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Zoology, lecture 10
Invertebrates: Annelida
| Question | Answer |
|---|---|
| Polychaeta | Class of annelida (more than 10,000 species) mostly marine, mostly between 5-10 cm, live under rocks, in coral reefs, abandoned shells, sand, mud. Some planktonic. Rarely found in large groups. Sessile/not. |
| Errantia | Free living worms (as opposed to sessile worms). They are homomeric. |
| Bispera brunea | Species of sessile polychaeta with secondary radial symmetry. They occupy tubes and can stay inside them or extend outwards. |
| Nereis | An errant genus of polychaete. |
| Palps | Elongated often segmented appendage carrying sensory cells usually found near the mouth. Used in sensation, locomotion and feeding. |
| Polychaeta characteristics | Errantia are homomeric, paired parapodia with lots of whiskers, head with eyes and palps, predators have cuticular jaws, sessiles have secondary radial symmetry. |
| Peritoneum function | Because the primary function of the coelomic cavity is containment of the sex cells they are produced by the peritoneum and released into the coelom where they are collected and used in reproduction. |
| Polychaeta pharynx | It can be extended outwards. If the species is predatorial it has cuticular jaws at the end of it. |
| Protostomial palps | Appendages at the front of the mouth with high concentrations of sensory cells. |
| Polychaeta sensory organs | Simple eyes that identify light source and strength. |
| Characteristics of sessile polychaetae | Secondary radial symmetry. At the front of the body there is a fan of tentacles used for filter feeding and respiration (often w/eyes at the ends). They live in a tube secreted by their ectoderm. |
| Christmas tree worm | תינולילס A species of sessile polychaetae. |
| Digging polychaeta | At the front of their bodies the parapodia are less pronounced and instead they have tentacles for eating/respiration there. |
| Characteristics of the oligochaeta | Class of annelida (about 3500 species) mostly land (moist ground) animals/fresh water. They specialized in digging. Parapodia disappeared, so did the whiskers. ex. tubifex, lumbricus (earth worms) |
| Aeolosoma, Tubifex, Dero and stylaria | All freshwater oligochaetes |
| Oligochaeta bristles (seta) | Thick setae are controlled by retractor muscles. They can dig, stick in their setae as anchors and move forward w/out slipping. Also hold onto their mates. |
| Hirudinea | תוקולע class of annelida mostly moist land/freshwater species (about 500), external parasites/predators. They developed from a common ancestor w/oligo's--no parapodia/setae. They have suckers (front/back) secrete hirudinin |
| Hirudinin | Substance secreted by hirudinea to prevent blood coagulation. |
| Dina | Predatorial hirudinea found in the Kineret. |
| Structure of hirudinea | More external line segments than internal structures (some of the septa disappeared). They have suckers at the front and back a branched digestive system and are hermaphroditic. |
| Hirudo medicinalis | A large rear sucker, small oral sucker. They are used in medicine. They are used today in certain types of surgeries to prevent coagulation. |
| Hirudinea eating mechanisms | Cuticular jaws near the oral sucker allow them to reach blood vessels. Dilator muscles of the pharynx allow them to suck. |
| Locomotion in segmented worms (annelida) | With the help of a metameric body and a hydorstatic skeleton they can alternate muscle flexing to create a snake like movement. |
| Annelida digging mechanism | Contraction of segments allows for crawling and digging. |
| Nerves and sensory systems of annelida | Some polychaeta have a ladder-like nervous system, the rest show unification of the two cords. Cerebral ganglia fuse. |
| Annelida ganglia | They have a fused cerebral ganglia with two extensions that wrap around the pharynx called the circumpharyngeal connective which then continues into the subpharyngeal ganglia. |
| Somite ganglia | Each segment has a pair of ganglia that then lead into the next segment. |
| Annelida Giant Fibers | Nerve fibers that function in fast transfer of sensory/nervous messages and can operate reflexes without first passing through ganglia. Allow for complex/precise function. |
| Annelida respiration | Diffusion through their entire body surface. In land species their skin is moist, in aquatic species parapodia increase surface area like gills. Circulation is through the coelomic liquid and blood vessels. |
| Annelida digestive system | It's one way allowing for specialization in parts. The entrance and exit are lined with ectoderm. Not digestion and circulation anymore! Just digestion. Mouth-esophagus-storage compartment (קפז) grinding stomach, gut. |
| Earthworm nutrition | They eat the dirt, extract organic components and release waste. |
| Grinding stomach in annelida | תנכות עביק with protrusions |
| Lumbricus terrestris | Scientific name of earthworm, a species of oligochaeta. |
| ינוציח לוכיע | External digestion refers to the digestion completed in the middle gut (through chewing, swallowing, storage and chemical digestion) |
| Oligochaete eating | Food is sucked into the pharynx, it's stored in the crop קפז saliva starts digestion. Gizzards grind and crush the food, active acidic chemical enzymes continue digestion. Basic enzymes work in the gut, water is absorbed in the rectum, waste comes out. |
| Earthworms and fertilizer | Because they process organic material they release a lot of waste rich in nutrients providing good fertilizer. |
| Annelida circulatory system | The only phylum with a closed circulatory system. |
| Closed circulatory system | Refers to a system of tubes that do not open. All passage is through diffusion/active absorption. |
| Circulatory mechanisms in annelida | Main dorsal and ventral arteries along the body length that move blood with the help of 5 pairs of pumping hearts with contraction capabilities. There are branches that then reach all organs/body parts. |
| Blood flow in a closed circulatory system | Ventral is front to back, dorsal is back to front, 5 aortic vessels function as accessory hearts pumping blood down, vessels of body wall and intestine are served. |
| Distribution of blood in a closed circulatory system | The blood richest in oxygen reaches the head first because it is the most important part. |
| Annelida excretory system | They have a pair of nephridia in each segment in the coelomic cavity. |
| Annelida nephridia | Opens with a cilliated funnel, continues into a twisted tube for purification of waste from the coelomic liquid and empty out the body wall through the nephridiopore. |
| Nephridia urinary system | Liquid goes into the nephrostome, through the septa into a curved messy tube covered in blood vessels that widens into the muscular bladder that forces the urine out through the nephridiopore. |
| תרזוח הגיפס | The curved tubes of the nephridia are covered with blood vessels that reabsorb all of the important nutrient before releasing waste. |
Created by:
YaelNoa
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