University of Louisiana at Lafayette
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This 14 page Class Notes was uploaded by Lauren Notetaker on Friday February 26, 2016. The Class Notes belongs to EBIO 1010 - 02 at Tulane University taught by Bruce Fleury in Spring 2016. Since its upload, it has received 20 views. For similar materials see Evolutionary Biology in Science at Tulane University.
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Date Created: 02/26/16
Week of February 22 notes EBIO Class Polychaeta - paddle worms, Nereis Class Oligochaeta - earthworms Class Hirudinea - leeches PhylumAnnelida - Class Polychaeta 5,400 species, fr Latin poly = many, chaeta = bristle - tube worms, fan worms, paddle worms, Nereis Most primitive annelids Mainly marine Common and abundant (13,425 worms/m found in Tampa Bay sediments!!) Highly cephalized Complex sensory organs Eyes with lens and retina Separate sexes External fertilization in water Mating swarms driven by the phases of the moon Trochophore larvae (suggests common ancestor with mollusks) Each segment has a pair of paddle-like appendages called parapodia Parapodia are covered with setae (hence many bristles) Used for swimming, crawling, burrowing Parapodia also provide more surface area for respiration by diffusion Most polychaetes also have gills (very active, so need more oxygen) Paddleworms have jaws of chitin (pincers), carnivorous or omnivorous Many polychaetes are filter feeders PhylumAnnelida - Class Oligochaeta (earthworms) 3,100 species, oligo = few - earthworms, Lumbricus Live in soil and in bottom sediments of fresh water habitats Afew species have re-invaded the ocean Extremely abundant, one meadow yielded 8,700 worms/m 2 Most earthworms are scavengers feeding on dead organic matter, mostly vegetation (detritus - detritivores) Fresh water forms eat detritus and protists Critically important in aerating the soil 22-40 metric tons of soil per hectare pass through the guts of earthworms every year If all the dirt ever churned up by worms were stacked up, it would cover the entire land surface of the Earth 300 miles thick, 50 times the height of Everest!! Important in bait industry (worm ranching or vermiculture) Lack parapodia, streamlined body - have to push through dirt Lack cephalization Lack eyes, but have light sensitive cells in some segments Why?? - Complex circulatory system, row of 5 blood vessels acts as a heart Pharynx draws in food Soil particles in the crop grind the food Reproduce asexually by transverse fission (like flatworms) Clitellum - series of segments swollen by large mucus glands Hermaphroditic, fertilize one another simultaneously Clitellum secretes mucus to hold worms together while they mate Fertilized eggs released into mucus Mucus dries into protective cocoon PhylumAnnelida - Class Hirudinea 500 species - leeches Most modified as parasites, some are scavengers or predators, feeding on worms, snails, insects 75% of species suck blood from mammals or crustaceans Common in fresh water habitats, a few species are marine or terrestrial Can be abundant - one stream in Illinois had 10,000 leeches/m !! 2 Highly modified as parasites Store blood meal in special pouches on the digestive tract Leeches suck up to 5 to 10 times their own weight in blood each time they feed Anterior and posterior sucker, attach to host Suckers also help them crawl across the bottom Coelom is greatly reduced, not divided into compartments like other annelids Leeches are strong swimmers, no longer need the adaptations of a burrowing animal Bite of the leech is antiseptic Leeches release an anticoagulant in their saliva, keeps the blood flowing For centuries doctors used leeches to bleed their patients (often to death) to get rid of “bad blood” (imbalance of humours) At height of the leech craze in the 1830’s, France was importing over 50 million medicinal leeches per year Medicinal leech is now a threatened species! Medicinal leeches (Hiruo medicinalis) undergoing a revival Used to drain blood clots and to drain postoperative swelling, bleeding Unlikely to evolve resistance - secretions go after seven critical steps in the clotting process! The traditional remedy is to pour salt on a feeding leech, or touch it with a burning cigarette - don’t pull it off! Recent studies show that these techniques cause the leech to vomit into the wound before letting go – enhances the risk of infection – peel them off gently with fingernails or a dull butter knife! One species of leech (Placobdelloides jaegerskioeldi) has one of the most unusual habitats of any annelid It lives and mates only in the rectum of the hippopotamus! Annelids share a common ancestor with mollusks Polychaetes and earthworms probably evolved from primitive burrowing marine worms Leeches and earthworms are sister clades, polychaetes are bit of a mystery… Leeches probably evolved from earthworms Lack parapodia and cephalization Hermaphroditic, develop a clitellum to breed Lay eggs in a cocoon Phylum Nematoda KingdomAnimalia Animalia Parazoa Eumetazoa Protostomia Spiralia Platyzoa – flatworms, rotifers Trochozoa – mollusks, annelids Ecdysozoa – nematodes, arthropods Deuterostomia Protostomes are divided into Spiralia – flatworms, rotifers, molluscs, annelids Ecdysozoa – animals that molt (nematodes, arthropods) Ecdysozoa is a relatively recent group Old story line in general biology was a gradual increase in complexity Through series of three body plans Segmentation (uniting annelids and arthropods) Turned out to be a fractured fairy tale… Many organisms appeared to be primitive but were not really (flatworms, nematodes) Body plans did not necessarily correspond to clades, some secondarily primitive etc… Segmentation turned out to be independently evolved in annelids and arthropods… Ecdysozoa - ecdysis means periodically shedding an exoskeleton in order to grow Cuticle molted Radial cleavage Don’t use cilia to move Lack trochophore larva (found in molluscs and annelids) Over 12,000 sp., maybe over 1 million!!, from Gr. nema = thread Potentially the most diverse group next to arthropods (mostly undiscovered) Incredibly abundant - 1 million worms per shovel full of garden soil, over 1 billion per acre of farmland Most are tiny (~ 1 mm), but Ascaris can reach 50 cm. (~ 20 inches) Round, bilaterally symmetric Pseudocoelomate (most pseudocoels are ecdysozoans) Mainly aquatic Usually molt four times during their lives basically filled with water Carnivores and parasites Lack circular muscles, use longitudinal muscles so thrash wildly about Interstitial habitat important (on land and in the sea) - life between the grains of soil… Because grains of soil are often covered with thin film of water, even terrestrial worms are basically aquatic Tough cuticle (non-living outer layer) resists abrasion, rings provide grip on surfaces to help burrow Unlike arthropods, cuticle has no chitin, uses collagen So nematode cuticle is porous, can still rely on diffusion Streamlined roundworm shape is an adaptation for moving through the soil Thrashing motion due to lack of circular muscles is a great adaptation for wriggling between grains of sand Excrete ammonia by diffusion Exchange gases by diffusion Primitive nervous system - nerve ring for brain, dorsal and ventral nerve cords Bristles and other structures for primitive mechanical and chemical senses Most have separate sexes Sexually dimorphic, males are smaller Males have a copulatory hook to hold open the female’s genital pore Economic importance Root nematodes cause over $5 billion crop damage per year Several medically important parasites Many harmful parasitic species: Ascaris etc. - intestinal roundworms, common in young vertebrates - close to the soil Infects 1 of 6 people worldwide, especially common in children in the southeastern US Female worm can hold up to 1 million eggs, and can lay up to 200,000 eggs per day!! Many harmful parasitic species: 340 million Ascaris victims per year with serious side effects, 100,000 deaths per year! Filarial worms - infect lymph system, cause grotesque swelling = elephantiasis Many harmful parasitic species: Trichinella - causes trichinosis in vertebrates (birds and mammals), worms form cysts in muscles of pigs etc Up to 500 million worms tunnel through host’s body - permanent organ and muscle damage Many harmful parasitic species: Hookworms - common in school children ~ 570 to 740 million people infected in the tropics alone - worms leave in feces, reenter through the soles of the feet At its peak in the late 19th and early 20th Century, hookworm infected ~ 40% of all southerners Primarily a disease of poor rural areas Enters through the soles of the feet, especially the skin between the toes Once in the body, hookworm migrates through the blood to the lungs, up into the throat Swallowed, carried down to the small intestine where it attaches itself to the lining of the intestine Feeds on the hosts blood Female lays up to 10,000 eggs a day, deposits them directly in the intestine Eggs are shed in feces If feces are deposited on warm soil, eggs hatch into larvae Can live in the soil for months before a victim comes along Southern soils and climate provided a nearly perfect new home for this old world parasite Primitive sanitary conditions in the south were a perfect breeding ground Bare feet (poverty), little medical care, no public health programs AfricanAmericans proved more resistant, maybe due to long exposure in nativeAfrica Slaves were healthier than the overseers! Subtle evolutionary revenge on slave owners! Symptoms are many and varied… Victims become pale, anemic, severe digestive problems Infection dulls mental processes, victims are easily fatigued - hence “germ of laziness” Muscles become weak, so abdomen protrudes (potbelly) Victims have a gaunt appearance, protruding shoulders (angel wings) Get unusual dietary cravings (pica) - eat chalk, dirt, paper.. Some were so badly infected they were blind, fluid of the eyes was filled with live worms!! Easy to cure (vermicidal purgative), very easy to become reinfected Must wear shoes, not defecate outdoors Widespread infection and suffering, went unrecognized until the early 20th Century Charles Wardell Stiles, zoologist with the USDA, was responsible for uncovering the extent of the infection Got John D. Rockefeller to fund a massive study, treatment program Poor condition of southern soldiers may have contributed to the outcome of the Civil War Robert Penn Warren describes rebel soldiers as “those gaunt, barefoot, whiskery scarecrows” Popular image of southerners as lazy, shiftless, dull-witted, etc… All symptoms of the germ of laziness Rockefeller Sanitary Commission for the Eradication of Hookworm Disease (1910-1915) Stiles found it very difficult to eradicate Subject of privys and excrement were taboo, especially in mixed company Stiles was sometimes threatened with violence when trying to interview victims, or asking for stool samples Editors of the Rockefeller Commission reports asked him to remove the section on privys as “exceedingly undignified, even disgusting” Mistrusted by medical doctors because he was a zoologist Mistrusted by local public health officials and residents as a carpetbagger Southerners took great offense “Where was the hookworm or lazy disease when it took five Yankee soldiers to whip one southerner?” asked the Macon Telegraph Many thought the whole thing was a conspiracy to sell shoes while Rockefeller secretly bought up shoe factories! Indoor plumbing essentially nonexistent, even outhouses few and far between 80% of southern rural schools and churches lacked a privy Even fewer found in rural farms and homes Despite massive attempt to train public health officials, local doctors, school children, mistrust undermined all efforts Tulane Medical School was one of the few supporters, exemplary in training its doctors to diagnose and cure the infection New vaccine enters clinical trials inAfrica in 2014 Goes after two key enzymes in hookworm metabolism, slowly kills it Ecological importance Aerate the soil (like earthworms) Recycle bacteria and fungi into animal tissue Guinea worm (Dracunculiasis medinensis) is thought to be the fiery serpent of biblical Israelites Probably dates toAncient Egypt (Pharaoh worm) Mentioned also in the Sanskrit Rig-Veda (14th Century BC) Arabs, Persians, were familiar with it, called it Medina vein – described by Rhazes andAvicenna in the 9 CenturyAD Adult nematode worm up to 1200 mm long! Intermediate host is a type of aquatic invertebrate called a copepod Copepod intermediate host discovered in 1870 byAlesej Pavlovich Fedchenko, a major step in early tropical medicine Worm enters the body through drinking water supply via the copepod Copepod dissolves in the stomach, releasing larval worms Worm matures and begins to tunnel under the skin host manipulation, gets you to plunge your skin in water which they want to disperse eggs Secretes irritant that causes papules to form on ankles and wrists Drives people to water, eggs released in water, eaten by copepod, people consume copepods when drinking water Ancient remedy was to patiently wind the worm out on a stick!! Practice was so common, physicians advertised with signs showing a worm on a stick This remedy is depicted on the staff of the Greek physicianAsclepius Thought to have practiced around 1200 BC, immortalized in the Iliad, revered as the Greek god of medicine This staff ofAsclepius is the true symbol of the medical profession The caduceus (entwined snakes) is really the symbol of the herald (Mercury) !?! Why did doctors switch to the caduceus of Mercury? Medicine was traditionally associated with alchemy, and alchemists were associated with Mercury (the hermetic arts)! PhylumArthropoda -Arachnids, Crustaceans, Insects thing about orders: know the class not the order We live in the age of arthropods. There are over three times as many species of arthropods as all other animal species on Earth put together. There may be as many as 20 to 30 million species of arthropods waiting to be discovered. Most of them are insects. At any one moment, there are some 10 individual arthropods alive on this planet. That’s ten billion billion organisms!! PhylumArthropoda Nearly 1.2 million named species of arthropods, does not include extinct species Subphylum Trilobita dominated Paleozoic marine ecology, over 10,000 species The cockroaches of the Cambrian… Some of the most ferocious predators in the history of life were arthropods Like Anomalocaris, worlds first large predator, a mighty 18” long… The terror of the trilobites! The giant sea scorpions were top dogs in the Paleozoic oceans Eurypterids were the largest arthropods that ever lived, up to nine feet long! Over one million named species (named), fr. Greek arthros = jointed, poda = foot Jointed appendages Eucoelomate protostomes Crustaceans dominate the sea, and insects dominate the land With few exceptions, each sticks to its own turf… Share common ancestor with polychaete worms Phylum Onychophora – velvet worms are sister clade, share common ancestor with arthropods; not on test Bodies are covered with a tough cuticle (= non-living outer layer) made of chitin and protein, which acts as an exoskeleton Problem - how can you get bigger if your skeleton is on the outside? Solution - must molt to grow (arthropods are vulnerable while molting) Open circulatory system Respiration via gills in aquatic forms Terrestrial forms rely on diffusion to exchange gases Sexes are separate Pronounced sexual dimorphism Internal fertilization in terrestrial forms Some aquatic forms have external fertilization Arthropods do everything with legs They creep, crawl, and swim with modified legs They use modified legs to bite, sting, suck, and chew They use modified legs as sensory organs (pedipalps, antennae) Many (like the crawfish) use modified legs to mate with! Each joint has a set of tendons, that can be pulled back and forth by tiny muscles These flexible joints allow an infinite variety of movements The first animals to succeed on land were arthropods The legs of arthropods were an essential instrument in that conquest It’s like having the ultimate Swiss army knife… Economically important Seafood industry, edible insects Pollinate commercial crops (fruit) Carry or cause many diseases, such as malaria, typhus, Lyme disease, bubonic plague Pollinate flowering plants Critical in most food chains Primary converters of plant to animal tissue Range from very small (mites) to 3.5 meters long recap on important topics ecdysozoa - animals that molt (nematodes and arthropods) charles styles Most are tiny - why?? Size limited by reliance on diffusion to exchange gases Exoskeleton would be so thick that a large insect couldn’t move about Escape detection by predators if small Fusion of segments into functional units (tagma - tagmosis) 3 major body sections head, thorax, abdomen head + thorax = cephalothorax One of the molecular tools behind our new map of biodiversity is comparison of hox genes Hox genes control the development of the animal body Hox genes in a fruit fly, for example, determine how each section of the body develops, front to back Amazingly enough, the genes are arrayed in the same relative order as the parts of the body they govern All higher animals turn out to have this same developmental toolkit It must have evolved very early in the history of higher animals Studies on arthropods have demonstrated that mutations in these genes are behind the incredible diversity of arthropod bodies Further mutations in Hox genes would have had a big effect on subsequent development Highly cephalized, very active Intricate mouthparts Highly developed CNS, 3 pair of ganglia fused into a brain Elaborate sensory organs Elaborate sensory organs Antennae Simple eyes Compound eyes KingdomAnimalia Animalia Parazoa Eumetazoa Protostomia Spiralia Platyzoa – flatworms, rotifers Trochozoa – mollusks, annelids Ecdysozoa – nematodes, arthropods Deuterostomia PhylumArthropoda Arthropod systematics is a pitched battle when it comes to sorting out major groups General agreement on four main clades, lot of controversy over how they are related to one another Subphylum Chelicerata - arachnids Subphylum Crustacea – crustaceans Subphylum Myriapoda – centipedes, millipedes Subphylum Hexapoda - insects one question on subphylum that’ll be easy Recent molecular evidence suggests that our traditional classification of insects and crustaceans may need to be revised Insects now appear to be more closely related to crustaceans than to millipedes and centipedes (clade Pancrustacea) Insects may be flying crustaceans!! PhylumArthropoda - Subphylum Chelicerata horseshoe crabs, spiders, scorpions, ticks, mites, daddy longlegs First pair of appendages modified as chelicerae Chelicerae are modified for manipulating food - usually fangs or pincers Lack antennae (no antennae on spiders) Class Merostomata - horseshoe crabs ClassArachnida - spiders, scorpions, ticks, mites Class Merostomata - horseshoe crabs Only 4 sp. of horseshoe crabs Nocturnal Feed on annelids and mollusks Swim on their backs Abundant, but live in deep water In spring, migrate inshore to mate on the beach during full or new moon, high tide Class Merostomata - Importance • Important food source for migratory birds • Source of lysate, which clots around dangerous bacteria - used to test equipment and drugs for infective bacteria - over one million lives saved so far! ClassArachnida 93,000 sp. - spiders, scorpions, ticks, mites Body = cephalothorax (fusion of head and thorax) + abdomen 4 pair of walking legs (=8 legs) First pair of appendages are chelicerae Second pair are pedipalps, modified for sensory functions and manipulating prey Mostly carnivorous (mites are herbivores) Secrete powerful digestive enzymes to dissolve prey, sip them like a root beer float ClassArachnida - Order Scorpiones 1,340 species Pedipalps modified as pincers Scorpion sting causes extreme pain, disorientation, salivation, convulsions, paralysis, asphyxia, and death Venomous sting in tail - 5,000 people a year are killed by scorpions May be first terrestrial arthropods, evolved in Silurian (~425 mya) Subphylum Chelicerata - ClassArachnida - OrderArenae 38,000 species - spiders Breathe by book lungs ex: nephila Use pedipalps as copulatory organs Posterior appendages modified as spinnerets, which produce silk threads used to build webs to capture prey Not all spiders spin webs Wolf spiders hunt through the leaf litter, leap onto their prey Tarantulas also hunt for big game Jumping spiders are common small spiders found in most homes and offices Jumping spiders have incredible eyes, may even have primitive color vision Can jump several times their body length to land on their tiny prey, attached to thread Elaborate courtship rituals ClassArachnida - OrderAcari 50,000 species - ticks and mites Most diverse arthropods next to insects Very tiny (< 1 mm) Cephalothorax and abdomen are fused Economically important Mites are major pests on crops, gardens, and house plants (spider mites) Ticks are blood-sucking parasites that carry several diseases, such as Lyme disease and Rocky Mountain spotted fever ClassArachnida - Order Opiliones 5,000 species - Daddy longlegs Oval body, cephalothorax and abdomen but no “waist” Extremely long legs Not spiders Predators, herbivores, scavengers Eyes mounted on a little tower on back Harvestmen were named by farmers, who noticed them in very large numbers at harvest time They feed on bits of vegetation, as well as insects, spiders, snails, and worms
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