BIO311D MIDTERM 3
Which of these causes the release of neurotransmitter molecules?
an action potential reaching the end of the axon
An example of a homeostatic response is
an increase in body temperature that results from involuntary shivering.
An exchange surface in direct contact with the external environment is found in the
lungs.
Homeostasis is the __________.
maintenance of a relatively constant and optimal internal environment
The overall function of the Calvin cycle is __________.
making sugar
Which of the following was an essential adaptive feature for the evolution of plants from water to the land?
minimizing the evaporative loss of water
From the superior vena cava, blood flows to the _____
right atrium Blood enters the right atrium from the superior and inferior venae cavae.
In a neuron, during the depolarization phase that may trigger an action potential _____.
some voltage-gated sodium channels are open
Where does the Calvin cycle take place?
stroma of the chloroplast
The space between an axon of one neuron and the dendrite of another neuron is called a(n) _____.
synaptic cleft
Neurons store neurotransmitter molecules in vesicles located within _____.
synaptic terminals
Which statement about human blood vessels is correct?
Pulmonary veins carry oxygen-rich blood to the heart. Following gas exchange in the lungs, the blood moves into the pulmonary veins for its return to the left atrium and then on into the highly muscular left ventricle.
Select the correct statement about feedback regulation in endocrine systems.
Some homeostatic control systems rely on pairs of negatively regulated hormone pathways, each counterbalancing the other.
Freshwater fish excrete nitrogenous wastes as __________.
ammonia
Hemolymph is found in the circulatory system of what kind of animal?
grasshopper
In which of the following animals are the circulatory fluid and interstitial fluid considered to be the same body fluid?
grasshoppers. Within an open circulatory system, such as that operating in insects, the body fluid, called hemolymph, bathes the organs directly as it is pumped between open spaces in the body.
The molar teeth of herbivorous mammals are especially effective at
grinding.
An animal body's automatic maintenance of a constant and optimal internal environment is termed
homeostasis.
Suppose you were walking to class when all of a sudden your friend jumped out and scared you! What would you expect to observe with your nervous system?
increased activity in the sympathetic division and decreased activity in the parasympathetic division
From the capillaries of the abdominal organs and hind limbs, blood flows to the _____.
inferior vena cava Blood enters the inferior vena cava from the capillaries of the abdominal organs and hind limbs.
Choose the list that presents the four stages of food processing in the order in which they naturally occur.
ingestion → digestion → absorption → elimination
From the pulmonary veins, blood flows to the _____.
left atrium Blood enters the left atrium via the pulmonary veins.
In their mechanism of action, a difference between lipid-soluble and water-soluble hormones is that __________.
lipid-soluble hormones bind to an intracellular receptor and this hormone-receptor complex binds to DNA Submit
The graph shows the body temperatures of two animals as a function of the environmental temperature. What might Animal 2 be?
lobster
Blood returns to the heart via the _____.
pulmonary veins Pulmonary veins carry oxygenated blood from the lungs to the left atrium.
The Pr form of the phytochrome pigment has maximum absorption in the __________ part of the spectrum.
red
The signaling molecule for flowering might be released earlier than usual in a long-day plant exposed to flashes of __________.
red light during the night
A countercurrent heat exchanger enables an animal to __________.
reduce the loss of body heat to the environment
Birds, insects, and many reptiles excrete nitrogenous waste in the form of uric acid, which __________.
reduces water loss compared to other nitrogenous wastes, but requires more metabolic energy to produce it
An animal's body maintains a relatively constant internal environment. How is this accomplished? It is surprisingly similar to the way a thermostat and heating system maintain a relatively constant temperature inside a room. The diagram below shows how a thermostat responds when the temperature becomes too hot or too cold. Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used.
1. This heating system maintains room temperature at or near a particular value, known as the set point 2. You open the window, and a blast of icy air enters the room. The temperature drops to 17 degrees Celsius, which acts as a stimulus to the heating system 3. The thermostat is a sensor that detects the stimulus and triggers a response. 4. The heater turns on, and the temperature in the room increases until it returns to the original setting. 5. The response of the heating system reduces the stimulus. This is an example of negative feedback. 6. The way this heating system maintains a stable room temperature is similar to the way an animal's body controls many aspects of its internal environment. The maintenance of a relatively constant internal environment is known as homeostasis.
Each muscle cell is in contact with a single motor neuron that controls the contraction of that cell. The diagram below shows a single muscle fiber and its motor neuron. Understanding the unique structural components of a muscle cell and its interaction with its motor neuron is a prerequisite for understanding muscle contraction and how it is regulated. Drag the labels to their appropriate locations on the diagram below.
A skeletal muscle cell is composed of a large number of contractile fibrils called myofibrils. The basic unit of contraction in a myofibril is a sarcomere. The sarcomeres are arranged end to end along the entire length of each myofibril. Each myofibril is partially surrounded by a specialized form of endoplasmic reticulum, called the sarcoplasmic reticulum. An action potential traveling along the motor neuron initiates an action potential in the muscle cell, which leads to muscle contraction. At the synaptic terminal of the motor neuron, an action potential causes the release of neurotransmitters, which subsequently trigger an action potential on the plasma membrane of the muscle cell. This action potential is propagated deep into the muscle cell via the T (transverse) tubules. In the interior of the cell, the action potential initiates changes in the sarcoplasmic reticulum.
Myosin heads have binding sites for __________.
ATP and actin
Which lung structure is a tiny sac that functions as an interface between air and blood?
Alveolus.
Select the correct statement describing feedback control in animals.
An animal may be a regulator for one environmental variable but a conformer for another.
The diagram below shows the five main transport proteins that control the distribution of Na+ and K+ ions across the plasma membrane of an axon. Assume that the membrane is at resting potential---the membrane potential of the axon remains constant at about -70 mV. Drag the arrows onto the diagram to show the direction of Na+ (gray arrows) and K+ (red arrows) movement through each transport protein at resting potential. If no ions move through a transport protein at resting potential, leave that target blank.
At resting potential, the membrane potential remains constant at about -70 mV. This means that there is no net movement of ions across the membrane. Assuming that Na+ and K+ are the only ions that move at resting potential, Na+ movement out of the cell through the sodium-potassium pump is balanced by an influx of Na+ through the non-gated Na+ channels. Conversely, K+ movement into the cell through the sodium-potassium pump is balanced by an outward movement of K+ through the non-gated K+ channels.
Suppose that an artificial non-gated K+ channel could be inserted into the plasma membrane of an axon at resting potential (membrane potential = -70 mV). Assume that the axon has not recently produced an action potential. What would happen when an artificial K+ channel is inserted into an axon membrane at resting potential?
At resting potential, the pumping of K+ ions into the cell by the sodium-potassium pump is balanced by the movement of K+ ions out of the cell through non-gated K+ channels. If an artificial K+ channel is inserted into the membrane at resting potential, K+ ions will also move out of the cell through that channel. The K+ ions moving through the artificial channel move along their concentration gradient, but against the membrane potential. The K+ movement further decreases the positive charge inside the cell, so the membrane potential becomes more negative (hyperpolarization).
Identify the role(s) of ATP in muscle contraction.
Binds to myosin to break an actin-myosin cross-bridge Provides the energy to convert myosin to a form that forms a cross-bridge with actin
Both plants and animals respond to environmental stimuli. Identify the correct statement(s) about this response.
Both plants and animals have physiological cycles called circadian rhythms. The molecular processes determining how plants and animals perceive environmental changes are often homologous. The molecular processes determining how plants and animals perceive environmental changes are equally complex.
The immediate function of digestion is...
Breaking down macromoledules into smaller monomers
What is the basic role of CO2 in photosynthesis?
CO2 is fixed or incorporated into organic molecules.
Select the correct statement about cellular respiration.
Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level.
Inhalation and exhalation move air into and out of the lungs. What happens when you inhale and exhale? Drag the labels to the correct locations on the flowchart to identify the steps of inhalation and exhalation
During inhalation, the diaphragm and rib muscles contract, increasing the volume of the lungs. Air enters the nose or mouth and flows down the trachea, bronchi, and bronchioles, and into the alveoli. During exhalation, the diaphragm and rib muscles relax, decreasing the volume of the lungs. Air leaves the alveoli and flows up the bronchioles, bronchi, and trachea, and exits through the nose or mouth.
How do endotherms and ectotherms differ?
Endotherms and ectotherms differ in the means by which they regulate their body temperature. Submit
True or false? The driving force for the unloading of oxygen from hemoglobin into tissues is the difference in PCO2 levels between the blood and body tissues.
False The PCO2 levels affect the diffusion of carbon dioxide; the driving force for the diffusion of oxygen from hemoglobin into tissues is the difference in PO2 levels between the blood (100 mm Hg when oxygenated) and body tissues (40 mm Hg at rest).
Compare the dissociation curves of the two hemoglobins in the graph. How does the dissociation curve for fetal hemoglobin compare to that for maternal hemoglobin?
Fetal hemoglobin has a higher affinity for oxygen than maternal hemoglobin at any partial pressure of oxygen. Submit
Which hypothesis best explains this difference?
Fetal hemoglobin's higher affinity for oxygen helps promote the movement of oxygen from mother to fetus.
Consider this diagram of blood circulation in a fish. Which of the following describes the path taken by oxygen-rich blood?
From the gills to the body tissues
Gas exchange involves the transport of two respiratory gases, oxygen and carbon dioxide. Review how each gas is transported between the atmosphere and the cells of your body by completing this exercise.
Gas exchange provides the body's cells with oxygen, which is needed for cellular respiration. Oxygen diffuses from the alveoli to capillaries in the lungs. Almost all the oxygen in the blood is bound to hemoglobin. Oxygen is carried all over the body and diffuses from blood to body tissues. Gas exchange also removes carbon dioxide, a waste product of cellular respiration, from the body. Carbon dioxide diffuses from body tissues to blood. Carbon dioxide is transported either in the plasma, bound to hemoglobin, or in the form of bicarbonate. In the lungs, carbon dioxide diffuses from the capillaries into the alveoli. When you exhale, carbon dioxide leaves the body.
Gas exchange involves the transport of two respiratory gases, oxygen and carbon dioxide. Review how each gas is transported between the atmosphere and the cells of your body by completing this exercise. Drag each statement into the appropriate bin depending on whether it applies to oxygen only, carbon dioxide only, or both oxygen and carbon dioxide.
Gas exchange provides the body's cells with oxygen, which is needed for cellular respiration. Oxygen diffuses from the alveoli to capillaries in the lungs. Almost all the oxygen in the blood is bound to hemoglobin. Oxygen is carried all over the body and diffuses from blood to body tissues. Gas exchange also removes carbon dioxide, a waste product of cellular respiration, from the body. Carbon dioxide diffuses from body tissues to blood. Carbon dioxide is transported either in the plasma, bound to hemoglobin, or in the form of bicarbonate. In the lungs, carbon dioxide diffuses from the capillaries into the alveoli. When you exhale, carbon dioxide leaves the body.
Many people have a tendency to gorge on rich, fatty foods. How could such a preference have evolved?
In ancestral hunter-gatherer communities, individuals with a tendency to gorge on such foods when available would have had a selective advantage.
Which statement regarding the mammalian heart is correct?
In the adult heart, blood in the right chambers of the heart cannot enter the left chambers without passing through the lungs.
Which statement about the gas exchange system in fish is correct?
It enables oxygen to diffuse from the water into the blood over the entire length of the gill capillaries
The Casparian strip in plant roots is correctly described by which of the following?
It ensures that all water and dissolved substances must pass through a cell membrane before entering the stele.
Which of the following statements correctly describe(s) T tubules and their role in conducting action potentials in muscle cells?
T tubules are infoldings of the plasma membrane that encircle the myofibrils and are in contact with the sarcoplasmic reticulum. T tubules carry action potentials into the interior of the muscle cell via voltage-gated Na+ and K+ channels. Without T tubules, the muscle cell would not be able to contract.
Select the most accurate statement describing the basic function of the light reactions of photosynthesis.
The basic function of the light reactions of photosynthesis is the conversion of solar energy to chemical energy.
Tunas, sharks, penguins, and dolphins all have a basic fusiform shape, tapered at both ends. What explains this similarity in shape?
The similarity is due to convergent evolution, because all these animals share similar environmental challenges.
Which three statements are true of blood flowing through a capillary at the location marked by the green circle?
The water surrounding the blood has a low concentration of oxygen. Oxygen diffuses from the water into the blood. Dissolved oxygen in the blood is lowest at this point.
The partial pressure of oxygen at a particular point in the bloodstream is 100 mm Hg. Under what circumstance will there be a net diffusion of oxygen from the water into the bloodstream at this location?
There will be a net diffusion of oxygen from the water into the bloodstream only if the partial pressure of oxygen in the water is greater than 100 mm Hg.
An advantage of excreting nitrogenous wastes as urea rather than as ammonia is that
Urea is less toxic than ammonia.
Why are action potentials usually conducted in one direction?
Voltage-gated Na+ channels are inactivated during the refractory period.
Consider a plant that grows best in bright sunlight in which seed germination is controlled by phytochromes. Which of the following statements describe(s) the structure and function of phytochromes in this plant?
When a phytochrome in the Pfr configuration absorbs far-red light, the phytochrome reverts to the Pr configuration. The plant seeds are more likely to germinate after exposure to red light than after exposure to far-red light. Phytochromes absorb red light maximally when the phytochrome is in the Pr configuration.
The diagram below depicts the transport of carbon dioxide in blood, from body tissues to the lungs. Drag the labels to their appropriate locations on the diagram.
With slight differences in the partial pressure of CO2, the body ensures that CO2 diffuses out of the tissues, into the blood, and then out of the body through the lungs. Most of the CO2 produced during cellular respiration is transported to the lungs in the form of bicarbonate ions in the blood. The incorporation of CO2 into bicarbonate ions lowers the partial pressure of CO2 in the blood, helping draw more CO2 out of the tissues. The incorporation of CO2 into bicarbonate ions in red blood cells roughly follows this process: CO2 reacts with water and forms carbonic acid, a reaction catalyzed by the enzyme carbonic anhydrase. Each molecule of carbonic acid (H2CO3) dissociates into a bicarbonate ion (HCO3 - ) and a proton (H+). Most of the bicarbonate ions diffuse into the blood plasma. (The protons, on the other hand, are bound by hemoglobin, which keeps them from causing a drop in blood pH. In this way, hemoglobin acts as a buffer.) When the blood reaches the lungs, the reverse of the above-described reactions takes place. Bicarbonate ions combine with protons, forming carbonic acid. Carbonic anhydrase catalyzes the conversion of carbonic acid back into CO2, which diffuses into the blood plasma and then into the alveoli, where it is exhaled through the lungs.
If a plant's stomata are closed and no transpiration is occurring, which of the following predictions is accurate?
Without transpiration, less water will be absorbed from the soil.
In a physiological system operating with positive feedback, __________.
a change in a variable will amplify rather than reverse the change
A biological cycle with a period of about 24 hours is called __________.
a circadian rhythm
Which of the following determines the direction of water movement across the membrane?
a difference in water potential
During mammalian labor and delivery, the contraction of uterine muscles is enhanced partly by the actions of oxytocin. This is an example of
a hormone that is involved in a positive feedback loop.
The semilunar valves of the mammalian heart
are able to prevent backflow of blood in the aorta and pulmonary arteries.
Most land-dwelling invertebrates and all of the amphibians
are ectothermic organisms with variable body temperatures.
A common feature of action potentials is that they __________.
are triggered by a depolarization that reaches threshold
Why has natural selection favored the evolution of double circulation in birds and mammals?
because they use more energy than equivalent-size reptiles and amphibians
If the membrane potential of a neuron decreases, the membrane potential _____.
becomes less negative.
During the contraction of a vertebrate skeletal muscle fiber, calcium ions _________.
bind with troponin, changing its shape so that the myosin-binding sites on actin are exposed Submit
An example of connective tissue is (are)
blood.
Bacteria in the human gut are which of the following?
both pathogens and mutualists
The smallest airway through which inspired air passes before gas exchange occurs in the mammalian lungs is the _____.
bronchiole
Which of the following terms describes metabolic pathways that break down complex molecules to release stored energy?
catabolic pathways
The binding of calcium to the troponin complex ________.
causes tropomyosin to shift position, exposing myosinbinding sites on actin
Hormones are __________.
chemical signals between cells, transported in blood or hemolymph
The photosynthetic membranes are found in the _____ in plant cells.
chloroplasts
The hypothalamus
controls most neuroendocrine signaling in mammals.
Where does glycolysis occur in animal cells?
cytosol
Homeostasis typically relies on negative feedback because positive feedback __________.
drives processes to completion rather than to a balance point
Negative feedback is a method of homeostatic control that __________.
ensures that conditions in an organism do not vary too much above or below their set points
Which barrier(s) must O2O2 and CO2CO2 cross to pass between air and blood inside lungs?
epithelial cells capillary wall extracellular fluid
The hydra is an example of an organism with a simple body plan that uses the same site for both digestion and nutrient distribution. What is the name of that site?
gastrovascular cavity
Sponges, cnidarians, and flatworms lack a specialized gas-exchange surface because
nearly all of their cells are in direct contact with the external environment.
The transpiration pull is due to the ________ that causes water to move up through the xylem that begins at the surface of mesophyll cells.
negative pressure potential
The four major categories of tissues are __________.
nervous, epithelial, connective, and muscle
What happens to pH and breathing rate during exercise?
pH decreases, which causes breathing rate to increase.
Preparation for the "rest and digest" response includes activation of the ________ nervous system.
parasympathetic
Interstitial fluid is
the fluid that surrounds body cells. Submit
An example of a properly functioning homeostatic control system is seen when
the kidneys excrete salt into the urine when dietary salt levels rise.
After the depolarization phase of an action potential, the resting potential is restored by
the opening of voltage-gated potassium channels and the closing of sodium channels.
Positive feedback differs from negative feedback in that
the positive feedback's responses are in the same direction as the initiating stimulus rather than opposite to it.
Where are neurotransmitter receptors located?
the postsynaptic membrane
Most types of communication between cells utilize
the release or reception of chemical signaling molecules.
Circulatory systems compensate for
the slow rate at which diffusion occurs over large distances.
Examine the figure. The countercurrent arrangement of the arterial and venous blood vessels causes
the temperature difference between the blood of the two sets of vessels to be minimized.
Metabolic rate is _____.
the total amount of energy an animal uses in a unit of time
Ions move in the direction opposite to that favored by the chemical concentration gradient when __________.
they are pumped by proteins that require ATP hydrolysis and when the electrical charge gradient repulses or attracts them
Cattle are able to survive on a diet consisting almost entirely of plant material because
they have cellulose-digesting, mutualistic microorganisms in chambers of their stomachs.
Which of the following is the most important result of the process of cellular respiration in biological systems?
transforming the energy in glucose and related molecules in a chemical form that cells can use for work
The nitrogenous waste that requires the most energy to produce is
uric acid.
Movement of xylem sap from roots to leaves __________.
usually depends on tension, or negative pressure potential
The cuticle on the surface of epidermis of leaves is an adaptation for plants to conserve
water.