Unit 3:  Diversity of Life

Module 5:  Kingdom Animalia

Learning Objectives:  4.1, 4.2

Lesson 4:  The Arthropods

Lesson Objectives:

  • To describe the characteristics of organisms belonging to the phylum Arthropoda
  • To explore the reasons for the great success of the Arthropods.
  • To identify members of the phylum Arthropoda which are native to Saskatchewan.


  • Assignment:  Phylum Arthropoda Questions (15 marks)

8.  Phylum Arthropoda

Kingdom Arhtropoda includes an abundant and diverse group of organisms.  Even though the organisms vary greatly from one another, they are grouped together in the same phylum because of a few of the characteristics that they share.  All arthropods have an exoskeleton with segmented bodies and externally jointed appendages.  Also, all arthropods have a ventral nerve cord.  This means that the nerve cord is located along the bottom side of the organisms rather the top or front side like a dorsal nerve cord, which is present in all Chordates, the Phylum that we will study next.  Arthropods are free living organisms that are found in marine, fresh water and terrestrial environments.

Reading:  “The Pinnacle of Adaptation and Diversity:  Phylum Arthropoda p. 485  Nelson Biology

Take notes on the subphlya of Phylum Arthropoda along with their classes, characteristics and examples.  It may be best to create a chart to record this information.

If preserved organisms are available to you, take the time to examine the various features and diversity that exists among the arthropods.

Images of the Arthropods:

The images in this lesson were obtained from the BIODIDAC web site.  ("A bank of digital resources for teaching biology.")

Horseshoe Crab

Subphylum Chelicerata; Class Merostomata


Subphylum Chelicerata; Class Arachnida


Subphylum Crustacea


Subphylum Uniramia; Class Insecta

Waterbug (ventral surface)

Subphylum Uniramia; Class Insecta

Spider (ventral surface)

Subphylum Chelicerata; Class Arachnida

If you would like to explore more images of arthropods, click on the link below:


Assignment:  Phylum Arthropoda Questions  (15 marks)

 You may have to do some thinking and exploring to find the answers to some of these questions.

1.  Based on a single structural characteristic, what is the easiest way to distinguish:

  • a) an arachnid from an insect
  • b) a crustacean from any other arthropod
  • c) a centipede from a millipede

2.      Arthropods are well known for some of their structural adaptations which help them to survive in a particular niche.  Describe one structural adaptation for each of the following insects that help it survive in its particular niche.

  • a) grasshopper
  • b) mosquito
  • c) butterfly
  • d) wasp

3.      A hard exoskeleton is one of the general characteristics of all arthropods. 

  • a) What would be some advantagees of having an exoskeleton?
  • b) What would be some disadvantages of having an exoskeleton?

4.      Their large numbers and high diversity prove the success of insects.  Explain at least four general adaptations of insects that have made them so successful.

5.  Some arthropods can be beneficial or useful to their ecosystems or to humans and some could be harmful.  Give two examples of each.  (Try to use Saskatchewan or your own area as the source of your examples.)

Print the above questions.

Reference for question #5 above.

"Diversity of Life:  A Survey of Kingdoms."  from Biology 20.  Assignment 15, page 286.  Copyright © Saskatchewan Government Correspondence School, 2000.

Back to Unit 3, Module 5