The Lone Ranger
07-03-2007, 09:19 AM
Oh, what the heck. Here are my answers, along with some commentary that’ll hopefully be helpful/illuminating. Personally, I think the test is poorly constructed, but what do I know?
I just hate trivia-type questions that are devoid of any context or explanation. They aren't tests of understanding; they're tests of recall. I tend to be much more concerned about whether or not students understand things than whether or not they can regurgitate definitions on command, without necessarily understanding what those terms mean.
Question #1:
Northern garter snakes exhibit a unique behavior in which they gather in deep dens by the hundreds or thousands. They then coil together in a huge ball. This behavior could help to
Locate food sources
Increase camouflage
Reduce heat loss
Increase oxygen consumption
The behavior, incidentally, is not unique to “northern garter snakes,” but it reaches its most spectacular expression in garter snakes, specifically Red-Sided Garter Snakes (Thamnophis sirtalis) living in Canada. Numerous other animal species have similar behaviors, including some mammals, such as the Northern Flying Squirrel (Glaucomys sabrinus) – though, admittedly, the squirrels don’t spend all winter aggregated into balls like the snakes do.
Why is this an effective mechanism for reducing loss of body heat? Well, keep in mind that you lose (or gain) body heat across body surfaces. A snake, being a very elongated animal, has a lot of surface area compared to, say, a frog of the same body weight. Consequently, snakes lose body heat very rapidly. If the snake’s body temperature falls below the point where ice starts to form in the tissues, it will die, so keeping the body temperature from falling too low is critical for winter survival.
The greater the temperature difference between your body and the outside environment, the faster you will lose body heat. Also, an animal’s body is mostly water, and water tends to hang onto heat quite well, compared to air. So, if your body is in contact with cold air, you’ll lose body heat rapidly, especially if you’re a snake and have lots of surface area in contact with that cold air. Conversely, if your body surface is mostly in contact with other snakes – snakes that are at about the same temperature as you and are composed mostly of water – your loss of body heat is greatly reduced. In fact, if you’re in the center of the ball of snakes, surrounded by snakes on all sides, then you’re absorbing heat from all sides, heat radiated by the snakes surrounding you. If anything, you may become too warm. Snakes on the outside of the ball, of course, have only a little insulation from the cold, and so tend to lose body heat pretty rapidly. So, there’s a slow turnover of snakes as those toward the outside move inward and some of the snakes in the interior get displaced to the outside of the aggregation.
Question #2:
This type of rock is buried deep within the earth’s crust.
Metamorphic rock
Sedimentary rock
Minerals
Igneous rock
The three main types of rocks are sedimentary rocks, igneous rocks, and metamorphic rocks. Each can be found buried within the Earth’s crust, and two of them form only when more or less completely buried.
Sedimentary rocks form when sediments deposited by wind, water or gravity become buried and slowly compacted until they ultimately harden into rock. For instance, sand that is buried and compacted ultimately forms sandstone; clay or mud that is compacted into rock forms shale, and so forth.
Igneous rocks are rocks that form from solidified lava or magma. (The difference between lava and magma is simple; molten rock on the surface is called “lava”; molten rock that’s below the Earth’s surface is called “magma.”) Basalt is a common example of an igneous rock that forms when magma cools and hardens underground, or flows onto the surface as lava and then hardens. Granite is another common igneous rock. Basalt usually forms from lava flowing onto the Earth’s surface; granite usually forms from magma that hardens underground and is later exposed when erosion removes the surface rocks that cover it.
Metamorphic rocks form when existing rocks (sedimentary rocks, igneous rocks, or preexisting metamorphic rocks) are buried deep in the Earth’s crust, where they’re subjected to intense pressure and heat, causing them to undergo physical and/or chemical changes into different kinds of rocks. For example, when shale is buried, heated and compressed, it metamorphoses into slate. Limestone metamorphoses into marble. Some forms of gneiss are metamorphosed granite.
A mineral, by the way, is a chemical substance that is normally crystalline in nature, and that has been formed by geological processes. Rocks are made of minerals, but a “mineral” is not a kind of rock.
Question #3:
Comets are composed of ____ left over from the formation of our solar system.
Rock
Dirty ice
Stony iron
Nickel
In deep space, a comet is a ball of water ice, dust, and rock. As such, it is often referred to as a “dirty snowball.” Actually, because of all the dust, rock, and organic molecules on and in the comet, it’s quite dark – it only looks bright to us because there’s nothing nearby for comparison. The Giotto probe discovered that the solid portion (the nucleus) of Comet Halley reflected only about 4% of incoming light – that makes it about as dark as black paint.
As a comet comes into the inner solar system, close to the Sun, it absorbs solar radiation and heats up. It’s thought that as this happens, ice and other volatile materials melt and then vaporize, producing the comet’s large and distinctive tail.
Actually, most comets have two tails. Pressure from the Sun’s radiation, as well as fast-moving particles emitted from the Sun (called the solar wind) create the comet’s tails. As the comet evaporates, relatively heavy dust particles are blown off, forming the dust tail, which consists of particles following the nucleus in the comet’s orbit. As a consequence, this tail is often distinctly curved. Gases ionized by the sun’s radiation and by interaction with the solar wind form the more tenuous ion tail, which always points directly away from the Sun, regardless of the comet’s direction of travel.
Question #4:
Which form of solar radiation causes sunburn?
Visible
Ultraviolet
Infrared
X-rays
Radio waves
Electromagnetic radiation consists of moving photons. The more energetic the photons, the shorter the wavelength of the radiation – and also, the more easily it penetrates substances.
Very low-energy photons form very long-wavelength radiation known as radio waves. Higher-energy photons are infrared light, which is invisible to the eye, though we can feel it if it’s sufficiently intense. It is absorbed as heat energy.
Higher-energy photons form visible light. The least-energetic form of visible light is what our eyes interpret as “red” light; the most energetic form of visible light is interpreted by our eyes as “violet” light.
Slightly more energetic photons form ultraviolet light. UV light is not visible to our eyes, but it is sufficiently energetic to penetrate into the surface tissues of the body, where it can damage DNA and other organic molecules. The damage it causes results in sunburn because as the body attempts to repair the damage, more blood is routed to the damaged tissue. The increased blood flow causes the damaged skin tissues to visibly redden and swell, and nerve endings in the area become stimulated, resulting in pain.
Even more energetic radiation takes the form of X-rays. Ironically, perhaps, X-rays are less likely to cause damage, since they’re so energetic that they’ll pass right through most body tissues (with the notable exception of bone). On the other hand, given its highly energetic state, if an X-ray photon does happen to be absorbed by a body tissue, it can cause quite a bit of damage.
Question #5:
A large truck and a small car fall with the same exact velocity. Which vehicle has more momentum?
The truck
The car
They both have the same momentum
An object’s momentum is its mass multiplied by its velocity (momentum = mass x velocity). Thus, assuming the truck is more massive than the car (probably a safe bet), if both are traveling at the same velocity, the truck must have a greater momentum.
Question #6:
Shock waves pass through the layers of the earth after an earthquake. The waves vary as they pass through different materials in the earth. Shock waves are also called _____ waves.
Weathering
Sonic
Lithospheric
Seismic
Core
A shock wave is a compression wave moving through some medium, carrying energy as it moves through the substance. The denser the substance (the medium), the closer-together are its molecules and the easier it is to transfer energy from one molecule to the next. As a result, compression waves move through denser media (like rock, for instance) faster and easier than they do through less-dense media (like air, for instance).
This is a purely definitional question. Compression waves moving through the Earth are called seismic waves. Compression waves moving through the atmosphere are usually called sound waves or simply sound.
Incidentally, because the seismic waves change speed (and therefore direction) when moving though substances with different densities, it’s possible to infer the densities (and, therefore, the composition) of different portions of the Earth by how seismic waves move through them.
Question #7:
_____ are hurtling through space and not captured in Earth’s atmosphere.
Meteors
Meteorites
Meteoroids
This is purely a definitional question. A meteoroid is a sand-sized to boulder-sized piece of debris moving through the solar system. Smaller objects are referred to as “interplanetary dust” and larger objects are “asteroids.” (What is the difference between “interplanetary dust,” “meteoroids” and “asteroids”? None, except size. The boundary between them is necessarily arbitrary.)
A meteoroid that enters the Earth’s atmosphere is a meteor. More precisely, the “meteor” is the glowing trail of the meteoroid as it passes through the atmosphere.
Incidentally, the glowing of the meteor is not caused by frictional heating, as is generally thought. If the meteoroid is smaller than about 10 centimeters in diameter, it is partially or completely vaporized as it rapidly moves through the Earth’s atmosphere and collides with air molecules. Collisions between the fast-moving, newly-liberated meteoroid atoms and atmospheric atoms knock electrons loose from their orbitals, and the resulting absorption and release of energy by ions and atoms causes the visible glow. Larger meteoroids aren’t ablated so rapidly, and compress the atmospheric gases ahead of them as they pass through the atmosphere at hypersonic speed. This compression heats the gases to incandescence, causing the visible glow.
A meteoroid that survives its passage through the Earth’s atmosphere and strikes the surface is a meteorite. (“Meteor Crater” in Arizona is mis-named; it should be Meteorite Crater. “Asteroid Crater” might be even more appropriate, since the impactor that created it was large-enough to be considered a small asteroid.)
Question #8:
What causes tides in the ocean?
The polar ice caps
The moon’s gravitational pull
The sun
Wind
The gravity created by an object drops off by the inverse square of your distance from its center of mass. For example, you’re currently about 4,000 miles from the Earth’s center of mass. If you could stand on a support that’s 4,000 miles above the Earth’s surface (and is therefore 2 times as far from the Earth’s center of mass), you’d feel the Earth’s gravity as being (1/2)2 = 1/4th as strong. If you could then move to a support 8,000 miles above the Earth’s surface (and therefore 3 times further from the Earth’s center of mass), you’d feel the Earth’s gravity as being (1/3)2 = 1/9th as strong. And so forth.
What this means is that if “Object A” is large-enough, and if it’s close-enough to another massive body (we’ll call that “Object B”), there is a noticeable difference between the gravitational force exerted by Object B on Object A’s near surface (the surface facing Object B) and Object A’s far surface. This difference in gravitational forces experienced by the different sides of Object A is the tidal force.
The pull exerted by the Moon’s gravity on the Earth’s near side pulls that portion of the Earth with more force than it pulls the Earth’s far side. If the Earth were a liquid, this would raise a noticeable bulge on the near side. Of course, the Earth is relatively solid, and so the bulge in the Earth’s crust is minimal. The oceans, of course, are not so rigid, and so they do bulge upward on the side facing the Moon. Ironically, there is a second tidal bulge in the oceans on the Earth’s far side. This is not a direct result of the Moon’s gravitational pull on the oceans, but is due to the fact that the Earth is relatively rigid, and so moves as a unit. In effect, the gravitation pull of the Moon on the Earth causes the entire Earth to move toward the Moon, since it’s too rigid for only the near portion of it to move toward the Moon. The ocean isn’t so constrained, and so the tidal bulge on the Earth’s far side is, in effect, caused by the Earth pulling away from the non-rigid ocean.
The Sun also exerts a tidal influence on the Earth. But, even though the Sun is much more massive than is the Moon and has a much greater gravitational influence on the Earth overall, its tidal influence is much less than is the Moon’s. That’s because the sun is too far away for there to be much of a difference in the strength of its gravity between the Earth’s near side and far side.
Even so, the Sun does exert a noticeable tidal influence, which is why the ocean tides are higher (and lower) when the Sun and Moon are in alignment, and less intense when they’re pulling at right angles to each other.
Question #9:
What is the name given to water loss to the atmosphere by green plants?
Evaporation
Transpiration
Condensation
Distillation
Transpiration is the term for the process by which water evaporates from the leaves and other exposed surfaces of a plant, and into the atmosphere. Transpiration is an important process, to be sure. In fact, the amount of water added to the atmosphere by transpiration of water that was originally absorbed from the soil can be impressive – so much water vapor is added to the atmosphere by the large tropical forests that they influence global weather patterns. (This is yet another reason why preserving them is probably in our best interests.)
Regardless, transpiration is a form of evaporation, so I’m not sure that “evaporation” should be considered an incorrect answer, though it’s clear that the question was searching for “transpiration” as the “correct” answer.
Question #10:
Tectonic plates sliding past one another can cause…
Evaporation
Volcanoes
Constructive plate margins
Destructive plate margins
Earthquakes
The solid Earth’s crust is broken up into tectonic plates which float upon the semi-liquid mantle below. Convection currents in the mantle cause these tectonic plates to slowly move across the Earth’s surface, and are thus responsible for the phenomenon of continental drift.
Where tectonic plates meet, one of three types of boundaries occurs. A transform boundary (or Conservative Boundary) occurs where the two plates are sliding past each other. The San Andreas Fault is a well-known example. Needless to say, there’s a lot of friction where two plates meet, and they don’t slide smoothly. Typically, what happens is that pressure builds until there is a sudden movement (a slip). That sudden movement of one or both plates causes an earthquake.
Where two plates are sliding apart from each other, a Divergent Boundary (or Constructive Boundary) occurs. As the plates pull apart, magma wells up from the Earth’s interior, creating new crust that fills the gap.
Where two plates are sliding together, a Convergent (Destructive) Boundary occurs. If one plate is forced under the other, it is subducted. The subducted plate partially melts and the material returns to the surface in the form of volcanic eruptions. The Cascade Mountain Range, for example, is a volcanic chain that is the result of subduction where two plates have collided. If neither plate is subducted, the two plates crumple at the impact zone, like the crumpling of fenders in a very slow-motion car wreck. The resulting crumpling of the Earth’s crust forms mountain ranges, such as the Rockies.
Question #11:
How do mammals respire?
Aerobically
Anaerobically
Both aerobically and anaerobically
Physiologically speaking, respiration is not the movement of air in and out of our lungs. That’s “breathing,” or more precisely, it’s “ventilation.”
Respiration refers to the movements of the gases oxygen (O2) and carbon dioxide (CO2) into and out of body tissues as they take part in the generation of energy. (Ventilation, therefore, is only a part of respiration.)
Cellular respiration occurs when living cells break down organic molecules for energy. Most cellular respiration is aerobic, meaning that it requires oxygen. The oxygen is used to efficiently break down organic molecules (chiefly glucose) for energy, releasing CO2 and water (H2O) as waste products. Many cells are also capable of anaerobic metabolism; anaerobic respiration does not require oxygen, but it produces far less energy than does aerobic respiration. Also, anaerobic respiration often produces toxic waste products, so it can go on for only so long in animals and other multicellular organisms.
Most of the time, your cells are producing energy aerobically, but some body cells (notably skeletal muscle cells) can produce energy for a time through anaerobic respiration – for instance, in an emergency situation where they’re working so hard that they’re consuming oxygen faster than it can be delivered by the blood. Needless to say, mammals such as ourselves can only produce energy through anaerobic respiration for so long, as it produces lactate as a waste product. The lactate is not directly toxic, but production of lactate does lead to accumulation of dangerous, highly-reactive hydrogen ions. Our muscles will shut down when lactate levels become sufficiently high, so we can’t poison ourselves with heavy exertion. That’s probably small comfort if you happen to be running from a hungry grizzly bear, I suppose.
Question #12:
Is the offspring of an asexual organism genetically identical to its parent?
Yes
No
The “correct” answer is wrong.
As ceptimus pointed out, if the offspring of asexually-reproducing parents were always genetically identical to their parents, then asexually-reproducing species could not evolve. Since the earliest life-forms were surely asexual, that means life would never have gotten past its earliest stages. Genetic mutations, though relatively rare, are still sufficiently common that each of us has probably inherited at least 100 of them. Even in asexual organisms, genetic mutations guarantee that organisms are unlikely to be genetically identical to their parents. Nearly identical, yes, but not quite identical.
Question #13:
What are the two main functions of fruit for a plant?
To attract insects and to protect the seeds
To disperse and protect the seeds
To disperse the seeds and attract insects
To store food for itself and to protect seeds
This one, at least, has a fairly straightforward answer, or so it seems at first blush. Actually, the fruits of different species can perform quite a few functions. Still, helping to disperse the seeds and protecting them from harm are generally agreed to be the two most common functions of fruits.
The fruit generally forms a protective layer around the seed(s), protecting them from desiccation or other damage. (In some fruits, e.g. strawberries, the fruit does not surround and protect the seeds, however.) In most cases, the fruit is somehow adapted to help disperse the seeds as well.
Some seeds are dispersed by the wind. In such cases, the fruit is light and has a very large surface area, so that it can be picked up and carried by the wind. Dandelions and milkweeds are examples of plants that have wind-transported seeds and light, fluffy fruits that help the seeds get and remain airborne.
Some seeds are surrounded by fruits that float on water, and so are transported by water. Coconuts are a well-known example.
Some seeds are transported by animals. In some cases, the fruits have sticky or barbed coats, causing them to stick to animals and thus be transported. (Think of burrs.) (Trivia: Velcro was invented by a Swiss engineer named Georges de Mestral, after he was inspired by examining burdocks stuck to his dog’s coat.)
Some fruits are adapted to be eaten by animals. In such cases, the seeds are protected by an acid-resistant coat that allows them to pass through an animal’s digestive system unharmed. After a time, the animal deposits the seeds somewhere (hopefully some distance away from the parent plant), along with some free fertilizer. Some seeds, in fact, won’t germinate unless they have passed through an animal’s digestive tract.
Question #14:
A stone dropped from a helicopter takes 10 seconds to hit the sea below. What is its final velocity? (Assume that the acceleration due to gravity is 10 m/s2
10 m/s2
100 m/s2
0 m/s2
1 m/s2
Acceleration over time (which we’ll abbreviate as “a”) = (v – u)/t. In the equation, “v” represents the final velocity, “u” represents the initial velocity, and “t” represents time.
We know the acceleration (10 meters/second2).* I think it’s safe to assume that the helicopter is neither climbing nor in a power dive at the moment the stone is released, so we’ll assume that the stone’s initial velocity is 0 meters/second. We know that the stone falls for 10 seconds. So, all we have to do is solve for “v”, the final velocity.
The original equation is a = (v – u)/t. Since u is 0, the actual equation is a = v/t . We can easily rearrange the equation by multiplying each side by “t”, giving us at = v . Now, all we have to do is plug in the numbers.
(10 m/s2)(10 s) = v , therefore v = 100 m/s .
*Yes, I know the acceleration is actually 9.80665 m/s2, but I figure 10 m/s2 is close enough for an 8th-grader. Besides, if we really want to be picky, air resistance will ensure that the stone doesn’t quite reach even 98.0665 m/s in 10 seconds’ time.
Question #15:
The colour of a pure red rose in white sunlight is a result of the fact that:
The rose absorbs red light only.
The rose absorbs all white light.
The rose reflects only red light
The rose reflects all light except red.
White light contains all the colors of the spectrum. (Actually, you can get what our eyes interpret as “white” light by combining light of only 3 different colors, but I digress.) The color of an object is determined by what wavelengths of light it reflects, if any. An object that reflects no visible light is either transparent (if light simply passes through it without being reflected), or is black (if it absorbs visible light of all wavelengths).
A “pure red” object, then, is one which reflects red light only.
Question #16:
The source of energy for the Earth’s water cycle is the
Wind
Sun’s radiation
Earth’s radiation
Sun’s gravity
Solar radiation falling on the Earth’s surface is absorbed, causing it to heat up. This causes water to evaporate from the surface and into the atmosphere. When this water-bearing air cools (as happens, for example, when it’s forced to move upward when it encounters a mountain range), the water condenses and falls back to Earth as rain or snow.
The water flows across the Earth’s surface in streams and rivers (or, more rarely, as glaciers), and through loose rock and soil as groundwater. Some of it evaporates back into the atmosphere. Some of it is absorbed by living things and then returned either to the Earth (in urine, etc.) or to the atmosphere (through respiration and transpiration). Ultimately, most of this water sooner or later winds up in the oceans. There, absorption of solar radiation by the oceans causes evaporation of water into the atmosphere – and the cycle continues.
Question #17:
Which BEST describes the surface of the Earth over billions of years?
A flat surface is gradually pushed up into higher and higher mountains until the Earth is covered with mountains.
High mountains gradually wear down until most of the Earth is at sea level.
High mountains gradually wear down as new mountains are continually being formed.
High mountains and flat plains stay side by side for billions of years with little change.
Mountains are constantly being thrust up by volcanic activity where one tectonic plate is subducted under another, partially melts, and then reemerges in the form of volcanoes. Mountains are also being formed where tectonic plates collide and crumple. Yet another source of mountain-building activity is the magma that wells up to fill the space between diverging plates.
But, as soon as mountains are thrust up, they are subjected to erosion by wind, water and ice. Eventually, even the hardest rocks are eventually worn down.
Question #18:
What is the most abundant element in the universe?
Hydrogen
Nitrogen
Oxygen
Silicon
Sodium
Magnesium
This question, at least, has a very straightforward answer. Hydrogen is by far the most abundant element in the Universe. If you could weigh all the atoms in existence, something like 75% of the total mass would be hydrogen. Since hydrogen atoms are also the lightest atoms (even the second-lightest of atoms, a helium atom, is 4 times heavier than a hydrogen atom), this means that well over 90% of the atoms in the Universe are hydrogen atoms. Most of the atoms in the Universe that aren’t hydrogen atoms are helium atoms.
Hydrogen and helium atoms are a direct result of the “Big Bang” that formed the Universe, which is why they’re so abundant compared to other atoms. (In fairness, a lot of the helium that currently exists was formed by nuclear fusion in the cores of stars, and not during the “Big Bang.”) Virtually every atom in the Universe heavier than helium was formed by nuclear fusion in the core of a star, some time after the “Big Bang.” Elements heavier than iron are formed in supernova explosions. (If you’re wearing any gold or silver jewelry, its atoms were formed when a star exploded billions of years ago and scattered its components into space, where they eventually became incorporated into the Earth as it was forming.)
Question #19:
When you bend your arm at the elbow, the bones and muscles in your arm are acting as a system. What simple machine does this system represent?
Inclined plane
Pulley
Wedge
Lever
A lever is one of the six fundamental types of simple machines – along with the inclined plane, the wheel and axle, the pulley, the wedge, and the screw. Specifically, a lever is a rigid body that turns around a fulcrum and that can redirect and/or magnify a force that is applied to it.
Muscles can only pull. By attaching them to rigid bones, a lever system can be set up that redirects their force; this is one of the reasons you can push objects, even though your muscles can generate only pulling forces. Depending upon the arrangement of the lever, it can also increase either the speed the muscle generates when it contracts, or the force it generates – but not both. There is always a trade-off between speed and force (properly, mechanical advantage).
In a Class 1 Lever, the fulcrum is located between the applied force (the force you apply to the lever) and the output force (the force generated when the opposite end of the lever moves). A see-saw is a familiar example of a Class 1 Lever. A Class 1 Lever always redirects a force, because the end you apply a force to always moves in the opposite direction of the end where the output force is generated. (So, if you push down on one end of a see-saw, the other end moves up.)
Depending on where the fulcrum is located, a Class 1 Lever can generate either increased speed or increased mechanical advantage. If the fulcrum is located near the output force, then the input arm is long and the output arm is short. This means the end you push on moves a great distance and the opposite end moves only a short distance in the same amount of time. This kind of lever greatly magnifies mechanical advantage at the cost of speed. A crowbar is a good example; you move the input arm a relatively great distance, with relatively great speed but little power. Since the output arm must travel its distance in the same amount of time, but travels a much shorter distance, it moves with much more power. So, a crowbar is a device for transforming speed into power. A baseball bat is just the opposite; it is a device for transforming power into speed. You move the (very short) input arm a short distance, so the much longer output arm must travel far faster in order to cover the distance it must travel in the same amount of time.
There are few examples of Class 1 Levers in your body. One of the few is the arrangement of the sternocleidomastoid muscle and the mastoid process of your skull. The mastoid process is the prominent “bump” you can feel if you press your fingers against you skull just behind your ear. That is the fulcrum. The sternocleidomastoid muscle attaches at your sternum (breastbone) and clavicle (collar bone) at one end, and to the occipital and temporal bones of the skull at the other. When it contracts and pulls downward, the mastoid process of the skull acts as a fulcrum, redirecting its force and pulling the chin upward.
In a Class 2 Lever, the output force is between the fulcrum and the applied force. A wheelbarrow is a common example of a Class 2 Lever. You apply a force by lifting one end; the fulcrum is at the opposite end, and the result is that the middle of the wheelbarrow is lifted upward. You’ll notice that a Class 2 Lever does not redirect the force. Because the applied force is always further from the fulcrum than is the output force, the output arm moves a smaller distance than the input arm, and therefore moves with less speed but more power. A Class 2 Lever is a device that sacrifices speed for power, which is why a wheelbarrow allows you to lift much heavier objects than you could lift on your own.
An example of a Class 2 Lever in your body is the gastrocnemius (calf) muscle and the bones of the foot and lower leg. The gastrocnemius is attached to the bones of the lower leg at one end, and to the calcaneus (heel) bone at the other. The bones in the forepart of the foot act as the fulcrum. When the muscle contracts, it pulls the heel up. The muscle itself moves a considerable distance (the input arm is long) in order to lift the heel a relatively short distance (the output arm is short). The result is that the force the muscle can generate is greatly magnified at the expense of its speed, and just one of your calf muscles can easily lift the entire weight of your body.
A Class 3 Lever is one in which the applied force is between the fulcrum and the output force. A Class 3 Lever is exactly the opposite of a Class 2 Lever, in that it trades power for speed. Because the applied force is closer to the fulcrum than is the output force, the output arm moves a greater distance than does the input arm. So, the output arm must move faster. A Class 3 Lever is similar to a Class 2 Lever in one sense, though; the applied force and the output force usually move in the same direction. A trebuchet is a kind of Class 3 lever, in that a great deal of power is applied to get one end moving very fast.
An example of a Class 3 Lever in your body is the biceps brachii muscle and the bones of the upper arm. The biceps brachii is attached to the shoulder bones at one end, and to the bones of the forearm at the other. The elbow is the fulcrum. When the biceps contracts, it moves a relatively short distance, while the forearm moves a much greater distance. The result is that the biceps sacrifices power for speed. (The biceps brachii typically has about a 1:6 ratio between input arm and output arm length. This means the muscle must generate 180 pounds of force in order for you to lift a 30-pound object with it.)
Question #20:
Which is the most basic unit of living things?
Cells
Bones
Tissues
Organs
This is a definitional question. The cell is defined as the “fundamental unit of life.” Every living thing is made up of at least one cell, by definition. That’s why non-cellular things like viruses (even though they behave very much like living organisms and are made of the same chemicals) aren’t considered to be alive.
Question #21:
What is the process by which plants use carbon dioxide, sunlight, and water to produce energy (and oxygen)?
Transmogrification
Transpiration
Carbon Dating
Photosynthesis
Photosynthesis is precisely the opposite of aerobic respiration. It takes energy to form chemical bonds, so when chemical bonds are broken, that energy is released and can be used. That’s why organisms break apart organic molecules (chiefly glucose) for energy in aerobic respiration. (And in anaerobic respiration too, but aerobic respiration is a far more efficient way to generate energy.)
The chemical equation for aerobic respiration looks like this: C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy
[That is, a glucose molecule is combined with 6 molecules of oxygen. The byproducts are 6 molecules of carbon dioxide and 6 molecules of water. Since the chemical bonds of the water and carbon dioxide contain less energy than did the bonds of the glucose and oxygen molecules, the “extra” energy is liberated and can be used to power an organism’s metabolism.]
But where does the glucose come from in the first place? Photosynthesis! Here’s the chemical formula – it should look pretty familiar: 6CO2 + 6H2O + energy (sunlight) --> C6H12O6 + 6O2
[That is, plants use the energy of sunlight to combine carbon dioxide and water to form glucose, releasing excess oxygen as a waste product. The glucose thus acts as an energy-storage molecule, which the plant can break down whenever it needs energy. Unless, of course, some nasty animal comes along and eats it first.]
Question #22:
How are warm-blooded animals different from cold-blooded animals?
Warm-blooded animals have a higher metabolism in warm weather
Warm-blooded animals are more aggressive in captivity.
Warm-blooded animals always have a higher blood temperature.
Warm-blooded animals normally maintain a fairly constant internal temperature at all air temperatures.
Warm-blooded animals are found only in warm climates.
The real world can be complicated. What most people mean when they say an animal is “warm-blooded” is that it can maintain a relatively high and fairly constant internal body temperature through metabolic action, over a wide range of air temperatures.
But, in fact, the body temperatures of many “warm-blooded” animals fluctuate quite a bit during the course of a normal day. Heck, many “warm-blooded” animals don’t even regulate all the parts of their own bodies at the same temperature – for instance, the lower leg of a caribou may be only a few degrees above freezing while its core body temperature is 60 degrees Fahrenheit warmer.
Some “cold-blooded” animals can raise their body temperatures to well above that of the surrounding air or water – Leatherback Sea Turtles, for example, and Great White Sharks. Even some moths can raise their body temperatures to well above that of the surrounding air.
The terms “warm-blooded” and “cold-blooded” are rarely used by serious zoologists, because they’re so imprecise.
An animal that can generate significant amounts of body heat metabolically is an endotherm. If it can maintain a more or less constant body temperature despite the temperature of its surroundings, it’s a homeotherm. Thus, most mammals, for example, are endothermic homeotherms. A Great White Shark is endothermic, but it is not homeothermic.
An animal that cannot raise its body temperature significantly above that of its surroundings through metabolic activity is an ectotherm. If it cannot maintain a more or less constant body temperature in the face of varying environmental temperatures, it is a poikilotherm. Your average snake or lizard is an ectothermic poikilotherm. Many bats and small birds, though endotherms, are poikilothermic, at least at night.
Question #23:
Which is made with the help of bacteria?
Yogurt
Cream
Soap
Cooking oil
Yogurt is fermented milk. Bacteria in the milk, usually Streptococcus salivarius and Lactobacillus delbrueckii digest the milk sugar lactose anaerobically, producing lactic acid as a waste product. The lactic acid causes milk proteins to denature and change shape, thus the milk congeals into yogurt. The lactic acid also gives yogurt its sour taste.
Question #24:
If a neutral atom loses an electron, what is formed?
A gas
An ion
An acid
A molecule
This is more or less a definitional question, though the question is actually worded a bit problematically. An atom is electrically neutral by definition. If it ain’t electrically neutral, it ain’t an atom. Thus, “neutral atom” is a redundancy.
This is true because an atom contains equal numbers of positively-charged protons in its nucleus and negatively-charged electrons “orbiting” the nucleus in orbitals. If the atom gains one or more electrons, it now has more negatively-charged electrons than positively-charged protons, and so becomes negatively charged. (And is no longer an atom.) If it loses one or more electrons, it now has more protons than electrons, and so is positively-charged. (And again, is no longer an atom.)
An atom that acquires an electrical charge by gaining or losing electrons is known as an ion.
Question #25:
Which is NOT an example of a chemical change?
Boiling water
Rusting iron
Burning wood
Baking bread
A chemical reaction occurs when atoms and/or molecules combine or recombine to form new chemical substances with chemical properties different from the original substances.
When you burn wood, you’re combining the molecules of the wood with oxygen. The byproducts are carbon dioxide, water, and a range of other chemicals.
When iron rusts, iron atoms combine chemically with oxygen in the presence of water to form hydrated iron oxides.
When you bake bread, chemical reactions release carbon dioxide, causing the bread to rise. This is due either to anaerobic respiration of sugar in the bread dough by yeast cells (a type of fungus) producing CO2 and ethyl alcohol as waste products (the ethanol evaporates during baking), or due to chemical reactions from baking powder releasing CO2. Baking powder contains dry compounds that form both acids (calcium phosphate, for example) and bases (sodium bicarbonate, for example) when wetted. The chemical reaction between the acids and bases releases CO2 so that the bread rises.
Among other chemical reactions that are likely to occur when you bake bread, the heat of the oven causes oxygen to combine chemically with sugars in the bread. This results in carmelization of those sugars, which causes the crust (where the heat is most intense) to harden and turn brown.
Boiling water, on the other hand, does not involve changing water molecules into any other sorts of molecules. When you boil water, you’re simply adding enough energy to the water that the water molecules no longer stick together, and so it transforms from a liquid into a gas.
Question #26:
Which of the following is a gaseous planet?
Mars
Jupiter
Venus
Mercury
Mars, Venus and Mercury (and Earth) are made mostly of rock and metals. They’re called “terrestrial planets.” Jupiter, Saturn, Uranus and Neptune are made largely of compressed gases, and are often called “gas giants” as a consequence.
Jupiter and Saturn are made mostly of compressed hydrogen and helium, and are properly classified as “Jovian planets.” Uranus and Neptune are much smaller (though still quite a lot bigger than any of the terrestrial planets); they contain relatively smaller amounts of hydrogen and helium, and relatively larger amounts of ices. (To astronomers, an “ice” is the frozen form of any small molecular-weight substance that is a liquid or a gas at standard temperatures and pressures.) Uranus and Neptune consist largely of water, methane, and ammonia ices, in addition to compressed hydrogen and helium gas – as such, they’re sometimes called “Uranian planets” or “ice giants.”
Cheers,
Michael
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