notes4 - Introduction Integument, Development, and...

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1 1 Integument, Development, and Reproduction 2 Introduction Have you ever watched a butterfly emerge from its cocoon? If you have ever watched this amazing process, you may have wondered how this happens. In this unit you will study the molting process, including the hormones involved. First you will need to learn about the structure and composition of the exoskeleton. In the final portion of the unit you will learn about the insect reproductive system and how insects propagate their kind. 3 Objectives By the end of this unit you should be able to: 1. Describe the three layers of an insect's integument. 2. Describe the advantages and disadvantages of an exoskeleton. 3. Using the proper terms for the structures involved, and explain the steps in the molting process. 4. Explain the role of JH and Ecdysone, where they come from, and how they are used together during the molting process. 5. Identify the internal and external reproductive structures of insects and describe what they do or what they are used for. 4 In unit one you learned that arthropods have an outer exoskeleton made up of chitin and proteins. The exoskeleton is also called the cuticle and is made up of three layers: the epicuticle , exocuticle , and endocuticle. The top layer, the extremely thin epicuticle, is a protective waterproof layer made of lipids and polyphenols. The exocuticle is the hardened layer consisting of chitin-protein microfibers linked together to form a plastic-like material. The innermost layer of the cuticle is the flexible endocuticle. It also is made proteins and chitin but they are not linked to form a hardened matrix as in the exocuticle. The cuticle is only made of chitin and proteins, not made up of cells. Below the cuticle is a layer of cells, called the epidermis . The epidermal cells supply the proteins, chitins, lipids and other products contained in the exoskeleton. These cells play a critical role in replacing the old exoskeleton when the insect molts. We will describe this process later in the unit. Integument Layers 5 The cuticle and epidermis make up what we call the insect's integument . Below the integument is a basement membrane --it is not known entirely what makes up this layer. This layer separates the epidermal cells from the insect blood. The membrane has pores large enough to allow proteins and other molecules in the blood to pass through the membrane and on to the epidermal cells. Integument cross-section Integument Cross-section of cockroach cuticle Read textbook pages 22-24. 6 Exoskeleton Advantages The insect exoskeleton serves several important functions. First it acts as physical barrier protecting the insect from everything from thorns to bacteria. It also acts as a waterproof barrier keeping in body moisture in dry habitats and keeping water out in wet habitats. Besides protection and keeping moisture in, the cuticle provides a place for muscles to attach since insects have no internal skeleton. In the human muscular system, you can imagine how our muscles attach
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This note was uploaded on 07/23/2011 for the course ENY 3005 taught by Professor Staff during the Spring '08 term at University of Florida.

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notes4 - Introduction Integument, Development, and...

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