Essay - AP Free Response 2009
Many organisms require a continuing source of oxygen for respiration. Discuss important structural and physiological adaptations for oxygen uptake in THREE of the following:
Using your text book and the Internet
for help, answer the questions below.
Respiratory System :
All eukaryotic organisms are dependent upon a source of Oxygen to insure that cellular respiration can make adequate ATP available for the cell. Single cell organisms or organisms that are comparitively usually do not have a respiratory system. Diffusion through the skin or plasma membrane provides all the O2 that is needed. Some very active microorganisms enhance gas exchange simply by circulating water across their surfaces like the larva shown below.
Earthworms are not very active but do have a fair amount of girth. Their moist skin provides sufficient surface area for gas exchange. Their circulatory system absorbs oxygen from the skin and transports it throughout the body. lExtremely active multicellular organisms or multicellular organisms with substantial thickness will require the presence of a respiratory system to insure rapid exchange of O2 & CO2. these systems must have:
Some organisms, like the starfish, have numerous extensions from their skin that offers substantial surface area and promotes gas exchange. Small pincher like structures (pedicellaria) are also present to keep the "skin gills" clean of debris. Organisms that live out of water tend to have their respiratory systems located inside their body in order to keep their gas exchange surfaces moist. Insects have numerous tracheal tubes that run throughout the inside of their body. The tracheal tubes open to the air through tiny pores, generally on the sides of the abdomen, called spiracles.
Air contains much higher concentrations of oxygen than water. Even with this, when a fish is taken out of the water it soon suffocates. Their are numerous tiny filaments associated with the fish gill that establishes an immense gas exchange surface area. When out of water these filaments are no longer suspended and the filaments clump together decreasing the surface upon which gas exchange can occur.
Fish protect their gills from silt and debris with a cover on the side of their head called the operculum. Water is pumped over their gills by positive pressure. Their mouth opens wide and fills with water. The mouth closes and narrows forcing water over the gills and out underneath the operculum flaps on the sides of the head.
For some fish, such as tuna, the pumping system is less efficient, so they have to swim constantly to keep water moving over their gills. By swimming quickly, at least 65 centimeters (about 2.1 feet) per second, the fish can force enough water over their gills. In addition, the surface area of tuna fish's gills is up to 30 times larger than that of other fish to make up for their reduced pumping efficiency. Many species of fish never stop swimming their entire life. To do so would mean suffocation.
1- Suppose your were told a new species of animal was discovered and it had no respiartory system or circulatory system. What might you conclude about this organsism size based on this information?
2- Why are earth worms commonly seen in large numbers out from under the ground after a heavy rain?
3- Why would you expect to see few starfish (if any) in very shallow tidepools (a tide pool is trapped water left behind during low tide)?
4-Why do fresh water fish tend to congregate next to rocks or under rock ledges and fallen trees immediately after heavy rain falls?
5- Why are frogs able to hibernate underwater at the bottom of a pond?
6- List two reasons why birds tend to have much more rapid throat expansion and contraction (panting) when hot?
Mammals have perhaps the most well developed respiratory system. We will look at the hman respiartory system as an example. The human respiratory system establishes all the necessary requirements for efficient gas excahnge.
Breathing through the nasal passage warms, moistens, and filters the air before it enters the system. warm moist air enhances gas exchange. Filtering out particulate matter in the mucus mebranes of the sinuses limits the accumulation of debris on gas exchange surfaces.
Using the mouth to breathe can allow larger volumes of air to enter during levels of high activity.
The epiglottis folds over the air passage (trachea) during swallowing to prevent food from entering the respistory system
Trachea have numerous cartilage rings to insure that it does not collapse with inhallation.
Cilliated epithelium lining the major airways forces particulate matter, stuck in the thin layer of mucus on the surface of the passageway, back up to the mouth for removal.
The tiniest passageways (bronchioles) terminate in clusters of microscopic air sacs called Alveoli. Each cluster of alveoli is serviced by its own cappilary bed (see diagram below). The lung is not a bag on the end of a tube, it is a mass of millions of tiny air sacs.
A muscle, the diaphragm, draws air into and forces air out of the respiratory system
7- Why do all smokers eventually develop the characteristic "smokers cough"?
8- How might mouth breathing in humans lead to impaired gas exchange in the alveoli?
The transport of gasses by the blood is made more efficient in many ways:
Hemoglobin in the red blood cells increases the carrying capacity of oxygen hundreds of times greater than plain water.
CO2 that diffuses into the blood enters red blood cells where an enzyme converts the CO2 into bicarbonate ions (HCO3-). Converting the CO2 into Bicarbonate ions increases the carrying capacity of CO2 molecules.
In addition, formation of bicarbonate ions offers the body an effective method of regulating blood pH. CO2 will react with water to produce carbonic acid. If carbonic acid were to increase (which can occur as a result of increased cellular activity) blood pH would lower which could effect enzyme activity. The fact that red blood cells convert CO2 into Bicarbonate ions, which are basic, enables the body to mainatin a constant pH in the blood.See a movie showing the formation of bicarbonate ions
12- The brain is constantly monitoring blood chemistry. What changes to the circulatory and respisrtory systems might be made by the brain in response to a lowering of blood pH?
The human respiratory system establishes all the essential characteristics needed to maintain efficient gas exchange