Lab8_insects

Lab8_insects - Laboratory 8 Arthropoda 154 Laboratory 8:...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Arthropoda Laboratory 8
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
154 Laboratory 8: Insects OBJECTIVES After completing this lab you will be able to: 1. Compare Arthropods and earthworms in four traits: support movement circulation feeding (and digestion) LAB PREPARATION In preparation for this laboratory you should do the following: 1. Review this laboratory. 2. Read Chapter 33,and re-read the invertebrate sections of Chapters 40, 41, 42, and 44 in Campbell (7 th Edition). 3. Bring your dissection instruments to lab. 4. Bring protective gloves to lab. INTRODUCTION Cockroaches (Order Blattaria) are insects (Class Insecta) belonging to the Phylum Arthropoda. Arthropods (Gk. arthros, joint; podos, foot) are the most numerous and successful animals on earth. At least three quarter of a million species have been described, more than three times the number of all other animal species combined. The tremendous adaptive diversity of arthropods has enabled them to survive in virtually every habitat, and the insects are perhaps the most successful invaders of the terrestrial environment. Arthropods are believed to have evolved from annelid-like ancestors. Like annelids, they are metamerically segmented. Unlike annelids, however, arthropod body segments have diversified, and have become a fascinating example of functional specialization. One of the most serious problems of terrestrial existence is the loss of body water. The solutions to these problems are two very successful and interesting morphological adaptations: a water-impermeable exoskeleton, and an internalized respiratory system, the tracheal system. Hard skeletons in the Kingdom Animalia appear in two types. One type lies outside the soft flesh as an exoskeleton, and the other lies inside the flesh as an endoskeleton. Exoskeletons, like those of insects, are derived from ectoderm. Endoskeletons, like the ones found in vertebrates, originate primarily from mesodermal tissue. While exoskeletons have the obvious advantage of protecting the vulnerable internal parts of an animal from harm, they also have one very distinct disadvantage - they limit growth. To circumvent this
Background image of page 2
Laboratory 8: Insects 155 limitation arthropods increase in size by periodically shedding their old skeleton for a new and larger one. This process is called molting or ecdysis. The cockroach has a chitinous exoskeleton, or cuticle. Chitin is a polymerized polysaccharide secreted by the underlying epidermis. Shortly after ecdysis, the cuticle is soft and flexible, thus allowing for an increase in size. The body swells rapidly by uptake of air, and when the outer layer becomes hardened, the air is released. The animal is then free to grow slowly, protected in its larger exoskeleton. Hardening of the exoskeleton is by a process known as sclerotization. Sclerotization involves the production of chemical bonds between protein chains within the cuticle. Not all parts of the cuticle harden, however; in special areas like limb joints, a specialized rubber-like cuticle, resilin, is secreted. The body of an insect can be divided into three regions: the head,
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/10/2008 for the course BIO 172L taught by Professor Gerald during the Spring '08 term at Hawaii.

Page1 / 16

Lab8_insects - Laboratory 8 Arthropoda 154 Laboratory 8:...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online