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PRESENTATION ON ARACHNIDA . GROUP 1. WHAT ARE ARACHNIDS?. ARACHNIDA ARE CLASS OF ANTHROPODS WHICH COMPRISES OF THE ORGANISM SUCH AS SPIDERS, SCORPIONS , TICKS AND MITES . Phylum Arthropoda. KINGDOM ANIMALIA. Class Arachnida (Spider, ticks, mites, scorpions ). Class Diplopoda
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PRESENTATION ON ARACHNIDA GROUP 1
WHAT ARE ARACHNIDS? ARACHNIDA ARE CLASS OF ANTHROPODS WHICH COMPRISES OF THE ORGANISM SUCH AS SPIDERS, SCORPIONS , TICKS AND MITES
Phylum Arthropoda KINGDOM ANIMALIA Class Arachnida (Spider, ticks, mites, scorpions ) Class Diplopoda (milipedes) Class Crustacea (lobster, prawn, barnacles, crabs) Class Insecta (grasshopper, cockroach) Class Chilopoda (centipedes) Class Merostomata (only 3 genera of horseshoe crabs )
GENERAL CHARACTERSITICS OF ARACHINIDAS • Usually terrestrial arthropods • No antennae and mandibles • Body divided into 2 parts i.eProsoma and opisthosoma). • Prosoma or Cephalothoraxes usually bears a pair of prehensile, chelicerae, one pair of pedipalps and 4 pairs of waking legs.
CHARACHERISTICS OF THE ARACHINIDAS • Opisthosoma or abdomen of thirteen segments. • Simple eyes only (No compound eyes) • Most of arachnids are predaceous and may be equipped with claws, fangs, poison glands or stingers.
OTHER UNIQUENESS • 6 pairs of appendages: two for feeding, sensing, and ATTACKING // four for locomotion • Respiration – tracheal system, book lungs. • Excretory: • Malpighian tubule system - absorbs solutes, water, waste; releases waste as nitrogenous compound • Coxal gland – collects and excretes urine; helps Malpighian system release waste
ARACHNIDAS HAVE THREE ORDERS • Order :Araneida– spiders • Order: Scorpionida– Scorpions • Order: Acarina- ticks and mites
Order: Araneida – spiders • The spiders are a large group of 35,000 species, distributed all over the world (cosmopolitan) • Body compact: a cephalothorax (prosoma) and abdomen (opisthosoma) both unsegmented and joined by a slender pedicel (narrow waist). • Chelicerae prehensile inject paralyzing poison into prey • Pedipals sensory modified for sperm transfer in the male • Three pairs of spinnerets are preset of the tip of the abdomen (opisthosoma) for spinning the web. • Excretory system is unique of malpighian tubules that work in conjunction with rectal glands Uric acid. • 8 simple eyes, which are usually poor in vision so they depend on its hair, like sensory setae. E.g. Opera – garden spider.
2. Order: Scorpionida – Scorpions • Prosoma (cephalothorax) is short and covered by dorsal carapace. • Opisthosoma (abdomen) is divided into pre abdomen (mesosoma) and the post abdomen (metasoma) which is narrow than the pre abdomen bearing terminal sting (tersion). • The sting has a bulbular base that contains venom-producing glands. • The chelicerae are small, the pedipalps are large and both are prehensile. • Spinnerets absent.
3.Order: Acarina- ticks and mites • Many are ecto-parasites on human, domestic and wild animals. Others are freeliving. Eggs may hatch as “larvae” with three pairs of legs or may be viviparous
VALUES OF ARACHNIDA • They are prey of other organism like birds, fishes, snakes and other organism, • Used in pollination of flowering plants • They are predators, they many eat insects that destroy crops • In medicine, spider silk is used in manufacturing of artificial tendons THREATS OF THE ARACHNIDA • Cause diseases like Lyme caused by ticks • Cause serious injuries to human beings • May cause anxiety attack related to arachnids namely spiders
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