questions stringlengths 37 1.22k | reasoning stringlengths 0 3.56k ⌀ | answers stringlengths 4 138 |
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There are six fundamentally different kinds of nuclear decay reactions, and each releases a different kind of particle or what?
Here are the choices:
A. mineral
B. protein
C. energy
D. mass | an identical particle that has been ejected from a heavier nucleus. There are six fundamentally different kinds of nuclear decay reactions, and each releases a different kind of particle or energy. The essential features of each reaction are shown in Figure 20.4 "Common Modes of Nuclear Decay". The most common are alphaand beta decay and gamma emission, but the others are essential to an understanding of nuclear decay reactions. Figure 20.4 Common Modes of Nuclear Decay. | C: energy. |
What is the only metal that is a liquid at room temperature?
Here are the choices:
A. copper
B. aluminum
C. mercury
D. tin | The elements mercury, gold, and copper display properties that are common of metals. Mercury ( left ) is the only metal that is a liquid at room temperature. Even in its liquid form, it still has a high luster. Gold ( middle ) is malleable and can be formed into very thin sheets called gold leaf. Because copper ( right ) is ductile, inexpensive, and a good conductor, it is used extensively in electrical wiring. | C: mercury. |
Heart valves prevent what kind of blood flow from happening in the heart?
Here are the choices:
A. backflow
B. irregular flow
C. slow flow
D. quick flow | A: backflow. | |
What is the source of energy for photosynthesis?
Here are the choices:
A. air
B. light
C. carbon
D. gravity | The energy for photosynthesis comes from light. Without light energy, photosynthesis cannot occur. As you can see in the Figure below , plants can get the energy they need for photosynthesis from either sunlight or artificial light. | B: light. |
Different types of interference include destructive and what else?
Here are the choices:
A. helpful
B. consistent
C. active
D. constructive | 2t = λ n / 2, 3λ n / 2, 5λ n / 2, … . To know whether interference is constructive or destructive, you must also determine if there is a phase change upon reflection. Thin film interference thus depends on film thickness, the wavelength of light, and the refractive indices. For white light incident on a film that varies in thickness, you will observe rainbow colors of constructive interference for various wavelengths as the thickness varies. Example 27.7 Soap Bubbles: More Than One Thickness can be Constructive (a) What are the three smallest thicknesses of a soap bubble that produce constructive interference for red light with a wavelength of 650 nm? The index of refraction of soap is taken to be the same as that of water. (b) What three smallest thicknesses will give destructive interference? Strategy and Concept Use Figure 27.33 to visualize the bubble. Note that water). There is a. | D: constructive. |
What is anything that causes cancer called?
Here are the choices:
A. bacteria
B. carcinogen
C. pesticide
D. chemical | A carcinogen is anything that causes cancer. Most carcinogens produce mutations in genes that control the cell cycle. | B: carcinogen. |
In comparing two solutions of unequal solute concentration, the solution with the higher solute concentration is called what?
Here are the choices:
A. hydrophilic
B. hypertonic
C. hypothermic
D. acetic | Imagine now that you have a second cup with 100ml of water, and you add 45 grams of table sugar to the water. Just like the first cup, the sugar is the solute, and the water is the solvent. But now you have two mixtures of different solute concentrations. In comparing two solutions of unequal solute concentration, the solution with the higher solute concentration is hypertonic , and the solution with the lower solute concentration is hypotonic . Solutions of equal solute concentration are isotonic . The first sugar solution is hypotonic to the second solution. The second sugar solution is hypertonic to the first. | B: hypertonic. |
What broad group of animals - which includes rats, dogs and camels - have highly developed brains and often perform work for humans?
Here are the choices:
A. reptiles
B. arachnids
C. mammals
D. amphibians | We see examples of mammals (other than people!) serving our needs everywhere. We have pets that are mammals, such as dogs and cats. Mammals are also used around the world for transport. For example, horses, donkeys, mules, or camels ( Figure below ) may be the primary means of transport in some parts of the world. Mammals also do work for us. Service dogs can be trained to help the disabled. These include guide dogs, which are assistance dogs trained to lead blind and visually impaired people around obstacles. Horses and elephants can carry heavy loads. Humans also use some mammals for food. For example, cows and goats are commonly raised for their milk and meat. Mammals’ more highly developed brains have made them ideal for use by scientists in studying such things as learning, as seen in maze studies of mice and rats. | C: mammals. |
What term describes a way that small molecules or ions move across the cell membrane without input of energy by the cell?
Here are the choices:
A. passive transport
B. immune transport
C. physical transport
D. impassive transport | Passive transport is a way that small molecules or ions move across the cell membrane without input of energy by the cell. The three main kinds of passive transport are diffusion (or simple diffusion), osmosis, and facilitated diffusion. Simple diffusion and osmosis do not involve transport proteins. Facilitated diffusion requires the assistance of proteins. | A: passive transport. |
Do most humans feed at one trophic level, or more than one?
Here are the choices:
A. less than one
B. more than one
C. one
D. none | Many consumers feed at more than one trophic level. Humans, for example, are primary consumers when they eat plants such as vegetables. They are secondary consumers when they eat cows. They are tertiary consumers when they eat salmon. | B: more than one. |
What is it called when two waves combine to create a larger wave?
Here are the choices:
A. constructive interference
B. wave propagation
C. Destructive Interference
D. consistent interference | Constructive interference occurs when two waves combine to create a larger wave. This occurs when the peaks of two waves line up. | A: constructive interference. |
What is the study of the relationship between electricity and chemical reactions called?
Here are the choices:
A. inorganic chemistry
B. analytical chemistry
C. electrochemistry
D. physical chemistry | Summary Electrochemistry is the study of the relationship between electricity and chemical reactions. The oxidation–reduction reaction that occurs during an electrochemical process consists of two halfreactions, one representing the oxidation process and one the reduction process. The sum of the halfreactions gives the overall chemical reaction. The overall redox reaction is balanced when the number of electrons lost by the reductant equals the number of electrons gained by the oxidant. An electric current is produced from the flow of electrons from the reductant to the oxidant. An electrochemical cell can either generate electricity from a spontaneous redox reaction or consume electricity to drive a nonspontaneous reaction. In a galvanic (voltaic) cell, the energy from a spontaneous reaction generates electricity, whereas in an electrolytic cell, electrical energy is consumed to drive a nonspontaneous redox reaction. Both types of cells use two electrodes that provide an electrical connection between systems that are separated in space. The oxidative half-reaction occurs at the anode, and the reductive half-reaction occurs at the cathode. A salt bridge connects the separated solutions, allowing ions to migrate to either solution to ensure the system’s electrical neutrality. A voltmeter is a device that measures the flow of electric current between two half-reactions. The potential of a cell, measured in volts, is the energy needed to move a charged particle in an electric field. An electrochemical cell can be described using line notation called a cell diagram, in which vertical lines indicate phase boundaries and the location of the salt bridge. Resistance to the flow of charge at a boundary is called the junction potential. | C: electrochemistry. |
What is the term for expelling air out of the body through the nose or mouth?
Here are the choices:
A. induction
B. inhalation
C. perspiration
D. exhalation | Most of the time, you breathe without thinking about it. Breathing is mostly an involuntary action that is controlled by a part of your brain that also controls your heart beat. If you swim, do yoga, or sing, you know you can control your breathing, however. Taking air into the body through the nose and mouth is called inhalation . Pushing air out of the body through the nose or mouth is called exhalation . The woman pictured below is exhaling before she surfaces from the pool water ( Figure below ). | D: exhalation. |
The lowest resonant frequency is called the what?
Here are the choices:
A. lowest
B. fundamental
C. simplest
D. basic | Given that maximum air displacements are possible at the open end and none at the closed end, there are other, shorter wavelengths that can resonate in the tube, such as the one shown in Figure 17.28. Here the standing wave has three-fourths of its wavelength in the tube, or L = (3 / 4)λ′ , so that λ′ = 4L / 3 . Continuing this process reveals a whole series of shorterwavelength and higher-frequency sounds that resonate in the tube. We use specific terms for the resonances in any system. The lowest resonant frequency is called the fundamental, while all higher resonant frequencies are called overtones. All resonant frequencies are integral multiples of the fundamental, and they are collectively called harmonics. The fundamental is the first harmonic, the first overtone is the second harmonic, and so on. Figure 17.29 shows the fundamental and the first three overtones (the first four harmonics) in a tube closed at one end. | B: fundamental. |
Body waves and surface waves are the two major types of what, which occur during earthquakes?
Here are the choices:
A. sound waves
B. seismic waves
C. tidal waves
D. current waves | There are two major types of seismic waves. Body waves travel through the Earth’s interior. Surface waves travel along the ground surface. In an earthquake, body waves are responsible for sharp jolts. Surface waves are responsible for rolling motions that do most of the damage in an earthquake. | B: seismic waves. |
Inferior rotation occurs during limb adduction and involves the downward motion of what?
Here are the choices:
A. choroidal cavity
B. dialysate cavity
C. pelvic cavity
D. glenoid cavity | Superior Rotation and Inferior Rotation Superior and inferior rotation are movements of the scapula and are defined by the direction of movement of the glenoid cavity. These motions involve rotation of the scapula around a point inferior to the scapular spine and are produced by combinations of muscles acting on the scapula. During superior rotation, the glenoid cavity moves upward as the medial end of the scapular spine moves downward. This is a very important motion that contributes to upper limb abduction. Without superior rotation of the scapula, the greater tubercle of the humerus would hit the acromion of the scapula, thus preventing any abduction of the arm above shoulder height. Superior rotation of the scapula is thus required for full abduction of the upper limb. Superior rotation is also used without arm abduction when carrying a heavy load with your hand or on your shoulder. You can feel this rotation when you pick up a load, such as a heavy book bag and carry it on only one shoulder. To increase its weight-bearing support for the bag, the shoulder lifts as the scapula superiorly rotates. Inferior rotation occurs during limb adduction and involves the downward motion of the glenoid cavity with upward movement of the medial end of the scapular spine. | D: glenoid cavity. |
The speed of an electromagnetic wave is the product of its wavelength and what else?
Here are the choices:
A. height
B. resonance
C. density
D. frequency | Electromagnetic waves differ in their wavelengths and frequencies. The higher the frequency of an electromagnetic wave, the greater its energy. The speed of an electromagnetic wave is the product of its wavelength and frequency, so a wave with a shorter wavelength has a higher frequency, and vice versa. | D: frequency. |
Electrons in inner shells are called what?
Here are the choices:
A. inner electrons
B. valence electrons
C. core electrons
D. surface electrons | because of interactions between the electrons of the outermost shell of different atoms, called the valence shell electrons. Electrons in inner shells are called core electrons. Elements are grouped together by similar chemical properties into a chart called the periodic table. Vertical columns of elements are called groups or families. Some of the groups of elements have names, like the alkali metals, the alkaline earth metals, the halogens, and the noble gases. A horizontal row of elements is called a period. Periods and groups have differing numbers of elements in them. The periodic table separates elements into metals, nonmetals, andsemimetals. The periodic table is also separated into main group elements,transition metals, lanthanide elements, and actinide elements. The lanthanide and actinide elements are also referred to as inner transition metal elements. The shape of the periodic table reflects the sequential filling of shells and subshells in atoms. The periodic table helps us understand trends in some of the properties of atoms. One such property is the atomic radius of atoms. From top to bottom of the periodic table, atoms get bigger because electrons are occupying larger and bigger shells. From left to right across the periodic table, electrons are filling the same shell but are being attracted by an increasing positive charge from the nucleus, and thus the atoms get smaller. | C: core electrons. |
The binding of complementary bases allows dna molecules to take their well-known shape, called a what?
Here are the choices:
A. double helix
B. single helix
C. triple helix
D. simple helix | The binding of complementary bases allows DNA molecules to take their well-known shape, called a double helix . Figure below shows how two chains of nucleotides form a DNA double helix. A simplified double helix is illustrated in Figure below . It shows more clearly how the two chains are intertwined. The double helix shape forms naturally and is very strong. Being intertwined, the two chains are difficult to break apart. This is important given the fundamental role of DNA in all living organisms. | A: double helix. |
What are the only amphibians without legs?
Here are the choices:
A. newts
B. porifera
C. crustaceans
D. caecilians | Caecilians The caecilian order is the amphibian order with the fewest species. Caecilians are closely related to salamanders. They have a long, worm-like body. They are the only amphibians without legs. Caecilians evolved from a four-legged ancestor but lost their legs later in their evolution. As adults, they often burrow into the soil. That’s one reason why Caecilians tend to be less well known than other amphibians. microcaecilia. | D: caecilians. |
Plants, fungi, bacteria and archaea cells all have what feature that keeps them rigid that animal cells do not have?
Here are the choices:
A. cell membrane
B. plastids
C. cell walls
D. cytoplasm | about how that occurs, in terms of membrane structure. If the influx of water continued unopposed, the membrane would eventually burst like an over-inflated balloon, killing the cell. One strategy to avoid this lethal outcome, adopted by a range of organisms, is to build a semi-rigid “cell wall” exterior to the plasma membrane (→). The synthesis of this cell wall is based on the controlled assembly of macromolecules secreted by the cell through the process of exocytosis (see above). As water passes through the plasma membrane and into the cell (driven by osmosis), the plasma membrane is pressed up against the cell wall. The force exerted by the rigid cell wall on the membrane balances the force of water entering the cell. When the two forces are equal, the net influx of water into the cell stops. Conversely, if the [H2O]outside decreases, this pressure is reduced, the membrane moves away from the cell wall and, because they are only semi-rigid, the walls flex. It is this behavior that causes plants to wilt when they do not get enough water. These are passive behaviors, based on the structure of the cell wall; they are built into the wall as it is assembled. Once the cell wall has been built, a cell with a cell wall does not need to expend energy to resist osmotic effects. Plants, fungi, bacteria and archaea all have cell walls. A number of antibiotics work by disrupting the assembly of bacterial cell walls. This leaves the bacteria osmotically sensitive, water enters these cells until they burst and die. Questions to answer & to ponder: • Make a graph of the water concentration across a typical cellular membrane for an organism living in fresh water; explain what factors influenced your drawing. • Look at this video: https://www. youtube. com/watch?v=VctALENHyyI&feature=youtu. How could you use reverse osmosis to purify water? • Where does the energy involved in moving molecules come from? • Plants and animals are both eukaryotes; how would you decide whether the common ancestor of the eukaryotes had a cell wall. • Why does an aquaporin channel not allow a Na+ ion to pass through it? • If there is no net flux of A, even if there is a concentration gradient between two points, what can we conclude?. | C: cell walls. |
What type of interspecies relationship involves one party being actively harmed?
Here are the choices:
A. mutualism
B. symbiosis
C. mosaicism
D. parasitism | Symbiosis is a close relationship between two species in which at least one species benefits. Mutualism is a symbiotic relationship in which both species benefit. Commensalism is a symbiotic relationship in which one species benefits while the other species is not affected. Parasitism is a symbiotic relationship in which one species (the parasite) benefits while the other species (the host) is harmed. | D: parasitism. |
Which nervous system consists of all the nervous tissue that lies outside the central nervous system?
Here are the choices:
A. significant nervous system
B. function nervous system
C. auxiliary nervous system
D. peripheral nervous system | The peripheral nervous system (PNS) consists of all the nervous tissue that lies outside the central nervous system. It is shown in yellow in Figure below . It is connected to the central nervous system by nerves. A nerve is a cable-like bundle of axons. Some nerves are very long. The longest human nerve is the sciatic nerve. It runs from the spinal cord in the lower back down the left leg all the way to the toes of the left foot. Like the nervous system as a whole, the peripheral nervous system also has two divisions: the sensory division and the motor division. | D: peripheral nervous system. |
What do organisms use to grow and repair themselves?
Here are the choices:
A. mutation
B. diffusion
C. cell solution
D. cell division | Cell division is how organisms grow and repair themselves. It is also how they produce offspring. Many single-celled organisms reproduce by binary fission. The parent cell simply divides to form two daughter cells that are identical to the parent. In many other organisms, two parents are involved, and the offspring are not identical to the parents. In fact, each offspring is unique. Look at the family in Figure below . The children resemble their parents, but they are not identical to them. Instead, each has a unique combination of characteristics inherited from both parents. In this lesson, you will learn how this happens. | D: cell division. |
The afferent arterioles service about 1.3 million of what in each kidney?
Here are the choices:
A. axons
B. nephrons
C. dendrites
D. neurons | Nephrons and Vessels The renal artery first divides into segmental arteries, followed by further branching to form interlobar arteries that pass through the renal columns to reach the cortex (Figure 25.9). The interlobar arteries, in turn, branch into arcuate arteries, cortical radiate arteries, and then into afferent arterioles. The afferent arterioles service about 1.3 million nephrons in each kidney. | B: nephrons. |
Kyphosis, lordosis, and scoliosis are all diseases involving improper curvature of which bodily structure (which is supposed to be curved in a certain way anyway)?
Here are the choices:
A. aorta
B. femur
C. lungs
D. spine | During fetal development, the body is flexed anteriorly into the fetal position, giving the entire vertebral column a single curvature that is concave anteriorly. In the adult, this fetal curvature is retained in two regions of the vertebral column as the thoracic curve, which involves the thoracic vertebrae, and the sacrococcygeal curve, formed by the sacrum and coccyx. Each of these is thus called a primary curve because they are retained from the original fetal curvature of the vertebral column. A secondary curve develops gradually after birth as the child learns to sit upright, stand, and walk. Secondary curves are concave posteriorly, opposite in direction to the original fetal curvature. The cervical curve of the neck region develops as the infant begins to hold their head upright when sitting. Later, as the child begins to stand and then to walk, the lumbar curve of the lower back develops. In adults, the lumbar curve is generally deeper in females. Disorders associated with the curvature of the spine include kyphosis (an excessive posterior curvature of the thoracic region), lordosis (an excessive anterior curvature of the lumbar region), and scoliosis (an abnormal, lateral curvature, accompanied by twisting of the vertebral column). | D: spine. |
What do herbivores eat?
Here are the choices:
A. meat and plants
B. animals
C. minerals
D. plants | Herbivores eat plants, carnivores eat meat, and omnivores eat both. | D: plants. |
What important aspect of the scientific method is a suggested explanation for an event, which can be tested?
Here are the choices:
A. hypothesis
B. string theory
C. independent variable
D. scientific control | The Process of Science Biology is a science, but what exactly is science? What does the study of biology share with other scientific disciplines? Science (from the Latin scientia, meaning “knowledge”) can be defined as knowledge that covers general truths or the operation of general laws, especially when acquired and tested by the scientific method. It becomes clear from this definition that the application of the scientific method plays a major role in science. The scientific method is a method of research with defined steps that include experiments and careful observation. The steps of the scientific method will be examined in detail later, but one of the most important aspects of this method is the testing of hypotheses by means of repeatable experiments. A hypothesis is a suggested explanation for an event, which can be tested. Although using the scientific method is inherent to science, it is inadequate in determining what science is. This is because it is relatively easy to apply the scientific method to disciplines such as physics and chemistry, but when it. | A: hypothesis. |
What distant and extraordinarily energetic objects now seem to be early stages of galactic evolution with a supermassive black-hole-devouring material?
Here are the choices:
A. pulsars
B. quasars
C. stars
D. neutrinos | the history of galactic evolution has been, and the nature of space in their vicinity. However, so many black holes are now known that correlations between black hole mass and galactic nuclei characteristics are being studied. What is the mechanism for the energy output of quasars? These distant and extraordinarily energetic objects now seem to be early stages of galactic evolution with a supermassive black-hole-devouring material. Connections are now being made with galaxies having energetic cores, and there is evidence consistent with less consuming, supermassive black holes at the center of older galaxies. New instruments are allowing us to see deeper into our own galaxy for evidence of our own massive black hole. | B: quasars. |
Which gland is an extension of the hypothalamus?
Here are the choices:
A. pineal gland
B. posterior pituitary gland
C. salivary gland
D. adrenal gland | B: posterior pituitary gland. | |
Energy often changes between potential and what other kind of energy?
Here are the choices:
A. kinetic
B. magnetic
C. realized
D. thermal | Energy conversion occurs when energy changes from one type or form of energy to another. Energy often changes between potential and kinetic energy. Energy is always conserved during energy conversions. | A: kinetic. |
As the prokaryotic cell size increases, what happens to its surface area-to-volume ratio?
Here are the choices:
A. stagnates
B. halts
C. decreases
D. increases | 4.2 Prokaryotic Cells Prokaryotes are predominantly single-celled organisms of the domains Bacteria and Archaea. All prokaryotes have plasma membranes, cytoplasm, ribosomes, and DNA that is not membrane-bound. Most have peptidoglycan cell walls and many have polysaccharide capsules. Prokaryotic cells range in diameter from 0.1 to 5.0 μm. As a cell increases in size, its surface area-to-volume ratio decreases. If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume. | C: decreases. |
Why are seeds of a pine cone easily carried by the wind and dispersed?
Here are the choices:
A. seeds are dense
B. seeds have wings
C. seeds are sticky
D. seeds are small | One such strategy is to allow the wind to carry the seeds. With special adaptations in the seeds, the seeds can be carried long distances by the wind. For example, you might have noticed how the "fluff" of a dandelion moves in the wind. Each piece of fluff carries a seed to a new location. If you look under the scales of pine cone, you will see tiny seeds with "wings" that allow these seeds to be carried away by the wind. Maple trees also have specialized fruits with wing-like parts that help seed dispersal ( Figure below ). | B: seeds have wings. |
What do dendrites from the cell body recieve impulses from?
Here are the choices:
A. other cells
B. myelin
C. axon
D. other neurons | Dendrites extend from the cell body and receive nerve impulses from other neurons. | D: other neurons. |
During what are deletions and duplications especially likely to occur?
Here are the choices:
A. meiosis
B. electrolysis
C. endothermia
D. nucleus | A: meiosis. | |
What causes maple leaves to change their colors?
Here are the choices:
A. radiation reactions
B. chemical reactions
C. factor reactions
D. artificial preservatives | These vividly colored maple leaves were all bright green during the summer. Every fall, leaves of maple trees change to brilliant red, orange, and yellow colors. A change of color is a sign that a chemical change has taken place. Maple leaves change color because of chemical reactions. | B: chemical reactions. |
The cell body contains what central structure along with other organelles?
Here are the choices:
A. nucleus
B. protons
C. electron
D. neutron | The cell body contains the nucleus and other organelles. | A: nucleus. |
What is the term for the number that describes an electron's orbital orientation in space?
Here are the choices:
A. relative quantum number
B. magnetic electron number
C. magnetic quantum number
D. imaging quantum number | The magnetic quantum number , signified as , describes the orbital orientation in space. Electrons can be situated in one of three planes in three dimensional space around a given nucleus and . For a given value of the angular momentum quantum number , there can be values for . As an example:. | C: magnetic quantum number. |
Where do most red algae species live?
Here are the choices:
A. seas
B. oceans
C. lakes
D. rivers | Red algae are a very large group of protists making up about 5,000–6,000 species. They are mostly multicellular and live in the ocean. Many red algae are seaweeds and help create coral reefs. | B: oceans. |
What term is used for darwin's idea that in stable geologic and climatic conditions evolution occurred gradually?
Here are the choices:
A. canibalism
B. elitism
C. tinkering
D. gradualism | When geologic and climatic conditions are stable, evolution may occur gradually. This is how Darwin thought evolution occurred. This model of the timing of evolution is called gradualism . | D: gradualism. |
What element is all life built around?
Here are the choices:
A. hydrogen
B. carbon
C. oxygen
D. neon | The cell is the basic unit of life. A cell is made of molecules, which are made of elements. All life-which means all bacteria and archaea, all protists, fungi, plants and animals-is built around the element carbon, and four categories of organic compounds: carbohydrates, lipids, proteins, and nucleic acids. These molecules come together to form a cell, which is the basis of life. One particular type of protein, enzymes, are biological catalysts, allowing biochemical reactions to proceed at the rate necessary to maintain life. One other molecule, water, is also essential to life, though water is not an organic compound. | B: carbon. |
What are seamounts that rise above the water surface called?
Here are the choices:
A. islands
B. sandbars
C. coasts
D. reefs | A seamount is a volcanic mountain on the ocean floor. Seamounts that rise above the water surface are known as islands. There are many seamounts dotting the seafloor. | A: islands. |
Though often regarded as the supporting cast of the nervous system, glial cells in the brain actually outnumber what by a factor of ten?
Here are the choices:
A. neurons
B. blood cells
C. electrons
D. muscles | Glia While glia are often thought of as the supporting cast of the nervous system, the number of glial cells in the brain actually outnumbers the number of neurons by a factor of ten. Neurons would be unable to function without the vital roles that are fulfilled by these glial cells. Glia guide developing neurons to their destinations, buffer ions and chemicals that would otherwise harm neurons, and provide myelin sheaths around axons. Scientists have recently discovered that they also play a role in responding to nerve activity and modulating communication between nerve cells. When glia do not function properly, the result can be disastrous—most brain tumors are caused by mutations in glia. Types of Glia There are several different types of glia with different functions, two of which are shown in Figure 35.7. Astrocytes, shown in Figure 35.8a make contact with both capillaries and neurons in the CNS. They provide nutrients and other substances to neurons, regulate the concentrations of ions and chemicals in the extracellular fluid, and provide structural support for synapses. Astrocytes also form the blood-brain barrier—a structure that blocks entrance of toxic substances into the brain. Astrocytes, in particular, have been shown through calcium imaging experiments to become active in response to nerve activity, transmit calcium waves between astrocytes, and modulate the activity of surrounding synapses. Satellite glia provide nutrients and structural support for neurons in the PNS. Microglia scavenge and degrade dead cells and protect the brain from invading microorganisms. Oligodendrocytes, shown in Figure 35.8b form myelin sheaths around axons in the CNS. One axon can be myelinated by several oligodendrocytes, and one oligodendrocyte can provide myelin for multiple neurons. This is distinctive from the PNS where a single Schwann cell provides myelin for only one axon as the entire Schwann cell surrounds the axon. Radial glia serve as scaffolds for developing neurons as they migrate to their end destinations. Ependymal cells line fluid-filled ventricles of the brain and the central canal of the spinal cord. They are involved in the production of cerebrospinal fluid, which serves as a cushion for the brain, moves the fluid between the spinal cord and the brain, and is a component for the choroid plexus. | A: neurons. |
Dinosaurs filled the niches that mammals fill today during which era?
Here are the choices:
A. Phanerozoic
B. Cenozoic
C. mesozoic
D. Proterozoic | In the Mesozoic, dinosaurs filled the niches that mammals fill today. | C: mesozoic. |
The magnet field of earth is called what?
Here are the choices:
A. troposphere
B. magnetosphere
C. atmosphere
D. ionosphere | Earth is a giant magnet with north and south magnetic poles and a magnetic field called the magnetosphere. Evidence in rocks shows that Earth’s magnetic poles switched positions hundreds of times in the past. Scientists think that Earth’s magnetic field is caused by the movement of charged particles through molten metals in the outer core. | B: magnetosphere. |
What two types of hormones regulate mammalian reproduction?
Here are the choices:
A. pheromones and enzymes
B. endorphins and adrenaline
C. tropic and sex
D. tropic and subtropic | 46.4 The interplay of tropic and sex hormones regulates mammalian reproduction. | C: tropic and sex. |
In addition to five classes of fish, what other classes make up the species of vertebrates?
Here are the choices:
A. insects, amphibians, reptiles, and birds
B. reptiles, birds, mammals, and primates
C. amphibians, reptiles, birds, and mammals
D. amphibians , vertebrae , birds , and mammals | There are about 50,000 living species of vertebrates. They are placed in nine classes: five classes of fish plus amphibians, reptiles, birds, and mammals. | C: amphibians, reptiles, birds, and mammals. |
What is the method of reproduction for echinoderms?
Here are the choices:
A. external fertilization
B. fragmentation
C. internal fertilization
D. pollination | Echinoderms generally reproduce by external fertilization; regeneration is fairly common among echinoderms. | A: external fertilization. |
What is happening to the rate of the expansion of the universe?
Here are the choices:
A. it is stable
B. it is unknown
C. it is decreasing
D. it is increasing | The rate of the expansion of the universe is increasing. The cause of this increase is unknown; one possible explanation involves a new form of energy called dark energy. | D: it is increasing. |
What are required when the damage from trauma or infection cannot be closed with sutures or staples?
Here are the choices:
A. bone grafts
B. skin grafts
C. debris grafts
D. tree grafts | Skin grafts are required when the damage from trauma or infection cannot be closed with sutures or staples. Watch this video (http://openstaxcollege. org/l/skingraft) to learn more about skin grafting procedures. | B: skin grafts. |
In addition to a vibrating electric field what does an electromagnetic wave consist of?
Here are the choices:
A. gravitational field
B. magnetic field
C. radiation field
D. molecular field | An electromagnetic wave consists of vibrating electric and magnetic fields. | B: magnetic field. |
What type of bones serve as points of attachment for muscles and often protect internal organs?
Here are the choices:
A. irregular bones
B. short bones
C. sesamoid bones
D. flat bones | Flat Bones The term “ flat bone” is somewhat of a misnomer because, although a flat bone is typically thin, it is also often curved. Examples include the cranial (skull) bones, the scapulae (shoulder blades), the sternum (breastbone), and the ribs. Flat bones serve as points of attachment for muscles and often protect internal organs. | D: flat bones. |
The presence of what stratospheric gas layer decreases the frequency of skin cancer and other damaging effects of ultraviolet radiation?
Here are the choices:
A. ozone
B. cumulonimbus
C. plasma
D. smog | O 3(g) ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ → O(g) + O 2(g) The reactive oxygen atoms recombine with molecular oxygen to complete the ozone cycle. The presence of stratospheric ozone decreases the frequency of skin cancer and other damaging effects of ultraviolet radiation. It has been clearly demonstrated that chlorofluorocarbons, CFCs (known commercially as Freons), which were present as aerosol propellants in spray cans and as refrigerants, caused depletion of ozone in the stratosphere. This occurred because ultraviolet light also causes CFCs to decompose, producing atomic chlorine. The chlorine atoms react with ozone molecules, resulting in a net removal of O3 molecules from stratosphere. This process is explored in detail in our coverage of chemical kinetics. There is a worldwide effort to reduce the amount of CFCs used commercially, and the ozone hole is already beginning to decrease in size as atmospheric concentrations of atomic chlorine decrease. While ozone in the stratosphere helps protect us, ozone in the troposphere is a problem. This ozone is a toxic component of photochemical smog. The uses of ozone depend on its reactivity with other substances. It can be used as a bleaching agent for oils, waxes, fabrics, and starch: It oxidizes the colored compounds in these substances to colorless compounds. It is an alternative to chlorine as a disinfectant for water. | A: ozone. |
The characteristic sound of a motorcycle buzzing by is an example of which effect?
Here are the choices:
A. coreolis effect
B. warp effect
C. doppler effect
D. polar effect | 17.4 Doppler Effect and Sonic Booms The characteristic sound of a motorcycle buzzing by is an example of the Doppler effect. The high-pitch scream shifts dramatically to a lower-pitch roar as the motorcycle passes by a stationary observer. The closer the motorcycle brushes by, the more abrupt the shift. The faster the motorcycle moves, the greater the shift. We also hear this characteristic shift in frequency for passing race cars, airplanes, and trains. It is so familiar that it is used to imply motion and children often mimic it in play. The Doppler effect is an alteration in the observed frequency of a sound due to motion of either the source or the observer. Although less familiar, this effect is easily noticed for a stationary source and moving observer. For example, if you ride a train past a stationary warning bell, you will hear the bell’s frequency shift from high to low as you pass by. The actual change in frequency due to relative motion of source and observer is called a Doppler shift. The Doppler effect and Doppler shift are named for the Austrian physicist and mathematician Christian Johann Doppler (1803–1853), who did experiments with both moving sources and moving observers. Doppler, for example, had musicians play on a moving open train car and also play standing next to the train tracks as a train passed by. Their music was observed both on and off the train, and changes in frequency were measured. What causes the Doppler shift? Figure 17.14, Figure 17.15, and Figure 17.16 compare sound waves emitted by stationary and moving sources in a stationary air mass. Each disturbance spreads out spherically from the point where the sound was emitted. If the source is stationary, then all of the spheres representing the air compressions in the sound wave centered on the same. | C: doppler effect. |
What protects the scalp from ultraviolet light exposure and loss of body heat?
Here are the choices:
A. temporal hair
B. head hair
C. ground hair
D. receding hair | Head hair protects the scalp from ultraviolet light exposure and loss of body heat. Hair in eyelashes, eyebrows, and nostrils traps water, dust, and other irritants. Nails protect the ends of fingers and toes and enhance the sense of touch. | B: head hair. |
What is the name given to the use of controlled nuclear fusion as an energy source?
Here are the choices:
A. thermonuclear power
B. generator power
C. fossil fuel
D. half-life | 32.5 Fusion While basking in the warmth of the summer sun, a student reads of the latest breakthrough in achieving sustained thermonuclear power and vaguely recalls hearing about the cold fusion controversy. The three are connected. The Sun’s energy is produced by nuclear fusion (see Figure 32.15). Thermonuclear power is the name given to the use of controlled nuclear fusion as an energy source. While research in the area of thermonuclear power is progressing, high temperatures and containment difficulties remain. The cold fusion controversy centered around unsubstantiated claims of practical fusion power at room temperatures. | A: thermonuclear power. |
Some compounds containing hydrogen are members of an important class of substances known as what?
Here are the choices:
A. ions
B. proteins
C. bases
D. acids | Binary Acids Some compounds containing hydrogen are members of an important class of substances known as acids. The chemistry of these compounds is explored in more detail in later chapters of this text, but for now, it will suffice to note that many acids release hydrogen ions, H+, when dissolved in water. To denote this distinct chemical property, a mixture of water with an acid is given a name derived from the compound’s name. If the compound is a binary acid (comprised of hydrogen and one other nonmetallic element): 1. The word “hydrogen” is changed to the prefix hydro2. The other nonmetallic element name is modified by adding the suffix -ic 3. The word “acid” is added as a second word. | D: acids. |
In which organ are bile acids made
Here are the choices:
A. gall bladder
B. spleen
C. kidney
D. liver | Bile salts are bile acids that help to break down fat. Bile acids are made in the liver. When you eat a meal, bile is secreted into the intestine, where it breaks down the fats ( Figure below ). | D: liver. |
What is the layer of electrons that encircle the nucleus at a distinct energy level called?
Here are the choices:
A. electron shell
B. ions shell
C. molecular shell
D. vortex shell | The Behavior of Electrons In the human body, atoms do not exist as independent entities. Rather, they are constantly reacting with other atoms to form and to break down more complex substances. To fully understand anatomy and physiology you must grasp how atoms participate in such reactions. The key is understanding the behavior of electrons. Although electrons do not follow rigid orbits a set distance away from the atom’s nucleus, they do tend to stay within certain regions of space called electron shells. An electron shell is a layer of electrons that encircle the nucleus at a distinct energy level. The atoms of the elements found in the human body have from one to five electron shells, and all electron shells hold eight electrons except the first shell, which can only hold two. This configuration of electron shells is the same for all atoms. The precise number of shells depends on the number of electrons in the atom. Hydrogen and helium have just one and two electrons, respectively. If you take a look at the periodic table of the elements, you will notice that hydrogen and helium are placed alone on either sides of the top row; they are the only elements that have just one electron shell (Figure 2.7). A second shell is necessary to hold the electrons in all elements larger than hydrogen and helium. Lithium (Li), whose atomic number is 3, has three electrons. Two of these fill the first electron shell, and the third spills over into a second shell. The second electron shell can accommodate as many as eight electrons. Carbon, with its six electrons, entirely fills its first shell, and half-fills its second. With ten electrons, neon (Ne) entirely fills its two electron shells. Again, a look at the periodic table reveals that all of the elements in the second row, from lithium to neon, have just two electron shells. Atoms with more than ten electrons require more than two shells. These elements occupy the third and subsequent rows of the periodic table. | A: electron shell. |
What is the most common way to classify stars?
Here are the choices:
A. by age
B. by distance
C. by size
D. by color | The most common way of classifying stars is by color as shown, in Table below . Each class of star is given a letter, a color, and a range of temperatures. The letters don’t match the color names because stars were first grouped as A through O. It wasn't until later that their order was corrected to go by increasing temperature. When you try to remember the order, you can use this phrase: “Oh Be A Fine Good Kid, Man. ”. | D: by color. |
What is a homogeneous mixture also known as?
Here are the choices:
A. structure
B. solution
C. mixture
D. element | A solution is another name for a homogeneous mixture. http://catalog. flatworldknowledge. com/bookhub/reader/2547 - gob-ch01defined a mixture as a material composed of two or more substances. In a solution, the combination is so intimate that the different substances cannot be differentiated by sight, even with a microscope. Compare, for example, a mixture of salt and pepper and another mixture consisting of salt and water. In the first mixture, we can readily see individual grains of salt and the flecks of pepper. A mixture of salt and pepper is not a solution. However, in the second mixture, no matter how carefully we look, we cannot see two different substances. Salt dissolved in water is a solution. Saylor URL: http://www. saylor. org/books. | B: solution. |
Living organisms are made up of what type of carbon-based compounds?
Here are the choices:
A. synthetic
B. microbial
C. biophysical
D. biochemical | Biochemical compounds are carbon-based compounds that make up living organisms. There are four main classes of biochemical compounds: carbohydrates, proteins, lipids, and nucleic acids. The classes have different structures and functions. | D: biochemical. |
What classification system was developed by a swedish botanist trying to classify all known living things?
Here are the choices:
A. linnaean system
B. taxonomical system
C. plantological system
D. bionumerical system | All modern classification systems have their roots in the Linnaean classification system. It was developed by Swedish botanist Carolus Linnaeus in the 1700s. He tried to classify all living things that were known at his time. He grouped together organisms that shared obvious physical traits, such as number of legs or shape of leaves. For his contribution, Linnaeus is known as the “father of taxonomy. ” You can learn more about Linnaeus and his system of classification by watching the video at this link: http://teachertube. com/viewVideo. php?video_id=169889 . | A: linnaean system. |
The word science is derived from what latin word?
Here are the choices:
A. scefitana
B. scitifica
C. scentia
D. sceria | The Nature of Science Biology is a science, but what exactly is science? What does the study of biology share with other scientific disciplines? Science (from the Latin scientia, meaning "knowledge") can be defined as knowledge about the natural world. Science is a very specific way of learning, or knowing, about the world. The history of the past 500 years demonstrates that science is a very powerful way of knowing about the world; it is largely responsible for the technological revolutions. | C: scentia. |
In a model of an atom, the level with the least energy is the one closest to what?
Here are the choices:
A. protons
B. surface
C. center
D. nucleus | The model of an atom in Figure below has six energy levels. The level with the least energy is the one closest to the nucleus. As you go farther from the nucleus, the levels have more and more energy. Electrons can jump from one energy level to another. If an atom absorbs energy, some of its electrons can jump to a higher energy level. If electrons jump to a lower energy level, the atom emits, or gives off, energy. You can see an animation at this happening at the URL below. | D: nucleus. |
What is the process of making atp without oxygen called?
Here are the choices:
A. fermentation
B. Cell Division
C. condensation
D. photosynthesis | An important way of making ATP without oxygen is called fermentation . It involves glycolysis, but not the other two stages of aerobic respiration. Many bacteria and yeasts carry out fermentation. People use these organisms to make yogurt, bread, wine, and biofuels. Human muscle cells also use fermentation. This occurs when muscle cells cannot get oxygen fast enough to meet their energy needs through aerobic respiration. | A: fermentation. |
What is the type of mining called when materials are removed along a strip?
Here are the choices:
A. edge mining
B. surface mining
C. pit mining
D. strip mining | Other methods of surface mining include strip mining, placer mining, and dredging. Strip mining is like open pit mining but with material removed along a strip. A quarry is a type of open-pit mine that produces rocks and minerals that are used to make buildings and roads. | D: strip mining. |
Chlorine is a nonmetal and gains one electron in becoming a what?
Here are the choices:
A. sulfate
B. carbonate
C. atom
D. anion | We will use sodium chloride as an example to demonstrate the nature of the ionic bond and how it forms. As you know, sodium is a metal and loses its one valence electron to become a cation. Chlorine is a nonmetal and gains one electron in becoming an anion. Both achieve a noble-gas electron configuration. However, electrons cannot be simply “lost” to nowhere in particular. A more accurate way to describe what is happening is that a single electron is transferred from the sodium atom to the chlorine atom as shown below. | D: anion. |
The most common mode of asexual reproduction is through the formation of asexual these?
Here are the choices:
A. spores
B. atoms
C. fibers
D. cells | The most common mode of asexual reproduction is through the formation of asexual spores, which are produced by one parent only (through mitosis) and are genetically identical to that parent (Figure 24.8). Spores allow fungi to expand their distribution and colonize new environments. They may be released from the parent thallus either outside or within a special reproductive sac called a sporangium. | A: spores. |
Some species of fish carry their fertilized eggs in their mouth until they hatch; this is called what?
Here are the choices:
A. schooling
B. spawning
C. mouth brooding
D. internal reproduction | Mouth Brooding. Some species of fish carry their fertilized eggs in their mouth until they hatch. This is called mouth brooding. If you look closely, you can see the eggs inside the mouth of the cardinalfish pictured here. | C: mouth brooding. |
In a chemical reaction, what, in general, comes together in order to form a product?
Here are the choices:
A. reactants
B. liquids
C. gases
D. propellants | Bonds break and reform during chemical reactions. Reactants and products contain the same atoms, but they are rearranged during the reaction, so reactants and products are different substances. | A: reactants. |
What decides what may enter or leave a cell?
Here are the choices:
A. cell membrane
B. cell wall
C. nucleus
D. golgi apparatus | The cell membrane also decides what may enter or leave a cell. The membrane is said to be semipermeable or selectively permeable, allowing only certain ions and organic molecules to cross the membrane. The plasma membrane contain many proteins, as well as other lipids called sterols. The proteins have various functions, such as channels (channel proteins) that allow certain molecules into the cell, and receptors (receptor proteins) that bind to signal molecules. In Figure above , the smaller (green) molecules shown between the phospholipids are cholesterol molecules. Cholesterol helps keep the plasma membrane firm and stable over a wide range of temperatures. At least ten different types of lipids are commonly found in plasma membranes. Each type of cell or organelle will have a different percentage of each lipid, protein and carbohydrate. | A: cell membrane. |
What trophic level are secondary consumers (which eat primary consumers) considered to be?
Here are the choices:
A. trophic level 3
B. trophic level 2
C. trophic level 5
D. trophic level 4 | Trophic level 3 = secondary consumers that eat primary consumers. | A: trophic level 3. |
What type of map projection is used for small areas to avoid distortion?
Here are the choices:
A. unmeasured projection
B. equatorial projection
C. mercator projection
D. gnomic projection | What if you want a different approach? Let's say you don't want to wrap a flat piece of paper around a round object. You could put a flat piece of paper right on the area that you want to map. This type of map is called a gnomonic map projection ( Figure below ). The paper only touches Earth at one point. The sizes and shapes of countries near that point are good. The poles are often mapped this way to avoid distortion. A gnomic projection is best for use over a small area. | D: gnomic projection. |
What do atoms form by sharing valence electrons?
Here are the choices:
A. phenotype bonds
B. neutron bonds
C. ionic bonds
D. covalent bonds | Atoms form covalent bonds by sharing valence electrons. The valence electrons are located in atomic orbitals. However, when a bond forms, the structure of the atomic orbitals changes. In this lesson, we will see how the atomic orbitals interact to share valence electrons and form different types of covalent bonds. | D: covalent bonds. |
What is the process that moves particles by rolling or dragging along the bottom of the water?
Here are the choices:
A. compression
B. isolation
C. compaction
D. traction | The biggest particles, including gravel and pebbles, are moved by traction . In this process, the particles roll or drag along the bottom of the water. | D: traction. |
Alkenes react with what to form dihalides?
Here are the choices:
A. oxides
B. antioxidants
C. halogens
D. amines | Alkenes can react with halogens to form dihalides. | C: halogens. |
A supervolcano that may have killed all but 10,000 humans resulted in what phenomenon, lasting up to a decade?
Here are the choices:
A. volcanic winter
B. volcanic summer
C. volcano fall
D. volcano spring | A supervolcano eruption took place at Lake Toba in northern Sumatra about 75,000 years ago ( Figure below ). This was the largest eruption in the past 25 million years. As much as 2,800 cubic kilometers of material was ejected into the atmosphere. The result was a 6- to 10-year volcanic winter. Some scientists think that only 10,000 humans survived worldwide. The numbers of other mammals also plummeted. | A: volcanic winter. |
The existence of the plasma membrane was identified in the 1890s, and its chemical components were identified in 1915. the principal components identified at that time were these?
Here are the choices:
A. lipids and proteins
B. gasses and proteins
C. lipids and carbohydrates
D. carbohydrates and proteins | Fluid Mosaic Model The existence of the plasma membrane was identified in the 1890s, and its chemical components were identified in 1915. The principal components identified at that time were lipids and proteins. The first widely accepted model of the plasma membrane’s structure was proposed in 1935 by Hugh Davson and James Danielli; it was based on the “railroad track” appearance of the plasma membrane in early electron micrographs. They theorized that the structure of the plasma membrane resembles a sandwich, with protein being analogous to the bread, and lipids being analogous to the filling. In the 1950s, advances in microscopy, notably transmission electron microscopy (TEM), allowed researchers to see that the core of the plasma membrane consisted of a double, rather than a single, layer. A new model that better explains both the microscopic observations and the function of that plasma membrane was proposed by S. Singer and Garth L. Nicolson in 1972. The explanation proposed by Singer and Nicolson is called the fluid mosaic model. The model has evolved somewhat over time, but it still best accounts for the structure and functions of the plasma membrane as we now understand them. The fluid mosaic model describes the structure of the plasma membrane as a mosaic of components—including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character. Plasma membranes range from 5 to 10 nm in thickness. For comparison, human red blood cells, visible via light microscopy, are approximately 8 µm wide, or approximately 1,000 times wider than a plasma membrane. The membrane does look a bit like a sandwich (Figure 5.2). | A: lipids and proteins. |
Acting like drawstrings to close off the alimentary canal, what regulates the passage of material between compartments?
Here are the choices:
A. uterus
B. intestine
C. sphincter
D. hamstring | C: sphincter. | |
What man-made substance tends to break down ozone in the stratosphere?
Here are the choices:
A. steel
B. gasoline
C. plastic
D. cfcs | CFCs break down ozone in the stratosphere. | D: cfcs. |
What in saliva protects the lining of the mouth from abrasion and lubricates food for easier swallowing?
Here are the choices:
A. hairs
B. mucus
C. phloem
D. spores | B: mucus. | |
Which latitudes get the most energy from the sun?
Here are the choices:
A. highest latitudes
B. middle latitudes
C. polular latitudes
D. lowest latitudes | The lowest latitudes get the most energy from the Sun. The highest latitudes get the least. | D: lowest latitudes. |
Extended stays in zero gravity are not healthy for human beings. thus, for the comfort of the astronauts, the station is rotated so that the astronauts feel there is what?
Here are the choices:
A. Fixed Gravity
B. internal gravity
C. revealed gravity
D. still gravity | A space station was established far from the gravitational field of Earth. Extended stays in zero gravity are not healthy for human beings. Thus, for the comfort of the astronauts, the station is rotated so that the astronauts feel there is an internal gravity. The rotation speed is such that the apparent acceleration of gravity is . The direction of rotation is counter-clockwise. If the radius of the station is , what is its rotational speed, ?. | B: internal gravity. |
What parts of the planet does solar energy have difficulty reaching?
Here are the choices:
A. poles
B. equators
C. deserts
D. oceans | Much less solar energy gets to the poles. | A: poles. |
Oceans are made of a solution of what?
Here are the choices:
A. salt and carbon
B. salt and water
C. salt and algae
D. water and carbon | Flickr:xiquinhosilva. Oceans are made of a solution of salt and water . CC BY 2.0. | B: salt and water. |
Although humans require it, what accounts for just one percent of all water on earth?
Here are the choices:
A. fresh water
B. glaciers
C. snow
D. salt water | All living things need water. For most human uses, water must be fresh. Of all the water on Earth, only 1 percent is fresh, liquid water. Most of the rest of Earth’s water is either salt water in the ocean or ice in glaciers and ice caps. | A: fresh water. |
Arachidic, stearic, and palmitic fatty acids are examples of what type of fatty acid?
Here are the choices:
A. compacted
B. integral
C. neutral
D. saturated | Saturated and Unsaturated Fatty Acids. Saturated fatty acids include arachidic, stearic, and palmitic fatty acids. Unsaturated fatty acids include all the other fatty acids in the figure. Notice how all the unsaturated fatty acids have bent chains, whereas the saturated fatty acids have straight chains. | D: saturated. |
Weather maps show storms, air masses, and what?
Here are the choices:
A. patterns
B. currents
C. regions
D. fronts | Weather maps show storms, air masses, and fronts. | D: fronts. |
What is a pure substance called?
Here are the choices:
A. a liquid
B. homogeneous matter
C. a mixture
D. an element | A pure substance is called an element . An element is a pure substance because it cannot be separated into any other substances. Currently, 92 different elements are known to exist in nature, although additional elements have been formed in labs. All matter consists of one or more of these elements. Some elements are very common; others are relatively rare. The most common element in the universe is hydrogen, which is part of Earth’s atmosphere and a component of water. The most common element in Earth’s atmosphere is nitrogen, and the most common element in Earth’s crust is oxygen. Several other elements are described in the musical video at this URL:. | D: an element. |
What term describes the energy of an object that is moving or has the potential to move?
Here are the choices:
A. thermal energy
B. mechanical energy
C. stationary energy
D. molecular energy | Mechanical energy is the energy of an object that is moving or has the potential to move. It is the sum of an object’s kinetic and potential energy. In Figure below , the basketball has mechanical energy because it is moving. The arrow in the same figure has mechanical energy because it has the potential to move due to the elasticity of the bow. What are some other examples of mechanical energy?. | B: mechanical energy. |
Evidence for the presence of what on mars makes scientists think that life might have existed there in the past?
Here are the choices:
A. gas
B. plasma
C. air
D. water | Curiosity, the rover, has found evidence of a flowing stream on Mars. Layers of smooth, water-polished pebbles have been photographed. This is exactly what you would see in a stream on Earth. There are many surface features that look like water-eroded canyons. Since there was liquid water on Mars, scientists think that life might have existed there in the past. One of Curiosity's tasks is to sample the soil to search for carbon and other evidence of life. | D: water. |
What does photosynthesis allow plants to generate?
Here are the choices:
A. enriched molecules
B. clorophyll
C. organic molecules
D. geometric molecules | C: organic molecules. | |
How many low and high tides occur per day?
Here are the choices:
A. ten
B. four
C. six
D. two | The primary cause of tides is the gravitational attraction of the Moon. This causes two high and two low tides a day. | D: two. |
What makes up most of the inside of a plant?
Here are the choices:
A. star tissue
B. animal tissue
C. mitochondria
D. ground tissue | In normal faults , the hanging wall drops down relative to the footwall. Normal faults are caused by tension that pulls the crust apart. This causes the hanging wall to slide down. Normal faults can build huge mountain ranges in regions experiencing tension ( Figure below ). | D: ground tissue. |
The first living cells may have evolved around how long ago?
Here are the choices:
A. 900,000 years
B. 2.2 billion years
C. 4 billion years
D. 6 billion years | The Precambrian Supereon (4.6 billion–544 million years ago) is the first major division of the geologic time scale. The first living cells may have evolved around 4 billion years ago. By 1 million years ago, the first multicellular eukaryotes had evolved. The Precambrian ended with the first of six mass extinctions that occurred during Earth’s history. | C: 4 billion years. |
What kind of relay occurs between the uterus, hypothalamus, and the posterior pituitary to assure an adequate supply of the hormone oxytocin during childbirth?
Here are the choices:
A. currents feedback
B. positive feedback
C. affirmative feedback
D. pressure feedback | Labor and Birth Labor is the physical efforts of expulsion of the fetus and the placenta from the uterus during birth (parturition). Toward the end of the third trimester, estrogen causes receptors on the uterine wall to develop and bind the hormone oxytocin. At this time, the baby reorients, facing forward and down with the back or crown of the head engaging the cervix (uterine opening). This causes the cervix to stretch and nerve impulses are sent to the hypothalamus, which signals for the release of oxytocin from the posterior pituitary. The oxytocin causes the smooth muscle in the uterine wall to contract. At the same time, the placenta releases prostaglandins into the uterus, increasing the contractions. A positive feedback relay occurs between the uterus, hypothalamus, and the posterior pituitary to assure an adequate supply of oxytocin. As more smooth muscle cells are recruited, the contractions increase in intensity and force. There are three stages to labor. During stage one, the cervix thins and dilates. This is necessary for the baby and placenta to be expelled during birth. The cervix will eventually dilate to about 10 cm. During stage two, the baby is expelled from the uterus. The uterus contracts and the mother pushes as she compresses her abdominal muscles to aid the delivery. The last stage is the passage of the placenta after the baby has been born and the organ has completely disengaged from the uterine wall. If labor should stop before stage two is reached, synthetic oxytocin, known as Pitocin, can be administered to restart and maintain labor. An alternative to labor and delivery is the surgical delivery of the baby through a procedure called a Caesarian section. This is major abdominal surgery and can lead to post-surgical complications for the mother, but in some cases it may be the only way to safely deliver the baby. | B: positive feedback. |
What type of plants do not typically require deep roots or woody stems?
Here are the choices:
A. dry plants
B. surface plants
C. aquatic plants
D. bacterial plants | Modern plants that live in water are called aquatic plants . Living in water has certain advantages for plants. One advantage is, well, the water. There's plenty of it and it's all around. Therefore, most aquatic plants do not need adaptations for absorbing, transporting, and conserving water. They can save energy and matter by not growing extensive root systems, vascular tissues, or thick cuticle on leaves. Support is also less of a problem because of the buoyancy of water. As a result, adaptations such as strong woody stems and deep anchoring roots are not necessary for most aquatic plants. | C: aquatic plants. |
What is the key to the demographic transition?
Here are the choices:
A. higher death rates
B. higher birth rates
C. reduced family size
D. higher expatriation | C: reduced family size. | |
For the nervous system to function, neurons must be able to send and receive what?
Here are the choices:
A. signals
B. information
C. proteins
D. pulses | Nerve Impulse Transmission within a Neuron For the nervous system to function, neurons must be able to send and receive signals. These signals are possible because each neuron has a charged cellular membrane (a voltage difference between the inside and the outside), and the charge of this membrane can change in response to neurotransmitter molecules released from other neurons and environmental stimuli. To understand how neurons communicate, one must first understand the basis of the baseline or ‘resting’ membrane charge. Neuronal Charged Membranes The lipid bilayer membrane that surrounds a neuron is impermeable to charged molecules or ions. To enter or exit the neuron, ions must pass through special proteins called ion channels that span the membrane. Ion channels have different configurations: open, closed, and inactive, as illustrated in Figure 35.9. Some ion channels need to be activated in order to open and allow ions to pass into or out of the cell. These ion channels are sensitive to the environment and can change their shape accordingly. Ion channels that change their structure in response to voltage changes are called voltage-gated ion channels. Voltage-gated ion channels regulate the relative concentrations of different ions inside and outside the cell. The difference in total charge between the inside and outside of the cell is called the membrane potential. | A: signals. |
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