romikgosai/squad_modified huggingface dataset:
Annelids' cuticles are made of collagen fibers, usually in layers that spiral in alternating directions so that the fibers cross each other. These are secreted by the one-cell deep epidermis (outermost skin layer). A few marine annelids that live in tubes lack cuticles, but their tubes have a similar structure, and mucus-secreting glands in the epidermis protect their skins. Under the epidermis is the dermis, which is made of connective tissue, in other words a combination of cells and non-cellular materials such as collagen. Below this are two layers of muscles, which develop from the lining of the coelom (body cavity): circular muscles make a segment longer and slimmer when they contract, while under them are longitudinal muscles, usually four distinct strips, whose contractions make the segment shorter and fatter. Some annelids also have oblique internal muscles that connect the underside of the body to each side.

Questions and answers:
["
Q: How are the layers arranged in annelids' cuticles?
A: spiral in alternating directions", "
Q: What are annelids' cuticles made out of?
A: collagen fibers", '
Q: What do non-cuticle annelids use to protect their skin?
A: mucus-secreting glands in the epidermis', '
Q: What layer is under the epidermis?
A: the dermis', "
Q: What does 'coelom' mean?
A: (body cavity"]
The setae ("hairs") of annelids project out from the epidermis to provide traction and other capabilities. The simplest are unjointed and form paired bundles near the top and bottom of each side of each segment. The parapodia ("limbs") of annelids that have them often bear more complex chetae at their tips – for example jointed, comb-like or hooked. Chetae are made of moderately flexible β-chitin and are formed by follicles, each of which has a chetoblast ("hair-forming") cell at the bottom and muscles that can extend or retract the cheta. The chetoblasts produce chetae by forming microvilli, fine hair-like extensions that increase the area available for secreting the cheta. When the cheta is complete, the microvilli withdraw into the chetoblast, leaving parallel tunnels that run almost the full length of the cheta. Hence annelids' chetae are structurally different from the setae ("bristles") of arthropods, which are made of the more rigid α-chitin, have a single internal cavity, and are mounted on flexible joints in shallow pits in the cuticle.

Questions and answers:
['
Q: What are parapodia?
A: limbs', '
Q: What do chetoblast cells do?
A: hair-forming', '
Q: What hair-like extensions do chetoblasts make?
A: microvilli', '
Q: What are setae?
A: bristles']
Nearly all polychaetes have parapodia that function as limbs, while other major annelid groups lack them. Parapodia are unjointed paired extensions of the body wall, and their muscles are derived from the circular muscles of the body. They are often supported internally by one or more large, thick chetae. The parapodia of burrowing and tube-dwelling polychaetes are often just ridges whose tips bear hooked chetae. In active crawlers and swimmers the parapodia are often divided into large upper and lower paddles on a very short trunk, and the paddles are generally fringed with chetae and sometimes with cirri (fused bundles of cilia) and gills.

Questions and answers:
['
Q: What are cirri?
A: fused bundles of cilia', '
Q: What kind of parapodia do burrowing annelids often have?
A: ridges whose tips bear hooked chetae', '
Q: What type of annelids have limb-like parapodia?
A: polychaetes', '
Q: What are parapodia?
A: unjointed paired extensions of the body wall']
The brain generally forms a ring round the pharynx (throat), consisting of a pair of ganglia (local control centers) above and in front of the pharynx, linked by nerve cords either side of the pharynx to another pair of ganglia just below and behind it. The brains of polychaetes are generally in the prostomium, while those of clitellates are in the peristomium or sometimes the first segment behind the peristomium. In some very mobile and active polychaetes the brain is enlarged and more complex, with visible hindbrain, midbrain and forebrain sections. The rest of the central nervous system is generally "ladder-like", consisting of a pair of nerve cords that run through the bottom part of the body and have in each segment paired ganglia linked by a transverse connection. From each segmental ganglion a branching system of local nerves runs into the body wall and then encircles the body. However, in most polychaetes the two main nerve cords are fused, and in the tube-dwelling genus Owenia the single nerve chord has no ganglia and is located in the epidermis.

Questions and answers:
['
Q: What are ganglia?
A: local control centers', "
Q: What is an annelid's brain in a ring around?
A: the pharynx", '
Q: What is a pharynx?
A: throat', "
Q: Where are clitellates' brains?
A: in the peristomium or sometimes the first segment behind the peristomium", "
Q: Where are polychaetes' brains?
A: in the prostomium"]
As in arthropods, each muscle fiber (cell) is controlled by more than one neuron, and the speed and power of the fiber's contractions depends on the combined effects of all its neurons. Vertebrates have a different system, in which one neuron controls a group of muscle fibers. Most annelids' longitudinal nerve trunks include giant axons (the output signal lines of nerve cells). Their large diameter decreases their resistance, which allows them to transmit signals exceptionally fast. This enables these worms to withdraw rapidly from danger by shortening their bodies. Experiments have shown that cutting the giant axons prevents this escape response but does not affect normal movement.

Questions and answers:
["
Q: What species group are annelids' muscle control similar to?
A: arthropods", '
Q: What are giant axons?
A: the output signal lines of nerve cells', '
Q: How do annelids withdraw from danger?
A: shortening their bodies']
The sensors are primarily single cells that detect light, chemicals, pressure waves and contact, and are present on the head, appendages (if any) and other parts of the body. Nuchal ("on the neck") organs are paired, ciliated structures found only in polychaetes, and are thought to be chemosensors. Some polychaetes also have various combinations of ocelli ("little eyes") that detect the direction from which light is coming and camera eyes or compound eyes that can probably form images. The compound eyes probably evolved independently of arthropods' eyes. Some tube-worms use ocelli widely spread over their bodies to detect the shadows of fish, so that they can quickly withdraw into their tubes. Some burrowing and tube-dwelling polychaetes have statocysts (tilt and balance sensors) that tell them which way is down. A few polychaete genera have on the undersides of their heads palps that are used both in feeding and as "feelers", and some of these also have antennae that are structurally similar but probably are used mainly as "feelers".

Questions and answers:
["
Q: What kind of things can annelids' sensors detect?
A: light, chemicals, pressure waves and contact", "
Q: What does 'nuchal' mean?
A: on the neck", '
Q: What type of annelids have nuchal organs?
A: polychaetes', '
Q: What are the nuchal organs thought to do?
A: chemosensors', "
Q: What term means 'little eyes'?
A: ocelli"]
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.

Questions and answers:
['
Q: What are coelomata?
A: body cavities', "
Q: What are annelids' body cavities separated from other segments by?
A: septa", "
Q: What are annelids' body cavities separated from each other by?
A: vertical mesenteries", '
Q: What is the mesothelium made of?
A: modified epitheliomuscular cells']
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.

Questions and answers:
['
Q: How does peristalsis work?
A: waves of contraction and expansion that sweep along the body', "
Q: Why are annelids' segments like water-balloons?
A: the septa enable the circular and longitudinal muscles to change the shape of individual segments", '
Q: What are phrynges?
A: throats', '
Q: What are cilia?
A: fine muscle-powered hairs']
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.

Questions and answers:
['
Q: What can coelomocyte cells defend against?
A: parasites and infections', "
Q: What type of pigment is dissolved in annelids' blood?
A: Respiratory", "
Q: What runs the length of annelids' bodies with well-developed septa?
A: blood vessels", '
Q: What do annelids without septa have to use for circulation?
A: circulation within the coelom']
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.

Questions and answers:
['
Q: What type of annelids are very different from others?
A: leeches and their closest relatives', '
Q: What type of tissue takes up most of the body of a leech?
A: connective tissue layer of the body wall', '
Q: How many coelomata do leeches have?
A: two', '
Q: What lines the coelomata of leeches?
A: mesothelium', '
Q: What do leeches use to move?
A: suckers at their front and rear ends']
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.

Questions and answers:
["
Q: What does 'everted' mean?
A: turned inside out to extend", '
Q: What part of a polychaete can be everted?
A: pharynx', '
Q: What types of annelids have evolved jaws?
A: Eunicidae and Phyllodocidae', '
Q: What do annelids use jaws for?
A: seizing prey, biting off pieces of vegetation, or grasping dead and decaying matter', "
Q: What do some annelids have 'crowns' of?
A: palps covered in cilia"]
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.

Questions and answers:
['
Q: What type of annelids are tube-dwelling?
A: Siboglinidae', "
Q: What blocks the Siboglinidae's gut?
A: a swollen lining", "
Q: How much of a Siboglinidae's weight is symbiotic bacteria?
A: 15%", '
Q: What gases come from hydrothermal vents?
A: hydrogen sulfide and carbon dioxide', '
Q: What gases come from seeps?
A: methane']
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.

Questions and answers:
['
Q: What do metanephridia remove?
A: soluble waste products', '
Q: What do annelids without blood vessels do to remove waste?
A: protonephridia', "
Q: How many stages are there in annelids' waste filtration?
A: two", '
Q: What annelid system combines both filtration states in one organ?
A: protonephridia']
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).

Questions and answers:
['
Q: How many sexes of annelids were there originally?
A: two', '
Q: What releases sperm from annelids?
A: nephridia', '
Q: What do annelid eggs become?
A: trochophore larvae', "
Q: What do annelids' larvae live like?
A: plankton", '
Q: What does the trochophore become when annelids mature?
A: the prostomium (head)']
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.

Questions and answers:
['
Q: How many species of polychaetes have known lifecycles?
A: about 25%', '
Q: What percent of polychaetes produce yolk-rich eggs?
A: 14%', '
Q: What is the benefit of yolk-rich eggs?
A: reduce the time the larva needs to spend among the plankton', "
Q: What are most polychaetes' eggs covered in?
A: jelly"]
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.

Questions and answers:
['
Q: What do some non-single-sex polychaetes do?
A: change sex', '
Q: What are most polychaetes lacking for reproduction?
A: permanent gonads', '
Q: How do some annelids get a one-time chance at a better spawning spot?
A: the rear of the body splits off and becomes a separate individual']
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.

Questions and answers:
['
Q: What annelid group includes leeches and earthworms?
A: clitellates', '
Q: What type of sex are most earthworms?
A: hermaphrodites', "
Q: Where are leeches' eggs fertilized?
A: in the ovaries", '
Q: Where do leeches move their eggs to?
A: the cocoon', '
Q: What type of annelids hatch as miniature adults?
A: clitellates']
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.

Questions and answers:
['
Q: Who published a book about worms in 1881?
A: Charles Darwin', '
Q: What was the first scientific study of how earthworms help soil?
A: The Formation of Vegetable Mould through the Action of Worms', '
Q: Where do earthworms prefer to live on the surface?
A: generally in moist leaf litter', "
Q: How does burrowers' loosening help the soil?
A: oxygen and water can penetrate it", '
Q: What is the largest bird that eats earthworms?
A: storks']
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.

Questions and answers:
['
Q: Where were native earthworms killed by glaciers?
A: glaciated areas of North America', '
Q: Where did most of the current earthworms in glacial areas come from?
A: Europe', '
Q: What type of forests can be hurt by invasive worms?
A: Northern hardwood forests']