sentence-transformers/squad huggingface dataset:
Passage: Most annelids have a pair of coelomata (body cavities) in each segment, separated from other segments by septa and from each other by vertical mesenteries. Each septum forms a sandwich with connective tissue in the middle and mesothelium (membrane that serves as a lining) from the preceding and following segments on either side. Each mesentery is similar except that the mesothelium is the lining of each of the pair of coelomata, and the blood vessels and, in polychaetes, the main nerve cords are embedded in it. The mesothelium is made of modified epitheliomuscular cells; in other words, their bodies form part of the epithelium but their bases extend to form muscle fibers in the body wall. The mesothelium may also form radial and circular muscles on the septa, and circular muscles around the blood vessels and gut. Parts of the mesothelium, especially on the outside of the gut, may also form chloragogen cells that perform similar functions to the livers of vertebrates: producing and storing glycogen and fat; producing the oxygen-carrier hemoglobin; breaking down proteins; and turning nitrogenous waste products into ammonia and urea to be excreted.

Question: What are coelomata?

Question: What are annelids' body cavities separated from other segments by?

Question: What are annelids' body cavities separated from each other by?

Question: What is the mesothelium made of?
Passage: Many annelids move by peristalsis (waves of contraction and expansion that sweep along the body), or flex the body while using parapodia to crawl or swim. In these animals the septa enable the circular and longitudinal muscles to change the shape of individual segments, by making each segment a separate fluid-filled "balloon". However, the septa are often incomplete in annelids that are semi-sessile or that do not move by peristalsis or by movements of parapodia – for example some move by whipping movements of the body, some small marine species move by means of cilia (fine muscle-powered hairs) and some burrowers turn their pharynges (throats) inside out to penetrate the sea-floor and drag themselves into it.

Question: How does peristalsis work?

Question: Why are annelids' segments like water-balloons?

Question: What are phrynges?

Question: What are cilia?
Passage: The fluid in the coelomata contains coelomocyte cells that defend the animals against parasites and infections. In some species coelomocytes may also contain a respiratory pigment – red hemoglobin in some species, green chlorocruorin in others (dissolved in the plasma) – and provide oxygen transport within their segments. Respiratory pigment is also dissolved in the blood plasma. Species with well-developed septa generally also have blood vessels running all long their bodies above and below the gut, the upper one carrying blood forwards while the lower one carries it backwards. Networks of capillaries in the body wall and around the gut transfer blood between the main blood vessels and to parts of the segment that need oxygen and nutrients. Both of the major vessels, especially the upper one, can pump blood by contracting. In some annelids the forward end of the upper blood vessel is enlarged with muscles to form a heart, while in the forward ends of many earthworms some of the vessels that connect the upper and lower main vessels function as hearts. Species with poorly developed or no septa generally have no blood vessels and rely on the circulation within the coelom for delivering nutrients and oxygen.

Question: What can coelomocyte cells defend against?

Question: What type of pigment is dissolved in annelids' blood?

Question: What runs the length of annelids' bodies with well-developed septa?

Question: What do annelids without septa have to use for circulation?
Passage: However, leeches and their closest relatives have a body structure that is very uniform within the group but significantly different from that of other annelids, including other members of the Clitellata. In leeches there are no septa, the connective tissue layer of the body wall is so thick that it occupies much of the body, and the two coelomata are widely separated and run the length of the body. They function as the main blood vessels, although they are side-by-side rather than upper and lower. However, they are lined with mesothelium, like the coelomata and unlike the blood vessels of other annelids. Leeches generally use suckers at their front and rear ends to move like inchworms. The anus is on the upper surface of the pygidium.

Question: What type of annelids are very different from others?

Question: What type of tissue takes up most of the body of a leech?

Question: How many coelomata do leeches have?

Question: What lines the coelomata of leeches?

Question: What do leeches use to move?
Passage: Feeding structures in the mouth region vary widely, and have little correlation with the animals' diets. Many polychaetes have a muscular pharynx that can be everted (turned inside out to extend it). In these animals the foremost few segments often lack septa so that, when the muscles in these segments contract, the sharp increase in fluid pressure from all these segments everts the pharynx very quickly. Two families, the Eunicidae and Phyllodocidae, have evolved jaws, which can be used for seizing prey, biting off pieces of vegetation, or grasping dead and decaying matter. On the other hand, some predatory polychaetes have neither jaws nor eversible pharynges. Selective deposit feeders generally live in tubes on the sea-floor and use palps to find food particles in the sediment and then wipe them into their mouths. Filter feeders use "crowns" of palps covered in cilia that wash food particles towards their mouths. Non-selective deposit feeders ingest soil or marine sediments via mouths that are generally unspecialized. Some clitellates have sticky pads in the roofs of their mouths, and some of these can evert the pads to capture prey. Leeches often have an eversible proboscis, or a muscular pharynx with two or three teeth.

Question: What does 'everted' mean?

Question: What part of a polychaete can be everted?

Question: What types of annelids have evolved jaws?

Question: What do annelids use jaws for?

Question: What do some annelids have 'crowns' of?
Passage: The gut is generally an almost straight tube supported by the mesenteries (vertical partitions within segments), and ends with the anus on the underside of the pygidium. However, in members of the tube-dwelling family Siboglinidae the gut is blocked by a swollen lining that houses symbiotic bacteria, which can make up 15% of the worms' total weight. The bacteria convert inorganic matter – such as hydrogen sulfide and carbon dioxide from hydrothermal vents, or methane from seeps – to organic matter that feeds themselves and their hosts, while the worms extend their palps into the gas flows to absorb the gases needed by the bacteria.

Question: What type of annelids are tube-dwelling?

Question: What blocks the Siboglinidae's gut?

Question: How much of a Siboglinidae's weight is symbiotic bacteria?

Question: What gases come from hydrothermal vents?

Question: What gases come from seeps?
Passage: Annelids with blood vessels use metanephridia to remove soluble waste products, while those without use protonephridia. Both of these systems use a two-stage filtration process, in which fluid and waste products are first extracted and these are filtered again to re-absorb any re-usable materials while dumping toxic and spent materials as urine. The difference is that protonephridia combine both filtration stages in the same organ, while metanephridia perform only the second filtration and rely on other mechanisms for the first – in annelids special filter cells in the walls of the blood vessels let fluids and other small molecules pass into the coelomic fluid, where it circulates to the metanephridia. In annelids the points at which fluid enters the protonephridia or metanephridia are on the forward side of a septum while the second-stage filter and the nephridiopore (exit opening in the body wall) are in the following segment. As a result, the hindmost segment (before the growth zone and pygidium) has no structure that extracts its wastes, as there is no following segment to filter and discharge them, while the first segment contains an extraction structure that passes wastes to the second, but does not contain the structures that re-filter and discharge urine.

Question: What do metanephridia remove?

Question: What do annelids without blood vessels do to remove waste?

Question: How many stages are there in annelids' waste filtration?

Question: What annelid system combines both filtration states in one organ?
Passage: It is thought that annelids were originally animals with two separate sexes, which released ova and sperm into the water via their nephridia. The fertilized eggs develop into trochophore larvae, which live as plankton. Later they sink to the sea-floor and metamorphose into miniature adults: the part of the trochophore between the apical tuft and the prototroch becomes the prostomium (head); a small area round the trochophore's anus becomes the pygidium (tail-piece); a narrow band immediately in front of that becomes the growth zone that produces new segments; and the rest of the trochophore becomes the peristomium (the segment that contains the mouth).

Question: How many sexes of annelids were there originally?

Question: What releases sperm from annelids?

Question: What do annelid eggs become?

Question: What do annelids' larvae live like?

Question: What does the trochophore become when annelids mature?
Passage: However, the lifecycles of most living polychaetes, which are almost all marine animals, are unknown, and only about 25% of the 300+ species whose lifecycles are known follow this pattern. About 14% use a similar external fertilization but produce yolk-rich eggs, which reduce the time the larva needs to spend among the plankton, or eggs from which miniature adults emerge rather than larvae. The rest care for the fertilized eggs until they hatch – some by producing jelly-covered masses of eggs which they tend, some by attaching the eggs to their bodies and a few species by keeping the eggs within their bodies until they hatch. These species use a variety of methods for sperm transfer; for example, in some the females collect sperm released into the water, while in others the males have a penis that inject sperm into the female. There is no guarantee that this is a representative sample of polychaetes' reproductive patterns, and it simply reflects scientists' current knowledge.

Question: How many species of polychaetes have known lifecycles?

Question: What percent of polychaetes produce yolk-rich eggs?

Question: What is the benefit of yolk-rich eggs?

Question: What are most polychaetes' eggs covered in?
Passage: Some polychaetes breed only once in their lives, while others breed almost continuously or through several breeding seasons. While most polychaetes remain of one sex all their lives, a significant percentage of species are full hermaphrodites or change sex during their lives. Most polychaetes whose reproduction has been studied lack permanent gonads, and it is uncertain how they produce ova and sperm. In a few species the rear of the body splits off and becomes a separate individual that lives just long enough to swim to a suitable environment, usually near the surface, and spawn.

Question: What do some non-single-sex polychaetes do?

Question: What are most polychaetes lacking for reproduction?

Question: How do some annelids get a one-time chance at a better spawning spot?
Passage: Most mature clitellates (the group that includes earthworms and leeches) are full hermaphrodites, although in a few leech species younger adults function as males and become female at maturity. All have well-developed gonads, and all copulate. Earthworms store their partners' sperm in spermathecae ("sperm stores") and then the clitellum produces a cocoon that collects ova from the ovaries and then sperm from the spermathecae. Fertilization and development of earthworm eggs takes place in the cocoon. Leeches' eggs are fertilized in the ovaries, and then transferred to the cocoon. In all clitellates the cocoon also either produces yolk when the eggs are fertilized or nutrients while they are developing. All clitellates hatch as miniature adults rather than larvae.

Question: What annelid group includes leeches and earthworms?

Question: What type of sex are most earthworms?

Question: Where are leeches' eggs fertilized?

Question: Where do leeches move their eggs to?

Question: What type of annelids hatch as miniature adults?
Passage: Charles Darwin's book The Formation of Vegetable Mould through the Action of Worms (1881) presented the first scientific analysis of earthworms' contributions to soil fertility. Some burrow while others live entirely on the surface, generally in moist leaf litter. The burrowers loosen the soil so that oxygen and water can penetrate it, and both surface and burrowing worms help to produce soil by mixing organic and mineral matter, by accelerating the decomposition of organic matter and thus making it more quickly available to other organisms, and by concentrating minerals and converting them to forms that plants can use more easily. Earthworms are also important prey for birds ranging in size from robins to storks, and for mammals ranging from shrews to badgers, and in some cases conserving earthworms may be essential for conserving endangered birds.

Question: Who published a book about worms in 1881?

Question: What was the first scientific study of how earthworms help soil?

Question: Where do earthworms prefer to live on the surface?

Question: How does burrowers' loosening help the soil?

Question: What is the largest bird that eats earthworms?
Passage: Terrestrial annelids can be invasive in some situations. In the glaciated areas of North America, for example, almost all native earthworms are thought to have been killed by the glaciers and the worms currently found in those areas are all introduced from other areas, primarily from Europe, and, more recently, from Asia. Northern hardwood forests are especially negatively impacted by invasive worms through the loss of leaf duff, soil fertility, changes in soil chemistry and the loss of ecological diversity. Especially of concern is Amynthas agrestis and at least one state (Wisconsin) has listed it as a prohibited species.

Question: Where were native earthworms killed by glaciers?

Question: Where did most of the current earthworms in glacial areas come from?

Question: What type of forests can be hurt by invasive worms?
Passage: Earthworms make a significant contribution to soil fertility. The rear end of the Palolo worm, a marine polychaete that tunnels through coral, detaches in order to spawn at the surface, and the people of Samoa regard these spawning modules as a delicacy. Anglers sometimes find that worms are more effective bait than artificial flies, and worms can be kept for several days in a tin lined with damp moss. Ragworms are commercially important as bait and as food sources for aquaculture, and there have been proposals to farm them in order to reduce over-fishing of their natural populations. Some marine polychaetes' predation on molluscs causes serious losses to fishery and aquaculture operations.

Question: What type of annelid tunnels through coral?

Question: What annelid's rear end do Samoans like to eat?

Question: What type of bait do experienced anglers prefer?

Question: What do some polychaetes eat that has been causing problems?

Question: What type of worm have there been proposals to farm?
Passage: Accounts of the use of leeches for the medically dubious practise of blood-letting have come from China around 30 AD, India around 200 AD, ancient Rome around 50 AD and later throughout Europe. In the 19th century medical demand for leeches was so high that some areas' stocks were exhausted and other regions imposed restrictions or bans on exports, and Hirudo medicinalis is treated as an endangered species by both IUCN and CITES. More recently leeches have been used to assist in microsurgery, and their saliva has provided anti-inflammatory compounds and several important anticoagulants, one of which also prevents tumors from spreading.

Question: When did leeches begin being used for blood-letting?

Question: Where did leeches begin being used for blood-letting?

Question: When did Rome begin using leeches?

Question: When did India begin using leeches?

Question: Which organizations list Hirudo medicinalis as endangered?
Passage: Since annelids are soft-bodied, their fossils are rare. Polychaetes' fossil record consists mainly of the jaws that some species had and the mineralized tubes that some secreted. Some Ediacaran fossils such as Dickinsonia in some ways resemble polychaetes, but the similarities are too vague for these fossils to be classified with confidence. The small shelly fossil Cloudina, from 549 to 542 million years ago, has been classified by some authors as an annelid, but by others as a cnidarian (i.e. in the phylum to which jellyfish and sea anemones belong). Until 2008 the earliest fossils widely accepted as annelids were the polychaetes Canadia and Burgessochaeta, both from Canada's Burgess Shale, formed about 505 million years ago in the early Cambrian. Myoscolex, found in Australia and a little older than the Burgess Shale, was possibly an annelid. However, it lacks some typical annelid features and has features which are not usually found in annelids and some of which are associated with other phyla. Then Simon Conway Morris and John Peel reported Phragmochaeta from Sirius Passet, about 518 million years old, and concluded that it was the oldest annelid known to date. There has been vigorous debate about whether the Burgess Shale fossil Wiwaxia was a mollusc or an annelid. Polychaetes diversified in the early Ordovician, about 488 to 474 million years ago. It is not until the early Ordovician that the first annelid jaws are found, thus the crown-group cannot have appeared before this date and probably appeared somewhat later. By the end of the Carboniferous, about 299 million years ago, fossils of most of the modern mobile polychaete groups had appeared. Many fossil tubes look like those made by modern sessile polychaetes , but the first tubes clearly produced by polychaetes date from the Jurassic, less than 199 million years ago.

Question: When did Cloudina exist?

Question: What do some people think Cloudina should be called instead of an annelid?

Question: How old were the fossils of Canadia and Burgessochaeta found in Canada?

Question: What era was underway 505 million years ago?

Question: Where was Myoscolex found?
Passage: The earliest good evidence for oligochaetes occurs in the Tertiary period, which began 65 million years ago, and it has been suggested that these animals evolved around the same time as flowering plants in the early Cretaceous, from 130 to 90 million years ago. A trace fossil consisting of a convoluted burrow partly filled with small fecal pellets may be evidence that earthworms were present in the early Triassic period from 251 to 245 million years ago. Body fossils going back to the mid Ordovician, from 472 to 461 million years ago, have been tentatively classified as oligochaetes, but these identifications are uncertain and some have been disputed.

Question: When did the Tertiary period begin?

Question: What era did oligochaetes evolve in?

Question: What type of annelid fossils have been found from the mid Ordovician period?

Question: When were the earliest annelid fossils found?
Passage: Traditionally the annelids have been divided into two major groups, the polychaetes and clitellates. In turn the clitellates were divided into oligochaetes, which include earthworms, and hirudinomorphs, whose best-known members are leeches. For many years there was no clear arrangement of the approximately 80 polychaete families into higher-level groups. In 1997 Greg Rouse and Kristian Fauchald attempted a "first heuristic step in terms of bringing polychaete systematics to an acceptable level of rigour", based on anatomical structures, and divided polychaetes into:

Question: What two groups are annelids traditionally divided among?

Question: What subtype of clitellates contains earthworms?

Question: What subtype of clitellates contains leeches?

Question: How many polychaete families are there?

Question: When did Greg Rouse begin trying to categorize polychaetes?
Passage: In 2007 Torsten Struck and colleagues compared 3 genes in 81 taxa, of which 9 were outgroups, in other words not considered closely related to annelids but included to give an indication of where the organisms under study are placed on the larger tree of life. For a cross-check the study used an analysis of 11 genes (including the original 3) in 10 taxa. This analysis agreed that clitellates, pogonophorans and echiurans were on various branches of the polychaete family tree. It also concluded that the classification of polychaetes into Scolecida, Canalipalpata and Aciculata was useless, as the members of these alleged groups were scattered all over the family tree derived from comparing the 81 taxa. In addition, it also placed sipunculans, generally regarded at the time as a separate phylum, on another branch of the polychaete tree, and concluded that leeches were a sub-group of oligochaetes rather than their sister-group among the clitellates. Rouse accepted the analyses based on molecular phylogenetics, and their main conclusions are now the scientific consensus, although the details of the annelid family tree remain uncertain.

Question: Who compared annelid genes in 2007?

Question: How many annelid genes did Torsten Struck first compare?

Question: How many annelid genes did Torsten Struck compare for a cross-check?

Question: What subtypes of polychaetes were useless classifications, according to the 2007 study?

Question: What did Rouse decide leeches were a subgroup of?
Passage: In addition to re-writing the classification of annelids and 3 previously independent phyla, the molecular phylogenetics analyses undermine the emphasis that decades of previous writings placed on the importance of segmentation in the classification of invertebrates. Polychaetes, which these analyses found to be the parent group, have completely segmented bodies, while polychaetes' echiurans and sipunculan offshoots are not segmented and pogonophores are segmented only in the rear parts of their bodies. It now seems that segmentation can appear and disappear much more easily in the course of evolution than was previously thought. The 2007 study also noted that the ladder-like nervous system, which is associated with segmentation, is less universal previously thought in both annelids and arthropods.[n 2]

Question: How many previously-separate phyla did the 2007 study reclassify?

Question: What did the 2007 study decide was the parent group for annelids?

Question: What offshoots of polychaetes are unsegmented?

Question: What offshoots of polychaetes are only segmented in the rear?

Question: What nervous system structure is less univeral among annelids than was thought before 2007?