Phylum: Arthropods Arthropods are segmented coelomates with exoskeletons and jointed appendages...

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Transcript of Phylum: Arthropods Arthropods are segmented coelomates with exoskeletons and jointed appendages...

  • Phylum: ArthropodsArthropods are segmented coelomates with exoskeletons and jointed appendagesThis phylum is represented in nearly all habitats in the biosphere.Arthropods are regarded as the most successful animal phylum.The diversity and success of arthropods is largely due to three features: - body segmentation , - a hard exoskeleton , - and jointed appendages .Lecture 17: Animal Classification

  • The body of an arthropod is completely covered by the cuticle, an exoskeleton constructed from layers of protein and chitin.The exoskeleton of arthropods is strong and relatively impermeable to water.Arthropods have well-developed sense organs, including eyes for vision, olfactory receptors for smell, and antennae for touch and smell.Arthropods have an open circulatory system in which hemolymph fluid is propelled by a heart through short arteries into sinuses (the hemocoel) surrounding tissues and organs.Arthropods have evolved a variety of specialized organs for gas exchange.Phylum: Arthropods

  • Phylum: ArthropodsThey have clawlike feeding appendages, chelicerae, crustaceans have jawlike mandibles .Have sensory antennae and usually a pair of compound eyes in addition to simple eyes.Arthropods have been grouped into the phylum Arthropoda.

  • 1-Class Arachnida

    These include scorpions , spiders , ticks , and mites .Nearly all ticks are blood-sucking parasites on the body surfaces of most animals.In most spiders, respiration is carried out by book lungs .

  • 2-class Insecta They live in almost every terrestrial habitat and in fresh water, and flying insects fill the air.The study of insect, (Entomology) is a vast field with many subspecialties, including physiology, ecology, and taxonomy.etc.Class Insecta is divided into about 26 orders. Many insects have one or two pairs of wings that emerge from the dorsal side of the thorax.

  • The Insects750,000 + species insects described, but may be 30 million species undescribed.Many adaptations make insects one of the most successful terrestrial animals.Exoskeleton for water conservationTracheal System for gas exchangeMetamorphosisMany types of mouth partsFlight

  • Fig. 33.33

  • Modified mouthparts have allowed insects to diversify and take advantage of many different food sources.Modify generic structures for various food sources.Generalized Insect MouthpartsSpecialized Mouthparts

  • The internal anatomy of an insect includes several complex organ systems.In the complete digestive system, there are regionally specialized organs with discrete functions.Metabolic wastes are removed from the hemolymph by Malpighian tubules , outpockets of the digestive tract.Respiration is accomplished by a branched, chitin-lined tracheal system that carries O2 from the spiracles directly to the cells.The insect nervous system consists of a pair of ventral nerve cords with several segmental ganglia.

  • 3 Kinds of Insect MetamorphosisAmetabolous Metamorphosis only difference between larvae and adult are size; both are wingless. Silverfish, Order Thysanura.After FlightHemimetabolous Metamorphosis develop from egg to adult has several stages (instars) with smaller versions of adults called nymphs. Immature nymphs have no wings or genitalia until adult.

  • Incomplete or Hemimetabolous Metamorphosis

  • Holometabolous Metamorphosis after hatching from egg, immatures are called larvae (very different body form than adult). After several instars, the last larval molt forms a pupa undergoes radical body form change.Protective case may enclose pupal stage:Moths use silk to make a cocoon.Butterflies use the larval exoskeleton to make a chrysalis.Adult emerges from case very different in body form eclosion.

  • Complete or Holometabolous Metamorphosis

  • You Decide?

    *Fig. 20.14*Fig. 20.24