Basic characteristics of arachnids ke lage chaar jorra gorr (1) aur dehin jon dui hissa me hae: cephalothorax (2) aur abdomen (3).
Makrraa (order Araneae) ek rakam ke aath gorr waala, aur saans le waala (air breathing)arthropod hae, jiske lagekhaang (fang) rahe hae jisse iijahar ke inject kare hae.[1] Iijaala (web) bhi banae hae.Arachnids me makrraa sab se jaada hae aur sab jiu me se 7th rank me hae.[2]
Makrraa ke,Antartica ke chhorr ke,dunia ke sab continent me paawa jaae hae. November 2023 metaxonomist log 51,673 makrraa ke species, 136 family me record kare rahin.[3] Lekin jiu vigyanik my bahae hoe hae ki makrraa ke palwaar ke kaise classify karaa jaae, aur 1900 se lagbhag 20 different classification ke propose karaa gais hae.[4]
Anatomically, makrraa (duusra arachnids ke rakam), aur arthopods se different hae kaaheki usual dehin kesegments duitagmata me fused rahe hae,cephalothorax nai to prosoma, auropisthosoma, nai to peet, ek chhotaa cylindricalpedicel se jurraa rahe hae. Lekin abhi koi paleontological nai to embryological sabuut nai hae ki makrraa ke kabhi alag thorax-like division rahaa. Yahii rakam se term "abdomen" ke virod me bhi argument hae, kaaheki makrraa ke opisthosoma me dil aur fefrraa rahe hae.[5]
Aur sabkirwaa se alag, makrraa ke lageantennae nai rahe hae. Sab se primitive group ke chhorr ke aur sab rakam makrraa me aur sab arthopods ke milaan me sab se centralized nervous system rahe hae, kaaheki uske sabganglia ek mass me fused rahe hae, cephalothorax me. Duusra arthropod ke rakam, makrraa ke koiextensor muscles uske limbs me nai rahe hae, aur iske jaghaa aapan gorr ke hydraulic pressure se extend kare hae.
Makrraa ke peet me appendages rahe hae, jiske spinnerets me modify bhais hae jon silk ke chhe rakam ke glands me se nikaale hae. Makrraa ke jaala dher rakam ke rahe hae, aur dher different amount aur shape me sticky thread ke kaam me laawa jaawe hae. Ii abhi samjhaa jaae hae ki spiral orb web sab se puraana hoi, aur makrraa jon tangled cobwebs banae haeorb-weaver spider se aur jaada hae. Makrraa ke rakamarachnid jiske silk-producingspigot hae (Uraraneida)Devonianperiod me evolve bhais rahaa, lagbhagTemplate:Ma me, lekin ii jaanwar me spinnerets nai rahaa. Aslii makrraa keCarboniferous rocks meTemplate:Ma se paawa gais hae aur ii sab se puraana jindaasuborder hae. Makrraa ke main group,Mygalomorphae aurAraneomorphae, sab se pahile Triassic period me,Template:Ma se jaada saal pahile aae rahin.
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