3 Alternate taxonomy: 4 major lineages Trilobita(trilobites –extinct)Chelicerata(jaw-like chelicerae, no antennae, simple eyes)Alternate taxonomy:4 major lineagesPhylum:Uniramia(jaw-likemandibles, 1pair antennae,complex eyes)CrustaceaSuper-PhylumArthropoda(jaw-like mandibles, 2 pairs antennae,(Crabs, lobsters,crayfish, shrimps)TaditionalTaxonomy:PhylumClass:Arachnida(spiders, scorpions,mites)Diplopoda(millipedes)Chilopoda(centipedes)Insecta(insects)CrustaceaArthropoda
4 Diplopoda Millipedes; 2 pairs of walking legs on each segment. Feed on decaying leaves and plant matter.Possibly among the earliest land animals.Fig a
5 Chilopoda Centipedes Terrestrial carnivores. Head has a pair of antennae and 3 pairs of appendages modified as mouthparts including jaw-like mandibles1 pair of walking legs per trunk segmentVenom in claws of anterior trunk segments
6 Insecta = hexapoda Greatest species diversity among animals. ~ 26 orders.All terrestrial habitats (even beetles in moss beds in Antarctica); some freshwater, few marine, and lots flying insects.
7 - evolution of wing/flight escape Oldest insect fossil – Devonian (~400 mya)Reasons for insect diversity:- evolution of wing/flight escapepredators, dispersal to new habitats, etc.- diversification of mouth parts forfeeding on plants;- plants and insects adaptive radiationseemed to parallel each other beginning about 100 mya and continued until about 50 mya. Insects probably played a major role in (caused ?) the angiosperm radiation because of specific role as pollinators.
8 Major Orders of Insects Order # spp Examples Large impact on humans
10 Insect digestion and excretion Digestive system – complete; specialized organs with discrete functions.Malpighian tubules – remove nitrogenous waste from hemolymph in form of uric acid; reabsorption of H2O by intestinal hind gut.
11 Respiration by a chitin-lined tracheal system blue . Insect respirationRespiration by a chitin-lined tracheal system blueair is carried from spiracles directly to the cells.
12 Insect Reproduction Separate sexes. Metamorphosis is central to insect development.Incomplete metamorphosis: eg. grasshoppers, cockroach; young resemble smaller adults.Complete metamorphosis: eg. butterfly, flies; larval stages look different from adults and food source different. Morphology changes completely during pupal stage and emerge as adults.Fig
13 Control of Moulting and Metamorphosis Role of Ecdysone and Juvenile Hormone.Overhead
14 ~ 40,000 species; almost all aquatic. Crustacea~ 40,000 species; almost all aquatic.A few terrestrial or semi-terrestrial.Crustaceans include lobsters, crabs, crayfish, shrimp, and barnacles.Appendages specialized on segments:- Claws, mouth parts,walking legs,swimming legs.- Can regeneratelost appendagesduring molting.Fig
17 Crustacean physiology Respiration:- small species, across cuticle.- large species: across gills.Open circulatory systemExcretion: nitrogenous wastes mostly NH3, by diffusion from modified coelomoducts called antennal or maxillary glands.Reproduction: mostly separate sexes (barnacles are hemaphrodite)Males use a specialized pair of appendages to transfer sperm to the female’s reproductive pore.Most aquatic species have several larval stages.
18 Major Crustacean Orders Isopods - ~ 10,000 species,largest groups of crustaceans.Copepods - small; importantin aquatic ecosystems;eat phytoplantons; eatenby large animals (fish).Decapods – 10 walking legs (5 pairs);lobsters, crabs, crayfish, shrimps. 3 additional anteriorpairs of appendages form mouth parts.- cephalothorax covered by carapace.
19 Mysidiacea: - mysid shrimps. Eg Mysidiacea: - mysid shrimps. Eg. Krill, planktonic, reaching about 3 cm long.major food source for whales;also used for agricultural fertilizer.Cirripedia: - barnaclessessile crustacean on intertidal rocks and whales.parts of cuticle hardened by calcium carbonate.Filter feed by extending long thoracic appendages.
21 Echinoderm introduction Echinoderms are invertebrates, but sister taxon to Phylum Chordata, which includes the vertebrates.Have deuterostome embryo characteristics: radial cleavage, coelom develops from archenteron, and anus formed from blastopore.This classification based on developmental features supported by molecular systematics.
22 Echinoderm characteristics Sessile or slow-moving.The internal and external parts of the animal radiate from the center, often as 5 spokes.A thin skin covers an endoskeleton of calcareous plates.Unique to echinoderms is the water vascular system, a network of hydraulic canals branching into extensions called tube feet – function in locomotion, feeding, and gas exchange.Separate sexes– fertilization external.Larvae – bilateral symmetry.Adult radial appearance - result of asecondary adaptation to a sessilelifestyle.Sea urchin larva(bilateral symmetry)
23 Echinoderm diversity ~7,000 species, all marine. 6 classes: Asteroidea (sea stars)Ophiuroidea (brittle stars)Echinoidea (sea urchins and sand dollars)Crinoidea (sea lilies and feather stars)Holothuroidea (sea cucumbers)Concentricycloidea (sea daisies)
24 The undersides of the arms have rows of tube feet. Asteroidea - Sea stars; five arms (sometimes more) radiating from a central disk.The undersides of the arms have rows of tube feet.Each can act like a suction disk that is controlled by hydraulic and muscular action.Predators; scavenger eaters.Sea stars feeding on AntarcticWeddell seal pup carcassFig
25 Ophiuroidea - Brittle stars. distinct central disk; long, flexible arms.Tube feet lack suckers.They move by serpentine lashing of their arms.Some species are suspension-feeders and others are scavengers or predators.Fig cAntarctic brittle starAstrotoma agassizii
26 Echinoidea - Sea urchins and sand dollars No arms; but have 5 rows of tube feet for locomotion.Sea urchins also move by pivoting their long spines.The mouth of urchin ringed by complex jawlike structures adapted for eating seaweed and other foods.Urchins roughly - Sand dollars, flattened spherical disk.Fig d
27 Crinoidea Sea lilies; attached to the substratum by stalks. Feather stars; crawl using their long, flexible arms.Both use arms for suspension-feeding.Crinoids show very conservative evolution.Fossilized sea lilies from 500 million years ago could pass for modern members of the class.Sea lilyFeathery star on sponge
28 Holothuroidea - Sea cucumbers. Look different from other echinoderms.No spines,Little or no hard endoskeleton.Oral-aboral axis is elongated.BUT – have 5 rows of tube feet.Some tube feet around the mouth function as feeding tentacles for suspension-feeding or deposit feedingFig f
33 Phylum Chordata Subphyla Urochordata and Cephalochordata: no cranium, no backbone “invertebrates”Subphylum Craniata (text calls it a Clade) :Class Myxini – Hagfish; elemental cranium, no backbone.Class Cephalaspidomorphi – Lamprey; cranium, partial backbone.Subplylum Vertebrata – fused cranium; complete backbone.
34 4 unifying anatomical features of chordates NotochordDorsal hollow nerve cordPharyngeal slitsMuscular, postanal tail.Fig. 34.2
35 3. Pharyngeal gill slits and arches. - connect the pharynx to the outside.- filter device for suspension-feeding in invertebrate chordates.- modified in higher vertebrates for gas exchange,jaw support, hearing.4. Muscular post-anal tail- contains chevron-shapedmuscle blocks.- propulsive force inaquatic species.Early gill arch structures in human embryo
36 Urochordata – tunicates, ascidians (sea squirts) Mostly sessile marine animals, some pelagic (salps). Some colonial, others solitary.tunicatetunicatesFilter feeders
37 Only pharyngeal slits obvious in adult urochordate. All chordate characteristics evident in larval forms.Tunicate “tadpole” larvaFig. 34.3c
38 Cephalochordata – lancelets or amphioxus Closely resemble the idealized chordate.The notochord, dorsal nerve cord, numerous gill slits, and postanal tail, all present in adult.Filter feeder
39 Evolutionary relationships Molecular evidence: cephalochordates are closest relatives to vertebrates and urochordates are the next closest.The evolution of vertebrates from invertebrates probably occurred in 2 stages:-- 1st: an ancestral cephalochordate evolved from an organism resembling a modern urochordate larva; paedogenesis - the precocious development of sexual maturity in a larva (the adult lancelet resembles a well developed tunicate larva).-- 2nd: vertebrate evolved from a cephalochordate. Fossil evidence in the early Cambrium (535 mya) show intermediate fossil forms.