Amazing Arthropods


1) Examine a grasshopper and a crayfish

2) Identify phylum traits

3) Identify class traits

Background Information


Scientific name: Astacoidea

Habitat: freshwater habitats

Predators: snapping turtles, bass

Prey: earthworm, dobsonfly

Adaptations: females store sperm until they're ready to lay eggs, four legs for walking on land


Scientific name: Caelifera

Habitat: grass (wow!)

Predators: beetles, birds, lizards

Food: grasses, leaves, cereal crops

Adaptations: specialized third limbs to jump up to one meter to avoid predation

Anatomy and Lab:

Arthropoda Cladogram:

System Focus:

Take a Breath as an Arthropod

Air enters the insect's body through valve-like openings in the exoskeleton called spiracles. They are located down the thorax and abdomen of most insects, and there is usually one pair of spiracles per body segment. Within each spiracle, air flow is regulated by small muscles with flap openings. Just like muscles, these flaps contract to close the spiracle and relax to open it.

After entering through the spiracle, air travels through the tracheal trunk and into tracheal tubes, which leads to the tracheole. The tracheole provides a thin, moist system for gases to exchange. Oxygen here first dissolves in the liquid of the tracheole and then dissolves into the cytoplasm of a nearby cell. At the same time, carbon dioxide is produced as a waste and leaves through the tracheal system.

Cross Content:

Human Impact

The arthropod group has provided numerous benefits to humans, although humans have shown an opposite effect. We farm various arthropods for food (crabs, lobsters, shrimp.) We also compete with them for food, since they eat the crops that we grow for agriculture. However, some arthropods do gain from humans because they use us as their hosts (mosquitoes, chiggers, fleas.)


The arthropoda phylum is by far the largest animal phylum. The major subphylums are chelicerata, crustacea, myriapoda, and hexapoda. Arthropod's closest relatives are the tardigrada and onycophora.


Annelida and Protoannelida animals lived in ocean sediment during the Cambrian period. They shared many of the same characteristics as arthropods, with bilateral symmetry and multiple segments. Zoologists still face controversy when figuring out the evolutionary path of arthropods, but they're assumed to be derived from protoannelida ancestors. However, arthropods differ from their annelida ancestors in a few ways: they have a chitinous exoskeleton, jointed appendages, and a well-developed head/mouth.

Interesting Facts

  • arthropods have been on Earth for approximately 428 million years
  • ancestral arthropods were the first land animals
  • they comprise over 90% of the animal kingdom
  • the word "arthropod" means jointed feet

Pundamental Arthropod Jokes

What arthropod has mastered the metric system?

The centipede

What is on the ground and also a hundred feet in the air?
A centipede on its back

Identify the Arthropod




Maya Waterland

Guzman - PAP Bio - 7