Lecture 17: Animal Classification Phylum: Arthropods Arthropods are segmented coelomates with exoskeletons and jointed appendages This phylum is represented in nearly all habitats in the biosphere. Arthropods are regarded as the most successful animal phylum. The diversity التنوع and successوالنجتح of arthropods is largely due to three features: - body segmentation تعقل الجسم, - a hard exoskeleton جليج خارجي صلب, - and jointed appendages زوائد مفصلية.

Phylum: Arthropods 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 They have clawlike feeding appendages, chelicerae, crustaceans have jawlike mandiblesفكوك . Have sensory antennaeقرون استشعار and usually a pair of compound eyes أعين مركبةin addition to simple eyes. Arthropods have been grouped into the phylum Arthropoda.

1-Class Arachnidaطائفة العنكبيات These include scorpionsالعقارب , spidersالعناكب , ticksالقراد , and mitesالحلم . Nearly all ticks are blood-suckingماص للدماء parasites on the body surfaces of most animals. In most spiders, respirationالتنفس is carried out by book lungsالرئة الكتابية .

2-class Insectaطائفة الحشرات 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 Insects 750,000 + species insects described, but may be 30 million species undescribed. Many adaptations make insects one of the most successful terrestrial animals. Exoskeleton for water conservation Tracheal System for gas exchange Metamorphosis Many types of mouth parts Flight

رأس صدر بطن قرون استشعار عين مركبة Fig. 33.33

Specialized Mouthparts Modified mouthparts have allowed insects to diversify and take advantage of many different food sources. Modify generic structures for various food sources. Generalized Insect 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 hemolymphالدم by Malpighian tubulesأنابيب ملبيجي , outpockets of the digestive tract. Respiration is accomplished by a branched, chitin-lined tracheal systemالجهاز القصبي that carries O2 from the spiracles directly to the cells. The insect nervous system consists of a pair of ventral nerve cordsحبلين عصبيين بطنيين with several segmental ganglia.

Fig. 20.14

3 Kinds of Insect Metamorphosis Ametabolous Metamorphosis – only difference between larvae and adult are size; both are wingless. Silverfish, Order Thysanura. After Flight… Hemimetabolous 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

Adult emerges from case very different in body form – eclosion. 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. 20.24