questions stringlengths 37 1.22k | reasoning stringlengths 0 3.56k ⌀ | answers stringlengths 4 138 |
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What is defined as the amount of force acting on a given area?
Here are the choices:
A. power
B. density
C. resistance
D. pressure | Pressure is defined as the amount of force acting on a given area. It measures how concentrated a force is. | D: pressure. |
Which type of energy is the energy of anything in motion?
Here are the choices:
A. physiological engergy
B. diffuse energy
C. residual engergy
D. kinetic engergy | Kinetic energy is the energy of anything in motion. Your muscles move your leg, your foot kicks the ball, and the ball gains kinetic energy ( Figure below ). The kinetic energy was converted from potential energy that was in your leg before the kick. The action of kicking the ball is energy changing forms. The same is true for anything that involves change. | D: kinetic engergy. |
What are large sheets of ice that cover relatively flat ground called?
Here are the choices:
A. continental glaciers
B. rocky glaciers
C. cellular glaciers
D. land glaciers | Continental glaciers are large ice sheets that cover relatively flat ground. These glaciers flow outward from where the greatest amounts of snow and ice accumulate. | A: continental glaciers. |
What is the accelerating pattern of increasing population size called?
Here are the choices:
A. limited growth
B. induced growth
C. exponential growth
D. reproducing growth | Exponential Growth Charles Darwin, in his theory of natural selection, was greatly influenced by the English clergyman Thomas Malthus. Malthus published a book in 1798 stating that populations with unlimited natural resources grow very rapidly, and then population growth decreases as resources become depleted. This accelerating pattern of increasing population size is called exponential growth. The best example of exponential growth is seen in bacteria. Bacteria are prokaryotes that reproduce by prokaryotic fission. This division takes about an hour for many bacterial species. If 1000 bacteria are placed in a large flask with an unlimited supply of nutrients (so the nutrients will not become depleted), after an hour, there is one round of division and each organism divides, resulting in 2000 organisms—an increase of 1000. In another hour, each of the 2000 organisms will double, producing 4000, an increase of 2000 organisms. After the third hour, there should be 8000 bacteria in the flask, an increase of 4000 organisms. The important concept of exponential growth is that the population growth rate—the number of organisms added in each reproductive generation—is accelerating; that is, it is increasing at a greater and greater rate. After 1 day and 24 of these cycles, the population would have increased from 1000 to more than 16 billion. When the population size, N, is plotted over time, a J-shaped growth curve is produced (Figure 45.9). The bacteria example is not representative of the real world where resources are limited. Furthermore, some bacteria will die during the experiment and thus not reproduce, lowering the growth rate. Therefore, when calculating the growth rate of a population, the death rate (D) (number organisms that die during a particular time interval) is subtracted from the birth rate (B) (number organisms that are born during that interval). This is shown in the following formula:. | C: exponential growth. |
Ions can be formed when atoms lose what other particles?
Here are the choices:
A. protons
B. shells
C. neutrons
D. electrons | By losing an electron, the sodium atom becomes a sodium ion. It now has more protons than electrons and a charge of +1. Positive ions such as sodium are given the same name as the element. The chemical symbol has a plus sign to distinguish the ion from an atom of the element. The symbol for a sodium ion is Na + . | D: electrons. |
Deserts are generally dry ecosystems having very little what?
Here are the choices:
A. snowfall
B. rainfall
C. heat
D. mountains | frequent algal blooms d. little or no vegetation 12. Which of the following is an example of a weather event? a. The hurricane season lasts from June 1 through November 30. The amount of atmospheric CO2 has steadily increased during the last century. A windstorm blew down trees in the Boundary Waters Canoe Area in Minnesota on July 4, 1999. Deserts are generally dry ecosystems having very little rainfall. Which of the following natural forces is responsible for the release of carbon dioxide and other atmospheric gases? a. the Milankovitch cycles b. volcanoes c. solar intensity d. burning of fossil fuels. | B: rainfall. |
The average number of individuals per unit of area can be expressed as what?
Here are the choices:
A. the percent of population
B. total density
C. population density
D. percent density | Population density just gives the average number of individuals per unit of area or volume. Often, individuals in a population are not spread out evenly. Instead, they may live in clumps or some other pattern (see Figure below ). The pattern may reflect characteristics of the species or its environment. Population distribution describes how the individuals are distributed, or spread throughout their habitat. | C: population density. |
The top 200 meters of water is called what zone?
Here are the choices:
A. the photic zone
B. the subterranean zone
C. the biotic zone
D. the stratosphere | The top 200 meters of water is the photic zone. Producers here include seaweeds and phytoplankton. Other organisms are plentiful. They include zooplankton and animals such as fish, whales, and dolphins. | A: the photic zone. |
A homogeneous mixture with tiny particles in it is known as what?
Here are the choices:
A. element
B. solution
C. plasmid
D. structure | A solution is a homogeneous mixture with tiny particles. An example is salt water. The particles of a solution are too small to reflect light. As a result, you cannot see them. That’s why salt water looks the same as pure water. The particles of solutions are also too small to settle or be filtered out of the mixture. | B: solution. |
What is the term for decomposers that consume dead leaves, animal feces, and other organic debris collected on the ground or at the bottom of water?
Here are the choices:
A. consumers
B. scavengers
C. detritivores
D. recyclers | Detritivores are decomposers that consume dead leaves, animal feces, and other organic debris that collects on the ground or at the bottom of a body of water. Examples of detritivores include earthworms and catfish. You can see another example in Figure below . | C: detritivores. |
If a gas in a closed area experiences increases in pressure and decreases in temperatures, what other attribute of the gas will be affected?
Here are the choices:
A. gravity
B. velocity
C. volume
D. temperature | Both the increase in pressure and the decrease in temperature cause the volume of the gas sample to decrease. Since both changes are relatively small, the volume does not decrease dramatically. | C: volume. |
What is the term for the hard covering that protects insects, crustaceans, and spiders?
Here are the choices:
A. exoplate
B. endoskeleton
C. exoskeleton
D. endoplate | Most animals have an exoskeleton, including insects, spiders, scorpions, horseshoe crabs, centipedes, and crustaceans. Scientists estimate that, of insects alone, there are over 30 million species on our planet. The exoskeleton is a hard covering or shell that provides benefits to the animal, such as protection against damage from predators and from water loss (for land animals); it also provides for the attachments of muscles. As the tough and resistant outer cover of an arthropod, the exoskeleton may be constructed of a tough polymer such as chitin and is often biomineralized with materials such as calcium carbonate. This is fused to the animal’s epidermis. Ingrowths of the exoskeleton, called apodemes, function as attachment sites for muscles, similar to tendons in more advanced animals (Figure 33.3). In order to grow, the animal must first synthesize a new exoskeleton underneath the old one and then shed or molt the original covering. This limits the animal’s ability to grow continually, and may limit the individual’s ability to mature if molting does not occur at the proper time. The thickness of the exoskeleton must be increased significantly to accommodate any increase in weight. It is estimated that a doubling of body size increases body weight by a factor of eight. The increasing thickness of the chitin necessary to support this weight limits most animals with an exoskeleton to a relatively small size. The same principles apply to endoskeletons, but they are more efficient because muscles are attached on the outside, making it easier to compensate for increased mass. | C: exoskeleton. |
What gas is expired out of the body during exhalation?
Here are the choices:
A. hydrogen
B. carbon monoxide
C. carbon dioxide
D. oxygen | Introduction Breathing is an involuntary event. How often a breath is taken and how much air is inhaled or exhaled are tightly regulated by the respiratory center in the brain. Humans, when they aren’t exerting themselves, breathe approximately 15 times per minute on average. Canines, like the dog in Figure 39.1, have a respiratory rate of about 15–30 breaths per minute. With every inhalation, air fills the lungs, and with every exhalation, air rushes back out. That air is doing more than just inflating and deflating the lungs in the chest cavity. The air contains oxygen that crosses the lung tissue, enters the bloodstream, and travels to organs and tissues. Oxygen (O2) enters the cells where it is used for metabolic reactions that produce ATP, a high-energy compound. At the same time, these reactions release carbon dioxide (CO2) as a by-product. CO2 is toxic and must be eliminated. Carbon dioxide exits the cells, enters the bloodstream, travels back to the lungs, and is expired out of the body during exhalation. | C: carbon dioxide. |
Through this process, algae provide glucose for the ecosystem?
Here are the choices:
A. GLUCOPHAGE
B. photosynthesis
C. glycolysis
D. spermatogenesis | In a marine ecosystem, algae are the producers. Through photosynthesis, they provide glucose for the ecosystem. So, can too much algae be a bad thing? Eutrophication is an over-enrichment of chemical nutrients in a body of water. Usually these nutrients are the nitrogen and phosphorous found in fertilizers. Run-off from lawns or farms can wash fertilizers into rivers or coastal waters. | B: photosynthesis. |
What determines your hair color trait?
Here are the choices:
A. cells
B. Heredity
C. genes
D. chromosomes | There are variations in the traits of a population. For example, there are lots of variations in the color of human hair. Hair can be blonde, brown, black, or even red. Hair color is a trait determined by genes. | C: genes. |
What layer of skin is directly under the epidermis?
Here are the choices:
A. hypodermis
B. the aponeurosis
C. the dermis
D. sweat glands | The dermis is the layer of skin directly under the epidermis. It is made of a tough connective tissue. The dermis contains hair follicles, sweat glands, oil glands, and blood vessels ( Figure above ). It also holds many nerve endings that give you your sense of touch, pressure, heat, and pain. | C: the dermis. |
What is caused by bodies sliding over rough surfaces?
Here are the choices:
A. vibration
B. heat loss
C. tension
D. friction | Friction is caused by bodies sliding over rough surfaces. | D: friction. |
The electromagnetic spectrum represents the full range of frequency of what type of wave?
Here are the choices:
A. mechanical
B. transverse wave
C. seismic
D. electromagnetic | Electromagnetic waves vary in their frequencies and wavelengths, and waves with higher frequencies have greater energy. The electromagnetic spectrum represents the full range of frequencies of electromagnetic waves. | D: electromagnetic. |
Distinguishing between homology and analogy is critical in reconstructing what?
Here are the choices:
A. phylogenies
B. proteases
C. residues
D. phylums | A: phylogenies. | |
What do many mollusks secrete for their protection?
Here are the choices:
A. microscopic shell
B. mucus
C. sedimentation shell
D. calcareous shell | 15.4 Mollusks and Annelids The phylum Mollusca is a large, mainly marine group of invertebrates. Mollusks show a variety of morphologies. Many mollusks secrete a calcareous shell for protection, but in other species, the shell is reduced or absent. Mollusks are protostomes. The dorsal epidermis in mollusks is modified to form the mantle, which encloses the mantle cavity and visceral organs. This cavity is distinct from the coelomic cavity, which the adult animal retains, surrounding the heart. Respiration is facilitated by gills known as ctenidia. A chitinous scraper called the radula is present in most mollusks. Mollusks are mostly dioecious and are divided into seven classes. The phylum Annelida includes worm-like, segmented animals. Segmentation is both external and internal, which is called metamerism. Annelids are protostomes. The presence of chitinous hairs called chaetae is characteristic of most members. These animals have well-developed nervous and digestive systems. Polychaete annelids have parapodia that participate in locomotion and respiration. Suckers are seen in the order Hirudinea. Breeding systems include separate sexes and hermaphroditism. | D: calcareous shell. |
What were the first particles with mass to be directly confirmed to have the wavelength proposed by de broglie?
Here are the choices:
A. electrons
B. protons
C. negatrons
D. ions | Electrons were the first particles with mass to be directly confirmed to have the wavelength proposed by de Broglie. Subsequently, protons, helium nuclei, neutrons, and many others have been observed to exhibit interference when they interact with objects having sizes similar to their de Broglie wavelength. The de Broglie wavelength for massless particles was well established in the 1920s for photons, and it has since been observed that all massless particles have a de Broglie wavelength λ = h / p. The wave nature of all particles is a universal characteristic of nature. We shall see in following sections that implications of the de Broglie wavelength include the quantization of energy in atoms and molecules, and an alteration of our basic view of nature on the microscopic scale. The next section, for example, shows that there are limits to the precision with which we may make predictions, regardless of how hard we try. There are even limits to the precision with which we may measure an object’s location or energy. Making Connections: A Submicroscopic Diffraction Grating The wave nature of matter allows it to exhibit all the characteristics of other, more familiar, waves. Diffraction gratings, for example, produce diffraction patterns for light that depend on grating spacing and the wavelength of the light. This effect, as with most wave phenomena, is most pronounced when the wave interacts with objects having a size similar to its wavelength. For gratings, this is the spacing between multiple slits. ) When electrons interact with a system having a spacing similar to the electron wavelength, they show the same types of interference patterns as light does for diffraction gratings, as shown at top left in Figure 29.24. Atoms are spaced at regular intervals in a crystal as parallel planes, as shown in the bottom part of Figure 29.24. The spacings between these planes act like the openings in a diffraction grating. At certain incident angles, the paths of electrons scattering from successive planes differ by one wavelength and, thus, interfere constructively. At other angles, the path length differences are not an integral wavelength, and there is partial to total destructive interference. This type of scattering from a large crystal with well-defined lattice planes can produce dramatic interference patterns. It is called Bragg reflection, for the father-and-son team who first explored and analyzed it in some detail. The expanded view also shows the pathlength differences and indicates how these depend on incident angle θ in a manner similar to the diffraction patterns for x rays reflecting from a crystal. | A: electrons. |
What is a simple machine that consists of a rope wrapped around a grooved wheel?
Here are the choices:
A. Wheel and axle
B. Inclined plane
C. Lever
D. a pulley | A pulley is a simple machine that consists of a rope wrapped around a grooved wheel. Pulleys are generally used to lift a load. | D: a pulley. |
What helps screen libraries for a gene of interest using nucleic acid hybridization?
Here are the choices:
A. nucleic acid probe
B. proteins acid probe
C. mitochondrial acid probe
D. cellular acid probe | A: nucleic acid probe. | |
What is one way of classifying organisms called?
Here are the choices:
A. cluster
B. spasm
C. tuck
D. clade | One way of classifying organisms that shows phylogeny is by using the clade. A clade is a group of organisms that includes an ancestor and all of its descendants. Clades are based on cladistics. This is a method of comparing traits in related species to determine ancestor-descendant relationships. Clades are represented by cladograms, like the one in Figure below . This cladogram represents the mammal and reptile clades. The reptile clade includes birds. It shows that birds evolved from reptiles. Linnaeus classified mammals, reptiles, and birds in separate classes. This masks their evolutionary relationships. | D: clade. |
The earliest stages of spermatogenesis occur closest to the lumen of the what?
Here are the choices:
A. viviparous tubules
B. interstitial tubules
C. seminiferous tubules
D. epithelium tubules | C: seminiferous tubules. | |
Which of the electromagnetic waves have the shortest wavelengths and highest frequencies?
Here are the choices:
A. ultraviolet
B. plasma
C. gamma
D. beta | Of all electromagnetic waves, gamma rays have the shortest wavelengths and highest frequencies. Because of their very high frequencies, gamma rays have more energy than any other electromagnetic waves. | C: gamma. |
The oxidation of an alcohol can produce either an aldehyde or what?
Here are the choices:
A. ester
B. ketone
C. enzyme
D. amine | The oxidation of an alcohol can produce either an aldehyde or a ketone. Ethanol can be oxidized in the laboratory through a heating process combined with the addition of an oxidizing agent such as the dichromate ion, which catalyzes the reaction in an acidic solution. The reaction produces the aldehyde ethanal (acetaldehyde). | B: ketone. |
Change in momentum in an object is equivalent to what other measurement?
Here are the choices:
A. impulse
B. gravity
C. velocity
D. resistance | The change of momentum of an object is equal to the impulse. | A: impulse. |
Where does most water evaporate from?
Here are the choices:
A. rivers
B. seas
C. lakes
D. oceans | Evaporation changes liquid water to water vapor. Energy from the Sun causes water to evaporate. Most evaporation is from the oceans because they cover so much area. The water vapor rises into the atmosphere. | D: oceans. |
Which waves have the longest wavelengths but the least energy in the atmosphere?
Here are the choices:
A. radio waves
B. microwaves
C. light waves
D. channel waves | Some people are allergic to certain foods. Nuts and shellfish are common causes of food allergies. Other common causes of allergies include:. | A: radio waves. |
The effect of gravity on circulation means that it is harder to get blood up from the legs as the body takes on this?
Here are the choices:
A. horizontal orientation
B. frontal orientation
C. vertical orientation
D. dorsal orientation | Chapter 15 1 The heart rate increases to send more blood to the muscles, and the liver releases stored glucose to fuel the muscles. 3 The effect of gravity on circulation means that it is harder to get blood up from the legs as the body takes on a vertical orientation. 5 The release of urine in extreme fear. The sympathetic system normally constricts sphincters such as that of the urethra. 7 D 9 C 11 A 13 D 15 A 17 A 19 B 21 B 23 C 25 D 27 Whereas energy is needed for running away from the threat, blood needs to be sent to the skeletal muscles for oxygen supply. The additional fuel, in the form of carbohydrates, probably wouldn’t improve the ability to escape the threat as much as the diversion of oxygen-rich blood would hinder it. 29 The nerves that carry sensory information from the diaphragm enter the spinal cord in the cervical region where somatic sensory fibers from the shoulder and neck would enter. The brain superimposes this experience onto the sensory homunculus where the somatic nerves are connected. 31 Pupillary dilation and sweating, two functions lost in Horner’s syndrome, are caused by the sympathetic system. A tumor in the thoracic cavity may interrupt the output of the thoracic ganglia that project to the head and face. 33 Blood vessels, and therefore blood pressure, are primarily influenced by only the sympathetic system. There is no parasympathetic influence on blood pressure, so nicotine activation of autonomic ganglia will preferentially increase blood pressure. Also, cardiac muscle tissue is only modulated by autonomic inputs, so the conflicting information from both sympathetic and parasympathetic postganglionic fibers will cause arrhythmias. Both hypertension and arrhythmias are cardiac risk factors. | C: vertical orientation. |
Red blood cells, white blood cells and what other cell is found in blood?
Here are the choices:
A. hemoglobin
B. plasma cells
C. antibodies
D. platelets | Blood consists of liquid plasma, which contains dissolved substances, and three types of cells: red blood cells, white blood cells, and platelets. The main function of blood is transport. Blood also fights infections, repairs tissues, controls pH, and helps regulate body temperature. | D: platelets. |
How many dimensions can humans see in?
Here are the choices:
A. one
B. two
C. five
D. three | Humans can see in three dimensions and color. | D: three. |
What do you call the unhealthy synthetic lipids created when unsaturated fatty acids are artificially manufactured to have straight chains?
Here are the choices:
A. safflower acids
B. omega-3 fatty acids
C. trans fatty acids
D. polyunsaturated fats | Unsaturated fatty acids occur naturally in the bent shapes shown in Figure above . However, unsaturated fatty acids can be artificially manufactured to have straight chains like saturated fatty acids. Called trans fatty acids , these synthetic lipids were commonly added to foods until it was found that they increased the risk for certain health problems. Many food manufacturers no longer use trans fatty acids for this reason. | C: trans fatty acids. |
In what type of climate might one find deciduous trees?
Here are the choices:
A. thick continental
B. Dry Continental
C. humid continental
D. moist continental | Deciduous trees are common in humid continental climates. Conifer forests grow in the subarctic. | C: humid continental. |
Cellular respiration involves forming atp from what type of sugar?
Here are the choices:
A. fructose
B. sucrose
C. glucose
D. glutamate | Cellular respiration occurs in the cells of all living things. It takes place in the cells of both autotrophs and heterotrophs. All of them burn glucose to form ATP. | C: glucose. |
The magnitude of the wave function at a particular point in space is proportional to what property of the wave at that point?
Here are the choices:
A. frequency
B. Sounding
C. amplitude
D. voltage | The magnitude of the wave function at a particular point in space is proportional to the amplitude of the wave at that point. Many wave functions are complex functions, which is a mathematical term indicating that they contain. | C: amplitude. |
Representing a leap in scientific understanding, einstein described what as a dent in the fabric of space and time?
Here are the choices:
A. light
B. energy
C. motion
D. gravity | The above example shows how science generally advances. New evidence is usually used to improve earlier ideas rather than entirely replace them. In this way, scientists gradually refine their ideas and increase our understanding of the world. On the other hand, sometimes science advances in big leaps. This has happened when a scientist came up with a completely new way of looking at things. For example, Albert Einstein came up with a new view of gravity. He said it was really just a dent in the fabric of space and time. | D: gravity. |
Green algae and land plants are closely what?
Here are the choices:
A. foreign
B. different
C. related
D. unrelated | C: related. | |
How many alleles control a characteristic?
Here are the choices:
A. 2
B. 3
C. 8
D. 4 | A characteristic may be controlled by one gene with two alleles, but the two alleles may have a different relationship than the simple dominant-recessive relationship that you have read about so far. For example, the two alleles may have a codominant or incompletely dominant relationship. The former is illustrated by the flower in Figure below , and the latter in Figure below . | A: 2. |
All living things are able to produce what?
Here are the choices:
A. toxins
B. offspring
C. tissue
D. proteins | B: offspring. | |
What is the smallest volcanic landform that is formed from accumulation of many small fragments of ejected material?
Here are the choices:
A. cinder cones
B. edifice cones
C. log cones
D. concave cones | Cinder cones are the smallest volcanic landform. They are formed from accumulation of many small fragments of ejected material. | A: cinder cones. |
What are surface currents mainly caused by?
Here are the choices:
A. waves
B. winds
C. lightning
D. rains | Surface currents are like streams flowing through the surface of the ocean. They are caused mainly by winds. Earth’s rotation influences their direction. This is called the Coriolis effect. Surface currents may affect the climate of nearby coasts. | B: winds. |
What kind of solids are generally classified by the forces that hold their particles together and include ionic, metallic, covalent network, and molecular types?
Here are the choices:
A. crystalline solids
B. distinct solids
C. helium solids
D. flat solids | Crystalline solids are generally classified according the nature of the forces that hold its particles together. These forces are primarily responsible for the physical properties exhibited by the bulk solids. The following sections provide descriptions of the major types of crystalline solids: ionic, metallic, covalent network, and molecular. | A: crystalline solids. |
What can often be used to measure distance?
Here are the choices:
A. maps
B. graphs
C. histograms
D. models | Maps can often be used to measure distance. The map in the Figure below shows the route from Jordan’s house to his school. You can use the scale at the bottom of the map to measure the distance between these two points. | A: maps. |
Which single most factor is responsible for the extinction of hundreds of species of birds?
Here are the choices:
A. human actions
B. diet
C. habitat
D. animal actions | Hundreds of species of birds have gone extinct as a result of human actions. A well-known example is the passenger pigeon. It was once the most common bird in North America, but over-hunting and habitat destruction led to its extinction in the 1800s. Habitat destruction and use of the pesticide DDT explain the recent extinction of the dusky seaside sparrow. This native Florida bird was declared extinct in 1990. | A: human actions. |
The differing glycosidic linkages in starch and cellulose give the two molecules what kind of distinct shapes?
Here are the choices:
A. square
B. diamond
C. one-dimensional
D. three-dimensional | D: three-dimensional. | |
What is the angiosperm seed surrounded by?
Here are the choices:
A. egg
B. uterus
C. ovary
D. cone | The two major divisions of seed plants are the gymnosperms (seeds in cones) and angiosperms (seeds in ovaries of flowers). Figure below shows how the seeds of gymnosperms and angiosperms differ. Do you see the main difference between the two seeds? The angiosperm seed is surrounded by an ovary. | C: ovary. |
Which process helps bacteria in the gut break down the remains of the digested food?
Here are the choices:
A. decomposition
B. oxidation
C. fermentation
D. synthesis | Behind every fart 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. |
Unlike wild animals, what type of species are genetically uniform, making them more vulnerable to die-out from disease?
Here are the choices:
A. mammals
B. domestic species
C. urbane species
D. free-range species | Wild plants and animals maintain a valuable pool of genetic variation . This is important because domestic species are genetically uniform. This puts them at great risk of dying out due to disease. | B: domestic species. |
The diapsids diverged into two groups, the archosauromorpha (“ancient lizard form”) and the lepidosauromorpha (“scaly lizard form”) during what time period?
Here are the choices:
A. cenozoic
B. holocene
C. mesozoic
D. paleozoic | The diapsids diverged into two groups, the Archosauromorpha (“ancient lizard form”) and the Lepidosauromorpha (“scaly lizard form”) during the Mesozoic period (Figure 29.22). The lepidosaurs include modern lizards, snakes, and tuataras. The archosaurs include modern crocodiles and alligators, and the extinct pterosaurs (“winged lizard”) and dinosaurs (“terrible lizard”). Clade Dinosauria includes birds, which evolved from a branch of dinosaurs. | C: mesozoic. |
A few elements, called what, can conduct electricity, but not as well as metals?
Here are the choices:
A. synthetics
B. metalloids
C. gases
D. halogens | A few elements, called metalloids, can conduct electricity, but not as well as metals. Examples include silicon and germanium in group 14. Both become better conductors at higher temperatures. These elements are called semiconductors. | B: metalloids. |
Which type of eruptions created the entire ocean floor?
Here are the choices:
A. lava effusion
B. formation eruptions
C. fissure eruptions
D. fault eruptions | The most obvious landforms created by lava are volcanoes. These are mostly cinder cones, composite volcanoes, and shield volcanoes. Eruptions also take place through other types of vents, commonly from fissures ( Figure below ). The eruptions that created the entire ocean floor are essentially fissure eruptions. | C: fissure eruptions. |
What is damaged in the inner ear by loud sounds that cause hearing loss?
Here are the choices:
A. hair cells
B. tympanic membrane
C. ear drum
D. hammer and anvil | Loud sounds can cause hearing loss by damaging hair cells in the inner ear. The louder the sounds are, the less exposure is needed to cause hearing loss. | A: hair cells. |
The energy in sunlight is also known as what kind of energy?
Here are the choices:
A. potential energy
B. geothermal energy
C. solar energy
D. kinetic energy | The energy in sunlight, or solar energy, can be used to heat homes. It can also be used to produce electricity in solar cells. However, solar energy may not be practical in areas that are often cloudy. | C: solar energy. |
In what form is the heat absorbed when you heat ice and it reaches a temperature of 0 c?
Here are the choices:
A. mechanical energy
B. potential energy
C. radiation energy
D. geothermal energy | The heating curve shown is for water but other substances have similarly shaped heating curves. Suppose you begin with solid water (ice) at -30°C and add heat at a constant rate. The heat you add in the beginning will be absorbed as kinetic energy and the temperature of the solid will increase. When you reach a temperature of 0°C (the melting point for water), the heat you add is no longer absorbed as kinetic energy. Instead, the added heat is absorbed as potential energy and the particles separate from each other. During the flat part of the curve labeled “melting”, heat is being added constantly but the temperature does not increase. At the left edge of this flat line, the water is solid; by the time enough heat has been added to get to the right edge, the water is liquid, but maintains the same temperature. Once all the water is in the liquid form, the added heat will once again be absorbed as kinetic energy and the temperature will increase again. During the time labeled “water being heated as a liquid”, all the added heat is absorbed as kinetic energy. | B: potential energy. |
The sugar of one nucleotide binds to what group of the next nucleotide?
Here are the choices:
A. the alkaline
B. the phosphate
C. the protein
D. the chloride | The sugar of one nucleotide binds to the phosphate group of the next nucleotide. Alternating sugars and phosphate groups form the backbone of a nucleotide chain, as shown in Figure below . The bases, which are bound to the sugars, protrude from the backbone of the chain. In DNA, pairs of bases-one from each of two nucleotides-form the middle section of the molecule. | B: the phosphate. |
How does the image focused by the eye travel to the brain?
Here are the choices:
A. the secondary nerve
B. the sensory nerve
C. the optic nerve
D. the modulated nerve | The image focused by the eye travels through the optic nerve to the brain as electrical signals. The brain interprets the signals and “tells” us what we are seeing. | C: the optic nerve. |
If a human only has 45 chromosomes it is most likely due to a mistake during what?
Here are the choices:
A. mitosis
B. plexus
C. testis
D. meiosis | So far we have focused on traits due to one gene or several genes. But what about many genes? 100s or 1000s of genes? What would happen if an entire chromosome were missing or duplicated? What if a human had only 45 chromosomes? Or 47? This real possibility is usually due to mistakes during meiosis; the chromosomes do not fully separate from each other during sperm or egg formation. Specifically, nondisjunction is the failure of replicated chromosomes to separate during anaphase II. If a zygote forms from a gamete lacking a chromosome, a viable embryo cannot be produced. Most human abnormal chromosome numbers result in the death of the developing embryo, often before a woman even realizes she is pregnant. Occasionally, a zygote with an extra chromosome can become a viable embryo and develop. | D: meiosis. |
The digestive organs within the abdominal cavity are held in place by the peritoneum, a broad serous membranous sac made up of squamous epithelial tissue surrounded by this?
Here are the choices:
A. skin
B. mucus
C. bone
D. connective tissue | The Peritoneum The digestive organs within the abdominal cavity are held in place by the peritoneum, a broad serous membranous sac made up of squamous epithelial tissue surrounded by connective tissue. It is composed of two different regions: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which envelopes the abdominal organs (Figure 23.4). The peritoneal cavity is the space bounded by the visceral and parietal peritoneal surfaces. A few milliliters of watery fluid act as a lubricant to minimize friction between the serosal surfaces of the peritoneum. | D: connective tissue. |
What season causes people to look forward to spring?
Here are the choices:
A. summer
B. winter
C. fall
D. autumn | In the winter, many people find the snow and ice beautiful. They enjoy getting out to ski or ice-skate. Others don’t find that time of year to be so much fun. When the snow melts, the roads get very sloppy and messy. Those people look forward to spring when all the ice and snow are gone and the weather is warmer. | B: winter. |
What are the narrowest blood vessels, where oxygen is transferred into body cells?
Here are the choices:
A. arteries
B. muscles
C. viens
D. capillaries | Red blood cells are flat, round, and very small. Their small size allows easy maneuverability through the capillaries, the narrowest blood vessels, where oxygen is transferred into body cells. | D: capillaries. |
What is quantified by measuring the number of decay processes per unit time?
Here are the choices:
A. temperature
B. microwave power
C. fossil age
D. radioactivity | Radioactivity is quantified by measuring the number of decay processes per unit time. For example, we can measure radioactivity in terms of counts per minute (cpm), where each "count" is a single decay process, such as the emission of an α-particle. A sample of one particular isotope may have an activity of 5,000 cpm, while an equal amount of another isotope might result in a radiation level of only 250 cpm. For a given nucleus, the amount of radioactivity gives a rough indication of the amount of the radioisotope present – the higher the activity, the more of the radioactive isotope in the sample. | D: radioactivity. |
What is a measure of the force of gravity pulling on an object of a given mass?
Here are the choices:
A. solidity
B. weight
C. scale
D. effect | Newton’s second law of motion explains the weight of objects. Weight is a measure of the force of gravity pulling on an object of a given mass. It’s the force (F) in the acceleration equation that was introduced above:. | B: weight. |
What is the atomic number?
Here are the choices:
A. Number of electrons
B. Number of neutrons
C. number of protons
D. Speed of electrons | In the modern periodic table, elements are organized by atomic number. The atomic number is the number of protons in an atom of an element. This number is unique for each element, so it seems like an obvious way to organize the elements. (Mendeleev used atomic mass instead of atomic number because protons had not yet been discovered when he made his table. ) In the modern table, atomic number increases from left to right across each period. It also increases from top to bottom within each group. How is this like Mendeleev’s table?. | C: number of protons. |
Some isotopes are stable indefinitely, while others are radioactive and do what through a characteristic form of emission?
Here are the choices:
A. expand
B. decay
C. bond
D. replicate | Whether or not a given isotope is radioactive is a characteristic of that particular isotope. Some isotopes are stable indefinitely, while others are radioactive and decay through a characteristic form of emission. As time passes, less and less of the radioactive isotope will be present, and the level of radioactivity decreases. An interesting and useful aspect of radioactive decay is half-life, which is the amount of time it takes for one-half of a radioactive isotope to decay. The half-life of a specific radioactive isotope is constant; it is unaffected by conditions and is independent of the initial amount of that isotope. Consider the following example. Suppose we have 100.0 g of tritium (a radioactive isotope of hydrogen). It has a half-life of 12.3 y. After 12.3 y, half of the sample will have decayed from hydrogen-3 to helium-3 by emitting a beta particle, so that only 50.0 g of the original tritium remains. After another 12.3 y— making a total of 24.6 y—another half of the remaining tritium will have decayed, leaving 25.0 g of tritium. After another 12.3 y—now a total of 36.9 y—another half of the remaining tritium will have decayed, leaving 12.5 g. This sequence of events is illustrated in Figure 15.1 "Radioactive Decay". Figure 15.1 Radioactive Decay. | B: decay. |
Cellular respiration uses oxygen to harvest what from organic molecules?
Here are the choices:
A. energy
B. light
C. water
D. chlorophyll | the evolution of cellular respiration, which used oxygen to help harvest energy from organic molecules. | A: energy. |
A red blood cell will swell and burst when placed in a?
Here are the choices:
A. hypotonic solution
B. exothermic solution
C. dissolved solution
D. acidic solution | A cell that does not have a rigid cell wall, such as a red blood cell, will swell and lyse (burst) when placed in a hypotonic solution. Cells with a cell wall will swell when placed in a hypotonic solution, but once the cell is turgid (firm), the tough cell wall prevents any more water from entering the cell. When placed in a hypertonic solution, a cell without a cell wall will lose water to the environment, shrivel, and probably die. In a hypertonic solution, a cell with a cell wall will lose water too. The plasma membrane pulls away from the cell wall as it shrivels, a process called plasmolysis . Animal cells tend to do best in an isotonic environment, plant cells tend to do best in a hypotonic environment. This is demonstrated in Figure below . | A: hypotonic solution. |
Which type of lava lavas are less viscous and erupt effusively?
Here are the choices:
A. Intermediate lava
B. mafic
C. Felsic lava
D. Ultramafic lava | Felsic lavas are more viscous and erupt explosively or do not erupt. Mafic lavas are less viscous and erupt effusively. | B: mafic. |
What are often formed biologically during the breakdown of proteins in animal cells, having the smell of death and decay?.
Here are the choices:
A. amines
B. acids
C. enzymes
D. ketones | Amines generally have rather pungent or noxious odors. Ammonia can be considered the simplest amine and has a very distinctive odor. Methylamine has an unpleasant odor associated with dead fish. Amines are often formed biologically during the breakdown of proteins in animal cells, and so many have the smell of death and decay. Putrescine and cadaverine are two such amines and are aptly named for their foul odors. The toxins which many animals use as a form of defense are frequently amines. Amines are used industrially as dyes and in many drugs. | A: amines. |
What produces the centripetal force to keep the earth orbiting the sun?
Here are the choices:
A. weight
B. motion
C. gravity
D. heat | Centripetal force is, simply, the force that causes centripetal acceleration. Objects that move in uniform circular motion all have an acceleration toward the center of the circle and therefore, they must also suffer a force toward the center of the circle. That force is the centripetal force. For orbiting satellites, such as the moon orbiting the earth or the earth orbiting the sun, the centripetal force is produced by gravity. When an Olympic hammer thrower whirls a massive ball on a chain, the centripetal force is created by the athlete and transmitted by the chain. | C: gravity. |
Group 13 of the periodic table is also called what?
Here are the choices:
A. the boron group
B. manganese group
C. iron group
D. nitrogen group | Group 13 of the periodic table is also called the boron group because boron (B) is the first element at the top of the group (see Figure below ). Boron is also the only metalloid in this group. The other four elements in the group—aluminum (Al), gallium (Ga), indium (In), and thallium (Tl)—are all metals. Group 13 elements have three valence electrons and are fairly reactive. All of them are solids at room temperature. | A: the boron group. |
What type of tissue transports water and minerals in a vascular plant?
Here are the choices:
A. capillaries
B. xylem
C. collagen
D. chlorophyll | 25.4 Seedless Vascular Plants Vascular systems consist of xylem tissue, which transports water and minerals, and phloem tissue, which transports sugars and proteins. With the development of the vascular system, there appeared leaves to act as large photosynthetic organs, and roots to access water from the ground. Small uncomplicated leaves are microphylls. Large leaves with vein patterns are megaphylls. Modified leaves that bear sporangia are sporophylls. Some sporophylls are arranged in cone structures called strobili. | B: xylem. |
What produces enzymes that digest carbohydrates in plant cell walls?
Here are the choices:
A. pollen
B. bacteria
C. algae
D. protists | Break down some substances in food that cannot be digested, such as fiber and some starches and sugars. Bacteria produce enzymes that digest carbohydrates in plant cell walls. Most of the nutritional value of plant material would be wasted without these bacteria. These help us digest plant foods like spinach. | B: bacteria. |
At what temperature does solid water melt to a liquid?
Here are the choices:
A. at temperatures above 0 degrees c
B. below 32 degrees c
C. above 32 degrees c
D. below 0 degrees c | The process in which rocks or other solids change to liquids is called melting. Melting occurs when particles of a solid absorb enough energy to partly overcome the force of attraction holding them together. This allows them to move out of their fixed positions and slip over one another. Melting, like other changes of state, is a physical change in matter, so it doesn’t change the chemical makeup or chemical properties of matter. | A: at temperatures above 0 degrees c. |
How many more legs do spiders have compared to insects?
Here are the choices:
A. six
B. two
C. four
D. one | Although spiders and insects are both arthropods, a spider is not an insect. One key difference is that insects have six legs, while spiders have eight legs. | B: two. |
Almost all energy at earth's surface comes from where?
Here are the choices:
A. wind
B. the sun
C. another sun
D. oceans | Almost all energy at Earth's surface comes from the Sun. The Sun’s energy heats the planet and the air around it. This causes the atmosphere to move and create weather. Sunlight also powers photosynthesis and life on Earth. | B: the sun. |
What is the first step in protein synthesis?
Here are the choices:
A. transcription
B. reproduction
C. differentiation
D. mutation | Transcription is the first step in protein synthesis. It takes place in the nucleus. During transcription, a strand of DNA is copied to make a strand of mRNA. How does this happen? It occurs by the following steps, as shown in Figure below . | A: transcription. |
What branch of biology focuses on heredity?
Here are the choices:
A. Epidemiology
B. ontology
C. semiotics
D. genetics | Genetics is the branch of biology that focuses on heredity. The basics of heredity are similar for all organisms that reproduce sexually: the offspring receive one set of genetic material from one parent and the other set from the other parent. But are there aspects of genetics that are specific for humans? Let’s find out. | D: genetics. |
Stars are born in clouds, and they form and grow dense due to what force?
Here are the choices:
A. Big Bang theory
B. coreolis effect
C. kinetic energy
D. gravity | Stars are born in clouds like the one in the picture. Gravity pulls material together. When it is extremely dense, it begins nuclear fusion. That is, it becomes a star. We can see places where stars are being born right now. Of course, it takes light a long time to travel to us. So what we see right now may have happened many millions or even billions of years ago. | D: gravity. |
What has atoms with unstable nuclei?
Here are the choices:
A. microwaves
B. radionuclide
C. radioisotope
D. hydrocarbon | A radioisotope has atoms with unstable nuclei. Unstable nuclei naturally decay, or break down. They lose energy and particles and become more stable. As nuclei decay, they gain or lose protons, so the atoms become different elements. This is illustrated in the Figure below . The original, unstable nucleus is called the parent nucleus. After it loses a particle (in this case a type of particle called an alpha particle), it forms a daughter nucleus, with a different number of protons. | C: radioisotope. |
What is the tissue beneath a mollusks' shell called?
Here are the choices:
A. mantle
B. skin
C. mucous
D. cartilage | Mollusks have ventral nerve cords. The tissue beneath the shell is called the mantle. The mantle cavity contains hemolymph. Figure 15.33 Which of the following statements about common features of chordates is true? a. The dorsal hollow nerve cord is part of the chordate central nervous system. In vertebrate fishes, the pharyngeal slits become the gills. Humans are not chordates because humans do not have a tail. Vertebrates do not have a notochord at any point in their development; instead, they have a vertebral column. | A: mantle. |
What is formed from an alcohol that loses water?
Here are the choices:
A. alcohols
B. Bonds
C. amines
D. alkenes | Alcohols can lose water to form alkenes. | D: alkenes. |
What is the division of the body into multiple parts called?
Here are the choices:
A. organ-level organization
B. segmentation
C. compression
D. transverse | Segmentation evolved next. This is a division of the body into multiple segments. Both the earthworm and ant pictured in Figure below have segmented bodies. This trait increases flexibility. It permits a wider range of motion. All annelids and arthropods are segmented. Arthropods also evolved jointed appendages. For example, they evolved jointed legs for walking and “feelers” (antennae) for sensing. | B: segmentation. |
What reproductive method has two parents involved?
Here are the choices:
A. budding
B. pollination
C. sexually
D. mitosis | Most reptiles reproduce sexually, meaning there are two parents involved. In some families of lizards and one snake family, however, asexual reproduction is possible. This is when only one parent is involved in creating new life. For example, the gecko females can make tiny clones of themselves without the aid of a male. | C: sexually. |
In many cases, the alkali metal amide salt (mnh2) is not very soluble in liquid ammonia and does what?
Here are the choices:
A. evaporates
B. settles
C. precipitates
D. isolates | where the (am) designation refers to an ammonia solution, analogous to (aq) used to indicate aqueous solutions. Without a catalyst, the reaction in Equation 21.20 tends to be rather slow. In many cases, the alkali metal amide salt (MNH2) is not very soluble in liquid ammonia and precipitates, but when dissolved, very concentrated solutions of the alkali metal are produced. One mole of Cs metal, for example, will dissolve in as little as 53 mL (40 g) of liquid ammonia. The pure metal is easily recovered when the ammonia evaporates. Solutions of alkali metals in liquid ammonia are intensely colored and good conductors of electricity due to the presence of solvated electrons (e−, NH3), which are not attached to single atoms. A solvated electron is loosely associated with a cavity in the ammonia solvent that is stabilized by hydrogen bonds. Alkali metal–liquid ammonia solutions of about 3 M or less are deep blue (Figure 21.11 "Alkali Metal–Liquid Ammonia Solutions") and conduct electricity about 10 times better than an aqueous NaCl solution because of the high mobility of the solvated electrons. As the concentration of the metal increases above 3 M, the color changes to metallic bronze or gold, and the conductivity increases to a value comparable with that of the pure liquid metals. | C: precipitates. |
An example of beta decay is the emission of an electron by a carbon-14 what?
Here are the choices:
A. protons
B. molecules
C. nucleus
D. ion | Transmutation also occurs when a nucleus undergoes decay. An example of beta decay is the emission of an electron by a carbon-14 nucleus. | C: nucleus. |
Which theory describes the distribution of electrons in molecules in much the same way that the distribution of electrons in atoms is described using atomic orbitals?
Here are the choices:
A. atomic orbital theory
B. molecular distribution theory
C. atomic distribution theory
D. molecular orbital theory | Molecular orbital theory describes the distribution of electrons in molecules in much the same way that the distribution of electrons in atoms is described using atomic orbitals. Using quantum mechanics, the behavior of an electron in a molecule is still described by a wave function, Ψ, analogous to the behavior in an atom. Just like electrons around isolated atoms, electrons around atoms in molecules are limited to discrete (quantized) energies. The region of space in which a valence electron in a molecule is likely to be found is called a molecular orbital (Ψ2). Like an atomic orbital, a molecular orbital is full when it contains two electrons with opposite spin. We will consider the molecular orbitals in molecules composed of two identical atoms (H2 or Cl2, for example). Such molecules are called homonuclear diatomic molecules. In these diatomic molecules, several types of molecular orbitals occur. The mathematical process of combining atomic orbitals to generate molecular orbitals is called the linear combination of atomic orbitals (LCAO). The wave function describes the wavelike properties of an electron. Molecular orbitals are combinations of atomic orbital wave functions. Combining waves can lead to constructive interference, in which peaks line up with peaks, or destructive interference, in which peaks line up with troughs. | D: molecular orbital theory. |
Oversecretion of insulin can cause what?
Here are the choices:
A. inflammation
B. hypoxia
C. hyperglycemia
D. hypoglycemia | This animation (http://openstaxcollege. org/l/insulin) describe the role of insulin and the pancreas in diabetes. Impaired insulin function can lead to a condition called diabetes mellitus, the main symptoms of which are illustrated in Figure 37.10. This can be caused by low levels of insulin production by the beta cells of the pancreas, or by reduced sensitivity of tissue cells to insulin. This prevents glucose from being absorbed by cells, causing high levels of blood glucose, or hyperglycemia (high sugar). High blood glucose levels make it difficult for the kidneys to recover all the glucose from nascent urine, resulting in glucose being lost in urine. High glucose levels also result in less water being reabsorbed by the kidneys, causing high amounts of urine to be produced; this may result in dehydration. Over time, high blood glucose levels can cause nerve damage to the eyes and peripheral body tissues, as well as damage to the kidneys and cardiovascular system. Oversecretion of insulin can cause hypoglycemia, low blood glucose levels. This causes insufficient glucose availability to cells, often leading to muscle weakness, and can sometimes cause unconsciousness or death if left untreated. | D: hypoglycemia. |
The first few species to colonize a disturbed area are called what?
Here are the choices:
A. pioneer species
B. colonization species
C. original species
D. producer species | The first few species to colonize a disturbed area are called pioneer species. In primary succession, pioneer species must be organisms that can live on bare rock. They usually include bacteria and lichens (see Figure below ). Along with wind and water, the pioneer species help weather the rock and form soil. Once soil begins to form, plants can move in. The first plants are usually grasses and other small plants that can grow in thin, poor soil. As more plants grow and die, organic matter is added to the soil. This improves the soil and helps it hold water. The improved soil allows shrubs and trees to move into the area. | A: pioneer species. |
What are the two loops of blood flow in the cardiovascular system?
Here are the choices:
A. systolic and diastolic
B. pulmonary and systemic
C. aerobic and anaerobic
D. anabolic and metabolic | The cardiovascular system circulates blood through two different loops. Pulmonary circulation is a loop that carries blood between the heart and lungs. Systemic circulation is a loop that carries blood between the heart and the rest of the body. | B: pulmonary and systemic. |
What is the name of a group of hereditary diseases that affect the body's ability to control blood clotting?
Here are the choices:
A. hemophilia
B. anemia
C. hypertension
D. arithmya | Hemophilia is the name of a group of hereditary diseases that affect the body's ability to control blood clotting. Hemophilia is caused by a lack of clotting factors in the blood. Clotting factors are normally released by platelets. Since people with hemophilia cannot produce clots, any cut can put a person at risk of bleeding to death. The risk of internal bleeding is also increased in hemophilia, especially into muscles and joints. This disease affected the royal families of Europe. | A: hemophilia. |
Protists which use their tails to eat are called what?
Here are the choices:
A. swimmers
B. flagellators
C. filter-feeders
D. cycle - feeders | Some animal-like protists use their "tails" to eat. These protists are called filter-feeders . They acquire nutrients by constantly whipping their tails, called flagellum , back and forth. The whipping of the flagellum creates a current that brings food into the protist. | C: filter-feeders. |
What term is used to describe foods containing active cultures of beneficial bacteria?
Here are the choices:
A. carotenoids
B. sembiotic
C. antibiotics
D. probiotic | Yogurt is a good source of calcium. Yogurt also contains active cultures of "good" bacteria. Foods that contain these beneficial bacteria are sometimes called "probiotic. ". | D: probiotic. |
What helps control the muscles and maintain balance?
Here are the choices:
A. circulatory system
B. lymphatic system
C. muscular system
D. nervous system | Staying balanced when riding a scooter requires control over the body’s muscles. The nervous system controls the muscles and maintains balance. | D: nervous system. |
What unit of power is equal to 1 joule of energy per second?
Here are the choices:
A. volt
B. byte
C. watt
D. hertz | The rate at which a device changes electric current to another form of energy is called electric power . The SI unit for power—including electric power—is the watt. A watt equals 1 joule of energy per second. High wattages are often expressed in kilowatts, where 1 kilowatt equals 1000 watts. The power of an electric device, such as a hair dryer, can be calculated if you know the voltage of the circuit and how much current the device receives. The following equation is used:. | C: watt. |
What is just below the cerebrum and coordinates body movements?
Here are the choices:
A. hypothalamus
B. spinal cord
C. bloodstream
D. cerebellum | The cerebellum is just below the cerebrum. It coordinates body movements. Many nerve pathways link the cerebellum with motor neurons throughout the body. | D: cerebellum. |
What part of blood releases clotting factors?
Here are the choices:
A. hemoglobin
B. platelets
C. white blood cells
D. erythrocytes | Platelets ( Figure below ) are very small, but they are very important in blood clotting. Platelets are not cells. They are sticky little pieces of larger cells. Platelets bud off large cells that stay in the bone marrow. When a blood vessel gets cut, platelets stick to the injured areas. They release chemicals called clotting factors, which cause proteins to form over the wound. This web of proteins catches red blood cells and forms a clot. This clot stops more blood from leaving the body through the cut blood vessel. The clot also stops bacteria from entering the body. Platelets survive in the blood for ten days before they are removed by the liver and spleen. | B: platelets. |
Adding carbon to iron makes what type of metal?
Here are the choices:
A. steel
B. ions
C. plastic
D. titanium | Metals such as iron are useful for many purposes because of their unique properties. For example, they can conduct electricity and bend without breaking. However, pure metals may be less useful than mixtures of metals with other elements. For example, adding a little carbon to iron makes it much stronger. This mixture is called steel. Steel is so strong that it can hold up huge bridges, like the one pictured above. Steel is also used to make skyscrapers, cargo ships, cars, and trains. Steel is an example of an alloy. | A: steel. |
Which structure includes sugar-phosphate "backbones", composed of alternating phosphate groups and deoxyribose sugars, and nitrogenous bases?
Here are the choices:
A. dna double helix
B. molecule double helix
C. mulecular triplex
D. dna triple helix | The DNA double helix. The two sides are the sugar-phosphate backbones, composed of alternating phosphate groups and deoxyribose sugars. The nitrogenous bases face the center of the double helix. As the base-pairing rules tell us, A always pairs with T, and G always pairs with C. | A: dna double helix. |
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