Question

1. There are two major groups of animals, what are they?
2. What is the difference between invertebrates and vertebrates?
3. Animals are placed, grouped, into “phyla” (groups) … what is considered to be the simplest animal?
4. Name IN Order of increasing complexity all of the different phyla of animals we have had in our class (there are actually 35, but we only briefly talked about 9)
5. Identify one or two (if present) traits, characteristics, that is significant to each phyla
6. What animals belong in the Porifera phyla?
7. What animals belong in the cnidarian phyla?
8. What are the 3 major groups of platyhelminthus?

Answer 1

1

The 2 major groups of animals are Vertebrates and Invertebrates.

Vertebrates are all those animals with a backbone. Humans are an example of vertebrate since we have a backbone which is part of our skeleton.

Invertebrates are all animals without a backbone. These animals do not have a bony skeleton. e.g. all insects are invertebrates. Their skeleton is on the outside of their body and is not made of bone.

2

The major difference is mentioned above. Apart from this, vertebrates have a highly developed brain and nervous system which the invertebrates lack. Vertebrates also have an outer skin covering.

Invertebrates do not have a cell wall and are heterotrophic in nature.

3

The simplest animals belong to the Phylum Porifera.

These animals lack a nervous, digestive or circulatory system. They rely on maintaining constant water flow through their bodies to obtain food and oxygen and to remove waste material.

4

The 9 major phyla are as follows:

a.    Porifera

b.    Cnidaria

c.    Platyhelminthes

d.    Nematoda

e.    Annelida

f.     Mollusca

g.    Echinodermata

h.    Arthropoda

i.     Chordata

5

Major characteristics of the above Phyla:

a.    Porifera – They have a central opening called osculum. These have only a few specialized cells and are filter feeders. They lack a body cavity and are sessile.

b.    Cnidaria – These are soft-bodied animals and have stinging tentacles. Their body has radial symmetry and contains specialized cells. They also have 2 germ layers – endoderm and ectoderm.

c.    Platyhelminthes – These have a flattened body (flatworms). They do not contain coelom between the tissues (another feature). They have bilateral symmetry. A gastrovascular cavity with a pharynx is present.

d.   Nematoda – These are also called the roundworms. The body is round and unsegmented. The body cavity contains a pseudocoelom. They have three germ layers and a complete digestive system. They also have bilateral body symmetry.

e.    Annelida – Their body is divided into segments that are separated internally by walls (septa). They have bilateral symmetry and a true coelom or body cavity. They have a complete digestive system with specialized organs and a closed circulatory system.

f.     Mollusca – These are soft-bodied animals with an internal or external shell. They have bilateral symmetry. These usually have an anterior head and a ventral foot.

g.    Echinodermata – They have a spiny internal skeleton with radial symmetry. These contain a water vascular system.

h.   Arthropoda – Their body consists of a head, thorax, and abdomen. These contain jointed appendages and a chitinous exoskeleton. They generally have bilateral symmetry.

i.     Chordata – These contain an internal skeletal rod (at some stage of development), a dorsal nerve cord. They have bilateral symmetry, a complete digestive system, and a closed circulatory system. They also contain a tail at some stage of development.

6

Different types of sponges belong to the Porifera phyla. Specific examples include yellow tube sponge and Sycon.

7

Some examples of the phyla Cnidaria include Corals, Jellyfishes, Sea Anemones, Hydra, Obelia, and Physalia.

8

The 3 major groups of Platyhelminthes are – Turbellaria (flatworms); Trematoda (flukes) and Cestoda (tapeworms).