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Plants that live in the desert are called? | sporozoans | xerozoans | heatophiles | xerophytes | Plants that live in extremely dry environments have the opposite problem: how to get and keep water. Plants that are adapted to very dry environments are called xerophytes . Their adaptations may help them increase water intake, decrease water loss, or store water when it is available. |
Dolphins are what type of animal? | whale | reptile | fish | mammal | Dolphins are mammals that have adapted to swimming and reproducing in water. |
What is the energy of moving matter? | residual energy | potential energy | binary energy | kinetic energy | Kinetic energy is the energy of moving matter. Things with kinetic energy can do work. Kinetic energy depends on an object’s mass and velocity. |
The two parts of photosynthesis photosynthesis takes place in two stages: the light-dependent reactions and which cycle? | dark cycle | colors cycle | klein cycle | calvin cycle | The Two Parts of Photosynthesis Photosynthesis takes place in two stages: the light-dependent reactions and the Calvin cycle. In the light-dependent reactions, which take place at the thylakoid membrane, chlorophyll absorbs energy from sunlight and then converts it into chemical energy with the use of water. The light-dependent reactions release oxygen from the hydrolysis of water as a byproduct. In the Calvin cycle, which takes place in the stroma, the chemical energy derived from the light-dependent reactions drives both the capture of carbon in carbon dioxide molecules and the subsequent assembly of sugar molecules. The two reactions use carrier molecules to transport the energy from one to the other. The carriers that move energy from the light-dependent reactions to the Calvin cycle reactions can be thought of as “full” because they bring energy. After the energy is released, the “empty” energy carriers return to the light-dependent reactions to obtain more energy. |
In an atom, what two major types of particles are located in the nucleus? | ions and electrons | electrons and neutrons | molecules and neutrons | protons and neutrons | Rutherford’s atomic model became known as the nuclear model . In the nuclear atom, the protons and neutrons, which comprise nearly all of the mass of the atom, are located in the nucleus at the center of the atom. The electrons are distributed around the nucleus and occupy most of the volume of the atom. It is worth emphasizing just how small the nucleus is compared to the rest of the atom. If we could blow up an atom to be the size of a large professional football stadium, the nucleus would be about the size of a marble. |
What is the first part of the large intestine, where wastes enter from the small intestine? | sacrum | tectum | spleen | cecum | The cecum is the first part of the large intestine, where wastes enter from the small intestine. The wastes are in a liquid state. As they pass through the colon , which is the second part of the large intestine, excess water is absorbed. The remaining solid wastes are called feces . Feces accumulate in the rectum , which is the third part of the large intestine. As the rectum fills, the feces become compacted. After a certain amount of feces accumulate, they are eliminated from the body. A sphincter controls the anus and opens to let feces pass through. |
Each pollen grain has two coverings: the exine (thicker, outer layer) and the what? | cytoplasm | tube nucleus | pollen tube | intine | Each pollen grain has two coverings: the exine (thicker, outer layer) and the intine (Figure 32.7). The exine contains sporopollenin, a complex waterproofing substance supplied by the tapetal cells. Sporopollenin allows the pollen to survive under unfavorable conditions and to be carried by wind, water, or biological agents without undergoing damage. Female Gametophyte (The Embryo Sac) While the details may vary between species, the overall development of the female gametophyte has two distinct phases. First, in the process of megasporogenesis, a single cell in the diploid megasporangium—an area of tissue in the ovules—undergoes meiosis to produce four megaspores, only one of which survives. During the second phase, megagametogenesis, the surviving haploid megaspore undergoes mitosis to produce an eight-nucleate, seven-cell female gametophyte, also known as the megagametophyte or embryo sac. Two of the nuclei—the polar nuclei—move to the equator and fuse, forming a single, diploid central cell. This central cell later fuses with a sperm to form the triploid endosperm. Three nuclei position themselves on the end of the embryo sac opposite the micropyle and develop into the antipodal cells, which later degenerate. The nucleus closest to the micropyle becomes the female gamete, or egg cell, and the two adjacent nuclei develop into synergid cells (Figure 32.8). The synergids help guide the pollen tube for successful fertilization, after which they disintegrate. Once fertilization is complete, the resulting diploid zygote develops into the embryo, and the fertilized ovule forms the other tissues of the seed. |
In stars like our sun, hydrogen atoms join together to create what? | iron atom | water molecule | oxygen atom | helium atom | A nuclear fusion reaction is so named because the nuclei (center) of atoms fuse (join) together in the process. In stars like our Sun, hydrogen atoms join together to create a helium atom. Nuclear fusion reactions need a lot of energy to get started. Once they begin, they produce even more energy. ( Figure below ). |
How do bacteria reproduce? | multiple fission | natural fission | residual fission | binary fission | New mitochondria and chloroplasts are produced through a process similar to binary fission . Bacteria also reproduce through binary fission. |
What sort of gas is found in balloons and blimps, and is used to make them float in the sky? | radon | oxygen | hydrogen | helium | Helium has long been used in balloons and blimps. Since it is much less dense than air, it will float above the ground. We can buy small balloons filled with helium at stores, but large ones (such as the balloon seen above) are much more expensive and take up a lot more helium. |
What color is pyrite? | silver | blue | black | gold | Pyrite has a similar color to gold. The appearance of the striations make pyrite different from gold. |
Planting a row of trees around a field or erecting a fence on a sand dune helps prevent what form of erosion? | rain | fire | water | wind | Planting rows of trees around fields is another way to reduce wind erosion. The trees slow down the wind, so it doesn’t cause as much erosion. Fences like the one in Figure below serve the same purpose. The fence in the figure is preventing erosion and migration of sand dunes on a beach. |
What structure connects the fetus to the placenta, allowing the exchange of gases? | belly button | sediment cord | skin cord | umbilical cord | Within seconds of birth, the umbilical cord is cut. Without this connection to the placenta, the baby can’t exchange gases, so carbon dioxide quickly builds up in the baby’s blood. This stimulates the baby’s brain to trigger breathing, and the newborn takes her first breath. |
Glass, rubber, and plastics are examples of which type of solids? | porous | dubious | aqueous | amorphous | Examples of amorphous solids include glass, rubber, and plastics. |
What is the process bacteria use to break down chemicals into food? | cellular respiration | biosynthesis | gametogenesis | chemosynthesis | The bacteria that make food from chemicals are also primary producers. These organisms do not do photosynthesis since there is no light at the vents. They do something called chemosynthesis. They break down chemicals to make food. |
A fully developed placenta is made up of a large mass of what? | estrogen hormones | brain tissues | plant cells | blood vessels | A fully developed placenta, like the one in Figure below , is made up of a large mass of blood vessels from both mother and fetus. The maternal and fetal vessels are close together but separated by tiny spaces. This allows the mother’s and fetus’s blood to exchange substances across their capillary walls without the blood actually mixing. |
What is an element that tend to be malleable? | lanthanide | actinide | mixture | metal | Metals tend to be malleable. This means that they can be formed into thin sheets without breaking. An example is aluminum foil, also pictured in the Figure below . |
As a diver descends, the increase in pressure causes the body’s air pockets in the ears and lungs to do what? | blow up | heat up | expand | compress | from the atmosphere at sea level. As a diver descends, the increase in pressure causes the body’s air pockets in the ears and lungs to compress; on the ascent, the decrease in pressure causes these air pockets to expand, potentially rupturing eardrums or bursting the lungs. Divers must therefore undergo equalization by adding air to body airspaces on the descent by breathing normally and adding air to the mask by breathing out of the nose or adding air to the ears and sinuses by equalization techniques; the corollary is also true on ascent, divers must release air from the body to maintain equalization. Buoyancy, or the ability to control whether a diver sinks or floats, is controlled by the buoyancy compensator (BCD). If a diver is ascending, the air in his BCD expands because of lower pressure according to Boyle’s law (decreasing the pressure of gases increases the volume). The expanding air increases the buoyancy of the diver, and she or he begins to ascend. The diver must vent air from the BCD or risk an uncontrolled ascent that could rupture the lungs. In descending, the increased pressure causes the air in the BCD to compress and the diver sinks much more quickly; the diver must add air to the BCD or risk an uncontrolled descent, facing much higher pressures near the ocean floor. The pressure also impacts how long a diver can stay underwater before ascending. The deeper a diver dives, the more compressed the air that is breathed because of increased pressure: If a diver dives 33 feet, the pressure is 2 ATA and the air would be compressed to one-half of its original volume. The diver uses up available air twice as fast as at the surface. |
Many deleterious alleles have such severe effects that a homozygous embryo spontaneously aborts long before what? | LIfe | baby | couple | birth | |
What kind of reaction, in general, keeps stars shining? | evolution | magnetism | fission | fusion | The energy from fusion reactions keeps the star shining. |
What is the most important factor determining soil type? | ecology | landscape | plant life | climate | Formed when elements either gain or lose electrons. |
What are the structural and functional units of the kidney called? | aeons | Ions | caldrons | nephrons | Each kidney has more than a million nephrons, which are the structural and functional units of the kidney. Each nephron is like a tiny filtering plant. |
What structure, containing many internal membranes, is the site of photosynthesis? | genome | ribosome | mitochondria | chloroplast | The chloroplast is the site of photosynthesis. Part of the photosynthesis reactions occur in an internal membrane within the organelle. The chloroplast contains many of these internal membranes, making photosynthesis very efficient. These internal membranes stack on top of each other, just like a stack of pancakes. |
During the day, what type of energy is transferred from the air over the land to the air over the water? | nuclear | magnetic | atmospheric | thermal | A: During the day, thermal energy is transferred from the air over the land to the air over the water. During the night, thermal energy is transferred in the opposite direction. |
Which nerve carries electrical signals from the rods and cones to the brain? | axon | auditory | neurotransmitter | optic | The optic nerve carries electrical signals from the rods and cones to the brain. |
What is the only thing that can change an asteroid? | a situation | weather | a wind | a collision | An asteroid can only change due to a collision. A collision may cause the asteroid to break up. It may create craters on the asteroid’s surface. An asteroid may strike a planet if it comes near enough to be pulled in by its gravity. |
Radon is inert and generally unreactive because it is which kind of gas? | ideal gas | ignoble gas | transitive gas | noble gas | Because radon is a noble gas, it is inert and generally unreactive. Despite this, exposure to even low concentrations of radon in air is quite dangerous. Describe the physical consequences of exposure to radon gas. Why are people who smoke more susceptible to these effects?. |
What are the two ways animals can manage their internal environment? | adaptation or mutation | digestion or excretion | sweating or sleeping | regulating or conforming | |
What may the jointed appendages of arthropods be used for? | digging | jumping | crawling | walking | The jointed appendages of arthropods may be used as legs for walking. Being jointed makes them more flexible. Try walking or climbing stairs without bending your knees, and you’ll see why joints are helpful. In most arthropods, the appendages on the head have been modified for other functions. Figure below shows some of the head appendages found in arthropods. Sensory organs such as eyes are also found on the head. |
A sperm cell and an egg cell fuse to become what? | unfertilized egg | embryo | fetus | fertilized egg | The Neural Tube To begin, a sperm cell and an egg cell fuse to become a fertilized egg. The fertilized egg cell, or zygote, starts dividing to generate the cells that make up an entire organism. Sixteen days after fertilization, the developing embryo’s cells belong to one of three germ layers that give rise to the different tissues in the body. The endoderm, or inner tissue, is responsible for generating the lining tissues of various spaces within the body, such as the mucosae of the digestive and respiratory systems. The mesoderm, or middle tissue, gives rise to most of the muscle and connective tissues. Finally the ectoderm, or outer tissue, develops into the integumentary system (the skin) and the nervous system. It is probably not difficult to see that the outer tissue of the embryo becomes the outer covering of the body. But how is it responsible for the nervous system? As the embryo develops, a portion of the ectoderm differentiates into a specialized region of neuroectoderm, which is the precursor for the tissue of the nervous system. Molecular signals induce cells in this region to differentiate into the neuroepithelium, forming a neural plate. The cells then begin to change shape, causing the tissue to buckle and fold inward (Figure 13.2). A neural groove forms, visible as a line along the dorsal surface of the embryo. The ridge-like edge on either side of the neural groove is referred as the neural fold. As the neural folds come together and converge, the underlying structure forms into a tube just beneath the ectoderm called the neural tube. Cells from the neural folds then separate from the ectoderm to form a cluster of cells referred to as the neural crest, which runs lateral to the neural tube. The neural crest migrates away from the nascent, or embryonic, central nervous system (CNS) that will form along the neural groove and develops into several parts of the peripheral nervous system (PNS), including the enteric nervous tissue. Many tissues that are not part of the nervous system also arise from the neural crest, such as craniofacial cartilage and bone, and melanocytes. |
The muscles in arteries and veins that are largely responsible for regulation of blood pressure are known as what type? | elongated muscles | opposing muscles | vascular muscles | smooth muscles | Smooth muscles in arteries and veins are largely responsible for regulation of blood pressure. |
An inversion may result when what kind of mass moves over cold ground? | cold air | warm water | cold water | warm air | When a new air mass moves over a region it brings its characteristics to the region. This may change the area's temperature and humidity. Moving air masses cause the weather to change when they contact different conditions. For example, a warm air mass moving over cold ground may cause an inversion. |
The eardrum is part of what part of the ear? | inner | main | thin | outer | The outer ear includes the pinna, ear canal, and eardrum. |
What is never lost and just changes forms? | fuel | life | food | energy | This platform is about to change energy from potential to kinetic. The energy is not lost; it just changes forms. The is on top of a precipice. The rest of the ride runs on the potential energy the platform has when it is at the top. |
What is the term for a mixture that varies in its composition? | mixed composition | homogeneous | amorphous | heterogeneous | The rock in Figure above is an example of a heterogeneous mixture. A heterogeneous mixture varies in its composition. The black nuggets, for example, are not distributed evenly throughout the rock. |
What are the "building blocks" of proteins? | nucleic acids | hormones | enzymes | amino acids | Amino acids are the "building blocks" of proteins. There are 20 different common amino acids. The structural formula of the simplest amino acid, called glycine, is shown in Figure below . Other amino acids have a similar structure. The sequence of amino acids and the number of amino acid chains in a protein determine the protein’s shape. The shape of a protein, in turn, determines its function. Shapes may be very complex. You can learn more about the structure of proteins at the URL below. |
What is responsible for our sense of balance? | our feet | our eyes | our limbs | our ears | The ears are also responsible for the sense of balance. Balance is the ability to sense and maintain body position. The semicircular canals inside the ear (see Figure above ) contain fluid that moves when the head changes position. Tiny hairs lining the semicircular canals sense movement of the fluid. In response, they send nerve impulses to the vestibular nerve , which carries the impulses to the brain. The brain interprets the impulses and sends messages to the peripheral nervous system. This system maintains the body’s balance by triggering contractions of skeletal muscles as needed. |
What technology do scientists use to create models? | microscopes | calculators | patterns | computers | Scientists create models with computers. Computers can handle enormous amounts of data. This can more accurately represent the real situation. For example, Earth’s climate depends on an enormous number of factors. Climate models can predict how climate will change as certain gases are added to the atmosphere. To test how good a model is, scientists might start a test run at a time in the past. If the model can predict the present it is probably a good model. It is more likely to be accurate when predicting the future. |
What essential molecules can be harmful if ingested in large amounts, especially if they contain saturated fatty acids from animal foods? | hydrogen | oxygen | helium | lipids | Lipids provide the body with energy and serve other vital functions. One gram of lipids provides 9 Calories of energy. You need to eat small amounts of lipids for good health. However, large amounts can be harmful, especially if they contain saturated fatty acids from animal foods. |
What are two ways cnidarians are able to reproduce? | internally and externally | mitosis and meiosis | spawning and sexual | asexually and sexually | General Cnidarian Life Cycle. Cnidarians may reproduce both asexually and sexually. |
In what human organ system would you find live e. coli bacteria? | skeletal system | circulatory system | respiratory system | digestive system | E. coli bacteria are anaerobic bacteria that live in the human digestive tract. |
What carries blood away from the heart? | capillaries | veins | pores | arteries | Arteries carry blood away from the heart, while veins return blood to the heart. |
What is the most important characteristic of a homogeneous mixture? | nonreactive | very reactive | high density | uniform composition throughout | A homogeneous mixture is a mixture in which the composition is uniform throughout the mixture. The salt water described above is homogeneous because the dissolved salt is evenly distributed throughout the entire salt water sample. Often it is easy to confuse a homogeneous mixture with a pure substance because they are both uniform. The difference is that the composition of the substance is always the same. The amount of salt in the salt water can vary from one sample to another. All solutions would be considered homogeneous because the dissolved material is present in the same amount throughout the solution. |
The domain geometry for a molecule with four electron pairs is called what? | linear | bent | trigonal planar | tetrahedral | As for methane and ammonia, the domain geometry for a molecule with four electron pairs is tetrahedral. In the water molecule, two of the electron pairs are lone pairs rather than bonding pairs. The molecular geometry of the water molecule is bent. The H-O-H bond angle is 104.5°, which is smaller than the bond angle in NH 3 (see Figure below ). |
What is the gel-like material between the cell membrane and the nucleus called? | vacuole | ribosome | mucus | cytoplasm | Cytoplasm is one component of cells that is common to all cells. Cytoplasm is the gel-like material between the cell membrane and the nucleus. The cytoplasm plays an important role in a cell, serving as a "jelly" in which organelles are suspended and held together by the cell membrane. Though prokaryotic cells do not have organelles (though they do have ribosomes), they still have cytoplasm. It is within the cytoplasm that most cellular activities occur, including the many metabolic pathways that occur within organelles, such as photosynthesis and aerobic respiration. |
Like mammals and birds, and unlike other reptiles, crocodiles have how many chambers in their heart? | two | one | six | four | Like mammals and birds, and unlike other reptiles, crocodiles have a four-chambered heart. But, unlike mammals, blood with and without oxygen can be mixed. |
What is the phenomenon in which light and sound waves become circular at the point source of a barrier? | reflection | refraction | sonic wave | diffraction | When a series of straight waves strike an impenetrable barrier, the waves stop at the barrier. However, the last particle of the medium at the back corner of the barrier will create circular waves from that point, called the point source. This can be seen in the image below. This phenomenon is called diffraction , and it occurs in liquid, sound, and light waves. While the waves become circular waves at the point source, they continue as straight waves where the barrier does not interfere with the waves. |
What is the name of the relatively large gland in the neck that secretes thyroxin? | Pituitary | Pancreas | Thyroid | thyroid | The thyroid gland is a relatively large gland in the neck. Hormones secreted by the thyroid gland include thyroxin. Thyroxin increases the rate of metabolism in cells throughout the body. |
Amplification that occurs in which cells often requires signal transduction pathways involving second messengers? | catayst cells | axons | optic nerves | sensory receptor | |
As adults, amphibians are completely _______, meaning they feed on other animals. | omnivorous | herbivorous | monogamous | carnivorous | Amphibians are an important food source for animals such as birds, snakes, raccoons, and fish. Amphibians are also important predators. As larvae, they feed mainly on small aquatic animals such as water insects. They may also feed on algae. As adults, amphibians are completely carnivorous . They may catch and eat worms, snails, and insects, as the frog in Figure below is doing. Unlike other amphibians, caecilians are burrowers . They use their head to dig in the soil, and they feed on earthworms and other annelids. Caecilians can be found in moist soil near rivers and streams in tropical regions. |
Approximately how many billion years ago did our solar system begin? | nine billion | four billion | three billion | five billion | Our solar system began about 5 billion years ago. The Sun, planets, and other solar system objects all formed at about the same time. The leading hypothesis for how they formed is called the nebular hypothesis . |
A type of what organism causes ergot, a disease that impacts crops directly and has more devastating effects on animals? | virus | insects | bacteria | fungus | Plant Parasites and Pathogens The production of enough good-quality crops is essential to our existence. Plant diseases have ruined crops, bringing widespread famine. Most plant pathogens are fungi that cause tissue decay and eventual death of the host (Figure 13.25). In addition to destroying plant tissue directly, some plant pathogens spoil crops by producing potent toxins. Fungi are also responsible for food spoilage and the rotting of stored crops. For example, the fungus Claviceps purpurea causes ergot, a disease of cereal crops (especially of rye). Although the fungus reduces the yield of cereals, the effects of the ergot’s alkaloid toxins on humans and animals are of much greater significance: In animals, the disease is referred to as ergotism. The most common signs and symptoms are convulsions, hallucination, gangrene, and loss of milk in cattle. The active ingredient of ergot is lysergic acid, which is a precursor of the drug LSD. Smuts, rusts, and powdery or downy mildew are other examples of common fungal pathogens that affect crops. |
Plant-like protists are commonly called what? | seaweed | fungus | sponge | algae | Plant-like protists are commonly called algae (alga, singular) . Some algae consist of single cells. They are called diatoms. Other algae are multicellular. An example is seaweed. Seaweed called kelp can grow as large as trees. You can see both a diatom and kelp in Figure below . Algae are probably ancestors of plants. |
Which cell gives rise to all cells of the human body? | schwann stem cell | signaler stem cell | omnipoten stem cell | totipotent stem cell | ability to diversify at each step. The totipotent stem cell is the zygote, or fertilized egg. The totipotent (toti- = “all”) stem cell gives rise to all cells of the human body. The next level is the pluripotent stem cell, which gives rise to multiple types of cells of the body and some of the supporting fetal membranes. Beneath this level, the mesenchymal cell is a stem cell that develops only into types of connective tissue, including fibrous connective tissue, bone, cartilage, and blood, but not epithelium, muscle, and nervous tissue. One step lower on the hierarchy of stem cells is the hemopoietic stem cell, or hemocytoblast. All of the formed elements of blood originate from this specific type of cell. Hemopoiesis begins when the hemopoietic stem cell is exposed to appropriate chemical stimuli collectively called hemopoietic growth factors, which prompt it to divide and differentiate. One daughter cell remains a hemopoietic stem cell, allowing hemopoiesis to continue. The other daughter cell becomes either of two types of more specialized stem cells (Figure 18.4): • Lymphoid stem cells give rise to a class of leukocytes known as lymphocytes, which include the various T cells, B cells, and natural killer (NK) cells, all of which function in immunity. However, hemopoiesis of lymphocytes progresses somewhat differently from the process for the other formed elements. In brief, lymphoid stem cells quickly migrate from the bone marrow to lymphatic tissues, including the lymph nodes, spleen, and thymus, where their production and differentiation continues. B cells are so named since they mature in the bone marrow, while T cells mature in the thymus. • Myeloid stem cells give rise to all the other formed elements, including the erythrocytes; megakaryocytes that produce platelets; and a myeloblast lineage that gives rise to monocytes and three forms of granular leukocytes: neutrophils, eosinophils, and basophils. |
What term describes the long tube that connects the mouth to the anus? | lungs tract | metabolism tract | esophagus tract | gastrointestinal tract | The organs in Figure below make up the gastrointestinal (GI) tract. This is essentially a long tube that connects the mouth to the anus. Food enters the mouth and then passes through the rest of the GI tract. Food waste leaves the body through the anus. In adults, the GI tract is more than 9 meters (30 feet) long!. |
In some ways, a collection of gas molecules represents the simplest form of what? | protein | life | energy | matter | In some ways, a collection of gas molecules represents the simplest form of matter. Because the individual molecules are so far apart, they have only fleeting interactions with one another. In contrast, molecules that have clustered together to form a liquid or solid are constantly exerting forces on each other. In fact, it is only because of these attractive forces that molecular solids and liquids exist at all. In this lesson, we will look at some of the ways in which molecules and ions attract one another to form solids and liquids. |
Are vesicles larger or smaller than vacuoles? | wider | larger | narrower | smaller | Vesicles are much smaller than vacuoles and have a variety of functions. Some vesicles pinch off from the membranes of the endoplasmic reticulum and Golgi apparatus. These vesicles store and transport proteins and lipids. Other vesicles are used as chambers for biochemical reactions. |
The duodenum is the first and the shortest part of what, and is where most chemical digestion takes place? | stomach | rectum | large intestine | small intestine | The duodenum is the first part of the small intestine. It is also the shortest part. This is where most chemical digestion takes place. Many enzymes and other substances involved in digestion are secreted into the duodenum. |
Which system consists of all the bones of the body? | digestive system | circulatory system | nervous system | skeletal system | The skeletal system consists of all the bones of the body. How important are your bones?. |
What is rusting an example of? | contamination change | radiation change | Decomposition | chemical change | Comets carry materials in from the outer solar system. Comets may have brought water into the early Earth. Other substances could also have come from comets. |
What molecule consists of two atoms of hydrogen and one atom of oxygen? | air | carbon monoxide | hydrogen peroxide | water | Water is an example of a common chemical compound. As you can see in the Figure below , each water molecule consists of two atoms of hydrogen and one atom of oxygen. Water always has this 2:1 ratio of hydrogen to oxygen. Like water, all compounds consist of a fixed ratio of elements. It doesn’t matter how much or how little of a compound there is. It always has the same composition. |
All compounds, whether ionic or covalent, must be what? | metallic neutral | abnormal neutral | organic neutral | electrically neutral | When chemists synthesize a new compound, they may not yet know its molecular or structural formula. In such cases, they usually begin by determining itsempirical formula, the relative numbers of atoms of the elements in a compound, reduced to the smallest whole numbers. Because the empirical formula is based on experimental measurements of the numbers of atoms in a sample of the compound, it shows only the ratios of the numbers of the elements present. The difference betweenempirical and molecular formulas can be illustrated with butane, a covalent compound used as the fuel in disposable lighters. The molecular formula for butane is C4H10. The ratio of carbon atoms to hydrogen atoms in butane is 4:10, which can be reduced to 2:5. The empirical formula for butane is therefore C2H5. The formula unit is the absolutegrouping of atoms or ions represented by the empirical formula of a compound, either ionic or covalent. Butane, for example, has the empirical formula C2H5, but it contains two C2H5 formula units, giving a molecular formula of C4H10. Because ionic compounds do not contain discrete molecules, empirical formulas are used to indicate their compositions. All compounds, whether ionic or covalent, must be electrically neutral. Consequently, the positive and negative charges in a formula unit must exactly cancel each other. If the cation and the anion have charges of equal. |
Which is the most common sti (sexually transmitted infection) in the united states? | syphilis | AIDS | giardia | chlamydia | Chlamydia is the most common STI in the United States. As shown in the graph in Figure below , females are much more likely than males to develop chlamydia. Like most STIs, rates of chlamydia are highest in teens and young adults. |
What do all chemical reactions need to get started? | potential energy | expression energy | kinetic energy | activation energy | All chemical reactions, even exothermic reactions, need activation energy to get started. Activation energy is needed to bring reactants together so they can react. |
What organ does asthma periodically cause to narrow? | liver | ovaries | intestines | lungs | Asthma is a disease in which the air passages of the lungs periodically become too narrow, often with excessive mucus production. This causes difficulty breathing, coughing, and chest tightness. An asthma attack may be triggered by allergens, strenuous exercise, stress, or other factors. |
Silver, gold, and copper all conduct what very well? | microwaves | light | sound | electricity | The electrical conductivity of a substance is a property that depends only on the type of substance. Silver, gold, and copper are excellent conductors of electricity, while glass and plastic are poor conductors. A larger or smaller piece of glass will not change this property. An intensive property is a property of matter that depends only on the type of matter in a sample and not on the amount. Other intensive properties include color, temperature, density, and solubility. |
Pakicetus and rodhocetus are considered to be ancestors of modern what? | hominins | rodents | primates | whales | Pakicetus and Rodhocetus are considered to be ancestors of modern whales. Scientists still argue about how aquatic Pakicetus was, but Rodhocetus is considered to be a largely aquatic animal. Where is the nostril located on Pakicetus ?. |
Chemical and physical changes in a system may be accompanied by an increase or a decrease in the disorder of the system, corresponding to an increase or decrease in what? | volume | enthalpy | vibration | entropy | Chemical and physical changes in a system may be accompanied by either an increase or a decrease in the disorder of the system, corresponding to an increase in entropy (ΔS> 0) or a decrease in entropy (ΔS < 0), respectively. As with any other state function, the change in entropy is defined as the difference between the entropies of the final and initial states: ΔS = Sf − Si. When a gas expands into a vacuum, its entropy increases because the increased volume allows for greater atomic or molecular disorder. The greater the number of atoms or molecules in the gas, the greater the disorder. The magnitude of the entropy of a system depends on the number of microscopic states, or microstates, associated with it (in this case, the number of atoms or molecules); that is, the greater the number of microstates, the greater the entropy. We can illustrate the concepts of microstates and entropy using a deck of playing cards, as shown in Figure 18.7 "Illustrating Low- and High-Entropy States with a Deck of Playing Cards". In any new deck, the 52 cards are arranged by four suits, with each suit arranged in descending order. If the cards are shuffled, however, there are approximately 1068 different ways they might be arranged, which corresponds to 1068different microscopic states. The entropy of an ordered new deck of cards is therefore low, whereas the entropy of a randomly shuffled deck is high. Card games assign a higher value to a hand that has a low degree of disorder. In games such as five-card poker, only 4 of the 2,598,960 different possible hands, or microstates, contain the highly ordered and valued arrangement of cards called a royal flush, almost 1.1 million hands contain one pair, and more than 1.3 million hands are completely disordered and therefore have no value. Because the last two arrangements are far more probable than the first, the value of a poker hand is inversely proportional to its entropy. We can see how to calculate these kinds of probabilities for a chemical system by considering the possible arrangements of a sample of four gas molecules in a two-bulb container (Figure 18.8 "The Possible Microstates for a Sample of Four Gas Molecules in Two Bulbs of Equal Volume"). There are five possible arrangements: all four molecules in the left bulb (I); three molecules in the left bulb and one in the right bulb (II); two molecules in each bulb (III); one molecule in the left bulb and three molecules in the right bulb (IV); and four molecules in the right bulb (V). If we assign a different color to each molecule to keep track of it for this discussion (remember, however, that in reality the molecules are indistinguishable from one another), we can see that there are 16 different ways the four molecules can be distributed in the bulbs, each corresponding to a particular microstate. As shown in Figure 18.8 "The Possible Microstates. |
What is the only way to completely avoid stis? | contraceptive use | cover your mouth | oral sex | avoid sexual contact | The only completely effective way to prevent infection with STIs is to avoid sexual contact and other risky behaviors. Using condoms can lower the risk of becoming infected with STIs during some types of sexual activity. However, condoms are not foolproof. Pathogens may be present on areas of the body not covered by condoms. Condoms can also break or be used incorrectly. |
What is an ion that is in common to both salts in a solution? | native ion | regular ion | strong ion | common ion | This situation describes the common ion effect. A common ion is an ion that is in common to both salts in a solution. In the above example, the common ion is Ca 2+ . The common ion effect is a decrease in the solubility of an ionic compound as a result of the addition of a common ion. Adding calcium ion to the saturated solution of calcium sulfate causes additional CaSO 4 to precipitate from the solution, lowering its solubility. The addition of a solution containing sulfate ion, such as potassium sulfate, would result in the same common ion effect. |
Prokaryotes and the nitrogen cycle nitrogen is a very important element for life because it is part of proteins and this? | molecules | nuclear forces | nerve cells | nucleic acids | Prokaryotes and the Nitrogen Cycle Nitrogen is a very important element for life because it is part of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds to ammonia, ammonium ions, nitrate, nitrite, and nitrogen gas by myriad processes, many of which are carried out only by prokaryotes. As illustrated in Figure 22.19, prokaryotes are key to the nitrogen cycle. The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen from the air, but this nitrogen is not usable by plants, which are primary producers. Gaseous nitrogen is transformed, or “fixed” into more readily available forms such as ammonia through the process of nitrogen fixation. Ammonia can be used by plants or converted to other forms. Another source of ammonia is ammonification, the process by which ammonia is released during the decomposition of nitrogen-containing organic compounds. Ammonia released to the atmosphere, however, represents only 15 percent of the total nitrogen released; the rest is as N2 and N2O. Ammonia is catabolized anaerobically by some prokaryotes, yielding N2 as the final product. Nitrification is the conversion of ammonium to nitrite and nitrate. Nitrification in soils is carried out by bacteria belonging to the genera Nitrosomas, Nitrobacter, and Nitrospira. The bacteria performs the reverse process, the reduction of nitrate from the soils to gaseous compounds such as N2O, NO, and N2, a process called denitrification. |
What property is a measure of the average kinetic energy of molecules? | density | mass | velocity | temperature | Temperature is a measure of the average kinetic energy of molecules. Consider a mixture of hydrogen and oxygen gas at a certain temperature. Use the formula for kinetic energy to explain why the hydrogen molecules move faster than the oxygen molecules. Then explain why there’s no hydrogen in the earth’s atmosphere, and why the moon has no atmosphere at all. |
A measure of the disorder of a system is called its what? | function | lose | spectral | entropy | Summary A measure of the disorder of a system is its entropy (S), a state function whose value increases with an increase in the number of available microstates. Areversible process is one for which all intermediate states between extremes are equilibrium states; it can change direction at any time. In contrast, anirreversible process occurs in one direction only. The change in entropy of the system or the surroundings is the quantity of heat transferred divided by the temperature. The second law of thermodynamics states that in a reversible process, the entropy of the universe is constant, whereas in an irreversible process, such as the transfer of heat from a hot object to a cold object, the entropy of the universe increases. |
What influence does the horizontal motion of a projectile have on free fall? | increase acceleration | decrease acceleration | vertical | none | The horizontal motion of a projectile does not influence its free fall. |
Larger animals expend more of what to achieve locomotion? | time | neurons | distance | energy | |
Subshells are subdivisions of what groupings of electrons that can be found surrounding atoms? | isotopes | globals | analogous | orbitals | Carbon (atomic number 6) has six electrons. Four of them fill the 1s and 2s orbitals. The remaining two electrons occupy the 2p subshell. We now have a choice of filling one of the 2p orbitals and pairing the electrons or of leaving the electrons unpaired in two different, but degenerate, p orbitals. The orbitals are filled as described by Hund’s rule: the lowest-energy configuration for an atom with electrons within a set of degenerate orbitals is that having the maximum number of unpaired electrons. Thus, the two electrons in the carbon 2p orbitals have identical n, l, and ms quantum numbers and differ in their ml quantum number (in accord with the Pauli exclusion principle). The electron configuration and orbital diagram for carbon are:. |
The number of moles of solute in 1 kg of solvent is defined as what? | kilocalorie | singularity | pollenation | molarity | An alternative way to define the concentration of a solution is molality, abbreviated m. Molality is defined as the number of moles of solute in 1 kg of solvent. How is this different from molarity? Would you expect a 1 M solution of sucrose to be more or less concentrated than a 1 m solution of sucrose? Explain your answer. What are the advantages of using solutions for quantitative calculations?. |
What is the name for the pores in leaves that allow a plant to retain water or exchange gases? | rhizomes | neurons | chloroplasts | stomata | To allow the plant to retain water and exchange gases, small pores (holes) in the leaves called stomata also evolved ( Figure below ). The stomata can open and close depending on weather conditions. When it's hot and dry, the stomata close to keep water inside of the plant. When the weather cools down, the stomata can open again to let carbon dioxide in and oxygen out. |
What is part of a cycle that holds an element or water for a long period of time called? | a holding tank | homeostasis | a ditch | a reservoir | Part of a cycle that holds an element or water for a long period of time is called a reservoir . The ocean is a reservoir for water. The deep ocean may hold water for thousands of years. |
What theory states that all organisms are made up of one or more cells? | the micro theory | the molecular anatomy theory | the atomic theory | the cell theory | According to the cell theory, all organisms are made up of one or more cells. Cells are the sites where all life processes take place. Cells come only from pre-existing cells. New cells forms when existing cells divide. |
What does rearrangements of chromosomes contribute to the emergence of? | fewer species | clones | extinction | new species | |
In the universe as a whole, what is the most common element? | oxygen | helium | carbon | hydrogen | Abundance The elements vary widely in abundance. In the universe as a whole, the most common element is hydrogen (about 90% of atoms), followed by helium (most of the remaining 10%). All other elements are present in relatively minuscule amounts, as far as we can detect. On the planet Earth, however, the situation is rather different. Oxygen makes up 46.1% of the mass of Earth’s crust (the relatively thin layer of rock forming Earth’s surface), mostly in combination with other elements, while silicon makes up 28.5%. Hydrogen, the most abundant element in the universe, makes up only 0.14% of Earth’s crust. Table 2.1 "Elemental Composition of Earth" lists the relative abundances of elements on Earth as a whole and in Earth’s crust. Table 2.2 "Elemental Composition of a Human Body" lists the relative abundances of elements in the human body. If you compare Table 2.1 "Elemental Composition of Earth" and Table 2.2 "Elemental Composition of a Human Body", you will find disparities between the percentage of each element in the human body and on Earth. Oxygen has the highest percentage in both Saylor URL: http://www. saylor. org/books. |
What are substances that cannot be broken down into simpler substances with different properties called? | molecules | atoms | compounds | elements | Elements are substances that cannot be broken down into simpler substances with different properties. |
What gas, that is dissolved in solution, is used in carbonated beverages? | hydrogen peroxide | phosphorus dioxide | carbon monoxide | carbon dioxide | Carbonated beverages contain carbon dioxide gas that is dissolved in solution. Do you think a carbonated beverage is a mixture or a pure substance? Explain. |
Fluoride ion is widely used in water supplies to help prevent what? | chlorine taste | rust | bacteria | tooth decay | Fluoride ion is widely used in water supplies to help prevent tooth decay. Chloride is an important component in ion balance in blood. Iodide ion is needed by the thyroid gland to make the hormone thyroxine. |
Amino acids are joined together to form a chain at what molecular structure? | DNA | chloroplasts | chromosomes | ribosomes | At the ribosome, the amino acids are joined together to form a chain of amino acids. |
What is the name of the science that studies matter and the changes material substances undergo? | biology | geology | physics | chemistry | Summary Chemistry is the study of matter and the changes material substances undergo. It is essential for understanding much of the natural world and central to many other scientific disciplines, including astronomy, geology, paleontology, biology, and medicine. |
Which process changes rocks by heat and pressure? | weathering | sediments | Changes | metamorphism | Metamorphism changes rocks by heat and pressure. These agents create an entirely new type of rock. Metamorphism changes rocks physically and/or chemically. |
What is defined as an antigen that causes an allergy? | a pollutant | an expectorant | a disinfectant | an allergen | An antigen that causes an allergy is called an allergen. |
What can be linked together to form disaccharides or polysaccharides? | nitrates | amino acids | carbohydrates | monosaccharides | Monosaccharides can be linked together to form disaccharides or polysaccharides. |
What were the first living things to evolve on earth? | DNA | eukaryotes | carbon | prokaryotes | Prokaryotes were the first living things to evolve on Earth, probably around 3.8 billion years ago. They were the only living things until the first eukaryotic cells evolved about 2 billion years ago. Prokaryotes are still the most numerous organisms on Earth. |
All members of a species living together form a what? | organization | family | group | population | Recall that the four different sublevels (s, p, d, and f) each consist of a different number of orbitals. The s sublevel has one orbital, the p sublevel has three orbitals, the d sublevel has five orbitals, and the f sublevel has seven orbitals. In the first period, only the 1s sublevel is being filled. Since all orbitals can hold two electrons, the entire first period consists of just two elements. In the second period, the 2s sublevel, with two electrons, and the 2p sublevel, with six electrons, are being filled. Consequently, the second period contains eight elements. The third period is similar to the second, except the 3s and 3p sublevels are being filled. Because the 3d sublevel does not fill until after the 4s sublevel, the fourth period contains 18 elements, due to the 10 additional electrons that can be accommodated by the 3d orbitals. The fifth period is similar to the fourth. After the 6s sublevel fills, the 4f sublevel is populated with up to 14 electrons. This is followed by the 5d and the 6p sublevels. The total number of elements in the sixth period is 32. The seventh period also contains 32 elements, most of which are too unstable to be found in nature. All 32 have been detected or synthesized, although for some of the later elements in this period, only a handful of atoms have ever been made. |
What type of disturbance do even dominant plants depend on in many biomes? | seismic force | mass extinction | radiation | periodic | |
What type of behaviors are triggered by pheromones in moths? | peculiar | exhibit | illuminating | courtship | |
What do organisms use to store energy? | metabolytes | tissues | proteins | lipids | A lipid is an organic compound such as fat or oil. Organisms use lipids to store energy, but lipids have other important roles as well. Lipids consist of repeating units called fatty acids. Fatty acids are organic compounds that have the general formula CH 3 (CH 2 ) n COOH, where n usually ranges from 2 to 28 and is always an even number. There are two types of fatty acids: saturated fatty acids and unsaturated fatty acids. |
The scientific practice of classifying organisms is also known as what? | methodology | taxodermy | terminology | taxonomy | 22 Classification of Living Things 22.0.1 Classification of Living Things & Naming With so many flora and fauna on planet Earth, there must be a method to classify each organism to distinguish it from others so it can be correctly identified. Classification does not only apply to biology. For example, supermarkets and grocery stores organise their products by classifying them. Beverages may occupy one aisle, while cleaning supplies may occupy another. In science, the practice of classifying organisms is called taxonomy (Taxis means arrangement and nomos means law). The modern taxonomic system was developed by the Swedish botanist Carolus (Carl) Linneaeus (1707-1788). He used simple physical characteristics of organisms to identify and differentiate between different species. Linneaeus developed a hierarchy of groups for taxonomy. To distinguish different levels of similarity, each classifying group, called taxon (pl. taxa) is subdivided into other groups. To remember the order, it is helpful to use a mnemonic device. The taxa in hierarchical order: • • • • • • • •. |
What is the type of cell division that produces gametes? | budding | electrolysis | mitosis | meiosis | Meiosis is the type of cell division that produces gametes. |
The force applied to an object is called? | strain | gravity | torque | stress | Stress is the force applied to an object. Stresses can be confining, compression, tension, or shear. |
What is the largest mineral group, comprising over 90% of earth's crust? | soils | oxides | carbonates | silicates | Silicates are the largest mineral group. About 1,000 silicate minerals are known. Silicate minerals are also extremely common. They make up over 90% of Earth's crust!. |
Sound navigation and ranging is an acronym for what, which is used to locate underwater objects such as submarines? | radar | sound transmission | GPS | sonar | Sonar stands for sound navigation and ranging. It is used to locate underwater objects such as submarines. |
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