University of Louisiana at Lafayette
Popular in Evolutionary Biology
Popular in Science
Joseph Merritt Ramsey
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This 13 page Class Notes was uploaded by Lauren Notetaker on Sunday March 6, 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 18 views. For similar materials see Evolutionary Biology in Science at Tulane University.
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Date Created: 03/06/16
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 PhylumArthropoda - Subphylum Crustacea crabs, shrimp, lobsters, brine shrimp, isopods, barnacles PhylumArthropoda - Subphylum Crustacea 38,000 species - crabs, shrimp, lobsters, brine shrimp, isopods, barnacles Mostly marine - crustaceans dominate the sea the way insects dominate the land Biramous appendages Legs on both abdomen and thorax First two pair of appendages modified as antennae Third pair of appendages are mandibles, for tough biting and chewing (other arthropods have mandibles) All crustaceans share a common larval form, the nauplius larva know all larva Order Isopoda - one of the few successful terrestrial crustaceans (plus a few crabs) Very common, abundant Curl up in a spiral to protect themselves Feed on decaying vegetation (detritivores) PhylumArthropoda - Subphylum Myriapoda centipedes, millipedes Centipedes and millipedes form the subphylum Myriapoda (lots and lots of legs) Class Chilopoda - centipedes (more dangerous) Class Diplopoda – millipedes (fatter) Subphylum Myriapoda - Class Chilopoda – centipedes 2,800 species, centi = 100, but they don’t really have 100 legs One pair of legs per segment Uniramous appendages Carnivorous, eat mostly insects Poison fangs, very painful bite, a dangerous creature!! Subphylum Myriapoda -Class Diplopoda - millipedes 11,000 species, milli = 1,000, but they don’t really have 1,000 legs Mostly herbivorous, feed on decaying vegetation (detritivore = feed on detritus) Two pair of legs per segment (fusion) Curl up in a spiral to protect themselves, secrete a defensive fluid (cyanide gas) PhylumArthropoda - Subphylum Hexapoda - Class Insecta – insects Over 925,000 named species, maybe up to 30 million species undiscovered Insects evolved about 200 mya, cockroaches and dragonflies were the first to appear We live in theAge of Insects Body consists of head, thorax, abdomen Uniramous appendages 3 pair of walking legs (= 6 legs) Communicate by scent and sound (pheromones) Compound eyes Terrestrial forms breathe via openings along the abdomen called spiracles Spiracles open into a network of tiny tubes called trachea Lose water vapor through trachea, many insects have valves to close spiracles Excrete by means of malphigian tubules, projections of the digestive tract Only invertebrates that fly One or two pair of wings (usually two) Extremely elaborate mouthparts, highly modified for chewing, sucking, or piercing Insects undergo metamorphosis – simple or complete Simple metamorphosis (hemimetabolous) - about 10% No resting stage, juvenile looks like tiny adult (ex. grasshopper) Complete metamorphosis (holometabolous) - about 90% Resting stage (pupa), adults look different, live in different places, eat different things (ex. butterfly) Orders of Insects Hymenoptera - ants, bees, wasps Coleoptera - beetles Lepidoptera - butterflies and moths Diptera - flies, mosquitoes Orthoptera - grasshoppers, crickets, roaches Isoptera - termites Phylum Echinodermata (sea lilies, starfish, sea urchins, sea cucumbers) KingdomAnimalia Parazoa Eumetazoa Protostomia Deuterostomia Echinodermata Chordata Phylum Echinodermata 6,000 species, fr. Greek ekhinos = spine, derma = skin Eucoelomate deuterostomes common ancestor Sedentary, slow moving, marine animals Five-part radial symmetry (pentamerous) Lack cephalization Echinoderms have no brain or CNS…Why? radial - sedentary/sessile; not going anywhere in a hurry Their nervous system reflects their return to a sedentary lifestyle, radial symmetry Five-part radial symmetry is superficial – ancestor was bilateral Asexual reproduction by splitting or fragmentation - great regenerative power Sexual reproduction by external fertilization Larvae are bilaterally symmetric, cephalized, reflect ancestral echinoderms Endoskeleton of calcium carbonate Endoskeleton consists of numerous small plates, covered by a thin skin (epidermis) Many small spines extend from the body Open circulatory system Large coelom functions in both respiration and circulation Locomotion and feeding by means of tube feet; propelled by hydraulic system Here’s how it works… Water flows through the madreporite (like a filter, slightly off center; technically bilaterally symmetric) Water passes into a ring canal Water passes into the radial canals (arms) Water passes into tube feet Longitudinal muscles contract to move the tube feet back and forth Water flows through small filter (madreporite) Water passes from the madreporite into the ring canal Water passes into the radial canals (arms) Water passes into tube feet Each tube foot resembles a miniature eye dropper The bulb or ampullae squeezes water into the tube foot One-way valve keeps water from flowing back out until the bulb relaxes Longitudinal muscles, attached to either side of the tube feet, contract to pull the stiffened foot back and forth The coordinated action of thousands of tiny tube feet pulls the animal along Nervous system consists of a simple nerve ring Five branches from nerve ring enervate the five arms Echinoderms have an odd type of connective tissue called catch or mutable (change) connective tissue Catch connective tissue can change from solid to near liquid at will Can shed arms to escape predators Class Crinoidea - sea lilies ClassAsteroidea - star fish Class Echinoidea - sea urchins, sand dollars Class Ophiuroidea - brittle stars Class Holothuridea - sea cucumbers Class Crinoidea 630 species, fr. Greek krinon = lily - sea lilies, feather stars Living fossils, sessile forms are ancient species – modern forms are mainly motile Mouth and anus atop disk, disk may be attached to a stalk (primitive) Tube feet modified for filter feeding ClassAsteroidea 1,500 species, fr. Greek aster = star, starfish Important marine predators - wolves in slow motion one of most common fossils Most have five arms (some have up to 20!) Superficial radial symmetry (madreporite is off center) Some starfish feed on bivalves Clamp onto shell with tube feet and pull... Can extrude their cardiac stomach adductor muscle has to take a breath so at that moment it shoves stomach inside it and floods with digestive enzymes Slide stomach through tiny gaps in shell (0.10 mm gaps within normal shell tolerance) Digest bivalve alive in its own shell!! Small projections of skin stick out near the base of the spines These finger-like projections are called dermal gills Dermal gills aid in respiration and excretion (accomplished by diffusion) Numerous small stalks also project from the skin These stalks, called pedicillaria, bear tiny pincers Pedicillaria can be used to help capture tiny prey also prevent other things from putting a house on it Pedicillaria can be also be used to repel boarders Class Echinoidea 950 species, fr. Greek ekhinos = spine - sea urchins, sand dollars Lack arms but you can see remnants diadema is most common to step on aristotle’s lantern is little mouth pinchers Still show 5 part radial symmetry (look at the 5 rows of tube feet) Over 5,000 fossil species of urchins! Well protected by sharp spines attached to the skeletal plates under the skin Spines are movable, help urchins creep about Many urchins are well defended with long sharp spines Modified tube feet constantly sense and probe the environment as the urchin moves along Feed by scraping algae off hard surfaces using sharp shelly “teeth” Ecologically important, can occur in large numbers and devastate kelp beds and coral reefs Economically important – harvested for their gonads (ewww…); popular sushi dish Sea urchin roe is not actually roe (eggs) but gonads Popular dish in the Orient (Japanese sushi called “uni”), Spain, Greece, Italy and Chile Thought to be an aphrodisiac Contains one of the cannabinoids (chemicals in marihuana) Sand dollars are bilateral, sedentary endo skeleton Highly modified for burrowing in sand Sedentary, move about 7-50 cm per day Feed on organic matter in the sand as they burrow through it Class Ophiuroidea 2,000 species, fr. Greek ophis = snake, oura = tail - brittle stars, basket stars Resemble starfish, but with long brittle arms Brittlestars (and most starfish) lack an anus Many are small, fast-moving Carnivores, scavengers, and filter feeders, most diverse group of echinoderms Brittle stars can be very abundant, carpeting the sea floor with their long and delicate filter- feeding arms Class Holothuridea 1,500 species, fr. Greek holothurum = sedentary marine animal (!) Sedentary marine animals Superficial 5 part radial symmetry Skeletal plates under the skin reduced to a few scattered plates tube in a tube Tube feet modified for filter feeding on plankton (algae, protozoa, larvae, gametes) Mouth surrounded by tentacles Tentacles coated with mucus (yum!) Mucus traps tiny prey Brings tentacles into mouth to wipe off mucus Recoats tentacles and extends to feed again Several species scour the ocean floor like tiny vacuum cleaners Economic importance: Sea cucumbers are a prized (and expensive) gourmet delicacy in the Orient Sold as trepang or beche-de-mere Unique defensive mechanism - they evert sticky tubules out their anus when threatened Tubules are sticky or toxic, regenerate
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