BIOL 1020

EXPLORING INVERTEBRATES
AND VERTEBRATES
OBJECTIVES

Describe the invertebrate phyla and provide examples.
Know the distinguishing characteristics of each invertebrate phylum.
Recognize members of each invertebrate phylum.
Identify and discuss the evolutionary significance of the amniote egg.
Identify and discuss the evolutionary significance of feathers.

There are two basic groups of higher animals. They are invertebrates and vertebrates.
While both have advanced through the processes of evolution, there is one fundamental
difference. Invertebrates do not have backbones. Both groups are in Kingdom Animalia,
but their bodies are organized differently. All invertebrates share common traits:
1. They are multicellular. It’s more than being a colony of individual cells. The cells are
working together for the survival of the organism. All of the cells have specific duties
and responsibilities.
2. No backbone. That’s the whole definition of invertebrate, no vertebrae.
3. No cell walls. When we talked about plants, we always mentioned cell walls, but
animals, including invertebrates, lack this feature.
4. Here are a few that have the qualifier "most" attached. That means not all of them have
the trait, but most do. Most of them have tissues (not sponges) that are specific
organizations of cells. Most of them reproduce sexually (not asexually). That means
two gametes combine to form a new organism. Most invertebrates can move. Even
sponges move when they are very young and very small. Once they settle down they
don’t move anymore. Other invertebrates like lobsters and insects move around their
whole lives. Most invertebrates are organized in a way that makes them bilaterally
symmetrical. Bilateral symmetry means when you can draw a line down the middle of
the organism and the two sides look like mirror images. Draw a line down the middle of
yourself and one side looks like the other side. If you draw a line down the middle of an
octopus you would find two sides with equal parts. Remember we said most? Sponges
and some coral are not bilaterally symmetrical.
5. Invertebrates can’t make their own food. Scientists use the word heterotrophic.
Heterotrophs feed off other things to get their energy. Plants are autotrophic. They
make their own food. Being heterotrophic is one of the main characteristics of being an
animal. We eat things, whether it is plants or other animals. That’s just the way the
world works.
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Exploring Invertebrates and Vertebrates

BIOL 1020

Vertebrate are one of three subphyla of the phylum Chordata. Chordates are distinguished
by four characteristics. At some point in their development, they all have a notochord, a
hollow nerve cord on the dorsal side of their body, pharyngeal slits or pouches, and a tail
that extends beyond the anus. Vertebrates are distinguished from other chordates by the
presence of a bony or cartilaginous backbone that serves to protect the nerve cord. This
vertebral column also provides a pivotal attachment point for muscles. The Subphylum
Vertebrata includes seven Classes of organisms, each distinguished by major evolutionary
developments that set it apart from the rest. The vertebrates include jawless fish,
cartilaginous and bony fish, amphibians, reptiles, birds, and mammals. The vertebrate
section of this lab will investigate a few of these evolutionary adaptations that make these
animals so well-suited for their environments.

LABORATORY ACTIVITIES
EXERCISE 1: COMPARISON OF INVERTEBRATE PHYLA
PROTOCOL:
Review the information covered in your textbook and lecture notes, and fill in the tables
below. Good organization of the material will make preparation for the exams easier.
Table 1.1: Invertebrate Phyla
Porifera
Cnidaria
Mollusca

Platyhelminthes

Distinguishing
characteristics
How do they
reproduce? You
need to provide a
few significant
details for full
credit.
Foraging strategy
(i.e. how do they
get their food?)
Where do they live?
Provide an example
of an organism that
belongs to this
phylum

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Exploring Invertebrates and Vertebrates

Table 1.2: Invertebrate Phyla
Annelida
Nematoda
Arthropoda

BIOL 1020

Echinodermata

Distinguishing
characteristics
How do they
reproduce?
Foraging strategy
(i.e. how do they
get their food?)
Where do they live?

Provide an example
of an organism that
belongs to this
phylum
QUESTIONS:
1. How do sponges differ from the majority of organisms in the animal kingdom?
2. What type of symmetry do sponge’s exhibit? How does this differ from organisms
belonging to phylum Cnidaria? Arthropoda?
3. Are hydra polyps or medusas?
4. How do cnidarians defend themselves and catch prey?
5. Distinguish between acoelomates and coelomates. Next, identify an organism
considered an acoelomate, and one considered a coelomate.
6. Using one unique characteristic for each phylum, distinguish between phyla Mollusca,
Nematoda, and Echinodermata.

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Exploring Invertebrates and Vertebrates

BIOL 1020

EXERCISE 2: THE AMNIOTE EGG
All tetrapods, with the exception of amphibians, share the evolutionary advantage of
producing amniote eggs. Amniote eggs can be shelled, if embryonic development is
external, or shell-less, as is found in placental mammals. For mammals that bear live
young, some of the extraembryonic membranes of the amniote egg form the placenta,
which connects the mother to the developing embryo.
PROTOCOL:
1. Read about the structure of the amniotic egg and animals that are amniotes. More
information can be found here. You may also find your textbook useful.
2. Answer the following questions.
QUESTIONS:
1. List the animal phyla that belong to the amniote clade.

2. Do all amniotes lay eggs? Explain.

3. Which animal phylum is the most closely related to the amniotes?

4. What is the major evolutionary advantage to producing an amnion? What does that
mean for embryonic development for the animal phylum you identified in question 3 as
compared to the animal phyla you identified in question 1?

5. Identify the four extraembryonic layers of the amnion and describe the function of each.

6. Which extraembryonic layers are modified for animals that have internal development
of their offspring? Describe the purpose of the modification.

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Exploring Invertebrates and Vertebrates

BIOL 1020

EXERCISE 3: THE EVOLUTION OF FEATHERS
Feathers are an evolutionary novelty among birds. We typically think of feathers as a
mechanism for flight, which is true, but there are a variety of feathers that serve a variety of
purposes.
PROTOCOL:
1. Visit the following websites to read and learn about feathers: site 1, site 2, site 3, and
site 4.
2. Answer the following questions.
QUESTIONS:
1. Discuss the various uses for feathers.

2. Explain how form follows function for remiges and rectrices, which are types of contour
or flight feathers. In other words, describe how a flight feather’s design makes it so
effective for flight.

3. Identify the other types of feathers and describe their function.

4. What is the evolutionary relationship between dinosaurs and birds? What similarities do
they share? What are some significant differences? You might want to visit this site
and this site for more information.

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