Invertebrate Diversity

Introduction

Invertebrates are the animals that lack a backbone. These creatures account for 95% of known animal species. They occupy almost every habitat on Earth, from the scalding water released by deep-sea hydrothermal vents to the rocky, frozen ground of Antarctica. Species also show enormous variation in size, from microscopic organisms to organisms that can grow to 18 m long. Many invertebrates have a fluid-filled, reduced internal shell, like the slugs and squids. Others have a hard outer shell, like insects and crustaceans. There are many other types of invertebrates. Earthworm, which is the representative of Annelids, specialized in the usage of hydrostatic skeleton, peristaltic muscle contractions, and stiff bristles. The most common invertebrates today include the protozoa, annelids, echinoderms, mollusks and arthropods.

The purpose of this lab is to observe and locate the internal and external structure of each species, to gain an understanding of the basic taxonomic levels of each species and how each part of its body functions in the relation to the rest of the body. By the end of the lab, we should be able to classify the examined species into the correct phylum, class, sub-class, order, family, and genus.

Methods

Materials: dissection tray, blade, scissor, gloves, frozen crab, frozen squid, preserved earthworm, dental tools.

Crab-we grabbed a blue crab from the bucket, it was icing cold and it was a female. We placed it in the tray, and then started insert scissors into the lateral posterior edge of the dorsal carapace. We cut around the entire dorsal carapace roughly 5mm from its edge. Soon we had the carapace removed, we see a layer of dark body wall that prevents internal organs from expose to the environment, and we removed that as well. At this point, we are able to locate the sensory organs, locomotory and support structures, digestive and excretory system. We went further the dissection because the ovaries and stomachs weren’t seen....