Chordate Characteristics
All chordates must display *all characteristics at some point in their lifetime:
✏ Notochord (for support)
✏ Dorsal hollow nerve cord
✏ Pharyngeal gill slits
✏ Post anal tail
✏ Notochord (for support)
✏ Dorsal hollow nerve cord
✏ Pharyngeal gill slits
✏ Post anal tail
Lower Chordates
Three Subphylums
Hemichordata:
✏ Primitive gill slits
✏ Marine
✏ Lack notochord (some do not consider them chordates because of this)
Example animal: Acorn Worm
Urochordata/Tunicata:
✏ Exhibits all chordate characteristics
✏ Adults are filter feeders and do not resemble a chordate (at all) - it has no dorsal nerve cord nor notochord
✏ Larvae are highly motile - This stage is mainly for species distribution and lasts 1-2 days
Example animal : Tunicate
Cephalochordata: "Classical Chordate"
✏ Exhibits all chordate characteristics in adult stage
✏ Believed to share a common ancestor with the vertebrates
Example animal: Amphioxus
✏ Primitive gill slits
✏ Marine
✏ Lack notochord (some do not consider them chordates because of this)
Example animal: Acorn Worm
Urochordata/Tunicata:
✏ Exhibits all chordate characteristics
✏ Adults are filter feeders and do not resemble a chordate (at all) - it has no dorsal nerve cord nor notochord
✏ Larvae are highly motile - This stage is mainly for species distribution and lasts 1-2 days
Example animal : Tunicate
Cephalochordata: "Classical Chordate"
✏ Exhibits all chordate characteristics in adult stage
✏ Believed to share a common ancestor with the vertebrates
Example animal: Amphioxus
Lower Chordata Lab
Lab Analysis:
1. How are these three organisms similar and different?
All three organisms are lower chordates. However the Acorn Worm lacks a true notochord and post anal tail, the Tunicate has all the true characteristics in its larval stage and the amphioxus has all four characteristics in its adult stage, which earns it the name of "The Classical Chordate".
2. Why is Amphioxus called the “Classical Chordate”?
The Amphioxus is called the "classical chordate" because it is the first organism to display all four chordate characteristics in its adult form.
3. How does a tunicate larva compare to an adult tunicate?
A tunicate larva is very small and highly motile. This stage is very short and used for species dispersal, normally lasting one to two days. Larvae also have a nerve chord and notochord which it then loses in its adult stage. As an adult the tunicates are sessile and reproduce.
4. Why is the Acorn worm not considered an invertebrate worm?
The tunicate isn't considered an invertebrate worm because it developed a dorsal nerve chord and gill slits which make it more similar to the lower chordates than the invertebrates.
1. How are these three organisms similar and different?
All three organisms are lower chordates. However the Acorn Worm lacks a true notochord and post anal tail, the Tunicate has all the true characteristics in its larval stage and the amphioxus has all four characteristics in its adult stage, which earns it the name of "The Classical Chordate".
2. Why is Amphioxus called the “Classical Chordate”?
The Amphioxus is called the "classical chordate" because it is the first organism to display all four chordate characteristics in its adult form.
3. How does a tunicate larva compare to an adult tunicate?
A tunicate larva is very small and highly motile. This stage is very short and used for species dispersal, normally lasting one to two days. Larvae also have a nerve chord and notochord which it then loses in its adult stage. As an adult the tunicates are sessile and reproduce.
4. Why is the Acorn worm not considered an invertebrate worm?
The tunicate isn't considered an invertebrate worm because it developed a dorsal nerve chord and gill slits which make it more similar to the lower chordates than the invertebrates.
Higher Chordates
Subphylum Vertebrata
Class Osteichthyes Lab: Perch Dissection
Class Amphibia Lab: Frog Dissection
Lab Analysis:
1.What is the function of the nictitating membrane?
A semi transparent third eyelid. It is there to protect and keep the eye moist while still being able to see.
2. A frog does not chew its food. What do the positions of its teeth suggest about how the frog uses them?
It uses its teeth to hold rather than chew its prey.
3. Trace the path of food through the digestive tract.
Tongue-> mouth-> pharynx-> esophagus-> stomach-> small intestine-> large intestine-> cloaca
4. Trace the path of blood through the circulatory system, starting at the right atrium.
Deoxygenated blood from the body enters into the right atrium. This blood mixes with oxygenated blood from the left atrium in the ventricle. This semi-oxygenated blood is pumped out of the heart aorta to the lungs or rest of the body.
5. Trace the path of air through the respiratory system.
Internal or external nares-> past the glottis-> bronchi-> sac-like lungs
6. Trace the paths of sperm in a male and eggs in a female.
In males, sperm is produced in the testes then travels down through the ureters and into the cloaca. In females eggs are formed in the ovaries then travel down the oviducts down the uterus and into the cloaca.
7. Trace the path of urine in both sexes.
The kidneys filter metabolic wastes from the blood. This "urine" then travels down the ureters and into the bladder from then it travels down to the cloaca from where the urine is released.
8. Which parts of the frog’s nervous system can be observed in its abdominal cavity and hind leg?
Spinal nerves are observed in the hind leg which are connected to the spinal cord in the abdominal cavity.
9. Suppose in a living frog the spinal nerves extending to the leg muscles were cut. What ability would the frog lose? Why?
The frog would lose the ability to control the muscles in its legs and wouldn't be able to move. This makes them sitting ducks which is not ideal -> since this isn't best fit to the environment there is a very high chance that they will fall prey to another animal and get eaten.
10. The abdominal cavity of a frog at the end of hibernation season would contain very small fat bodies or none at all. What is the function of the fat bodies?
To provide energy for "good eggs" ,as insulation from the cold, and to help them float in water.
11. Structures in an animal’s body that help it survive in the environment are called adaptations. How do the frog’s powerful hind legs help it survive in water and on land?
On water, their powerful hind legs are very efficient at swimming. While on land, their legs also give them the ability to quickly jump away from predators or to catch their prey.
12. During one mating, the female lays between 2,000 & 3,000 eggs in water and the male sheds millions of sperm over them. How do these large numbers relate to the frog’s ability to survive in water?
Since there are abundant numbers of eggs hatching there is a higher chance that more will survive in the water without protection from their parents.
1.What is the function of the nictitating membrane?
A semi transparent third eyelid. It is there to protect and keep the eye moist while still being able to see.
2. A frog does not chew its food. What do the positions of its teeth suggest about how the frog uses them?
It uses its teeth to hold rather than chew its prey.
3. Trace the path of food through the digestive tract.
Tongue-> mouth-> pharynx-> esophagus-> stomach-> small intestine-> large intestine-> cloaca
4. Trace the path of blood through the circulatory system, starting at the right atrium.
Deoxygenated blood from the body enters into the right atrium. This blood mixes with oxygenated blood from the left atrium in the ventricle. This semi-oxygenated blood is pumped out of the heart aorta to the lungs or rest of the body.
5. Trace the path of air through the respiratory system.
Internal or external nares-> past the glottis-> bronchi-> sac-like lungs
6. Trace the paths of sperm in a male and eggs in a female.
In males, sperm is produced in the testes then travels down through the ureters and into the cloaca. In females eggs are formed in the ovaries then travel down the oviducts down the uterus and into the cloaca.
7. Trace the path of urine in both sexes.
The kidneys filter metabolic wastes from the blood. This "urine" then travels down the ureters and into the bladder from then it travels down to the cloaca from where the urine is released.
8. Which parts of the frog’s nervous system can be observed in its abdominal cavity and hind leg?
Spinal nerves are observed in the hind leg which are connected to the spinal cord in the abdominal cavity.
9. Suppose in a living frog the spinal nerves extending to the leg muscles were cut. What ability would the frog lose? Why?
The frog would lose the ability to control the muscles in its legs and wouldn't be able to move. This makes them sitting ducks which is not ideal -> since this isn't best fit to the environment there is a very high chance that they will fall prey to another animal and get eaten.
10. The abdominal cavity of a frog at the end of hibernation season would contain very small fat bodies or none at all. What is the function of the fat bodies?
To provide energy for "good eggs" ,as insulation from the cold, and to help them float in water.
11. Structures in an animal’s body that help it survive in the environment are called adaptations. How do the frog’s powerful hind legs help it survive in water and on land?
On water, their powerful hind legs are very efficient at swimming. While on land, their legs also give them the ability to quickly jump away from predators or to catch their prey.
12. During one mating, the female lays between 2,000 & 3,000 eggs in water and the male sheds millions of sperm over them. How do these large numbers relate to the frog’s ability to survive in water?
Since there are abundant numbers of eggs hatching there is a higher chance that more will survive in the water without protection from their parents.
Class Mammalia Lab: Rat Dissection
Lab Analysis:
2. The sphincter is a circular muscle. Why is it this shape and what does it do?
The sphincter is a circular muscle that is at the beginning and end of the large intestine. This muscle controls the movement of water/food. The help with pushing food through the system and preventing backflow.
3. Why is there a difference in the diameter and length of the small and large intestine?
The small intestine is very long to maximize the surface area of absorption of nutrients. Since the large intestine receives the wastes from the small intestine as well as water that it need to absorbed it is fairly big to provide room for all this.
4. The liver is the largest organ in the body (after the skin), what are its functions?
Produces bile that helps digest food fats. It also detoxifies the body.
5. In each of the cavities there is a membrane that covers both the wall of the cavity and the organ it contains, what is the function of these membranes?
These membranes house capillaries which take the oxygenated blood and nutrients (where necessary) to the skin, muscles and all the organs.
6. What is the function of the spleen?
Removes/ Destroys old red blood cells and creates white blood cells
7. What is the function of the diaphragm?
To assist the lungs in respiration. When at rest it pushes on the lungs -> we exhale. When we inhale the diaphragm expands allowing more room for our lungs to take in air.
8. What distinguishes the atria from the ventricles?
The atria receive blood from the lungs and the rest of the body and pass it over to the ventricles who then pump the blood tot the rest of the body.
9. Why is the wall of the left ventricle of the heart thicker than that of the right?
The left ventricle pumps blood to the whole body while the right ventricle only pumps blood to the lungs which is a much shorer distance. Therefore the left ventricle is much thicker and muscular to allow the ventricle to effectively pump blood tot eh entire body.
10. What similarities exist between the male and female reproductive systems?
They are both connected to the excretory system.
11. What do the kidneys do?
Filters metabolic waste from the blood and produces urine.
2. The sphincter is a circular muscle. Why is it this shape and what does it do?
The sphincter is a circular muscle that is at the beginning and end of the large intestine. This muscle controls the movement of water/food. The help with pushing food through the system and preventing backflow.
3. Why is there a difference in the diameter and length of the small and large intestine?
The small intestine is very long to maximize the surface area of absorption of nutrients. Since the large intestine receives the wastes from the small intestine as well as water that it need to absorbed it is fairly big to provide room for all this.
4. The liver is the largest organ in the body (after the skin), what are its functions?
Produces bile that helps digest food fats. It also detoxifies the body.
5. In each of the cavities there is a membrane that covers both the wall of the cavity and the organ it contains, what is the function of these membranes?
These membranes house capillaries which take the oxygenated blood and nutrients (where necessary) to the skin, muscles and all the organs.
6. What is the function of the spleen?
Removes/ Destroys old red blood cells and creates white blood cells
7. What is the function of the diaphragm?
To assist the lungs in respiration. When at rest it pushes on the lungs -> we exhale. When we inhale the diaphragm expands allowing more room for our lungs to take in air.
8. What distinguishes the atria from the ventricles?
The atria receive blood from the lungs and the rest of the body and pass it over to the ventricles who then pump the blood tot the rest of the body.
9. Why is the wall of the left ventricle of the heart thicker than that of the right?
The left ventricle pumps blood to the whole body while the right ventricle only pumps blood to the lungs which is a much shorer distance. Therefore the left ventricle is much thicker and muscular to allow the ventricle to effectively pump blood tot eh entire body.
10. What similarities exist between the male and female reproductive systems?
They are both connected to the excretory system.
11. What do the kidneys do?
Filters metabolic waste from the blood and produces urine.