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61 Cards in this Set
- Front
- Back
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What Makes a Eukaryote?
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1)cytoskeleton
2) flagella or Cilia 3) endomembrane system 4) Primary genome 5)Chromosomes segregate during somatic growth (or unicellular asexual reproduction) via the process of mitosis. 6)Mitochondria 7)Unique 80S ribosomes: |
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cytoskeleton
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consisting of tubulin-based microtubules and actin-based microfilaments
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flagella (or their shortened versions, cilia)
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constructed of an axoneme of 9 peripheral microtubular doublets and 2 central microtubules
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An endomembrane system
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consisting of endoplasmic reticulum, Golgi bodies, vacuoles, lysosomes, peroxisomes, and the nuclear envelope
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Primary genome
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Primary genome of each cell consists of multiple, linear chromosomes contained within a membrane-bound nucleus.
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Mitochondria
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energy-transducing organelles bounded by two membranes
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Unique 80S ribosomes
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each consistis of four molecules of RNA complexed with many proteins. Functional whole consists of a 40S small and a 60S large subunit
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Most eukaryotes are single-celled organisms known as _____?
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Protists
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Two processes probably contributed to the origin of eukaryotic cells:
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Autogeny & Endosymbiosis
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Autogeny
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Extensive inpocketing of the external plasma membrane formed a complex internal network of membranes.
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Endosymbiosis
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First proposed by Lynn Margulis, this model proposes that small, energy-transducing prokaryotes either
were engulfed as prey by took up residence as internal, mutualistic symbionts inside ...larger prokaryotes, where they survived and thrived. Eventually, host and symbiont became inextricably linked in a mutually beneficial symbiosis. |
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Evidence for Endosymbiosis:
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1)Similar symbioses exist today (e.g. Giardia, a basal (i.e., very primitive) flagellated protist has symbiotic, energy-transducing bacteria instead of mitochondria and two haploid nuclei.)
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Evidence for Endosymbiosis:
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2) Some extant species of autotrophic cyanobacteria and heterotrophic bacteria strongly resemble chloroplasts and mitochondria, respectively.
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Evidence for Endosymbiosis:
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3)Mitochondrial and chloroplast membrane enzymes are more similar to those of prokaryotes than they are to eukaryotic membrane enzymes
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Evidence for Endosymbiosis:
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4)Mitochondrial and chloroplast ribosome enzymes are more similar to those of prokaryotes than they are to eukaryotic ribosome enzymes
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Evidence for Endosymbiosis:
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5)Mitochondria and chloroplasts have their own genome, separate from and largely independent of the nuclear genome.
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Evidence for Endosymbiosis:
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6)mtDNA and cpDNA are circular, like that of prokaryotes. (Though there may be multiple copies of the genome, all are genetically identical within a given cell. Hence, these organelles are--like bacteria--haploid.)
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Evidence for Endosymbiosis:
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7)mtDNA and cpDNA circular chromosomes have no associated histones or RNA (as linear, nuclear chromosomes do)
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Evidence for Endosymbiosis:
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8)Mitochondrial and chloroplast cytochromes and other transport proteins are made in situ, with little interaction from nuclear genome enzyme products.
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Evidence for Endosymbiosis:
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9)Mitochondria and chloroplasts reproduce via binary fission very similar to that seen in prokaryotes.
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Evidence for Endosymbiosis:
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10)Nucleus, mitochondria and chloroplasts all have a double membrane.
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Viruses
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Have been implicated in the evolution of the eukaryote genome (and phenotype). Sequestered and silenced for thousands of years, they make up as much as 8% of the human genome.
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Protists
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-range in size from the mighty, shelled, multinucleate Syringammina fragilissima (more than 20mm!) to the tiny Ostreococcus tauri (1 μm).
-Other than unicellularity, few characters link the protists. -Most are unicellular, but some may be aggregate, colonial, or colonial with a cellular division of labor. -They live in both terrestrial and aquatic habitats (though they generally need moisture when in their active life cycle stages.) -Some are extremely complex--the most complex living cells. |
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Protists may be...
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photoautotrophs
chemoheterotrophs predatory parasitic commensal mutualistic detritivorous (feeding on dead, organic matter and turning it into smaller organic molecules, but NOT decomposing it) mixotrophs (a little of both) May be... -asexual -sexual - with protists in every category of sexual reproduction |
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The earliest Eukaryotes were...?
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Protists
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The oldest known eukaryote fossil is?
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(2.1 billion years old, found in pre-Cambrian fossil beds in Michigan) are called acritarchs.
acrit = "confused" (Gr) arch = "beginning" (Gr.) |
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The main protist clades (at the moment) are...
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-Excavates
-Chromalveolates -Rhizaria -Unikonts (This containing group also includes Animals and Fungi) -Archaeplastida (This group also includes Plants) |
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Excavata
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This group is named for a groove that appears to be "excavated" on on side of the cell.
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Excavata group:
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it has typical eukaryotic flagella
mitochondria are reduced, and lack DNA mitochondria are reduced, and lack DNA Giardia lacks any type of plastids lacks electron transport chain proteins or any enzymes associated with aerobic respiration. usually lives in anaerobic conditions has a very simple cytoskeleton contains two haploid nuclei pathogenic; causes giardiasis |
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giardiasis
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Giardia is a microscopic parasite that causes the diarrheal illness known as giardiasis. Giardia (also known as Giardia intestinalis, Giardia lamblia, or Giardia duodenalis) is found on surfaces or in soil, food, or water that has been contaminated with feces (poop) from infected humans or animals.
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Trichomonas vaginalis
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is another opportunistic pathogen (found in the human female vagina) that shares many primitive characters with Giardia.
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Trichonympha and Personympha
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are two parabasalids that make life possible for termites (endosymbionts in the intestine, they digest cellulose, which termites cannot)
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Euglena
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is a ubiquitous mixotroph that some of us remember from after Hurricane Andrew.
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kinetoplastids
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(such as Trypanosoma spp., the causative agents of such deadly diseases as Chaga's Disease, leishmaniasis and "Sleeping Sickness", more accurately known as African Trypanosomiasis.)
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The flagellum
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The flagellum (and its shorter cousin, the cilium is a very ancient, widespread eukaryotic structure) It gives little information useful for classifying anything with a flagellum into a less inclusive taxon.
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Chromalveolata
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This diverse group includes not only some of the most important photoautotrophs in the biosphere (diatoms; macroalgae such as "brown algae"), but also economically important pathogens. It is currently divided into two clades, the Alveolata and the Stramenopila.
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Alveolata
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These are linked by the presence of alveoli under the plasma membrane, which is highly complex in function and anatomy.
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Alveolata group includes:
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Dinoflagellates
economically important Apicomplexans, parasites formerly known as "sporozoans". the hugely diverse ciliates |
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Dinoflagellates
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These organisms are responsible for seasonal red tides that can cause massive die-offs of fish and other marine animals. They are also indirectly responsible for the most common form of non-bacterial seafood poisoning in the U.S., ciguatera. But they're not all bad, of course.
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"sporozoans"
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economically important Apicomplexans, parasites formerly known as "sporozoans". These all possess a modified Golgi apparatus, the apicoplast, at the apex of the cell, which facilitates invasion of a host cell. All apicomplexans are intracellular parasites of animals (coccidia, gregarines, plasmodia, etc.)
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Ciliates
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the hugely diverse ciliates (among the most complex of all protists--and possibly all cell types, in general)
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Stramenopila
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Their name comes from the Latin stramen ("straw") and pilos ("hair")). The taxon gets its name from its fuzzy flagellum, which is often paired with a smooth one. Flagellated cells occur in all members of this taxon, though in some highly derived groups, they occur only during reproductive cycles and function as gametes. This group includes the Diatoms.
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Diatoms
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The diatoms are one of the largest and ecologically most significant groups of organisms on Earth. They are also one of the easiest to recognize, because of their unique cell structure, silicified cell wall and life cycle.
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Golden Algae
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Golden-brown colored photosynthetic eukaryotes that are filamentous, pseudofilamentous, coccoid or capsoid in nature. Most described from fresh or brackish waters.
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Brown Algae
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Kelps
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Water molds
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Labyrinthulomycetes are mainly marine protists that are heterotrophic zoospore producing organisms.
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haptophytes
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unicellular algae that produce plated shells (coccoliths) that presumably protect them from predators. The calcium carbonate "skeletons" of a famous haptophyte, >Emiliana huxleyi are the primary component of the White Cliffs of Dover
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Rhizaria
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Once subsumed within the Chromalveolata, these specialized amoebas are currently grouped within a putatively monophyletic taxon.
Many Rhizarians secrete ornate shells, through which highly derived, threadlike pseudopods emerge. |
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pseudopods
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The pseudopods facilitate movement, may be involved in prey capture, and also provide buoyancy via greatly increased surface area.
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Cercozoa
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These little guys are ubiquitous in marine, freshwater, and soil ecosystems. Most are heterotrophs, and some are parasites or predators. They may be amoeboid, flagellate, or alternate between those two forms.
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Foraminifera
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These manufacture a test (shell) of calcium carbonate (CaCO3). Found more commonly in warm water than cold water areas.
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Radiolaria
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These manufacture a test of silica (glass!). Found more commonly in cold water and fresh water.
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Archaeplastida
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This clade includes the Red Algae (Rhodophyta) and the Green Plants.
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Rhodophyta
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The Rhodophyta form a monophyletic clade united by the synapomorphic appearance of
phycoerythrin phycocyanin allophycocyanins |
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phycobilisomes.
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phycoerythrin
phycocyanin allophycocyanins all contained in specialized light-collecting systems known as phycobilisomes. These are found elsewhere in the cyanobacteria, strongly suggesting that a secondary endosymbiosis involving cyanobacteria gave rise to the Rhodophytes. |
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Rhodophytes
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lack flagella
lack centrioles |
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Agar
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Chemically, agar is a polymer made up of subunits of the sugar galactose, and is a component of the cell walls of several species of red algae that are usually harvested in eastern Asia and California. Dissolved in boiling water and cooled, laboratory agar looks gelatinous. Although agar's chief use is as a culture medium for various microorganisms, particularly for bacteria, its other less well-known uses include serving as a thickening for soups and sauces, in jellies and ice cream, in cosmetics, for clarifying beverages, and for sizing fabrics.(1)
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Unikonta
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This clade includes several groups of protists as well as the Fungi and Animalia. Amoebozoa
Yes, it's true. We are closely related to amoebas. And, specifically, to Entamoebas. |
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Slime Molds
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But we also share a common ancestor with slime molds, whose systematics are still being worked out.
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Choanoflagellates
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Our closest relations, though, are unikont protists known as choanoflagellates. Among all the protists, it is with these small, colonial creatures that we are believed to share a most recent common ancestor.
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Choanoflagellates
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Choanoflagellates are free-living, single-cell and colony forming eukaryotes ubiquitous in aquatic environments. As their name implies, choanoflagellates (collared flagellates) have a distinctive cell morphology characterized by an ovoid or spherical cell body 3-10 µm in diameter with a single apical flagellum surrounded by a collar of 30-40 microvilli (see figure). Movement of the flagellum creates water currents that can propel free-swimming
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