Term
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Definition
Eukaryotes that are neither plants, animals, or fungi are called protists, or microbial eukaryotes (though not all are microbial).
They do not constitute a clade, they are paraphyletic.
Their true phylogeny is the subject of research and debate. |
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Term
|
Definition
Many are constituents of plankton—
free floating, microscopic, aquatic
organisms.
Plankton that are photosynthetic are called phytoplankton |
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Term
| Plankton as primary producers |
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Definition
In marine food webs, phytoplankton are the primary producers.
Diatoms (a clade) are
-dominant in the phytoplankton.
-They do one-fifth of the carbon
fixation on earth.
The primary producers are consumed by heterotrophs. |
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Term
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Definition
Endosymbiosis
-in which one organism lives inside
another,
-is common in microbial eukaryotes
Dinoflagellates are common endosymbionts in animals and other microbial eukaryotes;
some are photosynthetic. |
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Term
| Examples of Endosymbiosis Relationships |
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Definition
Many radiolarians have photosynthetic endosymbionts.
Often, both organisms benefit from the relationship.
Some dinoflagellates live as endosymbionts in corals. |
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Term
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Definition
Pathogens:
Plasmodium
—cause of malaria
-Part of its life cycle is spent as
a parasite in red blood cells
-Female Anopheles mosquito is the vector
-takes up Plasmodium gametes with the
blood
-zygotes form in mosquito gut.
-Plasmodium is passed to another human. |
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Term
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Definition
Trypanosomes (kinetoplastids) are some of the most deadly organisms on Earth
causing
-sleeping sickness,
-leishmaniasis, and
-Chagas’ disease |
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Term
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Definition
Some chromalveolates, including
-diatoms
-dinoflagellates, and
-haptophytes
can form “red tides.”
Color is from pigments in dinoflagellates. Cell concentrations are extremely high.
Some produce neurotoxins that kill fish.
Gonyaulax produces a toxin that accumulates in shellfish. |
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Term
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Definition
Diatoms store oil as an energy reserve.
Over millions of years, diatoms have died and sunk to the ocean floor
and through chemical and physical changes form petroleum and natural gas deposits. |
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Term
|
Definition
Foraminiferans secrete shells of calcium carbonate.
Discarded shells make up extensive deposits of limestone.
Some beach sands are made of fragments of foram shells.
Foram shells are also used to date and characterize sedimentary rocks,
and are used to infer temperatures from the past. |
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Term
The main events of how eukaryotic
cells arose |
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Definition
-Origin of a flexible cell surface
-Origin of a cytoskeleton
-Origin of a nuclear envelope
-Appearance of digestive vesicles or
vacuoles
-Endosymbiotic acquisition of some
organelles |
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Term
Info about
flexible cell surface |
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Definition
Flexible cell surface:
-Prokaryotic cell wall was lost
-cells can grow larger.
-As cell size increases,
surface area-to-volume ratio
decreases
-but with a flexible surface
infolding can occur
creating more surface area.
-A flexible cell surface also allowed endocytosis to develop. |
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Term
cytoskeleton info for development
of eukaryotic cells |
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Definition
A cytoskeleton
-provided cell support
-allowed cells to change shape
-and move materials around the cell
-including daughter chromosomes.
In some cells microtubules gave rise to flagella. |
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Term
Possible first stage in
development of a nucleus
in eukaryotic cells |
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Definition
-The nuclear envelope may have developed from the plasma membrane.
-The DNA of a prokaryote is attached to the plasma membrane
-infolding of the membrane could have been the first step in development of the nucleus |
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Term
after flexible cell wall,
what was probably next step in
developing a eukaryotic cell? |
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Definition
The next step was probably phagocytosis—the ability to engulf and digest other cells.
The first true eukaryotes had a cytoskeleton and nuclear envelope; they probably had ER, Golgi apparatus, and perhaps flagella. |
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Term
| Development of mitochondria |
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Definition
Cyanobacteria were producing oxygen
at some point, some Eukarya incorporated proteobacteria that evolved into mitochondria—the endosymbiotic theory.
The function of mitochondria initially might have been to detoxify O2 by reducing it to water.
Later this became associated with ATP production. |
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Term
| Development of chloroplasts |
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Definition
Some eukaryotes incorporated a prokaryote related to today’s cyanobacteria
which developed into chloroplasts.
Evolution of chloroplasts probably occurred in a series of endosymbiotic events.
Evidence comes from nucleic acid sequencing and electron microscopy. |
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Term
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Definition
Primary endosymbiosis
All chloroplasts descended from a
gram-negative cyanobacterium
with an inner and outer membrane.
A small amount of peptidoglycan from the bacterial cell wall is found today in the glaucophytes—the first group to branch off. |
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Term
| Primary endosymbiosis gave rise to chloroplasts of |
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Definition
Primary endosymbiosis gave rise to chloroplasts of
-green algae (chlorophytes and
charophytes)
-and the red algae.
Photosynthetic land plants arose from a green algal ancestor.
Red algal chloroplasts retain some pigments that were present in the original cyanobacterium. |
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Term
| Secondary and tertiary endosymbiosis gave rise to: |
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Definition
Secondary and tertiary endosymbiosis gave rise to chloroplasts in the other microbial eukaryote groups.
The euglenid ancestor engulfed a chlorophyte, retaining the chloroplasts.
Euglenid chloroplasts have the same pigments as green algae and land plants, and has a third membrane. |
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Term
Example of primary endosymbiosis
and dev of a chloroplast |
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Definition
The cryptophytes (a clade of chromalveolates)
engulfed a red algal cell that became the chloroplast.
These chloroplasts contain reduced red algal nuclei, and appear to be a sister clade to all other chromalveolate chloroplasts. |
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Term
| Dinoflagellates engaged in tertiary endosymbiosis: |
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Definition
Dinoflagellates engaged in tertiary endosymbiosis:
Karenia brevis
-lost its chloroplast
-and took up a haptophyte
(a result of secondary
endosymiosis).
One case of sequential secondary endosymbiosis—
-a dinoflagellate lost its red
algal chloroplast and
-took up a chlorophyte. |
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Term
| Uncertainties remain about the origins of eukaryotic cells. |
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Definition
Uncertainties remain about the origins of eukaryotic cells.
Lateral gene transfer complicates the study of relationships.
Endosymbiosis does not account for all bacterial genes in eukaryotes.
A recent suggestion is that Eukarya arose from the fusion of a gram-negative bacterium and an archaean |
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Term
| Microbial eukaryotes have evolved a diversity of lifestyles. |
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Definition
Microbial eukaryotes have evolved a diversity of lifestyles.
Most are aquatic, marine and freshwater;
but also damp soils and decaying organic matter.
Some are photosynthetic, some are heterotrophs,
some can switch between modes. |
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Term
Lumping together groups
of microbial eukaryotes |
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Definition
Some used to be considered animals, and are called protozoans.
But this term lumps phylogenetically unrelated groups.
Most protozoans are ingestive heterotrophs.
The term algae also lumps many groups of photosynthetic microbial eukaryotes and does not reflect phylogeny. |
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Term
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Definition
Amoeboid motion
—cells form pseudopods that are extensions of the cell.
A network of cytoskeletal microfilaments squeezes the cytoplasm forward. |
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Term
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Definition
Cilia and flagella developed from microtubules.
Cilia beat in a coordinated fashion; move cell forward or backward.
Flagella have whip-like movement. Some pull, some push the cell forward.
Flagella have a 9 + 2 arrangement of microtubules. |
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Term
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Definition
Vacuoles increase effective surface area in large cells.
Contractile vacuoles in freshwater microbial eukaryotes such as Paramecium are used to excrete excess water. |
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Term
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Definition
Food vacuoles are formed by Paramecium and others when solid food particles are ingested by endocytosis.
The food is digested in the vacuole.
Smaller vesicles pinch off—increasing surface area for products of digestion to be absorbed by the rest of the cell. |
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Term
| cell surfaces (strengthening) |
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Definition
Many microbial eukaryotes have diverse means of strengthening their surfaces.
Paramecium has a covering of surface proteins called a pellicle, making it flexible but resilient.
Other groups secrete a “shell,” such as foraminiferans. |
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Term
| examples of shells to strengthen cell surfaces |
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Definition
Some amoebas make a “shell” or test from bits of sand beneath the plasma membrane.
Diatoms form glassy cell walls of silica. These walls are exceptionally strong, and perhaps enhanced defense against predators. |
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Term
Most microbial eukaryotes have both sexual and asexual reproduction.
Asexual processes: |
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Definition
Most microbial eukaryotes have both sexual and asexual reproduction.
Asexual processes:
Binary fission—equal splitting; mitosis followed by cytokinesis.
Multiple fission—splitting into more than two cells.
Budding—outgrowth of a new cell from the surface of an old cell.
Spores—specialized cells that are capable of growing into a new individual. |
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Term
ciliate clade
and genetic information |
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Definition
The ciliate clade (such as Paramecium) have a single macronucleus and one to several micronuclei.
The macronucleus
-contains many copies of the genetic
information
-packaged into units and
-regulates the life of the cell.
Micronuclei are essential for genetic recombination. |
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Term
|
Definition
In conjugation
-two Paramecia line up together
-the oral groove regions fuse, and -nuclear material is exchanged and
reorganized
Each cell gets two haploid nuclei, one from each cell.
These fuse to form a new diploid micronucleus.
Conjugation is a sexual process, but it is not reproductive.
Asexual clones must periodically conjugate. |
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Term
| alternation of generations |
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Definition
In alternation of generations,
a diploid spore-forming organism gives rise to a haploid gamete-forming organism.
When haploid gametes fuse (fertilization or syngamy) a diploid individual is formed.
The haploid or diploid organism, or both, may reproduce asexually. |
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Term
individual players
in
alternations of generations |
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Definition
In multicellular organisms
the sporophyte is the multicellular diploid generation
the gametophyte is the multicellular haploid generation.
heteromorphic--The generations are different morphologically
Isomorphic—the generations have similar morphology. |
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Term
the spores
and
the gametes |
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Definition
Specialized cells in the sporophyte (sporocytes) divide meiotically to produce haploid spores.
The spores germinate and divide mitotically to produce the haploid gametophyte generation.
Gametes produced by the gametophyte generation must fuse to form a new sporophyte generation. |
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Term
| Life cycles in chlorophytes: |
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Definition
Life cycles in chlorophytes:
Ulva lactuca (sea lettuce) has alternation of generations.
-The haploid spores have four flagella—zoospores.
-They lose flagella and divide mitotically to form the sporophyte.
-Isomorphic—both generations look alike. |
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Term
|
Definition
Isogamous—the gametes are the same morphologically.
Anisogamous—female and male gametes are different. |
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Term
|
Definition
In haplontic life cycles,
a multicellular haploid individual produces gametes that fuse to form a zygote.
The zygote undergoes meiosis to form haploid spores
these develop into a new haploid individual.
The zygote is the only diploid part of the life cycle. |
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Term
|
Definition
In diplontic life cycles,
meiosis of diploid sporocytes produces haploid gametes.
Gametes fuse to form a diploid zygote that develops mitotically into a new diploid individual.
Gametes are the only haploid part of the life cycle.
Most animals have this type of life cycle |
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Term
| Many microbial eukaryote life cycles require participation of different host species. |
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Definition
Many microbial eukaryote life cycles require participation of different host species.
Examples: Plasmodium and the trypanosomes
Advantages of such a life cycle are not clear.
The sexual part of the life cycle takes place in the insect vectors. |
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Term
| Most eukaryotes can be divided into five groups: |
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Definition
Most eukaryotes can be divided into five groups:
-chromalveolates
-Plantae
-excavates
-Rhizaria
-unikonts. |
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Term
|
Definition
Chromalveolates
Includes haptophytes—
many are “armored” with elaborate scales. |
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Term
|
Definition
Alveolates:
synapomorphy that distinguishes this clade
is presence of alveoli or sacs beneath surface of plasma membrane.
All unicellular;
includes dinoflagellates, apicomplexans, and ciliates. |
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Term
|
Definition
Most dinoflagellates
are marine and are important primary producers.
Mixture of pigments give them a golden brown color.
Some are endosymbionts in corals and other invertebrates and microbial eukaryotes.
Some are nonphotosynthetic parasites
Dinoflagellates have two flagella, one in an equatorial groove, the other in a longitudinal groove.
Some can take different forms, including amoeboid, (e.g., Pfiesteria piscicida).
When present in large numbers, they can stun fish and feed on them. |
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Term
|
Definition
Apicomplexans are all parasites.
They have a mass of organelles at one tip—the apical complex.
The organelles help the parasite enter the host’s cells.
They have complex life cycles, often with two different hosts, (e.g., Plasmodium).
They lack contractile vacuoles;
have a reduced, nonfunctional chloroplast. |
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Term
|
Definition
Ciliates
have numerous cilia, the structure is identical to flagella.
Most are heterotrophic; very diverse group.
Have complex body form; two types of nuclei. |
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Term
Paramecium & Trichocysts
about cilia |
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Definition
Paramecium has a pellicle composed of an outer membrane and an inner layer of membrane-enclosed sacs (alveoli) that surround bases of cilia.
Trichocysts in the pellicle are defensive organelles, they are like sharp darts on the tip of an expanding filament.
Locomotion by cilia is more precise than by flagella. |
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Term
|
Definition
Stramenopiles:
synapomorphy that defines them is rows of tubular hairs on the longer of the two flagella.
Some stramenopiles lack flagella but are descended from ancestors that had them.
Includes diatoms, brown algae, oomycetes, and slime nets. |
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Term
|
Definition
Diatoms are unicellular, but many associate in filaments.
Have carotenoids and appear yellow or brown.
All make chrysolaminarin (a carbohydrate) and oils as storage products.
Only male gametes have flagella |
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Term
|
Definition
Diatoms deposit silicon in their cell walls.
They are constructed in two pieces, like a petri plate.
They are either bilaterally or radially symmetrical.
Asexual reproduction is by binary fission. Both top and bottom of the “petri plate” become the tops of the new daughter cells. |
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Term
| Diatoms & sexual reproduction |
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Definition
Sexual reproduction results in larger cells:
gametes fuse to form a zygote which grows substantially before a new cell wall is laid down.
Diatoms are major primary producers in the ocean, and also in fresh waters. |
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Term
|
Definition
Some diatoms form large blooms in the ocean that are not grazed by copepods, the usual predator.
The cells die and sink to the ocean floor.
When diatoms make up a large proportion of the copepod diet, they become toxic,
preventing copepod populations from taking advantage of the food available in a diatom bloom. |
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Term
|
Definition
Diatom cell walls resist decomposition, and become fossilized in sedimentary rock.
Diatomaceous earth is from rock composed almost entirely of diatom cell walls.
It is used in insulation, filtration, metal polishing, and as an insecticide. |
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Term
|
Definition
Brown algae are multicelluar;
some get very large (e.g., the giant kelp).
The carotenoid fucoxanthin imparts the brown color.
Almost exclusively marine.
Sargassum forms dense mats in the Sargasso Sea in the mid-Atlantic. |
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Term
| How do most brown algae attach to rocks? |
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Definition
Most brown algae attach to rocks by a holdfast that glues it to the rock.
The “glue” is alginic acid—a gummy polymer of sugars.
Also holds cells and filaments together.
It is harvested and used as an emulsifier in ice cream, cosmetics, and other products. |
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Term
| Some brown algae have specialized organs |
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Definition
Some brown algae have specialized organs
—stem-like stalks and leaf-like blades,
and gas-filled bladders that act as floats.
Some of the larger species have tissue differentiation.
Giant kelps have tubular cells that resemble nutrient-conducting tissue of land plants, called trumpet cells. |
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Term
|
Definition
Oomycetes:
water molds and downy mildews;
nonphotosynthetic.
Water molds are absorptive heterotrophs (e.g., Saprolegnia).
Once were classed as fungi, but are unrelated.
Some are coenocytes—many nuclei enclosed in one plasma membrane |
|
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Term
| more info on oomycetes and water molds |
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Definition
Oomycetes are diploid throughout most of their life cycle, and have flagellated reproductive cells.
Water molds are saprobic (feed on dead organic matter). A few are terrestrial, and a few of those are parasites on plants. |
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Term
|
Definition
The Plantae consist of several clades;
--Glaucophytes
--Red algae
--Chlorophytes
--Land plants
--Charophytes
all chloroplasts trace back to a single incidence of endosymbiosis. |
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Term
|
Definition
Glaucophytes are unicellular, freshwater organisms;
probably first group to diverge.
The chloroplast retains a bit of peptidoglycan between the inner and outer membrane.
They probably resemble the common ancestor of all Plantae. |
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Term
|
Definition
Most red algae are marine and multicellular.
Red pigment is phycoerythrin.
Also have phycocyanin, chlorophyll a, and carotenoids.
They can vary the relative amounts of pigments depending on light conditions.
In deep water, low light conditions, they increase the amount of phycoerythrin and look more red. |
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Term
| Red algae storage product |
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Definition
Red algae storage product is floridean starch—very small glucose chains.
They have no flagellated cells at any time in the life cycle.
Some species secrete calcium carbonate, and enhance growth of coral reefs. |
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Term
Some red algae
source of agar
ancestor to the chloroplasts |
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Definition
Some red algae produce mucilaginous polysaccharides, which form solid gels and are the source of agar.
A red alga was the ancestor to the chloroplasts of photosynthetic chromalveolates by secondary endosymbiosis. |
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Term
|
Definition
The chlorophytes are
the sister group to charophytes and land plants
Synapomorphies include chlorophyll a and b, and starch as a storage product.
More than 17,000 species; marine, freshwater, and terrestrial.
Unicellular to large multicellular forms. |
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Term
| Some chlorophytes form colonies of cells |
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Definition
Some chlorophytes form colonies of cells that show the possible first step for cell and tissue differentiation.
In Volvox colonies, some cells are specialized for reproduction.
Other species are multicellular,
some are coenocytic;
Acetabularia is a single giant cell a few centimeters long. |
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Term
| Diplomonads and parabasalids: |
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Definition
Diplomonads and parabasalids:
-unicellular
-lack mitochondria.
Giardia lamblia is a diplomonad. It has two nuclei bounded by nuclear envelopes.
Trichomonas vaginalis is a parabasalid responsible for a sexually transmitted disease in humans. |
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Term
|
Definition
Heteroloboseans have amoeboid body form.
The free-living Naegleria can enter humans and cause a fatal disease of the nervous system. |
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Term
|
Definition
The euglenids have flagella.
Spiral strips of proteins under the plasma membrane control cell shape.
Some are photosynthetic, some always heterotrophic, and some can switch |
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Term
|
Definition
The kinetoplastids are
-unicellular parasites with
-two flagella and
-a single mitochondrion.
The mitochondrion contains a kinetoplast, a structure with multiple, circular DNA molecules and proteins.
Trypanosomes are kinetoplastids. |
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Term
|
Definition
Rhizaria
Unicellular, aquatic, have long thin pseudopodia. |
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Term
|
Definition
Some cercozoans are aquatic, others live in soil.
They have diverse forms and habitats.
One group has chloroplasts derived from a green alga by secondary endosymbiosis. |
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Term
|
Definition
Foraminiferans secrete shells of calcium carbonate.
Some live as plankton, others at the bottom of the sea.
Thread-like, branched pseudopods extend through numerous pores in the shell and form a sticky net that captures smaller plankton. |
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Term
|
Definition
Radiolarians have
thin, stiff pseudopods reinforced by microtubules.
The pseudopods increase surface area for exchange of materials; and help the cell float.
Exclusively marine,
most secrete glassy endoskeletons, many with elaborate designs. |
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Term
|
Definition
Unikonts:
single flagellum (if present |
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Term
|
Definition
Animals and fungi arose from a common ancestor within the opisthokont clade; sister to the amoebozoans.
Synapomorphy of the opisthokonts: if flagellum is present it is posterior (anterior in other eukaryotes).
Choanoflagellates are sister to the animals. Some are colonial and resemble a type of cell found in sponges. |
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Term
|
Definition
The amoebozoans have lobe-shaped pseudopods.
Loboseans, such as Amoeba proteus, are unicellular and do not aggregate.
Feed by phagocytosis, living as predators, parasites, or scavengers.
Some secrete shells or glue sand grains together to form a casing. |
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Term
|
Definition
There are two clades of slime molds.
All are motile,
ingest food by endocytosis,
form spores on stalks called fruiting bodies.
Slime molds are found in cool, moist habitats, primarily forests. |
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Term
|
Definition
Plasmodial slime molds
During the vegetative (feeding stage) they are coenocytes with many diploid nuclei that streams over the substrate in a network of strands called a plasmodium. |
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Term
|
Definition
Movement is by cytoplasmic streaming—outer cytoplasmic region becomes more fluid, and cytoplasm rushes in.
Microfilaments and a contractile protein called myxomyosin interact to produce the streaming movement.
As it moves, the plasmodium engulfs food particles by endocytosis. |
|
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Term
| plasmodiums when lack of food sources |
|
Definition
If there is food, a plasmodium can grow indefinitely.
When conditions become unfavorable,
--a resting form develops with hardened
components,
--called a sclerotium.
Becomes a plasmodium again when conditions are favorable. |
|
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Term
| plasmodiums as spore bearing fruiting bodies |
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Definition
Alternatively, the plasmodium transforms into spore-bearing fruiting bodies.
In the rigid stalks, walls form and thicken between nuclei.
Diploid nuclei undergo meiosis,
sporangia form at the tip of the stalk
and haploid nuclei in the sporangia form spores. |
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Term
| When plasmodium spores germinate |
|
Definition
The spores germinate into swarm cells—haploid cells that divide mitotically to form more swarm cells, or function as gametes.
Swarm cells can live as individuals, moving by flagella or pseudopods, or become walled, resistant cysts.
Two swarm cells can fuse to form a zygote, which forms a new plasmodium. |
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Term
| The vegetative unit of cellular slime molds |
|
Definition
The vegetative unit of cellular slime molds is an amoeboid cell.
The myxamoebas
--have a single haploid nucleus
--engulf food by endocytosis, and
--reproduce by fission.
This stage persists if food is available.
When conditions become unfavorable, the cells aggregate into a slug or pseudoplasmodium.
Individuals retain their plasma membranes. |
|
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Term
| cellular slime mold slugs |
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Definition
A slug (When conditions become unfavorable, the cells aggregate into a slug or pseudoplasmodium.) may migrate before coming to rest and forming fruiting bodies.
Cells at the top become spores.
Spores germinate and release myxamoebas when conditions are favorable.
Two myxamoebas may also fuse in sexual reproduction. |
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