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					VERTEBRATE ADAPTATIONS - Found in the Bio 203 Lab Manual – Pg 329

An ADAPTATION is a trait that an organism possesses that helps that organism to be more successful at surviving
and/or reproducing. For example, primates, including ourselves, possess tiny ridges on their palms and soles
(fingerprints) which enable them to hold onto tree branches better. Primates who did not possess these ridges
would tend to fall out of trees and into the jaws of lions earlier in life than those with ridges. Thus, those individ-
uals with ridges would likely live longer and produce more offspring, eventually becoming more numerous in the
population. These ridges are an adaptation for tree climbing. Much of biology is concerned with the study of the
evolution and utility of adaptations. Another example is the thick layer of insulating fat in marine mammals, an
adaptation for living in cold water. Plants have adaptations, too, such as thorns to ward off herbivores, and leaves
with large surface areas to capture more sunlight for photosynthesis. These are examples of MORPHOLOGICAL
(shape-related) adaptations. There are also physiological and behavioral adaptations. Sweating is a physiological
adaptation to prevent extremely high body temperatures. Building nests in high trees might be a behavioral
adaptation of birds, thwarting ground-dwelling egg eaters such as rodents and coyotes.

What are some of the adaptations that you have inherited? Are they behavioral, morphological or physiological?

Exercise 1
Most of the vertebrates you will look at this week may be found in New Mexico. In some cases you will look at
the organisms, in other cases you will look at their skeletons.

Lab Study A: Adaptations for Locomotion
Two groups of vertebrates have developed adaptations that allow them to truly fly (not just glide through the air).

Examine the bat skeleton and the bird skeleton located in the lab. Pay special attention to the forelimbs of the
skeletons. Both of these forelimbs are modified for flight. Are the modifications convergent adaptations? _______

Examine the pictures of bats in flight, and watch the birds or examine the bird wings.

Explain why the different features seen in the forelimb skeleton are adaptive for the bat.

For the bird.

Find the frog skeleton and the live frog located in the lab. Examine the hind limbs of these specimens.

In what ways do bats and frogs use similar adaptations for locomotion?

Examine the bird skeleton and locate the large keel on the breast bone. Compare the breast bone of the bird to the
breast bone of the human skeleton and the frog skeleton. The keel is designed to provide attachment for very large
flight muscles.
How does the position of the keel affect the bird’s center of gravity?

Compare the bird neck region and back region of the vertebral column to that of the cat. Offer an explanation for
the differences you see.

Watch the snake located in the lab as it moves about its cage. Snakes lack limbs but have no difficulty moving;
they can even climb trees. Snakes move by contracting muscles in rhythmic patterns along the length of their

One type of movement is called concertina movement. Your T.A. will demonstrate this movement by allowing
the snake to crawl through a tube that is nearly the same diameter as the snake. Do not handle the snake

Watch the snake’s movement and describe it.

Notice the scales on the underside of the snake’s body. These are called scutes; they assist the snake in moving
along any surface.

Snakes also move by serpentine motion. Watch the snake move about its cage and describe serpentine motion.

Lab Study B: Adaptations for Feeding
Locate the fish in the live tank. All of these species are native to the Rio Grande or Pecos River systems. Each
species lives in a particular habitat and has adaptations that fit them into that habitat. Not all habitats are
represented in the tank.

Look closely at the fish. Certain fish have a more streamlined shape than others. Their streamlined shape allows
water to flow past them with a minimum of resistance. The broader, blunter fish stay in slower-moving water.

How might these variations in shape help fish avoid competition for food?

Notice the location of the mouths of the fish. Some of the fish have mouths that are more ventrally located. Where
do these fish probably feed?
Examine these bottom feeders. Notice that they have a very streamlined shape. This fish is naturally found in
riffles and scrapes algae from the rocks that are located there.

Notice the small fish that swim near the top of the tank. Notice how flat their upper profile is. Notice the location
of their mouths. These fish feed by catching mosquito larvae and other prey from the surface of the water.

Explain how their shape and the location of their mouths are adapted to this kind of feeding.

Compare the top and bottom feeders to the other fish in the tank. What adaptations can you identify that would
reduce competition for food with those species you have already considered?

Examine the series of skulls located in the lab. These skulls show many adaptations for specialized feeding and
ways the animal interact with its environment. The teeth of vertebrates are especially adapted to different feeding
strategies and can tell us much about the animals feeding habits.

Look at the alligator skull. Notice the placement of the eye sockets and nostrils. How is the skull's overall shape
adapted to where alligators live and how they hunt?

Notice the teeth. These are adapted to catching and holding prey. The jaws of the alligator are not designed to
chew prey like mammals so it must swallow its prey whole or shake it into smaller pieces which can then be

Describe the alligator teeth.

Examine the rattlesnake skull. Snakes swallow their prey whole.

Compare the skulls of the snake and the alligator.

Does the snake skull have the heavy structure that would allow crushing and shaking prey apart?
Unlike the alligator skull, the snake’s skull is very flexible. The joints of the jaws and the bones which hold the
jaws onto the rest of the skull in a living snake are highly flexible. The upper and lower jaws on each side of the
head can move independently of each other to “walk” along a prey item and assist in swallowing.

Examine the teeth. Rattlesnakes have two specialized fangs. These teeth are designed to fold back when the
snake’s mouth is closed. The fangs are hollow and are associated with a duct of specialized salivary glands.

What advantage does the folding up of the fangs provide for the rattlesnake?

The salivary glands associated with the fangs produce enzymes that begin digesting a prey item as soon as the
fangs inject them into the prey. This is the poison for which rattlesnakes are known. Other enzymes are
specialized to kill or immobilize prey.

Why is it adaptive for rattlesnakes to be able to kill or immobilize prey in this manner?

Rattlesnakes often lose a fang during a strike or while feeding and these lost teeth are replaced.

Examine the other teeth located in the snake skull. Notice their shape. How is this shape adaptive to the snake’s
mode of eating its prey?

In mammals, four basic kinds of teeth are recognized: incisors, canines, premolars and molars.

INCISORS are generally chisel-shaped teeth that are used for nipping. A human biting an apple or a horse cropping
grass use their incisors. In some herbivores, such as cattle and deer, incisors are only found on the lower jaw.
They use their prehensile tongues and mobile lips to draw vegetation across the incisors which cut the vegetation
like a tape dispenser cuts tape. Rodents have very stout incisors that can be used for gnawing. These incisors grow
continually as they are worn away at the tips. Incisors can also be used for pinching. A dog biting fleas or carrying
a pup illustrates how they are used in this capacity.

CANINES are usually used to catch, hold and kill prey. In hogs and some primitive deer the canines are very long
and can be used for fighting.

PREMOLARS and MOLARS are cheek teeth used for a variety of functions. These teeth are greatly modified to fit
the diet of different animals. In some mammals, molars and premolars are specially adapted to crushing or
grinding mollusks, meat, soft vegetation, tough grasses, hard-bodied insects, worms and plankton. In other
mammals, the anterior molariform teeth are suited to shearing and the hind molariform teeth are suited to crushing
and grinding.

Examine the antelope or deer skull. Describe the incisors.

Describe the molars.
Describe the canine teeth. Explain why this might be.

Notice how long the skull is. There is a long space in the jaw where there are no teeth at all.

What advantage might grazers gain from having a long rostrum? Are their eyes set high enough to detect

Examine the skull and photograph of the vampire bat. These bats have specialized incisors that are used to make a
cut from which they take blood. Describe the incisors.

Vampire bats evolved with large mammals in the tropics of Central and South America. When cattle were
introduced to the areas where these bats lived, the population of bats exploded.

Examine the fox skull and the cat skull. These animals are both carnivores: both eat meat as a main part of their
diet. Canids (dog, fox, etc.) also eat insects and vegetation.

Examine how the anterior molariform (cheek) teeth of carnivores move over each other. Compare this movement
with that of the herbivore skull. What are carnivore molariform teeth designed to do?

Notice the placement of the eye sockets in the carnivore skulls. These predators have good forward vision and
depth perception. Why is that adaptive?

Examine the raccoon skull. Notice the molariform teeth. Raccoons eat a variety of things but they have a
preference for insects and crayfish. Compare the teeth of the raccoon to that of the cat.

Examine the skulls labeled 1 through 4. Using the information about teeth provided above, identify what type of
diet each animal probably had and defend your answer.

 Skull        Probable Diet                                         Explaination
Examine the pig skeleton located in the lab. Pigs use their snouts to dig up roots and underground vegetation.
Their bodies are adapted to allow them to use their snouts like a plow.

Compare the shape of the back of the skull to that of the human and the cat. The high ridges on the back of the pig
skull are sites that allow placement of very large muscles used for lifting the head.
Compare the spines on the vertebrae located between the shoulder blades of all three skeletons. Notice how long
and broad the spines of the hog are compared to the other two. These spines are the sites where the large lifting
muscles are also attached.

Examine the bones of the forelimbs (arms) of all three skeletons. Look at the olecranon process (elbow). The
pig’s very long elbow allows very large muscles to help brace the front limbs against the force caused by the
plowing action of the pig's snout.

Identify any other adaptations of the forelimbs of the pig that would help strengthen them.

Examine the cat skeleton. We know cats are carnivores. Besides the teeth, what other adaptations can you identify
that might help in catching prey? (Why have so many bones in the vertebral column?)

Lab Study C: Adaptations for Reproduction
Examine the fish in the live tank again. Your T.A. will point out some of the silvery fish and some with bright red
fins; these are the same species. The fish with the bright red fins are males, while the silvery fish are females. The
apparent differences between sexes of the same species is called SEXUAL DIMORPHISM.

Red shiners reproduce using external fertilization. Eggs are laid in an appropriate substrate and fertilized there.

Notice the interactions between the red individuals compared to interactions between the red and silvery
individuals. Watch these fish for a few minutes, and then describe what occurs.

Identify two ways in which the red shiner males seem to use their color.

Examine the small Gambusia. These are live bearers. Instead of laying eggs in a nest to be fertilized, they are held
in the mother until they hatch. This requires internal fertilization.

Watch these small fish closely for a few minutes. Look at their anal fins. Some of the fish have two long, narrow
fins; fish with these fins are males. The males can use these fins as a pseudopenis to inject sperm into the female’s
cloaca to fertilize the eggs she holds.

Aside from the difference of the anal fins, do you see any other apparent examples of sexual dimorphism between
the male and female Gambusia? ________ Explain.

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