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Alveolates: dinoflagellates, apicomplexians, and ciliates

A large body of data supports that the alveolates are derived from a shared common ancestor. The alveolates are named for the presence of an alveolus, or membrane-enclosed sac, beneath the cell membrane. The exact function of the alveolus is unknown, but it may be involved in osmoregulation. The alveolates are further categorized into some of the better-known protists: the dinoflagellates, the apicomplexans, and the ciliates.

Dinoflagellates exhibit extensive morphological diversity and can be photosynthetic, heterotrophic, or mixotrophic. Many dinoflagellates are encased in interlocking plates of cellulose. Two perpendicular flagella fit into the grooves between the cellulose plates, with one flagellum extending longitudinally and a second encircling the dinoflagellate ( [link] ). Together, the flagella contribute to the characteristic spinning motion of dinoflagellates. These protists exist in freshwater and marine habitats, and are a component of plankton    , the typically microscopic organisms that drift through the water and serve as a crucial food source for larger aquatic organisms.

The illustration shows two dinoflagellates. The first is walnut-shaped, with a groove around the middle and another perpendicular groove that starts at the middle and extends back. Flagella fit in each groove. The second dinoflagellate is horseshoe-shaped, with the body extending from the wide part of the horseshoe toward the narrow end. Like the first dinoflagellate, this one has two perpendicular grooves, each containing a flagellum.
The dinoflagellates exhibit great diversity in shape. Many are encased in cellulose armor and have two flagella that fit in grooves between the plates. Movement of these two perpendicular flagella causes a spinning motion.

Some dinoflagellates generate light, called bioluminescence    , when they are jarred or stressed. Large numbers of marine dinoflagellates (billions or trillions of cells per wave) can emit light and cause an entire breaking wave to twinkle or take on a brilliant blue color ( [link] ). For approximately 20 species of marine dinoflagellates, population explosions (also called blooms) during the summer months can tint the ocean with a muddy red color. This phenomenon is called a red tide, and it results from the abundant red pigments present in dinoflagellate plastids. In large quantities, these dinoflagellate species secrete an asphyxiating toxin that can kill fish, birds, and marine mammals. Red tides can be massively detrimental to commercial fisheries, and humans who consume these protists may become poisoned.

The breaking wave in this photo is an iridescent blue color.
Bioluminescence is emitted from dinoflagellates in a breaking wave, as seen from the New Jersey coast. (credit: “catalano82”/Flickr)

The apicomplexan protists are so named because their microtubules, fibrin, and vacuoles are asymmetrically distributed at one end of the cell in a structure called an apical complex ( [link] ). The apical complex is specialized for entry and infection of host cells. Indeed, all apicomplexans are parasitic. This group includes the genus Plasmodium , which causes malaria in humans. Apicomplexan life cycles are complex, involving multiple hosts and stages of sexual and asexual reproduction.

Illustration A shows an oval cell that has a narrow end and a wide end. The apical complex is located at the narrow end. The three branches of this complex narrow and join at the apical, or narrow, end of the cell. Illustration b shows the life cycle of Plasmodium, which causes malaria. The plasmodium life cycle begins when a mosquito takes a blood meal and injects Plasmodium into the bloodstream. The Plasmodium enters the liver where it multiplies, and eventually reenters the blood. In the blood it enters the ring stage, so called because the cell is curled into a ring shape. The Ring stage may multiply by mitosis or it may undergo meiosis, forming new 1n gametes of male or female sex types. When a mosquito takes a blood meal from an infected host the gametes are ingested. A smaller gamete sex type, called a microgamete, fertilizes a larger sex type, called a macrogamete, producting a 2n zygote. The zygote undergoes mitosis and differentiation. It enters the saliva where it can be injected into another host, completing the cycle.
(a) Apicomplexans are parasitic protists. They have a characteristic apical complex that enables them to infect host cells. (b) Plasmodium , the causative agent of malaria, has a complex life cycle typical of apicomplexans. (credit b: modification of work by CDC)

Questions & Answers

what is cell?
V.S.Nikhil Reply
The smallest structure and functional unit
vinod
Hydra reproduce through which process
Saint Reply
which is smallest organ in our body
Techi
pineal gland
Himangshu
Yh in the ears...
Mozua
why you hand plam is sweating in everytime
Techi
who is the father of mycology
Sagar Reply
Heinrich Anton de Bary
Delissa
describe the similarities and differences between cytokinesis mechanism found in animal cells versus in plant cells
hiro Reply
what is life?
Techi
life is the existantce of indvidual human or animal.
R0se
thanks
Techi
are humans beings considered to have the eukaryotic cells
success Reply
yes.....
Delissa
eukaryotes are organisms that possess cells with a nucleus enclosed in a membrane, humans, and all complex organisms are eukaryotes.
Delissa
so humans and animals also have cell membranes.... cause I did this test prep and they said plants...I just want to be sure
success
and thank you for your reply it was helpful👍✌
success
eu= "perfect", "good", karyon= nut, amound, nucleus
Tiago
you're welcome. Plants are also eukaryotes.
Delissa
plants, like animals, possess a nucleus bound by a membrane.
Delissa
similarities and differences between cytokinesis mechanism found in animal cell vs cell division
Raymark Reply
what is the name of a male flower?
Ikeomu Reply
staminate means flower containing only stamen
Falak
what is the definition of evolution in a population?
Homero Reply
the slow changing of a species to adapt to any changes in the environment or how it feeds/hunts. im not good at explaining things lol.
Eclipse
the organ which is sensitive to light in euglena
Fatimah Reply
the organ which is sensitive to light in euglena is
Fatimah
all chlorophyll containing motile cells are sensitive to light
Himangshu
there is no more other chapter
Sandeep Reply
Give tow examples for nutritional deficiency Diseases-
Singampalli Reply
How does a plant cell look like
Sang Reply
in a sleepers form
David
what do you mean ? I could not understand
Gul
they have a regular shape and a large vacoule
Fatimah
I thought it looked like rectangle
Abrahán
a stage in mitosis wherein in spindle fibers begin to shorten to pu the sister chromatids away from each other towards the opposite ends of the cell
Earl Reply
a stage in interphase where chromosome s are duplicated
Earl
What is biodiversity
Sp Reply
Hmm
Hele
Name two secretions of Golgi apparatus
Daniel Reply

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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