The digestive and respiratory systems rely on the circulatory system for transporting nutrients, oxygen, and waste products in and out of the body. In order for the cells to function, it needs oxygen and nutrients. The respiratory system obtains oxygen and the circulatory system delivers it to the rest of the body.

On the other hand, the digestive system obtains and breaks down the food, while the circulatory system transports the nutrients to the cells throughout the body. In turn, carbon dioxide is eliminated by the body through the help of the respiratory system. Other solid waste products are eliminated from the digestive tract through the rectum.

When a rabbit spots a predator, its brain will interpret this information and the rest of the nervous system would signal and prepare the body for a threat. In turn, the musculoskeletal systems would be triggered to react to the stimulus that it received. This would cause the rabbit to exhibit a fight-or-flight response. It would try to protect itself by either fighting back or running away from the coyote.

During trials 9 and 10 on the first series, the time in which the mice were able to get the food has leveled out. On the other hand, the mean during the second series has increased during trials 9 and 10.

After the first set of trials, the scientists might have asked the following questions:
1. Would a second trial provide the same results as the first trial?
2. Would the mice still recognize the maze even if they are kept out of it for a certain period of time?
3. Would the mice stop responding to the stimuli if they are exposed to it for another series of trials?
4. Would the mice get quicker in reaching the food during the second trial?
5. How long would it take for the mice to retain their memories?

During the first series, the graph shows a downhill pattern. This indicates that the time has significantly decreased during the majority of the trials. The first trial started with 60 seconds and it ended with 10 seconds on the last trial.

On the other hand, the first trial during the second series started with 40 seconds. The mice were quicker during the second series. However, the graph has leveled out after a decrease in time. The time during the last trial on the second series is 10 seconds.

Here is a sample circle graph the represents the data from the reptile clade diversity table:

Here is a sample circle graph the represents the data from the reptile clade diversity table. (Click to see the graph)

The circle graph shows how each group of the reptile clade sums up to a whole. However, it does not really make an effective comparison between the parts. The slices that represent the number of species have very different sizes. In fact, there are very small slices in the circle graph, particularly the population of crocodilians and tuataras, that are very hard to read.

Since the goal of the data representation is not just to compare the parts to the whole but also to compare the relationship between the parts, it is also helpful to use a bar graph. This kind of graph makes it easier to illustrate the comparison of the number of species between the reptile clades.

Aside from using a circle graph to compare the parts that sum up to the whole reptile clade diversity, a bar graph can also be helpful in illustrating the relationship between the parts. In just one glance, you can immediately see the differences between each category.

Aside from using a circle graph to compare the parts that sum up to the whole reptile clade diversity, a bar graph can also be helpful in illustrating the relationship between the parts. In just one glance, you can immediately see the differences between each category. (Click to see the bar graph)

To classify whether a vertebrate is a fish, an amphibian, a reptile, a bird, or a mammal, these steps can be done:

1. Observe the organism and determine if it exhibits the characteristics of a fish.
a. has jaws and paired fins
b. lives in the water
c. has gills
d. covered in scales
e. cold-blooded

2. Observe the organism and check if it exhibits the characteristics of an amphibian.
a. has four limbs (short forelimbs and long hind limbs)
b. covered in moist, slimy skin
c. lives in moist habitats
d. reproduces unshelled eggs
e. metamorphic: begins life in water and move to the land when it matures
f. cold-blooded

3. Observe the organism and determine if it exhibits the characteristics of a reptile.
a. covered in tough and scaly skin
b. lives on land and breathes air
c. reproduces by laying amniotic eggs
d. some have four limbs and some have none
e. lacks external ears (eardrum is inside the head)
e. cold-blooded

4. Observe the organism and check if it exhibits the characteristics of a bird.
a. has feathers
b. has strong, lightweight bones
c. has modified limbs in the form of wings
d. has a beak
e. reproduces amniotic eggs
f. warm-blooded

5. Observe the organism and determine if it exhibits the characteristics of a mammal.
a. has four limbs
b. has hair or fur
c. has mammary glands
d. warm-blooded

A chordate ancestor, which gave rise to tunicates, lancelets, and hagfishes, are also related to vertebrates. Eventually, the notochord of chordates was replaced by vertebrae and produced the earliest vertebrate, which is the lamprey.

The next evolution was the appearance of jaws and paired appendages in sharks and other cartilaginous fishes. In turn, the cartilage developed into bones and produces bony fishes. Then, evolution caused the formation of lungs in fishes. This adaptation led the aquatic organisms to move onto land. Organisms developed four limbs, which helped them survive the terrestrial life. These changes led to the evolution of amphibians.

After some time, amphibians developed into animals the reproduce amniotic eggs. They are called reptiles. This evolution branched off into two groups of warm-blooded animals–birds, and mammals.

Segmentation is controlled by the genes that are responsible for the growth and development of body segments. The mutations in the genes often produce different forms of segments and increased the diversity among organisms. In this case, differentiated segments can perform varied functions, such as feeding, movement, or reproduction, and it can cause differences in the body structure of organisms.

When the body segments combine, both the internal and external parts fuse together. In this way, some organs become concentrated in a particular area. This evolution led to the specialization of organ systems, particularly cephalization. In cephalization, the sense organs and nerve cells become concentrated in the anterior part of the body or the head.