Comparative Study of Animal Phyla and Body Plans

Biology

This document compares six animal phyla (Porifera, Cnidaria, Platyhelminthes, Annelida, Arthropoda, Chordata) based on their mode of life, body plan characteristics such as cephalization, symmetry, tissue layers, body cavity (coelom), blood system, and digestive tract completeness. It also elaborates on radial and bilateral symmetry, and the significance of germ layers (diploblastic and triploblastic) in animal development and organization.

Zoology Evolution Comparative Anatomy

21 Questions Medium Ages 12+ Mar 8, 2026

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About this Study Set

This study set covers Biology through 21 practice questions. This document compares six animal phyla (Porifera, Cnidaria, Platyhelminthes, Annelida, Arthropoda, Chordata) based on their mode of life, body plan characteristics such as cephalization, symmetry, tissue layers, body cavity (coelom), blood system, and digestive tract completeness. It also elaborates on radial and bilateral symmetry, and the significance of germ layers (diploblastic and triploblastic) in animal development and organization. Every question includes the correct answer so you can learn as you go — pick any format above to get started.

Questions & Answers

Browse all 21 questions from the Comparative Study of Animal Phyla and Body Plans study set below. Each question shows the correct answer — select a study format above to practice interactively.

1 Which phylum is characterized by sessile and free-living modes of life, radial symmetry, and lacks cephalization and a blood system?

A Porifera
B Cnidaria
C Platyhelminthes
D Annelida

2 Animals with bilateral symmetry can be cut into two mirror images by how many vertical planes through their center?

A More than one
B Exactly one
C No vertical planes
D Any plane

3 What is the term for the concentration of nerve cells at the anterior end of a bilaterally symmetrical animal's body?

A Nerve net
B Central nervous system
C Cephalization
D Ganglion

4 Which phylum has a triploblastic body, a closed blood system, and is coelomate with two openings in the digestive tract?

A Arthropoda
B Annelida
C Chordata
D Platyhelminthes

5 Animals that have an ectoderm and an endoderm, separated by a non-cellular mesoglea, are classified as:

A Triploblastic
B Diploblastic
C Acoelomate
D Coelomate

6 Which phylum includes free-living and parasitic forms, is bilaterally symmetrical, triploblastic, and acoelomate?

A Cnidaria
B Annelida
C Platyhelminthes
D Arthropoda

7 What type of symmetry is characterized by having a definitive oral and aboral side, but no left or right side?

A Bilateral symmetry
B Asymmetrical
C Radial symmetry
D Spherical symmetry

8 The phylum Porifera consists of animals that are:

A Diploblastic and radially symmetrical
B Triploblastic and bilaterally symmetrical
C Cellular level of organization and asymmetrical
D Organ level of organization and radially symmetrical

9 Which of the following is a characteristic of Arthropoda?

A Closed blood system
B Coelenteron
C Open blood system (haemocoel)
D Spongocoel

10 Animals that are triploblastic have how many germ layers in their developing embryo?

A One
B Two
C Three
D Four

11 Which phylum is described as aquatic (fresh and sea water), terrestrial, and underground, with cephalization and an open blood system?

A Annelida
B Chordata
C Arthropoda
D Platyhelminthes

12 The term 'sessile' means an animal is:

A Able to move quickly
B Sedentary and attached to a substrate
C Free-floating in water
D Burrowing underground

13 Which phylum possesses a coelom, is triploblastic, and has a closed blood system?

A Cnidaria
B Porifera
C Platyhelminthes
D Annelida

14 What is the primary disadvantage of radial symmetry mentioned in the text?

A Slow and inefficient locomotion
B Lack of a digestive tract
C Absence of cephalization
D Limited environmental adaptation

15 All bilaterally symmetrical animals are:

A Diploblastic and do not develop organs
B Triploblastic with three germ layers
C Radially symmetrical
D Acoelomate

16 The body cavity in Arthropoda is often referred to as a:

A Coelom
B Spongocoel
C Coelenteron
D Haemocoel

17 Which phylum is characterized by having only one opening for both ingestion and egestion?

A Chordata
B Annelida
C Platyhelminthes
D Arthropoda

18 Animals that show radial symmetry have an extended:

A Central nervous system
B Specialized head
C Nerve net
D Complex organ systems

19 Which of these phyla are described as occurring everywhere, including terrestrial and aquatic environments?

A Cnidaria and Porifera
B Platyhelminthes and Cnidaria
C Annelida and Arthropoda
D Porifera and Platyhelminthes

20 The ectoderm is the:

A Inner germ layer
B Middle germ layer
C Outer germ layer
D Non-cellular jelly layer

21 Which phylum has a 'spongocoel' and is aquatic (sea water)?

A Cnidaria
B Porifera
C Platyhelminthes
D Annelida

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