Chapter 32 - Animal Diversity & the Evolution of Body Plans

Select characteristics of the mesoglea of cnidarians.

Can contain many cells Found between the epidermis and the gastrodermis Can be acellular

What organisms are included in the phylum Ctenophora?

Comb jellies

What are the functions of a hydrostatic skeleton in animals lacking a skeleton of shell or bone?

It gives shape to the animal. It provides a rigid structure against which muscles can operate.

Which of the following are characteristics of ctenophores?

Many species are bioluminescent. They possess colloblasts for prey capture. They move by coordinated beating of cilia.

Which of the following statements regarding the two body forms in the life cycle of cnidarians is true?

Most species have both forms, but some species may not have either a medusa or a polyp form.

What cnidarian form is characterized by a cylindrical body with a mouth surrounded by tentacles at the end of the cylinder opposite where it is attached to substrate or colonial tissue?

Polyp

Consider a cnidarian, which forms both a polyp and a medusa stage. Which of the following statements about the life cycle of such a cnidarian are TRUE?

Polyps are sessile Medusae are free-swimming

In cnidarians, what is a medusa?

The free-swimming form that is umbrella-shaped with a mouth on the concave underside, surrounded by tentacles

In cnidarians that exhibit both polyp and medusa in the life cycle, how are gametes typically formed?

The medusa produces both sperm and eggs.

Which of the following accurately describes reproduction in cnidarian species which do not have a medusa form?

The polyp form produces gametes and the resulting planula develops directly into a polyp.

Which of the following accurately describes why ctenophores are no longer considered closely related to cnidarians?

They have muscle cells derived from mesoderm. They are structurally complex. They lack nematocysts.

Which of the following are characteristics of cnidarians?

They have radial symmetry. They are made of distinct tissues. They are diploblastic.

Which of the following is true of the two body forms found in cnidarians (polyp and medusa)?

They share the same basic morphology - mouth, gastrovascular cavity, and tentacles.

How do ctenophores move?

They use the beating of their cilia.

Which of the following accurately describes the number of body forms exhibited by most cnidarians?

Two

Ctenophores use eight rows of comb-like plates of fused ________ to propel themselves in the water column.

cilla

Comb jellies make up the phylum

ctenophores

In eumetazoans, digestive tissue that develops from the embryonic endoderm is known as the ______.

gastrodermis

The ________ cavity of cnidarians is the site of digestion, gas exchange, waste discharge, and, in many species, gamete formation.

gastrovascular

In cnidarians, dispersal occurs in _______ and _______.

larva or larvae medusa or medusae

The polyp form of cnidarians has a tubular body with a __________ that is surrounded by ________.

mouth tentacles

A hydrostatic skeleton serves two main functions: it provides a rigid structure against which _______ can operate and it gives the animal _______.

muscles shape or form

In cnidarians, a zygote develops into a planktonic ciliated ________ larva that metamorphoses into a polyp.

planula

In cnidarians, a zygote develops into a planktonic ciliated _________ larva that metamorphoses into a polyp.

planula

Cnidarians may exist as either __________ or _______ , or they may alternate between both phases during their life cycle.

polyps medusae