A is For Arthropods

Arthropod Dissection PreAP Biology March 14, 2014- GABI MATA

What's an Arthropod?

An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda, which is divided into five different subgroups. The arthropod body consists of repeated segments, each with a pair of appendages. Their versatility has enabled them to be one of the most extensive members of most environments. They have over a million described species, making up more than 80% of all described living animal species, so they can adapt and evolve and can easily take on any niche, depending on their environment.

Today's Objectives

Students will be learning about the external and internal anatomy of an arthropod, specifically that of a grasshopper and a crayfish. Students will focus on the organs, structures, and functions of the two arthropods' body systems, specifically integumentary, respiratory, or skeletal. Students will also study the ecological roles arthropods play in the environment and how they are of importance to the natural world.

The Crayfish and the Grasshopper

Astacoidea

A crayfish is a part of the Crustacean sub phylum of Arthropoda and are closely related to lobsters, crabs, and shrimp. They are found in bodies of fresh water that do not freeze to the bottom, and which have shelter against predators. Most crayfish cannot tolerate polluted water. They have ten legs; the front two have developed large claws called chellae. Crayfish use their chellae not only to defend themselves, but also to attack their prey (an assortment of an animals and plants, such as worms, insects (and their larvae), certain plants, and eggs of fish, frogs, toads, and salamanders, as they are omnivorous) and pick things up. However, their claws cannot always protect them from their many predators, including raccoons, opossums, snakes and muskrats. The crayfish's ecological niche is that it is an omnivoric scavenger that likes to eat aquatic plants and small invertabrates like insects and is eaten by many other animals. It evolved from ancient species of crustaceans.

Caelifera

A grasshopper is a part of the Insecta (Hexapods) subphylum of Arthropoda. This insect can live all over the world, specially in grassy areas such as fields, meadows, forests, and woodlands. Grasshoppers are herbivore, so they feast on any type of plant matter, such as grasses, weeds, and shrubs. Because they are only primary consumers, they are also eaten as prey for predators like rodents, other insects, reptiles and birds. That is, if these predators can catch them since grasshoppers have six jointed legs that are incredibly powerful for such a small creature. They use their legs to jump extraordinary distances. A grasshopper's ecological niche is to pass droppings which contributes to nutrient turnover by returning nutrients as a sort of fertilizer for plants. They evolved from the first reptiles well over 200 million years ago.

Arthropod Dissection 101

External Anatomy:

Watch This!

The next two videos are dissections videos of both the grasshopper and the crayfish. Both videos demonstrate the external and internal anatomy of the arthropods.


Grasshopper Dissection: http://www.youtube.com/watch?v=LlipwN_5zlM


Crayfish Dissection: http://www.youtube.com/watch?v=W7F0jZgdc8A


As you watch these, make sure to write down any keynotes or questions you have. My question is: why were the people doing the dissections in each video NOT wearing gloves? Ew. Talk about gross.

Residing in the Respiratory System

In both arthropods, the respiratory system is a vital part of its daily life, helping it breathe and thrive. Despite these arthropods having many similarities in their exoskeletons and segmented body parts, the respiratory system in a crayfish is completely different from that of a grasshopper. In a crayfish, it uses gills and, in a grasshopper, it uses a specialized system known as the tracheal system. The respiratory systems in both animals also interact with all the other systems in the body as every system needs air to flow through to be able to function properly. The following down below are better explanations of the respiratory systems in both animals:

If You're Interested....

The following video below shows how a typical tracheal system in insects (this one being a common fruit fly) develops:

Crayfish and Grasshopper Virtual Labs

Feel like you want to know more? For a better hands-on visual of dissecting between a grasshopper and a crayfish, use the following sites to see the anatomies of both animals:


http://crescentok.com/staff/jaskew/isr/biology/biolab46b.htm


http://www.ent.iastate.edu/ref/anatomy/ihop/

A is for Arthropod Quiz: Let's See What You've Learned!