Split (1)

test · 389k rows

questions stringlengths 37 1.22k	reasoning stringlengths 0 3.56k ⌀	answers stringlengths 4 138
Molecules move from an area of high concentration to an area of lower concentration until an what is met? Here are the choices: A. freezing point B. respiration C. equilibrium D. oxidation	Molecules move from an area of high concentration to an area of lower concentration until an equilibrium is met. The molecules continue to cross the membrane at equilibrium, but at equal rates in both directions.	C: equilibrium.
What type of layers do animals' tissues develop from? Here are the choices: A. embryonic B. transgenic C. dermic D. cytoplasm	32.1 Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers.	A: embryonic.
Vectors along the same line can be what to one another like ordinary numbers? Here are the choices: A. taken B. noted C. added D. lost	Components along the same axis, say the x-axis, are vectors along the same line and, thus, can be added to one another like ordinary numbers. The same is true for components along the y-axis. (For example, a 9-block eastward walk could be taken in two legs, the first 3 blocks east and the second 6 blocks east, for a total of 9, because they are along the same direction. ) So resolving vectors into components along common axes makes it easier to add them. Now that the components of R are known, its magnitude and direction can be found. Step 3. To get the magnitude.	C: added.
As a cell grows, its volume increases more quickly than its what? Here are the choices: A. density B. surface area C. age D. weight	As a cell grows, its volume increases more quickly than its surface area. If a cell was to get very large, the small surface area would not allow enough nutrients to enter the cell quickly enough for the cell’s needs. This idea is explained in Figure below . However, large cells have a way of dealing with some size challenges. Big cells, such as some white blood cells, often grow more nuclei so that they can supply enough proteins and RNA for the cell’s requirements. Large, metabolically active cells often have lots of cell protrusions, resulting in many folds throughout the membrane. These folds increase the surface area available for transport of materials into or out of the cell. Such cell types are found lining your small intestine, where they absorb nutrients from your food through protrusions called microvilli .	B: surface area.
What is the term for an antibody that inappropriately marks self-components as foreign? Here are the choices: A. rogue antibody B. autoimmune antibody C. autoantibody D. compromised antibody	Try your hand at diagnosing an allergic reaction by selecting one of the interactive case studies (http://openstaxcollege. org/l/world_allergy) at the World Allergy Organization website. Autoimmunity Autoimmunity is a type of hypersensitivity to self-antigens that affects approximately five percent of the population. Most types of autoimmunity involve the humoral immune response. An antibody that inappropriately marks self-components as foreign is termed an autoantibody. In patients with myasthenia gravis, an autoimmune disease, muscle-cell receptors that induce contraction in response to acetylcholine are targeted by antibodies. The result is muscle weakness that may include.	C: autoantibody.
What type of orbit do the planets make in the solar system? Here are the choices: A. figure eight B. vertical C. elliptical D. conical	Earth and the other planets in the solar system make elliptical orbits around the Sun.	C: elliptical.
In which part of the ear are the vibrations amplified by the malleus, incus, and stapes? Here are the choices: A. inner ear B. outer ear C. middle ear D. major ear		C: middle ear.
What landform occurs most often along plate boundaries? Here are the choices: A. geysers B. dunes C. volcanoes D. sinkholes	Volcanoes occur most often along plate boundaries.	C: volcanoes.
Which type of glaciers form several unique features through erosion, including cirques, arêtes, and horns? Here are the choices: A. valley glaciers B. line glaciers C. icebergs D. deep glaciers	Glaciers cause erosion by plucking and abrasion. Valley glaciers form several unique features through erosion, including cirques, arêtes, and horns.	A: valley glaciers.
What are the strongest chemical bonds? Here are the choices: A. weak and ionic bonds B. covalent and ionic bonds C. mutual and stock bonds D. curvature and ionic bonds		B: covalent and ionic bonds.
Bacteria break down the remains of digested food through a processed called what? Here are the choices: A. oxidation B. regulation C. fermentation D. synthesis	Behind each release of gas is an army of gut bacteria undergoing some crazy biochemistry. These bacteria break down the remains of digested food through fermentation, creating gas in the process. Learn what these bacteria have in common with beer brewing at http://youtu. be/R1kxajH629A?list=PLzMhsCgGKd1hoofiKuifwy6qRXZs7NG6a .	C: fermentation.
What is the term for the process in which water vapor changes to tiny droplets of liquid water? Here are the choices: A. dispersion B. vaporization C. diffusion D. condensation	Some elements have been known for centuries (gold, silver, iron, copper, among others) while others have been created in the lab only within the last several years. Most elements do not exist as such in nature. They are so reactive that they can be found only in combination with other materials.	D: condensation.
Specialized features of populations of galápagos finches inspired what theory? Here are the choices: A. evolution by reaction B. evolution by force C. evolution by natural selection D. evolution by isolation	Demonstrations of evolution by natural selection can be time consuming. One of the best demonstrations has been in the very birds that helped to inspire the theory, the Galápagos finches. Peter and Rosemary Grant and their colleagues have studied Galápagos finch populations every year since 1976 and have provided important demonstrations of the operation of natural selection. The Grants found changes from one generation to the next in the beak shapes of the medium ground finches on the Galápagos island of Daphne Major. The medium ground finch feeds on seeds. The birds have inherited variation in the bill shape with some individuals having wide, deep bills and others having thinner bills. Large-billed birds feed more efficiently on large, hard seeds, whereas smaller billed birds feed more efficiently on small, soft seeds. During 1977, a drought period altered vegetation on the island. After this period, the number of seeds declined dramatically: the decline in small, soft seeds was greater than the decline in large, hard seeds. The large-billed birds were able to survive better than the small-billed birds the following year. The year following the drought when the Grants measured beak sizes in the much-reduced population, they found that the average bill size was larger (Figure 11.4). This was clear evidence for natural selection (differences in survival) of bill size caused by the availability of seeds. The Grants had studied the inheritance of bill sizes and knew that the surviving large-billed birds would tend to produce offspring with larger bills, so the selection would lead to evolution of bill size. Subsequent studies by the Grants have demonstrated selection on and evolution of bill size in this species in response to changing conditions on the island. The evolution has occurred both to larger bills, as in this case, and to smaller bills when large seeds became rare.	C: evolution by natural selection.
In the equation for pressure, how is force expressed? Here are the choices: A. meters B. pounds C. teraflops D. newtons	In the equation for pressure, force is expressed in newtons (N) and area is expressed in square meters (m 2 ). Therefore, pressure is expressed in N/m 2 , which is the SI unit for pressure. This unit is also called the pascal (Pa) . It is named for the scientist Blaise Pascal, whose discovery about pressure in fluids is described later in this lesson. Pressure may also be expressed in the kilopascal (kPa), which equals 1000 pascals. For example, the correct air pressure inside a mountain bike tire is usually about 200 kPa.	D: newtons.
The radiocarpal and midcarpal joints are responsible for all movements of the hand and what other part of the body? Here are the choices: A. fingers B. wrist C. shoulder D. foot	The carpal bones form the base of the hand. This can be seen in the radiograph (X-ray image) of the hand that shows the relationships of the hand bones to the skin creases of the hand (see Figure 8.8). Within the carpal bones, the four proximal bones are united to each other by ligaments to form a unit. Only three of these bones, the scaphoid, lunate, and triquetrum, contribute to the radiocarpal joint. The scaphoid and lunate bones articulate directly with the distal end of the radius, whereas the triquetrum bone articulates with a fibrocartilaginous pad that spans the radius and styloid process of the ulna. The distal end of the ulna thus does not directly articulate with any of the carpal bones. The four distal carpal bones are also held together as a group by ligaments. The proximal and distal rows of carpal bones articulate with each other to form the midcarpal joint (see Figure 8.8). Together, the radiocarpal and midcarpal joints are responsible for all movements of the hand at the wrist. The distal carpal bones also articulate with the metacarpal bones of the hand.	B: wrist.
Psip can be positive or negative relative to what kind of pressure? Here are the choices: A. magnetic B. atmospheric C. inertia D. manometric		B: atmospheric.
Lava erupts through long cracks in the ground, also called what? Here are the choices: A. ridges B. faults C. crevasses D. fissures	At divergent plate boundaries hot mantle rock rises into the space where the plates are moving apart. As the hot mantle rock rises, it goes from higher to lower pressure. This is because there is no longer the weight of all the rock above it. Lower pressure lowers the melting temperature of the rock (2 in the previous section). This is why there is volcanism at divergent plate boundaries. Lava erupts through long cracks in the ground, or fissures.	D: fissures.
What is the smallest aromatic hydrocarbon? Here are the choices: A. phosphate B. benzene C. furan D. sulfide	Unsaturated hydrocarbons called aromatic hydrocarbons are cyclic hydrocarbons that have double bonds. These compounds have six carbon atoms in a ring with alternating single and double bonds. The smallest aromatic hydrocarbon is benzene, which has just one ring. Its structural formula is shown in the Figure below . Larger aromatic hydrocarbons consist of two or more rings, which are joined together by bonds between their carbon atoms. The name of aromatic hydrocarbons comes from their strong aroma, or scent. That’s why they are used in air fresheners and mothballs. You can learn more about these interesting hydrocarbons at this URL:.	B: benzene.
Which type of tree loses its leaves each fall and remains leafless in the winter? Here are the choices: A. conifer B. deciduous C. annual D. perennial	Temperate Forests Temperate forests are the most common biome in eastern North America, Western Europe, Eastern Asia, Chile, and New Zealand (Figure 20.18). This biome is found throughout mid-latitude regions. Temperatures range between –30oC and 30oC (–22oF to 86oF) and drop to below freezing on an annual basis. These temperatures mean that temperate forests have defined growing seasons during the spring, summer, and early fall. Precipitation is relatively constant throughout the year and ranges between 75 cm and 150 cm (29.5–59 in). Deciduous trees are the dominant plant in this biome with fewer evergreen conifers. Deciduous trees lose their leaves each fall and remain leafless in the winter. Thus, little photosynthesis occurs during the dormant winter period. Each spring, new leaves appear as temperature increases. Because of the dormant period, the net primary productivity of temperate forests is less than that of tropical rainforests. In addition, temperate forests show far less diversity of tree species than tropical rainforest biomes. The trees of the temperate forests leaf out and shade much of the ground; however, more sunlight reaches the ground in this biome than in tropical rainforests because trees in temperate forests do not grow as tall as the trees in tropical rainforests. The soils of the temperate forests are rich in inorganic and organic nutrients compared to tropical rainforests. This is because of the thick layer of leaf litter on forest floors and reduced leaching of nutrients by rainfall. As this leaf litter decays, nutrients are returned to the soil. The leaf litter also protects soil from erosion, insulates the ground, and provides habitats for invertebrates and their predators (Figure 20.24).	B: deciduous.
Water is a versatile solvent that can dissolve many ionic and polar molecular solutes to make what? Here are the choices: A. sulfide solutions B. sulfate solutions C. aqueous solutions D. chloride solutions	Water is a versatile solvent that can dissolve many ionic and polar molecular solutes to make aqueous solutions.	C: aqueous solutions.
Cigarettes are a major source of what kind of chemical substances linked with cancer? Here are the choices: A. pesticides B. chemicals C. alkaloids D. carcinogens	Courtesy of the CDC/Debora Cartagena. Cigarettes are a major source of chemical carcinogens .	D: carcinogens.
Does the force of magnetism increase or decrease as the distance between objects increases? Here are the choices: A. increase B. fluctuate C. decrease D. remain stable		C: decrease.
What evolutionary concept emphasizes reproductive isolation? Here are the choices: A. chemical species concept B. biological species concept C. toxic species concept D. reproductive method concept	24.1 The biological species concept emphasizes reproductive isolation.	B: biological species concept.
What do you call the transfer of thermal energy between particles of matter that are touching? Here are the choices: A. convection B. conduction C. oxidation D. activation	Conduction is the transfer of thermal energy between particles of matter that are touching. Thermal energy is always transferred from particles of warmer matter to particles of cooler matter.	B: conduction.
What's the term for a cyclic hydrocarbon with a carbon-carbon triple bond? Here are the choices: A. cycloalkyne B. bialkyne C. bicycloalykne D. tricycloalkyne	Larger cycloalkanes also exist, but are less common. Cyclic hydrocarbons may also be unsaturated. A cycloalkene is a cyclic hydrocarbon with at least one carbon-carbon double bond. A cycloalkyne is a cyclic hydrocarbon with at least one carbon-carbon triple bond. Shown below are the simplified structural formulas for cyclohexene and cyclooctyne.	A: cycloalkyne.
Osmosis is driven by the imbalance of what? Here are the choices: A. evaporation B. water concentration C. isolation D. precipitation	Osmosis is the transport of water through a semipermeable membrane from a region of high concentration to a region of low concentration. Osmosis is driven by the imbalance in water concentration. For example, water is more concentrated in your body than in Epsom salt. When you soak a swollen ankle in Epsom salt, the water moves out of your body into the lower-concentration region in the salt. Similarly, dialysis is the transport of any other molecule through a semipermeable membrane due to its concentration difference. Both osmosis and dialysis are used by the kidneys to cleanse the blood. Osmosis can create a substantial pressure. Consider what happens if osmosis continues for some time, as illustrated in Figure 12.23. Water moves by osmosis from the left into the region on the right, where it is less concentrated, causing the solution on the right to rise. This movement will continue until the pressure ρgh created by the extra height of fluid on the right is large enough to stop further osmosis. This pressure is called a back pressure. The back pressure.	B: water concentration.
Chromosomes consist of what material made up of strings of dna? Here are the choices: A. mitochondria B. rna C. gray matter D. chromatin	8.2 Chromatin Chromosomes consist of chromatin11 . This is made up of strings of DNA, which typically measure centimeters in length if stretched out. This DNA is wound around a histone12 core and organized into nucleosome13 s. The chromatin14 must be uncoiled for gene expression15 and replication16 . Chromosome micrograph.	D: chromatin.
Are scissors simple or compound machines? Here are the choices: A. neither B. lever C. compound D. simple	Look at the scissors in Figure below . As you can see from the figure, scissors consist of two levers and two wedges. You apply force to the handle ends of the levers, and the output force is exerted by the blade ends of the levers. The fulcrum of both levers is where they are joined together. Notice that the fulcrum lies between the input and output points, so the levers are first-class levers. They change the direction of force. They may or may not also increase force, depending on the relative lengths of the handles and blades. The blades themselves are wedges, with a sharp cutting edge and a thicker dull edge.	C: compound.
What type of isotopes have short half-lives and are given in very low doses? Here are the choices: A. gasses B. stable isotopes C. radioisotopes D. radionuclides	Radioisotopes are widely used in medical diagnosis. These isotopes need to have short half-lives so that they can be administered in very low doses, thus minimizing damage to cells.	C: radioisotopes.
What is the multi-phase process in which the nucleus of a eukaryotic cell divides? Here are the choices: A. cytokinesis B. Osmosis C. mitosis D. fission	Mitosis in the Eukaryotic Cell Cycle. Mitosis is the multi-phase process in which the nucleus of a eukaryotic cell divides.	C: mitosis.
What are microscopic vessels with very thin, porous walls? Here are the choices: A. capillaries B. veins C. valves D. arteries		A: capillaries.
Which part of a fish helps them breathe? Here are the choices: A. fins B. pores C. layers D. gills		D: gills.
What produces hormones referred to as thymosins, which contribute to the development of the immune response in infants? Here are the choices: A. thymus B. receptors C. pancreas D. heart	The thymus is found behind the sternum. The thymus produces hormones referred to as thymosins, which contribute to the development of the immune response in infants. Adipose tissue, or fat tissue, produces the hormone leptin in response to food intake. Leptin produces a feeling of satiety after eating, reducing the urge for further eating.	A: thymus.
Some of the biggest waves occur with what type of storm that forms over the ocean and brings high winds? Here are the choices: A. hurricane B. tropical depression C. tsunami D. tropical storm	The size of an ocean wave depends on how fast, over how great a distance, and how long the wind blows. The greater each of these factors is, the bigger a wave will be. Some of the biggest waves occur with hurricanes. A hurricane is a storm that forms over the ocean. Its winds may blow more than 150 miles per hour! The winds also travel over long distances and may last for many days.	A: hurricane.
In many species, display behaviors, like a gorilla beating on its chest, are used instead of actual physical attacks to show what? Here are the choices: A. aggression B. stress C. friction D. dominance	In many species, display behaviors—rather than actual physical attacks—are used to show aggression. This helps prevent injury and death. Male gorillas, for example, are more likely to put on a display of aggression than to attack another male. In fact, gorillas have a whole series of display behaviors that they use to show aggression. They beat on their chest, dash back and forth, and pound the ground with their hands.	A: aggression.
What are the two types of vascular tissue? Here are the choices: A. ectoderm and phloem B. cytoplasm and ectoplasm C. xylem and phloem D. phloem and phlegm		C: xylem and phloem.
Because heterotrophs cannot make their own food, what are they called? Here are the choices: A. consumers B. destroyers C. customers D. products	Heterotrophs cannot make their own food, so they must eat or absorb it. For this reason, heterotrophs are also known as consumers . Consumers include all animals and fungi and many protists and bacteria. They consume either autotrophs or other heterotrophs. Heterotrophs show great diversity and may appear far more fascinating than producers. But heterotrophs are limited by their utter dependence on those autotrophs which originally made the food. If plants, algae, and autotrophic bacteria vanished from Earth, animals, fungi, and other heterotrophs would soon disappear as well. All life requires a constant input of energy. Only autotrophs can transform that ultimate, solar source into the chemical energy in food which powers life, as shown in Figure below .	A: consumers.
Nucleic acids contain the information needed for cells to make what? Here are the choices: A. metabolytes B. protons C. lipids D. proteins	The order of bases in nucleic acids is highly significant. The bases are like the letters of a four-letter alphabet. These "letters" can be combined to form "words. " Groups of three bases form words of the genetic code . Each code word, called a codon, stands for a different amino acid. A series of many codons spells out the sequence of amino acids in a polypeptide or protein ( Figure below ). In short, nucleic acids contain the information needed for cells to make proteins. This information is passed from a body cell to its daughter cells when the cell divides. It is also passed from parents to their offspring when organisms reproduce.	D: proteins.
Unlike corals, jellyfish spend most of their lives as what? Here are the choices: A. infants B. pupae C. medusae D. cercariae	Unlike corals, jellyfish spend most of their lives as medusae. They live virtually everywhere in the ocean. They are typically carnivores. They prey on zooplankton, other invertebrates, and the eggs and larvae of fish.	C: medusae.
What are materials that eject electrons when illuminated with light called? Here are the choices: A. illumination B. photoemissive C. photogenic D. fragmentation	Materials that eject electrons when illuminated with light, such as potassium, are called photoemissive. Not all materials are photoemissive, nor are all light sources capable of initiating electron emission from a given substance. For example, in Figure above , we see that 700 nm light will not initiate electron ejection, while 550 nm light will.	B: photoemissive.
Hfcs are used as a replacement for what? Here are the choices: A. nitrofluorocarbons B. pollutants C. cfcs D. gases	HFCs are used as a replacement for CFCs. The molecular structure of HFC134a is shown in this ball-and-stick model.	C: cfcs.
What has the burning of fossil fuels increased in the atmosphere? Here are the choices: A. temperature B. oxygen C. carbon dioxide D. ozone	Ocean water normally dissolves some of the carbon dioxide in the atmosphere. The burning of fossil fuels has increased the amount of carbon dioxide in the atmosphere. As a result, ocean water is also dissolving more carbon dioxide. When carbon dioxide dissolves in water, it forms a weak acid. With higher levels of dissolved carbon dioxide in ocean water, the water becomes more acidic. This process is called ocean acidification.	C: carbon dioxide.
In humans, the sperm cell is the only cell with what structure that enables motility? Here are the choices: A. eukaryotic B. False Cell C. sporangia D. flagella	The Cytoskeleton Much like the bony skeleton structurally supports the human body, the cytoskeleton helps the cells to maintain their structural integrity. The cytoskeleton is a group of fibrous proteins that provide structural support for cells, but this is only one of the functions of the cytoskeleton. Cytoskeletal components are also critical for cell motility, cell reproduction, and transportation of substances within the cell. The cytoskeleton forms a complex thread-like network throughout the cell consisting of three different kinds of proteinbased filaments: microfilaments, intermediate filaments, and microtubules (Figure 3.18). The thickest of the three is the microtubule, a structural filament composed of subunits of a protein called tubulin. Microtubules maintain cell shape and structure, help resist compression of the cell, and play a role in positioning the organelles within the cell. Microtubules also make up two types of cellular appendages important for motion: cilia and flagella. Cilia are found on many cells of the body, including the epithelial cells that line the airways of the respiratory system. Cilia move rhythmically; they beat constantly, moving waste materials such as dust, mucus, and bacteria upward through the airways, away from the lungs and toward the mouth. Beating cilia on cells in the female fallopian tubes move egg cells from the ovary towards the uterus. A flagellum (plural = flagella) is an appendage larger than a cilium and specialized for cell locomotion. The only flagellated cell in humans is the sperm cell that must propel itself towards female egg cells.	D: flagella.
Dispersal occurs only on what time scale? Here are the choices: A. developmental B. evolutionary C. regular D. conventional		B: evolutionary.
What type of feedback intensifies a change in the body’s physiological condition rather than reversing it? Here are the choices: A. negative feedback B. positive feedback C. neutral feedback D. susceptible feedback	Positive Feedback Positive feedback intensifies a change in the body’s physiological condition rather than reversing it. A deviation from the normal range results in more change, and the system moves farther away from the normal range. Positive feedback in the body is normal only when there is a definite end point. Childbirth and the body’s response to blood loss are two examples of positive feedback loops that are normal but are activated only when needed. Childbirth at full term is an example of a situation in which the maintenance of the existing body state is not desired. Enormous changes in the mother’s body are required to expel the baby at the end of pregnancy. And the events of childbirth, once begun, must progress rapidly to a conclusion or the life of the mother and the baby are at risk. The extreme muscular work of labor and delivery are the result of a positive feedback system (Figure 1.11).	B: positive feedback.
What law explains why some objects float and some sink. Here are the choices: A. montenegrins ' law B. newton's law C. archimedes' law D. flanges ' law	Archimedes’ law explains why some objects float in fluids even though they are very heavy. It all depends on how much fluid they displace. The cruise ship pictured in the opening image is extremely heavy, yet it stays afloat. If a steel ball with the same weight as the ship were placed in water, it would sink to the bottom. This is modeled in the Figure below . The reason the ball sinks is that its shape is very compact, so it displaces relatively little water. The volume of water displaced by the steel ball weighs less than the ball itself, so the buoyant force is not as great as the force of gravity pulling down on the ball. Thus, the ball sinks.	C: archimedes' law.
What is the force of gravity called? Here are the choices: A. scale B. weight C. pressure D. mass	The force of gravity is called weight. Near the surface of a planet, it has magnitude and is directed perpendicular to its surface. This is different from the Gravitational Constant, and differs from planet to planet.	B: weight.
The structure of the human tail bone is called what? Here are the choices: A. a abnormal structure B. an artifact C. a vital structure D. a vestigial structure	The majority of human genes have two or more possible alleles , which are alternative forms of a gene. Differences in alleles account for the considerable genetic variation among people. In fact, most human genetic variation is the result of differences in individual DNA bases within alleles.	D: a vestigial structure.
Of course, a net external force is needed to cause any acceleration, just as newton proposed in his second law of what? Here are the choices: A. speed B. land C. motion D. gravity	Of course, a net external force is needed to cause any acceleration, just as Newton proposed in his second law of motion. So a net external force is needed to cause a centripetal acceleration. In Centripetal Force, we will consider the forces involved in circular motion. PhET Explorations: Ladybug Motion 2D Learn about position, velocity and acceleration vectors. Move the ladybug by setting the position, velocity or acceleration, and see how the vectors change. Choose linear, circular or elliptical motion, and record and playback the motion to analyze the behavior.	C: motion.
The oldest fossil of land plants date back how many millions of years? Here are the choices: A. 430 million years B. 520 million years C. 470 million years D. 350 million years	Plants may have colonized the land as early as 700 million years ago. The oldest fossils of land plants date back about 470 million years. The first land plants probably resembled modern plants called liverworts , like the one shown in Figure below .	C: 470 million years.
What do young female meerkats act as in colonies? Here are the choices: A. midwives B. predators C. babysitters D. defenders	Besides social insects, animals in many other species also cooperate. For example, in meerkat colonies, young female meerkats act as babysitters. They take care of the baby meerkats while their parents are out looking for food.	C: babysitters.
Since europeans settled in the united states, about what percentage of topsoil has eroded away? Here are the choices: A. 33 percent B. 25 percent C. 10 percent D. 42 percent	Soil erosion is a natural occurrence. However, human activities have greatly accelerated soil erosion. In some locations, soil may now be eroding about 10 times faster than its natural rate. Since Europeans settled in the United States, approximately one-third of the topsoil has eroded away.	A: 33 percent.
What is first year after birth is called? Here are the choices: A. infancy B. adolescence C. primary stage D. neonatal stage	The first year after birth is called infancy . Infancy is a period when the baby grows very fast. During infancy, the baby doubles in length and triples in weight. Other important changes also happen during infancy:.	A: infancy.
What do you call a substance that cannot be separated into smaller pieces, which is also defined by the number of protons it has? Here are the choices: A. atom B. electrol C. molecule D. element	element: A substance that cannot be separated into smaller pieces. Defined by how many protons it has.	D: element.
A protective coating of zinc to prevent corrosion is applied to steel and other metals labeled what? Here are the choices: A. battered B. galvanized C. corroded D. polarized	Zinc is a silvery metal that quickly tarnishes to a blue-gray appearance. This change in color is due to an adherent coating of a basic carbonate, Zn2(OH)2CO3, which passivates the metal to inhibit further corrosion. Dry cell and alkaline batteries contain a zinc anode. Brass (Cu and Zn) and some bronze (Cu, Sn, and sometimes Zn) are important zinc alloys. About half of zinc production serves to protect iron and other metals from corrosion. This protection may take the form of a sacrificial anode (also known as a galvanic anode, which is a means of providing cathodic protection for various metals) or as a thin coating on the protected metal. Galvanized steel is steel with a protective coating of zinc.	B: galvanized.
How do bacteria reproduce? Here are the choices: A. sexual reproduction B. budding C. nuclear fission D. binary fission	New mitochondria and chloroplasts are produced through a process similar to binary fission. Bacteria also reproduce through binary fission.	D: binary fission.
The pituitary gland is associated with what bodily system? Here are the choices: A. cardiovascular B. nervous C. endocrine D. digestive	37.5 Endocrine Glands The pituitary gland is located at the base of the brain and is attached to the hypothalamus by the infundibulum. The anterior pituitary receives products from the hypothalamus by the hypophyseal portal system and produces six hormones. The posterior pituitary is an extension of the brain and releases hormones (antidiuretic hormone and oxytocin) produced by the hypothalamus. The thyroid gland is located in the neck and is composed of two lobes connected by the isthmus. The thyroid is made up of follicle cells that produce the hormones thyroxine and triiodothyronine. Parafollicular cells of the thyroid produce calcitonin. The parathyroid glands lie on the posterior surface of the thyroid gland and produce parathyroid hormone. The adrenal glands are located on top of the kidneys and consist of the renal cortex and renal medulla. The adrenal cortex is the outer part of the adrenal gland and produces the corticosteroids, glucocorticoids, and mineralocorticoids. The adrenal medulla is the inner part of the adrenal gland and produces the catecholamines epinephrine and norepinephrine. The pancreas lies in the abdomen between the stomach and the small intestine. Clusters of endocrine cells in the pancreas form the islets of Langerhans, which are composed of alpha cells that release glucagon and beta cells that release insulin. Some organs possess endocrine activity as a secondary function but have another primary function. The heart produces the hormone atrial natriuretic peptide, which functions to reduce blood volume, pressure, and Na + concentration. The gastrointestinal tract produces various hormones that aid in digestion. The kidneys produce renin, calcitriol, and erythropoietin. Adipose tissue produces leptin, which promotes satiety signals in the brain.	C: endocrine.
Why is it necessary to maintain proper levels of cations in intercellular fluids? Here are the choices: A. keep cells healthy B. cell division C. for digestion D. reverse homeostasis	Because the health of cells depends on maintaining the proper levels of cations in intracellular fluids, any change that affects the normal flux of metal ions across cell membranes could well cause an organism to die. Molecules that facilitate the transport of metal ions across membranes are generally called ionophores (ionplus phore from the Greek phorein, meaning “to carry”). Many ionophores are potent antibiotics that can kill or inhibit the growth of bacteria. An example isvalinomycin, a cyclic molecule with a central cavity lined with oxygen atoms (part (a) in Figure 21.14 "Valinomycin Is an Antibiotic That Functions Like an Ionophore") that is similar to the cavity of a crown ether (part (a) in Figure 13.7 "Crown Ethers and Cryptands"). Like a crown ether, valinomycin is highly selective: its affinity for K+ is about 1000 times greater than that for Na+. By increasing the flux of K+ ions into cells, valinomycin disrupts the normal K+ gradient across a cell membrane, thereby killing the cell (part (b) in Figure 21.14 "Valinomycin Is an Antibiotic That Functions Like an Ionophore"). Figure 21.14 Valinomycin Is an Antibiotic That Functions Like an Ionophore.	A: keep cells healthy.
Evolving from a single common ancestor, what group of organisms was perhaps the dominant life form on earth 250 million years ago? Here are the choices: A. acids B. atoms C. proteins D. fungi	Almost all fungi have a single common ancestor. The earliest fungi may have evolved about 600 million years ago. Fungi colonized land at least 460 million years ago. By 250 million years ago, they may have been the dominant life forms on Earth.	D: fungi.
What two forms can fluids take? Here are the choices: A. mixture or gas B. vapor or gas C. liquid or gas D. water or gas	Fluid friction occurs in fluids, which are liquids or gases.	C: liquid or gas.
What are ionic compounds that produce hydroxide ions when dissolved in water? Here are the choices: A. enzymes B. bases C. isotopes D. acids	Bases are ionic compounds that produce hydroxide ions when dissolved in water.	B: bases.
When do end portions of two nonsister chromatids trade places? Here are the choices: A. at night B. during respiration C. at every crossover D. never		C: at every crossover.
Through which part of the body do most animals take in oxygen? Here are the choices: A. rectum B. nose C. mouth D. ears		C: mouth.
Magma can be created when temperature rises, pressure lowers, or what else is added? Here are the choices: A. water B. sand C. dirt D. air	Magma can be created when temperature rises, pressure lowers, or water is added.	A: water.
What is the rotational equivalent of a force? Here are the choices: A. power B. momentum C. centripetal force D. torque	The magnitude, direction, and point of application of the force are incorporated into the definition of the physical quantity called torque. Torque is the rotational equivalent of a force. It is a measure of the effectiveness of a force in changing or accelerating a rotation (changing the angular velocity over a period of time). In equation form, the magnitude of torque is defined to be.	D: torque.
What happens when when the immune system does not work properly? Here are the choices: A. stroke B. anemia C. diabetes D. immunodeficiency	Immunodeficiency occurs when the immune system is not working properly. As a result, it cannot fight off pathogens that a normal immune system would be able to resist. Most commonly, immunodeficiency diseases occur when T or B cells (or both) do not work as well as they should, or when your body doesn't produce enough antibodies.	D: immunodeficiency.
What is the beneficial function to the body of sweating? Here are the choices: A. regulating body temperature B. diuretic effect C. calorie loss D. pheromone release	Sweating regulates body temperature. The composition of the sweat determines whether body odor is a byproduct of sweating. Visit this link (http://openstaxcollege. org/l/sweating) to learn more about sweating and body odor.	A: regulating body temperature.
What type of microscope is used to see extremely small objects? Here are the choices: A. ultrasonic microscope B. electron microscope C. optical microscope D. X-ray microscope	Light microscopes continued to improve and are still used today. However, to see extremely small objects, a different type of microscope, such as an electron microscope, must be used.	B: electron microscope.
What is the most prevalent gas in the atmosphere, but not the most vital for life? Here are the choices: A. nitrogen B. oxygen C. carbon dioxide D. argon	Most of the atmosphere is nitrogen, but it doesn't do much. Carbon dioxide and oxygen are the gases in the atmosphere that are needed for life.	A: nitrogen.
Why wouldn't a teakettle have an aluminum handle? Here are the choices: A. it absorbs light B. it isn't washable C. it is magnetic D. it conducts heat	This teakettle is made of aluminum except for its handle, which is made of plastic. Aluminum is a good conductor of heat. It conducts heat from the flames on the range to the water inside the kettle, so the water heats quickly. Plastic, on the other hand, is not a good conductor of heat. It stays cool enough to touch even when the rest of the teakettle becomes very hot.	D: it conducts heat.
What can help scientist gather information for an investigation? Here are the choices: A. conclusions B. controls C. variables D. observations	Observations raise questions that lead to scientific investigations. Observations also help scientists gather evidence in investigations.	D: observations.
What do we call the region on the lung root formed by the entrance of the nerves at the hilum? Here are the choices: A. pulmonary plexus B. renal plexus C. heart plexus D. brain plexus	Nervous Innervation Dilation and constriction of the airway are achieved through nervous control by the parasympathetic and sympathetic nervous systems. The parasympathetic system causes bronchoconstriction, whereas the sympathetic nervous system stimulates bronchodilation. Reflexes such as coughing, and the ability of the lungs to regulate oxygen and carbon dioxide levels, also result from this autonomic nervous system control. Sensory nerve fibers arise from the vagus nerve, and from the second to fifth thoracic ganglia. The pulmonary plexus is a region on the lung root formed by the entrance of the nerves at the hilum. The nerves then follow the bronchi in the lungs and branch to innervate muscle fibers, glands, and blood vessels.	A: pulmonary plexus.
Both oxygen and glucose are transported within the body via what? Here are the choices: A. heart B. bone C. blood D. marrow	Oxygen is just one substance transported by the blood. The blood also transports nutrients such as glucose.	C: blood.
An increase in the body's cholesterol levels can lead to your arteries filling with what? Here are the choices: A. plaque B. fat C. triglycerides D. marble	Ways to prevent atherosclerosis include eating healthy foods, getting plenty of exercise and not smoking. A diet high in saturated fat and cholesterol can raise your body's cholesterol levels, which can lead to increased plaque in your arteries. Cholesterol and saturated fat are found mostly in animal products, such as meat, eggs, milk and other dairy products.	A: plaque.
After citric acid forms, it goes through a series of reactions that release what, which is then captured in special molecules? Here are the choices: A. metabolytes B. hydrogen C. energy D. chlorophyll	After citric acid forms, it goes through a series of reactions that release energy. The energy is captured in molecules of NADH, ATP, and FADH 2 , another energy-carrying compound. Carbon dioxide is also released as a waste product of these reactions.	C: energy.
All chemical changes involve a transfer of what? Here are the choices: A. energy B. nitrogen C. pressure D. hydrogen	All chemical changes involve a transfer of energy. When zinc reacts with hydrochloric acid, the test tube becomes very warm as energy is released during the reaction. Some other reactions absorb energy. While energy changes are a potential sign of a chemical reaction, care must be taken to ensure that a chemical reaction is indeed taking place. Physical changes also involve a transfer of energy. Melting of a solid absorbs energy, while the condensation of a gas releases energy. The only way to be certain that a chemical reaction has taken place is to test the composition of the substances after the change has taken place to see if they are different from the starting substances.	A: energy.
The normal response of the respiratory system to elevated ph is to increase the amount of what in the blood? Here are the choices: A. glucose B. acid C. red blood cells D. co2	Respiratory Compensation Respiratory compensation for metabolic acidosis increases the respiratory rate to drive off CO2 and readjust the bicarbonate to carbonic acid ratio to the 20:1 level. This adjustment can occur within minutes. Respiratory compensation for metabolic alkalosis is not as adept as its compensation for acidosis. The normal response of the respiratory system to elevated pH is to increase the amount of CO2 in the blood by decreasing the respiratory rate to conserve CO2. There is a limit to the.	D: co2.
What part of an atom is electrically neutral? Here are the choices: A. neutrons B. protons C. electrons D. newtons	An atom’s protons and electrons carry electrical charges. Protons, with their positive charge, are designated p+. Electrons, which have a negative charge, are designated e–. An atom’s neutrons have no charge: they are electrically neutral. Just as a magnet sticks to a steel refrigerator because their opposite charges attract, the positively charged protons attract the negatively charged electrons. This mutual attraction gives the atom some structural stability. The attraction by the positively charged nucleus helps keep electrons from straying far. The number of protons and electrons within a neutral atom are equal, thus, the atom’s overall charge is balanced.	A: neutrons.
Bar, circle, and line are all types of what? Here are the choices: A. theories B. maps C. algorithms D. graphs	Descriptive statistics and graphs help organize data so patterns and trends are more apparent. Descriptive statistics include the mean and range. Types of graphs include bar, circle, and line graphs.	D: graphs.
Unlike eukaryotic cells, dna and rna synthesis in prokaryotic cells occurs together with synthesis of what? Here are the choices: A. protein B. fruit C. membrane D. mutation	ART CONNECTION QUESTIONS 1. Figure 14.10 In eukaryotic cells, DNA and RNA synthesis occur in a separate compartment from protein synthesis. In prokaryotic cells, both processes occur together. What advantages might there be to separating the processes? What advantages might there be to having them occur together? 2. Figure 14.14 You isolate a cell strain in which the joining together of Okazaki fragments is impaired and.	A: protein.
What type of bacteria are sometimes used as weapons of bioterrorism? Here are the choices: A. avian B. hypothermic C. pathogenic D. carcinogenic		C: pathogenic.
What is the name of a joint in which one bone rotates in relation to another bone? Here are the choices: A. gliding B. pivot joint C. hinge D. ball and socket	Rotation Rotation can occur within the vertebral column, at a pivot joint, or at a ball-and-socket joint. Rotation of the neck or body is the twisting movement produced by the summation of the small rotational movements available between adjacent vertebrae. At a pivot joint, one bone rotates in relation to another bone. This is a uniaxial joint, and thus rotation is the only motion allowed at a pivot joint. For example, at the atlantoaxial joint, the first cervical (C1) vertebra (atlas) rotates around the dens, the upward projection from the second cervical (C2) vertebra (axis). This allows the head to rotate from side to side as when shaking the head “no. ” The proximal radioulnar joint is a pivot joint formed by the head of the radius and its articulation with the ulna. This joint allows for the radius to rotate along its length during pronation and supination movements of the forearm. Rotation can also occur at the ball-and-socket joints of the shoulder and hip. Here, the humerus and femur rotate around their long axis, which moves the anterior surface of the arm or thigh either toward or away from the midline of the body. Movement that brings the anterior surface of the limb toward the midline of the body is called medial (internal) rotation. Conversely, rotation of the limb so that the anterior surface moves away from the midline is lateral (external) rotation (see Figure 9.12f). Be sure to distinguish medial and lateral rotation, which can only occur at the multiaxial shoulder and hip joints, from circumduction, which can occur at either biaxial or multiaxial joints.	B: pivot joint.
Cirrus, stratus, and cumulus are types of what? Here are the choices: A. storms B. plants C. slopes D. clouds	Cloud types include cirrus, stratus, and cumulus.	D: clouds.
What is a buildup of electric charges on objects? Here are the choices: A. static B. potential C. conduction D. wattage	Our Sun is a star , a sphere of plasma held together by gravity. It is an ordinary star that is extraordinarily important. The Sun provides light and heat to our planet. This star supports almost all life on Earth.	A: static.
Where do you find the greatest biodiversity? Here are the choices: A. in shallow lakes B. in the tundra C. at the poles D. in the tropics	It is not yet clear why biodiversity increases closer to the equator, but hypotheses include the greater age of the ecosystems in the tropics versus temperate regions, which were largely devoid of life or drastically impoverished during the last ice age. The greater age provides more time for speciation. Another possible explanation is the greater energy the tropics receive from the sun versus the lesser energy input in temperate and polar regions. But scientists have not been able to explain how greater energy input could translate into more species. The complexity of tropical ecosystems may promote speciation by increasing the habitat heterogeneity, or number of ecological niches, in the tropics relative to higher latitudes. The greater heterogeneity provides more opportunities for coevolution, specialization, and perhaps greater selection pressures leading to population differentiation. However, this hypothesis suffers from some circularity—ecosystems with more species encourage speciation, but how did they get more species to begin with? The tropics have been perceived as being more stable than temperate regions, which have a pronounced climate and day-length seasonality. The tropics have their own forms of seasonality, such as rainfall, but they are generally assumed to be more stable environments and this stability might promote speciation. Regardless of the mechanisms, it is certainly true that biodiversity is greatest in the tropics. The number of endemic species is higher in the tropics. The tropics also contain more biodiversity hotspots. At the same time, our knowledge of the species living in the tropics is lowest and because of recent, heavy human activity the potential for biodiversity loss is greatest.	D: in the tropics.
The ostwald process is the commercial method for producing what? Here are the choices: A. citric acid B. nitric acid C. chlorine D. deoxyribonucleic acid	NaNO 3(s) + H 2 SO 4(l) ⎯⎯→ NaHSO 4(s) + HNO 3(g) The Ostwald process is the commercial method for producing nitric acid. This process involves the oxidation of ammonia to nitric oxide, NO; oxidation of nitric oxide to nitrogen dioxide, NO2; and further oxidation and hydration of nitrogen dioxide to form nitric acid: 4NH 3(g) + 5O 2(g) ⟶ 4NO(g) + 6H 2 O(g) 2NO(g) + O 2(g) ⟶ 2NO 2(g) 3NO 2(g) + H 2 O(l) ⟶ 2HNO 3(aq) + NO(g) Or 4NO 2(g) + O 2(g) + 2H 2 O(g) ⟶ 4HNO 3(l) Pure nitric acid is a colorless liquid. However, it is often yellow or brown in color because NO2 forms as the acid decomposes. Nitric acid is stable in aqueous solution; solutions containing 68% of the acid are commercially available concentrated nitric acid. It is both a strong oxidizing agent and a strong acid. The action of nitric acid on a metal rarely produces H2 (by reduction of H+) in more than small amounts. Instead, the reduction of nitrogen occurs. The products formed depend on the concentration of the acid, the activity of the metal, and the temperature. Normally, a mixture of nitrates, nitrogen oxides, and various reduction products form. Less active metals such as copper, silver, and lead reduce concentrated nitric acid primarily to nitrogen dioxide. The reaction of dilute nitric acid with copper produces NO. In each case, the nitrate salts of the metals crystallize upon evaporation of the resultant solutions. Nonmetallic elements, such as sulfur, carbon, iodine, and phosphorus, undergo oxidation by concentrated nitric acid to their oxides or oxyacids, with the formation of NO2: S(s) + 6HNO 3(aq) ⟶ H 2 SO 4(aq) + 6NO 2(g) + 2H 2 O(l) C(s) + 4HNO 3(aq) ⟶ CO 2(g) + 4NO 2(g) + 2H 2 O(l) Nitric acid oxidizes many compounds; for example, concentrated nitric acid readily oxidizes hydrochloric acid to chlorine and chlorine dioxide. A mixture of one part concentrated nitric acid and three parts concentrated hydrochloric acid (called aqua regia, which means royal water) reacts vigorously with metals. This mixture is particularly useful in dissolving gold, platinum, and other metals that are more difficult to oxidize than hydrogen. A simplified equation to represent the action of aqua regia on gold is: Au(s) + 4HCl(aq) + 3HNO 3(aq) ⟶ HAuCl 4(aq) + 3NO 2(g) + 3H 2 O(l).	B: nitric acid.
What includes the bones and cartilage? Here are the choices: A. lungs B. skeleton C. skull D. fossil	The human skeleton includes bones and cartilage.	B: skeleton.
What type of constraints are placed on technological design? Here are the choices: A. moral and legal B. physical and legal C. legal and social D. physical and social	Technological design constraints may be physical or social.	D: physical and social.
What cycle is the second stage of cellular respiration? Here are the choices: A. glycolysis B. electron transport chain C. krebs cycle D. sodium potassium pump	The Krebs cycle is the second stage of cellular respiration.	C: krebs cycle.
What phenomenon can cause a protein in an organism to be made incorrectly? Here are the choices: A. allele B. heredity C. mutation D. evolution	A mutation may have no effect. However, sometimes a mutation can cause a protein to be made incorrectly. A defect in the protein can affect how well the protein works, or whether it works at all. Usually the loss of a protein function is detrimental to the organism.	C: mutation.
What are mid-wavelength electromagnetic waves commonly referred to as? Here are the choices: A. x-rays B. gamma rays C. light D. electricity	Mid-wavelength electromagnetic waves are commonly called light. This range of electromagnetic waves has shorter wavelengths and higher frequencies than radio waves, but not as short and high as X rays and gamma rays. Light includes visible light, infrared light, and ultraviolet light. If you look back at Figure above , you can see where these different types of light waves fall in the electromagnetic spectrum.	C: light.
Bronchial tubes in the lungs branch into ever-smaller structures, finally ending in alveoli. the alveoli act like what? Here are the choices: A. tiny bubbles B. bellows C. filters D. springs	Figure 11.31 Bronchial tubes in the lungs branch into ever-smaller structures, finally ending in alveoli. The alveoli act like tiny bubbles. The surface tension of their mucous lining aids in exhalation and can prevent inhalation if too great.	A: tiny bubbles.
What can be used to accelerate the rate at which chemical reactions occur? Here are the choices: A. components B. protein C. hormones D. enzymes	Enzymes increase the rate of chemical reactions by reducing the amount of activation energy needed for reactants to start reacting. One way this can happen is modeled in the Figure below . Enzymes aren’t changed or used up in the reactions they catalyze, so they can be used to speed up the same reaction over and over again. Each enzyme is highly specific for the particular reaction is catalyzes, so enzymes are very effective. A reaction that would take many years to occur without its enzyme might occur in a split second with the enzyme. Enzymes are also very efficient, so waste products rarely form.	D: enzymes.
Air temperature changes as what increases? Here are the choices: A. pressure B. density C. altitude D. salinity	Air temperature changes as altitude increases. In some layers of the atmosphere, the temperature decreases. In other layers, it increases. You can see this in Figure below . Refer to this figure as you read about the layers below.	C: altitude.
What happens to energy in a closed system? Here are the choices: A. is wasted B. is destroyed C. is conserved D. is replicated	Energy is conserved in a closed system. That is, if you add up all the energy of an object(s) at one time it will equal all the energy of said object(s) at a later time. A closed system is a system where no energy is transferred in or out. The total energy of the universe is a constant (i. e. it does not change). The problems below do not consider the situation of energy transfer (called work). So friction and other sources where energy leaves the system are not present. Thus, one simply adds up all the potential energy and kinetic energy before and sets it equal to the addition of the total potential energy and kinetic energy after .	C: is conserved.
What are magnetites naturally attracted to? Here are the choices: A. glass B. stone C. iron D. aluminum	Magnetite naturally attracts iron nails and filings. Its natural magnetism was discovered thousands of years ago.	C: iron.
The visceral senses are most often below the limit of conscious perception because they are involved in this? Here are the choices: A. sensory balance B. homeostatic manipulation C. subtle regulation D. homeostatic regulation	the conscious perception of the how the body interacts with the environment. The visceral senses are most often below the limit of conscious perception because they are involved in homeostatic regulation through the autonomic nervous system. The sensory exam tests the somatic senses, meaning those that are consciously perceived. Testing of the senses begins with examining the regions known as dermatomes that connect to the cortical region where somatosensation is perceived in the postcentral gyrus. To test the sensory fields, a simple stimulus of the light touch of the soft end of a cotton-tipped applicator is applied at various locations on the skin. The spinal nerves, which contain sensory fibers with dendritic endings in the skin, connect with the skin in a topographically organized manner, illustrated as dermatomes (Figure 16.13). For example, the fibers of eighth cervical nerve innervate the medial surface of the forearm and extend out to the fingers. In addition to testing perception at different positions on the skin, it is necessary to test sensory perception within the dermatome from distal to proximal locations in the appendages, or lateral to medial locations in the trunk. In testing the eighth cervical nerve, the patient would be asked if the touch of the cotton to the fingers or the medial forearm was perceptible, and whether there were any differences in the sensations.	D: homeostatic regulation.
The ideal gas law does not require that the properties of what? Here are the choices: A. transit change B. copper change C. liquid change D. gas change	The ideal gas law does not require that the properties of a gas change.	D: gas change.
Vertebrates lacking what structures often use lungs for gas exchange? Here are the choices: A. gills B. pores C. nostrils D. spores		A: gills.
What "kind" of water may take longer to become contaminated than surface water, while the natural cleaning process may take longer? Here are the choices: A. lake water B. groundwater C. dam water D. spring water	Water pollution happens when contaminants enter water bodies. Contaminants are any substances that harm the health of the environment or humans. Most contaminants enter the water because of humans. Surface water (river or lake) can be exposed to and contaminated by acid rain, storm water runoff, pesticide runoff, and industrial waste. This water is cleaned somewhat by exposure to sunlight, aeration, and microorganisms in the water. Groundwater (private wells and some public water supplies) generally takes longer to become contaminated, but the natural cleaning process also may take much longer. Groundwater can be contaminated by disease-producing pathogens, careless disposal of hazardous household chemical-containing products, agricultural chemicals, and leaking underground storage tanks.	B: groundwater.

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.