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When do the eggs in a female's ovaries start to mature? Here are the choices: A. puberty B. adolescence C. maturity D. adulthood	At birth, a female’s ovaries contain all the eggs she will ever produce. However, the eggs do not start to mature until she enters puberty. After menarche, one egg typically matures each month until a woman reaches middle adulthood.	A: puberty.
Drilling wells into hot rocks to release hot water or steam is an example of what kind of power plant? Here are the choices: A. hydroelectric B. fossil fuel C. geothermal D. solar	At a geothermal power plant, engineers drill wells into the hot rocks. Hot water or steam may come up through the wells. Alternatively, water may be put down into the well to be heated. It then comes up. The hot water or steam makes a turbine spin. This makes electricity. Pictured below is an example of a geothermal power plant ( Figure below ).	C: geothermal.
What is the state of matter that resembles a gas but has certain properties that a gas does not have called? Here are the choices: A. plasma B. solid C. liquid D. fluid	You’re probably less familiar with plasmas than with solids, liquids, and gases. Yet, most of the universe consists of plasma. Plasma is a state of matter that resembles a gas but has certain properties that a gas does not have. Like a gas, plasma lacks a fixed volume and shape. Unlike a gas, plasma can conduct electricity and respond to magnetism. That’s because plasma contains charged particles called ions. This gives plasma other interesting properties. For example, it glows with light.	A: plasma.
What enthalpy change is observed in an exothermic reaction? Here are the choices: A. negative B. positive C. entropy D. no change	The reaction is exothermic and thus the sign of the enthalpy change is negative.	A: negative.
What does hypoxic mean? Here are the choices: A. higher oxygen B. low oxygen C. standard oxygen level D. Oxygen rate	The pond on the left is covered with algae because there is too much nitrogen in the water. The red-shaded area in the map on the right is a dead zone in the Gulf of Mexico. It’s called the hypoxic (“low oxygen”) zone in the figure.	B: low oxygen.
Who has proposed that cigarette advertising in all media be banned entirely? Here are the choices: A. teachers B. parents C. antismoking groups D. schools		C: antismoking groups.
What is the reaction called when an acid and a base react? Here are the choices: A. activation B. oxidation C. decomposition D. neutralization	When an acid and a base react, the reaction is called a neutralization reaction . That’s because the reaction produces neutral products. Water is always one product, and a salt is also produced. A salt is a neutral ionic compound. You can learn more about salts and how they form at this URL: http://www. youtube. com/watch?v=zjIVJh4JLNo .	D: neutralization.
What is the term for when clumped solids sink to the bottom of the water? Here are the choices: A. Foundation B. Clumping C. sediment D. sedimentation	The water is moved to tanks. The clumped solids sink to the bottom of the water. This is called sedimentation .	D: sedimentation.
A wildfire clears a forest of vegetation and animal life, returning their nutrients to the ground leaving a foundation for rapid recolonization. what is this a classic example of? Here are the choices: A. secondary succession B. primary succession C. typical succession D. cause succession	Secondary succession A classic example of secondary succession occurs in oak and hickory forests cleared by wildfire (Figure 19.27). Wildfires will burn most vegetation, and unless the animals can flee the area, they are killed. Their nutrients, however, are returned to the ground in the form of ash. Thus, although the community has been dramatically altered, there is a soil ecosystem present that provides a foundation for rapid recolonization. Before the fire, the vegetation was dominated by tall trees with access to the major plant energy resource: sunlight. Their height gave them access to sunlight while also shading the ground and other low-lying species. After the fire, though, these trees are no longer dominant. Thus, the first plants to grow back are usually annual plants followed within a few years by quickly growing and spreading grasses and other pioneer species. Due, at least in part, to changes in the environment brought on by the growth of grasses and forbs, over many years, shrubs emerge along with small pine, oak, and hickory trees. These organisms are called intermediate species. Eventually, over 150 years, the forest will reach its equilibrium point and resemble the community before the fire. This equilibrium state is referred to as the climax community, which will remain until the next disturbance. The climax community is typically characteristic of a given climate and geology. Although the community in equilibrium looks the same once it is attained, the equilibrium is a dynamic one with constant changes in abundance and sometimes species identities. The return of a natural ecosystem after agricultural activities is also a well-documented secondary succession process.	A: secondary succession.
What system of the body can specifically protect you from pathogens and other things that might make you ill? Here are the choices: A. immune B. cardiovascular C. digestion D. muscle	The immune system usually protects you from pathogens and other causes of disease. When the immune system is working properly, it keeps you from getting sick. But the immune system is like any other system of the body. It can break down or develop diseases.	A: immune.
During glycolysis, each glucose molecule is broken down into two molecules of what compound? Here are the choices: A. sugar B. cellulose C. chlorophyll D. pyruvate		D: pyruvate.
The single circular dna chromosome of bacteria is not enclosed in what, but instead occupies a specific location called the nucleoid within the cell? Here are the choices: A. protons B. nucleus C. molecules D. atom	Binary Fission Due to the relative simplicity of the prokaryotes, the cell division process, called binary fission, is a less complicated and much more rapid process than cell division in eukaryotes. The single, circular DNA chromosome of bacteria is not enclosed in a nucleus, but instead occupies a specific location, the nucleoid, within the cell (Figure 10.2). Although the DNA of the nucleoid is associated with proteins that aid in packaging the molecule into a compact size, there are no histone proteins and thus no nucleosomes in prokaryotes. The packing proteins of bacteria are, however, related to the cohesin and condensin proteins involved in the chromosome compaction of eukaryotes. The bacterial chromosome is attached to the plasma membrane at about the midpoint of the cell. The starting point of replication, the origin, is close to the binding site of the chromosome to the plasma membrane (Figure 10.15). Replication of the DNA is bidirectional, moving away from the origin on both strands of the loop simultaneously. As the new double strands are formed, each origin point moves away from the cell wall attachment toward the opposite ends of the cell. As the cell elongates, the growing membrane aids in the transport of the chromosomes. After the chromosomes have cleared the midpoint of the elongated cell, cytoplasmic separation begins. The formation of a ring composed of repeating units of a protein called FtsZ directs the partition between the nucleoids. Formation of the FtsZ ring triggers the accumulation of other proteins that work together to recruit new membrane and cell wall materials to the site. A septum is formed between the nucleoids, extending gradually from the periphery toward the center of the cell. When the new cell walls are in place, the daughter cells separate.	B: nucleus.
Plaque is surgically removed from the walls of a vessel in which surgery? Here are the choices: A. endarterectomy B. arthroscopy C. lumpectomy D. discectomy	whereas atherosclerosis is a more specific term for the build-up of plaque in the walls of the vessel and is a specific type of arteriosclerosis. There is also a distinct genetic component, and pre-existing hypertension and/or diabetes also greatly increase the risk. However, obesity, poor nutrition, lack of physical activity, and tobacco use all are major risk factors. Treatment includes lifestyle changes, such as weight loss, smoking cessation, regular exercise, and adoption of a diet low in sodium and saturated fats. Medications to reduce cholesterol and blood pressure may be prescribed. For blocked coronary arteries, surgery is warranted. In angioplasty, a catheter is inserted into the vessel at the point of narrowing, and a second catheter with a balloon-like tip is inflated to widen the opening. To prevent subsequent collapse of the vessel, a small mesh tube called a stent is often inserted. In an endarterectomy, plaque is surgically removed from the walls of a vessel. This operation is typically performed on the carotid arteries of the neck, which are a prime source of oxygenated blood for the brain. In a coronary bypass procedure, a non-vital superficial vessel from another part of the body (often the great saphenous vein) or a synthetic vessel is inserted to create a path around the blocked area of a coronary artery.	A: endarterectomy.
Where does most of the earth's energy come from? Here are the choices: A. sun B. its core C. magnetic field D. its atmosphere	Give an example of how matter cycles. While matter cycles round and round in the Earth System, ENERGY FLOWS through the Earth System. The vast majority of Earth’s energy comes from the sun, flows into the Earth’s System, and flows out of the Earth’s System into space. If all the energy that comes to Earth from the sun were to stay on Earth, the Earth would melt away. But the energy that comes to Earth from the sun does not stay. Eventually it radiates back out to space as heat. We know this because the average temperature of the Earth has remained relatively constant. If the energy from the sun were to stay on Earth, the Earth’s average temperature would rise. Some of the sun’s energy is reflected by the atmosphere, some is absorbed by the Earth and re-radiated as heat, some evaporates water and powers the water cycle, some is captured by plants and used to make sugars, and some powers the wind but eventually ALL of the energy that comes to the Earth from the sun leaves the Earth and flows into space. For this reason we say that energy flows through the Earth System.	A: sun.
What is the primary energy source for cells? Here are the choices: A. sucrose B. glycogen C. glucose D. protein	Figure 8.5 The basic equation for photosynthesis is deceptively simple. In reality, the process takes place in many steps involving intermediate reactants and products. Glucose, the primary energy source in cells, is made from two three-carbon GA3Ps.	C: glucose.
What is a simple sugar such as fructose or glucose? Here are the choices: A. disaccharide B. galactose C. polysaccharides D. monosaccharide	A monosaccharide is a simple sugar such as fructose or glucose. Fructose is found in fruits, whereas glucose generally results from the digestion of other carbohydrates. Glucose is used for energy by the cells of most organisms.	D: monosaccharide.
Gram-negative bacteria have a cell wall made of peptidoglycan, whereas gram-positive bacteria have a cell wall made of what? Here are the choices: A. hydrolic acid B. lipoteichoic acid C. choanocyte acid D. solmization acid	Gram-negative bacteria have a cell wall made of peptidoglycan, whereas Gram-positive bacteria have a cell wall made of lipoteichoic acid. Figure 22.19 Which of the following statements about the nitrogen cycle is false? a. Nitrogen fixing bacteria exist on the root nodules of legumes and in the soil. Denitrifying bacteria convert nitrates (NO3-) into nitrogen gas (N2). Ammonification is the process by which ammonium ion (NH4+) is released from decomposing organic compounds. Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+).	B: lipoteichoic acid.
What term is used to describe muscle fibers that allows muscles to contract? Here are the choices: A. organelle B. organisms C. ligaments D. fluorescence	organelle in muscle fibers that allows muscles to contract.	A: organelle.
What are the main organs for breathing in a mammal? Here are the choices: A. nostrils B. gills C. intestines D. lungs	All mammals have lungs that are the main organs for breathing. Lung capacity has evolved to support the animal’s activities. During inhalation, the lungs expand with air, and oxygen diffuses across the lung’s surface and enters the bloodstream. During exhalation, the lungs expel air and lung volume decreases. In the next few sections, the process of human breathing will be explained.	D: lungs.
What class of animals have four limbs and produce amniotic eggs? Here are the choices: A. mammals B. reptiles C. insects D. amphibians	Mammals are a class of endothermic vertebrates. They have four limbs and produce amniotic eggs. The mammal class is defined by the presence of mammary glands and hair (or fur). Other traits of mammals include sweat glands in their skin, alveoli in their lungs, a four-chambered heart, and a brain covering called the neocortex.	A: mammals.
No chemical process on the planet can match the output of what process? Here are the choices: A. photosynthesis B. pollination C. glycolysis D. sexual reproduction		A: photosynthesis.
Which disease afflicts children who don't get enough calcium during their bone formation stage? Here are the choices: A. cancer B. sids C. rabies D. rickets	A: Children who don’t get enough calcium while their bones are forming may develop a deficiency disease called rickets, in which their bones are softer than normal and become bent and stunted. Adults who don’t get enough calcium may develop a condition called osteoporosis, in which the bones lose calcium and become weak and brittle. People with osteoporosis are at high risk of bone fractures.	D: rickets.
What kind of reactions between an acid and a base yield a salt and water? Here are the choices: A. neutralization B. distillation C. evaporation D. oxidation	Neutralization reactions between an acid and a base yield a salt and water. In some cases, this results in a completely neutral solution. However, some salts are weakly acidic or basic. How can we tell whether a given salt will act as an acid or base? Looking at the relative strengths of the acid and base that were used to form the salt can give us information on the acid-base properties of the resulting solution.	A: neutralization.
What human bodily function does cellulose help with? Here are the choices: A. moves food wastes B. reproduction C. sleep D. stops food wastes	Cellulose is another complex carbohydrate that is a polymer of glucose. However, glucose molecules are bonded together differently in cellulose than they are in starches. Cellulose molecules bundle together to form long, tough fibers, as you can see in the Figure below . Have you ever eaten raw celery? If you have, then you probably noticed that the stalks contain long, stringy fibers. The fibers are mostly cellulose. Cellulose is the most abundant biochemical compound. It makes up the cell walls of plants and gives support to stems and tree trunks. Cellulose also provides needed fiber in the human diet. We can’t digest cellulose, but it helps keep food wastes moving through the digestive tract.	A: moves food wastes.
What are large vesicles derived from the endoplasmic reticulum and golgi apparatus? Here are the choices: A. chloroplasts B. tubules C. alleles D. vacuoles		D: vacuoles.
The burning of charcoal is what type of reaction? Here are the choices: A. physical B. combustion C. condensation D. evaporation	Serge Melki (Flickr:Serge Melki). The burning of charcoal is a combustion reaction . CC BY 2.0.	B: combustion.
What is responsible for the physical changes of puberty? Here are the choices: A. caffeine B. testosterone C. nicotine D. adrenaline	CHAPTER REVIEW 27.1 Anatomy and Physiology of the Male Reproductive System Gametes are the reproductive cells that combine to form offspring. Organs called gonads produce the gametes, along with the hormones that regulate human reproduction. The male gametes are called sperm. Spermatogenesis, the production of sperm, occurs within the seminiferous tubules that make up most of the testis. The scrotum is the muscular sac that holds the testes outside of the body cavity. Spermatogenesis begins with mitotic division of spermatogonia (stem cells) to produce primary spermatocytes that undergo the two divisions of meiosis to become secondary spermatocytes, then the haploid spermatids. During spermiogenesis, spermatids are transformed into spermatozoa (formed sperm). Upon release from the seminiferous tubules, sperm are moved to the epididymis where they continue to mature. During ejaculation, sperm exit the epididymis through the ductus deferens, a duct in the spermatic cord that leaves the scrotum. The ampulla of the ductus deferens meets the seminal vesicle, a gland that contributes fructose and proteins, at the ejaculatory duct. The fluid continues through the prostatic urethra, where secretions from the prostate are added to form semen. These secretions help the sperm to travel through the urethra and into the female reproductive tract. Secretions from the bulbourethral glands protect sperm and cleanse and lubricate the penile (spongy) urethra. The penis is the male organ of copulation. Columns of erectile tissue called the corpora cavernosa and corpus spongiosum fill with blood when sexual arousal activates vasodilatation in the blood vessels of the penis. Testosterone regulates and maintains the sex organs and sex drive, and induces the physical changes of puberty. Interplay between the testes and the endocrine system precisely control the production of testosterone with a negative feedback loop.	B: testosterone.
Unlike prokaryotes, eukaryotes have what? Here are the choices: A. golgi apparatus B. cell wall C. cell membrane D. cell nucleus	Eukaryotes evolved about 2 billion years ago. Unlike prokaryotes, eukaryotes have a cell nucleus. They have more structures and are better organized. Organelles within a eukaryote can perform certain functions. Some supply energy; some break down wastes. Eukaryotes were better able to live and so became the dominant life form.	D: cell nucleus.
An electron is accelerated from rest through a potential difference of what? Here are the choices: A. watts B. volts C. joules D. amperes	An electron is accelerated from rest through a potential difference of volts. It then enters a region traveling perpendicular to a magnetic field of . Calculate the velocity of the electron.	B: volts.
What is the most commonly used source of energy in the world? Here are the choices: A. wind B. electricity C. water D. oil	Oil is a thick, dark brown or black liquid. It is found in rock layers of the Earth's crust. Oil is currently the most commonly used source of energy in the world.	D: oil.
Silk and cotton are examples of what type of fibers? Here are the choices: A. natural B. mechanical C. coral D. artificial	Many of the fibers that compose the materials for our clothes are naturally occurring. Silk and cotton are examples of natural fibers. Silk is produced by the silkworm, and cotton is grown as a plant. However, several chemical processes are used to treat silk thread so that it is shrink-resistant and will repel water. Chemical dyes are frequently used to color various fabrics. Cleaning requires special soaps or chemicals used to dry-clean materials. Cotton will grow better if the boll weevil (an insect that kills the plant) is eliminated with the use of specific insecticides. Ironing of cotton is made easier by the use of chemicals that produce a permanent press in the material.	A: natural.
Tuna have been shown to contain high levels of what metal? Here are the choices: A. mercury B. titanium C. cadmium D. iron	The higher up a food chain that humans eat, the greater the levels of toxic metals they take in. That’s why people should avoid eating too much of large fish such as tuna. Tuna are predators near the top of their food chains. They have been shown to contain high levels of mercury. In people, heavy metals can damage the brain and other organs. Unborn babies and young children are most affected. That’s because their organs are still developing.	A: mercury.
What does the esophagus produce for lubrication? Here are the choices: A. phloem B. mucous C. synovial fluid D. bile	animal diet needs carbohydrates, protein, and fat, as well as vitamins and inorganic components for nutritional balance. How each of these components is digested is discussed in the following sections. Carbohydrates The digestion of carbohydrates begins in the mouth. The salivary enzyme amylase begins the breakdown of food starches into maltose, a disaccharide. As the bolus of food travels through the esophagus to the stomach, no significant digestion of carbohydrates takes place. The esophagus produces no digestive enzymes but does produce mucous for lubrication. The acidic environment in the stomach stops the action of the amylase enzyme. The next step of carbohydrate digestion takes place in the duodenum. Recall that the chyme from the stomach enters the duodenum and mixes with the digestive secretion from the pancreas, liver, and gallbladder. Pancreatic juices also contain amylase, which continues the breakdown of starch and glycogen into maltose, a disaccharide. The disaccharides are broken down into monosaccharides by enzymes called maltases, sucrases, and lactases, which are also present in the brush border of the small intestinal wall. Maltase breaks down maltose into glucose. Other disaccharides, such as sucrose and lactose are broken down by sucrase and lactase, respectively. Sucrase breaks down sucrose (or “table sugar”) into glucose and fructose, and lactase breaks down lactose (or “milk sugar”) into glucose and galactose. The monosaccharides (glucose) thus produced are absorbed and then can be used in metabolic pathways to harness energy. The monosaccharides are transported across the intestinal epithelium into the bloodstream to be transported to the different cells in the body. The steps in carbohydrate digestion are summarized in Figure 34.16 and Table 34.5.	B: mucous.
What type of amplitudes and wavelengths avoid detection in deep water? Here are the choices: A. low and wide B. low and long C. high and wide D. high and long	An underwater earthquake creates a tsunami this way: The movement of the crust displaces water. The displacement forms a set of waves. The waves travel at jet speed through the ocean. Since the waves have low amplitudes and long wavelengths, they are unnoticed in deep water. As the waves reach shore they compress. They are also pushed upward by the shore. For these reasons, tsunami can grow to enormous wave heights. Tsunami waves can cause tremendous destruction and loss of life. Fortunately, few undersea earthquakes generate tsunami.	B: low and long.
What is the smallest main part of the brain? Here are the choices: A. the stem B. the cortex C. the cerebellum D. the claw	The brain stem is the smallest of the three main parts of the brain. It lies directly under the cerebrum. The brain stem controls basic body functions, such as breathing, heartbeat, and digestion. The brain stem also carries information back and forth between the cerebrum and spinal cord.	A: the stem.
Adding the number of protons plus the number of neutrons in an atom, decides it's approximate mass, what is another word for this value? Here are the choices: A. real number B. atomic mass C. electron count D. atomic number	The type of atom is determined by the atomic number (i. e. the number of protons). The atomic mass of an atom is approximately the number of protons plus the number of neutrons. Typically, the atomic mass listed in a periodic table is an average, weighted by the natural abundances of different isotopes.	D: atomic number.
Why do people build dams and levees? Here are the choices: A. to horde the water B. increase flooding C. store drinking water D. prevent flooding	People build dams and levees to protect from flooding. In an emergency, sandbags can be put out.	D: prevent flooding.
What runs through the penis and opens to the outside at the tip of the penis? Here are the choices: A. prostate gland B. the urethra C. fallopian tube D. vas deferens		B: the urethra.
What is the chemical name of table sugar? Here are the choices: A. sucrose B. potassium C. cellulose D. codeine	There are several dietary sources of carbohydrates. Starch is found in many vegetables (especially potatoes) and baked goods. Sucrose (table sugar) is included as part of many prepared foods. Lactose is found in milk products, and maltose is present in some vegetables.	A: sucrose.
What enzyme is found in the small intestine catalyzes the hydrolysis of lactose? Here are the choices: A. lipase B. elastases C. amylase D. lactase	Chymotrypsin is found in the small intestine and catalyzes the hydrolysis of peptide bonds following aromatic amino acids. Lactase is found in the small intestine and catalyzes the hydrolysis of lactose. Pepsin is found in the stomach and catalyzes the hydrolysis of peptide bonds, primarily those that occur after aromatic amino acids. Maltase is found in the small intestine and catalyzes the hydrolysis of maltose.	D: lactase.
While smooth muscle tissue can regenerate from stem cells called pericytes, dead cardiac muscle tissue is replaced by what type of tissue? Here are the choices: A. Maximum B. neon tissue C. scar tissue D. embryo tissue	10.9 Development and Regeneration of Muscle Tissue Muscle tissue arises from embryonic mesoderm. Somites give rise to myoblasts and fuse to form a myotube. The nucleus of each contributing myoblast remains intact in the mature skeletal muscle cell, resulting in a mature, multinucleate cell. Satellite cells help to repair skeletal muscle cells. Smooth muscle tissue can regenerate from stem cells called pericytes, whereas dead cardiac muscle tissue is replaced by scar tissue. Aging causes muscle mass to decrease and be replaced by noncontractile connective tissue and adipose tissue.	C: scar tissue.
What natural process allows water to return again to the earth’s surface? Here are the choices: A. wind B. erosion C. precipitation D. currents	Condensation creates precipitation. Precipitation includes rain, snow, hail, and sleet. The precipitation allows the water to return again to the Earth’s surface.	C: precipitation.
What is a spectrometer able to produce from starlight? Here are the choices: A. radio waves B. spectrum C. exposure D. aspect	A spectrometer produces a spectrum from starlight. Astronomers can learn a lot about a star by studying its spectrum.	B: spectrum.
Without what food chain component, organic wastes and dead organisms would pile up everywhere, and their nutrients would no longer be recycled? Here are the choices: A. decomposers B. acids C. probiotics D. nitrates	Decomposers are heterotrophs that break down the wastes of other organisms or the remains of dead organisms. When they do, they release simple inorganic molecules back into the environment. Producers can then use the inorganic molecules to make new organic compounds. For this reason, decomposers are essential to every ecosystem. Imagine what would happen if there were no decomposers. Organic wastes and dead organisms would pile up everywhere, and their nutrients would no longer be recycled.	A: decomposers.
What are made on ribosomes in the cytoplasm? Here are the choices: A. proteins B. cells C. lipids D. enzymes	DNA is located in the nucleus. Proteins are made on ribosomes in the cytoplasm. Remember that information in a gene is converted into mRNA , which carries the information to the ribosome. In the nucleus, mRNA is created by using the DNA in a gene as a template. A template is a model provided for others to copy.	A: proteins.
How do you test a hypothesis? Here are the choices: A. think of how they would work B. write things on paper C. conduct experiments D. ask a co-worker about it	Conduct experiments or make observations to test the hypothesis.	C: conduct experiments.
What kind of power plant uses energy to heat water that becomes steam and spins turbines? Here are the choices: A. hydroelectric B. wind C. nuclear power plants D. coal	Nuclear power plants use the energy they produce to heat water. The water turns into steam, which causes a turbine to spin. This in turn produces electricity.	C: nuclear power plants.
What is defined as the product of a force times the distance over which the force acts? Here are the choices: A. motion B. energy C. matter D. work	Work is defined as the product of a force times the distance over which the force acts. The force and the distance must act along the same line; if the angle between them is not (or ) then you must use the component of force; hence the in the equation.	D: work.
Visible light has what that can be detected by the human eye? Here are the choices: A. wavelengths B. patterns C. colors D. dimensions	Visible light is light that has wavelengths that can be detected by the human eye. The wavelength of visible light determines the color that the light appears. As you can see in the Figure below , light with the longest wavelength appears red, and light with the shortest wavelength appears violet. In between are all the other colors of light that we can see. Only seven main colors of light are actually represented in the diagram.	A: wavelengths.
Chemical elements and water are recycled through what cycle? Here are the choices: A. biogeochemical B. evaporation C. biogenic D. dynamical	Chemical elements and water are recycled through biogeochemical cycles. The cycles include both biotic and abiotic parts of ecosystems.	A: biogeochemical.
The anterior muscles of the neck facilitate swallowing and what else? Here are the choices: A. speech B. hearing C. crying D. perspiration	Figure 11.13 Muscles of the Anterior Neck The anterior muscles of the neck facilitate swallowing and speech. The suprahyoid muscles originate from above the hyoid bone in the chin region. The infrahyoid muscles originate below the hyoid bone in the lower neck.	A: speech.
How many directions can ions flow along the axon? Here are the choices: A. two B. three C. six D. one		D: one.
Ionic, covalent, and hydrogen are three important types of what type of interaction between different types of atoms? Here are the choices: A. levels B. forms C. bonds D. conflicts	2.2 \| Chemical Bonds By the end of this section, you will be able to: • Explain the relationship between molecules and compounds • Distinguish between ions, cations, and anions • Identify the key difference between ionic and covalent bonds • Distinguish between nonpolar and polar covalent bonds • Explain how water molecules link via hydrogen bonds Atoms separated by a great distance cannot link; rather, they must come close enough for the electrons in their valence shells to interact. But do atoms ever actually touch one another? Most physicists would say no, because the negatively charged electrons in their valence shells repel one another. No force within the human body—or anywhere in the natural world—is strong enough to overcome this electrical repulsion. So when you read about atoms linking together or colliding, bear in mind that the atoms are not merging in a physical sense. Instead, atoms link by forming a chemical bond. A bond is a weak or strong electrical attraction that holds atoms in the same vicinity. The new grouping is typically more stable—less likely to react again—than its component atoms were when they were separate. A more or less stable grouping of two or more atoms held together by chemical bonds is called a molecule. The bonded atoms may be of the same element, as in the case of H2, which is called molecular hydrogen or hydrogen gas. When a molecule is made up of two or more atoms of different elements, it is called a chemical compound. Thus, a unit of water, or H2O, is a compound, as is a single molecule of the gas methane, or CH4. Three types of chemical bonds are important in human physiology, because they hold together substances that are used by the body for critical aspects of homeostasis, signaling, and energy production, to name just a few important processes. These are ionic bonds, covalent bonds, and hydrogen bonds.	C: bonds.
In classical physics, momentum is a simple product of mass and this? Here are the choices: A. speed B. direction C. velocity D. acceleration	In classical physics, momentum is a simple product of mass and velocity. However, we saw in the last section that when special relativity is taken into account, massive objects have a speed limit. What effect do you think mass and velocity have on the momentum of objects moving at relativistic speeds? Momentum is one of the most important concepts in physics. The broadest form of Newton’s second law is stated in terms of momentum. Momentum is conserved whenever the net external force on a system is zero. This makes momentum conservation a fundamental tool for analyzing collisions. All of Work, Energy, and Energy Resources is devoted to momentum, and momentum has been important for many other topics as well, particularly where collisions were involved. We will see that momentum has the same importance in modern physics. Relativistic momentum is conserved, and much of what we know about subatomic structure comes from the analysis of collisions of accelerator-produced relativistic particles. The first postulate of relativity states that the laws of physics are the same in all inertial frames. Does the law of conservation of momentum survive this requirement at high velocities? The answer is yes, provided that the momentum is defined as follows. Relativistic Momentum Relativistic momentum.	C: velocity.
What compounds contain only carbon and hydrogen? Here are the choices: A. molecules B. carbonates C. particles D. hydrocarbons	You can tell that this sponge is saturated with water because when it is squeezed, the water pours out. When something is saturated with water, it already holds as much water as possible. Compounds called hydrocarbons, which contain only carbon and hydrogen, can also be saturated, but not with water.	D: hydrocarbons.
Synthetic and natural rubber, styrofoam and plastic are examples of organic what? Here are the choices: A. polymers B. microbes C. metals D. solutions	Polymers are a pervasive part of modern life. It is very likely that at least some part of your clothing is made of nylon, rayon, or polyester. The milk or juice that you have for breakfast often comes in a polyethylene container. If you don’t have breakfast at home, you might get coffee from a fast food establishment, where your order is delivered to you in a Styrofoam® container. While getting out of your car, you bang the door on another vehicle. One reason you may not have dented the door is the fact that it could be made out of a polymeric plastic material that resists deformation more than simple metallic structures. Elsewhere on your car, both synthetic and natural rubber are probably present in the tires. All these materials are examples of organic polymers.	A: polymers.
Some viruses carry a few viral enzyme molecules within their what? Here are the choices: A. DNA B. hormones C. plastids D. capsids		D: capsids.
Dietary proteins are broken down into what components when food is digested? Here are the choices: A. organic acids B. amino acids C. protein acids D. polymer acids	Proteins in the diet are necessary for life. Dietary proteins are broken down into their component amino acids when food is digested. Cells can then use the components to build new proteins. Humans are able to synthesize all but nine of the twenty common amino acids. These nine amino acids, called essential amino acids , must be consumed in foods. Like dietary carbohydrates and lipids, dietary proteins can also be broken down to provide cells with energy. The amino acids regarded as essential for humans are phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, leucine, lysine, and histidine. Additionally, cysteine, tyrosine and arginine are required by infants and growing children.	B: amino acids.
What kind of plants do not need adaptations for absorbing, transporting, and conserving water? Here are the choices: A. desert plants B. aquatic plants C. normal plants D. terrestrial plants	Aquatic plants are plants that live in water. 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 cuticles 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.	B: aquatic plants.
Organisms cannot live alone, needing other organisms to survive; what is this relationship called? Here are the choices: A. dominance B. interdependence C. independence D. coexistence	Organisms are not independent, they are interdependent . They cannot live alone; they need other organisms to survive. The same is true for species. All species need other species to survive.	B: interdependence.
What force pulls bodies with mass together? Here are the choices: A. isolation B. solar C. gravity D. thermal	A very important point here is that the vertical motion of these two balls is identical. That is, they each fall exactly the same distance vertically in each succeeding second. The constant horizontal velocity of the blue ball has no effect on its accelerated vertical motion. Therefore, the vertical motion of the blue ball can be analyzed exactly the same as the vertical motion of the red ball.	C: gravity.
If a fixed amount of gas maintains a perfectly inversely proportional relationship between volume and pressure, then what else must be constant about the gas? Here are the choices: A. friction B. surface tension C. density D. temperature	For a fixed amount of gas at constant temperature, the volume is inversely proportional to its pressure.	D: temperature.
What conveys signals received by the eye to the brain? Here are the choices: A. optic nerve B. sensory nerve C. sciatic nerve D. motor nerve	26.1 Physics of the Eye The eye is perhaps the most interesting of all optical instruments. The eye is remarkable in how it forms images and in the richness of detail and color it can detect. However, our eyes commonly need some correction, to reach what is called “normal” vision, but should be called ideal rather than normal. Image formation by our eyes and common vision correction are easy to analyze with the optics discussed in Geometric Optics. Figure 26.2 shows the basic anatomy of the eye. The cornea and lens form a system that, to a good approximation, acts as a single thin lens. For clear vision, a real image must be projected onto the light-sensitive retina, which lies at a fixed distance from the lens. The lens of the eye adjusts its power to produce an image on the retina for objects at different distances. The center of the image falls on the fovea, which has the greatest density of light receptors and the greatest acuity (sharpness) in the visual field. The variable opening (or pupil) of the eye along with chemical adaptation allows the eye to detect light intensities from the 10 lowest observable to 10 times greater (without damage). This is an incredible range of detection. Our eyes perform a vast number of functions, such as sense direction, movement, sophisticated colors, and distance. Processing of visual nerve impulses begins with interconnections in the retina and continues in the brain. The optic nerve conveys signals received by the eye to the brain.	A: optic nerve.
When cardiac muscle contracts, the heart does what? Here are the choices: A. pumps blood B. irregular heartbeat C. heart murmur D. cardiac arrest	Cardiac muscle is found only in the walls of the heart. It is striated, or striped, because its muscle fibers are arranged in bundles. Contractions of cardiac muscle are involuntary. This means that they are not under conscious control. When cardiac muscle contracts, the heart beats and pumps blood.	A: pumps blood.
Do placental mammals give birth to relatively small or large fetuses? Here are the choices: A. large B. they don't give birth C. neither D. small	Placental mammals give birth to a relatively large and mature fetus. This is possible because they have a placenta to nourish the fetus and protect it from the mother’s immune system. This allows for a long period of growth and development before birth.	A: large.
What is the largest class of elements? Here are the choices: A. oils B. organics C. acids D. metals	Metals are elements that are good conductors of electricity. They are the largest class of elements. Many metals are shiny, ductile, and malleable. They are also good conductors of heat. Almost all metals are solids are room temperature.	D: metals.
Liquid hcl can be used to do what to the ph of a swimming pool? Here are the choices: A. raise it B. increase it C. heighten it D. lower it	We all enjoy a cool dip in a swimming pool on a hot day, but we may not realize the work needed to keep that water safe and healthy. The ideal pH for a swimming pool is around 7.2. The pH will change as a result of many factors. Adjustment can be accomplished with different chemicals depending on the tested pH. High pH can be lowered with liquid HCl (unsafe material) or sodium bisulfate. The bisulfate anion is a weak acid and can dissociate partially in solution. To increase pH, use sodium carbonate. The carbonate anion forms an equilibrium with protons that results in some formation of carbon dioxide.	D: lower it.
The three greatest proximate threats to biodiversity are habitat loss, overharvesting, and introduction of what? Here are the choices: A. solar radiation B. exotic species C. carbon dioxide D. carbon monoxide	21.2 \| Threats to Biodiversity By the end of this section, you will be able to: • Identify significant threats to biodiversity • Explain the effects of habitat loss, exotic species, and hunting on biodiversity • Identify the early and predicted effects of climate change on biodiversity The core threat to biodiversity on the planet, and therefore a threat to human welfare, is the combination of human population growth and the resources used by that population. The human population requires resources to survive and grow, and those resources are being removed unsustainably from the environment. The three greatest proximate threats to biodiversity are habitat loss, overharvesting, and introduction of exotic species. The first two of these are a direct result of human population growth and resource use. The third results from increased mobility and trade. A fourth major cause of extinction, anthropogenic (human-caused) climate change, has not yet had a large impact, but it is predicted to become significant during this century. Global climate change is also a consequence of human population needs for energy and the use of fossil fuels to meet those needs (Figure 21.7). Environmental issues, such as toxic pollution, have specific targeted effects on species, but are not generally seen as threats at the magnitude of the others.	B: exotic species.
The sun’s energy is converted to chemical energy by a what? Here are the choices: A. mammal B. bacterium C. amphibian D. plant	The sun’s energy is converted to chemical energy by a plant. An animal gets energy when it eats the plant. The student gets energy when it eats the animal. The boy’s energy is used to pedal the bike.	D: plant.
What are antacids comprised of? Here are the choices: A. bases B. gases C. acids D. solids	Bases are less common as foods, but they are nonetheless present in many household products. Many cleaners contain ammonia, a base. Sodium hydroxide is found in drain cleaner. Antacids , which combat excess stomach acid, are comprised of bases such as magnesium hydroxide or sodium hydrogen carbonate.	A: bases.
Where can neurohormones act within the body? Here are the choices: A. throughout B. nerve endings C. digestive process D. brain only		A: throughout.
What are composed of a phosphate group, a sugar, and one of five different nitrogenous bases. Here are the choices: A. nucleotides B. carotenoids C. cytotypes D. prokaryotes	Nucleotides are composed of a phosphate group, a sugar, and one of five different nitrogenous bases.	A: nucleotides.
Scientists measure the gases that escape from a volcano to predict what? Here are the choices: A. storms B. snowfall C. floods D. eruptions	Scientists measure the gases that escape from a volcano to predict eruptions. Gases like sulfur dioxide (SO 2 ), carbon dioxide (CO 2 ), hydrochloric acid (HCl), and water vapor can be measured at the site. Gases may also be measured from satellites. The amounts of gases and the ratios of gases are calculated to help predict eruptions.	D: eruptions.
What molecule is made of two hydrogen atoms and one oxygen atom? Here are the choices: A. carbohydrate B. lipids C. water D. Oxygen	A molecule of water ( Figure below ) is made of three atoms bonded together. Two of these atoms are hydrogen and one atom is oxygen. The hydrogen ions have a positive electrical charge. The oxygen atom has a negative electrical charge. The hydrogen atoms are located on one side and the oxygen atom on the other. This means that the side with the hydrogen ions has a slightly positive charge. The other side, the side without the hydrogen ions, has a slightly negative charge. The water molecule is a polar molecule .	C: water.
What occurs when muscle fibers get shorter? Here are the choices: A. muscle tension B. muscle contraction C. muscle extension D. muscle diffusion	Muscle contraction occurs when muscle fibers get shorter. Literally, the muscle fibers get smaller in size. To understand how this happens, you need to know more about the structure of muscle fibers.	B: muscle contraction.
The nitrogen cycle includes air, soil, and what? Here are the choices: A. decomposers B. living things C. water D. heat	The nitrogen cycle includes air, soil, and living things.	B: living things.
As the organism grows more sophisticated, what happens to the process of gene regulation? Here are the choices: A. degenerates B. becomes simplified C. becomes more complex D. becomes fractured	As the organism grows more sophisticated, gene regulation becomes more complex, though prokaryotic organisms possess some highly regulated systems. Some human genes are controlled by many activators and repressors working together. Obviously, a mutation in a cis-regulatory region, such as the promoter, can greatly affect the proper expression of a gene. It may keep the gene permanently off, such that no protein can be made, or it can keep the gene permanently on, such that the corresponding protein is constantly made. Both of these can have detremental effects on the cell.	C: becomes more complex.
Rh antibodies can prove dangerous if they cross what barrier in pregnancy? Here are the choices: A. placental B. fungal C. embryo D. stomach	A drug known as RhoGAM, short for Rh immune globulin, can temporarily prevent the development of Rh antibodies in the Rh− mother, thereby averting this potentially serious disease for the fetus. RhoGAM antibodies destroy any fetal Rh+ erythrocytes that may cross the placental barrier. RhoGAM is normally administered to Rh− mothers during weeks 26−28 of pregnancy and within 72 hours following birth. It has proven remarkably effective in decreasing the incidence of HDN. Earlier we noted that the incidence of HDN in an Rh+ subsequent pregnancy to an Rh− mother is about 13–14 percent without preventive treatment. Since the introduction of RhoGAM in 1968, the incidence has dropped to about 0.1 percent in the United States.	A: placental.
Galaxies can be spiral, elliptical, or which other type? Here are the choices: A. vertical B. simple C. irregular D. oblong	Galaxies can be spiral, elliptical, or irregular.	C: irregular.
What often involves the loss of hydrogen, the gain of oxygen, or the loss of electrons? Here are the choices: A. carbonation B. decomposition C. precipitation D. oxidation	Oxidation often involves the loss of hydrogen, the gain of oxygen, or the loss of electrons.	D: oxidation.
Luster, malleability, ductility, and conductivity are all properties of which kind of material? Here are the choices: A. ores B. wood C. nonmetals D. metals	The image above is of a copper plate that was made in 1893. The utensil has a great deal of elaborate decoration and the item is very useful. What would have happened if we decided that copper (I) chloride was just as good a material (well, it does have copper in it). The CuCl would end up as a powder when we pounded on it to shape it. Metals behave in unique ways. The bonding that occurs in a metal is responsible for its distinctive properties: luster, malleability, ductility, and excellent conductivity.	D: metals.
Anosmia, the loss of what sense, is often the result of the olfactory nerve being severed? Here are the choices: A. taste B. smell C. general sensitivity D. balance	Nervous System Anosmia is the loss of the sense of smell. It is often the result of the olfactory nerve being severed, usually because of blunt force trauma to the head. The sensory neurons of the olfactory epithelium have a limited lifespan of approximately one to four months, and new ones are made on a regular basis. The new neurons extend their axons into the CNS by growing along the existing fibers of the olfactory nerve. The ability of these neurons to be replaced is lost with age. Age-related anosmia is not the result of impact trauma to the head, but rather a slow loss of the sensory neurons with no new neurons born to replace them. Smell is an important sense, especially for the enjoyment of food. There are only five tastes sensed by the tongue, and two of them are generally thought of as unpleasant tastes (sour and bitter). The rich sensory experience of food is the result of odor molecules associated with the food, both as food is moved into the mouth, and therefore passes under the nose, and when it is chewed and molecules are released to move up the pharynx into the posterior nasal cavity. Anosmia results in a loss of the enjoyment of food. As the replacement of olfactory neurons declines with age, anosmia can set in. Without the sense of smell, many sufferers complain of food tasting bland. Often, the only way to enjoy food is to add seasoning that can be sensed on the tongue, which usually means adding table salt. The problem with this solution, however, is that this increases sodium intake, which can lead to cardiovascular problems through water retention and the associated increase in blood pressure.	B: smell.
Which planet is the kuiper belt closest to? Here are the choices: A. Venus B. Jupiter C. Mars D. neptune	Figure below shows those distances correctly. In the upper left are the orbits of the inner planets and the asteroid belt. The asteroid belt is a collection of many small objects between the orbits of Mars and Jupiter. In the upper right are the orbits of the outer planets and the Kuiper belt. The Kuiper belt is a group of objects beyond the orbit of Neptune.	D: neptune.
Does warm air sit above or below cooler air in the troposphere? Here are the choices: A. above B. adjacent C. below D. near	In the troposphere, warm air ordinarily sits below cooler air.	C: below.
What is the name for the stratospheric gas layer that protects living things from uv radiation? Here are the choices: A. carbon layer B. ozone layer C. atmospheric layer D. toposphere	The stratosphere contains a layer of ozone gas. Ozone consists of three oxygen atoms (O 3 ). The ozone layer absorbs high-energy UV radiation. As you can see in Figure below , UV radiation splits the ozone molecule. The split creates an oxygen molecule (O 2 ) and an oxygen atom (O). This split releases heat that warms the stratosphere. By absorbing UV radiation, ozone also protects Earth’s surface. UV radiation would harm living things without the ozone layer.	B: ozone layer.
All atoms have equal numbers of what two particles? Here are the choices: A. electrons and protons B. photons and protons C. electrons and neutrons D. nuclei and neutrons	Electrons are one of three main types of particles that make up the atom. They are extremely small and have an electric charge of -1. All atoms have the same number of electrons as protons.	A: electrons and protons.
What is the only planet that rotates clockwise as viewed from its north pole? Here are the choices: A. mars B. venus C. uranus D. earth	Venus is the only planet that rotates clockwise as viewed from its North Pole. All of the other planets rotate counterclockwise. Venus turns slowly, making only one turn every 243 days. This is longer than a year on Venus! It takes Venus only 225 days to orbit the Sun.	B: venus.
Most radioactive emissions that people are exposed to are on the order of a few dozen what? Here are the choices: A. ticks B. micrograms C. millirems D. millivolts	rem = rad × factor where factor is a number greater than or equal to 1 that takes into account the type of radioactive emission and sometimes the type of tissue being exposed. For beta particles, the factor equals 1. For alpha particles striking most tissues, the factor is 10, but for eye tissue the factor is 30. Most radioactive emissions that people are exposed to are on the order of a few dozen millirems (mrem) or less; a medical X-ray is about 20 mrem. A sievert (Sv) is a related unit and is defined as 100 rem. What is a person’s annual exposure to radioactivity and radiation? Table 15.3 "Average Annual Radiation Exposure (Approximate)" lists the sources and annual amounts of radiation exposure. It may surprise you to learn that fully 82% of the radioactivity and radiation exposure we receive is from natural sources— sources we cannot avoid. Fully 10% of the exposure comes from our own bodies—largely from carbon-14 and potassium-40. Table 15.3 Average Annual Radiation Exposure (Approximate).	C: millirems.
What decay produces helium nuclei? Here are the choices: A. radiative decay B. duo decay C. alpha decay D. Beta Decay	A final effect of this trapped radiation merits mention. Alpha decay produces helium nuclei, which form helium atoms when they are stopped and capture electrons. Most of the helium on Earth is obtained from wells and is produced in this manner. Any helium in the atmosphere will escape in geologically short times because of its high thermal velocity. What patterns and insights are gained from an examination of the binding energy of various nuclides? First, we find that BE is approximately proportional to the number of nucleons A in any nucleus. About twice as much energy is needed to pull apart a nucleus like 24 Mg compared with pulling apart 12 C , for example. To help us look at other effects, we divide BE by A and consider the binding energy per nucleon, BE / A . The graph of BE / A in Figure 31.27 reveals some very interesting aspects of nuclei. We see that the binding energy per nucleon averages about 8 MeV, but is lower for both the lightest and heaviest nuclei. This overall trend, in which nuclei with A equal to about 60 have the greatest BE / A and are thus the most tightly bound, is due to the combined characteristics of the attractive nuclear forces and the repulsive Coulomb force. It is especially important to note two things—the strong nuclear force is about 100 times stronger than the Coulomb force, and the nuclear forces are shorter in range compared to the Coulomb force. So, for low-mass nuclei, the nuclear attraction dominates and each added nucleon forms bonds with all others, causing progressively heavier nuclei to have progressively greater values of BE / A . This continues up to A ≈ 60 , roughly corresponding to the mass number of iron. Beyond that, new nucleons added to a nucleus will be too far from some others to feel their nuclear attraction. Added protons, however, feel the repulsion of all other protons, since the Coulomb force is longer in range. Coulomb repulsion grows for progressively heavier nuclei, but nuclear attraction remains about the same, and so BE / A becomes smaller. This is why stable nuclei heavier than A ≈ 40 have more neutrons than protons. Coulomb repulsion is reduced by having more neutrons to keep the protons farther apart (see Figure 31.28).	C: alpha decay.
Instead of wood, what do some fireplaces use? Here are the choices: A. propane B. acetylene C. kerosene D. gasoline	Some fireplaces use propane gas rather than wood as fuel.	A: propane.
What is the sum of all biochemical reactions in cells called? Here are the choices: A. respiration B. metabolism C. evolution D. diffusion	Biochemical reactions are chemical reactions that take place inside living things. Thousands of biochemical reactions continuously take place inside each cell. The sum of all these biochemical reactions is called metabolism.	B: metabolism.
What process is magnesium important to? Here are the choices: A. photosynthetic B. absorption C. carbon cycle D. dna replication	Magnesium (Mg) and calcium (Ca) are also important macronutrients. The role of calcium is twofold: to regulate nutrient transport, and to support many enzyme functions. Magnesium is important to the photosynthetic process. These minerals, along with the micronutrients, which are described below, also contribute to the plant’s ionic balance. In addition to macronutrients, organisms require various elements in small amounts. These micronutrients, or trace elements, are present in very small quantities. They include boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), molybdenum (Mo), nickel (Ni), silicon (Si), and sodium (Na). Deficiencies in any of these nutrients—particularly the macronutrients—can adversely affect plant growth (Figure 31.4. Depending on the specific nutrient, a lack can cause stunted growth, slow growth, or chlorosis (yellowing of the leaves). Extreme deficiencies may result in leaves showing signs of cell death.	A: photosynthetic.
What type of shots do people with allergy get? Here are the choices: A. booster shots B. allergy shots C. nasal shots D. flu shots	Sometimes people with an allergy get allergy shots. They are injected with tiny amounts of the allergen that triggers the allergic reaction. The shots are repeated at regular intervals, and the amount of allergen that is injected each time gradually increases. How do you think this might help an allergy? Do you think this approach just treats allergy symptoms or might it cure the allergy?.	B: allergy shots.
Where do polychaete worms live? Here are the choices: A. the ocean floor B. garden soil C. digestive tract D. lakes	Polychaete worms live on the ocean floor. They may be sedentary filter feeders or active predators or scavengers. Active species crawl along the ocean floor in search of food.	A: the ocean floor.
What kind of material that might otherwise go to a landfill can serve as the source of biomass power? Here are the choices: A. mechanical waste B. reactive waste C. organic waste D. microscopic waste	Any organic material can be made into electricity. But some materials are better than others. Wastes can be used, like almond shells. Biomass power is a great use of wastes. It's hard to use wastes as a consistent large scale source of energy though.	C: organic waste.
What was the appendix used for in the past but is no longer needed for? Here are the choices: A. sense danger B. digest food C. fight infection D. produce food	The appendix is a tiny remnant of a once-larger organ. In a distant ancestor, it was needed to digest food. If your appendix becomes infected, a surgeon can remove it. You won’t miss it because it no longer has any purpose in the human body.	B: digest food.
Dermal, vascular, and ground tissue make up what part of a plant, which bears the leaves, flowers and fruits? Here are the choices: A. leaves B. root C. stem D. flowers	30.2 Stems The stem of a plant bears the leaves, flowers, and fruits. Stems are characterized by the presence of nodes (the points of attachment for leaves or branches) and internodes (regions between nodes). Plant organs are made up of simple and complex tissues. The stem has three tissue systems: dermal, vascular, and ground tissue. Dermal tissue is the outer covering of the plant. It contains epidermal cells, stomata, guard cells, and trichomes. Vascular tissue is made up of xylem and phloem tissues and conducts water, minerals, and photosynthetic products. Ground tissue is responsible for photosynthesis and support and is composed of parenchyma, collenchyma, and sclerenchyma cells. Primary growth occurs at the tips of roots and shoots, causing an increase in length. Woody plants may also exhibit secondary growth, or increase in thickness. In woody plants, especially trees, annual rings may form as growth slows at the end of each season. Some plant species have modified stems that help to store food, propagate new plants, or discourage predators. Rhizomes, corms, stolons, runners, tubers, bulbs, tendrils, and thorns are examples of modified stems.	C: stem.
What term is used to describe the conditions in the sky on any particular day? Here are the choices: A. humidity B. temperature C. weather D. forecast		C: weather.
What does the human body produce to help digest food? Here are the choices: A. carbohydrates B. enzymes C. vitamins D. fiber	The human body produces many enzymes that help digest food. Here are just two examples.	B: enzymes.
What is a coil of wire with electric current flowing through it called? Here are the choices: A. hydraulic valve B. carrier valve C. tectonic valve D. a solenoid	An electromagnet is a solenoid wrapped around a bar of iron or other ferromagnetic material. A solenoid is a coil of wire with electric current flowing through it. This gives the coil north and south magnetic poles and a magnetic field. The magnetic field of the solenoid magnetizes the iron bar by aligning its magnetic domains. You can see this in the Figure below . You can learn how to make an electromagnet at this URL: http://www. youtube. com/watch?v=emlzh9XXWgQ.	D: a solenoid.

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