Name ________________
Notes Page ______
Protists
Objectives
• List the animal-like, fungus-like, and plantlike protists and describe their
characteristics.
• Identify the parts protists.
• Recognize that most protists are single-celled.
• Recognize that all protists are eukaryotic.
• Summarize how protists get energy in three different ways.
The BIG Idea
• Bacteria and protists have the characteristics of living things.
Key Concept
• Protists are a diverse group of organisms.
Most protists are single celled.
•
When Aton van Leeuwenhoek began using one the world’s first
microscopes, he looked at pond water, among other things. Recall that
he described what he saw as animalcules. Some of the organisms he
saw probably were small, multicellular organisms. However, many of
the organisms he saw only had one cell. Today, scientists call these
single-celled organisms protists.
•
Protists include all organisms with cells having nuclei and not
belonging to the animal, plant, or fungi kingdoms. In other words,
protists may be considered a collection of leftover organisms. As a
result, protists are the most diverse of all the kingdoms.
•
Most protists are single-celled, microscopic organisms that live in
water or a moist environment. However, protists also include some
organisms with many cells. These many-celled organisms have simpler
structures than animals, plants, or fungi. They also have fewer types
of cells in their bodies.
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There are three groups of protists.
•
When we examine protists, we see that they share many characteristics.
Scientists are able to group the protists based on how they obtain their
energy. They name each group of protists based on the kingdom they
most resemble.
•
The three groups of protists include animal-like, plant-like, and funguslike.
What are protists? Single or multi-celled organisms that
have nuclei but do not fit in the other kingdoms.
Where do most protists live? In water or moist environments.
Why is the protists kingdom considered the most diverse? It
includes all organisms that do not fit into any of the
other categories. It is the “leftover” kingdom.
There are four types of animal-like protists.
•
Protists that eat other organisms, or decaying parts of other organisms,
are animal-like protists, called protozoa.
•
They include many forms, but they are all unicellular. Protozoa cannot
use sunlight as a source of energy. Therefore they are heterotrophs.
Also, protozoa must move to obtain their energy.
•
Certain chemicals in protozoa can recognize when a particle of food is
nearby. The food particle is usually another organism or part of one.
The protozoan ingests the good and breaks it down to obtain energy.
•
There are four types of animal-like protists. They are classified by how
they live and move.
•
The first is protozoa with pseudopods.
o This group of protozoa use pseudopods to move. Pseudopods are
temporary bulges of the cell membrane that fill with cytoplasm.
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o When the cell fills the pseudopod with cytoplasm, the rest of the
cell follows, causing it to move in that direction.
o Pseudopods are use primarily for two reasons: to move and to
capture food.
o This group of protozoa are called sarcodines. An example of
this group is the amoeba.
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The second is protozoa with cilia.
o These protozoa are called ciliates because they have a structure
called cilia.
o Cilia are hair-like projections from the cell that move in a
wavelike pattern. Ciliates use cilia to move, obtain food, and to
sense the environment.
o Ciliates have very complex cells. This is because they have two
nuclei. The large nucleus controls the everyday tasks of the cell.
The small nucleus functions in reproduction. Ciliates can
reproduce through binary fission but also use conjugation.
o A common example of ciliates include paramecium, one of the
most well-known protists.
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The third group is protozoa with flagella.
o This group of protozoa is called zooflagellate. These organisms
use their flagella to move. Zooflagellates can have one to eight
long, whip-like flagella to help them move.
o Many zooflagellates live in organisms. More often than not,
these organisms benefit each other. This is an example of
symbiosis.
o However, not all symbiotic relationships are good. For example,
malaria is a disease that is caused by protists.
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The fourth group of protozoa is diverse.
o This group of protozoa moves in a variety of ways. However,
they are grouped on how they live.
o For example one group is the sporozoans, which feed on their
host’s cells and body fluids.
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What is the name given to all animal-like protists? Protozoa
Identify the name of the group of protozoa that have the following
characteristic.
Has flagella: zooflagellates
Has cilia: ciliates
Feeds on cells: sporozoans
Has pseudopods: sarcodines
Why are sporozoans not classified by how they move? They
move in a variety of ways. Therefore, they are classified
by how they live.
There are six types of plant-like protists.
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Plantlike protists, called algae, obtain their energy from sunlight. Like
plants, algae use the Sun’s energy, water, and carbon dioxide from the
air or water to produce food. Algae contain chlorophyll (and
chloroplasts). Because they produce their own food, all algae are
autotrophs.
•
Algae include organisms that are unicellular, unicellular but live in
colonies, and multicellular. If the cells form a colony, certain cells
can carry out specific functions: reproduction, capturing food, etc.
•
Algae also come in a variety of colors, even if their cells contain
chloroplasts and chlorophyll. This is a result of the cells having
pigments.
•
Euglenoids
o Euglenoids are green, unicellular algae that found mostly in
fresh water.
o Although they are classified as plant-like protists, they have an
unusual characteristic. Given the right circumstances, these algae
can be heterotrophs. This will occur when there is not enough
sunlight.
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o Euglena, a common euglenoid, is able to detect light through the
use of its eyespot. Should you place them in a container and
expose half in sunlight, all of the euglena will move to the sunlit
side.
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Dinoflagellates
o Dinoflagellates are like the knights of the protist kingdom. Stiff
plates of silica, that look like armor, cover their body.
o You will most commonly find these in saltwater environments.
o All dinoflagellates are unicellular. To move, they have two
flagella that cause them to twirl.
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Diatoms
o Diatoms are unicellular and have glasslike cell walls. Some
simply float on the surface of the water. If any organism
(including plants, animals, and protists) drifts in water they are
called plankton. If they are able to carry out photosynthesis,
they are called phytoplankton.
o Sometimes diatoms will attach themselves to a surface.
o Diatoms have a unique way to move: they shoot chemicals from
their cell wall. It’s similar to jet propulsion.
o When they die, their cell walls collect at the bottom of sea floors.
As a result, they form a material called diatomaceous earth.
This substance is often found in toothpaste. It does a great job
at polishing your teeth.
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Green, Red, and Brown Algae
o This group of protists is what you think of when you hear the word
seaweed. There are many different organisms that are classified
under green, red, and brown algae.
o The major difference between these types of algae is there color
and where they live.
o Green algae can be found in both fresh and saltwater. Some can
be found on land but it must be in moist environments. It can also
be unicellular or multicellular.
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o Red algae are mostly multicellular seaweeds. Their red color
helps them absorb light deep in the ocean. This means they can
grow deeper in the ocean where there is less competition from
other organisms.
o Brown algae are what most people refer to when they encounter
seaweed. Even though they are brown, they have a variety of
pigments. These also make the giant kelp forests in the Pacific
costal waters.
Of the plant-like protists, which can be a heterotroph? Euglenoid
Which group is unicellular? Dinoflagellates
What causes plant-like protists to have such a variety of colors,
even though they have chloroplasts? Pigments
How do protozoa and algae differ in the way they get their
energy? Protozoa eat other organisms and get energy
from the nutrients in the organisms they eat. Algae get
energy from sunlight.
There are three types of fungus-like protists.
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Protists that absorb food from their environment can be called fungus-like
protists. These protists take in materials from the soil or from other
organisms and break materials down in order to obtain energy. They
are called decomposers.
•
The term “mold” refers to many organisms that produce a fuzzy-looking
growth. Most of the molds you might be familiar with, like bread mold,
are fungi (not protists). But three groups of protists are also called
molds.
•
These molds have structures that are too simple to be called fungi, and
they are unicellular for a portion of their lives.
•
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Water molds
o One example of a fungus-like protist is water mold, which forms a
fuzzy growth on food. This food may be decaying animal or
plant tissue or a living organism. Water molds live mainly in
fresh water.
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Slime molds
o Slime molds live on decaying plants on the forest floor. One kind
of slime mold consists of microscopic single cells that ooze
around, eating bacteria.
o When their food is scarce, however, many of the cells group
together to produce a multicellular colony. The colony eventually
produces a reproductive structure to release spores.
o Wind can carry sports about, and they sprout where they land.
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Plasmodial slime molds
o You might see this type of mold while
walking through a forest. The organism
looks like a fine net, like lace, several
centimeters across, on rotting logs.
o These slime molds are not multicellular,
but instead one giant cell with many
nuclei. They form when many different cells fuse together to form
one large cell.
Compare and contrast slime molds and plasmodial slime molds.
Both slime molds and PSMs are unicellular. PSMs have
many nuclei in one cell. They form when many different
cells fuse together. Slime molds can form colonies to
reproduce.
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