Protista Phyla
Ciliates
Their name is derived from the many cilia that Ciliates use
to move and feed. Their cilia may be arranged in a wide variety of patterns,
with some species even having many cilia bonded together to form leg-like
structures for movement. Ciliates are also heterotrophic. They use cilia to
move their prey along their cell mouth, where it enters the food vacuole via
phagocytosis. Their heterotrophic metabolism and motile lifestyles frames the
Ciliate as an animal-like protist. They reproduce asexually through binary
fission but genetic diversity occurs through conjugation. An example is Stentor roeseli.
|
Dinoflagellates
Dinoflagellates are characterized by reinforced cellulose
plates which protect their cells. Flagella in the grooves between the plates
spin the Dinoflagellate as it moves through the water. They can be
photosynthetic plankton, but many are also heterotrophic and mixotrophic
(utilizing both photosynthesis and heterotrophic modes of metabolism). Due to
the presence of cellulose and chloroplasts in most dinoflagellates, they can be
thought of as plant-like. Certain species of dinoflagellates are known to
produce poison which kills large numbers of fish, invertebrates and even
humans. An example is Ceratium furca.
|
Euglena
Euglenids
have a long flagellum from one end of their cell, which is used for movement. Many
are mixotrophs, using photosynthesis in sunlight but when sunlight is unavailable,
they become heterotrophic. Euglenids can absorb organic nutrients from their
surroundings, and some engulf prey by phagocytosis. They have a light detector
organelle near the base of their flagellum, helping them move toward an appropriate
light intensity. This appropriate light intensity is filtered through by the
eyespot organelle. Euglenids are plant-like protists. Even though they are
motile and heterotrophic like animals, they rely heavily on photosynthesis and
have many organelles devoted solely to finding and utilizing light. An example is Euglena viridis.
|
Chlorophyta (Green Algae)
Closely
related to land plants, Green Algae have chloroplasts very similar to those of
plants. They are divided into two groups, charophytes and chlorophytes. Charophytes
have rings of cellulose-synthesizing proteins, peroxisome enzymes, flagellated
sperm and the formation of microtubules called phragmoplast which are all
evidence of their link with plants. Chlorophytes can form colonies, have true
multicellular bodies or repeatedly divide their nuclei without dividing the
cytoplasm. Their links to modern plants, alternation of generations and usage
of photosynthesis strongly suggests that Green Algae are plant-like protists. An example is green seaweed (Enteromorpha).
|
Phaeophyta (Brown Algae)
Multicellular,
large and complex, Brown Algae are found in marine environments along temperate
coasts. Their brown colors comes from the carotenoids in their plastids. Specialized
tissues and organs developed analogous with plants in the Brown Algae. They
also share several plant-like features like a root-like holdfast, stem-like
stipe and leaf-like blades, but they all developed analogously. Their life cycle
includes the alternation of generations, with haploid zoospores developing into
multicellular male and female gametophytes. The sporophyte arises from the
following zygote. Brown algae, with their similarities to plants, can be framed
as plant-like. An example is giant kelp.
|
Rhodophyta (Red Algae)
Red
Algae derived their reddish color from a photosynthetic accessory pigment
called phycoerythrin. Some Red Algae may lack pigment entirely and lives parasitically
on other Algae. They are abundant in the warm coastal waters of tropical
oceans. They absorb blue and green light, which penetrate deep in the ocean
depths. They are multicellular and their life cycles include the alternation of
generations. But their sperm are not flagellated, and they Red Algae rely on
ocean currents to bring the gametes together. Red Algae are plant-like protists
because their life cycles have the alternation of generation and they perform
photosynthesis. An example is Fauchea laciniata.
|
Cellular Slime Molds
Cellular
Slime Molds consist of individual feeding cells when food is available. When
the food source is depleted, the cells come together and function as a unit. While
their plasma membranes still separate them, the Cellular Slime Molds work as
one. They are all haploid organisms as well. Cellular Slime Molds can be
considered fungi-like protists because they form fruiting bodies to release
spores for reproduction, although it is asexual. An example is Fuligo septica.
|
Click on the following link to learn about the domain Bacteria: