Question

Patsy is explaining about the phylum Arthropoda to her daughter. Her daughter is wondering how they grow in size. What should be Patsy’s reply? A. that they grow by splitting into two halves B. that they grow by complete shedding of their appendages C. that they grow by partial shedding of their exoskeleton D. that they grow by increasing the length of their appendages E. that they grow by secreting more chitin

Answer 1

Arthropods grow by partial shedding of their exoskeleton.

Explanation:

Arthropods grow by a process called molting or ecdysis which is shedding of their exoskeleton periodically and replacement of new bigger skeleton. Molting process usually happens along the posterior end at the tail region leading to elongation of the body.

The exoskeleton is made up of proteinaceous thin layer, epicuticle, and procuticile or inner chitin layer. This exoskeleton contains protein and minerals which makes it hard.

Although, the exoskeleton provides good protection, it becomes tough for an arthropod to grow along with the tough exoskeletion.

So, an arthropod’s body actually grows inside the exoskeleton, and as the body grows, the exoskeleton sheds off and replaced with newer ones. Molting is controlled by growth hormones like ecdysone present in their blood.

Answer 2

C. That they grow by partial shedding of their exoskeleton is the right answer.

Explanation:

Arthropoda are invertebrates. They have an external skeleton called as exoskeleton.

The exoskeleton is made up of chitin.

It can be hard or brittle and is waterproof. The exoskeleton protects the plant from drying and gives ability to live on both land and water.

The exoskeleton has great importance in arthropod growth because as they grow in size their exoskeleton is shed off and new one is formed by the process called molting.

Arthropods keep increasing layers to existing exoskeleton.

The process of ecdysis ( growth in arthropods) is necessary because the rigid and hard exoskeleton will not grow like skin and in metamorphosis when external eyes lenses are formed the hard exoskeleton will make it difficult.