Biology Chapter 33
Biology Chapter 33 BSC 120
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This 9 page Class Notes was uploaded by fwmartin on Friday March 4, 2016. The Class Notes belongs to BSC 120 at University of Alabama - Tuscaloosa taught by Dr. Martha Powell in Spring 2016. Since its upload, it has received 58 views. For similar materials see Honors Gen Biology II in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 03/04/16
Chapter 33: Invertebrates Invertebrates • Animals without a backbone • 95% of known animal species • All but one of the ~35 animal phyla. • Live in diverse habitats Important Phylum’s: • Phylum Porifera (sponges) o No true tissues o Hermaphadites o Sedentary (sessile) § Both fresh and salt water o Suspension feeders § Water flows through pores into the spongeoceol (central cavity) and then out through the osculum. *ceol means cavity Sponges are a community of cells. Two layers of cells with a gelantounous middle layer (mesohyl). • Cholanocytes line the interior of the sponge and have a collar of flagella that pull water in to capture food. • Amoebocytes are involved with digestion and structure. Make tough protein fibers called spongin and spicules (calcium carbonate or silicon) Sexual reproduction occurs by producing sperm that are carried by ocean currents to other sponges. The sperms settle into an egg, producing larvae that then flows outwards and grows to become a new sponge. Sponges create chemicals to protect themselves. AZT is an anti-AIDS anti-viral modeled after sponges. Nucleoside antiviral drug – inhibits replication of retrovirus Phylum Cnidaria o Sessile and floating diploblasts with radial symmetry o Have a Sac with one opening § gastrovascular cavity- both mouth and anus o Carnivores (a few are omnivores) o Tentacles capture prey and force it in o Simplest form of nerves- no brain, sensory cells located radially o Jellies (jelly fish), corals, hydras Can paralyze fish and then digest it alive. Jellies have body plan called medusa, which is really an upside down polyp. Both types have tentacles. • Tentacles are lined with Cnidocytes o Unique cells that function in defense and capture of prey o Have organelles called cnidae that evert o Ex. nematocysts- cnidae that sting § Other cnidae are very long sticky threads Hydrozoa: both polyp and medusa stages, some found in fresh water Scyphozoa: jelly fish (not a fish), polyp stage reduced, swimming medusa dominant form Anthozoa (“flower animals): sea anemones, corals exist as polyp only Lophotrochozoa (18 phylums) • This clade identified by molecular data • Some develop a lophophore (structure for feeding) [bryozoans = ectoprocta] • others pass through a trochophore larval stage • a few have neither feature • Includes the: flatworms (Platyhelminthes), rotifers, molluscs, and annelids (=earth worms) Phylum Platyhelminthes • Flat worms • Live in aquatic and moist terrestrial environments • Thin bodies, acoelomates – Shape enables all cells to exchange gas and eliminate waste • Most have gastrovascular cavity with one opening 3 Types: Turbellarians- most free living (not parasites), marine Ex. Planarians- very common • move using cilia • chemical sensitive eyespots • move away from toxins, too food • Basic centralized nervous system • Can learn, have memory • Can regenerate if cut in half any direction. Lots of medical research being done Trematodes- also called flukes, parasitic complex life cycles, alternating sexual and asexual stages, many have multiple hosts • Ex. Blood flukes (Schistosoma): o 200 million people infected world wide annually o schistosomiasis: chronic disease- pain, anemia, dysentery, cancer, death o lifecycle: § Mature flukes live in human bloodstream where they sexually reproduce § Fertilized eggs leave human host in feces § Eggs develop into ciliated larvae in water and then infect snails § Asexual reproduction in the snail produces another larva which then penetrates the skin of humans and enters the bloodstream. Cestodes: Tape worms - parasitic, mostly vertebrate (including human) hosts • scolex- anterior end with hooks and suction o hooks to intestinal lining o no gastrovascular cavity. It just absorbs nutrients from host • Posterior to scolex- long ribbon of units called proglottids o When mature, they contain thousands of eggs and they break off and exit host in feces. • Life Cycle o Infect feed or water for hosts, cow or pig, and then infect muscles and form cysts. o When humans eat meat, they consume the cysts. § If meat is fully cooked the cycsts will be destroyed. o After consuming the cyst, eggs hatch and then move into the intestines and lay eggs which exit body through in feces. Phylum Rotifera • Rotifer: “wheel bearer” - a crown of cilia that draws water into mouth • Smaller than many protists, yet much more complex • Alimentary canal- a full digestive tube with mouth and anus- not seen in flatworms or cnidarians • Pseudocoelum- filled with fluid, acts like internal skeleton • Can move around • Parthenogenisis- very different reproduction strategy • produce only females that produce more females from unfertilized eggs- asexual clones. • Under bad conditions: some species will produce males- make sperm that fertilize eggs and then die. • The zygotes are resistant spores, when the environment is better, they germinate as all female. Phylum Mollusca o Soft bodied and mostly marine o Most protected by a calcium carbonate shell o Examples: oysters, clams, snails, slugs, octopuses, squids o Those without shells had ancestors with them but in exchange for loss of shell gain mobility and size o All are coelomates, o Most have an open circulatory system o with a heart o Life cycles usually includes a ciliated larval stage called a trochophore o Most have separate sexes o All have the same general body plan: o Visceral mass: contains most internal organs, including gonads o Muscular foot: movement o Mantle: tissue that drapes over the visceral mass The mantle… – Secretes a shell if one is present – some have a water filled chamber (mantle cavity) • Contains the gills, anus and excretory pores • Many also have a radula- a belt of backward curved teeth that slides back and forth and scopes food Gastropods: includes most molluscs species – Most are marine, but also garden snails, freshwater snails, and slugs – Most have separate sexes, some are hermaphroditic – Most have a single, spiraled shell o – As a gastropod develops, its visceral mass rotates 180 (torsion). – Mantle cavity is above its head – Anus on the anterior Bivalves: clams, oysters, scallops, mussels - shell divided in 2 halves - powerful abductor muscles draw the halves tightly together for protection - suspension eaters, sedentary lives - cilium to ring food in - SOME CAN MOVE ephalopods: octopuses, squids, nautilus n active predators n have a complex brain n only molluscs with a closed circulatory system • only one living shelled species- the nautilus PHYLUM ANNEELIDA • Body plan looks like a set of fused rings • Aquatic and in moist soil • Coelomates – complete digestive system • Closed circulatory system • Lack respiratory systems – Lots of blood vessels in skin • Function in gas exchange Phylum Annelida Includes 3 major groups: Leeches: most aquatic, some in moist soil • Free living and parasitic • Parasites suck blood • after certain injuries- such as reattach body parts • VAMPIRES OF THE worms • Salvia contains an anesthetic and anticoagulant Errantians: most marine, each segment has paddle like structures for movement • Also functions as gills • parapodia Oligochaetes: earthworms and relatives • Sparse bristles of chitin- chaete • How are they able to move in the soil? • Eat through soil, – leaves it aerated – waste improves soil texture – castings are highly prized by gardeners Ecdysozoans The other protostomes • covered by a tough coat called a cuticle • The cuticle is shed or molted through a process called ecdysis • The two largest phyla are nematodes and arthropods Phylum Nematoda Roundworms: Non-segmented body, pseudocoelomates • Lack a circulatory system – Fluid in pseudocoelom transports nutrients • Have an alimentary canal (=complete digestive system) • Very diverse, free living and parasitic • Sheds the cuticle as it grows and makes a new one • Most species have separate sexes Nematode Research: C. elegans • Widely used in developmental research – Study of aging and neuromuscular diseases – Ex. Parkinson’s disease – Every neuron is mapped – Can easily control genes – Called a “model organism” Parasitic nematodes: – Humans host at least 50 parasitic species Ex. Pinworms, hookworms – Trichonella spiralis : (will be on test)causes trichinosis • Acquired by eating undercooked pork infected by juveniles encysted in muscle tissue • If undercooked stay alive in cyst • Move through lymphatic system into muscles and cause enormous pain. • Is a Roundworm Hookworms can be gotten by walking barefoot. They can live in dirt and burrow through the skin. -Treatment is using anti-helemants to kill the worms. -Elephantiasis -Guinea Worm -heartworms are transmitted to dogs by mosquitoes can protect dogs with regular dosages of medication -also attack plants and feed on root. The damage invites bacterial infection. -ex. Root Knot Nematodes Phylum Arthropods • Most successful animal phyla • More than 1 million species described • 2/3 of all known animal species – About 10 individuals • General characteristics: – Segmented coelomates – Jointed appendages – Exoskeleton made of protein and chitin • Exoskeleton completely covers animal • Thick and hard over some parts • Rigid exoskeleton protects, provides points of attachment for muscles • Thin and flexible over joints • Animal cannot grow without shedding and producing a larger version • Energetically expensive – Well developed sensory organs – Eyes, olfactory receptors (smell), antennae – Open circulatory system • a heart pushes fluid through tiny vessels into open spaces called sinuses • Fluid drains into pores that have valves and from there to the heart – Variety of organs for gas exchange – Separate males and females There are four major arthropod lineages: cheliceriforms, myriapods, insects, and crustaceans Cheliceriforms : • all have claw like feeding appendages called chelicerae, • no antennae, • simple eyes • Body has 1-2 main parts – Anterior cephalothorax – Posterior abdomen – Horseshoe crabs- living fossils, little change for millions of years – most are arachnids: scorpions, spiders, ticks and mites Spider Physiology • fang like chelicerae- that secrete poison to kill prey – As they chew with the chelicera, digestive juices are secreted, food softens and the spider sucks up the liquid food • book lungs- an internal chamber with stacked tissue that most spiders have. – high surface area to exchange gas • webs of silk - protein made in spinnerets – Each species has a characteristic web pattern • Inherited complex behavior • Incredibly strong: tinsel strength is 5x stronger than steel per weight M yriapods • All terrestrial, three pairs of modified appendages for mouth parts – Includes jaw like mandibles • Millipedes: large number of legs (<1000) – Each segment has 2 pairs of legs – Herbivores, can’t hurt you • Centipedes: one pair of legs per segment – Poisonous claws on front segment • Paralyze prey – Are carnivores and go after any type of animal – Aggressive and will go after humans and will hurt Insects More species than any other arthropod group How has adaptation contributed to insect success? Development of flight – Escaping predators, finding food and mates – Many have 1-2 sets of wings – Wings are not modified appendages, therefore winged insects still have walking legs (Not true for flying vertebrates) Explosion of types of mouth parts – diversification and explosion of gymnosperm populations- carboniferous period – co-evolution with gymnosperms for more access to food Other adaptations of insects: – Tracheal tubes- chitin lined tubes that infiltrate the body – Function in gas exchange – Do not open to the outside via the pharynx – Have pores called spiracles – Well developed compound eyes – Specialized brain – Nitrogen waste removal system – metamorphosis – Incomplete metamorphosis: Ex. grasshoppers – Nymphs (young) look like adults – Smaller, different body proportions, lack wings – Go through a series of molts until the final stage is reached – Complete metamorphosis: Ex. Butterfly – Larval stages specialized for eating and growing – Looks completely different from adult stage – Adult stage specialized for dispersal and reproduction – Reproduction: sexual with separate male and female individuals- many mate once in a lifetime Crustaceans Mostly aquatic: lobsters, crayfish, krill • Branched, specialized appendages – Only arthropods with 2 pairs of antennae • Very good at sensing their surroundings – 3 or more are mouth parts – Unlike insects, they have appendages on the thorax and the abdomen (insects- thorax only) • Most go through one or more larval stages Ex. • Isopods: wood lice, pill bugs- terrestrial – 7 pairs of legs • Decapods: lobsters, crayfish, crabs, shrimp • Copepods: tiny plankton, krill – Food for whales • Barnacles: sessile, larvae look like other crustaceans – Covered in a protective armor Deuterostomia Phylum Echinodermata • phylum Echinodermata, may seem to have little in common with phylum Chordata, which includes the vertebrates • Shared characteristics define deuterostomes (Chordates and Echinoderms) – Radial cleavage – Formation of the mouth at the end of the embryo opposite the blastopore • Invertebrate Deuterostomes • Slow moving or sessile marine animals • Thin skin covers endoskeleton • Water vascular system- unique to echinoderms – Network of hydraulic canals – Branch in to tube feet • Function in movement, feeding and gas exchange • Separate sexes, external fertilization • In Adults: External and many internal parts radiate from the center – Usually 5 spokes – Adults are Not perfectly radial- certain organs off to one side • Larvae have bilateral symmetry • NOTE: radial anatomy is a secondary adaptation
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