AP Biology Midterm Study Guide

							      AP BIOLOGY
     STUDY GUIDE
                      CREATED BY
                      EASY-NOTES




                                               Preface:
Thank you for purchasing the AP Biology Study Guide made by Easy-Notes! The purpose of this
study guide is to incorporate the experience of previous and current AP Biology students to
facilitate the learning of Biology for high school students. This study guide will provide detailed
explanations and tips for each test section which will be invaluable for quizzes, tests, midterms,
finals, etc. This study guide is for educational purposes only. Any dissemination or alteration of
this document without the written consent of Easy-Notes is subject to legal terms.
Section 1: The Respiratory System

Insects:
The respiratory system of insects is the tracheal system. The respiratory medium for insects is air.
In this system, air tubes branch throughout the body. The largest tube, called the tracheae opens
to the outside. All the body cells are close to air tubes, and diffusion occurs between the air tubes
and the body cells. Larger insects need to bring in more O2 and expel more CO2 than smaller
insects, so they ventilate their tracheal systems with rhythmic body movements. Hemocyanin is
found in arthropods and is their respiratory pigment. It binds copper to oxygen, giving t blood of
insects a blue color.

Practice question 1: Small insects bring in enough O2 and expel enough CO2 through diffusion
through the trachea to support cellular respiration.

Fish:
Gills are the respiratory surface and water is the respiratory medium for fish. Water as a
respiratory medium has advantages and disadvantages. The advantage of water as a respiratory
medium is the aqueous environment keeps the respiratory surface (the gills) moist. The
disadvantage of water as a respiratory medium is water has a smaller O2 concentration than air.
Water is also more dense than air. As a result, fish have a lower max metabolic rate than
mammals.

Practice question 2: Name one reason why gills are unsuitable for land animals.

Countercurrent exchange is the process of ventilation in fish. Blood flowing through the
capillaries of the gills gains O2 as the fish moves water over its gills. The countercurrent blood
flow maintains a lower concentration gradient of oxygen inside the capillaries which allows O2
to diffuse into the capillaries. This works because the blood from the capillaries is flowing in the
opposite direction that the fish is swimming. Therefore, oxygen poor blood that is returning to
the gills will continually be renewed with new oxygen.


Vertebrate Respiratory System in Humans:
In humans, the respiratory surface is the lungs and the respiratory medium is air. Unlike the
tracheal system that branches throughout insects, the circulatory system must connect the lungs
to the rest of the body. Diffusion of O2 into and CO2 out of the lungs occurs at the alveoli.

Practice question 3: What is the advantage of the alveoli being only one cell thick?

The medulla oblongata controls breathing. It detects changes in pH. CO2 increases cause a
decrease in pH (remember decreasing pH means it gets more acidic), causing chemoreceptors
to send messages to the diaphragm. As a result, breathing rate increases.
*remember CO2 is the gas monitered. NOT O2!

Pathway of air in humans:
1. Nasal Cavity or pharynx
2. Larynx
3. Trachea
4. Bronchus
5. Bronciole
6. Alveoli
7. Pulmonary vein
8. Left atrium


Mammals breath by negative pressure breathing. Mammals ventilate their lungs by pulling air
into their lungs. The diaphragm, a muscle under the ribs contracts, and causes the rib cage to
expand. When the diaphragm contracts the air pressure of the alveoli gets lower (as the volume
of the lungs increases, so does air pressure) than the atmospheric pressure. Air moves from areas
of higher pressure to an area of lower pressure.
*TIP: Think of a vacuum cleaner. When you turn it on, the bag expands, and air moves from the
outside into the inside of the vacuum cleaner.

Hemoglobin is the respiratory pigment of nearly all vertebrates is hemoglobin. Unlike
hemocyanin, hemoglobin is red. It has four subunits, each with a heme group that has an iron
atom in the center. One oxygen molecule binds to one heme group. Cooperativity occurs here;
once one O2 binds to one subunit, all the other subunits go through a conformational change,
making it easier for O2 to bind. O2 is loaded into hemoglobin in the lungs, and unloaded in the
tissues. Hemoglobin with O2 attached is called oxyhemoglobin. CO2 can also bind to the
multiple amino groups of hemoglobin. This is called carboxyhemoglobin.

Practice Question 4: Which cells contain hemoglobin?


Challenge questions:
1. Which of the following has the highest O2 concentration?
       a. inhaled air
       b. exhaled air
       c. blood entering the alveolar capillaries
       d. blood leaving the alveolar capillaries.
       e. blood entering tissue capillaries.

2. The respiratory pigment of insects is:
        a. hemoglobin
        b. oxyhemoglobin
        c. carboxyhemoglobin
        d. hemocyanin

3. How many O2 molecules can bind to 1 hemoglobin?
      a. 1
      b. 2
      c. 3
       d. 4
       e. 5

Practice Questions:
1. True
2. Sample answer: Without the aqueous environment, the gills would dry out.
3. Allows for diffusion to occur much more quickly than if it was thicker.
4. Red blood cells

Challenge Questions:
1. a
2. d
3. e
Section 2: The Circulatory System

Types of circulation:
Gastrovascular cavities- Digests and distributes nutrients throughout the body of hydras and
cnidarians.

Open circulatory system- Blood and interstitial fluid are separated. This fluid is called
hemolymph. The heart(s) pump hemolymph into sinuses where chemical exchange occurs
between hemolymph and body cells. Open circulatory systems are in insects and arthropods.
Advantages of an open circulatory system are less energy costly because of their low hydrostatic
pressures and need less energy to maintain because they have no blood vessels.

Closed circulatory system- Blood is separate from interstitial fluid. Blood is kept in vessels.
Earthworms, squids, octopuses, and all vertebrates have this circulatory system. The advantage
of a closed circulatory is they can have higher blood pressure, allowing more faster transport of
blood.


Closed circulatory systems of vertebrates:
Fish- hHve a two chambered heart. Only one circuit of blood flow. Blood is pumped to the
capillaries where it receives O2. Then, it goes to the capillaries of the fish's body.

Amphibians- Have a three-chambered heart with two circuits (pulmocutaneous and systemic).
There is one ventricle, so there is some mixing of O2 rich and O2 poor blood. Double circulation
occurs here.

Reptiles- Have a three-chambered heart with a septum partially dividing the ventricle. They have
a pulmonary circuit and a systemic circuit. This allows less mixing of blood than amphibians.
Double circulation occurs here.

Mammals- Have a four-chamber heart with two atria and two ventricles. There is no mixing of
O2 rich and O2 poor blood. There is a pulmonary circuit and systemic circuit. Double circulation
occurs here.

Mammalian circulation. (starting in the right ventricle)
1. right ventricle
2. pulmonary artery
3. capillaries of the lungs
4. pulmonary vein.
5. left atrium
6. left ventricle
7. aorta
8. capillaries above the aorta (head and forelimbs) and below the aorta (abdominal organs and
hind limbs)
9. Posterior or Anterior Vena cava
10. right atrium