A.Schevers
Chapter 19 Protists
Section One The World of Protists
I.
II.
III.
What is a protest?
* Kingdom Protista contains the most diverse organisms of all the kingdoms.
 May be unicellular or multicellular, microscopic or very large, heterotrophic or
autotrophic.
 The characteristic that all protists share is they are all eukaryotes.
 The animal-like protists are called protoza, unlike animals, though, all protosoans are
unicellular.
 Plant-like protists are called algae, unlike plants; algae do not have organs such as
roots, stems, and leaves.
 Still other protists are like fungi because they decompose, but are able to move and do
not have chitin in their cell walls.
 Unicellular algae produce much of the oxygen in Earth’s atmosphere and are the basis
of aquatic food chains.
What is a protozoan?
 All protozoans are unicellular heterotrophs that feed on other organism or dead
organic matter.
 They usually reproduce asexually.
Diversity of Protozoans
 Many protozoans are grouped according to the way they move.
Ex. Cilia, flagella, pseudopodia
 Pseudopodia = cytoplasm-containing extensions of the plasma membrane.
 There are four main groups of protozoans: amoebas, flagellates, ciliates, sporozoans.
A.
Amoebas: Shapeless protists – (phylum Rhizopoda)
 Amoebas have no cell wall and form pseudopodia to move and feed.
 Two groupings of mostly marine amoebas
1. foraminifera – abundant on the sea floor, have hard shells made of calcium carbonate.
2. Radiolarian – are important part of marine plankton- an assortment of microscope
organisms that float in the ocean and form the base of marine food chains.
 Most amoebas reproduce asexually.
B.
Flagellates: Protozoans with flagella –(phylum Zoomastigina)
 Some flagellates are parasites that cause diseases, others are helpful to other
organisms, such as the flagellates that live in the gut of termites.
C.
Ciliates: Protozoans with cilia –(phylum Ciliophora)
 Use cilia that cover their bodies to move
 Live in every kind of aquatic habitat
 Many structures found in ciliates’ cells may work together to perform just one
important life function.
Ex. A paramecium uses its cilia, oral groove, gullet, and food vacuoles in the process
of digestion.
A paramecium usually reproduces asexually by dividing crosswise and separating into
two daughter cells.
 When environmental conditions change, they usually undergo a form of conjugation.
Sporozoans: Parasitic protozoans –(phylum Sporozoa)
 Most produce spores.
 Spores = is a reproductive cell that forms without fertilization and produces a new
organism.
 All sporozoans are parasites, have complex life cycles.
 Plasmodium, are organisms that cause the disease malaria in humans and other mammals
and in birds.
Sporozoans and malaria
 Today, more than 300 million people have malaria, which usually occurs in tropical
climates.
 The Plasmodium that mosquitoes transmit to people cause human malaria.
 Today, a combination of the drugs chloroquine and primaquine are most often used to
treat malaria.
 Some species of Plasmodium have begun to resist theses drugs.

D.
E.
Section 19-2 Algae: Plantlike Protists
I.
II.
What are algae?
 Photosynthesizing protests are called algae.
 All algae contain up to four kinds of chlorophyll what can produce a variety of colors in
algae: purple, rusty-red, olive-brown, yellow, and golden-brown, and are a way of
classifying algae.
 Algae include both unicellular and multicellular organisms.
 Photosynthesizing unicellular protests are known as phytoplankton, which produce much
of the oxygen used on Earth.
 Although multicellular algae may look like plants, they have no roots, stems, or leaves.
Diversity of Algae
 Algae are classified into six phyla
 Three of these phyla – include only unicellular species
- euglenoids
- diatoms
- dinoflagellates
 Most species in other three phyla are multicellular
- green
- red
- brown
A.
Euglenoids: Autrotrophs
 Euglenoids are unicellular, aquatic protests that have both plant and animal
characteristics.
 They lack a cell wall made of cellulose
 Most have chlorophyll and photosynthesize, but when light is not available, they can
ingest food.
 They have one or more flagella to move.
B.
Diatoms: The golden algae
Unicellular photosynthetic protists with shells composed of silica.
They make up a large component of the phytoplankton population.
The food that diatoms make is stored as oils rather than starch, which help them to
float near the surface where light is available.
 Diatoms reproduce asexually for several generations before reproducing sexually.
 Diatom shells are mined, processed and used as abrasives in tooth and metal polishes,
or added to paint to give it sparkle.
C.
Dinoflagellates: The spinning algae
 Cell walls composed of thick cellulose plates.
 Have two flagella located in grooves at right angles to each other, the cell spins slowly
as they beat.
 Major component of phytoplankton.
 Some are bioluminescent, which means they emit light.
 Some produce toxins, which cause red tides.
D.
Red Algae
 Mostly multicellular marine seaweeds
 The body of a seaweed is called a thallus, and lacks roots, stems, or leaves.
 Red algae use structures called holdfasts to attach to rocks.
 They contain photosynthetic pigments called phycobilins, which can absorb the light
that is able to penetrate water below 100 meters, allowing red algae to live in deep
water.
E.
Brown Algae
 Most live in salt water along rocky coasts in cool areas.
 Many have air bladders that keep their bodies floating near the surface, where light is
available.
 The largest and most complex of brown algae are kelp.
F.
Green Algae
 The most diverse, with more than 7000 species
 Most live in freshwater, in moist soil, on tree trunks, in snow, and even in the fur of
sloths.
 Can be unicellular, colonial, or multicellular in organization.
Ex. Chlamydomonas (unicellular), spirogyra (mutlicellular), Volvox (colony)
 Green algae can reproduce both asexually and sexually.
 A way of reproducing asexually is through fragmentation, where an individual breaks up
into pieces and each piece grows into a new individual.
 Green algae have a complex life cycle, which consists of individuals that alternate
between producing spores and producing gametes.
Alternation of Generations
 The life cycles of some of the algae and all plants have a pattern called alternation of
generations.
 An organism that has this pattern alternates between existing as a haploid and a
diploid organism.
 The haploid form of the organism is called the gametophyte because its produces
gametes.
 The gametes fuse to form a zygote from which the diploid form of the organism, which
is called the sporophyte.



III.

Certain cells in the sporophyte undergo meiosis, eventually; these cells become haploid
spores that can develop into a new gametophyte.
Section 19-3 Slime Molds, Water Molds, and Downy Mildews
I.
II.
III.
What are funguslike protists?
 These protists decompose organic materials.
 Slime molds have characteristics of both protozoans and fungi and are classified by
the way they reproduce.
A.
Slime Molds
 They live in cool, moist, shady places where they grow on damp, organic matter, such as
rotting leaves or decaying tree stumps.
 Two major types of slime molds: plasmodial slime molds and cellular slime molds.
 Slime molds are animal-like during much of their life, moving about and engulfing food
in a way similar to that of amoebas.
 Like fungi, slime molds make spores to reproduce.
B.
Plasmodial slime molds
 They get their name from the fact that they form a plasmodium, a mass of cytoplasm
that contains many diploid nuclei but no cell walls or membranes.
 This slimly mass is the feeding stage of the organism, and some move at the rate of 2.5
cm per hour.
 When food becomes scarce it transforms itself into spore-producing structures.
Meiosis takes place and produces haploid spores which will turn into gametes what will
fuse together forming a zygote. This will grow into a new plasmodium.
C.
Cellular Slime Molds
 Unlike plasmodial slime molds, cellular slime molds spend part of their life cycle as an
independent cell.
 When food is scarce, these independent cells join with hundreds of others to
reproduce.
 Cellular slime molds are haploid during their entire life cycle.
Water Molds and Downy Mildews
 Live in water or moist places.
 Some feed on dead organisms and others are plant parasites.
 Most water molds appear fuzzy, and resemble fungi, but at some point water molds
produce flagellated reproductive cells, something fungi never do.
Origin of Protists
 There is little conclusive evidence to indicate whether ancient protists were the
evolutionary ancestors of fungi, plants, and animals or whether protists emerged as
evolutionary lines that were separate.
 Some biologist agree that ancient green algae were probably ancestral to modern
plants.