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Arthropods Jessica Corley Andrew Lightfoot Johnny Chen.

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1 Arthropods Jessica Corley Andrew Lightfoot Johnny Chen

2 General Arthropod Terms  Cuticle: The exoskeleton of an arthropod, consisting of protein and chitin that are variously modified for function  Exoskeleton: A hard encasement on the surface of an animal that provides protection  Molting: The process in which the exoskeleton is shed at intervals to allow growth by the creation of a larger exoskeleton  Book Lungs: Organs of gas exchange in spiders, consisting of stacked plates contained in an internal chamber A cricket undergoing molting

3 General Terms (Cont..) Open Circulatory System: An arrangement of internal transport in which blood bathes the organs directly. There is no distinction between blood and intestinal fluid Chelicerae: Pointed appendages which are used to grasp food; which are used to grasp food; some can contain venom glands some can contain venom glands Mandibles: Pair of mouthparts used for eating that can actually chew food unlike chelicerae Antennae: Pair of sensory organs joined at the base, functions can vary from organism to organism, including smelling, tasting, and sensing vibrations (sort of like hearing).

4 General Terms (Cont……….)  Compound Eyes: Eyes of an arthropod that consist of several ommatidia, tiny independent photoreception units  Malpighian tubules: Excretory organs that remove metabolic wastes from the Arthropods   Complete Metamorphosis: Arthropods with a larval stage that is made to eat and grow. These arthropods look completely different from their adult forms.   Incomplete Metamorphosis: Arthropods that resemble adults during the larval stages. With each successive molting, the arthropod becomes an adult   Tracheal System: Responsible for gas exchange in arthropods; consists of branched, chitin-lined tubes that carry oxygen directly to the cells   Spiracles: Pores that open to the outside of the body that open and close to regulate air flow and reduce water loss

5 Antennae Chelicerae Compound eye Mandible Exoskeleton / Cuticle Segmented Legs 1 2 3 4 5 6 Dorsal View of Lobster

6 Classes Arachnida Body has one or two main part, six pairs of appendages (chelicerae, pedipalps, and 4 pairs of legs) terrestrial Spiders,scorpions, ticks, mites ticks, mites Diplopoda Body with distinct head bearing antennae and mouthparts, segmented body with 2 pairs of legs per segment terrestrial, herbivorous Millipedes Chilopoda Body with distinct head with antennae and 3 pairs of mouthparts, first body segment has poison claws, following segments have 2 legs, terr., carnivore Centipedes Insecta Body divided into head, thorax, and abdomen, antennae, mouthparts modified to chew, suck, or lap, 2 pairs of wings, 3 sets of legs, most terr. Insects Crustacea Body divided into two or three parts, antennae, chewing mouthparts, 3 or more pairs of legs, most marine Crabs, lobsters, Crayfish,shrimp

7 A Few Orders of Insects Coleoptera Two Pairs of wings, armored exoskeleton, biting and chewing mouthparts, complete metamorphosis Beetles Diptera One pair of wings and halteres (balancing organs); sucking, piercing, or lapping mouthparts, complete meta. Flies,Mosquitoes Hymenoptera Two pairs of membranous wings; head mobile; chewing of sucking mouthparts; posterior stinging organ on females; complete metamorphosis; many species social Ants,Bees,Wasps Lepidoptera 2 pairs of wings with tiny scales; long, coiled tongue for sucking; complete metamorphosis Butterflies,moths Orthoptera 2 pairs of wings; biting and chewing mouthparts; incomplete metamorphosis Crickets,Roaches,Grasshoppersmantids

8 General Arthropod Information Bilateral symmetry 3 Germ Layers, and a real coelem The more dominant body cavity is called hemocoel. This is filled with hemolymph, a mixture of blood, lymph, and tissue fluid Open circulatory system (the cause of a hemocoel) Protostomes Lobster demonstrating bilateral symmetry

9 Movement Arthropods are sessile Arthropods are characterized by their jointed appendages. These are how they move. In some cases, arthropods use wings for movement.

10 Development Most insects develop starting as eggs. The eggs hatch in larvae which is the equivalent of a “baby.” Larvae transition into the adult stage through metamorphosis—sometimes called molting—and become sexual active. A prime example of this is the life cycle of butterflies which start as eggs, hatch into caterpillars, and then go through a stage of dormancy (known as Chrysalis) that eventually results in the butterfly.

11 Reproduction/ Life Cycle Arthropods reproduce sexually. Male arthropods transfer sperm through sealed packets called spermatophores. The male can either lay it on the ground so that female arthropods will pick them up or the male can deposit the packet directly into the female. After the eggs become fertilized, they can hatch from periods ranging from a few days to years. Most species of arthropods will lay the eggs in an external environment but some species will hatch them internally. The life cycle of an arthropod can range from a few weeks to many years, depending the species.

12 Specialized Tissues/Functions The exoskeleton of the Arthropod is built so that the hard section become much thinner at joints. Respiratory structures are specialized to adapt to the environment of the Arthropod. For instance, lobsters have developed gills that allow them to survive underwater. Land-based Arthropods develop air-conducting tubes known as tracheas. In order to adapt to the environment, Arthropods have specialized sensory structures. Compound eyes are a prime example of this occurrence. In order to adapt to the environment, Arthropods have specialized sensory structures. Compound eyes are a prime example of this occurrence.

13 Interesting, but Unnecessary Facts  Arthropods account for roughly 2/3 of all known organisms. The estimated number of Arthropods is around 1 billion billion (10 18 )  Because both the Phylum Arthropod and Phylum Annelids are segmented, it was though for many years that both shared a common ancestor. One of the prevalent hypotheses was that Arthropods descended from Onychophorans (Walking worms). However, recent study suggest that this is not the case and that they share common characteristics of bilaterians.

14 Cicada molting *The process is sped up


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