Classification of phylum arthropoda | general organization | economic importance скачать в хорошем качестве

Classification of phylum arthropoda | general organization | economic importance

Aslam o alikum I am Hassam ur Rahman and I am teaching Fsc biology since 2014 .I am always trying to improve myself and provide best lecture to students.i am taking content for the lecture from authentic and relevant sources but human errors are possible . you are requested to please highlight the mistakes.My lectures are equally reliable for Fsc and mdcat students #visiblescience #mdcatbiology #alevelbiology #neetbiology #fscbiology My personal channel, I am sure it will change your life and very beneficial for you https://youtube.com/@hassamurRahman?f... My Facebook page link https://www.facebook.com/hassam.urahm... This lecture is about Classiication Phylum Arthropoda is a large group consisting of great variety among them. Some of its important classes are as follows. 1. Class Crustacea : These arthropods are aquatic and have gills for respiration. On the dorsal side of the cephalothorax the exoskeleton is in the fofm of carapace. In the exoskeleton deposition of salts in addition to chitin makes it more irm. The appendages are modiied for capturing food, walking, swimming, respiration and reproduction. Coelom is reduced and is in the form of hemocoel. Head has two pairs of antennal appendages, one pair of mandibles (jaws) and two pairs of maxillae. Sexes are mostly separate e.g. Daphnia, Cyclops, Crabs, lobsters, prawn, wood louse etc. (Fig. 10.8)2. Class Insecta : This is the largest group not only of Arthropoda but of all the animal kingdom and has great variety. Insects are found everywhere, many show social behaviour. The body in, insects has three distinct regions head, thorax and abdomen. There are a pair of antennae and compound eyes on the head. The head is usually vertical to the body and jaws are ventrally placed. The thorax has three segments in which are present three pairs of jointed legs and in many one or two pairs of wings. Abdomen has varying number of segments. Brain is formed of fused ganglia and double nerve cord is ventral. Sexes are separate and animals are oviparous. Metamorphosis takes place during development e.g. dragonly mosquito, butterlies, moths, wasps, and beetles etc. (Fig. 10.9). Fig. 10.9 Insects 3. Class Arachnida : Body has the anterior segments that are fused to form a combined cephalothorax, with a pair of appendages called chelicerae with claws, two pairs as pedipalps and four pairs of legs. There are no antennae and no true jaws. Abdomen may be segmented or unsegmented with or without appendages. Respiration is by gills or special structures called book lungs, excretion is by the Malpighian tubules. Eyes simple, sexes are separate. They are oviparous (lay eggs). No true metamorphosis e.g. scorpions, spiders, mites and ticks4. Class Myriapoda: The body is divided into large number of segments each having a pair of legs. A pair of antennae and a pair of eyes are present on head e.g. centipedes and millipedes. General organization of Arthropods Arthropods have characteristics of higher forms such as bilateral symmetry, triploblastic, coelomic cavity and organ systems and have reached the peak of invertebrate evolution. Two of their main achievements are the chitinous exoskeleton and locomotary mechanism. These animals can walk, swim and ly. The jointed appendages (limbs) have been modiied or diversiied for various uses in the diferent sub-groups of Arthropoda. Chitin is non-living, non-cellular and is secreted by the under lying epidermis. It is made of polysaccharide.On the outer side of chitin,there is a waxy layer. In some Arthropods and in certain parts in other Arthropods chitin is soft and lexible, in others it is hard. In general, it is for protection but it also serves as lever for the movement of muscles of jointed limbs. The chitin in the jaws is used for biting and crushing food. It also forms lens of the compound eyes the copulatory organs and organs of defence and ofence.