question stringlengths 1 6.54k | choices listlengths 4 4 | answer stringclasses 4
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The nitrogen that enters living systems by nitrogen fixation is successively converted from organic nitrogen back into nitrogen gas by what? | [
"viruses",
"bacteria",
"algae",
"pollen"
] | B | The Nitrogen Cycle Getting nitrogen into the living world is difficult. Plants and phytoplankton are not equipped to incorporate nitrogen from the atmosphere (which exists as tightly bonded, triple covalent N2) even though this molecule comprises approximately 78 percent of the atmosphere. Nitrogen enters the living wo... | train | sciq | null |
What term describes the amount of solute in a given amount of solution? | [
"temperature",
"density",
"concentration",
"cloudiness"
] | C | The concentration of a solution is the amount of solute in a given amount of solution. A dilute solution has a low concentration of solute. A concentrated solution has a high concentration of solute. | train | sciq | null |
Which process helps absorptive protists absorb food molecules across their cell membranes? | [
"activation",
"secretion",
"metabolism",
"diffusion"
] | D | Absorptive protists absorb food molecules across their cell membranes. This occurs by diffusion. These protists are important decomposers. | train | sciq | null |
When matter recycles and changes state what does it gain or lose by doing so? | [
"volume",
"energy",
"fuel",
"density"
] | B | Matter can exist in one of several different states, including a gas, liquid, or solid state. States of matter differ in the amount of energy their molecules have. When matter recycles, it changes state by gaining or losing energy. | train | sciq | null |
Where does oxygen enter the blood? | [
"in the lungs",
"in the liver",
"in the heart",
"in the veins"
] | A | train | sciq | null | |
What kind of compounds change color when bases come into contact with them, so they can be used to detect bases? | [
"indicators",
"parameters",
"metals",
"liquid"
] | A | Certain compounds, called indicators, change color when bases come into contact with them, so they can be used to detect bases. An example of an indicator is a compound called litmus. It is placed on small strips of paper that may be red or blue. If you place a few drops of a base on a strip of red litmus paper, the pa... | train | sciq | null |
Concentric circles that spread out through the water around the droplets are actually types of what moving through the water? | [
"waves",
"troughs",
"lines",
"winds"
] | A | No doubt you’ve seen this happen. Droplets of water fall into a body of water, and concentric circles spread out through the water around the droplets. The concentric circles are waves moving through the water. | train | sciq | null |
The smallest units of matter that retain the unique properties of an element are known as what? | [
"atoms",
"molecules",
"neutrons",
"protons"
] | A | All matter is made of tiny particles. Protons, neutrons, and electrons form atoms that bond together to create molecules. Atoms are the smallest units that have the properties of an element. Molecules are the smallest units of a compound. Chemical bonds hold molecules together. Molecules form the different types of min... | train | sciq | null |
What is a process that changes some chemical substances into other chemical substances? | [
"a bio reaction",
"a chemical reaction",
"cellular respiration",
"spontaneous mutation"
] | B | A chemical reaction is a process that changes some chemical substances into other chemical substances. The substances that start a chemical reaction are called reactants . The substances that form as a result of a chemical reaction are called products . During the reaction, the reactants are used up to create the produ... | train | sciq | null |
What type of lens and mirrors have a negative focal length? | [
"converging",
"convexing",
"subverging",
"diverging"
] | D | The focal length , , of a lens or mirror is the distance from the surface of the lens or mirror to the place where the light is focused. This is called the focal point or focus . For diverging lenses or mirrors, the focal length is negative. | train | sciq | null |
What is the formation of organs from the germ layers called? | [
"photosynthesis",
"synaptogenesis",
"biosynthesis",
"organogenesis"
] | D | 43.7 Organogenesis and Vertebrate Formation Organogenesis is the formation of organs from the germ layers. Each germ layer gives rise to specific tissue types. The first stage is the formation of the neural system in the ectoderm. The mesoderm gives rise to somites and the notochord. Formation of vertebrate axis is ano... | train | sciq | null |
What must two nuclei do for fusion to occur? | [
"collide",
"melt",
"explode",
"repel each other"
] | A | Two nuclei must collide for fusion to occur. High temperatures are required to give the nuclei enough kinetic energy to overcome the very strong repulsion resulting from their positive charges. A nuclear reactor consists of the following: 1. A nuclear fuel. A fissionable isotope must be present in large enough quantiti... | train | sciq | null |
What determines the ability of soil particles to bind many nutrients? | [
"layer charges",
"currents charges",
"surface pulses",
"surface charges"
] | D | train | sciq | null | |
Enthalpy is a measure of the total energy of what kind of system? | [
"thermodynamic",
"planetary",
"hypodermic",
"macroscopic"
] | A | Reactions can proceed by themselves if they are exergonic or exothermic, that is if they release energy. The associated free energy of the reaction is composed of two different thermodynamic quantities, enthalpy and entropy. Enthalpy is a measure of the total energy of a thermodynamic system. The change in enthalpy is ... | train | sciq | null |
In eukaryotes, the new mrna is not yet ready for translation. it must go through more processing before it leaves where? | [
"molecules",
"nucleus",
"protons",
"Electrons"
] | B | In eukaryotes, the new mRNA is not yet ready for translation. It must go through more processing before it leaves the nucleus. This may include splicing, editing, and polyadenylation. These processes modify the mRNA in various ways. Such modifications allow a single gene to be used to make more than one protein. | train | sciq | null |
What term describes the splitting of the nucleus of an atom into two smaller nuclei? | [
"nuclean fusion",
"nuclear fission",
"atomic reaction",
"critical fission"
] | B | Nuclear fission is the splitting of the nucleus of an atom into two smaller nuclei. This type of reaction releases a great deal of energy from a very small amount of matter. It begins when the nucleus of a radioactive atom gains a neutron. | train | sciq | null |
What type of contamination causes almost 90% of diarrheal disease worldwide? | [
"ground contamination",
"water supply contamination",
"air contamination",
"food contamination"
] | B | Unsafe water supplies have drastic effects on human health. Waterborne diseases are diseases due to microscopic pathogens in fresh water. These diseases can be caused by protozoa, viruses, bacteria, and intestinal parasites. In many parts of the world there are no water treatment plants. If sewage or animal manure gets... | train | sciq | null |
Why is respiratory acidosis considered to be problematic? | [
"causes suffocation",
"excess co2 in blood",
"causes acid stomach",
"excess oxygen in blood"
] | B | Metabolic acidosis is problematic, as lower-than-normal amounts of bicarbonate are present in the blood. The pCO2 would be normal at first, but if compensation has occurred, it would decrease as the body reestablishes the proper ratio of bicarbonate and carbonic acid/CO2. Respiratory acidosis is problematic, as excess ... | train | sciq | null |
When light strikes rhodopsin, the g-protein transducin is activated, which in turn activates what? | [
"phosphodiesterase",
"hydrolysis",
"photosynthesis",
"aldosterone"
] | A | Figure 36.20 When light strikes rhodopsin, the G-protein transducin is activated, which in turn activates phosphodiesterase. Phosphodiesterase converts cGMP to GMP, thereby closing sodium channels. As a result, the membrane becomes hyperpolarized. The hyperpolarized membrane does not release glutamate to the bipolar ce... | train | sciq | null |
In what stage of photosynthesis does the calvin cycle occur? | [
"fourth",
"second",
"third",
"first"
] | B | The Calvin cycle occurs in the second stage of photosynthesis. This stage takes place in the stroma of the chloroplast. In the Calvin cycle, carbon dioxide is used to produce glucose (sugar) using the energy stored in ATP and NADPH. The energy is released from these molecules when ATP loses phosphate (P i ) to become A... | train | sciq | null |
All of the planets rotate on their axes in the same direction that they move around the sun, except for which one? | [
"uranus",
"venus",
"Jupiter",
"Saturn"
] | A | All of the planets rotate on their axes in the same direction that they move around the Sun. Except for Uranus. Uranus is tilted on its side. Its axis is almost parallel to its orbit. So Uranus rolls along like a bowling ball as it revolves around the Sun. How did Uranus get this way? Scientists think that the planet w... | train | sciq | null |
What is the process by which organisms change in small ways over time? | [
"spontaneous mutation",
"adaptation",
"microevolution",
"natural selection"
] | C | Microevolution is the process by which organisms change in small ways over time. | train | sciq | null |
What regulates the cell cycle only when they are tightly bound to cdks? | [
"hormones",
"kinases",
"subclades",
"cyclins"
] | D | Cyclins regulate the cell cycle only when they are tightly bound to Cdks. To be fully active, the Cdk/cyclin complex must also be phosphorylated in specific locations. Like all kinases, Cdks are enzymes (kinases) that phosphorylate other proteins. Phosphorylation activates the protein by changing its shape. The protein... | train | sciq | null |
Einstein developed a theory about how electromagnetic radiation can behave as both a wave and what else? | [
"particle",
"bacteria",
"sound",
"energy"
] | A | In 1905, the physicist Albert Einstein developed a new theory about electromagnetic radiation. The theory is often called the wave-particle theory . It explains how electromagnetic radiation can behave as both a wave and a particle. Einstein argued that when an electron returns to a lower energy level and gives off ele... | train | sciq | null |
What type of proteins are only temporarily associated with the membrane? | [
"visual membrane proteins",
"peripheral membrane proteins",
"sensitive rod proteins",
"peripheral oxidation proteins"
] | B | Peripheral membrane proteins are proteins that are only temporarily associated with the membrane. They can be easily removed, which allows them to be involved in cell signaling. Peripheral proteins can also be attached to integral membrane proteins, or they can stick into a small portion of the lipid bilayer by themsel... | train | sciq | null |
Which organisms break down either organic or inorganic molecules to supply energy for the cell? | [
"photoreactive organisms",
"asexual organisms",
"chemotrophic organisms",
"spicule organisms"
] | C | Chemotrophic organisms break down either organic or inorganic molecules to supply energy for the cell. Some chemotrophic organisms can also use their organic energy-supplying molecules as a carbon supply, which would make them chemoheterotrophs. | train | sciq | null |
What are the things moving under the earth's mantle that move the crust? | [
"plates",
"lava channels",
"crystals",
"ridges"
] | A | What portion of Earth makes up the “plates” in plate tectonics? Again, the answer came about in part due to war. In this case, the Cold War. The scientists set up seismometer networks during the 1950s and early 1960s. The purpose was to see if other nations were testing atomic bombs. Since seismometers measure ground s... | train | sciq | null |
Although they look like big rocks, what structures that serve as habitats for many different types of ocean life are actually alive? | [
"natural reefs",
"southern reefs",
"coral reefs",
"new forming reefs"
] | C | Coral reefs ( Figure below ) look like big rocks, but they are actually alive. They are built from cnidarians called corals. The corals are sessile (non-moving) polyps that can use their tentacles to feed on ocean creatures that pass by. Their skeletons are made up of calcium carbonate, which is also known as limestone... | train | sciq | null |
What type of reactions are chemical reactions that release energy? | [
"ozonic reactions",
"exothermic reactions",
"sulfuric reactions",
"biochemical reactions"
] | B | Chemical reactions that release energy are called exothermic reactions . An example is the combustion of methane described at the beginning of this lesson. In organisms, exothermic reactions are called catabolic reactions . Catabolic reactions break down molecules into smaller units. An example is a decomposition react... | train | sciq | null |
Fossil fuels and coal are examples of what kind of resources? | [
"renewable",
"valuable",
"nonrenewable",
"reusable"
] | C | Nonrenewable resources exist in fixed amounts. They can be used up. Examples include fossil fuels such as coal. | train | sciq | null |
What type of compound contains atoms of two or more different elements in its ring structure? | [
"hydrocarbon",
"polymer",
"heterocyclic",
"aldehyde"
] | C | In some amines, the nitrogen atom replaces a carbon atom in an aromatic hydrocarbon. Pyridine (Figure 20.17) is one such heterocyclic amine. A heterocyclic compound contains atoms of two or more different elements in its ring structure. | train | sciq | null |
What is formed when atoms of different elements combine in a chemical reaction? | [
"dust",
"toxins",
"crystals",
"compounds"
] | D | For each of the following situations, tell whether the rate of the reaction would increase or decrease, and explain your answer in terms of collision theory. The concentration of a reactant is doubled. | train | sciq | null |
What type of electricity is formed when a negative charge builds up and are transferred? | [
"alternating current",
"static electricity",
"direct current",
"neutron energy"
] | B | Static electricity is a buildup of electric charges on objects. Charges build up when negative electrons are transferred from one object to another. The object that gives up electrons becomes positively charged, and the object that accepts the electrons becomes negatively charged. This can happen in several ways. | train | sciq | null |
What important liquid is stored throughout the earth in the oceans, underground, and in ice? | [
"lava",
"water",
"air",
"oil"
] | B | Water cycling is extremely important to ecosystem dynamics. Water has a major influence on climate and, thus, on the environments of ecosystems, some located on distant parts of the Earth. Most of the water on Earth is stored for long periods in the oceans, underground, and as ice. Figure 46.13 illustrates the average ... | train | sciq | null |
What results when a warm air mass runs into a cold air mass? | [
"rough front",
"cool front",
"dry front",
"warm front"
] | D | When a warm air mass runs into a cold air mass, it creates a warm front ( Figure below ). The warm air mass is moving faster than the cold air mass. The warm air mass then flows up over the cold air mass. As the warm air rises, it cools. This brings about clouds and sometimes light precipitation. Warm fronts move slowl... | train | sciq | null |
Which type of double bond has a sigma bond and a pi bond? | [
"sodium - oxygen bond",
"Covalent Bonds",
"carbon-oxygen bond",
"dioxide - oxygen bond"
] | C | Has a double-bonded carbon-oxygen bond (one sigma bond and one pi bond). The carbon to which the oxygen is attached has one hydrogen atom connected to it. | train | sciq | null |
Has the average annual temperature on earth been rising or falling for the past 100 years? | [
"fluctuating",
"falling",
"unchanged",
"rising"
] | D | The average annual temperature on Earth has been rising for the past 100 years. | train | sciq | null |
The majoirty of modern gymnosperms belong to what group, which includes pine trees? | [
"Pinophytes",
"clusters",
"conifers",
"stems"
] | C | There are only about 1,000 living species of gymnosperms, whereas there are hundreds of thousands of living species of angiosperms. Living gymnosperms are typically classified in the divisions described in the Table below . Most modern gymnosperms are trees with woody trunks. The majority are conifers such as pine tree... | train | sciq | null |
A circuit must be what in order for electric devices such as light bulbs to work? | [
"down",
"open",
"cyclical",
"closed"
] | D | A circuit must be closed for electric devices such as light bulbs to work. The arrows in the diagram show the direction in which electrons flow through the circuit. The current is considered to flow in the opposite direction. | train | sciq | null |
What type of radiation from the sun reaches earth across space striking everything on earth’s surface? | [
"particle",
"static",
"electromagnetic",
"seismic"
] | C | Electromagnetic radiation from the sun reaches Earth across space. It strikes everything on Earth’s surface, including these volleyball players. | train | sciq | null |
What happens if a catalyst runs out? | [
"reaction increases",
"reaction slows",
"variety slows",
"variety increases"
] | B | Chemistry in Everyday Life Transition Metal Catalysts One of the most important applications of transition metals is as industrial catalysts. As you recall from the chapter on kinetics, a catalyst increases the rate of reaction by lowering the activation energy and is regenerated in the catalytic cycle. Over 90% of all... | train | sciq | null |
What type of mammals are humans? | [
"marsupial mammals",
"placental mammals",
"somatic mammals",
"respiratory mammals"
] | B | Human beings are mammals. Like other mammals, we have hair and mammary glands. The subclass in which the human species is classified is the placental mammals. | train | sciq | null |
The shape of the path of an object undergoing projectile motion in two dimensions is a what? | [
"circle",
"radius",
"parabola",
"orbit"
] | C | The shape of the path of an object undergoing projectile motion in two dimensions is a parabola. | train | sciq | null |
The earliest cells were called what? | [
"prokaryotes",
"carbohydrates",
"microcytes",
"eukaryotes"
] | A | The first organisms were made of only one cell ( Figure below ). The earliest cells were prokaryotes . Prokaryotic cells are surrounded by a cell membrane, but they do not have a nucleus. The cells got their nutrients directly from the water. The cells needed to use these nutrients to live and grow. | train | sciq | null |
Protists are the simplest of what? | [
"fungi",
"plants",
"eukaryotes",
"prokaryotes"
] | C | Protists are the simplest eukaryotes. They are easiest to define by what they are not. Protists are not animals, plants, or fungi. | train | sciq | null |
The measure of magnetic fields is named after a serbian physicist. what is his name? | [
"nikola tesla",
"Carl Sagan",
"Albert Einstein",
"Niels Bohr"
] | A | For static electric charges, the electromagnetic force is manifested by the Coulomb electric force alone. If charges are moving, an additional force emerges, called magnetism. The century realization that electricity and magnetism are dual aspects of the same force completely changed our understanding of the world we l... | train | sciq | null |
Radon (rn) is a radioactive gas formed by the decay of naturally occurring uranium in rocks such as granite. it tends to collect in the basements of houses and poses a significant health risk if present in indoor air. many states now require that houses be tested for radon before they are what? | [
"seen",
"built",
"modified",
"sold"
] | D | M = dRTP Exercise Radon (Rn) is a radioactive gas formed by the decay of naturally occurring uranium in rocks such as granite. It tends to collect in the basements of houses and poses a significant health risk if present in indoor air. Many states now require that houses be tested for radon before they are sold. Calcul... | train | sciq | null |
What state of matter takes neither the shape nor the volume of its container? | [
"solid",
"liquid",
"hot",
"gas"
] | A | All three containers contain a substance with the same mass, but the substances are in different states. In the left-hand container, the substance is a gas, which has spread to fill its container. It takes both the shape and volume of the container. In the middle container, the substance is a liquid, which has spread t... | train | sciq | null |
Force times distance is the equation for what? | [
"work",
"power",
"speed",
"gravity"
] | A | Work is directly related to both the force applied to an object and the distance the object moves. It can be represented by the equation: Work = Force × Distance. | train | sciq | null |
What is the name for a series of changes in the reproductive system of mature females that repeats every month on average? | [
"puberty",
"periodic table",
"menstrual cycle",
"urinary cycle"
] | C | Egg production in the ovary is part of the menstrual cycle. The menstrual cycle is a series of changes in the reproductive system of mature females that repeats every month on average. These changes include the development of an egg and follicle in the ovary. | train | sciq | null |
What is the name of the iron-containing oxygen-transport protein in the red blood cells of all vertebrates? | [
"hemoglobin",
"ferric acid",
"platelet",
"plasma"
] | A | Hemoglobin is the iron-containing oxygen-transport protein in the red blood cells of all vertebrates. The hemoglobin molecule is an assembly of four globular protein subunits, each tightly associated with a non-protein heme group. The heme group binds to the iron ion. The most common hemoglobin is hemoglobin A, a tetra... | train | sciq | null |
What is the active ingredient in household bleach? | [
"chlorine",
"oxygen",
"magnesium",
"iodine"
] | A | Chlorine is the active ingredient in household bleach. It removes stains from clothes. It can also be used to disinfect countertops and other surfaces. | train | sciq | null |
What are the membrane-bound organelles that are usually larger than vesicles and can have secretory, excretory, and storage functions? | [
"vacuoles",
"ribosomes",
"nucleolus",
"tubules"
] | A | Vacuoles are membrane-bound organelles that can have secretory, excretory, and storage functions. They are usually larger than vesicles. | train | sciq | null |
What broad category of animals is primarily ectothermic and covered with scales that facilitate swimming? | [
"deer",
"armadillo",
"turtles",
"fish"
] | D | Fish show great diversity in body size. They range in length from about 8 millimeters (0.3 inches) to 16 meters (about 53 feet). Most are ectothermic and covered with scales. Scales protect fish from predators and parasites and reduce friction with the water. Multiple, overlapping scales provide a flexible covering tha... | train | sciq | null |
What has two chains of nucleotides, one more than rna? | [
"mna",
"dna",
"fna",
"gna"
] | B | RNA consists of just one chain of nucleotides. DNA consists of two chains. Nitrogen bases on the two chains of DNA form hydrogen bonds with each other. Hydrogen bonds are relatively weak bonds that form between a positively charged hydrogen atom in one molecule and a negatively charged atom in another molecule. Hydroge... | train | sciq | null |
The axon terminates on muscle fibers at the neuromuscular junction. acetylcholine is released at this specialized synapse, which causes the muscle action potential to begin, following a large potential known as an end plate potential. when the lower motor neuron excites the muscle fiber, it contracts. all of this occur... | [
"muscular system",
"respiratory system",
"cardiovascular system",
"nervous system"
] | D | described in the chapter on muscle tissue, an action potential travels along the motor neuron axon into the periphery. The axon terminates on muscle fibers at the neuromuscular junction. Acetylcholine is released at this specialized synapse, which causes the muscle action potential to begin, following a large potential... | train | sciq | null |
Misconceptions about what theory contribute to the controversy that still surrounds this fundamental principle of biology? | [
"darwin on evolution",
"cycle of evolution",
"theory of evolution",
"brain of evolution"
] | C | Today, evolution is still questioned by some people. Often, people who disagree with the theory of evolution do not really understand it. For example, some people think that the theory of evolution explains how life on Earth first began. In fact, the theory explains only how life changed after it first appeared. Some p... | train | sciq | null |
What device is used to stop a current in a circuit? | [
"a signal",
"a valve",
"a switch",
"a mirror"
] | C | Understand current as it passes through a series circuit. | train | sciq | null |
What oily substance prevents the hair and skin of living things from drying out? | [
"pancreatic enzymes",
"sebum",
"progesterone",
"pus"
] | B | Sebaceous glands are commonly called oil glands. They produce an oily substance called sebum. Sebum is secreted into hair follicles. Then it makes its way along the hair shaft to the surface of the skin. Sebum waterproofs the hair and skin and helps prevent them from drying out. | train | sciq | null |
What two types of communication do both humans and birds use primarily? | [
"sensual and auditory",
"material and auditory",
"interaction and auditory",
"visual and auditory"
] | D | train | sciq | null | |
Eggs are produced in what organs and, upon fertilization, develop in what other organ? | [
"uterus, vagina",
"ovaries, uterus",
"cervix, ovaries",
"fallopian tubes, ovaries"
] | B | train | sciq | null | |
The first line of defense includes mechanical, chemical, and which other barrier? | [
"biological",
"physical",
"surgical",
"independent"
] | A | The first line of defense includes mechanical, chemical, and biological barriers. | train | sciq | null |
What is another term for nearsightedness? | [
"anemia",
"astigmatism",
"myopia",
"hypoxia"
] | C | Nearsightedness, or myopia, is the condition in which nearby objects are seen clearly, but distant objects appear blurry. The Figure below shows how it occurs. The eyeball is longer (from front to back) than normal. This causes images to be focused in front of the retina instead of on the retina. Myopia can be correcte... | train | sciq | null |
Because all animals require an external source of what, they are called heterotrophic? | [
"food",
"energy",
"water",
"fuel"
] | A | 27.1 | Features of the Animal Kingdom By the end of this section, you will be able to: • List the features that distinguish the kingdom Animalia from other kingdoms • Explain the processes of animal reproduction and embryonic development • Describe the roles that Hox genes play in development Even though members of the... | train | sciq | null |
What causes blue litmus to turn red? | [
"carbon",
"oxygen",
"acid",
"base"
] | C | Acids change the color of certain acid-base indicators. Two common indicators are litmus and phenolphthalein. Blue litmus turns red in the presence of an acid, while phenolphthalein turns colorless. | train | sciq | null |
When fossil fuel is burned the chemical energy is converted into what? | [
"natural energy",
"kinetic energy",
"thermal energy",
"atmospheric energy"
] | C | Watching movies, eating hot popcorn, and many other activities depend on electrical energy. Most electrical energy comes from the burning of fossil fuels, which contain stored chemical energy. When fossil fuels are burned, the chemical energy changes to thermal energy and the thermal energy is then used to generate ele... | train | sciq | null |
What two activities are especially important when a number of local populations are linked, forming a metapopulation? | [
"flow and emigration",
"immigration and emigration",
"family reunions and emigration",
"immigration and family reunions"
] | B | train | sciq | null | |
What is the physical environment in which a species lives and to which it has adapted? | [
"ecosystem",
"farmland",
"habitat",
"land mass"
] | C | Another important aspect of a species’ niche is its habitat. Habitat is the physical environment in which a species lives and to which it has adapted. Features of a habitat depend mainly on abiotic factors, such as temperature and rainfall. These factors influence the traits of the organisms that live there. | train | sciq | null |
What kind of tests may detect substances associated with particular disorders? | [
"electrical",
"hormonal",
"genetic",
"biochemical"
] | D | train | sciq | null | |
Scientists think the solar system formed from a big cloud of gas and dust called what? | [
"comet",
"Oort cloud",
"supernova",
"nebula"
] | D | Scientists think the solar system formed from a big cloud of gas and dust, called a nebula . This is the solar nebula hypothesis. The nebula was made mostly of hydrogen and helium. There were heavier elements too. Gravity caused the nebula to contract ( Figure below ). | train | sciq | null |
What are the largest phylum of the animal kingdom? | [
"arthropods",
"Pycnogonida",
"Crustacea",
"Chelicerata"
] | A | Two chemical species combine to produce a new compound. The general expression for this reaction is A + B → C. | train | sciq | null |
What is the name for a material that prevents the transfer of heat energy? | [
"physical insulator",
"thermal condenser",
"structure insulator",
"thermal insulator"
] | D | Another example of a thermal insulator is pictured in the Figure below . The picture shows fluffy pink insulation inside the attic of a home. Like the down filling in a snowsuit, the insulation traps a lot of air. The insulation helps to prevent the transfer of thermal energy into the house on hot days and out of the h... | train | sciq | null |
What is a rock exposed to if it's undergoing metamorphism? | [
"time and energy",
"gravity and precipitation",
"heat and pressure",
"humidity and pressure"
] | C | Metamorphism. This long word means “to change form. “ A rock undergoes metamorphism if it is exposed to extreme heat and pressure within the crust. With metamorphism, the rock does not melt all the way. The rock changes due to heat and pressure. A metamorphic rock may have a new mineral composition and/or texture. | train | sciq | null |
Water infiltrates the ground because soil and rock may have air spaces between the grains. these pores, or tiny holes, result in the rock's what? | [
"energy",
"porosity",
"sheen",
"shine"
] | B | Identify features caused by groundwater erosion and deposition. | train | sciq | null |
Work is done only if a force is exerted in the direction of what? | [
"wind",
"motion",
"north",
"gravity"
] | B | Work is done only if a force is exerted in the direction of motion. If the motion is perpendicular to the force, no work has been done. If the force is at an angle to the motion, then the component of the force in the direction of the motion is used to determine the work done. | train | sciq | null |
What is the smallest independently functioning unit of a living organism? | [
"proteins",
"atom",
"molecule",
"cell"
] | D | A cell is the smallest independently functioning unit of a living organism. Even bacteria, which are extremely small, independently-living organisms, have a cellular structure. Each bacterium is a single cell. All living structures of human anatomy contain cells, and almost all functions of human physiology are perform... | train | sciq | null |
All animals have specialized types of what basic structures, which can then do different jobs? | [
"atoms",
"cells",
"muscles",
"proteins"
] | B | Animals are multicellular eukaryotes in the Animal Kingdom. All animals are heterotrophs. They eat other living things because they can’t make their own food. All animals also have specialized cells that can do different jobs. Most animals have higher levels of organization as well. They may have specialized tissues, o... | train | sciq | null |
What term describes the number of items in a given area or volume? | [
"density",
"fraction",
"alkalinity",
"concentration"
] | D | In its most general form, concentration describes the number of items in a given area or volume. The units generally depend on the types of items being counted. For example, if we were to calculate the concentration of people that live in a city, we would divide the total number of people by the area. If we measured th... | train | sciq | null |
Birds are known for flying south in the winter to avoid what? | [
"solar radiation",
"hurricanes",
"rain",
"cold weather"
] | D | train | sciq | null | |
The root system is usually anchored by one main root developed from what? | [
"embryonic radicle",
"organisms radicle",
"nuclei radicle",
"sperm radicle"
] | A | Eudicots Eudicots, or true dicots, are characterized by the presence of two cotyledons. Veins form a network in leaves. Flower parts come in four, five, or many whorls. Vascular tissue forms a ring in the stem. (In monocots, vascular tissue is scattered in the stem. ) Eudicots can be herbaceous (like dandelions or viol... | train | sciq | null |
What type of learning is done from past experiences and reasoning? | [
"transformation learning",
"consequence learning",
"rational learning",
"insight learning"
] | D | Insight learning is learning from past experiences and reasoning. It usually involves coming up with new ways to solve problems. Insight learning generally happens quickly. An animal has a sudden flash of insight. Insight learning requires relatively great intelligence. Human beings use insight learning more than any o... | train | sciq | null |
Where is the pituitary gland? | [
"heart",
"lung",
"thyroid",
"brain"
] | D | The regulation of Leydig cell production of testosterone begins outside of the testes. The hypothalamus and the pituitary gland in the brain integrate external and internal signals to control testosterone synthesis and secretion. The regulation begins in the hypothalamus. Pulsatile release of a hormone called gonadotro... | train | sciq | null |
Which fungi eaten by people all over the world? | [
"mushrooms",
"fruits",
"legumes",
"algae"
] | A | Mushrooms are fungi that are eaten by people all over the globe. | train | sciq | null |
The outermost layer of the leaf is the epidermis; it is present on both sides of the leaf and is called the upper and lower epidermis, respectively. botanists call the upper side the adaxial surface (or adaxis) and the lower side this? | [
"posterior surface",
"abaxial surface (or abaxis)",
"anterior surface",
"dorsal surface"
] | B | Leaf Structure and Function The outermost layer of the leaf is the epidermis; it is present on both sides of the leaf and is called the upper and lower epidermis, respectively. Botanists call the upper side the adaxial surface (or adaxis) and the lower side the abaxial surface (or abaxis). The epidermis helps in the re... | train | sciq | null |
A small quake preceding a large quake is called what? | [
"preshock",
"aftershock",
"foreshock",
"warning shock"
] | C | There are sometimes signs that a large earthquake is coming. There may be small quakes, called foreshocks . These can occur a few seconds to a few weeks before a major quake. Unfortunately, foreshocks are not very useful for predicting large earthquakes. Many quakes do not have foreshocks. Also, small earthquakes are n... | train | sciq | null |
What do winter storms develop from at higher latitudes? | [
"cyclones",
"temperatures",
"clouds",
"humidity"
] | A | Winter storms develop from cyclones at higher latitudes. They include blizzards and lake-effect snow storms. | train | sciq | null |
What is the only substance on earth that is present in all three states of matter? | [
"mercury",
"water",
"carbon",
"air"
] | B | Water is the only substance on Earth that is present in all three states of matter. This means that water is present as a solid, liquid, and gas. Earth is the only planet where water is present in all three states. All three phases may be present in a single location or in a region. The three phases are solid (ice or s... | train | sciq | null |
What is essential for forming new genes? | [
"large mutations",
"enough mutations",
"enough chromosomes",
"chromosome deversity"
] | A | It is believed that large mutations form new genes. Mutations that duplicate large sections of DNA are a major source of genetic material for new genes. It is thought that tens to hundreds of genes are duplicated in animal genomes every million years. Most genes belong to larger families of genes of shared ancestry. Th... | train | sciq | null |
What is fluid friction with air called? | [
"wind resistance",
"air resistance",
"buoyancy",
"gravity"
] | B | Types of friction include static friction, sliding friction, rolling friction, and fluid friction. Fluid friction with air is called air resistance. | train | sciq | null |
Plants produce their own sugars and other food molecules through what process? | [
"spermatogenesis",
"hydrogenesis",
"glycolysis",
"photosynthesis"
] | D | train | sciq | null | |
What do fission reactors use to slow down the neutrons? | [
"brake",
"moderator",
"inertia",
"control"
] | B | U-235 nuclei can capture neutrons and disintegrate more efficiently if the neutrons are moving slower than the speed at which they are released. Fission reactors use a moderator surrounding the fuel rods to slow down the neutrons. Water is not only a good coolant but also a good moderator, so a common type of fission r... | train | sciq | null |
What term is used to describe an unusual sound coming from the heart that is caused by the turbulent flow of blood? | [
"music",
"garble",
"whisper",
"murmur"
] | D | The term murmur is used to describe an unusual sound coming from the heart that is caused by the turbulent flow of blood. Murmurs are graded on a scale of 1 to 6, with 1 being the most common, the most difficult sound to detect, and the least serious. The most severe is a 6. Phonocardiograms or auscultograms can be use... | train | sciq | null |
Carbon atoms are bonded to as many hydrogen atoms as possible in what type of fatty acids? | [
"oily",
"saturated",
"unsaturated",
"super"
] | B | Saturated fatty acids have only single bonds between carbon atoms. As a result, the carbon atoms are bonded to as many hydrogen atoms as possible. In other words, the carbon atoms are saturated with hydrogens. Saturated fatty acids are found in fats. | train | sciq | null |
What kind of mouthparts do aphids have? | [
"siphoning mouthparts",
"chewing mouthparts",
"sponging mouthparts",
"piercing-sucking mouthparts"
] | D | Some insects, such as aphids, have piercing-sucking mouthparts. Other insects, like grasshoppers, have chewing mouthparts. | train | sciq | null |
Sounds, chemicals, and visual cues are examples of what between animals? | [
"circulation",
"communication",
"migration",
"procreation"
] | B | For individuals to cooperate, they need to communicate . Animals can communicate with sounds, chemicals, or visual cues. For example, to communicate with sounds, birds sing and frogs croak. Both may be communicating that they are good mates. Ants communicate with chemicals called pheromones . For example, they use the ... | train | sciq | null |
What is pressure times area equal to? | [
"mass",
"force",
"volume",
"density"
] | B | There is a pressure difference when the channel narrows. This pressure difference results in a net force on the fluid: recall that pressure times area equals force. The net work done increases the fluid’s kinetic energy. As a result, the pressure will drop in a rapidly-moving fluid, whether or not the fluid is confined... | train | sciq | null |
What part of the kangaroo helps it balance when it leaps as well as when it sits? | [
"the spine",
"large feet",
"the tail",
"the pouch"
] | C | train | sciq | null | |
What is the evolutionary history of a group of related organisms called? | [
"superfamily",
"ancestry",
"phylogeny",
"lineage"
] | C | Linnaeus classified organisms based on obvious physical traits. Basically, organisms were grouped together if they looked alike. After Darwin published his theory of evolution in the 1800s, scientists looked for a way to classify organisms that showed phylogeny. Phylogeny is the evolutionary history of a group of relat... | train | sciq | null |
What are specialized cells in the brain that monitor the concentration of solutes in the blood called? | [
"ionconcentrate",
"osmoreceptors",
"sporozoans",
"staurikosaurus"
] | B | Many marine invertebrates have internal salt levels matched to their environments, making them isotonic with the water in which they live. Fish, however, must spend approximately five percent of their metabolic energy maintaining osmotic homeostasis. Freshwater fish live in an environment that is hypotonic to their cel... | train | sciq | null |
Bones consist of four types of tissue, compact bone, spongy bone, bone marrow, and what? | [
"epithelium",
"periosteum",
"plasma",
"collagen"
] | B | Bones consist of four different types of tissue: periosteum, compact bone, spongy bone, and bone marrow. Ossification gradually changes the cartilage skeleton of the fetus to the bony skeleton of the adult. | train | sciq | null |
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