BACKGROUND:
The vertebrates refer to the phylum called
CHORDATA. Members of this phylum are our common everyday animals. All mammals,
birds, amphibians, reptiles, and fish belong to this group. There are over
45,000 species throughout the world. Vertebrates have a backbone, a nervous
system, and a gill slit during some stage of their life cycle. In
land-dwelling vertebrates, these slits are present only in the embryo.
Mammals have distinct characteristics
including: controlled body temperature, highly developed jaws, a coat or hairy
skin covering, highly developed internal organs, and mammalian glands. Most
important is their mode of reproduction and the way in which the young are fed
on the mother's milk.
Birds are warm blooded and have a constant
body temperature (with some exceptions). Birds have succeeded in conquering
the air by having a very light skeleton. The beak and eyes are highly
developed. They have feathers and produce eggs.
Reptiles are mainly terrestrial, but there
are many living partly in the aquatic environment. The body is covered with
scales or patches of horny, sometimes bony skin. Limbs are usually short or
absent, feet show many variations in form. Most reptiles are oviparous,
meaning that they produce external eggs. Representatives of reptiles include
lizards and snakes.
Amphibians are aquatic are four limbed. The
most common characteristic is an exposed, water permeable skin, rich in glands
which secrete mucus, which is sometimes poisonous. Amphibians lay small round
eggs protected by a gelatinous mass. Some species go through a larval stage
that metamorphoses into a juvenile, for example, a tadpole changes into a
frog.
There are two major types of fish, one
group called the bony fishes and the other cartilaginous fishes. All fishes
live in water and have external fertilization (with some exceptions).
Cartilaginous fish include sharks, rays, and lampreys. Bony include most of
your present day fishes like tuna, salmon, and goldfishes.
PROCEDURE:
This activity requires live animals,
which can be obtained or borrowed from a fellow teacher or by having students
bring in their small pets. There is always one student who owns a rabbit,
turtle, goldfish, hamster, guinea pig, mouse, or any other small animal.
Discuss the following vertebrates
characteristics with the students:
- vertebrates have an endoskeleton (internal skeleton) made of bone or
cartilage
-
vertebrates have a body with a head and trunk and many times a neck and tail
-
vertebrates have eyes, ears, and nostrils on the head
-
vertebrates also contain many highly developed systems associated with their
specialized organs. The systems include the muscular, skeletal, digestive,
respiratory, circulatory, excretory, nervous, and reproductive systems.
- Emphasize that humans are vertebrates.
In the laboratory activity have the students describe the different animals
that are brought to lab. On the lab sheet fill in the animal that is brought
in on the left-hand column and on the right have the students describe the
animal. You might want to develop a list of words that are more suitable for
the animals that you have. You may want to compare the position of each
animal's eyes, nose, and ears. Ask students to discuss why an animal looks the
way it does. The correct answers are not as important as is having the
children ask questions that compare and contrast the animals.
