by Miller & Levine
[complete Table of Contents]
the pull-down menu to jump to any of the Book's 40 Chapters:
what this critter is (was)? Click Here to find out
chapter, students will read about the major trends and patterns in the
evolution of invertebrate animals. They will also read about the major
organ systems and life functions of invertebrates. The links below lead
to additional resources to help you with this chapter. These include Hot
Links to Web sites related to the topics in this chapter, the Take It
to the Net activities referred to in your textbook, a Self-Test you can
use to test your knowledge of this chapter, and Teaching Links that instructors
may find useful for their students.
29-1: Invertebrate Evolution
As animals became
larger and more complex, specialized cells joined together to form tissues,
organs, and organ systems that work together to carry out complex functions.
except sponges exhibit some type of body symmetryeither radial symmetry
or bilateral symmetry.
with cephalization can respond to the environment more quickly and in
more sophisticated ways than can simpler invertebrates.
with bilateral symmetry also have segmented bodies. Over the course of
evolution, different segments have often become specialized for specific
Most animal phyla
have a true coelom that is lined completely with mesoderm.
and mollusks are protostomes, and echinoderms are deuterostomes.
29-2: Form and Function in Invertebrates
The simplest animals
break down food primarily through intracellular digestion, whereas more
complex animals use extracellular digestion.
have large surface areas that are in contact with the air or water. In
order for diffusion to occur, these respiratory surfaces must be kept
Most complex animals
move fluid through their bodies using one or more hearts and an open or
closed circulatory system.
Most animals have
an excretory system that rids the body of metabolic wastes and controls
the amount of water in their tissues.
show three trends in the evolution of the nervous system: centralization,
cephalization, and specialization.
have one of three main kinds of skeletal systems: hydrostatic skeletons,
exoskeletons, and endoskeletons.
reproduce sexually during at least part of their life cycle. Depending
on environmental conditions, however, many invertebrates may also reproduce