Zoology Arthropod Unit

Zoology Arthropod UnitChapter 18 ArthropodsChapter 19 CrustaceansChap.20 Terrestrial ArthropodsChapter 18 Objectives1.Identify characteristics distinguishing phylum Arthropoda

2.Discuss adaptations characteristic of the phylum Arthropoda with regard to Body form, morphology & embryonic developmentFeeding and digestionExcretionMovement/locomotionReproductionSensory/Motor responseAny special features unique to the phylum

3.Identify derived characteristics that contribute to the phylogeny of phylum ArthropodaArthropod Diversity

Characteristics of ArthropodsArthro = jointPoda = footArthropods are named for their jointed appendagesAll arthropods have an exoskeleton made of an amino sugar called Chitin

Arthropod AppendagesAppendages in arthropods are modified for a number of functions:Walking legsMouth partsAntennaeClawsOrgans for matingHolding eggs

Modified Appendages

SegmentationSegmentation is an ancestral characteristic that carries over from the AnnelidsNote the similarity of the insect caterpillar to polychaete worms

Rick Takahashi on Segmentation

Fusion of Segments forming Body Regions

These animals have segements in the head and thorax region fused togetherSegmentation

These animals have little differentiation between body segmentsThe millipede below has segments fused in pairs, resulting in 2 pair of legs per segmentExoskeleton: AdvantagesThe exoskeleton provides rigid support and strong points for muscle attachmentThe exoskeleton also forms a protective shell

Exoskeleton: DisadvantagesThe exoskeleton prevents drying out, but also prevents respiration through the skinThe exoskeleton provides rigid support, but prevents growth requiring molting

Other Arthropod CharacteristicsStriated muscle associated with the exoskeleton, and smooth muscle associated with the gutReduced body cavity, filled with blood, forming an open circulatory systemSpecialized excretory glands (coxal, antennal or maxillary glands; malpighian tubules)Specialized respiratory organs (gills, tracheae, book lungs)Dorsal brain with fused ventral nerve cords

Nervous SystemLike the annelids, the arthropods have a dorsal brain, fused ventral nerve cords, and paired nerve branches that encircle the pharynx

Excretory System

The exoskeleton prevents the use of the skin as an excretory organ. In insects, salts and metabolic wastes are removed by Malpighian TubulesThe malpighian tubules extend into the hemocoel, extract waste materials and funnel them into the digestive tract for removalRespiratory AdaptationsTracheal system in insects bring air directly to tissuesBook Lungs in Arachnids : a series of flattened tissues to create surfaces for gas exchangeGills in Crustaceans are extensions of the walking legs

Arthropod Phylogeny

Arthropod PhylogenySubphylum TrilobitaExtremely common in the early Paleozoic era, trilobites are extinct todaySubphylum ChelicerataClass Merostomata includes Horseshoe CrabsClass Pycnogonida includes Sea SpidersClass Arachnida includes spiders, scorpions, ticks and mitesSubphylum CrustaceaLobsters, crabs, shrimp, crayfish and others less familiarSubphylum UniramiaMyriapods (Centipedes and millipedes) and InsectsTrilobites

Chelicerates: Arachnids

Chelicerates: Scorpions

Chelicerates: Ticks and Mites

Crustaceans

Uniramia: Myriapods

Centipedes have 1 pair of legs per segmentMillipedes have 2 pair of legs per segmentUniramia: Insects

Chapter 19 Objectives4.Distinguish Crustaceans from other arthropods

5.Perform a dissection of the crayfish, a representative crustacean.

6.Identify internal and external anatomical features of the crayfishChapter 20 Objectives7.Compare and contrast Chilopods, Diplopods, and Insects

8.Discuss adaptations for gas exchange in a terrestrial environment as displayed in the insects

9.Discuss adaptations for excretion of metabolic waste as displayed in the insects

10.Discuss the process of metamorphosis in insects.

Chapter 20 Objectives10.Discuss the process of metamorphosis in insects.

11.Distinguish between complete and incomplete metamorphosis

12.Perform a dissection of the grasshopper, a representative insect

13.Identify internal and external anatomical features of the grasshopper