ASVAB GENERAL SCIENCE

To get a better idea of how the scientific classification system works, The picture shows you how a few species are classified.

(Picture) Taxonomy of Different Organisms

5. The nasal cavity is part of which system? (A) respiratory (B) cardiac (C) muscular (D) lymphatic

A. The nasal cavity, where air enters your body, is part of the respiratory system. Other parts of this system include the nose, lungs, and trachea.

1. A cell nucleus is often referred to as the (A) control center. (B) cytoskeleton. (C) cell membrane. (D) chromosome.

A. The nucleus contains most of the cell's genetic material and is often referred to as the control center of the cell, so the correct answer is Choice (A).

Visiting the kingdoms part 1 Most scientists agree that there are five or six kingdoms. Check out the kinds of organisms that fall under each: Each organism is given a scientific name that consists of two words (usually derived from Latin) — the genus and the species of the organism. The genus is the first word, and the species is the second. Thus, Homo sapiens refers to humans. Canis familiaris is the family dog, and Canis lupus is the family wolf. Because wolves and dogs share many similarities, they share the same genus (no, no, not the same genes, the same genus).

Animals: This is one of the two largest kingdoms, and it includes many-celled organisms that, unlike plants, don't have cell walls, chlorophyll, or the capacity to use light to make energy (photosynthesis). Members of this kingdom can move. The Animal kingdom includes more than one million species. (Check out Figure for a better look at cells.)

3. Proteins come from all the following sources except (A) beans. (B) water. (C) meat. (D) eggs.

B. Beans, meat, and eggs all contain protein necessary for body functions, but water doesn't. That makes Choice (B) the right answer.

10. Where would you find a hinge joint in the human body? (A) the neck (B) the elbow (C) the hip (D) the toes

B. Hinge joints are found at the elbows and knees, and they allow bones to move back and forth (like a door that opens and closes).

9. Most cells reproduce by (A) meiosis. (B) mitosis. (C) photosynthesis. (D) osmosis.

B. Most cells reproduce by mitosis, the process of dividing into two separate cells with identical DNA, so Choice (B) is correct. By contrast, meiosis is the process of cells separating into four separate cells. Photosynthesis refers to plants making energy from light, and osmosis is the transfer of liquid between cell walls.

6. The gram is a unit of (A) liquid measurement. (B) mass. (C) distance. (D) temperature.

B. The gram is a unit of mass in the metric system, making Choice (B) the only right answer.

Nucleus: The nucleus (plural nuclei) controls cellular activity. It's like the brains behind the cell, and it holds the cell's genetic material — DNA.

Bacteria are prokaryotes, which means their cells don't have nuclei. Their genetic material floats in the cytoplasm instead of being held inside a membrane (nuclear envelope).

Understanding Forms of Measurement

Because science is based on developing objective facts — evidence and results that are measurable and experiments that can be reproduced — measurements are an important part of science. And because this subtest is all about science, you can expect to run into a few questions about measuring scientifically on the ASVAB. The metric system, or SI (abbreviated for the French le Système International d'Unités, which translates to the International System of Units), is based on a decimal system of multiples and fractions of ten. Scientists almost always use the metric system for precise measurement so a standard exists among scientists around the world. In fact, the majority of countries around the globe use the metric system — the United States is one of the few countries countries that still teach and use the Imperial (non-metric) system.

Variety is the spice of life: Biodiversity

Biodiversity is the term scientists use to talk about the variety of life in the world-at-large or in specific habitats and ecosystems. Scientists have already named and classified just under 2 million species of plants and animals, but experts suspect between 8 and 10 million haven't been discovered yet. Every species has an important role to play in natural sustainability, from the smallest bacterium to the biggest animal. The continuation of life on this planet depends on biodiversity; if one species that was food for another species dies out, it creates a domino effect that disrupts the entire food chain (all the way up to humans). It's not only about food, though. It's also about depending on other organisms to perform functions that keep the world turning (such as bees pollinating plants or big trees taking carbon dioxide out of the air and replacing it with oxygen). When any species has good genetic diversity, it has a larger gene pool to pull from during the process of evolution — and that makes organisms more adaptable to changing conditions over time so species can survive. About 40 percent of the medicines we use today come from natural compounds in plants, fungi, and animals, too. Biodiversity is nature's checks-and-balances system, and without it, conditions for every species on Earth would quickly go downhill.

8. In the term Homo sapiens, the word sapiens describes the organism's (A) genus. (B) domain. (C) species. (D) phylum.

C. Species is the most specific classification in the Linnaean taxonomic system, and sapiens is a species. Domain is the broadest, and phylum and genus are between the two. (Homo in this question is the genus.)

2. The human circulatory system (A) uses air to release energy. (B) processes food and eliminates waste. (C) moves oxygenated blood throughout the body. (D) controls movement of joints.

C. The respiratory system uses air to release energy, the digestive system processes food and eliminates waste, and the musculoskeletal system controls the movement of joints. The correct answer is Choice (C).

7. The first step in the scientific method is to (A) ask questions. (B) test hypotheses. (C) make observations. (D) create a theory.

C. The scientific method starts with observation. Scientists then ask questions, develop a hypothesis, make predictions about what will happen, and test the hypothesis.

Operating condition In order to work properly (so all those functions can keep on keepin' on), your body needs plenty of fuel — and that comes in the form of food, vitamins, minerals, and water. You need the following:

Carbohydrates for energy: Carbohydrates come from starches and sugars, such as bread, pasta, fruit, and candy bars. Fats for energy: Too much fat is bad, but you do need some in your diet. Fats fall into three categories: saturated, monounsaturated, and polyunsaturated. Polyunsaturated fats are required for normal body functions, but your body can't make them, so you have to eat foods that contain them (such as many vegetable oils, walnuts, and some fish). Saturated fats come from meat, shellfish, eggs, and dairy. Monounsaturated fats come from olives, avocados, and some nuts. Fiber for getting rid of waste products: Leafy green vegetables, beans, potatoes, and fruits have plenty of fiber. Minerals for various bodily functions: A few necessary minerals include iron to develop red blood cells, calcium to keep your bones strong, and potassium to keep your heart's electrical activity in check. A well-balanced diet ensures you're getting the minerals you need, but some people need supplements. Protein for growth, maintenance, and repair: Humans consume protein through meat, fish, beans, nuts, and a handful of other sources. Vitamins for various bodily functions: You can usually get all the 13 essential vitamins from fruits, veggies, and the sun. Your body uses them for things such as blood clotting, processing food, and regulating your hormones. Water to keep your cells from shriveling up and withering away: Most foods contain water, but you still need to drink water as well. Humans lose about four pints of water each day, and you have to replace it or face serious health consequences, such as headaches, cramps, and even death.

Animals can't produce their own food, so they're consumers, which are classified in three categories:

Carnivores eat only meat. Some examples include lions, tigers, polar bears, snakes, crocodiles, hawks, and eagles. Herbivores eat only plants. Cows, moose, giraffes, and elk are herbivores. Omnivores eat both plants and other animals. People are omnivores, and so are pigs, mice, raccoons, chickens, crows, and foxes. Conditions in the world either encourage or prevent the establishment of individual ecosystems. For plants (producers) to grow, adequate sunlight, good soil, moderate temperatures, and water must be part of the environment. If plants aren't around, plant-eating consumers can't be sustained, which means predators (who eat other animals) can't be sustained, either. For consumers, mates are as essential as a food supply. Diseases and enemies can prevent an animal from establishing itself in an ecosystem. Human actions, such as wasting natural resources and polluting the air, water, or soil, can disrupt or destroy an entire ecosystem.

Compounds, mixtures, and reactions: When elements get together Elements that combine can join together in specific ratios, mix and mingle in different ratios, or react to each other to create different substances.

Compounds: Adding elements together Compounds are elements that have joined by chemical bonds in a specific ratio. The water that comes out of your tap is a compound made of two elements: hydrogen (represented by H in the periodic table) and oxygen (represented by O in the periodic table). These elements together make water if they're combined only in a very specific way: two hydrogen atoms for every one oxygen atom (that's why you see the compound written as ). The little number 2 between the two elements tells you the compound has two hydrogen atoms; because there's no number after the O, you can assume that the compound has just one of them.

4. Animals that eat only plants are called (A) vegivores. (B) carnivores. (C) omnivores. (D) herbivores.

D. An herbivore is an animal that eats only plants, so Choice (D) is correct. Carnivores eat meat, and omnivores eat both meat and plants. (And for the record, vegivores aren't a thing.)

Counting down the classification system The scientific classification system notes the relationships and similarities among organisms. It consists of eight main levels:

Domain: A domain is a group of organisms that are similar based on characteristics such as chemistry and cell structure. The three domains are the broadest classifications and include the most kinds of organisms. Kingdom: Kingdoms group organisms by developmental characteristics and whether they make their own food. The relationships between organisms in a kingdom can be extremely loose, so members may share only a few characteristics. According to scientists, five or six kingdoms exist. Phylum: Phylum (plural phyla) is the next major taxonomic group. Within the kingdoms, organisms are divided into 36 phyla by general characteristics. For example, in the Animal kingdom, animals with backbones (vertebrates) are placed in a separate phylum from animals without backbones. Class: Organisms in a phylum are divided into classes. In the Animal kingdom, for example, birds, mammals, and fish all go in their own classes. Among plants, all flowering plants comprise the Angiosperm class, and all trees that bear cones, such as pines and spruces, comprise the Conifer class. Order: Scientific groupings create orders, which separate organisms based on the characteristics of the major groups in their class. For example, humans, chimps, gorillas, and gibbons are all part of the order Primate because they all share large brains and opposable thumbs, use tools, and have social social groups. The order Rodentia includes gnawing mammals with continuously growing teeth, like squirrels, hamsters, and rats. Family: Families further divide organisms of the same order by similar characteristics. For example, humans are part of the Hominidae family, where gibbons split off into their own family: Hylobatidae. Genus: Two or more species that share unique body structures or other characteristics are closely related enough to be placed in a single genus. A genus may include only a single species if no other organism has characteristics similar enough for it to be considered the same genus. Here's where humans split from gorillas; we're part of the genus Homo, while they're in the genus Gorilla. Species: A species is the most specific level, so it contains the fewest types of organisms. Organisms of the same species have very similar characteristics. The human species is sapiens, while a gorilla's species is gorilla (and yes, that means they're classified as Gorilla gorilla, gorilla, because species are conventionally written with the genus and the species together).

Understanding the elements. The atom is the smallest part of an element that still retains the characteristics of that element. Every atom has particles — pieces of matter that are very, very small. Electrons are negatively charged particles that float around the atom's nucleus, or core, which is made up of neutrons (particles with no charge) and protons (positively charged particles).

Each element has its own atomic number that's equal to the number of protons it has. If an atom has one proton in its nucleus, it has the atomic number 1. Hydrogen is the only element with just one proton in its nucleus. Magnesium, which has 12 protons in its nucleus, is given the atomic number 12. Atoms can combine with each other to form molecules. If those atoms are of two or more different elements, the molecule is called a compound. A compound can have very different properties from the elements that make it up. For example, table salt, which is mostly harmless, consists of two lethal elements — sodium and chlorine. But when combined, these elements make a compound that people ingest every day: salt.

Covering all the bases (and the acids, too) Aqueous chemical compounds, substances, and mixtures (those that contain water) can be bases, acids, or neutral (neither an acid nor a base). A base is a substance that gives up negatively charged hydroxyl ions when dissolved in water; they're often called alkaline substances. Liquid soap, ammonia, and baking soda are all bases. An acid gives up positively charged hydrogen ions when dissolved in water. Some examples of acids include vinegar, orange juice, and sulfuric acid. Whether a solution is basic or acidic, it can be measured on a pH scale. The pH scale ranges from 0 to 14, with 0 being the most acidic (that's where you find battery acid) and 14 being the most basic (that's where liquid drain cleaner hangs out). Pure water falls right in the middle, at a very neutral 7. The Image shows the pH scale with common household substances on it.

Each whole pH value below 7 — the most neutral number on the scale — is ten times more acidic than the value after it. That means something with a pH of 3 is 10 times more acidic than something with a pH of 4 and 100 times more acidic than something with a pH of 5. pH stands for the Latin potentia hydrogenii — in English, potential hydrogen. The scale is based on the logarithm , where log is the base 10 logarithm and H+ is the hydrogen ion concentration measured in moles per liter.

Relating to your world through ecology

Ecology is the study of the environment — more specifically, the relationship between organisms and the world around them. All plants and animals are part of an ecosystem (a biological community of interacting organisms and their environment). An ecosystem includes producers that make their own food and consumers that eat other things. An ecosystem also has decomposers, such as bacteria, that break down dead plants, animals, and the waste of all organisms.

The anatomy of a plant. A plant's stem is technically part of its shoot system, but it has several big jobs. It moves water and nutrients between roots and leaves, holds the plant upright so it can grow taller (and access more sun so it can grow even taller), and redirects the plant's growth. Plants make their own food through photosynthesis, which takes place in the leaves. All they need are carbon dioxide, water, and sunlight. Photosynthesis occurs in two stages: light-dependent reactions and the Calvin cycle. Light-dependent reactions happen when chlorophyll (the chemical substance that makes plants green) and other pigments absorb energy from sunlight. The energy splits water molecules into hydrogen and oxygen and the oxygen evaporates into the atmosphere when temperatures heat up. The hydrogen that's left behind combines with carbon dioxide the plant absorbs to form glucose — that's what plants "eat." The Calvin cycle is a series of chemical reactions that take place during photosynthesis. These reactions can only happen after the plant has captured energy from sunlight.

Every living organism on earth is carbon-based. Carbon atoms form the backbone of nearly every molecule that makes up creatures and plants that can live in Earth's environment. Carbon, as an element, is really, really good at bonding to other elements. It's so good that it can bond with itself to create long carbon chains and rings — and without it, DNA wouldn't be possible.

Radiation doesn't require particles to carry thermal energy. Instead, it uses infrared waves (see Figure 11-6 earlier in the chapter), which radiate out in all directions and travel at the speed of light until they hit something else. When the waves hit an object, the object can absorb or reflect the thermal energy they carry.

Fire uses all three methods of heat transfer. First, the substance that's burning uses conduction; the moving particles make other particles in nearby solids hot enough to catch (and stay) on fire. Convection heats the air above and around the fire, and you warm your hands near the flames because of radiant heat transfer.

General and Life Science Practice Questions

General science and life science are both broad topics. To score well on this subtest, you pretty much have to wade through the textbooks and memorize the facts. See how well you do on the following 10 practice questions.

Perusing the Human Body Systems Your body consists of several major systems that work together to keep you alive. (And staying alive is a good thing, so be sure to thank your circulatory system and all the rest!) These systems include the ones listed in The picture and described in the following sections.

Human Body Systems Your nervous system is at the wheel, controlling everything that happens in your body. Your cardiovascular system pumps blood to spread oxygen to all your organs and tissues — but it couldn't do that if your respiratory system wasn't bringing in the oxygen in the first place. Your musculoskeletal system enables you to keep bringing in food by eating, and your digestive system turns the food into fuel for your nervous system (and all your other systems). Some of these functions are involuntary, like breathing and pumping blood through your body. Others, such as eating, running, and scratching the itch on your foot, are voluntary — they require you to actively choose to do something (even if it happens within a split second) and then act on your impulse. When your nervous system takes in stimuli (either through one of your external senses or through an internal stimulus, like hunger), it kicks into high gear. It sends chemical and electrical signals out to the organs that need to participate in what's happening next, and they take action.

The lymphatic system: The body's lymphatic and immune systems include lymph (a fluid that contains white blood cells that fight infection). These systems can fight off many bacteria and viruses, which are everywhere. Bacteria are single-celled organisms that cause illnesses such as pneumonia and staph infections, and viruses cause illnesses like colds and HIV. The bacteria and viruses that cause diseases evolve — sometimes very quickly, such as when antibiotic resistance pops up — and the lymphatic system responds quickly to new challenges from newly evolved organisms. Antibiotics can be used to treat bacterial infections, but they don't work on viruses. Scientists have had a tough time defeating most viruses, except through prevention by way of vaccines. Vaccinations prevent disease and pick up where the immune system leaves off.

Human bodies are always in a balancing act between staying healthy and falling apart. Some illnesses and diseases are caused by diet and lifestyle, so they're preventable. Others are genetic and ingrained in DNA. Still others come through pathogens, such as bacteria and viruses; sometimes these illnesses and diseases are preventable, too. Disease-carrying organisms are called vectors, and they include mosquitoes, rats, and ticks.

Keeping track with SI units of measurement Scientists around the world need a common language to share and explain their discoveries, so they use SI units of measurement. The Image shows the base quantities, names, and abbreviations that physicists and other scientists use to communicate.

Image Measurement, SI Base Quantities, and Abbreviations

SI derived units are measurements you can get by using a system of equations. The Image shows the most common measurements, SI derived units, and the abbreviations and symbols that represent them.

Image Measurements, SI Derived Units, and Symbols/Abbreviations

Swimming in the Gene Pool: Genetics You might have your grandma's eyes, your great-grandpa's nose, or your great-great-grandfather's height. Whether you like it or not, it happens because parents pass their traits on to their offspring. Understanding genetics — how traits are physically passed from parents to offspring and what happens when the process goes wrong — helps scientists pinpoint the causes of diseases and disorders and can help them develop treatments and cures.

In human genetics, a healthy person has 23 pairs of chromosomes (the structure that contains the genes). The mother and the father each supply one chromosome per pair. Genes contained in the chromosomes determine many characteristics of the resulting child.

IN THIS CHAPTER Figuring out the scientific method Grasping measurements Examining human and plant biology Considering cell structures and processes Getting into genetics Using scientific strategies to improve your score

Instead of trying to remember nine million individual facts, spend some time reviewing the general principles behind the facts. Think about how the facts relate to each other. Looking at the big picture is an effective learning technique.

Uncovering Biology, from Big to Small

It would be impossible to cover all the areas of biology in this book, and I'm not going to try. Luckily, the General Science subtest of the ASVAB measures your knowledge of scientific disciplines at the average high school level. You remember studying the Animal kingdom, the human body, plant physiology, and cell structures in high school, right? If not, the following sections can serve as a short refresher course.

Profiting from cell processes Cells perform various processes to function at an optimum level. Here are a few of these processes:

Metabolism: Chemical processes within a cell that are necessary to maintain life Osmosis: Movement of liquid through the cell membrane (and the main way that water goes in and out of cells) Phagocytosis: Acquisition of particles of material from outside the cell; it's accomplished by surrounding the particles and passing them through the cell membrane Photosynthesis: Conversion of light energy from the sun to chemical energy that the cell can use Cellular respiration: Process in which biochemical energy from nutrients turns into products the cell can use; one of the ways a cell releases chemical energy to fuel its activity

Boiling and freezing When you're making spaghetti for dinner, the first thing you do is boil a pot of water so you have an environment that's hot enough to change the spaghetti from a very solid piece of pasta to a softer (and much tastier) piece of pasta without catching it on fire. You eat the pasta while it's transitioning between states; it's still a solid, but it's a much softer solid. If you leave the pasta in boiling water for too long, it'll turn into mush and eventually become a liquid. Heating water changes its state. The molecules begin to move faster as they absorb heat, and the temperature rises until water reaches its boiling point. (Water's boiling point varies based on atmospheric pressure, but if you're at sea level, it's 100 degrees Celsius or 212 degrees Fahrenheit.) The temperature stays constant until all the liquid evaporates into a gas (water turns into steam). Steam contains the same molecules water does ,(H2O) but in each state, the molecules are at different distances and moving at different speeds. Cooling water changes its state, too. Condensation — the process of a substance changing from a gas to a liquid — is the first phase change liquids go through as they cool; it's the opposite of evaporation. When your glasses fog up when you open the dishwasher, when you see dew on the grass in the morning, or when your cup of cold liquid "sweats" on a hot day, you're watching liquids condense. These events happen because your glasses, the ground, and your cup are colder than the environment they're in; they cause water molecules in the air to gather together and form a liquid. Freezing is another way to change a molecule's state. The molecule's freezing point is the same as its melting point; it's just that the thermostat is moving in the opposite direction. Cooling a substance slows down the motion of its molecules until it becomes a solid.

Most substances go through the same progression of events to change states, but some elements go through the process of sublimation instead. Sublimation occurs when a substance goes directly from a solid state to a gaseous state with no liquid state in-between. One example is dry ice. Dry ice is solid carbon dioxide, and it's often used to create a smoke or fog effect in magic shows (and nightclubs). Dry ice turns into a colorless gas, but it creates a white cloud as it evaporates (the white cloud it forms is actually condensation of water vapor in the air because the dry ice is so cold). The reverse of sublimation is called deposition, where a gaseous substance becomes a solid without a liquid state in-between.

The words law and theory don't mean the same things to scientists that they mean to the average person. Theories can evolve over time as new information becomes available, but they're pretty much accepted as true across the scientific community. Laws, on the other hand, are always true (that's why there are few laws and many theories), and they're often expressed in a simple statement.

Newton's first law of motion Newton's first law of motion says that an object at rest tends to stay at rest, and an object in motion tends to stay in motion with the same speed and in the same direction, unless acted upon by an unbalanced force. What that means is that without friction to slow down a moving object (and nothing to knock the object off its path), the object would keep going the same speed, on the same path. Newton's first law, which is sometimes called the law of inertia, basically means that objects tend to keep doing what they're doing unless something interrupts them. Inertia means a tendency to do nothing or to remain unchanged, and all matter resists changes in motion. The key phrase in Newton's first law is unbalanced force. The first law of motion only works if forces are balanced — that is, if there's nothing to change the object's course. In that case, the object is in a state of equilibrium (the condition in which all forces balance) and won't accelerate, decelerate, or change course. You've probably experienced the law of inertia yourself. When you're in the car with a hot cup of coffee and the driver hits the brakes, your coffee keeps moving in the same direction it's been moving the entire time you've been in the car, at the same speed (so you'd better have the lid on tight). The same is true for you; if you're in a crash and the car stops abruptly, you keep going in the same direction at the same speed (and right through the windshield, if you're not wearing a seat belt that acts as an unbalanced force to stop you). Sometimes other forces, such as gravity, also act on objects. That's why when you throw a baseball from left field to first base, it follows an upward path but begins to drop by the time it (hopefully) reaches the first baseman, and why when you fire your M4 carbine at a 300-meter target, the bullet hits a little lower than it would've if you'd been firing at a 50-meter target.

There's a Scientific Method to the Madness Scientists are pretty skeptical. They don't necessarily believe anything said by anyone else unless it's been shown to be true (time after time after time) using a process called the scientific method. Scientists know that personal and cultural biases may influence perceptions and interpretations of data, so they've derived a standard set of procedures and criteria to minimize those influences when developing a theory. Because the scientific method is prevalent in all fields of science, you can expect to see a few questions about the process on the General Science subtest. Here are the usual steps to solving a problem using the scientific method:

Observe some aspect of the universe. Ask a question about why this thing is happening. Develop a testable explanation (hypothesis) based on the theory. Make a prediction based on the hypothesis. Experiment and observe to test the prediction. Use the results of the experiment to create new hypotheses or predictions.

Bryophytes are plants that don't have a vascular system and don't produce flowers or seeds. They reproduce by releasing spores. Lichen, liverwort, and many types of mosses are bryophytes.

Plant reproduction Bryophytes and ferns reproduce sexually and asexually. They use spores, which contain male and female reproductive organs. Fertilization occurs before the plant ever releases a spore. After a plant releases a spore, the spore can grow where it lands (as long as conditions are right). Scientists believe that all plants were once spore-bearing, and only after plants evolved and adapted to live on land did they begin to form seeds.

Gymnosperms are plants that produce cones and seeds rather than flowers, and they have vascular tissue, too. Your Christmas tree is a gymnosperm, as are California's giant sequoias and most non-flowering shrubs.

Plant reproduction Gymnosperms sexually reproduce in ways similar to angiosperms. They produce naked seeds — seeds that aren't wrapped in a fruit or seed pod — that develop on the upper surfaces of cone scales (pine trees are gymnosperms, and pine cones are where seeds develop). Wind carries the seeds where they need to be for fertilization.

Angiosperms are flowering plants. These plants have vascular tissue (tissue that transports fluid and nutrients internally, which is similar to human veins) and produce flowers and seeds. Angiosperms include roses and all the flowers in your garden; palm trees; and apple trees.

Plant reproduction Angiosperms are the most advanced types of plants when it comes to sexual reproduction. They create flowers that contain stigma, which produces pollen, and carpels, which catch pollen. A bug, a bird, or even the wind can pick up pollen from one flower and deposit it on the stigma of the same species (or on another stigma of the same plant). Each particle of pollen grain contains sperm that fertilizes an ovule (egg) in the flower.

Visiting the kingdoms Part 2 Most scientists agree that there are five or six kingdoms. Check out the kinds of organisms that fall under each:

Plants: Plants are also one of the two largest kingdoms. This kingdom includes organisms that can't move, don't have obvious nervous or sensory systems (the Venus flytrap is one exception), and possess cell walls made of cellulose. More than 250,000 species belong to the Plant kingdom. Fungi: Examples of common fungi are mushrooms and yeast. Fungi don't photosynthesize (use light to create energy) like plants do, but they do have cell walls made of a carbohydrate called chitin. More than 100,000 species belong to the Fungi kingdom. Protists: Protists include one-celled organisms that do have a nucleus, such as the protozoan, which you may remember from biology class. This kingdom consists of more than 250,000 species. Eubacteria: This kingdom, which used to be considered Monerans, is made up of single-celled organisms that don't have distinct nuclei or organelles (small, specialized structures within cells that act like organs). Bacteria are found everywhere, including your body and the depths of the ocean. Archaebacteria: Archaea is a kingdom comprising single-celled organisms that have no distinct nuclei or organelles; they have different genetic structures and metabolic processes than bacteria do.

Understanding sound waves Your favorite song, the bell ringing before class starts, and your mom reminding you to pick up your room all travel to your ears through sound waves. Sound waves are actually fast-moving waves of pressure that result in the vibrations of particles in the medium carrying them (most of the time, that's air). If you bang on a drum, you're causing the drum's tight surface to vibrate. In turn, that makes the air around the drum vibrate, sending energy out of the drum in all directions. When the vibrating air hits your eardrums, you perceive it as a sound; you're hearing energy making a journey. If that vibrating air hits a wall or another surface, it bounces back in the form of an echo, which is technically called sound reflection.

Sound waves travel very quickly. At sea level, they speed through the air at about 760 miles per hour. When you hear about ultra-fast jets breaking the sound barrier, that means the jet is accelerating so quickly that it goes faster than the sound waves it's creating. The result is a sonic boom — a tremendous, explosion-like sound caused by the shock waves the jet makes.

Solids have particles or molecules that are close together and don't move much, and they have a definite shape. In many cases, that's because the molecules are bound together in a very rigid structure of repeating patterns. The structure is called crystal lattice. The molecules are still moving, but not much. Liquids have particles that are a bit more spread out than they are in solids. The big difference? They move around a lot more. Liquids don't have definite shapes, but they do have a definite volume. (Picture one cup of orange juice in a plastic box and one cup of orange juice in a coffee mug. They both have the same volume — one cup — but they definitely have different shapes.) Gases have particles that are much more spread out than they are in solids or liquids, and they move faster, too. Gases have no definite shape and no definite volume. The molecules move independently of one another, so gases expand to fill the area that contains them. You can compress gases (such as in a SCUBA tank) or release them (like when you turn the knob and release the gas from the same SCUBA tank).

States Of Matter/ See Image Matter can — and does — change states. It usually takes extreme conditions to change the state of matter, like boiling or freezing. For example, an ice cube is a solid, but it quickly becomes a liquid when you leave it on the sidewalk in the sun. Soon after that, it evaporates into a gas. As molecules heat up, they move more quickly and become more spread out.

As you read a chemical formula, you have to deal with molecules and compounds in shorthand. The number of molecules is listed in front of the molecule, so you write "five molecules of helium" as "5He." You write the number of atoms in a molecule in subscript after the elemental symbol, so hydrogen with two atoms is H2. Sometimes formulas have brackets, just like algebraic formulas do, to separate them when they're complex. The Table gives you examples of how to read chemical formulas. Use Image (the periodic table) earlier in the chapter to figure out which elements are in each compound.

The ASVAB may dish up a question or two that asks you to identify one (or more) of the components of a chemical formula. Though you don't have to memorize the symbols for each element, knowing how formulas work (and how to break them apart) can help boost your score. If you think of atoms like LEGO blocks that you can arrange into different structures (and make parts for an even bigger structure), you can visualize the letters and numbers inside brackets as parts that can be added to other molecules. Those parts are called functional groups. Like atoms, you indicate how many of these groups there are with the subscript number(NO3). means that there are three(NO3) functional groups. Here's an example: I always add two (sometimes more) teaspoons of good, old-fashioned (C12-H22-O11) (that's sugar) to my coffee in the morning. Look at Image 11-2 earlier in the chapter. Based on sugar's molecular formula, you can tell that it has 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms in each molecule. These three elements together, in this ratio only, make up sugar. If one is off, even by one atom, my coffee would taste a lot different (and may even be toxic). Acetone, which removes paint, serves as an ingredient in rubber cement, and does a bunch of other non-food-related tasks, is also made up of carbon, hydrogen, and oxygen. (In case you were wondering, acetone's chemical makeup is (CH3) O, and it's nasty in coffee.)

If the classification system gets you mixed up, try the mnemonic "Dear King Phillip, come over for good spaghetti." The first letter of each word represents part of the classification system, in order from broadest (domain) to most narrow (species). (See picture) shows you the taxonomic system in action.

The Linnaean taxonomic classification system. Picture

Measuring work, force, energy, and power Physicists define work as far more than "showing up at the right place at the right time in the right uniform" (you hear that phrase often in the military). To a physicist, a force performs work on an object when it causes the object to move. You can calculate the work performed on an object by multiplying the force by how much the object object moves. The equation for work is , where W represents work, F represents force, and d represents displacement. Units of work are measured in newton-meters (Nm) or joules (J) under the SI system, but under the U.S. system, they're measured in pounds. Force is something that causes a change in an object's motion, such as a push or pull resulting from the object's interaction with another object. It can refer to gravity, pushing against something with your muscles, or smashing into something with a car; it's anything that takes away an object's inertia. Forces only exist as a result of an interaction between two objects, and it's typically measured in pounds (lbs.).

The SI system is used in most of the world, but in the U.S., many common applications (and most engineering functions) use U.S. Standard Units. You may see either system on the ASVAB, which is designed to test the depth of your existing knowledge, but what you won't see is a mixture of the two systems in the same problem. Table 11-4 highlights some of the key differences between them.

Determining your sex with two little letters The genes on one pair of chromosomes, called the sex chromosomes, determine whether a child will be male or female. In females, the two sex chromosomes are alike, and they're labeled XX. In males, the chromosomes are different and are labeled XY.

The child always receives an X chromosome from the mother (who only has XX chromosomes). The father (who has XY chromosomes) can contribute either an X or a Y chromosome, so Papa actually determines the sex of the child.

Flowing through the heart, blood, and circulatory system When you donate blood, or when someone donates it to you, your blood types need to match. The exceptions to this rule are Type O negative and Type AB positive. Type O negative blood is considered the universal donor; it can be donated to anyone. Type AB positive is the universal recipient, which means a person with this blood type can receive any other kind of blood.

The circulatory system keeps blood with oxygen and nutrients flowing to all your organs so they continue to work. At its core is the heart, a four-chambered organ that contracts and relaxes several times each minute. Two chambers collect blood coming in (each is called an atrium, but together, they're atria), and two, called ventricles, pump it back out. Heart valves close after blood leaves, preventing it from coming back in the Exit door. When blood leaves the heart, it rushes through arteries — the largest and thickest tunnels in the circulatory system. These blood-carrying tubes have to be thick and strong, because the heart pumps out oxygenated blood fast, which creates a lot of pressure. Arteries branch out several times (each branch is called an arteriole) to send blood into the tissues through tiny tunnels called capillaries. Capillaries let out oxygen and nutrients while they take in carbon dioxide and waste in a process called diffusion (arteries and veins don't). Veins carry blood back to the heart, and they don't have thick walls because they don't need them; when blood makes its return trip, it's not under a lot of pressure to get there quickly. The blood going back to the heart is dark red because it's deoxygenated (it drops off all its oxygen to organs and systems when it travels from the heart). Blood is made up of cells suspended in plasma. Red blood cells carry oxygen, white blood cells fight infection, and platelets are pieces of cells that cause blood to clot. The cells for blood are made in bone marrow (the spongy stuff inside the cavities of bones). Types A, B, AB, and O are all the types of blood, which can be positive or negative.

The rainbow of frequencies on the electromagnetic spectrum Visible light is only one part of the electromagnetic spectrum (shown in Figure 11-6), which covers all the wavelengths and frequencies of radiation. Radiation that produces long wavelengths and low frequencies falls on one side of the electromagnetic spectrum, while radiation that produces short wavelengths and high frequencies falls on the other.

The electromagnetic spectrum. On the electromagnetic spectrum, wavelengths are measured by the distance from the peak of one wave to the peak of the next wave. They're measured in kilometers (km), meters (m), centimeters (cm), millimeters (mm), and nanometers (nm). Frequencies are measured by how many waves occur per second, in hertz (Hz), kilohertz (kHz), megahertz (MHz), and gigahertz (GHz), with one Hz being one wave per second.

The zeroth law of thermodynamics serves as the definition of temperature, but it wasn't created until after the first, second, and third laws of thermodynamics were. The first three laws were already well-known by the time this one came about, but it supersedes all of them. As a result, scientist Ralph H. Fowler who was also a British soldier during World War I — proposed calling it the "zeroth" law. All matter adheres to the zeroth law. It's the reason scientists can measure temperature (which they do in kelvins), and it makes the following three laws of thermodynamics possible:

The first law of thermodynamics: The first law of thermodynamics is another version of the law of conservation of energy, which says that energy can be neither created nor destroyed. It can be transferred to other locations, though, and it can be converted to (and from) other forms of energy. However, the total quantity of energy in the universe always stays the same. The second law of thermodynamics: The second law of thermodynamics describes how energy affects matter, as well as the relationships between thermal energy (heat) and other types of energy. It says that the more energy is transferred or transformed, the more it's wasted. It also says that an isolated system has a tendency to degenerate into a more disordered state. The third law of thermodynamics: The third law of thermodynamics says that achieving a temperature of absolute zero is impossible. Absolute zero is the temperature matter would reach if it contained absolutely no heat energy.

Picking your brain: The nervous system

The human brain is part of the nervous system, which also includes the spinal cord and billions of nerve cells called neurons. The central nervous system contains the cerebrum, which is responsible for thinking, hearing, seeing, and other functions. The cerebellum is also part of the central nervous system; it's the group of nerves responsible for your balance and muscle coordination. The medulla connects your brain to your spinal cord, and it handles all your involuntary actions (including your heartbeat). The spinal cord — the last major component of the central nervous system — is the highway that carries nerve impulses so your brain and organs can communicate. The peripheral nervous system is everything else, and it includes every other neuron in your body.

Here are some units of measurement you need to know for the General Science subtest of the ASVAB:

The meter (m) is a unit of length. The liter (L) is a unit of volume. The gram (g) is a unit of mass (similar to weight).

Categorizing Mother Nature

The most common classification system was created by Swedish botanist Carl Linnaeus, who published ten editions of his works from 1753 to 1758. Scientists often refer to this system as taxonomy. Not only does taxonomy provide official names for every plant and animal, but it also helps scientists understand how living creatures are related to one another. Modern-day taxonomy has its roots in the Linnaean taxonomic system.

Side effects: Feeling hot and cold When substances get hot because their molecules are colliding fast, they expand. When things cool down, they shrink. Sometimes the change in size is so small that you don't notice it — but sometimes it's huge. One example of this change happens in burning houses. The air inside the house is hot, and its molecules are moving really quickly. The air expands so much that it creates tremendous pressure, and eventually, the windows explode outward. Heat expansion is why mercury thermometers worked (back when we still used them, that is). Cold contraction is why a weather balloon looks emptier as it floats higher into the atmosphere.

The reason objects feel so hot or cold to the touch is because of the state their molecules are in. When you stick a metal spoon into a pot of boiling water, it excites the spoon's molecules — and remember, even in solids, the molecules are always moving. If you stick that same spoon in the freezer, you'll slow down its molecules so much that it will feel cold when you touch it. For example, you can test out how cold a metal light pole is by sticking your tongue on it during winter. (Wait! Bad idea. Please don't lick anything metal during winter. I just wanted to make sure you were still paying attention!) Essentially, when you cool down an object, you're "freezing" the movement of its molecules.

Chemical reactions Boiling and freezing are changes in a substance's state (as I discuss earlier in the chapter), but a chemical reaction is a process that rearranges a substance's molecular structure. No matter what its physical state, water is still made up of . But if you compound it with another element, its atoms are redistributed to create a new substance. For example, when iron rusts, a chemical change occurs. The rust isn't the same molecule as the iron is. In a normal chemical reaction, matter is neither created nor destroyed. That means the total mass of reactants (the elements that are changing) is the same as the total mass of products (the elements that have changed).

There are several types of chemical reactions, but the most common are these: Combination: Combination reactions occur when two or more reactants merge to form one product. One example is the way sodium and chlorine combine to create sodium chloride (that's table salt). Decomposition: Decomposition reactions are the opposite of combination reactions because a single compound breaks down into two or more simpler substances. This process happens when water decomposes into hydrogen and oxygen gases, for example. Combustion: Combustion reactions typically involve carbon and oxygen in the process known as burning. This type of reaction occurs in your car, in open fires, and when some people try to cook.

Weight and mass Weight and mass are two different things. Look at it this way: If you were on the moon, you'd weigh a lot less than you do here on Earth. Your body composition hasn't changed, so your mass would remain the same.

Weight is a measure of the force gravity exerts on an object or the force needed to support it. You're being pulled to the Earth at an accelerating rate of 9.8 meters per second squared, or m/s2, but if you were on the moon, you'd be pulled to it at a rate of 1.62 m/s2. You weigh less on the moon than you do on Earth. Mass is a measure of an object's inertial property — the amount of matter it contains. The mass of an object doesn't change, whether it's on the moon, in a compression device, or anywhere else.

Newton's second law of motion Newton's second law of motion says that when dealing with an object for which all existing forces are not balanced, the acceleration of that object (as produced by the net force) is in the same direction as the net force and directly proportional to the magnitude of the net force, and is inversely proportional to the object's mass. That's expressed by the mathematical formula . If you're using this formula, Acceleration = Net Force Divided by Mass. you need to rely on these units of measurement: m/s2, N, and kg.

You can express Newton's second law of motion as , A = F/M where (A) represents acceleration, (F) represents net force, and (M) represents mass. The formula's equivalent form (to figure out force) is (F) = MA. The greater an object's mass, the greater the force you need to overcome its inertia, which is described in Newton's first law of motion (see the preceding section). Starting or stopping a moving 50-car train carrying lead is a lot harder than starting or stopping a toy car in motion. That's because the force necessary to overcome an object's inertia is inversely proportional to its mass. If you use the same force to push the toy car as you use to push the train, the toy car is going to accelerate a lot faster because it has less mass than the train does.

(Sitting down at the periodic table) The periodic table (also known as the table of elements) classifies all elements, because scientists love to classify things. Elements are listed according to their atomic numbers (number of protons) and are arranged into families of similar elements.

You don't have to memorize these charts to do well on the ASVAB, but knowing the atomic numbers for common elements such as hydrogen (1), helium (2), carbon (6), nitrogen (7), and oxygen (8) can't hurt.

(Sitting down at the periodic table) The periodic table (also known as the table of elements) classifies all elements, because scientists love to classify things. Elements are listed according to their atomic numbers (number of protons) and are arranged into families of similar elements.

You don't have to memorize these charts to do well on the ASVAB, but knowing the atomic numbers for common elements such as hydrogen (1), helium (2), carbon (6), nitrogen (7), and oxygen (8) can't hurt. Image 11-2

Newton's third law of motion Newton's third law of motion says that for every action, there is an equal and opposite reaction. That means that when an object exerts a force on another object, the second object exerts an equal force in an opposite direction on the first object. In every interaction between objects, a pair of forces is acting on the objects that are

interacting. The forces on the first object equal the forces on the second object, but the direction of the forces are opposite. Forces always come in pairs, called action-reaction force pairs. Birds can fly because of action-reaction force pairs. A bird's wings push air down, but because every action has an equal and opposite reaction, the air is pushing the bird's wings upward. (They're attached to the bird, so the whole bird stays airborne.) When your car rolls down the road, your wheels push the road backward.The road exerts the same force on your wheels (but in the opposite direction), which makes your car move forward.