Biology II Lab Final Phylum Arthropoda Part 2 Classification Subphylum Myriapoda 1 Class Chilopoda Centipedes flat one pair of legs per segment longer legs are usually larger than millipedes Centipedes are active predators They eat roaches and earthworms remember the video about the centipede capturing and eating a flying BAT Have 2 tagmata head and trunk 2 Class Diplopoda Milipedes round two pairs of legs per segment very short and tiny bristle like legs more legs than centipedes Milipedes are usually herbivores and detritovores Some millipedes secrete hydrogen cyanide from special defensive glands They also have 2 tagmata head and trunk Subphylum Hexapoda 1 Class Insecta most diverse group of arthropods Slubclass Pterygota with wings Division Exopterygota wings through hemimetabolous o Order Odonata tooth jawed Dragonflies Damselflies o Order Orthoptera straight winged Grasshoppers Mantids Crickets Roaches o Order Homoptera whole winged Cicadas Leaf Hoppers Aphids Mouthparts modified as proboscis to suck sap o Order Hemiptera half winged True bugs water bugs bed bugs assassin bugs etc base or proximal half of first wing is hardened o Order Isoptera similar wings Termites exhibit eusociality Division Endopterygota wings through holometabolous o Order Diptera two wings Flies mosquitoes have only 1 pair of flying wings 2nd pair of wings are reduced to halteres and used in balance as stabilizers o Order Lepidoptera scaled wings butterflies moth Butterflies wings folded raised at rest thin antennae colorful and chrysalis pupate Moths wings open flat at rest thicker antennae mostly nocturnal and drab pupate in silk cocoon o Order Hymenoptera married wings Bees Wasps Moths exhibit eusociality o Order Coleoptera sheath wings Beetles lady bugs greatest number of insect species top pair of wings is modified into an armor like covering called an elytra Organization Organ level Embryonic Development Triploblastic Eucoelomate Protostomes Symmetry Bilateral metameric segmented tagmosis the process of specialized segments Skeleton Support Cuticle forms a well developed exoskeleton chitinous or calcified calcified is usually for marine arthropods growth is by ecdysis molting Sensory Nervous nervous system with double nerve chain of ventral ganglia Movement Locomotion apodemes for muscle attachment well developed antagonistic muscles Digestion Complete digestive tract Excretory Osmoregulation malpighian tubules at the end of the hindgut insects resorb water Feeding along with K Na ions Malpighian tubules allow insects to conserve H2O withstand terrestrial environments Ion pumping of Na allows for the osmotic reabsorption of water and NH3 Circulation Open circulatory system with blood vessels opening up to a hemocoel blood empties into sinuses to bathe organs and tissues and returns directly from the hemocoel to the heart through ostia Respiration via gills tracheaa book lungs or book gills Reproduction Most are dioecious internal fertilization terrestial sexual canabalism Class Insecta Insects are mostly terrestrial conserve H2O by 1 waxy waterproof cuticle exoskeleton 2 valved spiracles 3 Malpighian tubules conserve H20 Some insects have aquatic larval stages that respire through gills Insects are so diverse because they have body plans that are capable of great modification which allows for much adaptive radiation There are numerous species with adaptations to many different environments and niches One major adaption is flight Flight enables organism to disperse to new habitats move to better food sources and escape bad conditions Why Insects are so Diverse small size can exploit more niches short generation time recall natural selection criteria metamorphosis use 1 niche life stages don t compete winged adults dispersal adaptations to terrestrial environments e g waterproof cuticle tracheal system etc sophisticated sensory system sophisticated behavior and communication co evolutionary interactions with other organisms e g plant mutualisms and parasitism Insects are divided into 3 tagmata head thorax and abdomen The head is comprised of 6 segments the thorax 3 and the abdomen 11 An insects complete gut runs through its entire body The foregut in the head is comprised of ectoderm and is involved in mechanical digestion The midgut in the thorax is comprised of endoderm tissue and is responsible for chemical digestion and the absorption of nutrients The hindgut in the abdomen is comprised of ectoderm and is responsible for water reabsorption Since the foregut and the hindgut are made of ectoderm tissues they undergo ecdysis when the insect molts Insects have one pair of antennae Insects use tracheal tubes open to the outside by surface valved openings called spiracles for respiration These openings are valved to prevent insects from drying out Flight Some insects have both direct and indirect wing muscles Direc t muscles Blue pull the wings down o Indirec t muscles Purple pull body wall down wings get uplifted by default Some insects have ONLY indirect flight muscles e g Diptera Hymenoptera the wings are moved by altering the shape of the thoracic body wall Indirect muscles contract to pull body wall down wings get uplifted When relaxed body wall moves up wings move down o o Modes of Development Primitive Insects Develop via ametabolous They do not undergo metamorphosis The larvae look exactly like the adult As larvae progress through their life cycle they only increase in size These primitive insects are wingless and belong to the subclass Apterygota o Example Springtails Order Collembola and Silverfish Order Thysanura o The next two types of insect development are found in the subclass Pterygota insects with wings These insects develop from a growing and molting larva lymph to a non molting sexually reproducing adult with wings These insects develop their wings through two different modes of development 1 Hemimetabolous or 2 Holometabolous o Hemimetabolous outside Insects that develop this way are categorized in the Exopterygota Division Development incomplete metamorphosis Insects develop wing buds Nymphs undergo several molts called instars Once the insect becomes an adult and the wings are produced there is no further moltin Grasshopper life cycle egg molting nymphal instars adult o Holometabolous Development complete metamorphosis insects develop wing buds inside These insects are catorgorized in the Endopterygota Division 88 of all insects Wormlike larva grow and molt in instar stages
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