ARTHROPODA (Animals with jointed legs)

The individuals from phylum Arthropoda are known as Arthropods.




General Characters

1. Jointed Legs: Arthropods are creatures (animals) with jointed legs. The word arthropod is derived from the words Arthro & pods meaning jointed legs. As it were, the arthropods own jointed appendages.

2. Largest Phylum: The phylum contains more species than all the other phyla put together.

3. Segmented Body: The body is segmented/divided. Each section is joined to its neighbour by means of an adjusted segment of the cuticle. It is thin and flexible.

4. Origin: They are believed to have a common origin with annelids because both have segmented body, appendages and cuticle.

5. Habitat: They live ashore (on land) and in water. thalassic species incorporate both freshwater and marine. Many can fly, therefore visit air periodically.

6. Shape: Some are worm-like centipedes. some are flying bugs their body is divided into head, thorax and abdomen. The body is secured with chitinous cuticle secreted by Epidermis.

7. Haemocoel: The coelom is absent as the main body cavity instead of haemocoel is developed. It is reduced coelom. It speaks with a blood vascular framework.

8. Digestive System: The digestive system is in the form of the nutritious channel with 2 openings mouth and anus. The food comprehends (comprises) small plants and animals.

9. Excretory System: The excretory system incorporates of Malpighian tubules. Nitrogenous squanders are discharged in the form of uric acid.

10. Sense Organs: Sense organs are available as a pair of compound eyes and antennae.

11. Nervous System: It consists of paired cerebral ganglia in the head which represent brain. The brain is associated with a ventral double nerve string. Nerves emerge from these ganglia which are available in each fragment.

12. Respiratory System: Most arthropods possess Tracheal system for the exchange of gases. Trachea open to the exterior through openings known as Spiracles. Oceanic arthropods respire through gills.

13. Circulatory System (Open type): The blood circulatory system in arthropods is open sort. The blood circulations in the body cavity washing tissues of the body. However, there is a crude heart and vein (blood vessel). Blood is dull without Hb are known as haemolymph.

14. Skeleton: The skeleton is outside for example Exoskeleton. It is in the form of the external concealing of cuticle made up of chitin. It gives a surface to the connection of muscles which help in locomotion (movement).

15. Locomotion: The organs of motion are paired appendages and paired wings additionally in some cases.

16. Reproduction: The sexes are isolated. The testicles and ovaries produce sperms and eggs respectively.

17. Metamorphosis: Life histories of worms are characterized by transformation (meta = change + transformed - structure). Transformation is the progressions from hatchling to grown-up. There are two ilks of metamorphosis.

  • Complete Metamorphosis
  • Incomplete Metamorphosis

Complete Metamorphosis

There are 3  particular phases of partial metamorphosis.

(i)  Egg →         (ii)  Large  →          (iii)   Pupa →     (iv) Adult (Mosquito)

The egg develops into larva. The larva is converted into motionless pupa that develops into an adult.


Incomplete Metamorphosis

In some bugs metamorphosis is incomplete. The larva looks like the adult and known as nymph or instar. It lives in a similar habitat as an adult.    Egg → Nymph or instar → Adult (cockroach)

18. Examples: Cockroach, butterflies, mosquitoes, ants, prawans, scorpion, centipedes, millipedes.

CLASSIFICATION OF ARTHROPODA

  • Class Crustacea
  • Class Insecta
  • Class Arachnida
  • Class  Myriapoda
   

1- Class Crustacea

i. Habitat: Oceanic with gills for respiration.

ii. Exoskeleton: Exoskeleton as carapace made up of chitin and salts.

iii. Appendages: Appendages are adjusted for walking, swimming, breath and generation.

iv. Head: Head has two duos/pairs of appendages i.e. (1) jaws (2) Maxillae.

v. Coelom: It is curtailed and haemocoel is available.

vi. Reproduction: Replicate sexually, Sexes independent.

vii. Examples: Water flea, Cyclops, Crabs, Lobsters, Prawn, Woodlouse.


2- Class Insecta

1. Number: It is the biggest gathering of Arthropoda as well as of all the set of animals. This cluster/group has an incredible assortment.

2. Habitat: They are found everywhere.

3. Division of body: Bugs have three varying regions.


  •  Head
  • Thorax
  • Abdomen

Head: There is a duad of receiving wires on the head. Compound eyes are furthermore available.

Thorax: The thorax has 3 bits. Thorax has 3 duads of jointed legs. In numerous creepy crawlies, a couple of sets of wings are available.

 Abdomen: The stomach area (abdomen) has an alternate number of segments.

4. Respiration: Respiration by Tracheae.

5. Nervous system: The brain is formed of fused ganglia and verve cord and ventral.

6. Reproduction: Sexes are isolated, oviparous.

7. Development: Metamorphosis happens during progress.

8. Examples: Housefly, mosquito, butterflies, moth,  beetles.


3- Class Arachnida

1. Segmentation: The body has the anterior segments that are fused to form a combined cephalothorax.

2. Appendages: The cephalothorax has the following extremities.

  • A pair of cheliceral with claws.
  • Two pairs of pedipalps.
  • Four pairs of legs.

3. Antenna: There are no receiving wires (antennae).

4. Jaws: There are no obvious jaws.

5. Abdomen: Abdomen segmented or unsegmented with or without limbs.

6. Respiration: Respiration by lungs, gills or special structure known as book lungs (scorpion)

7. Excretion: Excretion takes place by Malpighian tubules.

8. Sense Organs: Eyes are straightforward.

9. Sexes: Sexes are separated, oviparous.

10. Metamorphosis: No true metamorphosis.

11. Examples: Scorpion, spiders, mites, ticks.


4- Class Myriapoda

1. Structure: Elongated dorsoventrally flattened.

2. Segmentation: The body is isolated into numerous segments with a couple of legs.

3. Antennae & Eyes: A pair of antennae (reception apparatuses) and eyes present on the head.

Example: Centipede, Millipede.