Go Back   Freethought Forum > The Library > Articles & Essays > Science

Comment
 
Article Tools Display Modes
An Introduction to Zoology:  Chapter 4
An Introduction to Zoology: Chapter 4
Published by The Lone Ranger
08-04-2008
Default Introduction

An Introduction to Zoology

Chapter Four: Animal Body Plans and Phylogenies:



Body Plans:
An organism’s body plan is the set of distinctive morphological and developmental traits that is characteristic of the taxon to which it belongs. It’s important to remember that a particular body plan may have evolved more than once in life’s history though, so it can be a mistake to think that just because two different species have similar body plans that they’re necessarily closely-related.

Extant animal species display a relatively small number of body plans. From this fact, and from examination of the molecular and fossil records of animal evolution, it seems that once a particular body plan has evolved, it tends to remain remarkably stable. For instance, comparisons between species that are separated by hundreds of millions of years of evolutionary history reveal that the molecular control of gastrulation has not changed in over 500 million years.

Because animals’ body plans are so stable, they have often been used to classify organisms. For example, all animals with radial symmetry are often assumed to make up a distinct clade, while animals with bilateral symmetry are often assumed to make up a different clade.

Nowadays, we have the ability to directly compare organisms’ genetic and biochemical makeups in order to determine their evolutionary relationships. What these molecular techniques sometimes reveal is that just because organisms share similar body plans doesn’t always mean that they’re related.


Contents

Article Tools

Featured Articles
<< <    Next Page: Body Symmetry (Page 1 of 22)    >  >>
Thanks, from:
Corona688 (08-10-2008), curses (08-04-2008), Ensign Steve (08-05-2008), monruw (03-30-2011), Stormlight (08-05-2008)
Comment

  Freethought Forum > The Library > Articles & Essays > Science


Currently Active Users Viewing This Article: 1 (0 members and 1 guests)
 
Article Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

 

All times are GMT +1. The time now is 06:47 PM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.

Article powered by GARS 2.1.8m ©2005-2006
Page generated in 0.21923 seconds with 17 queries