Phylum Arthropoda

PHYLUM ARTHROPODA

This is the phylum with the most number of animals  (arthras-jointed ,pod-feet.

Characteristic  features

  1. Have jointed appendages which include legs and other body out growths e.g antennae
  2. Have an open blood circulatory system
  3. Have bodies which are segmented i.e with distinct divisions
  4. Have a bilateral symmetry
  5.  Have a developed nervous system located ventrally on the body
  6. They shed off their exo skeleton to allow growth

This phylum is divided into four classes basing on;

  1.  Number of limbs
  2.  Number of body divisions
  3.  Presence of antennae
  4.  Number of antennae

The four classes of this phylum are;

Insecta

Arachnida

Myriapoda

Crustacea

 

CLASS EXAMPLES NUMBER OF BODY DIVISIONS NUMBER OF LEGS NUMBER OF ANTENNAE
Insecta Grasshoppers ,housefly, bees ,beetles 3 6 2
Arachnida Spiders, ticks, mites, scorpions 2 8 None
Crustacea Woodlice, crayfish,  lobsters, water flea 2 10 or more 4
Myriapoda Centipedes, millipedes Many body segments with head Many 2

CLASS INSECTA

Insects have the following characteristics

  1. The body is divided into three body parts, namely; head, thorax, and abdomen
  2. They have three pairs of legs on the thorax
  3. They have a pair of compound eyes except the soldier termites
  4. Adults have one or two pairs of wings except some few members
  5. They breath through the spiracles and gases reach the body cells through the tracheal system
  6. The thorax is divided into three main parts i.e. prothorax, mesothorax, and metathorax

 

CLASS ARACHNIDA

Arachnids have the following characteristics

  1. They do not have wings
  2. Its body is divided into two parts i.e cephalothorax and abdomen
  3. It has four pairs of legs attached to the cephalothorax
  4. It has no antennae
  5. It has simple eyes
  6. It breathes by means of the lung book located in the abdomen

Its mouth parts are segmented and end in

CLASS CRUSTACEA

They have the following characteristics

  1. They are aquatic or live in damp places
  2. They use the gills and body surface for breathing
  3. They have two pairs of antennae
  4. They have two body divisions namely; cephalothorax and abdomen

CLASS MYRIAPODA

They contain the following characteristics

  1. It has an elongated body with many legs
  2. It has one pair of antennae
  3. It breathes through the spiracles
  4. It lives on land
  5. It has many body segments
  6. It has simple eyes

DIFFERENCES BETWEEN CENTIPEDES &MILLEPEDES

CENTIPEDES MILLEPEDES
Have fewer body segments Have many body segments
Have one pair of legs per segment Have two pairs of legs per segment
Have poison claws Have no poison claws
Are carnivorous Are herbivores
Do not coil They coil
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