll a & c
Carotenoids
Starch
Cellulose
Unicellular
Some Colonial
Chlorophyll a & c
Xanthophyll
Carotenoids
Laminarin
Cellulose
Unicellular
Chlorophyll a & b
Carotenoids
Xanthophyll
Paramylon
No Cell Wall
Pellicle
Phaeophyta
(Brown Algae)
Rhodophyta
(Red Algae)
Bacillariophyta
(Diatoms)
Dinoflagellata
(Dinoflagellates)
Chrysophyta
(Golden Algae)
Euglenophyta
(Euglenoids)
Chlorophyta (green Algae):
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May be unicellular, multicellular, or colonial
Include Spirogyra, Ulva, & Chlamydomonas
Contain chlorophyll a & chlorophyll b and carotenoids (orange & yellow
pigments) as accessory pigments
Store food as starch
Cell walls mainly cellulose, but some marine forms add CaCO3
Habitat may be freshwater, moist surfaces, or marine environments
Some have whip-like flagella for movement
May live symbiotically as lichens
Thought to have given rise to terrestrial plants
Phaeophyta (brown algae):
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7000 species
1500 species
Contain chlorophyll a & chlorophyll c and fucoxanthin (brown pigment) as
accessory pigments
Most are multicellular growing in cooler marine habitats
Include kelps & seaweeds
Largest protists
Specialized rootlike holdfasts anchor thallus to rocks
Specialized air bladders keep leaflike blades afloat near surface to get light
for photosynthesis
Stemlike structures are called the stipe and support the blades
Store food as a carbohydrate called laminarin
Include Laminaria & Fucus
Laminaria
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Macrocystis or giant kelp contains algin in its cell walls which is used in
cosmetics, some drugs, ice cream, etc.
Rhodophyta (red algae):
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Fucus
4000 species
Multicellular algae that mainly grow deep in warm marine waters
Some freshwater species exist
Highly branched thallus
Contain chlorophyll a & phycobilins (red pigments) to trap sunlight for
photosynthesis
Polysiphonia (red algae)
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Store food as starch
Cell walls contain cellulose and agar (used as a base in culture dishes to grow
microbes)
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Some species contain carageenan in their cell walls used for gelatin capsules
& in some cheeses
Bacillariophyta (diatoms):
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11,500 species
Abundant in marine & freshwater habitats
Called phytoplankton & start many aquatic food chains
Contain chlorophyll a & c, carotenoids (orange pigments), & xanthophyll
(yellow pigments)
Store food as starch & contain mainly cellulose in their cell walls
Lack cilia & flagella
Have glass like shells or valves containing SiO2 that fit together in 2 parts
Diatoms
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Centric diatoms are marine & have circular or triangular shells
Pennate diatoms are found in freshwater & have rectangular shells
When diatoms die, they form a layer called diatomaceous earth that is
abrasive and used in detergents, toothpaste, fertilizers, etc.
Dinoflagellata or Pyrrophyta (dinoflagellates):
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1100 species
Major producers in marine habitats
Small, unicellular organisms making up plankton
Many are photosynthetic, but some are colorless heterotrophs
Photosynthetic dinoflagellates are yellow to brown in color due to
chlorophyll a & c and carotenoids
Copyright © by Holt, Rinehart and Winston
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Have 2 flagella that spin and move the dinoflagellate through water
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Store food as starch
Some dinoflagellates are covered with armor like plates & spines made of
cellulose
Often undergo algal blooms where their numbers greatly increase
Produce a toxic substance and cause poisonous red tides (water appears red
due to red pigments in the dinoflagellates)
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Red Tide
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Some such as Noctiluca can produce light by bioluminescence
Photograph by Robert Brons
Chrysophyta (golden algae)
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850 Species:
Most are live in freshwater habitats, but some are marine
Unicellular algae containing chlorophyll a & c and the brown pigment
fucoxanthin and carotenoids
Many have flagella for movement
May be naked or have cellulose cell walls or silica scales or shells
May form highly resistant cysts to survive beneath frozen lake surfaces in
winter
Euglenophyta
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1000 Species:
Unicellular algae that lack cell walls
Have a flexible protein covering called the pellicle
Called euglenoids
Possess chlorophyll a & b and carotenoids
Store food as paramylon (polysaccharide)
Most live in freshwater, but some live in moist soil & the digestive tracts of
certain animals
Copyright © by Holt, Rinehart and Winston
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Euglena is a common euglenoid found in freshwater
a. Elastic, transparent pellicle below cell membrane
b. Contractile vacuole to pump out excess water
c. Chloroplasts to make food by photosynthesis
d. Can be heterotrophic in the absence of light
Fungal-Like Protists
Characteristics of Fungal Protists:
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Includes cellular slime molds, plasmodial slime molds, & water molds
Unique life cycles with two phases
Multicellular, heterotrophic organisms
Little tissue specialization
Usually small & live in moist or watery habitats
Act as decomposers breaking down dead organic matter
Slime molds:
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Shiny, wet appearance
Often brightly colored (yellow or orange)
Have unique life cycles with 2 phases --- a mobile feeding stage & a
nonmotile reproductive stage
Feeding Stage of Slime Mold
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Fungal-like in nutrition (absorptive heterotrophs that break down dead
organic matter)
May be saprophytes or parasites
Saprophytic Slime Mold
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Multinucleate body mass
May have a mobile, ameba-like feeding stage
Make a reproductive structure or fruiting body that produces spores
Often found on decaying wood or leaves
A is Lycogala epidendrum, B is Comatricha typhoides, C is Badhamia utricularia, D is
Dictydium
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Two groups of slime molds exist --- Cellular slime molds & Plasmodial slime
molds
Cellular Slime Molds (Phylum Acrasiomycota)
Plasmodial Slime Molds (Phylum Myxomycota)
Copyright © by Holt, Rinehart and Winston
Acrasiomycota (Cellular Slime Molds):
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Alternate in their life cycle between amoeboid feeding stage & sporeproducing fruiting body
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Live in freshwater, moist soil
Clump together into masses called pseudoplasmodium whenever little food
is available
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Cells in the pseudoplasmodium are independent but move together "sluglike"
Pseudoplasmodium settles & forms fruiting body with spores
Spores spread by wind to new location & form individual amoeboid feeding
stage
Myxomycota (Plasmodial Slime Molds):
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Exist as a plasmodium ( a mass of cytoplasm with many nuclei)
Plasmodium creeps along over decaying material
Decomposes & absorbs plant material as food
When food is scarce, the plasmodium forms stalked fruiting bodies with
spores that are resistant to bad environmental conditions
When conditions turn favorable, spores form a new plasmodium
Oomycota (Water Molds):
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Fungal-like organism made of branching filaments with cell walls of cellulose
Branching Filaments of Water Mold
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Aquatic water molds are parasites on fish forming furry growths on their gills
May act as decomposers in water of dead plants & animals
May be pathogenic to plants
e.g. Phytophthora infestans caused blight in potatoes (Irish Potato Famine in
19th century)
Blight in plants decays & discolors stems & leaves
Blight on Leaves & Potatoes
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Water molds reproduce sexually & asexually
Motile zoospores are asexually produced from reproductive structures called
sporangium
In sexual reproduction, cells with eggs form tubes to cells with sperm to
fertilize & form new branching filaments
Chytridiomycota (Chytrids):
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Aquatic protists that form gametes & zoospores
Most are unicellular or filamentous
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May be saprophytes (decomposers) or parasites on algae, plants, or insects
May be a link between protists & fungi