Sponges - Advanced
Douglas Wilkin, Ph.D. Jennifer Blanchette
Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required)
To access a customizable version of this book, as well as other interactive content, visit www.ck12.org
CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-source, collaborative, and web-based compilation model, CK-12 pioneers and promotes the creation and distribution of high-quality, adaptive online textbooks that can be mixed, modified and printed (i.e., the FlexBook® textbooks). Copyright © 2015 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by federal, state, and international laws. Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms. Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution-Non-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated herein by this reference. Complete terms can be found at http://www.ck12.org/about/ terms-of-use. Printed: December 22, 2015
AUTHORS Douglas Wilkin, Ph.D. Jennifer Blanchette
www.ck12.org
C HAPTER
Chapter 1. Sponges - Advanced
1
Sponges - Advanced
• Describe the general characteristics of sponges and how the various classes of sponges are distinguished.
So what exactly is a sponge? Here we have a giant pink barrel sponge adorned with tube sponges and gorgonian sea fans. How can something that looks like that be considered an animal? Where’s the head? Where are the legs? Where’s the mouth? Sponges are aquatic, invertebrate animals that make up the phylum Porifera. The word Porifera means “porebearing,” and a highly porous body is one of the most striking features of sponges. Sponges are the simplest multicellular animals found in the fossil record. It is difficult to imagine that an organism as complicated as a human being could be related to such a remarkably simple animal. However, sponges represent an essential step in the evolution of complex animals: the transition from simple protists to multi-celled, complex animals. In this concept we will consider the characteristics and classification of sponges, their specific structural features, how they reproduce, and the environments that they inhabit. 1
www.ck12.org Characteristics and Classification of Sponges
The phylum Porifera contains many beautifully colored sponge species (see http://www.pbs.org/kcet/shapeoflife/ animals/porifera.html ) that range in size from one centimeter (about the width of a pinky finger) to over one meter (about the arm span of a human) in diameter. An example of a sponge is shown in the Figure 1.1. Sponges arose roughly 500 million years ago, and there are currently over 5,000 different species. Adult sponges are sessile, meaning that they are not able to move from place to place. This characteristic makes sponges seem superficially plant-like, but sponges do not share other features of plants. In particular, sponges are not capable of photosynthesis. See The First Animal at http://www.pbs.org/kcet/shapeoflife/episodes/origins.html for an introduction to sponges.
FIGURE 1.1 The sponge species Aplysina aerophoba.
Sponges do not have organs or true tissues, however, they do have specialized cells that can carry out distinct functions within the organism. This is generally referred to as cellular-level organization. Cell specialization is one of the major advantages that multicellular animals, or metazoans, have over single-celled organisms. This is the first step in the evolution of tissue and organ systems, such as the muscular and nervous systems. These developments ultimately allow higher organisms to have complex interactions with their environments. There are three classes within the phylum porifera: Calcerea, Desmospongia, and Hexactinellida. Sponges are divided into these classes based primarily on the composition of their spicules and skeletal fibers. Spicules are rodshaped cellular projections that make up the skeleton of sponges. Sponges within the class Calcerea have skeletal spicules made up of calcium carbonate. Species within the class Hexactinellida are also referred to as glass sponges because their skeletons consist of spicules made of silica, the primary component of glass. The skeletons of the class Desmospongia are composed of spicules made up of silica and skeletal fibers made from spongin, a type of collagen protein. Desmospongia is the most abundant class of sponges alive today. More than 90% of all known sponge species are found within the class desmospongia. Because their skeletons are often composed primarily of spongin fibers that are less rigid than spicules, it is desmospongia species that have been used to make the cleaning sponges we commonly think of when we hear the word “sponge.” This will be discussed in greater detail in the Sponges: Ecology (Advanced) concept. Sponges are filter-feeders that pump water in via their porous surface and through a system of internal canals where bacteria and nutrients can be trapped and digested.
Vocabulary
• metazoan: A multicellular animal. 2
www.ck12.org
Chapter 1. Sponges - Advanced
FIGURE 1.2 Stove-pipe Sponge (Aplysina archeri) and corals on a tropical reef in Bonaire, Netherlands Antilles.
FIGURE 1.3 Yellow Tube Sponges.
FIGURE 1.4 Colorful red finger sponge and brown tube sponges on Belize reef.
3
www.ck12.org • sessile: Not able to move from place to place. • spicule: Rod-shaped cellular projections that make up the skeleton of sponges. • spongin: A type of collagen protein found in the skeletal fibers of the class Desmospongia. Summary
• Sponges are the simplest multicellular organisms, classified by their primitive cellular-level of organization, their porous bodies, and their filter-feeding system. • Sponges have specialized cells that can carry out distinct functions within the organism. • Sponges are divided into three classes based primarily on the composition of their spicules and skeletal fibers. Practice
Use this resource to answer the questions that follow. • Proifera sponges at http://animaldiversity.ummz.umich.edu/site/accounts/information/Porifera.html . 1. What function do choanocytes perform within sponges? 2. What are the canals and pores in sponges called? 3. Where are sponges usually found? Review
1. How many different species of sponges are there? How are they characterized? 2. How are sponges divided into different classes? 3. What class of sponges is most common?
References 1. Parent Géry. http://commons.wikimedia.org/wiki/File:Tylodina_perversa_(Gmelin,_1791)_sur_Aplysina_aer ophoba_Narcot,_1843.jpg . Public Domain 2. Image copyright Stubblefield Photography. Stove-pipe Sponge (Aplysina archeri) and corals on a beautiful t ropical reef in Bonaire, Netherlands Antilles. . Used under license from Shutterstock.com 3. Image copyright Manda Nicholls. Yellow Tube Sponges . Used under license from Shutterstock.com 4. Image copyright Dennis Sabo. Colorful red finger sponge and brown tube sponges on Belize reef . Used under license from Shutterstock.com
4
