Answer Key- LO 2.3

1. Answer Key- LO 2.3 Which of the following best explains why energy cannot cycle through an ecosystem? A. The law of conservation of energy B. The second law of thermodynamics C. The competitive exclusion principle D. The green world hypothesis E. The principle of bio magnification Learning Log/ FRQ-style Question: An energy pyramid for a marine ecosystem is shown to the right. Label each trophic level of the pyramid and provide an example of a marine organism found at each level of this pyramid. Explain why the energy available at the top layer of the pyramid is a small percentage of the energy present at the bottom of the pyramid. An example of a marine organism in each trophic level is algae (producer), plankton (consumer), small fish (carnivore), shark (consumer). Energy transferred due to heat, work, and metabolic activities leaves only 10% of energy to the passed onto the next tropic level. This is called the 10% rule.

2. ANSWER KEY- LO 2.4 According to the data, the mice at 10°C demonstrated greater oxygen consumption per gram of tissue than did the mice at 25°C. This is most likely explained by which of the following statements? (A) The mice at 10°C had a higher rate of ATP production than the mice at 25°C. (B) The mice at 10°C had a lower metabolic rate than the mice at 25°C. (C) The mice at 25°C weighed less than the mice at 10°C. (D) The mice at 25°C were more active than the mice at 10°C. The metabolic rates of organisms determines how quickly energy is used up when at rest. Explain why some organisms must constantly consume food to maintain their metabolism and support themselves whereas some organisms can consume a large amount of food at one time and still maintain their metabolism over the course of weeks, such as in hibernation and estivation? An organism undergoes hibernation or estivation in order to avoid extreme conditions of heat or coldness. During hibernation, metabolism, oxygen consumption, and heart rate decrease drastically. In this hyper metabolic state, instead of using carbohydrates, it turns to lipids for energy production. Though very little energy is spent during hibernation/estivation, the most energy is spent during the waking period. Since many organisms can avoid such extreme cold/hot temperatures they don’t need to hibernate/estivate and must use their energy to maintain their body temperatures. Animals in hibernation often drop to extremely low core body temperatures in order to decrease its metabolic rate, allowing for survival over long periods of time.

3. Answer Key- LO 2.5 Multiple Choice: If the rubisco coding sequence were to be altered in a plant what process would be inhibited? • ATP production • Phosphorylation • Transcription • Carbon Fixation Free Response: The light from the sun first strikes the plant exciting an electron located in the thylakoid. The electron excites others in a chain reaction until a final electron is excited. This electron is captured by the primary acceptor which delivers the electron to an electron transport chain. The electrons are replaced by the breakdown of water. Once the electrons have traveled down the ETC they replace electrons which have already been excited in photosystem1 . After being excited at the photosystem 1 stage the electrons are captured again and travel down another ETC to NADP+. The NADP+ changes into NADPH and travels into the stroma. In the stroma rubisco fixes carbon from CO2 to 5 carbon chains. Once fixed the carbon chains get altered into 3 carbon sugars that are sent elsewhere in the plant. The NADPH helps alter the carbon chains by reducing them with phosphate groups. The remaining carbon chains are altered once more to be recycled as 5 carbon chains. Plants have adapted to live in areas where photosynthesis does not produce enough energy by producing enzymes that can break down other animals for nutrients such as the Venus fly trap. CAM plants have evolved to have the ability to store CO2 molecules during the night and store it for the day when photosynthesis takes place but its to hot for the stomata to be open, like pineapple plants. C4 plants have adapted to complete a fixation method in which a 4 carbon chain is formed thus preventing the process known as photorespiration, such as corn. Photorespiration is the process in which oxygen bonds to rubisco and becomes fixed on the 5 carbon chains which cannot be used to make sugars, thus wasting energy the plant needs.

4. Answer Key L.O- 2.10 Which of the following is a typical component in the plasma membrane of a eukaryotic cell? A) DNA B) mRNA C) tRNA D) Cholesterol E) Actin Describe the body’s immune response and how the cell membrane’s structure plays a part in it. When a helper T cell recognizes an antigen on an antigen presenting cell’s surface, it releases cytokines which are a cell to cell signal that is received by cytotoxic T cells and B cells. T cells then bind to the infected cell and recognize the invader via MHC and the T cell’s surface receptors. Cytotoxic T cells are then able to send out perforins which must go through proteins so that they are regulated and because they cant simply pass through the membrane. The purpose of the plasma membrane’s structure is the proteins that are imbedded into it. These proteins help cells recognize and sent signals to one another during the immune response. Cytotoxic T cells are also able to send out perforins which kill invaders via these channels.

5. Answer Key-LO 2.11 A lack of ATP would most directly impact the movement of_______. Water through a hydrophilic channel across the membrane. Hydrophobic molecules slowly diffusing across the lipid bilayer. Na+ through a sodium-potassium pump going against its concentration gradient. A solute moving diffusing passively through the membrane with the help of a transport protein. Suppose a paramecium cell was placed in a hypotonic solution. Describe the process by which water would pass through the hydrophobic plasma membrane. Also, hypothesize how the cell avoids being lysed in the hypotonic solution. Since the solution is hypotonic, water will diffuse through the membrane into the cell without energy from the cell. However, the water wouldn’t be able to diffuse along its concentration gradient without the help of membrane proteins. Many hydrophilic substances diffuse through membranes with the assistance of transport proteins, wither channel or carrier proteins. Water could flow through hydrophilic channel proteins known as aquaporinsto satisfy the concentration gradient. Water could also utilize a carrier protein which hold onto their passengers and change shape in a way that shuttles them across the membrane. Since the paramecium would be trying to pump water out of the cell against it’s concentration gradient, active transport would be required. The paramicium’s vacuole could actively pump stored water back across the membrane as water was diffusing inwards. Proteins in the membrane could hydrolyze ATP as an energy source to actively pump water out of the cell. The proteins use energy to change shape and move water across the membrane and against its concentration gradient.

6. LO 2.13 Answer Key M.C Question: In what order does the endomembrane system progress? a)Gogli, ER, Vesicle, Lysosome b)Lysosome, Vesicle, Golgi, ER c)ER, Vesiicle, Golgi Lysosome d) ER Golgi, Lysosome, Vesicle Free Response: The nucleus plays an important role in eukaryotic cellular formation, growth and other aspects explain the following; The difference between chromosome placement in prokaryotic vs. Eukaryotic cells. Why is it this way? And the importance of the nuclear envelope in eukaryotic cells. The nuclear envelope surrounds the nucleus and creates a barrier. It also serves as insulation to maintain the environment inside. The envelope consists of two nuclear membranes (inner and outer), nuclear pore complexes, and the lamina, a tough network. The nuclear membranes form an impermeable barrier. The first component, the outer membrane, faces the cytoplasm and is part of the endoplasmic reticulum. The second component, the inner membrane, faces the chromosomes. Movement into and out of the nucleus occurs through pores. Each pore is consisting of about a thousand proteins called nucleoporins. Each pore complex is large enough to accommodate the passage of ribosomal subunits, large protein-RNA complexes, which exit the nucleus after being assembled in the nucleolus. The third major component of the envelope, the nuclear lamina, is found in multicellular eukaryotes, but not in single-celled eukaryotes or plants. The lamina is a mesh of fibers, formed by the head-to-tail polymerization of proteins known as lamins. They are concentrated close to the inner membrane and extend through the inside of the nucleus. Lamins are a type of intermediate filament protein and are strong but also flexible. Different cell types, such as muscles and neurons , express different combinations of lamins.

7. Answer Key-LO 2.14 Some prokaryotic cells receive an extra piece of DNA through a process called conjunction. The DNA is called ? A) Granule B) Plasmid C) Nucleiod D) Transformation E) Nucleus Are there any real evidence that mitochondria and chloroplast were individual cells? If so, what are some similarities they share? Yes, the mitochondria and chloroplasts have their own genetic systems. They have their own DNA, which is not duplicated in the nucleus. That DNA contains a number of the genes which are necessary to make the materials needed for aerobic cellular respiration, or photosynthesis in the case of chloroplasts. Mitochondrial and chloroplast DNA molecules are naked and cellular, like prokaryotic DNA. These organelles also have their own population of ribosomes, which are smaller and simpler than the ribosomes out in the general cytoplasm. Mitochondria and chloroplasts also divide on their own, in a manner similar to the binary fission of prokaryotic cells.

8. ANSWER KEY– LO 2.15 A distinctive feature of the mechanism of action of insulin and glucagon is? The control of blood glucose levels through positive feedback loops. The antagonistic effects on blood glucose levels. The antagonistic effects on blood calcium levels Regulating blood glucose levels through their interactions with the nervous system and potassium. You are a doctor and a patient come in with the symptoms of diabetes mellitus. You decide to run a glucose tolerance test and have the patient drink a glucose containing solution and then every hour for four hours you check their blood glucose levels. What will the results show if the patient does not have diabetes mellitus? Why? Explain using feedback loops and the relationship between feedback loops and blood glucose. Negative feedback loops are a homeostatic control system that counteracts the reaction that was already in motion. Blood glucose levels are controlled by negative feedback loops. In a healthy person insulin causes body cells to take up more glucose and causes the liver to take in more glucose to store it as glycogen thus lowering the blood glucose levels. The negative feedback loop caused the onset of a rising blood glucose level to be counteracted by insulin causing the reduction of blood glucose levels. Since insulin and the negative feedback loop lowers blood glucose levels, it would be expected that if the patient did not have diabetes mellitus the their blood glucose levels would decrease every hour until homeostasis is restored.

9. Answer Key- LO 2.16 The pancreas stabilizes blood glucose levels by releasing insulin and glucagon, depending on whether blood glucose levels are too high or too low. Which of the following demonstrates a correct example of negative feedback in relation to blood glucose regulation? • Blood glucose levels rise and the pancreas releases glucagon in order to raise blood glucose levels further • Blood glucose levels fall and the pancreas releases insulin to lower blood glucose levels further • Blood glucose levels are homeostatic and the pancreas releases neither hormone • Blood glucose levels fall and the pancreas releases glucagon in order to raise blood glucose levels • None of these examples provide a correct example of negative feedback The human nervous system initiates a hormone pathway to regulate the metabolism. a) EXPLAIN this process and b) DESCRIBE how the process relates to negative feedback. • Metabolic regulation begins when external conditions stimulate the hypothalamus to release TRH. TRH binds to the anterior pituitary and stimulates the release of TSH. TSH then binds to the thyroid and stimulates the release of T3 and T4. T4 must be converted into T3 before it can become active, so T3 is the primary catalyzer of metabolism. T3 raises the metabolic rate of almost all the cells in the body. It also increases the breakdown of fat, stimulates protein synthesis and degradation, and stimulates the heart. • This process utilizes negative feedback because the anterior pituitary and hypothalamus both have receptors for excess T3 and T4. Once T3 and/ or T4 binds to these receptors, the hypothalamus and anterior pituitary become inhibited and the whole process stops. Specifically, the hypothalamus becomes unable to release TRH and the anterior pituitary becomes unable to release TSH. This is negative feedback because the products (T3 and T4) inhibit the production of themselves.

10. Answer Key L.O. 2.17 • M.C Question: Which of the following demonstrates a negative feedback loop? • A baby suckling on a mother’s nipple increases the flow of milk. • An enzyme substrate binding to that enzyme to inhibit the enzyme’s activity. • An enzyme substrate binding to that enzyme to stimulate the enzyme’s activity. • The pancreas releasing glucagon to lower the blood glucose level. • Describe 3 negative feedback loops the human body uses, how they are regulated, and what classifies them as negative feedback loops. On a regular basis the body uses negative feedback loops to regulate blood glucose levels, regulate enzyme activity and regulate metabolism in the thyroid. When blood glucose levels are too low, the pancreas senses that and releases glucagon to raise blood glucose levels. If they are too high, the pancreas releases insulin to lower them. In some enzymes, when the enzyme has produced enough substrate and that cell doesn’t need anymore the substrate will bind to a site on the enzyme changing the shape of the enzyme and keeps it from catalyzing any more reactions. The thyroid produces T3 and T4 to regulate the metabolism of food. If the thyroid has produced enough T3 and T4, the pituitary gland in the brain will sense this and stop producing TSH which will slow the production of T3 and T4 in the thyroid. All of these are negative feedback loops because as the stimulus increases, the response decreases.

11. ANSWER KEY- LO 2.18 Which of the following is not an example of Negative Feedback? A)Secretion of sweat while playing soccer B)Secretion of insulin to lower blood sugar level C)Contraction during pregnancy D)Secretion of glucagon to increase blood sugar level Negative Feedback allows homeostasis to be maintained. Explain how the alteration of feedback mechanisms could effect the production of hormones and describe one process in which a negative consequence could affect the homeostasis of the internal environment. Negative feedback occurs when a change in an environmental factor is regulated and triggers a response that counteracts the process to maintain a normal internal environment. When feedback mechanisms are disrupted deficiencies occur that cause responses to increase or decrease hormone responses. Diabetes Mellitus occurs when there is a deficiency of insulin that increases blood glucose levels. Insulin is regulated by feedback mechanisms to maintain a healthy blood glucose level. Glucagon and insulin operate simple endocrine pathways that maintain homeostasis; when glucose is at a high level insulin is released to lower blood sugar, when blood glucose is low glucagon is released to increase blood sugar. Negative consequences occur when a hormone can not be released to maintain the internal environment.

12. L.O. 2.19 M.C. Question: Which of the following statements is an accurate prediction of how a positive feedback loop ends? A)It slows down after a while to the point where it is producing reactions at a rate where the body can counter them so the body reaches homeostasis. B) It keeps going because it is always getting triggered by outside stimuli. C) It will eventually reach a point where it produces a counter-signal to stop or suppress the loop. D) The loop abruptly ends after the set amount of reactions have occurred. E) Mr. Mercer sends the Amish to build a log cabin around it so the positive feedback loop can’t move anymore. • FRQ-style Question: Name two advantages of positive feedback loops in mammals, and how these are activated, and two possible disadvantages, relating the disadvantages to homeostasis. • Two advantages are in childbirth and blood clotting. Mammals almost exclusively give live birth, and the babies are born by first the head pushing against the cervix. This sends chemical signals to the brain to release oxytocin, which causes more contractions, further contracting and pushing the fetus towards the cervix, which releases more oxytocin which causes even more contractions. Another advantage is blood clotting. Injured tissue releases signals that activates platelets always in the blood. When these platelets are activated, they rapidly produce/activate more platelets, so that the blood clots in the specific area. Two disadvantages could be in temperature regulation and pH. If a dip in temperature caused the body to start heating itself up, and then the produced heat caused the body to increase it’s heat even more, the organism would eventually overheat too much and denature too many enzymes, killing it. If the a dip in pH caused the body to rapidly increase it’s basicity then the body would become too basic, also making the enzymes not work and killing the organism yet again.

13. ANSWER KEY– LO 2.20 M.C. Question: Which of the following statements regarding positive feedback is NOT true? A) Stimulation of the mammary gland causing lactation is an example of positive feedback. B) Most hormones are controlled by positive feedback mechanisms that include the pituitary gland. C) Oxytocin is a hormone secreted from the posterior pituitary gland. D) Positive feedback enhances responses to stimuli in an organism. Learning Log/FRQ-style Question: The hormone oxytocin is used to induce abortions. Define the type of feedback mechanism that is used in this process and explain in detail how this hormone would be used to induce abortions. The feedback mechanism that is used in this process is the positive feedback loop. A positive feedback loop involves the release of hormones that causes an amplified change. The stimulus is intensified rather than counteracted (like in a negative feedback loop). Oxytocin is released from the pituitary gland naturally during the process of childbirth. Oxytocin stimulates contractions during childbirth. When a baby pushes headfirst against its mother’s uterus, the pressure causes the release of oxytocin which causes contractions to occur. The contractions lead to more pressure on the uterus which in turn leads to more contractions (amplification of the response). This hormone could be used to induce abortion by injecting it into a woman who is pregnant and causing contractions to prematurely occur. The contractions would help clear out the uterus by moving fetus and placenta out of the body.

14. ANSWER KEY – LO 2.21 M.C. Question: A male has a thyroxine deficiency. What would you expect the likely outcome directly resulting of his condition, and what his body would do in order to compensate for the issue, and maintain stability? A) A reduction of blood flow due to vasoconstriction; His body will attempt to increase blood flow, produced by an increase in his heart rate, to prevent heat loss. B) A behavioral change; he will envelope himself in insulating materials, as his body feels cold, and shakes to gain more heat. C) An increase in bodily isolation; to compensate, his body sweats more often to maintain core temperature, and to prevent it from increasing. D) An increased in blood flow, resulting from vasodilation; the body will increase intake or production of Calcium ions to force the body to constrict blood vessels, increasing internal heat. Learning Log/FRQ Style Question: Two organisms live in the same conditions, one is endothermic, a fox, while the other ectothermic, a lizard. The temperature of their environment increases, due to climate change. What you expect the animals to do in order to maintain optimal internal temperature? Will they undergo the same mechanisms and actions under homeostasis? Why? It is said that ectothermic animals save more energy in the attempt to regulate temperature. How is this statement true? Explain. In the situation, where an endothermic and endothermic organism, where to experience a change in external conditions, regarding temperature increase, the two animals will not undergo the same actions to maintain optimal conditions. Because the ectothermic organism can not regulate it's temperature itself, as of the endotherm, the lizard will seek shade to prevent its body from getting too hot, while the dog will pant to keep cool. The ectotherm relies on the environment to maintain temperature, while the endotherm has a bodily reaction, while also using environmental factors. The statement, suggesting that ectothermic organism save more “energy” in comparison to endothermic ones, because they do not undergo bodily reactions, and will not use any ATP or energy providing molecule or substance in order to keep cool, or heat up, thus saving energy.

15. Answer Key-LO 2.22 Which hypothesis will test the effect of biotic factors on plant growth? A. If the soil is acidic, then plants will not grow well. B. If two kinds of corn seeds are planted, then one will grow better than the other. C. If an insect is placed on a plant, then it might eat the plant. D. If the plants are crowded, then they will not grow well. Give examples of human actions that could expand a species’ distribution by changing its (a) biotic Interactions and (b) abiotic factors. (a) Humans could change a species’ biotic interactions by eliminating a predator in the area such as a sea urchin in an aquatic biome. (b) When humans put out forest fires that occur naturally in wooded areas it changes the distribution of trees in that ecosystem and affects species like the Red-cockaded Woodpecker. The lack of forest fires allows the trees to build up in population which isn’t the best nesting situation for the woodpecker which causes a decrease in reproduction. But if the forest fires occur the tree population decreases and the woodpeckers are once again reproducing.

16. Answer Key – LO 2.24 Which of the following are important abioticfactors that can affect the structure and organization of biological communities? A) Amount of light, soil pH, availability of nutrients B) precipitation, wind, temperature C) predation, competition, disease D) A and B E) All of the Above Learning Log Answer: Identify and discuss two abiotic factors and two biotic factors that could cause a specific variation of animal populations in a location. One abiotic factor that would cause animal changing location to suit its needs would be the temperature of the environment. If an animal lives in a temperature that is too hot to function effectively, it will move to a cooler location or possibly perform its work at night when the temperature is lower. Another abiotic factor would be the precipitation of an area. If an area has an higher precipitation level, it will cause a different variety of animal to live there than if the area were dry. A biotic factor that would effect the location of an animal would be the presence of predation in an area. The predators of a certain environment may hunt down the animal and so that animal will want to change locations to avoid the killing of its population. Another biotic factor would be the presence of a disease in one area. If the population is dying out due to an disease in the area, the animals will migrate to a place where they are not susceptible to diseases.

17. Answer Key- L.O. 2.25 M.C. Question: The importance of endothermic thermoregulation in mammals is critical to avoid which of the following? Increased vasodilation and heat loss through the skin Denaturing of enzymes and loss of protein function Convection and heat loss with cooling of an organism Reduction in heat shock proteins Free Response Question: Describe how organisms obtain dynamic homeostasis through thermoregulation? Identify 2 specific adaptations that help regulate heat and why are these important to the organism. Organisms obtain dynamic homeostasis and thermoregulation through either endothermic or ectothermic regulation. Endotherms regulate their temperature through counter current heat exchanges within their bodies and do not have to rely on the environment around them. Counter current heat exchanges send warm blood through the arteries and transfers some of this heat over to the cooler vein. The venous blood travels in the opposite direction back to the trunk of the body, the arterial blood provides warmth for it. As the blood being carried by the vein reaches the core of the body ,it is almost as warm as the core. This minimizes the heat loss in organisms who can internally regulate their temperature. In ectotherms, an organism must regulate body temperature based on the environment. There are four ways this can occur: Radiation ( waves of warmth absorbed by the organism), Evaporation ( which is removal of heat from surface os a liquid), Convection ( the movement of air or liquid by an organism which transfers heat), and Conduction ( the direct transfer of heat from an organism and an objects molecules). A major thermoregulatory adaptation in animals is insulation. This is associated with the integumentary system (fat, skin, and hair). Circulatory adaptations which include vasodilation and vasoconstriction which can increase or decrease blood flow to the superficial vessels and thus regulate the transfer of body heat to the environment.. Both of these mechanisms allow for dynamic thermoregulation to maintain a homeostatic to allow metabolic processes to function appropriately.

18. ANSWER KEY LO 2.26 • MC Question: In the diagram provided, which • of the following conclusions can be made about • these organisms? • Lizards have evolved from birds • Amphibians and anapsids are equally related to mammals • Birds and mammals share no common ancestor • Dinosaurs have the trait of laying amniote eggs • Amphibians do not classify as “tetrapods” In the cladogram, explain the relationship between amphibians and synapsid reptiles. What characteristics present on the diagram are shared between these two organisms? Also, suppose that a new fossil was discovered and classified to be a synapsid reptile. This fossil was shown to have wing bone structures, though they are structured very differently from the wings of a bird. These two organisms are the only ones present on the diagram that have wings. How could these structures be classified, and how is it possible that no other organism present has this structure? Amphibians are considered ancestors of synapsid reptiles as they are located to the left, or before, the synapsid reptiles, and they share the following traits: vertebrae, jaws, and tetrapods (these traits are found to the left of both organisms, indicating a shared trait). The wings of the birds and the newly discovered synapsid reptile are considered analogous structures, as they share a similar function (providing for flight) but both developed and evolved independently of one another. No other organism has this trait because they evolved independently due to natural selection and change in their environments.

19. Answer Key-LO 2.27 Which of the following is an example of homeostasis? A) Ectotherms that maintain a constant internal body temperature. B) Endotherms that maintain a constant internal body temperature. C) Lying in the shade to keep cool. D) Producing large amounts of urea. In cool weather, jackrabbits sometimes flatten their ears against their body. What is an advantage and disadvantage of this behavioral response? List 3 other regulatory mechanisms that the jackrabbit could use to maintain homeostasis/ body temperature. Jackrabbits do this to maintain homeostasis and body temperature because it is an endothermic animal. The flattening of the ears will regulate blood flow through the blood vessels. The ears would also be less subject to the cold and not be exposed on all sides. It is easiers for the heart to pump warm blood to the ears when the ears are laying down. A disadvantage would be the jackrabbit’s lack of hearing. The jackrabbit could also (1) sweat when hot to increase evaporative cooling. It could (2) shiver when cold to increase heat production through contraction and relaxation cycling in skeletal muscles. And the jackrabbit could (3)increase activity when cold to increase metabolic heat production.

20. ANSWER KEY– LO 2.28 What would be a result of the disruption? A. When the kidneys shut down, oxygen cannot be transported to the heart. B. Because the kidneys are unable to filter and maintain the balance of the fluids and minerals in the body, the body can no longer maintain the homeostatic levels in the body. C. The hormone receptors are signaling to the brain that the ph balance in the body is not at an equilibrium D. A positive feedback mechanism allows the fluid levels to be regulated. Diabetes causes a disruption in the balance blood glucose levels, describe the factors that are being affected, explain why this is a problem in maintaining homeostasis and how it can be treated. The pancreas is an organ that is part of the digestive system responsible for producing hormones to regulate blood glucose levels. Insulin is one hormone produced by special cells in the pancreas and is responsible for lowering blood sugar levels. When a person is affected with diabetes they are no longer able to produce the necessary insulin to lower blood sugar levels. Long term effects of high blood sugar is including kidney damage, neurological damage, cardiovascular damage, damage to the retina or damage to feet and legs. These problems can all be attributed to the disruption of the homeostatic balance of blood glucose levels because the insulin is either not produced in enough quantities or it is defective. It can be treated by eating a healthy diet in order to maintain prevent the blood sugar levels from rising, it can also be treated with medication to bring the blood sugar levels back to their homeostatic balance.

21. L.O. 2.29 A patient is admitted to a hospital with tumors rapidly metastasizing in his body almost as if the body could not control it. The patient became ill with the flu while at the hospital as well but managed to fight it off rather quickly. Why was his immune response effective for one and not the other? • A) immunoglobulins are attacking the antibodies that target cancerous cells • B) the MHC protein is not able to bind with the cancerous antigen fragment • C) perforin secreted by the cytotoxic T cells does not effect the cancerous cells • D) Both B and C • FRQ Answer • When antibodies are secreted by B cells, they bind to the epitopes of the antigen and destroy them. One mechanism of destruction is phagocytosis. The antibody activates and send a signal to macrophages and the macrophages then engulf the antigen, effectively destroying it. Another way antibodies can shut down an antigen is through neutralization. The antibody is able to block the viral binding sites so that the antigen can not infect any new cells so it dies. After the first response to a foreign invader a stockpile of memory B and T cells is produced. During the second exposure these memory cells are able to produce antibodies and signal the rest of the immune system much faster than before. This creates a quick, efficient response that effectively destroys the antigen; most of the time before harmful effects occur.

22. Secretions from the skin and mucous membranes also contain antimicrobial proteins. One such protein is/are… A)Lysozyme-invade microorganisms B)Macrophages-engulf and then digest C)Lysozyme-enzyme that digest the cell walls of bacteria D)Lymphocytes-produces immune responses Histamine is a protein that the immune system uses to help protect the body’s cells against infection. The immune system is the body’s natural defense against illness and infection. If the immune system detects a harmful foreign object, such as bacteria or a virus, it will release histamine into nearby cells. The histamine causes small blood vessels to expand and the surrounding skin to swell. This is known as inflammation. What happens in a cellular level when inflammation happens and when would it be necessary to block the histamine protein? The expansion of the blood vessels allows an increased number of infection-fighting white blood cells to be sent to the site of the infection. The swelling of the surrounding skin also makes it harder for an infection to spread to other parts of the body. Histamine is usually a useful protein, but if you're having an allergic reaction it's sometimes necessary to block its effects. Allergic reactions occur when your immune system mistakes a harmless substance, such as pollen, as a threat. The release of histamine causes the process of inflammation to begin and leads to nearby tissue becoming red and swollen. It can also affect the nerves in the skin, making the skin feel itchy. Answer Key: LO 2.30

23. Answer Key LO 2.33 • Which of the following can cause apoptosis to occur? • The removal of ineffective immune system cells • The formation of body organs within the embryo • The production of abnormal cells within the body • The maintenance of the number of cells in adults • Suppose the DNA within a cell in your body mutated and will eventually become cancerous. Describe the process in which your body will take in order to perform apoptosis on that specific cell. • Within mammal cells, ligands will bind to the receptors of the cell to send a pro-apoptotic signal to the cell. The cell then starts shrinking and forms blebs. Proteins are activated at this time to break down cellular components. Enzymes then break down the nucleus and the cell emits signals to attract macrophages. The cell then breaks into several pieces containing the cell components and destroyed nucleus. Macrophages will recognize these parts and remove the mutated/cancerous cell pieces from the body.

24. Answer Key L.O. 2.34: • Which of the following statements concerning concentration gradient’s effect on membrane transport activity is false? A)Equilibrium is achieved by solute’s tendency to move from areas of high concentration to areas of low concentration. B)Membranes are universally impermeable. C)Transport proteins act as the beginning of signal transduction pathways. D)None of the above. • Membranes are not universally impermeable; they are selectively impermeable and they use transport and integral proteins as receptors for ligands and other signals to bond. These allow an equilibrium to be achieved by the import and export of solutes in the cell. • Explain the importance of apoptosis in the development of multicellular organisms. Provide an example in the human body. • Apoptosis is programmed cell death (suicide). When apoptosis occurs, it can be preventative (like in the case of cancer cells) or it can be developmental (like in the formation of fingers on hands and the evolutionary removal of a vestigial tail). For apoptosis to occur, first a death signal must bind to the death signal receptor. Then, Ced9 is inactivated, relieving its inhibition of Ced-3 and Ced-4. Active Ced-3 triggers a cascade of reactions leading to activation of nucleases and proteases. The action of these enzymes causes the changes seen in apoptotic cells and eventual cell death. C. elegansare used as a model for apoptosis. Apoptosis is more complicated in mammals but involves proteins similar to those in the nematode.

25. Answer Key- L.O. 2.35 M.C. Question: Quorum sensing would most likely occur when: A bacterium senses the production of cAMP Tobacco plants are exposed to sunlight Bacteria reach a certain critical concentration Predator insects eat herbivorous insects Insulin binds to target cells FRQ: Describe the difference between long-day and short-day plants. How can a long-day plant be induced to bloom in the middle of winter? Photoperiodism is the response of an organism to seasonal changes in day length. In plants, photoperiodism usually influences the physiological changes required to initiate changes in leafing or blooming of flowers in angiosperms. A photoreceptor protein, called a phytochrome, is usually found in plants that respond to photoperiods. The phytochrome is responsible for absorbing light and often initiating a signal transduction pathway that induces a response. The flowering of long-day plants was initially thought to be stimulated by the length of daylight being longer than the critical photoperiod for that plant, although recent research suggests that a critical “night length” is responsible for the control of blooming. (Thus, ‘long-day’ plants may be more accurately referred to as ‘short-night’ plants.) In the same way, ‘short-day’ plants may be more accurately referred to as ‘long-night’ plants. A long-day plant may be induced to bloom in the middle of winter by interrupting the long nights of winter with a regular “flash” of light.

26. Answer Key- LO 2.38Which of the following statements is validas to why the ground squirrel will sacrifice itself to help other squirrels? A)The ground squirrels biological behavior indicates it is trying to attract a female.B)Every group of ground squirrels assigns one squirrel to do so in order to save the young and others.C)The ground squirrel learned a certain behavior in where he would sacrifice himself in order to save his family.D)When a ground squirrel acquires the behavior to sacrifice itself to a predator, the predator typically backs off because of the brave behavior.Suppose you have a species where a baby can prosper when being exiled from their biological mother. How can the baby survive? Where will it get the necessities to stay alive?An example used that has this similar problems are the blue-footed boobies. Some of the times the mother lays two baby eggs, only wanting to raise one. This is a problem, because it puts the two baby boobies at risk of one being thrown out. They typically have to fight each other, and most of the time it is the bigger and stronger one that prospers and injures the smaller. With the mother as a witness, not caring if one of her chicks die, it shows that the losingboobie doesn’t have a mother that will help it throughout its life. Some of the time, the boobie may crawl into another mother boobies next, leaving it to fight the child of hers. Mothers are not able to spot which chicks are and are not theirs. As long as the baby may prosper against the baby in the other nest, then he will live. Unfortunately some of the time the baby will die or starve.

27. L.O. 2.39 M.C. Question-When horses hear an unusual noise, they turn their ears toward the sound. This is an example of A. a fixed-action pattern. B. habituation. C. associative learning. D. imprinting. E. kinesis. A—This is a fixed-action pattern which is an innate behavior that is a programmed response to a stimulus that appears to be carried out without any thought by the organisms involved. Free response- Taxis is the random movement of an organism in response to a stimulus. Kinesis is movement towards or away from a stimulus when something in the environment changes, for example the organism is exposed to light, the organism will randomly move around until it encounters a favorable condition again. One example is when you flip open a rock, insects hiding under the rock will scatter to another rock. This behavior will insure that the organism will remain in an environment that maximizes its chances of survival. Since its activity will increase when met with an unfavorable environment and its activity will decrease when it is met with a favorable environment. The animal will stay in the most favorable environment for the longest time. Migration is the movement of a population from one area to another. Migration is usually caused by seasonal changes. For example, birds may migrate south, when the length of the day shortens. Migration improves the survivorship of an individual by ensuring that it is in a suitable environment. Birds who cannot survive the cold winters migrate south to a warmer area. They then migrate north when it in winter in the southern hemisphere. This ensures that they are always living in a relatively warm environment.