Trypanosoma most resembles which of the unicellular algae

When there is sufficient sunlight for it to feed by phototrophy, it uses chloroplasts containing the pigments chlorophyll a and chlorophyll b to produce sugars by photosynthesis. Thus, the intriguing similarities between Euglena and the plants would have arisen not because of kinship but because of a secondary endosymbiosis. Molecular phylogenetic analysis has lent support to this hypothesis, and it is now generally accepted.

Peranema Figure They are found in freshwater lakes, ponds and ditches, and are often abundant at the bottom of stagnant pools rich in decaying organic material. Although they belong to the class Euglenoidea, and are morphologically similar to the green Euglena, Peranema have no chloroplasts, and cannot feed by autotrophy. Chlamydomonas Figure Chlamydomonas is used as a model organism for molecular biology, especially studies of flagellar motility and chloroplast dynamics, biogeneses, and genetics.

One of the many striking features of Chlamydomonas is that it contains ion channels, channelrhodopsins , that are directly activated by light. These proteins are used in optogenetics. Gymnodinium is a genus of dinoflagellates It is one of the few naked dinoflagellates, or species lacking armor cellulosic plates.

Most are marine plankton, but they are common in freshwater habitats, as well. Their populations are distributed depending on temperature, salinity, or depth. Many dinoflagellates are known to be photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey phagotrophy. In terms of number of species, dinoflagellates form one of the largest groups of marine eukaryotes, although this group is substantially smaller than the diatoms.

Some species are endosymbionts of marine animals and play an important part in the biology of coral reefs. Other dinoflagellates are unpigmented predators on other protozoa, and a few forms are parasitic.

Pandorina Figure The cells are ovoid or slightly narrowed at one end to appear keystone- or pear-shaped. Each cell has two flagella with two contractile vacuoles at their base, an eyespot, and a large cup-shaped chloroplast with at least one pyrenoid. The colonies co-ordinate their flagellar movement to create a rolling, swimming motion.

Pandorina shows the beginnings of the colony polarity and differentiation seen in Volvox since the anterior cells have larger eyespots. Asexual reproduction is by simultaneous division of all cells of the colony to form autocolonies that are liberated by a gelatinization of the colonial envelope. Sexual reproduction occurs by division of each cell of the colony into zoogametes. Zoogametes show indications of heterogamy, a slight difference in the size and motility of the pairs that fuse to form the smooth walled zygote.

Volvox Figure It forms spherical colonies of up to 50, cells that were first reported by Antonie van Leeuwenhoek in Volvox diverged from unicellular ancestors approximately million years ago. Each mature Volvox colony is composed of up to thousands of cells from two differentiated cell types: numerous flagellate somatic cells and a smaller number of germ cells lacking in soma that are embedded in the surface of a hollow sphere or coenobium containing an extracellular matrix made of glycoproteins.

Adult somatic cells comprise a single layer with the flagella facing outward. The cells swim in a coordinated fashion, with distinct anterior and posterior poles. The cells have anterior eyespots that enable the colony to swim towards light. An asexual colony includes both somatic vegetative cells, which do not reproduce, and large, non-motile gonidia in the interior, which produce new colonies through repeated division.

In sexual reproduction two types of gametes are produced. Volvox species can be monoecious or dioecious. Male colonies release numerous sperm packets, while in female colonies single cells enlarge to become oogametes, or eggs. Volvox is facultatively sexual and can reproduce both sexually and asexually.

The switch from asexual to sexual reproduction can be triggered by environmental conditions and by the production of a sex-inducing pheremone. Desiccation-resistant diploid zygotes are produced following successful fertilization.

Oedogonium Figure Oedogonium can be free-floating, though it is usually attached to aquatic plants by a holdfast. It appears greenish and inhabits calm, fresh water. Oedogonium can reproduce asexually by fragmentation of the filaments, through some other types of non-motile spores, and also through zoospores, which have many flagella. These develop in a zoosporangium cell, one zoospore per zoosporangium. After settling and losing its flagella, a zoospore grows into a filament.

Oedogonium can also reproduce sexually. Its sexual life cycle is haplontic, i. Antheridia produce and release sperm, and oogonia produce and release an egg,. The egg and sperm then fuse and form a zygote which is diploid 2n. The zygote then undergoes meiosis to produce the filamentous green alga which is haploid 1n. Spirogyra Figure It is commonly found in freshwater areas, and there are more than species of Spirogyra in the world.

Spirogyra can reproduce both sexually and asexually. The body thallus contains holdfasts for attachment, blades , and a stem-like structure that holds the blades is called a stipe. Many species have floats that function in floatation. Some have gas-filled floats. Mucilaginous slimy material in the cell walls retards drying in exposed individuals when the tide goes out. Most species have a life cycle with alternation of generations. Some species of Fucus have diploid adults. Sargassam sometimes breaks off to form floating masses.

Other marine organisms congregate around these masses. Laminaria is a brown alga that is usually found attached just below the intertidal zone.

It has a life cycle with alternation of generations. Protective cellulose plates cover dinoflagellates and two flagella enable them to move. One of the flagella lies in a transverse groove that causes cell to spin as it moves.

Most are found in marine or freshwater environments and many are photosynthetic. They are important components of phytoplankton and thus are important in aquatic food chains.

This group also includes many heterotrophic and many mixotrophic species. Some species are responsible for red tides that kill fish and shellfish Gymnodinium, Gonyaulax, Pfiesteria. Some live as symbiants within some invertebrates. For example, some corals grow faster with dinoflagellates living within their cells.

Some species are capable of bioluminescence they produce light. Both sexual and asexual reproduction occur. Sexual reproduction produces cysts which are resistant to unfavorable environmental conditions. Cysts are dormant and become active when environmental conditions improve. The pellicle outer covering of paramecium is covered with hundreds of cilia.

They have numerous organelles including a gullet oral groove and an anal pore. Ciliates have a large macronucleus and a smaller micronucleus. The micronucleus is involved in sexual and asexual reproduction. Other nuclear activities are handled by the macronucleus. The macronucleus is polyploid approximately N in Paramecium aurelia and the micronucleus is diploid.

During reproduction, the macronucleus disintegrates. Later, a micronucleus will develop into a macronucleus. Most reproduction is asexual mitosis. Sexual reproduction is by conjugation. The micronucleus will divide by meiosis; 3 of the 4 resulting nuclei will disintegrate as will the macronucleus. The remaining haploid nucleus will divide by mitosis producing an individual with two haploid nuclei.

Two conjugating individuals will each exchange one of the nuclei. The two haploid nuclei will then fuse producing a diploid nucleus. Red algae are mostly multicellular and are found mainly in warmer, tropical oceans. Their red color is due to an accessory photosynthetic pigment called phycoerythrin.

The accessory pigments of red algae are able to absorb blue and green light. This allows some species to survive in deep waters where blue and green light predominates.

The protist then transports its cytoplasm into the pseudopod, thereby moving the entire cell. This type of motion, called cytoplasmic streaming, is used by several diverse groups of protists as a means of locomotion or as a method to distribute nutrients and oxygen.

Ammonia tepida : Ammonia tepida, a Rhizaria species viewed here using phase contrast light microscopy, exhibits many threadlike pseudopodia. Foraminiferans, or forams, are unicellular heterotrophic protists, ranging from approximately 20 micrometers to several centimeters in length; they occasionally resemble tiny snails. As a group, the forams exhibit porous shells, called tests, that are built from various organic materials and typically hardened with calcium carbonate.

The tests may house photosynthetic algae, which the forams can harvest for nutrition. Foram pseudopodia extend through the pores and allow the forams to move, feed, and gather additional building materials. Foraminiferans are also useful as indicators of pollution and changes in global weather patterns. The life-cycle involves an alternation between haploid and diploid phases. The haploid phase initially has a single nucleus, and divides to produce gametes with two flagella.

The diploid phase is multinucleate, and after meiosis fragments to produce new organisms. The benthic forms has multiple rounds of asexual reproduction between sexual generations. Forams : These shells from foraminifera sank to the sea floor. A second subtype of Rhizaria, the radiolarians, exhibit intricate exteriors of glassy silica with radial or bilateral symmetry. Radiolarians display needle-like pseudopods that are supported by microtubules which radiate outward from the cell bodies of these protists and function to catch food particles.

The shells of dead radiolarians sink to the ocean floor, where they may accumulate in meter-thick depths. Preserved, sedimented radiolarians are very common in the fossil record. Radiolarian shell : This fossilized radiolarian shell was imaged using a scanning electron microscope. Archaeplastida are a supergroup of protists that comprise red and green algae, which include unicellular, multicellular, and colonial forms. Red algae and green algae are included in the supergroup Archaeplastida.

It is well documented that land plants evolved from a common ancestor of these protists; their closest relatives are found within this group. Molecular evidence supports that all Archaeplastida are descendants of an endosymbiotic relationship between a heterotrophic protist and a cyanobacterium. The red and green algae include unicellular, multicellular, and colonial forms. Red algae, or rhodophytes, are primarily multicellular, lack flagella, and range in size from microscopic, unicellular protists to large, multicellular forms grouped into the informal seaweed category.

The red algae life cycle is an alternation of generations. Some species of red algae contain phycoerythrins, photosynthetic accessory pigments that are red in color and outcompete the green tint of chlorophyll, making these species appear as varying shades of red.

Other protists classified as red algae lack phycoerythrins and are parasites. Red algae are common in tropical waters where they have been detected at depths of meters. Other red algae exist in terrestrial or freshwater environments. The most abundant group of algae is the green algae.

The green algae exhibit similar features to the land plants, particularly in terms of chloroplast structure. It is well supported that this group of protists share a relatively-recent common ancestors with land plants. The green algae are subdivided into the chlorophytes and the charophytes. The charophytes are the closest-living relatives of land plants, resembling them in morphology and reproductive strategies.

Charophytes are common in wet habitats where their presence often signals a healthy ecosystem. The chlorophytes exhibit great diversity of form and function. Chlorophytes primarily inhabit freshwater and damp soil; they are a common component of plankton.

Chlamydomonas is a simple, unicellular chlorophyte with a pear-shaped morphology and two opposing, anterior flagella that guide this protist toward light sensed by its eyespot. More complex chlorophyte species exhibit haploid gametes and spores that resemble Chlamydomonas.

The chlorophyte Volvox is one of only a few examples of a colonial organism, which behaves in some ways like a collection of individual cells, but in other ways like the specialized cells of a multicellular organism. Volvox colonies contain to 60, cells, each with two flagella, contained within a hollow, spherical matrix composed of a gelatinous glycoprotein secretion.

Individual Volvox cells move in a coordinated fashion and are interconnected by cytoplasmic bridges. Only a few of the cells reproduce to create daughter colonies, an example of basic cell specialization in this organism.

Volvox aureus is a green alga in the supergroup Archaeplastida. This species exists as a colony, consisting of cells immersed in a gel-like matrix and intertwined with each other via hair-like cytoplasmic extensions. True multicellular organisms, such as the sea lettuce, Ulva , are represented among the chlorophytes.

In addition, some chlorophytes exist as large, multinucleate, single cells. Species in the genus Caulerpa exhibit flattened, fern-like foliage and can reach lengths of 3 meters. Caulerpa species undergo nuclear division, but their cells do not complete cytokinesis, remaining instead as massive and elaborate single cells. Caulerpa taxifolia is a chlorophyte consisting of a single cell containing potentially thousands of nuclei. Amoebozoa are a type of protist that is characterized by the presence of pseudopodia which they use for locomotion and feeding.

Protists are eukaryotic organisms that are classified as unicellular, colonial, or multicellular organisms that do not have specialized tissues. This identifying property sets protists apart from other organisms within the Eukarya domain. The amoebozoans are classified as protists with pseudopodia which are used in locomotion and feeding.

Amoebozoans live in marine environments, fresh water, or in soil. In addition to the defining pseudopodia, they also lack a shell and do not have a fixed body. The pseudopodia which are characteristically exhibited include extensions which can be tube-like or flat lobes, rather than the hair-like pseudopodia of rhizarian amoeba. Rhizarian amoeba are amoeboids with filose, reticulose, or microtubule-supported pseudopods and include the groups: Cercozoa, Foraminifera, and Radiolaria and are classified as bikonts.

The Amoebozoa include several groups of unicellular amoeba-like organisms that are free-living or parasites that are classified as unikonts. The best known and most well-studied member of this group is the slime mold. Additional members include the Archamoebae, Tubulinea, and Flabellinea. Pseudopodia structures : Amoebae with tubular and lobe-shaped pseudopodia, such as the ones seen under this microscope, would be morphologically classified as amoebozoans.

A subset of the amoebozoans, the slime molds, has several morphological similarities to fungi that are thought to be the result of convergent evolution. For instance, during times of stress, some slime molds develop into spore -generating fruiting bodies, similar to fungi.

The slime molds are categorized on the basis of their life cycles into plasmodial or cellular types. Plasmodial slime molds are composed of large, multinucleate cells that move along surfaces like an amorphous blob of slime during their feeding stage. Food particles are lifted and engulfed into the slime mold as it glides along.

Upon maturation, the plasmodium takes on a net-like appearance with the ability to form fruiting bodies, or sporangia, during times of stress.

Haploid spores are produced by meiosis within the sporangia. These spores can be disseminated through the air or water to potentially land in more favorable environments. If this occurs, the spores germinate to form ameboid or flagellate haploid cells that can combine with each other and produce a diploid zygotic slime mold to complete the life cycle.

Badhamia utricularis : Badhamia utricularis: an example of a plasmodial slime mold with the ability to form a fruiting body. The cellular slime molds function as independent amoeboid cells when nutrients are abundant.

When food is depleted, cellular slime molds pile onto each other into a mass of cells that behaves as a single unit called a slug. Some cells in the slug contribute to a 2—3-millimeter stalk, drying up and dying in the process. Cells atop the stalk form an asexual fruiting body that contains haploid spores. As with plasmodial slime molds, the spores are disseminated and can germinate if they land in a moist environment. One representative genus of the cellular slime molds is Dictyostelium, which commonly exists in the damp soil of forests.

Plasmodial slime mold: Physarum polycephalum : Physarum polycephalum is an example of a cellular slime mold. The Archamoebae are a group of Amoebozoa distinguished by the absence of mitochondria. They include genera that are internal parasites or commensals of animals Entamoeba and Endolimax.

A few species are human pathogens, causing diseases such as amoebic dysentery. The other genera of archamoebae live in freshwater habitats and are unusual among amoebae in possessing flagella. Most have a single nucleus and flagellum, but the giant amoeba, Pelomyxa , has many of each. The Tubulinea are a major grouping of Amoebozoa, including most of the larger and more familiar amoebae like Amoeba , Arcella , and Difflugia. During locomotion, most Tubulinea have a roughly cylindrical form or produce numerous cylindrical pseudopods.

Each cylinder advances by a single central stream of cytoplasm, granular in appearance, and has no subpseudopodia. This distinguishes them from other amoeboid groups, although in some members this is not the normal type of locomotion. Privacy Policy.