Question

Arthropods represent the cumulation of evolutionary development in the protostomes. identify at least three characteristics that contribute to their success. and explain the selective advantage of each exmaple.

Answer 1

Answer:

Three characteristics of arthropods that contribute to their success are:

1) Development of the exoskeleton (hard chitinous):

• The exoskeleton is the rigid external covering (shell) of the arthropod and is composed primarily of chitin. Arthropods discard their exoskeleton (molting) and new soft exoskeleton grows underneath the old one. Exoskeleton provides protection and support to arthropods. It also acts as site for muscle attachment.
• Selective advantage: Exoskeleton provides protection against physical injury and strengthens the body of the arthropods. It also prevents evaporation of water from the arthropod's body.

2) Segmentation of body:

• The body of arthropods is segmented into three different regions - head, thorax and abdomen. Head consists of specialized mouthparts for feeding and compound eyes. Thorax consists of 6 legs and 2 pairs of wings. The abdomen is the posterior segment of the body in arthropods.
• Selective advantage: segmentation helps in improved locomotion and feeding in arthropods.

3) Joined appendages or legs:

• Appendages extend from the body wall of the arthropods and can have several variation (paired joined appendages could include mouth parts, legs, antennae, claws etc.) Joined appendages help in advancement movement and antenna appendages are used for sensing purpose.
• Selective advantage: Joined appendages helps arthropods to move easily. Other than these features, arthropods have highly developed sense organs.