KINGDOMS OF LIFE
Protista
Table of Contents
National Science Standards Correlations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .I
Chapter One: What is a Protist?
Protista: The Variable Kingdom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
What is a Eukaryote? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Eukaryotic Cellular Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Three Lifestyles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Functions of Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Questions on What is a Protist? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Lab Activity: Identifying Protists in Pond Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Chapter Two: The Protista Family Tree
Plant-like Protists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Diatoms, Euglenoids, and Dinoflagellates, Green, Red, and Brown Algae
Animal-like Protists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Parasitic Protozoa, Pseudopodia, Flagellates, Ciliates
Fungus-like Protists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Slime Molds, Water Molds
A Crossword on The Protista Family Tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Lab Activity: The Needs of Algae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Chapter Three: Protist Internal Processes, Homeostasis, and Natural Cycles
Functions of the Living Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Functions of Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Respiration, Metabolism, and the Krebs Cycle, Homeostasis and Transport
Nutrition, Internal Transport and Synthesis, Growth and Movement
Questions on Protist Internal Processes, Homeostasis, and Natural Cycles . . . . . . . . . . . . . . . . . . . . . .26
Lab Activity: Observing the Growth of Water Mold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Chapter Four: Protist External Processes and Relationships in Nature
Trophic Levels, Food Chains, and Energy Transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
The Carbon Cycle and the Nitrogen Cycle, and their Ecological Effects . . . . . . . . . . . . . . . . . . . . . . .29
Symbiotic Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Evolution, Adaptation, and the Protists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Questions on Protist External Processes and Relationships in Nature . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Lab Activity: Food Chains Among Protists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Chapter Five: Protist Reproduction
What is Ploidy? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Mitosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Meiosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
Alternation of Generations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Why Is There a Need for More than One Reproductive Strategy? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Questions on the Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
Lab Activity: Reproduction Rate of Protozoa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Answer Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Safety and Ethical Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
Biology Timeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48
Transparencies
Eukaryotic Cell, Three Lifestyles of Protista, Single-Celled Algae, Large Algae,
The Protozoa, Amoeba Feeding, Krebs Cycle, Diversity Chart, Carbon Cycle,
Mitosis, Meiosis, Alternation of Generations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-12
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MP4851 Kingdoms of Life: Protista
What is a Protist?
Protista—The Variable Kingdom
T
he Kingdom Protista is a kingdom of
exclusion. Organisms that are not clearly
bacteria, fungi, plants, or animals, are grouped
into this large and diverse kingdom.
The organisms in Kingdom Protista have
things in common with other kingdoms of life.
Some members of this kingdom are singlecelled, like the organisms in the two bacterial
kingdoms. Some eat, move, and behave very
much like animals. Some are autotrophic, and
are producers in marine and aquatic ecosystems
worldwide. Some are saprobes, and break
down dead matter, like fungi.
If they have so much in common with the
other kingdoms of life, why aren’t protists
members of those other kingdoms? Why have
they been grouped into their own varied
kingdom? In this book, we will explore the
differences between protists and the other
kingdoms of life, as well as the similarities
between protists and other kingdoms.
Protists, unlike bacteria, are eukaryotes.
All life higher than bacterial life consists of
organisms composed of one or more eukaryotic
cells. The word eukaryote means “true cell,”
and each eukaryotic organism, whether singlecelled or multicellular, has cells with a nucleus
that contain the organism’s DNA, and undergo
mitosis. Even the simplest single-celled protist,
such as an amoeba or a diatom, is far more
complex than the most complicated bacterium.
All protists require a moist environment,
and most are entirely aquatic or marine. Some
can live in moist soil. Protists are not found in
dry regions, such as deserts or tundra. With
few exceptions, most do not survive in very
cold or very hot temperatures. A few species of
algae can live below polar ice in near-freezing
liquid water, and a few more at very high
temperatures, but they are the exceptions. Even
though they are exceptions, these algae still
cannot survive freezing or boiling. Having no
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mechanism for thermoregulation, most protists
thrive at temperatures that permit them to
perform homeostatic functions—well above the
freezing temperature of water, and well below
the boiling point of water. Outside of this
narrow temperature range, they engage in selfprotective activities, and slow down their
metabolism to a great extent, or, in many cases,
simply die out. Boiling water, for instance,
will kill all protists, as any back country hiker
can tell you.
Protists are responsible for a number of
waterborne diseases in humans, as well as in
wildlife and livestock. An example of a disease
that affects humans and other animals is
giardiasis, which is caused by an amoeba
(Giardia intestinalis) that lives in the intestinal
tracts of humans or animals. Once in the
intestines, they attach to the intestinal wall,
where they compete for important nutrients.
The loss of these nutrients causes cramps, gas,
and diarrhea on a cyclical basis. The parasites
are then excreted in the fecal matter of the
victim, and are introduced to water supplies by
runoff into streams.
In developed nations, giardiasis is not much
of a problem. The amoeba that causes the
disease is killed easily by modern water
purification techniques, and, as mentioned, by
boiling. Occasional outbreaks are reported by
day-care centers that work with very young
children, and are usually tied to insufficient
hygiene after diaper changes. Outbreaks occur
in nursing homes for largely the same reasons.
Most cases can be cured with medication, and
the disease is easily prevented.
However, in the developing world,
giardiasis is a major killer, especially of small
children. Water supplies in the developing
world are often contaminated, and public
health programs to purify water do not exist.
Any form of diarrhea can cause serious
dehydration, and the nature of the illness causes
the child not to be able to process fats from his
MP4851 Kingdoms of Life: Protista 1
(Fig.1A)
Chloroplast and
Mitochondrion
or her diet. Many children die of malnutrition
because of giardiasis.
There are also human diseases caused by
protists that are carried to the final host by
arthropod vectors. Ticks, mosquitoes, and
biting flies pass along protist-caused diseases
such as malaria, yellow fever, sleeping
sickness, and a host of others. Most of these
diseases are caused by protozoa called
sporozoa, which form spores as part of their
reproductive cycles.
Some protists are autotrophic. It is now
known that autotrophic protists are the ancient
ancestors of modern plants. Others are
saprobes. It is currently believed that these
organisms are the ancestors of modern fungi.
Finally, some protists have distinct animal-like
characteristics, and it is known that these
organisms, in colony forms, are the ancestors of
modern animals.
(Fig.1A)
of one or more cells that contain a nucleus,
and usually, other organelles. These organelles
are separated from the cytoplasm of the cell
by membranes.
In a eukaryotic cell, the organism’s DNA is
contained wholly within the nucleus. A
secondary DNA, which in sexual organisms is
passed along through the mother’s line, is
contained within the mitochondria.
Mitochondrial DNA, or mDNA, is passed
whole down to the cells during mitosis, and
unlike nuclear DNA, also during meiosis.
How can this happen? In the early 1960s a
number of experiments showed that
mitochondria could not be produced by the
cells themselves, the way that the other parts of
the cell, including the nucleus, can be produced.
They arose only from the division of alreadyexistent mitochondria—they are selfreplicating. By the end of the decade, it was
known that mitochondria had their own DNA.
Today, it is believed that mitochondria are
quasi-independent organisms that are the
descendants of obligate symbionts among the
ancient monera. The result is a mutual
symbiotic relationship between prokaryotes and
eukaryotes, without which eukaryotic life
would cease to exist.
Eukaryotic Cellular Organization
Chloroplast
Mitochondrion
What is a Eukaryote?
Bacteria of both types, eubacteria and
archaebacteria, are prokaryotes, or “first cells.”
All other living things on Earth are eukaryotes,
or “true cells.” Eukaryotic life forms consist
2 MP4851 Kingdoms of Life: Protista
Protophyta cells, such as those belonging to
algae, dinoflagellates, and diatoms, look very
much like other protist cells, such as those
belonging to protozoa and protofungi. There
are a few differences, however. In addition to
the following organelles and structures,
protophyta cells also contain chloroplasts, where
chlorophyll is stored. They also have a cell wall
on the outside of the cellular membrane, which
gives the algae its shape. Some of these cell
walls have been further defined into hard shells,
such as diatoms possess. One group of
protozoa, an amoeba family called the
foraminiferans, also make a hard shell around
their bodies. This is not an extension of a cell
wall, however, but a true shell, such as a
mollusc produces from calcium carbonate in the
water. Another group, the radiolarians, make
outer protective coatings from silica.
Here, then, are the basic parts of the
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(Fig.1B)
typical eukaryotic cell:
(Fig.1C)
Nucleus. The nucleus contains the DNA of
the organism in long, tangled strings called
chromatin. These chromatin separate during
mitosis or meiosis. Also within the nucleus is
the nucleolus, where ribosomes are produced.
Ribosomes are involved in protein synthesis,
and eventually move throughout the cell. They
produce enzymes and carry out the DNA
message for the cell.
Nuclear envelope. The nucleus is
surrounded by a membrane called the nuclear
envelope. It is porous, and allows for the
transport of sugars called nucleotides to pass
into the nucleus, and ribosomes to pass out of
the nucleus.
Cytoplasm. Cytoplasm is the gel-like
substance within the cell in which all the
organelles are suspended.
Endoplasmic Reticulum. This is a folded
membrane that takes up a good percentage of
the cell. There are two types. Rough E.R. is
covered with ribosomes, and smooth E.R. does
not have ribosomes sited on it. The function of
the E.R. is to synthesize fats and produce
enzymes for protein synthesis.
(Fig.1B)
Foraminifera
(Fig.1C)
Radiolarian
(Fig.1D)
Protista Cell
Structure
(Fig.1D)
Cilia
Mitochondrion
(In animals and some protists)
Golgi Apparatus
Smooth Endoplasmic Reticulum
Lysosome
(In animal cells only)
Vacuole
Cytoskeleton
Vacuole
Cytoplasm
Free Ribosomes
Rough Endoplasmic Reticulum
Chloroplast
Microvilli
(In plants)
(In animals)
Cell Wall
Nucleolus
Nucleus
(In plants and some protists)
Nuclear Membrane
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MP4851 Kingdoms of Life: Protista 3