Context: Apicoplasts have lost all photosynthetic function, and contain no photosynthetic pigments or true thylakoids. They are bounded by four membranes, but the membranes are not connected to the endoplasmic reticulum. The fact that apicomplexans still keep their nonphotosynthetic chloroplast around demonstrates how the chloroplast carries out important functions other than photosynthesis. Plant chloroplasts provide plant cells with many important things besides sugar, and apicoplasts are no different—they synthesize fatty acids, isopentenyl pyrophosphate, iron-sulfur clusters, and carry out part of the heme pathway. This makes the apicoplast an attractive target for drugs to cure apicomplexan-related diseases. The most important apicoplast function is isopentenyl pyrophosphate synthesis—in fact, apicomplexans die when something interferes with this apicoplast function, and when apicomplexans are grown in an isopentenyl pyrophosphate-rich medium, they dump the organelle.

Question: What do apicoplasts synthesize?

Question: What kind of diseases do drugs target apicoplasts for?

Question: What is the most important thing apicoplasts do?

Question: What are apicoplasts missing?

Question: How many membranes do apicoplasts have?


Context: The most common dinophyte chloroplast is the peridinin-type chloroplast, characterized by the carotenoid pigment peridinin in their chloroplasts, along with chlorophyll a and chlorophyll c2. Peridinin is not found in any other group of chloroplasts. The peridinin chloroplast is bounded by three membranes (occasionally two), having lost the red algal endosymbiont's original cell membrane. The outermost membrane is not connected to the endoplasmic reticulum. They contain a pyrenoid, and have triplet-stacked thylakoids. Starch is found outside the chloroplast An important feature of these chloroplasts is that their chloroplast DNA is highly reduced and fragmented into many small circles. Most of the genome has migrated to the nucleus, and only critical photosynthesis-related genes remain in the chloroplast.

Question: What is only found in peridinin-type chloroplasts?

Question: Where is Peridinin found?

Question: How are peridinin-type chloroplasts' thylakoids arranged?

Question: What have peridinin-type chloroplasts lost?


Context: The fucoxanthin dinophyte lineages (including Karlodinium and Karenia) lost their original red algal derived chloroplast, and replaced it with a new chloroplast derived from a haptophyte endosymbiont. Karlodinium and Karenia probably took up different heterokontophytes. Because the haptophyte chloroplast has four membranes, tertiary endosymbiosis would be expected to create a six membraned chloroplast, adding the haptophyte's cell membrane and the dinophyte's phagosomal vacuole. However, the haptophyte was heavily reduced, stripped of a few membranes and its nucleus, leaving only its chloroplast (with its original double membrane), and possibly one or two additional membranes around it.

Question: What lineage is Karlodinium in?

Question: What lineage is Karenia in?

Question: How many membranes does the haptophyte chloroplast have?

Question: What is tertiary endosymbiosis of haptophyte chloroplasts expected to create?


Context: Members of the genus Dinophysis have a phycobilin-containing chloroplast taken from a cryptophyte. However, the cryptophyte is not an endosymbiont—only the chloroplast seems to have been taken, and the chloroplast has been stripped of its nucleomorph and outermost two membranes, leaving just a two-membraned chloroplast. Cryptophyte chloroplasts require their nucleomorph to maintain themselves, and Dinophysis species grown in cell culture alone cannot survive, so it is possible (but not confirmed) that the Dinophysis chloroplast is a kleptoplast—if so, Dinophysis chloroplasts wear out and Dinophysis species must continually engulf cryptophytes to obtain new chloroplasts to replace the old ones.

Question: Where did Dinophysis get its chloroplasts from?

Question: What have the Dinophysis chloroplasts lost?

Question: What is the chloroplast of Dinophysis?

Question: What is left of the Dinophysis chloroplasts?


Context: Some dinophytes, like Kryptoperidinium and Durinskia have a diatom (heterokontophyte) derived chloroplast. These chloroplasts are bounded by up to five membranes, (depending on whether you count the entire diatom endosymbiont as the chloroplast, or just the red algal derived chloroplast inside it). The diatom endosymbiont has been reduced relatively little—it still retains its original mitochondria, and has endoplasmic reticulum, ribosomes, a nucleus, and of course, red algal derived chloroplasts—practically a complete cell, all inside the host's endoplasmic reticulum lumen. However the diatom endosymbiont can't store its own food—its starch is found in granules in the dinophyte host's cytoplasm instead. The diatom endosymbiont's nucleus is present, but it probably can't be called a nucleomorph because it shows no sign of genome reduction, and might have even been expanded. Diatoms have been engulfed by dinoflagellates at least three times.

Question: What is another word for diatom?

Question: What is Durinskia's chloroplast?

Question: How many membranes does Durinskia's chloroplast have?

Question: What is sometimes but not always counted regarding Durinskia's chloroplast membranes?

Question: Where does the diatom endosymbiont store starch?


Context: Lepidodinium viride and its close relatives are dinophytes that lost their original peridinin chloroplast and replaced it with a green algal derived chloroplast (more specifically, a prasinophyte). Lepidodinium is the only dinophyte that has a chloroplast that's not from the rhodoplast lineage. The chloroplast is surrounded by two membranes and has no nucleomorph—all the nucleomorph genes have been transferred to the dinophyte nucleus. The endosymbiotic event that led to this chloroplast was serial secondary endosymbiosis rather than tertiary endosymbiosis—the endosymbiont was a green alga containing a primary chloroplast (making a secondary chloroplast).

Question: Where do nucleomorph genes transfer to?

Question: What is the only dinophyte that has a non-rhodoplast chloroplast?

Question: What did Lepidodinium viride lose?

Question: What did Lepidodinium viride replace their original chloroplast with?

Question: What is a prasinophyte?


Context: While most chloroplasts originate from that first set of endosymbiotic events, Paulinella chromatophora is an exception that acquired a photosynthetic cyanobacterial endosymbiont more recently. It is not clear whether that symbiont is closely related to the ancestral chloroplast of other eukaryotes. Being in the early stages of endosymbiosis, Paulinella chromatophora can offer some insights into how chloroplasts evolved. Paulinella cells contain one or two sausage shaped blue-green photosynthesizing structures called chromatophores, descended from the cyanobacterium Synechococcus. Chromatophores cannot survive outside their host. Chromatophore DNA is about a million base pairs long, containing around 850 protein encoding genes—far less than the three million base pair Synechococcus genome, but much larger than the approximately 150,000 base pair genome of the more assimilated chloroplast. Chromatophores have transferred much less of their DNA to the nucleus of their host. About 0.3–0.8% of the nuclear DNA in Paulinella is from the chromatophore, compared with 11–14% from the chloroplast in plants.

Question: Where did most chloroplasts come from?

Question: What is different about Paulinella chromatophora?

Question: How many base pairs are there in Chromatophore DNA?

Question: How many protein-encoding genes are there in Chromatophore DNA?

Question: How many base pairs are there in Synechococcus DNA?


Context: Chloroplasts have their own DNA, often abbreviated as ctDNA, or cpDNA. It is also known as the plastome. Its existence was first proved in 1962, and first sequenced in 1986—when two Japanese research teams sequenced the chloroplast DNA of liverwort and tobacco. Since then, hundreds of chloroplast DNAs from various species have been sequenced, but they're mostly those of land plants and green algae—glaucophytes, red algae, and other algal groups are extremely underrepresented, potentially introducing some bias in views of "typical" chloroplast DNA structure and content.

Question:
What is chloroplast DNA abbreviated as?
What is a synonym for chloroplast DNA?
When was the plastome discovered?
When was the first plastome sequenced?
Who sequenced the first plastome?


Context: The inverted repeat regions are highly conserved among land plants, and accumulate few mutations. Similar inverted repeats exist in the genomes of cyanobacteria and the other two chloroplast lineages (glaucophyta and rhodophyceæ), suggesting that they predate the chloroplast, though some chloroplast DNAs have since lost or flipped the inverted repeats (making them direct repeats). It is possible that the inverted repeats help stabilize the rest of the chloroplast genome, as chloroplast DNAs which have lost some of the inverted repeat segments tend to get rearranged more.

Question:
What seldom mutates?
What have some inverted repeats become?
What could inverted repeats help do?


Context: The mechanism for chloroplast DNA (cpDNA) replication has not been conclusively determined, but two main models have been proposed. Scientists have attempted to observe chloroplast replication via electron microscopy since the 1970s. The results of the microscopy experiments led to the idea that chloroplast DNA replicates using a double displacement loop (D-loop). As the D-loop moves through the circular DNA, it adopts a theta intermediary form, also known as a Cairns replication intermediate, and completes replication with a rolling circle mechanism. Transcription starts at specific points of origin. Multiple replication forks open up, allowing replication machinery to transcribe the DNA. As replication continues, the forks grow and eventually converge. The new cpDNA structures separate, creating daughter cpDNA chromosomes.

Question: How is chloroplast replication observed?

Question: How many major chloroplast replication models have been suggested?

Question: What is a Cairns replication intermediate?

Question: What is a D-loop?

Question: How does the D-loop finish replicating?


Context: In cpDNA, there are several A → G deamination gradients. DNA becomes susceptible to deamination events when it is single stranded. When replication forks form, the strand not being copied is single stranded, and thus at risk for A → G deamination. Therefore, gradients in deamination indicate that replication forks were most likely present and the direction that they initially opened (the highest gradient is most likely nearest the start site because it was single stranded for the longest amount of time). This mechanism is still the leading theory today; however, a second theory suggests that most cpDNA is actually linear and replicates through homologous recombination. It further contends that only a minority of the genetic material is kept in circular chromosomes while the rest is in branched, linear, or other complex structures.

Question: What kind of gradients does cpDNA have?

Question: What makes DNA vulnerable to deamination?

Question: How does the secondary theory say most cpDNA is structured?

Question: How does the secondary theory say most cpDNA replicates?

Question: Where does the secondary theory say most genes are kept?


Context: One of competing model for cpDNA replication asserts that most cpDNA is linear and participates in homologous recombination and replication structures similar to bacteriophage T4. It has been established that some plants have linear cpDNA, such as maize, and that more species still contain complex structures that scientists do not yet understand. When the original experiments on cpDNA were performed, scientists did notice linear structures; however, they attributed these linear forms to broken circles. If the branched and complex structures seen in cpDNA experiments are real and not artifacts of concatenated circular DNA or broken circles, then a D-loop mechanism of replication is insufficient to explain how those structures would replicate. At the same time, homologous recombination does not expand the multiple A --> G gradients seen in plastomes. Because of the failure to explain the deamination gradient as well as the numerous plant species that have been shown to have circular cpDNA, the predominant theory continues to hold that most cpDNA is circular and most likely replicates via a D loop mechanism.

Question:
What is cpDNA's replication similar to?
What kind of cpDNA does maize have?
How is most plants' cpDNA arranged?
How does most plants' cpDNA replicate?


Context: Endosymbiotic gene transfer is how we know about the lost chloroplasts in many chromalveolate lineages. Even if a chloroplast is eventually lost, the genes it donated to the former host's nucleus persist, providing evidence for the lost chloroplast's existence. For example, while diatoms (a heterokontophyte) now have a red algal derived chloroplast, the presence of many green algal genes in the diatom nucleus provide evidence that the diatom ancestor (probably the ancestor of all chromalveolates too) had a green algal derived chloroplast at some point, which was subsequently replaced by the red chloroplast.

Question: What shows us lost chloroplasts?

Question: What do donated genes give evidence of?

Question: What kind of chloroplasts do diatoms have?

Question: What kind of chloroplasts did diatoms have but lost?


Context: Curiously, around half of the protein products of transferred genes aren't even targeted back to the chloroplast. Many became exaptations, taking on new functions like participating in cell division, protein routing, and even disease resistance. A few chloroplast genes found new homes in the mitochondrial genome—most became nonfunctional pseudogenes, though a few tRNA genes still work in the mitochondrion. Some transferred chloroplast DNA protein products get directed to the secretory pathway (though it should be noted that many secondary plastids are bounded by an outermost membrane derived from the host's cell membrane, and therefore topologically outside of the cell, because to reach the chloroplast from the cytosol, you have to cross the cell membrane, just like if you were headed for the extracellular space. In those cases, chloroplast-targeted proteins do initially travel along the secretory pathway).

Question: What is the status of most chloroplast genes in the mitochondrion?

Question: How much of the protein products of transferred genes don't go back to chloroplasts?

Question: What new tasks do the protein products of transferred genes take on?

Question: What do you have to cross to reach the chloroplast in many secondary plastids?


Context: After a chloroplast polypeptide is synthesized on a ribosome in the cytosol, an enzyme specific to chloroplast proteins phosphorylates, or adds a phosphate group to many (but not all) of them in their transit sequences. Phosphorylation helps many proteins bind the polypeptide, keeping it from folding prematurely. This is important because it prevents chloroplast proteins from assuming their active form and carrying out their chloroplast functions in the wrong place—the cytosol. At the same time, they have to keep just enough shape so that they can be recognized by the chloroplast. These proteins also help the polypeptide get imported into the chloroplast.

Question: What is the chloroplast polypeptide synthesized on?

Question: Where is the chloroplast polypeptide synthesized?

Question: What does Phosphorylation do?

Question: What is the benefit of polypeptide binding?


Context: In land plants, chloroplasts are generally lens-shaped, 5–8 μm in diameter and 1–3 μm thick. Greater diversity in chloroplast shapes exists among the algae, which often contain a single chloroplast that can be shaped like a net (e.g., Oedogonium), a cup (e.g., Chlamydomonas), a ribbon-like spiral around the edges of the cell (e.g., Spirogyra), or slightly twisted bands at the cell edges (e.g., Sirogonium). Some algae have two chloroplasts in each cell; they are star-shaped in Zygnema, or may follow the shape of half the cell in order Desmidiales. In some algae, the chloroplast takes up most of the cell, with pockets for the nucleus and other organelles (for example some species of Chlorella have a cup-shaped chloroplast that occupies much of the cell).

Question: How are chloroplasts in land plants usually shaped?

Question: How large across are chloroplasts in land plants?

Question: How thick are chloroplasts in land plants?

Question: What shape is Oedogonium's chloroplasts?

Question: What shape is Chlamydomonas's chloroplasts?


Context: There are some common misconceptions about the outer and inner chloroplast membranes. The fact that chloroplasts are surrounded by a double membrane is often cited as evidence that they are the descendants of endosymbiotic cyanobacteria. This is often interpreted as meaning the outer chloroplast membrane is the product of the host's cell membrane infolding to form a vesicle to surround the ancestral cyanobacterium—which is not true—both chloroplast membranes are homologous to the cyanobacterium's original double membranes.

Question: What is evidence chloroplasts descended from endosymbiotic cyanobacteria?

Question: What is incorrectly thought about the outer chloroplast membrane?

Question: How do both chloroplast membranes compare to cyanobacterium's original double membranes?


Context: The chloroplast double membrane is also often compared to the mitochondrial double membrane. This is not a valid comparison—the inner mitochondria membrane is used to run proton pumps and carry out oxidative phosphorylation across to generate ATP energy. The only chloroplast structure that can considered analogous to it is the internal thylakoid system. Even so, in terms of "in-out", the direction of chloroplast H+ ion flow is in the opposite direction compared to oxidative phosphorylation in mitochondria. In addition, in terms of function, the inner chloroplast membrane, which regulates metabolite passage and synthesizes some materials, has no counterpart in the mitochondrion.

Question: What is the chloroplast double membrane sometimes compared to?

Question: What does the inner mitochondria membrane do?

Question: What does oxidative phosphorylation do?

Question: What chloroplast structure is similar to the inner mitochondria membrane?

Question: What part of chloroplasts isn't similar to mitochondria?


Context: The chloroplast membranes sometimes protrude out into the cytoplasm, forming a stromule, or stroma-containing tubule. Stromules are very rare in chloroplasts, and are much more common in other plastids like chromoplasts and amyloplasts in petals and roots, respectively. They may exist to increase the chloroplast's surface area for cross-membrane transport, because they are often branched and tangled with the endoplasmic reticulum. When they were first observed in 1962, some plant biologists dismissed the structures as artifactual, claiming that stromules were just oddly shaped chloroplasts with constricted regions or dividing chloroplasts. However, there is a growing body of evidence that stromules are functional, integral features of plant cell plastids, not merely artifacts.

Question: What are more common in other plastids than chloroplasts?

Question: What is a stromule?

Question: Why do stromules exist?

Question: When were stromules discovered?


Context: Some chloroplasts contain a structure called the chloroplast peripheral reticulum. It is often found in the chloroplasts of C4 plants, though it has also been found in some C3 angiosperms, and even some gymnosperms. The chloroplast peripheral reticulum consists of a maze of membranous tubes and vesicles continuous with the inner chloroplast membrane that extends into the internal stromal fluid of the chloroplast. Its purpose is thought to be to increase the chloroplast's surface area for cross-membrane transport between its stroma and the cell cytoplasm. The small vesicles sometimes observed may serve as transport vesicles to shuttle stuff between the thylakoids and intermembrane space.

Question: Where is the chloroplast peripheral reticulum usually found?

Question: Where is the chloroplast peripheral reticulum less commonly found?

Question: What is a maze of membranous tubes?

Question: What does the chloroplast peripheral reticulum do?

Question: Where do transport vesicles move between?


Context: Chloroplasts have their own ribosomes, which they use to synthesize a small fraction of their proteins. Chloroplast ribosomes are about two-thirds the size of cytoplasmic ribosomes (around 17 nm vs 25 nm). They take mRNAs transcribed from the chloroplast DNA and translate them into protein. While similar to bacterial ribosomes, chloroplast translation is more complex than in bacteria, so chloroplast ribosomes include some chloroplast-unique features. Small subunit ribosomal RNAs in several Chlorophyta and euglenid chloroplasts lack motifs for shine-dalgarno sequence recognition, which is considered essential for translation initiation in most chloroplasts and prokaryotes. Such loss is also rarely observed in other plastids and prokaryotes.

Question: What do chloroplasts use their ribosomes for?

Question: How large are Chloroplast ribosomes?

Question: How large are Cytoplasmic ribosomes?

Question: What are some Chlorophyta and euglenid chloroplasts missing?

Question: Why is shine-dalgarno sequence recognition important?


Context: Plastoglobuli (singular plastoglobulus, sometimes spelled plastoglobule(s)), are spherical bubbles of lipids and proteins about 45–60 nanometers across. They are surrounded by a lipid monolayer. Plastoglobuli are found in all chloroplasts, but become more common when the chloroplast is under oxidative stress, or when it ages and transitions into a gerontoplast. Plastoglobuli also exhibit a greater size variation under these conditions. They are also common in etioplasts, but decrease in number as the etioplasts mature into chloroplasts.

Question:
What is a single Plastoglobuli called?
What shape are Plastoglobuli?
What are Plastoglobuli made of?
How large are Plastoglobuli?
What surrounds Plastoglobuli?


Context: Plastoglobuli were once thought to be free-floating in the stroma, but it is now thought that they are permanently attached either to a thylakoid or to another plastoglobulus attached to a thylakoid, a configuration that allows a plastoglobulus to exchange its contents with the thylakoid network. In normal green chloroplasts, the vast majority of plastoglobuli occur singularly, attached directly to their parent thylakoid. In old or stressed chloroplasts, plastoglobuli tend to occur in linked groups or chains, still always anchored to a thylakoid.

Question: What are Plastoglobuli attached to?

Question: What do Plastoglobuli exchange contents with?

Question: How are green chloroplasts' Plastoglobuli arranged?

Question: When do Plastoglobuli occur in linked groups?


Context: The chloroplasts of some hornworts and algae contain structures called pyrenoids. They are not found in higher plants. Pyrenoids are roughly spherical and highly refractive bodies which are a site of starch accumulation in plants that contain them. They consist of a matrix opaque to electrons, surrounded by two hemispherical starch plates. The starch is accumulated as the pyrenoids mature. In algae with carbon concentrating mechanisms, the enzyme rubisco is found in the pyrenoids. Starch can also accumulate around the pyrenoids when CO2 is scarce. Pyrenoids can divide to form new pyrenoids, or be produced "de novo".

Question:
Where are pyrenoids found?
What shape are pyrenoids?
What do pyrenoids look like?
What do pyrenoids store?
How can pyrenoids replicate?


Context: In the helical thylakoid model, grana consist of a stack of flattened circular granal thylakoids that resemble pancakes. Each granum can contain anywhere from two to a hundred thylakoids, though grana with 10–20 thylakoids are most common. Wrapped around the grana are helicoid stromal thylakoids, also known as frets or lamellar thylakoids. The helices ascend at an angle of 20–25°, connecting to each granal thylakoid at a bridge-like slit junction. The helicoids may extend as large sheets that link multiple grana, or narrow to tube-like bridges between grana. While different parts of the thylakoid system contain different membrane proteins, the thylakoid membranes are continuous and the thylakoid space they enclose form a single continuous labyrinth.

Question: In what model do grana look like pancakes?

Question: What shape are granal thylakoids?

Question: How many granal thylakoids can be in each granum?

Question: How many granal thylakoids are usually in each granum?

Question: What are frets?


Context: Embedded in the thylakoid membranes are important protein complexes which carry out the light reactions of photosynthesis. Photosystem II and photosystem I contain light-harvesting complexes with chlorophyll and carotenoids that absorb light energy and use it to energize electrons. Molecules in the thylakoid membrane use the energized electrons to pump hydrogen ions into the thylakoid space, decreasing the pH and turning it acidic. ATP synthase is a large protein complex that harnesses the concentration gradient of the hydrogen ions in the thylakoid space to generate ATP energy as the hydrogen ions flow back out into the stroma—much like a dam turbine.

Question: What does chlorophyll absorb?

Question: What do carotenoids absorb?

Question: What does chlorophyll use light energy to do?

Question: What does the thylakoid membrane use the energized electrons for?

Question: What is ATP synthase similar to?


Context: There are two types of thylakoids—granal thylakoids, which are arranged in grana, and stromal thylakoids, which are in contact with the stroma. Granal thylakoids are pancake-shaped circular disks about 300–600 nanometers in diameter. Stromal thylakoids are helicoid sheets that spiral around grana. The flat tops and bottoms of granal thylakoids contain only the relatively flat photosystem II protein complex. This allows them to stack tightly, forming grana with many layers of tightly appressed membrane, called granal membrane, increasing stability and surface area for light capture.

Question:
How many types of thylakoids are there?
What distinguishes granal thylakoids?
What distinguishes stromal thylakoids?
What shape are granal thylakoids?
How large are granal thylakoids?


Context: In addition to chlorophylls, another group of yellow–orange pigments called carotenoids are also found in the photosystems. There are about thirty photosynthetic carotenoids. They help transfer and dissipate excess energy, and their bright colors sometimes override the chlorophyll green, like during the fall, when the leaves of some land plants change color. β-carotene is a bright red-orange carotenoid found in nearly all chloroplasts, like chlorophyll a. Xanthophylls, especially the orange-red zeaxanthin, are also common. Many other forms of carotenoids exist that are only found in certain groups of chloroplasts.

Question: How many photosynthetic carotenoids are there?

Question: What do photosynthetic carotenoids do?

Question: Why do carotenoids make leaves change color in the fall?

Question: What is beta carotene?

Question: What is the most common Xanthophyll?


Context: Phycobilins are a third group of pigments found in cyanobacteria, and glaucophyte, red algal, and cryptophyte chloroplasts. Phycobilins come in all colors, though phycoerytherin is one of the pigments that makes many red algae red. Phycobilins often organize into relatively large protein complexes about 40 nanometers across called phycobilisomes. Like photosystem I and ATP synthase, phycobilisomes jut into the stroma, preventing thylakoid stacking in red algal chloroplasts. Cryptophyte chloroplasts and some cyanobacteria don't have their phycobilin pigments organized into phycobilisomes, and keep them in their thylakoid space instead.

Question:
What are Phycobilins?
What color is phycoerytherin?
What does phycoerytherin appear in?
What are phycobilisomes?
How big are phycobilisomes?


Context: To fix carbon dioxide into sugar molecules in the process of photosynthesis, chloroplasts use an enzyme called rubisco. Rubisco has a problem—it has trouble distinguishing between carbon dioxide and oxygen, so at high oxygen concentrations, rubisco starts accidentally adding oxygen to sugar precursors. This has the end result of ATP energy being wasted and CO2 being released, all with no sugar being produced. This is a big problem, since O2 is produced by the initial light reactions of photosynthesis, causing issues down the line in the Calvin cycle which uses rubisco.

Question: What do chloroplasts use to fix carbon dioxide into sugar?

Question: What is rubisco's flaw?

Question: What effect does rubisco's flaw have?

Question: What process down the line does rubisco's flaw interfere with?

Question: What is wasted by rubisco's flaw?


Context: As a result, chloroplasts in C4 mesophyll cells and bundle sheath cells are specialized for each stage of photosynthesis. In mesophyll cells, chloroplasts are specialized for the light reactions, so they lack rubisco, and have normal grana and thylakoids, which they use to make ATP and NADPH, as well as oxygen. They store CO2 in a four-carbon compound, which is why the process is called C4 photosynthesis. The four-carbon compound is then transported to the bundle sheath chloroplasts, where it drops off CO2 and returns to the mesophyll. Bundle sheath chloroplasts do not carry out the light reactions, preventing oxygen from building up in them and disrupting rubisco activity. Because of this, they lack thylakoids organized into grana stacks—though bundle sheath chloroplasts still have free-floating thylakoids in the stroma where they still carry out cyclic electron flow, a light-driven method of synthesizing ATP to power the Calvin cycle without generating oxygen. They lack photosystem II, and only have photosystem I—the only protein complex needed for cyclic electron flow. Because the job of bundle sheath chloroplasts is to carry out the Calvin cycle and make sugar, they often contain large starch grains.

Question: What are chloroplasts in mesophyll cells specialized for?

Question: What do chloroplasts in mesophyll cells lack?

Question: What do chloroplasts in mesophyll cells specialized use to make ATP?

Question: What do chloroplasts in mesophyll cells store carbon dioxide in?

Question: What do bundle sheath chloroplasts specialize in?


Context: Not all cells in a multicellular plant contain chloroplasts. All green parts of a plant contain chloroplasts—the chloroplasts, or more specifically, the chlorophyll in them are what make the photosynthetic parts of a plant green. The plant cells which contain chloroplasts are usually parenchyma cells, though chloroplasts can also be found in collenchyma tissue. A plant cell which contains chloroplasts is known as a chlorenchyma cell. A typical chlorenchyma cell of a land plant contains about 10 to 100 chloroplasts.

Question: What parts of plants have chloroplasts?

Question: What makes plants green?

Question: What plant cells have chloroplasts in them?

Question: Where can chloroplasts sometimes be found?

Question: What is a chlorenchyma cell?


Context: In some plants such as cacti, chloroplasts are found in the stems, though in most plants, chloroplasts are concentrated in the leaves. One square millimeter of leaf tissue can contain half a million chloroplasts. Within a leaf, chloroplasts are mainly found in the mesophyll layers of a leaf, and the guard cells of stomata. Palisade mesophyll cells can contain 30–70 chloroplasts per cell, while stomatal guard cells contain only around 8–15 per cell, as well as much less chlorophyll. Chloroplasts can also be found in the bundle sheath cells of a leaf, especially in C4 plants, which carry out the Calvin cycle in their bundle sheath cells. They are often absent from the epidermis of a leaf.

Question: Where do cacti have chloroplasts?

Question: Where do most plants have chloroplasts?

Question: How many chloroplasts are in stomatal guard cells?

Question: How many chloroplasts are in a square mm of a leaf?

Question: What layers of a leaf have chloroplasts?


Context: The chloroplasts of plant and algal cells can orient themselves to best suit the available light. In low-light conditions, they will spread out in a sheet—maximizing the surface area to absorb light. Under intense light, they will seek shelter by aligning in vertical columns along the plant cell's cell wall or turning sideways so that light strikes them edge-on. This reduces exposure and protects them from photooxidative damage. This ability to distribute chloroplasts so that they can take shelter behind each other or spread out may be the reason why land plants evolved to have many small chloroplasts instead of a few big ones. Chloroplast movement is considered one of the most closely regulated stimulus-response systems that can be found in plants. Mitochondria have also been observed to follow chloroplasts as they move.

Question: When do chloroplasts spread out flat?

Question: When do chloroplasts arrange in vertical columns or turn sideways?

Question: What does turning sideways protect chloroplasts from?

Question: Why do land plants have more and smaller chloroplasts?

Question: What sometimes follows moving chloroplasts?


Context: Plants have two main immune responses—the hypersensitive response, in which infected cells seal themselves off and undergo programmed cell death, and systemic acquired resistance, where infected cells release signals warning the rest of the plant of a pathogen's presence. Chloroplasts stimulate both responses by purposely damaging their photosynthetic system, producing reactive oxygen species. High levels of reactive oxygen species will cause the hypersensitive response. The reactive oxygen species also directly kill any pathogens within the cell. Lower levels of reactive oxygen species initiate systemic acquired resistance, triggering defense-molecule production in the rest of the plant.

Question: How many major immune responses do plants have?

Question: What is the hypersensitive response of a plant immune system?

Question: What is the systemic acquired resistance response of a plant immune system?

Question: How do chloroplasts trigger the plant's immune system?

Question: What does damaging photosynthesis systems create?


Context: Chloroplasts can serve as cellular sensors. After detecting stress in a cell, which might be due to a pathogen, chloroplasts begin producing molecules like salicylic acid, jasmonic acid, nitric oxide and reactive oxygen species which can serve as defense-signals. As cellular signals, reactive oxygen species are unstable molecules, so they probably don't leave the chloroplast, but instead pass on their signal to an unknown second messenger molecule. All these molecules initiate retrograde signaling—signals from the chloroplast that regulate gene expression in the nucleus.

Question: What molecules act as defense signals?

Question: When do chloroplasts produce defense signals?

Question: What happens to reactive oxygen species signals since they don't leave the chloroplast?

Question: What is retrograde signaling?


Context: One of the main functions of the chloroplast is its role in photosynthesis, the process by which light is transformed into chemical energy, to subsequently produce food in the form of sugars. Water (H2O) and carbon dioxide (CO2) are used in photosynthesis, and sugar and oxygen (O2) is made, using light energy. Photosynthesis is divided into two stages—the light reactions, where water is split to produce oxygen, and the dark reactions, or Calvin cycle, which builds sugar molecules from carbon dioxide. The two phases are linked by the energy carriers adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADP+).

Question: What is the most important role of chloroplasts?

Question: What is the process of changing light into chemical energy?

Question: What is chemical energy used to produce in plants?

Question: What are the molecular inputs for photosynthesis?

Question: What are the molecular outputs for photosynthesis?


Context: Like mitochondria, chloroplasts use the potential energy stored in an H+, or hydrogen ion gradient to generate ATP energy. The two photosystems capture light energy to energize electrons taken from water, and release them down an electron transport chain. The molecules between the photosystems harness the electrons' energy to pump hydrogen ions into the thylakoid space, creating a concentration gradient, with more hydrogen ions (up to a thousand times as many) inside the thylakoid system than in the stroma. The hydrogen ions in the thylakoid space then diffuse back down their concentration gradient, flowing back out into the stroma through ATP synthase. ATP synthase uses the energy from the flowing hydrogen ions to phosphorylate adenosine diphosphate into adenosine triphosphate, or ATP. Because chloroplast ATP synthase projects out into the stroma, the ATP is synthesized there, in position to be used in the dark reactions.

Question: What do chloroplasts do like mitochondria?

Question: Where do chloroplasts pump hydrogen?

Question: How concentrated do the hydrogen ions get in the thylakoid space?

Question: What does ATP synthase change into ATP?

Question: What does ATP mean?


Context: While photosystem II photolyzes water to obtain and energize new electrons, photosystem I simply reenergizes depleted electrons at the end of an electron transport chain. Normally, the reenergized electrons are taken by NADP+, though sometimes they can flow back down more H+-pumping electron transport chains to transport more hydrogen ions into the thylakoid space to generate more ATP. This is termed cyclic photophosphorylation because the electrons are recycled. Cyclic photophosphorylation is common in C4 plants, which need more ATP than NADPH.

Question: What usually takes reenergized electrons?

Question: In what process are electrons recycled?

Question: Where is cyclic photophosphorylation common?

Question: What do C4 plants need?


Context: The Calvin cycle starts by using the enzyme Rubisco to fix CO2 into five-carbon Ribulose bisphosphate (RuBP) molecules. The result is unstable six-carbon molecules that immediately break down into three-carbon molecules called 3-phosphoglyceric acid, or 3-PGA. The ATP and NADPH made in the light reactions is used to convert the 3-PGA into glyceraldehyde-3-phosphate, or G3P sugar molecules. Most of the G3P molecules are recycled back into RuBP using energy from more ATP, but one out of every six produced leaves the cycle—the end product of the dark reactions.

Question: What cycle starts with rubisco?

Question: What is the result of the Calvin cycle?

Question: What do unstable 6-carbon molecules become?

Question: How many G3P molecules leave the cycle?


Context: Alternatively, glucose monomers in the chloroplast can be linked together to make starch, which accumulates into the starch grains found in the chloroplast. Under conditions such as high atmospheric CO2 concentrations, these starch grains may grow very large, distorting the grana and thylakoids. The starch granules displace the thylakoids, but leave them intact. Waterlogged roots can also cause starch buildup in the chloroplasts, possibly due to less sucrose being exported out of the chloroplast (or more accurately, the plant cell). This depletes a plant's free phosphate supply, which indirectly stimulates chloroplast starch synthesis. While linked to low photosynthesis rates, the starch grains themselves may not necessarily interfere significantly with the efficiency of photosynthesis, and might simply be a side effect of another photosynthesis-depressing factor.

Question: What is an alternate way to make starch?

Question: When might starch grains become overly large?

Question: What happens when starch grains become overly large?

Question: What root problem can cause starch buildup?

Question: What might starch grains be a side effect of?


Context: Photorespiration can occur when the oxygen concentration is too high. Rubisco cannot distinguish between oxygen and carbon dioxide very well, so it can accidentally add O2 instead of CO2 to RuBP. This process reduces the efficiency of photosynthesis—it consumes ATP and oxygen, releases CO2, and produces no sugar. It can waste up to half the carbon fixed by the Calvin cycle. Several mechanisms have evolved in different lineages that raise the carbon dioxide concentration relative to oxygen within the chloroplast, increasing the efficiency of photosynthesis. These mechanisms are called carbon dioxide concentrating mechanisms, or CCMs. These include Crassulacean acid metabolism, C4 carbon fixation, and pyrenoids. Chloroplasts in C4 plants are notable as they exhibit a distinct chloroplast dimorphism.

Question: What can rubisco do by mistake?

Question: When does photorespiration happen?

Question: Why is using O2 instead of CO2 less efficient?

Question: How much carbon gets wasted by using O2 instead of CO2?

Question: What is unusual about C4 plants' chloroplasts?


Context: Chloroplasts alone make almost all of a plant cell's amino acids in their stroma except the sulfur-containing ones like cysteine and methionine. Cysteine is made in the chloroplast (the proplastid too) but it is also synthesized in the cytosol and mitochondria, probably because it has trouble crossing membranes to get to where it is needed. The chloroplast is known to make the precursors to methionine but it is unclear whether the organelle carries out the last leg of the pathway or if it happens in the cytosol.

Question: Where do chloroplasts make amino acids?

Question: Which amino acids contain sulfur?

Question: What is the problem with cysteine?

Question: What are we unsure of about how chloroplasts make methionine precursors?


Context: Chloroplasts are a special type of a plant cell organelle called a plastid, though the two terms are sometimes used interchangeably. There are many other types of plastids, which carry out various functions. All chloroplasts in a plant are descended from undifferentiated proplastids found in the zygote, or fertilized egg. Proplastids are commonly found in an adult plant's apical meristems. Chloroplasts do not normally develop from proplastids in root tip meristems—instead, the formation of starch-storing amyloplasts is more common.

Question: What is sometimes used interchangeably with 'plastids'?

Question: What do a plant's chloroplasts descend from?

Question: Where are Proplastids usually found?

Question: What is more often seen in root tip maristems?


Context: If angiosperm shoots are not exposed to the required light for chloroplast formation, proplastids may develop into an etioplast stage before becoming chloroplasts. An etioplast is a plastid that lacks chlorophyll, and has inner membrane invaginations that form a lattice of tubes in their stroma, called a prolamellar body. While etioplasts lack chlorophyll, they have a yellow chlorophyll precursor stocked. Within a few minutes of light exposure, the prolamellar body begins to reorganize into stacks of thylakoids, and chlorophyll starts to be produced. This process, where the etioplast becomes a chloroplast, takes several hours. Gymnosperms do not require light to form chloroplasts.

Question: What happens if angiosperm shoots don't get enough light?

Question: What is an etioplast?

Question: What do etioplasts' internal membranes have?

Question: What do etioplasts have instead of chlorophyll?

Question: What plants don't need light to make chloroplasts?


Context: Plastid differentiation is not permanent, in fact many interconversions are possible. Chloroplasts may be converted to chromoplasts, which are pigment-filled plastids responsible for the bright colors seen in flowers and ripe fruit. Starch storing amyloplasts can also be converted to chromoplasts, and it is possible for proplastids to develop straight into chromoplasts. Chromoplasts and amyloplasts can also become chloroplasts, like what happens when a carrot or a potato is illuminated. If a plant is injured, or something else causes a plant cell to revert to a meristematic state, chloroplasts and other plastids can turn back into proplastids. Chloroplast, amyloplast, chromoplast, proplast, etc., are not absolute states—intermediate forms are common.

Question: What can chloroplasts change into?

Question: What are chromoplasts?

Question: What can amyloplasts become?

Question: What can proplastids become?

Question: When a plant is injured, what can become proplastids?


Context: The division process starts when the proteins FtsZ1 and FtsZ2 assemble into filaments, and with the help of a protein ARC6, form a structure called a Z-ring within the chloroplast's stroma. The Min system manages the placement of the Z-ring, ensuring that the chloroplast is cleaved more or less evenly. The protein MinD prevents FtsZ from linking up and forming filaments. Another protein ARC3 may also be involved, but it is not very well understood. These proteins are active at the poles of the chloroplast, preventing Z-ring formation there, but near the center of the chloroplast, MinE inhibits them, allowing the Z-ring to form.

Question: What do FtsZ1 and FtsZ2 combine into?

Question: What are FtsZ1 and FtsZ2?

Question: What do FtsZ1 and FtsZ2 plus ARC6 form?

Question: Where is the Z-ring?

Question: What gets the Z-ring in the right place?


Context:
Next, the two plastid-dividing rings, or PD rings form. The inner plastid-dividing ring is located in the inner side of the chloroplast's inner membrane, and is formed first. The outer plastid-dividing ring is found wrapped around the outer chloroplast membrane. It consists of filaments about 5 nanometers across, arranged in rows 6.4 nanometers apart, and shrinks to squeeze the chloroplast. This is when chloroplast constriction begins.
In a few species like Cyanidioschyzon merolæ, chloroplasts have a third plastid-dividing ring located in the chloroplast's intermembrane space.

Question: What are PD rings?

Question: How many PD rings are there?

Question: How large are the outer PD ring's filaments?

Question: How far apart are the outer PD ring's filaments?

Question: What is different about Cyanidioschyzon merolæ?


Context: Light has been shown to be a requirement for chloroplast division. Chloroplasts can grow and progress through some of the constriction stages under poor quality green light, but are slow to complete division—they require exposure to bright white light to complete division. Spinach leaves grown under green light have been observed to contain many large dumbbell-shaped chloroplasts. Exposure to white light can stimulate these chloroplasts to divide and reduce the population of dumbbell-shaped chloroplasts.

Question: What is necessary for chloroplasts to replicate?

Question: What kind of light is important for chloroplasts to divide?

Question: What do chloroplasts look like in spinach grown in green light?

Question: What kind of light is inadequate for chloroplasts to divide?


Context: Recently, chloroplasts have caught attention by developers of genetically modified crops. Since, in most flowering plants, chloroplasts are not inherited from the male parent, transgenes in these plastids cannot be disseminated by pollen. This makes plastid transformation a valuable tool for the creation and cultivation of genetically modified plants that are biologically contained, thus posing significantly lower environmental risks. This biological containment strategy is therefore suitable for establishing the coexistence of conventional and organic agriculture. While the reliability of this mechanism has not yet been studied for all relevant crop species, recent results in tobacco plants are promising, showing a failed containment rate of transplastomic plants at 3 in 1,000,000.

Question: Why are chloroplasts of interest in GMO crops?

Question: What is reduced by using plastid transformation for gene modification?

Question: What was the containment failure rate in a tobacco plant study using plastid transformation?

Question: What are plants with plastid gene transformations called?


Context: A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number. For example, 5 is prime because 1 and 5 are its only positive integer factors, whereas 6 is composite because it has the divisors 2 and 3 in addition to 1 and 6. The fundamental theorem of arithmetic establishes the central role of primes in number theory: any integer greater than 1 can be expressed as a product of primes that is unique up to ordering. The uniqueness in this theorem requires excluding 1 as a prime because one can include arbitrarily many instances of 1 in any factorization, e.g., 3, 1 · 3, 1 · 1 · 3, etc. are all valid factorizations of 3.

Question: What is the only divisor besides 1 that a prime number can have?

Question: What are numbers greater than 1 that can be divided by 3 or more numbers called?

Question: What theorem defines the main role of primes in number theory?

Question: Any number larger than 1 can be represented as a product of what?

Question: Why must one be excluded in order to preserve the uniqueness of the fundamental theorem?


Context: The property of being prime (or not) is called primality. A simple but slow method of verifying the primality of a given number n is known as trial division. It consists of testing whether n is a multiple of any integer between 2 and . Algorithms much more efficient than trial division have been devised to test the primality of large numbers. These include the Miller–Rabin primality test, which is fast but has a small probability of error, and the AKS primality test, which always produces the correct answer in polynomial time but is too slow to be practical. Particularly fast methods are available for numbers of special forms, such as Mersenne numbers. As of January 2016[update], the largest known prime number has 22,338,618 decimal digits.

Question: What is the name of the property that designates a number as being prime or not?

Question: What is the name of the process which confirms the primality of a number n?

Question: What is the name of one algorithm useful for conveniently testing the primality of large numbers?

Question: What is the name of another algorithm useful for conveniently testing the primality of large numbers?

Question: As of January 2016 how many digits does the largest known prime consist of?


Context: There are infinitely many primes, as demonstrated by Euclid around 300 BC. There is no known simple formula that separates prime numbers from composite numbers. However, the distribution of primes, that is to say, the statistical behaviour of primes in the large, can be modelled. The first result in that direction is the prime number theorem, proven at the end of the 19th century, which says that the probability that a given, randomly chosen number n is prime is inversely proportional to its number of digits, or to the logarithm of n.

Question: How many prime numbers exist?

Question: Who established the amount of prime numbers in existence?

Question: What type of behavior in primes is it possible to determine?

Question: What theorem states that the probability that a number n is prime is inversely proportional to its logarithm?

Question: When was the prime number theorem proven?


Context: Many questions regarding prime numbers remain open, such as Goldbach's conjecture (that every even integer greater than 2 can be expressed as the sum of two primes), and the twin prime conjecture (that there are infinitely many pairs of primes whose difference is 2). Such questions spurred the development of various branches of number theory, focusing on analytic or algebraic aspects of numbers. Primes are used in several routines in information technology, such as public-key cryptography, which makes use of properties such as the difficulty of factoring large numbers into their prime factors. Prime numbers give rise to various generalizations in other mathematical domains, mainly algebra, such as prime elements and prime ideals.

Question: What is the name of the supposition that any number larger than 2 can be represented as the sum of two primes?

Question: What is the name of the supposition that there are infinite pairs of primes whose difference is 2?

Question: Besides the analytic property of numbers, what other property of numbers does number theory focus on?

Question: What is the application of prime numbers used in information technology which utilizes the fact that factoring very large prime numbers is very challenging?

Question: What is the name of one algebraic generalization prime numbers have inspired?


Context: Hence, 6 is not prime. The image at the right illustrates that 12 is not prime: 12 = 3 · 4. No even number greater than 2 is prime because by definition, any such number n has at least three distinct divisors, namely 1, 2, and n. This implies that n is not prime. Accordingly, the term odd prime refers to any prime number greater than 2. Similarly, when written in the usual decimal system, all prime numbers larger than 5 end in 1, 3, 7, or 9, since even numbers are multiples of 2 and numbers ending in 0 or 5 are multiples of 5.

Question: Any even number larger than what cannot be considered prime?

Question: What are the specific divisors of all even numbers larger than 2?

Question: What name is given to any prime number larger than 2?

Question: Besides 1,3 and 7, what other number must all primes greater than 5 end with?

Question: What type of numbers are always multiples of 2?


Context: Most early Greeks did not even consider 1 to be a number, so they could not consider it to be a prime. By the Middle Ages and Renaissance many mathematicians included 1 as the first prime number. In the mid-18th century Christian Goldbach listed 1 as the first prime in his famous correspondence with Leonhard Euler -- who did not agree. In the 19th century many mathematicians still considered the number 1 to be a prime. For example, Derrick Norman Lehmer's list of primes up to 10,006,721, reprinted as late as 1956, started with 1 as its first prime. Henri Lebesgue is said to be the last professional mathematician to call 1 prime. By the early 20th century, mathematicians began to accept that 1 is not a prime number, but rather forms its own special category as a "unit".

Question: What number did early Greeks not regard as a true number?

Question: Who included 1 as the first prime number in the mid 18th century?

Question: In the mid 18th century, who did not concur that 1 should be the first prime number?

Question: How many primes were included in Derrick Norman Lehmer's list of prime numbers?

Question: What type of number do modern mathematicians consider 1 to be?


Context: A large body of mathematical work would still be valid when calling 1 a prime, but Euclid's fundamental theorem of arithmetic (mentioned above) would not hold as stated. For example, the number 15 can be factored as 3 · 5 and 1 · 3 · 5; if 1 were admitted as a prime, these two presentations would be considered different factorizations of 15 into prime numbers, so the statement of that theorem would have to be modified. Similarly, the sieve of Eratosthenes would not work correctly if 1 were considered a prime: a modified version of the sieve that considers 1 as prime would eliminate all multiples of 1 (that is, all other numbers) and produce as output only the single number 1. Furthermore, the prime numbers have several properties that the number 1 lacks, such as the relationship of the number to its corresponding value of Euler's totient function or the sum of divisors function.

Question: Which theorem would be invalid if the number 1 were considered prime?

Question: The sieve of Eratosthenes would not be valid if what were true?

Question: What is another function that primes have that the number 1 does not?

Question: What is one function that prime numbers have that 1 does not?

Question: If 1 were to be considered as prime what would the sieve of Eratosthenes yield for all other numbers?


Context: There are hints in the surviving records of the ancient Egyptians that they had some knowledge of prime numbers: the Egyptian fraction expansions in the Rhind papyrus, for instance, have quite different forms for primes and for composites. However, the earliest surviving records of the explicit study of prime numbers come from the Ancient Greeks. Euclid's Elements (circa 300 BC) contain important theorems about primes, including the infinitude of primes and the fundamental theorem of arithmetic. Euclid also showed how to construct a perfect number from a Mersenne prime. The Sieve of Eratosthenes, attributed to Eratosthenes, is a simple method to compute primes, although the large primes found today with computers are not generated this way.

Question: What is the name of the Egyptian papyrus that suggests that they may have had knowledge of prime numbers?

Question: What civilization was the first known to clearly study prime numbers?

Question: What work from around 300 BC has significant theorems about prime numbers?

Question: Who demonstrated how to create a perfect number from a Mersenne prime?

Question: What does the Sieve of Eratosthenes do?


Context: After the Greeks, little happened with the study of prime numbers until the 17th century. In 1640 Pierre de Fermat stated (without proof) Fermat's little theorem (later proved by Leibniz and Euler). Fermat also conjectured that all numbers of the form 22n + 1 are prime (they are called Fermat numbers) and he verified this up to n = 4 (or 216 + 1). However, the very next Fermat number 232 + 1 is composite (one of its prime factors is 641), as Euler discovered later, and in fact no further Fermat numbers are known to be prime. The French monk Marin Mersenne looked at primes of the form 2p − 1, with p a prime. They are called Mersenne primes in his honor.

Question: In what year did Pierre de Fermat declare Fermat's little theorem?

Question: Besides Leibniz, what other mathematician proved the validity of Fermat's little theorem?

Question: Of what form do Fermat numbers take?

Question: Of what form do Mersenne primes take?

Question: To what extent did Fermat confirm the validity of Fermat numbers?


Context: The most basic method of checking the primality of a given integer n is called trial division. This routine consists of dividing n by each integer m that is greater than 1 and less than or equal to the square root of n. If the result of any of these divisions is an integer, then n is not a prime, otherwise it is a prime. Indeed, if  is composite (with a and b ≠ 1) then one of the factors a or b is necessarily at most . For example, for , the trial divisions are by m = 2, 3, 4, 5, and 6. None of these numbers divides 37, so 37 is prime. This routine can be implemented more efficiently if a complete list of primes up to  is known—then trial divisions need to be checked only for those m that are prime. For example, to check the primality of 37, only three divisions are necessary (m = 2, 3, and 5), given that 4 and 6 are composite.

Question: What is the most elemental way to test the primality of any integer n?

Question: What makes the method of trial division more efficient?

Question: Trial division involves dividing n by every integer m greater than what?

Question: How many divisions are required to verify the primality of the number 37?

Question: What must the integer m be less than or equal to when performing trial division?


Context: Modern primality tests for general numbers n can be divided into two main classes, probabilistic (or "Monte Carlo") and deterministic algorithms. Deterministic algorithms provide a way to tell for sure whether a given number is prime or not. For example, trial division is a deterministic algorithm because, if performed correctly, it will always identify a prime number as prime and a composite number as composite. Probabilistic algorithms are normally faster, but do not completely prove that a number is prime. These tests rely on testing a given number in a partly random way. For example, a given test might pass all the time if applied to a prime number, but pass only with probability p if applied to a composite number. If we repeat the test n times and pass every time, then the probability that our number is composite is 1/(1-p)n, which decreases exponentially with the number of tests, so we can be as sure as we like (though never perfectly sure) that the number is prime. On the other hand, if the test ever fails, then we know that the number is composite.

Question: How many modern types of primality tests for general numbers n are there?

Question: What is the name of one type of modern primality test?

Question: What is the name of another type of modern primality test?

Question: What type of algorithm is trial division?

Question: When using a probabilistic algorithm, how is the probability that the number is composite expressed mathematically?


Context: A particularly simple example of a probabilistic test is the Fermat primality test, which relies on the fact (Fermat's little theorem) that np≡n (mod p) for any n if p is a prime number. If we have a number b that we want to test for primality, then we work out nb (mod b) for a random value of n as our test. A flaw with this test is that there are some composite numbers (the Carmichael numbers) that satisfy the Fermat identity even though they are not prime, so the test has no way of distinguishing between prime numbers and Carmichael numbers. Carmichael numbers are substantially rarer than prime numbers, though, so this test can be useful for practical purposes. More powerful extensions of the Fermat primality test, such as the Baillie-PSW, Miller-Rabin, and Solovay-Strassen tests, are guaranteed to fail at least some of the time when applied to a composite number.

Question: What is one straightforward case of a probabilistic test?

Question: What does the Fermat primality test depend upon?

Question: What type of numbers demonstrate a flaw with the Fermat primality test?

Question: What is the name of one impressive continuation of the Fermat primality test?

Question: What is the name of another compelling continuation of the Fermat primality test?


Context: are prime. Prime numbers of this form are known as factorial primes. Other primes where either p + 1 or p − 1 is of a particular shape include the Sophie Germain primes (primes of the form 2p + 1 with p prime), primorial primes, Fermat primes and Mersenne primes, that is, prime numbers that are of the form 2p − 1, where p is an arbitrary prime. The Lucas–Lehmer test is particularly fast for numbers of this form. This is why the largest known prime has almost always been a Mersenne prime since the dawn of electronic computers.

Question: Of what form are Sophie Germain primes?

Question: Of what form are Mersenne primes?

Question: What test is especially useful for numbers of the form 2p - 1?

Question: What is the name of one type of prime where p+1 or p-1 takes a certain shape?

Question: What is the name of another type of prime here p+1 or p-1 takes a certain shape?


Context: The following table gives the largest known primes of the mentioned types. Some of these primes have been found using distributed computing. In 2009, the Great Internet Mersenne Prime Search project was awarded a US$100,000 prize for first discovering a prime with at least 10 million digits. The Electronic Frontier Foundation also offers $150,000 and $250,000 for primes with at least 100 million digits and 1 billion digits, respectively. Some of the largest primes not known to have any particular form (that is, no simple formula such as that of Mersenne primes) have been found by taking a piece of semi-random binary data, converting it to a number n, multiplying it by 256k for some positive integer k, and searching for possible primes within the interval [256kn + 1, 256k(n + 1) − 1].[citation needed]

Question: What is the name of one type of computing method that is used to find prime numbers?

Question: In what year was the Great Internet Mersenne Prime Search project conducted?

Question: the Great Internet Mersenne Prime Search, what was the prize for finding a prime with at least 10 million digits?

Question: What organization offers monetary awards for identifying primes with at least 100 million digits?

Question: In what interval are some of the greatest primes without a distinct form discovered in?


Context: are prime for any natural number n. Here  represents the floor function, i.e., largest integer not greater than the number in question. The latter formula can be shown using Bertrand's postulate (proven first by Chebyshev), which states that there always exists at least one prime number p with n < p < 2n − 2, for any natural number n > 3. However, computing A or μ requires the knowledge of infinitely many primes to begin with. Another formula is based on Wilson's theorem and generates the number 2 many times and all other primes exactly once.

Question: What is name of the function used for the largest integer not greater than the number in question?

Question: Who first proved Bertrand's postulate?

Question: For what size natural number does Bertrand's postulate hold?

Question: How is the prime number p in Bertrand's postulate expressed mathematically?

Question: On what theorem is the formula that frequently generates the number 2 and all other primes precisely once based on?


Context: can have infinitely many primes only when a and q are coprime, i.e., their greatest common divisor is one. If this necessary condition is satisfied, Dirichlet's theorem on arithmetic progressions asserts that the progression contains infinitely many primes. The picture below illustrates this with q = 9: the numbers are "wrapped around" as soon as a multiple of 9 is passed. Primes are highlighted in red. The rows (=progressions) starting with a = 3, 6, or 9 contain at most one prime number. In all other rows (a = 1, 2, 4, 5, 7, and 8) there are infinitely many prime numbers. What is more, the primes are distributed equally among those rows in the long run—the density of all primes congruent a modulo 9 is 1/6.

Question: What is another way to state the condition that infinitely many primes can exist only if a and q are coprime?

Question: If a and q are coprime, which theorem holds that an arithmetic progression has an infinite number of primes?

Question: What is the density of all primes compatible with a modulo 9?

Question: If q=9 and a=3,6 or 9, how many primes would be in the progression?

Question: If q=9 and a=1,2,4,5,7, or 8, how many primes would be in a progression?


Context: The zeta function is closely related to prime numbers. For example, the aforementioned fact that there are infinitely many primes can also be seen using the zeta function: if there were only finitely many primes then ζ(1) would have a finite value. However, the harmonic series 1 + 1/2 + 1/3 + 1/4 + ... diverges (i.e., exceeds any given number), so there must be infinitely many primes. Another example of the richness of the zeta function and a glimpse of modern algebraic number theory is the following identity (Basel problem), due to Euler,

Question: What function is related to prime numbers?

Question: What type of value would the zeta function have if there were finite primes?

Question: What property of the harmonic series 1 + 1/2 + 1/3 + 1/4 + ... shows that there is an infinite number of primes?

Question: What does it mean when a harmonic series diverges?

Question: Of what mathematical nature is the Basel problem?


Context: The unproven Riemann hypothesis, dating from 1859, states that except for s = −2, −4, ..., all zeroes of the ζ-function have real part equal to 1/2. The connection to prime numbers is that it essentially says that the primes are as regularly distributed as possible.[clarification needed] From a physical viewpoint, it roughly states that the irregularity in the distribution of primes only comes from random noise. From a mathematical viewpoint, it roughly states that the asymptotic distribution of primes (about x/log x of numbers less than x are primes, the prime number theorem) also holds for much shorter intervals of length about the square root of x (for intervals near x). This hypothesis is generally believed to be correct. In particular, the simplest assumption is that primes should have no significant irregularities without good reason.

Question: When was the Riemann hypothesis proposed?

Question: According to the Riemann hypothesis, all zeroes of the ζ-function have real part equal to 1/2 except for what values of s?

Question: What does the Riemann hypothesis state the source of irregularity in the distribution of points comes from?

Question: What type of prime distribution does the Riemann hypothesis propose is also true for short intervals near X?

Question: What type of prime distribution is characterized about x/log x of numbers less than x?


Context: In addition to the Riemann hypothesis, many more conjectures revolving about primes have been posed. Often having an elementary formulation, many of these conjectures have withstood a proof for decades: all four of Landau's problems from 1912 are still unsolved. One of them is Goldbach's conjecture, which asserts that every even integer n greater than 2 can be written as a sum of two primes. As of February 2011[update], this conjecture has been verified for all numbers up to n = 2 · 1017. Weaker statements than this have been proven, for example Vinogradov's theorem says that every sufficiently large odd integer can be written as a sum of three primes. Chen's theorem says that every sufficiently large even number can be expressed as the sum of a prime and a semiprime, the product of two primes. Also, any even integer can be written as the sum of six primes. The branch of number theory studying such questions is called additive number theory.

Question: Which conjecture holds that every even integer n greater than 2 can be expressed as a sum of two primes?

Question: When did Landau propose his four conjectural problems?

Question: As of February 2011, how many numbers has Goldbach's conjecture been proven to?

Question: Which theorem states that all large odd integers can be expressed as a sum of three primes?

Question: Which theorem states that every large even integer can be written as a prime summed with a semiprime?


Context: A third type of conjectures concerns aspects of the distribution of primes. It is conjectured that there are infinitely many twin primes, pairs of primes with difference 2 (twin prime conjecture). Polignac's conjecture is a strengthening of that conjecture, it states that for every positive integer n, there are infinitely many pairs of consecutive primes that differ by 2n. It is conjectured there are infinitely many primes of the form n2 + 1. These conjectures are special cases of the broad Schinzel's hypothesis H. Brocard's conjecture says that there are always at least four primes between the squares of consecutive primes greater than 2. Legendre's conjecture states that there is a prime number between n2 and (n + 1)2 for every positive integer n. It is implied by the stronger Cramér's conjecture.

Question: What conjecture holds that there is an infinite amount of twin primes?

Question: What is a twin prime?

Question: Which conjecture holds that for any positive integer n, there is an infinite amount of pairs of consecutive primes differing by 2n?

Question: Of what form is the infinite amount of primes that comprise the special cases of Schinzel's hypothesis?

Question: What conjecture holds that there are always a minimum of 4 primes  between the squares of consecutive primes greater than 2?


Context: For a long time, number theory in general, and the study of prime numbers in particular, was seen as the canonical example of pure mathematics, with no applications outside of the self-interest of studying the topic with the exception of use of prime numbered gear teeth to distribute wear evenly. In particular, number theorists such as British mathematician G. H. Hardy prided themselves on doing work that had absolutely no military significance. However, this vision was shattered in the 1970s, when it was publicly announced that prime numbers could be used as the basis for the creation of public key cryptography algorithms. Prime numbers are also used for hash tables and pseudorandom number generators.

Question: Besides the study of prime numbers, what general theory was considered the official example of pure mathematics?

Question: What British mathematician took pride in doing work that he felt had no military benefit?

Question: When was it discovered that prime numbers could applied to the creation of public key cryptography algorithms?

Question: Besides public key cryptography, what is another application for prime numbers?

Question: What type of number generators make use of prime numbers?


Context: Giuga's conjecture says that this equation is also a sufficient condition for p to be prime. Another consequence of Fermat's little theorem is the following: if p is a prime number other than 2 and 5, 1/p is always a recurring decimal, whose period is p − 1 or a divisor of p − 1. The fraction 1/p expressed likewise in base q (rather than base 10) has similar effect, provided that p is not a prime factor of q. Wilson's theorem says that an integer p > 1 is prime if and only if the factorial (p − 1)! + 1 is divisible by p. Moreover, an integer n > 4 is composite if and only if (n − 1)! is divisible by n.

Question: Assuming p is a prime other than 2 or 5, then, according to Fermat's theorem, what type of decimal will 1/p always be?

Question: According to Fermat's theorem, what period does 1/p always have assuming p is prime that is not 2 or 5?

Question: According to Wilson's theorem, what factorial must be divisible by p if some integer p > 1 is to be considered prime?

Question: According to Wilson's theorem, what factorial must be divisible by n if some integer n > 4 is to be considered composite?

Question: What condition what must be satisfied in order for 1/p to be expressed in base q instead of base 10 and still have a period of p - 1?


Context: Several public-key cryptography algorithms, such as RSA and the Diffie–Hellman key exchange, are based on large prime numbers (for example, 512-bit primes are frequently used for RSA and 1024-bit primes are typical for Diffie–Hellman.). RSA relies on the assumption that it is much easier (i.e., more efficient) to perform the multiplication of two (large) numbers x and y than to calculate x and y (assumed coprime) if only the product xy is known. The Diffie–Hellman key exchange relies on the fact that there are efficient algorithms for modular exponentiation, while the reverse operation the discrete logarithm is thought to be a hard problem.

Question: What is one type of public key cryptography algorithm?

Question: What is another type of public key cryptography algorithm?

Question: How many bits are often in the primes used for RSA public key cryptography algorithms?

Question: On what type of exponentiation does the Diffie–Hellman key exchange depend on?

Question: How many bits are typically used in the primes for the Diffie–Hellman key exchange?


Context: The evolutionary strategy used by cicadas of the genus Magicicada make use of prime numbers. These insects spend most of their lives as grubs underground. They only pupate and then emerge from their burrows after 7, 13 or 17 years, at which point they fly about, breed, and then die after a few weeks at most. The logic for this is believed to be that the prime number intervals between emergences make it very difficult for predators to evolve that could specialize as predators on Magicicadas. If Magicicadas appeared at a non-prime number intervals, say every 12 years, then predators appearing every 2, 3, 4, 6, or 12 years would be sure to meet them. Over a 200-year period, average predator populations during hypothetical outbreaks of 14- and 15-year cicadas would be up to 2% higher than during outbreaks of 13- and 17-year cicadas. Though small, this advantage appears to have been enough to drive natural selection in favour of a prime-numbered life-cycle for these insects.

Question: What type of insect employs the use of prime numbers in its evolutionary strategy?

Question: Where do cicadas spend the majority of their lives?

Question: Other than 7 and 13, what other year interval do cicadas pupate?

Question: What is the logic behind the cicadas prime number evolutionary strategy?

Question: How much larger would cicada predator populations be if cicada outbreaks occurred at 14 and 15 year intervals?


Context: The concept of prime number is so important that it has been generalized in different ways in various branches of mathematics. Generally, "prime" indicates minimality or indecomposability, in an appropriate sense. For example, the prime field is the smallest subfield of a field F containing both 0 and 1. It is either Q or the finite field with p elements, whence the name. Often a second, additional meaning is intended by using the word prime, namely that any object can be, essentially uniquely, decomposed into its prime components. For example, in knot theory, a prime knot is a knot that is indecomposable in the sense that it cannot be written as the knot sum of two nontrivial knots. Any knot can be uniquely expressed as a connected sum of prime knots. Prime models and prime 3-manifolds are other examples of this type.

Question: What does the word prime generally suggest?

Question: For a field F containing 0 and 1, what would be the prime field?

Question: How can any knot be distinctively indicated?

Question: What is an additional meaning intended when the word prime is used?

Question: What does it mean for a knot to be considered indecomposable?


Context: Prime numbers give rise to two more general concepts that apply to elements of any commutative ring R, an algebraic structure where addition, subtraction and multiplication are defined: prime elements and irreducible elements. An element p of R is called prime element if it is neither zero nor a unit (i.e., does not have a multiplicative inverse) and satisfies the following requirement: given x and y in R such that p divides the product xy, then p divides x or y. An element is irreducible if it is not a unit and cannot be written as a product of two ring elements that are not units. In the ring Z of integers, the set of prime elements equals the set of irreducible elements, which is

Question: What is the name of an algebraic structure in which addition, subtraction and multiplication are defined?

Question: What is one general concept that applies to elements of commutative rings?

Question: What is another general concept that applies to elements of commutative rings?

Question: What is one condition that an element p of R must satisfy in order to be considered a prime element?

Question: Under what condition is an element irreducible?


Context: The fundamental theorem of arithmetic continues to hold in unique factorization domains. An example of such a domain is the Gaussian integers Z[i], that is, the set of complex numbers of the form a + bi where i denotes the imaginary unit and a and b are arbitrary integers. Its prime elements are known as Gaussian primes. Not every prime (in Z) is a Gaussian prime: in the bigger ring Z[i], 2 factors into the product of the two Gaussian primes (1 + i) and (1 − i). Rational primes (i.e. prime elements in Z) of the form 4k + 3 are Gaussian primes, whereas rational primes of the form 4k + 1 are not.

Question: What theorem remains valid in unique factorization domains?

Question: What is one example of a unique factorization domain?

Question: What form do complex Gaussian integers have?

Question: What do a and b represent in a Gaussian integer expression?

Question: Of what form are rational primes?


Context: In ring theory, the notion of number is generally replaced with that of ideal. Prime ideals, which generalize prime elements in the sense that the principal ideal generated by a prime element is a prime ideal, are an important tool and object of study in commutative algebra, algebraic number theory and algebraic geometry. The prime ideals of the ring of integers are the ideals (0), (2), (3), (5), (7), (11), … The fundamental theorem of arithmetic generalizes to the Lasker–Noether theorem, which expresses every ideal in a Noetherian commutative ring as an intersection of primary ideals, which are the appropriate generalizations of prime powers.

Question: In what theory is the idea of a number exchanged with that of an ideal?

Question: What type of ideals generalize prime elements?

Question: What type of number theory utilizes and studies prime ideals?

Question: Which theorem can be simplified to the Lasker–Noether theorem?

Question: What type of commutative ring does the Lasker–Noether theorem express every ideal as an intersection of primary ideals in?


Context: Prime ideals are the points of algebro-geometric objects, via the notion of the spectrum of a ring. Arithmetic geometry also benefits from this notion, and many concepts exist in both geometry and number theory. For example, factorization or ramification of prime ideals when lifted to an extension field, a basic problem of algebraic number theory, bears some resemblance with ramification in geometry. Such ramification questions occur even in number-theoretic questions solely concerned with integers. For example, prime ideals in the ring of integers of quadratic number fields can be used in proving quadratic reciprocity, a statement that concerns the solvability of quadratic equations

Question: What are the points of algebro-geometric objects?

Question: What does factorization of prime ideals approximate?

Question: In what type of ring can prime ideals be used for validating quadratic reciprocity?

Question: What does quadratic reciprocity seek to achieve?


Context: In particular, this norm gets smaller when a number is multiplied by p, in sharp contrast to the usual absolute value (also referred to as the infinite prime). While completing Q (roughly, filling the gaps) with respect to the absolute value yields the field of real numbers, completing with respect to the p-adic norm |−|p yields the field of p-adic numbers. These are essentially all possible ways to complete Q, by Ostrowski's theorem. Certain arithmetic questions related to Q or more general global fields may be transferred back and forth to the completed (or local) fields. This local-global principle again underlines the importance of primes to number theory.

Question: What happens to the norm when a number is multiplied by p?

Question: To what may general global fields be transferred to or from?

Question: Completing Q with respect to what will produce the field of real numbers?

Question: What principle highlights the significance of primes in number theory


Context: Prime numbers have influenced many artists and writers. The French composer Olivier Messiaen used prime numbers to create ametrical music through "natural phenomena". In works such as La Nativité du Seigneur (1935) and Quatre études de rythme (1949–50), he simultaneously employs motifs with lengths given by different prime numbers to create unpredictable rhythms: the primes 41, 43, 47 and 53 appear in the third étude, "Neumes rythmiques". According to Messiaen this way of composing was "inspired by the movements of nature, movements of free and unequal durations".

Question: Which French composer wrote ametrical music using prime numbers?

Question: What is one work by Olivier Messiaen?

Question: What is another piece created by Olivier Messiaen?

Question: In which etude of Neumes rythmiques do the primes 41, 43, 47 and 53 appear in?

Question: Messiaen says that composition with prime numbers was inspired by what?


Context: The name Rijn, from here on, is used only for smaller streams farther to the north, which together formed the main river Rhine in Roman times. Though they retained the name, these streams no longer carry water from the Rhine, but are used for draining the surrounding land and polders. From Wijk bij Duurstede, the old north branch of the Rhine is called Kromme Rijn ("Bent Rhine") past Utrecht, first Leidse Rijn ("Rhine of Leiden") and then, Oude Rijn ("Old Rhine"). The latter flows west into a sluice at Katwijk, where its waters can be discharged into the North Sea. This branch once formed the line along which the Limes Germanicus were built. During periods of lower sea levels within the various ice ages, the Rhine took a left turn, creating the Channel River, the course of which now lies below the English Channel.

Question: What is the name for the smaller streams along the region northern Germany?

Question: The smaller streams are used for what?

Question: What is the name of the old north branch of the Rhine?

Question: What is the translation of the old north branch of rhe Rhine?

Question: What part of the Rhine flows west at Katwijk?


Context: The Rhine-Meuse Delta, the most important natural region of the Netherlands begins near Millingen aan de Rijn, close to the Dutch-German border with the division of the Rhine into Waal and Nederrijn. Since the Rhine contributes most of the water, the shorter term Rhine Delta is commonly used. However, this name is also used for the river delta where the Rhine flows into Lake Constance, so it is clearer to call the larger one Rhine-Meuse delta, or even Rhine–Meuse–Scheldt delta, as the Scheldt ends in the same delta.

Question: What is the name of the Delta in the Netherlands?

Question: Where does the Delta in the Netherlands begin?

Question: What is the nickname for the Delta in the Netherlands?


Context: The shape of the Rhine delta is determined by two bifurcations: first, at Millingen aan de Rijn, the Rhine splits into Waal and Pannerdens Kanaal, which changes its name to Nederrijn at Angeren, and second near Arnhem, the IJssel branches off from the Nederrijn. This creates three main flows, two of which change names rather often. The largest and southern main branch begins as Waal and continues as Boven Merwede ("Upper Merwede"), Beneden Merwede ("Lower Merwede"), Noord River ("North River"), Nieuwe Maas ("New Meuse"), Het Scheur ("the Rip") and Nieuwe Waterweg ("New Waterway"). The middle flow begins as Nederrijn, then changes into Lek, then joins the Noord, thereby forming Nieuwe Maas. The northern flow keeps the name IJssel until it flows into Lake IJsselmeer. Three more flows carry significant amounts of water: the Nieuwe Merwede ("New Merwede"), which branches off from the southern branch where it changes from Boven to Beneden Merwede; the Oude Maas ("Old Meuse"), which branches off from the southern branch where it changes from Beneden Merwede into Noord, and Dordtse Kil, which branches off from Oude Maas.

Question: At Millingen aan de Rijn where the Rhine splits, what does it change it's name to?

Question: How many main flows are branched off from the Nederrijn?

Question: What is the largest main branch of the Rhine?

Question: What is the translation of Oude Maas?

Question: What is the English translation of Het Scheur?


Context: Before the St. Elizabeth's flood (1421), the Meuse flowed just south of today's line Merwede-Oude Maas to the North Sea and formed an archipelago-like estuary with Waal and Lek. This system of numerous bays, estuary-like extended rivers, many islands and constant changes of the coastline, is hard to imagine today. From 1421 to 1904, the Meuse and Waal merged further upstream at Gorinchem to form Merwede. For flood protection reasons, the Meuse was separated from the Waal through a lock and diverted into a new outlet called "Bergse Maas", then Amer and then flows into the former bay Hollands Diep.

Question: What flood impacted the Meuse?

Question: What year did the flood that impacted the Meuse take place?

Question: Where did the Meuse flow before the flood?

Question: When did the Meuse and Waal merge?

Question: What did the Merwede-Oude Maas form with Waal and Lek?


Context: The hydrography of the current delta is characterized by the delta's main arms, disconnected arms (Hollandse IJssel, Linge, Vecht, etc.) and smaller rivers and streams. Many rivers have been closed ("dammed") and now serve as drainage channels for the numerous polders. The construction of Delta Works changed the Delta in the second half of the 20th Century fundamentally. Currently Rhine water runs into the sea, or into former marine bays now separated from the sea, in five places, namely at the mouths of the Nieuwe Merwede, Nieuwe Waterway (Nieuwe Maas), Dordtse Kil, Spui and IJssel.

Question: What do closed rivers serve as after they close?

Question: What changed the Rhine's Delta?

Question: What is the term for closing off rivers that are no longer connected?

Question: When was the construction that changed the Rhine's Delta?


Context: The Rhine-Meuse Delta is a tidal delta, shaped not only by the sedimentation of the rivers, but also by tidal currents. This meant that high tide formed a serious risk because strong tidal currents could tear huge areas of land into the sea. Before the construction of the Delta Works, tidal influence was palpable up to Nijmegen, and even today, after the regulatory action of the Delta Works, the tide acts far inland. At the Waal, for example, the most landward tidal influence can be detected between Brakel and Zaltbommel.

Question: What type of Delta is the Rhine-Meuse?

Question: Besides rivers, what shapes the sedimentation of the rivers?

Question: What does a high tide risk near lands?

Question: Between Brakel and what other city can the most landward tidal influence be detected?


Context: In southern Europe, the stage was set in the Triassic Period of the Mesozoic Era, with the opening of the Tethys Ocean, between the Eurasian and African tectonic plates, between about 240 MBP and 220 MBP (million years before present). The present Mediterranean Sea descends from this somewhat larger Tethys sea. At about 180 MBP, in the Jurassic Period, the two plates reversed direction and began to compress the Tethys floor, causing it to be subducted under Eurasia and pushing up the edge of the latter plate in the Alpine Orogeny of the Oligocene and Miocene Periods. Several microplates were caught in the squeeze and rotated or were pushed laterally, generating the individual features of Mediterranean geography: Iberia pushed up the Pyrenees; Italy, the Alps, and Anatolia, moving west, the mountains of Greece and the islands. The compression and orogeny continue today, as shown by the ongoing raising of the mountains a small amount each year and the active volcanoes.

Question: The present Mediterranean Sea descends from what sea?

Question: What period did plates reverse directions to compress the Tethys floor?

Question: Microplates squeezing and rotating created the features of what?

Question: What period opened the Tethys Ocean?

Question: What pushed up the Pyrenees?


Context: From the Eocene onwards, the ongoing Alpine orogeny caused a N–S rift system to develop in this zone. The main elements of this rift are the Upper Rhine Graben, in southwest Germany and eastern France and the Lower Rhine Embayment, in northwest Germany and the southeastern Netherlands. By the time of the Miocene, a river system had developed in the Upper Rhine Graben, that continued northward and is considered the first Rhine river. At that time, it did not yet carry discharge from the Alps; instead, the watersheds of the Rhone and Danube drained the northern flanks of the Alps.

Question: What rift system developed in the Alpine orogeny?

Question: What elements from the rift system in the Alpine orogeny in Southwest Germany?

Question: What time did a river system develop in the Upper Rhine Graben?

Question: The Rhine and what other river drained the northern flanks of the alps?


Context: Through stream capture, the Rhine extended its watershed southward. By the Pliocene period, the Rhine had captured streams down to the Vosges Mountains, including the Mosel, the Main and the Neckar. The northern Alps were then drained by the Rhone. By the early Pleistocene period, the Rhine had captured most of its current Alpine watershed from the Rhône, including the Aar. Since that time, the Rhine has added the watershed above Lake Constance (Vorderrhein, Hinterrhein, Alpenrhein; captured from the Rhône), the upper reaches of the Main, beyond Schweinfurt and the Vosges Mountains, captured from the Meuse, to its watershed.

Question: How did the Rhine extend watershed southward?

Question: What period did the Rhine capture streams?

Question: Where are the streams the Rhine captured?


Context: Around 2.5 million years ago (ending 11,600 years ago) was the geological period of the Ice Ages. Since approximately 600,000 years ago, six major Ice Ages have occurred, in which sea level dropped 120 m (390 ft) and much of the continental margins became exposed. In the Early Pleistocene, the Rhine followed a course to the northwest, through the present North Sea. During the so-called Anglian glaciation (~450,000 yr BP, marine oxygen isotope stage 12), the northern part of the present North Sea was blocked by the ice and a large lake developed, that overflowed through the English Channel. This caused the Rhine's course to be diverted through the English Channel. Since then, during glacial times, the river mouth was located offshore of Brest, France and rivers, like the Thames and the Seine, became tributaries to the Rhine. During interglacials, when sea level rose to approximately the present level, the Rhine built deltas, in what is now the Netherlands.

Question: What period was 2.5 million years ago?

Question: How many major ice ages have occurred?

Question: How far did the sea level drop in the ice ages?

Question: In early Pleistocene, what direction did the Rhine flow?

Question: During glacial times, where was the mouth of the Rhine located?


Context: The last glacial ran from ~74,000 (BP = Before Present), until the end of the Pleistocene (~11,600 BP). In northwest Europe, it saw two very cold phases, peaking around 70,000 BP and around 29,000–24,000 BP. The last phase slightly predates the global last ice age maximum (Last Glacial Maximum). During this time, the lower Rhine flowed roughly west through the Netherlands and extended to the southwest, through the English Channel and finally, to the Atlantic Ocean. The English Channel, the Irish Channel and most of the North Sea were dry land, mainly because sea level was approximately 120 m (390 ft) lower than today.

Question: When did the last glacial start?

Question: When did the last glacial end?

Question: Which direction did the Rhine flow during the last cold phase?

Question: How much lower was the North Sea in the last cold phase than it is today?

Question: Besides the North Sea and the Irish Channel, what else was lowered in the last cold phase?


Context: Most of the Rhine's current course was not under the ice during the last Ice Age; although, its source must still have been a glacier. A tundra, with Ice Age flora and fauna, stretched across middle Europe, from Asia to the Atlantic Ocean. Such was the case during the Last Glacial Maximum, ca. 22,000–14,000 yr BP, when ice-sheets covered Scandinavia, the Baltics, Scotland and the Alps, but left the space between as open tundra. The loess or wind-blown dust over that tundra, settled in and around the Rhine Valley, contributing to its current agricultural usefulness.

Question: What was the source of the Rhine in the last Ice Age?

Question: What stretched across middle Europe in the last ice age?

Question: When was the Last Glacial Maximum?

Question: What covered Scandinavia, the Baltics, Scotland, and the Alps in the last Ice Age?

Question: What is the term for wind-blown dust in a tundra?


Context: As northwest Europe slowly began to warm up from 22,000 years ago onward, frozen subsoil and expanded alpine glaciers began to thaw and fall-winter snow covers melted in spring. Much of the discharge was routed to the Rhine and its downstream extension. Rapid warming and changes of vegetation, to open forest, began about 13,000 BP. By 9000 BP, Europe was fully forested. With globally shrinking ice-cover, ocean water levels rose and the English Channel and North Sea re-inundated. Meltwater, adding to the ocean and land subsidence, drowned the former coasts of Europe transgressionally.

Question: When did Europe slowly begin to warm up from the last Ice Age?

Question: What did frozen subsoil and expanded alpine glaciers begin to do?

Question: Where did the discharge from glaciers go in Europe in the last Ice Age?

Question: When did rapid warming begin and help vegetation?

Question: When was Europe fully forested and recovered from the last Ice Age?


Context: Since 7500 yr ago, a situation with tides and currents, very similar to present has existed. Rates of sea-level rise had dropped so far, that natural sedimentation by the Rhine and coastal processes together, could compensate the transgression by the sea; in the last 7000 years, the coast line was roughly at the same location. In the southern North Sea, due to ongoing tectonic subsidence, the sea level is still rising, at the rate of about 1–3 cm (0.39–1.18 in) per century (1 metre or 39 inches in last 3000 years).

Question: When did tides and currents similar to our current system begin?

Question: Why did natural sedimentation by the Rhine compensate the transgression bby the sea?

Question: How long has the Rhine coastline been in the same location?

Question: Why is the current sea level rising?

Question: How quickly is the sea level rising?