Biology & Life Sciences ASVAB

Ecology

All living things need energy to survive. If an organism is able to produce its own energy, it is called a producer. Plants use sunlight to make food, so they are considered producers.

If an organism cannot make its own food, it needs to eat other organisms. These organisms are called consumers. Consumers are divided into four groups:

1. Herbivores eat plants. Examples include deer, grasshoppers, and pandas.

2. Carnivores eat animals. Examples include lions and coyotes.

3. Omnivores eat both plants and animals. Examples include humans, bears, and raccoons.

4. Scavengers are animals that feed on dead animals. These include vultures, earthworms, and maggots (fly larva).

Energy flows in ecosystems as producers use the sun’s energy to make food, and then the producers are eaten by consumers. This flow of energy can be documented in several ways:

Food chains show the linear flow of energy through organisms.

Food webs more accurately depict the flow of energy through an ecosystem, because they show the numerous ways organisms obtain their food. With a food web the arrow indicates the direction of energy flowing through the system. In the food web below, the hawk eats the rabbit, so the energy from the rabbit flows to the hawk.

Energy pyramids show how energy (in the form of food) is lost as it is transferred through organisms in an ecosystem. The amount of available energy is reduced as energy moves to a higher level (trophic level) because organisms use most of their consumed food to live.

Human Body Systems

The human body is organized into 11 major organ systems. These are the systems that you are most likely to be asked about on the  ASVAB Science test:

Muscular System: Includes all the muscles that move the bones and their connective tissue.

Respiratory System: Consists of the nose, pharynx, larynx, trachea, bronchi and lungs. The job of the respiratory system is respiration, or breathing, which is the process by which oxygen is obtained and carbon dioxide (the produce of respiration) is released.

Circulatory System: Responsible for transporting materials to and from the cells. It consists of blood cells and platelets, the heart, and blood vessels (arteries, capillaries and veins).

Digestive System: Works to digest food so that it can be used by the body. It consists of the digestive tract, which is a series of organs that are joined together. The organs of the digestive tract include the mouth, throat, esophagus, stomach, small intestine, large intestine, rectum and anus. The digestive system has several glands associated with it to aid in digestion: liver, gallbladder, pancreas, and salivary glands.

Nervous System: Gathers and interprets information from the body’s internal and external environments, and responds to the information. It allows humans to speak, smell, taste, hear, see, move, think and experience emotions. The nervous system includes the brain, nerves, and spinal cord.

Reproductive System: Allows organisms to make offspring. Humans reproduce sexually, which means it requires a male and female. Females produce sex cells called eggs, and males produce sex cells called sperm. The female reproductive system includes the ovaries, uterus, fallopian tubes and vagina. The male reproductive system includes the testes and penis.

Genetics

Genetics is the study of how hereditary information is passed from one generation of organisms to their offspring.

Gregor Mendel is known as the “Father of Genetics.” He worked in a monastery garden in the 1800s, and studied how pea plants passed traits on to their offspring. In doing so, he bred various pea plants and recorded the traits of their offspring. His results led him to the discovery that each plant contained two sets of instructions for each characteristic. Each parent plant donates one set of these instructions to the offspring.

Since cells carry two copies of each chromosome, they have two versions of each gene. Different versions of genes are called alleles. An allele can be dominant or recessive.

Dominant alleles will show their effect even if the person only has one copy of that particular allele. For example, the allele for brown eyes is a dominant allele. So if a person has an allele for brown eyes and an allele for blue eyes, their eyes will be brown. A person who has two different alleles of a particular gene is described as heterozygous.

Recessive alleles will show their effect only if the person has two copies of that particular allele. For example, the allele for blue eyes is recessive. So if someone has two alleles for blue eyes, their eyes will be blue. A person who has two of the same alleles of a particular gene is described as homozygous.

Summary: If a person has two dominant alleles or two recessive alleles, they are homozygous, and will display the traits of these two identical alleles. If they have one dominant allele and one recessive allele, they are heterozygous, and they will display the traits of the dominant allele.

How to Solve Punnett Squares:

A common genetics problem on the ASVAB requires you to figure out the probability of an offspring having a particular genotype. These problems can be solved by using a Punnett square.

The two alleles for a particular gene are known as the genotype, and can be represented with letters. A capital letter is used for the dominant allele and a lowercase letter is used for the recessive allele. For an example we will review an experiment that involves crossing two pea plants. Pea plants can have rounded seeds or wrinkled seeds. Round seeds are dominant to wrinkled, so round seeds will be represented by a capital R. Wrinkled seeds are recessive and will be represented by a lowercase r. Here are the possible combinations:

RR = This plant will have round seeds.
Rr = This plant will have round seeds.
rr = This plant will have wrinkled seeds.

In our example we will cross a homozygous dominant plant (RR) with a heterozygous plant (Rr). We would setup our Punnett square as shown below with one plants genotype on the left and one plants genotype on the top. Then fill in each of the four squares by copying the symbols across:

Here is the completed Punnett square:

The four boxes represent four offspring. Two of the offspring are homozygous dominant (RR) and two of the offspring are heterozygous (Rr). All four offspring will have rounded seeds. The only way a plant can have wrinkled seeds is by being homozygous recessive (rr).

Now lets try crossing two heterozygous plants:

In the Punnett square shown above you can see that this cross produces 1 plant that is homozygous dominant (RR), 2 that are heterozygous (Rr), and 1 that is homozygous recessive (rr). Only the homozygous recessive plant will have wrinkled seeds. It should be clear that when we cross these 2 heterozygous plants there is a 75% that the offspring will have round seeds and a 25% it will have wrinkled seeds.

Health and Nutrition

Nutrients

Macronutrients

Macronutrients consist of those larger compounds from which we derive the calories, or energy, necessary to sustain life functions. Carbohydrates, proteins, and lipids (or fats) are the macronutrients from which our energy is derived.

Carbohydrates—Carbohydrates, both simple and complex, can be thought of as immediate and readily accessible energy. These molecules are ultimately broken down into glucose and circulated throughout the blood to support metabolic functions.

Lipids—The body converts and stores unused carbohydrates as lipids, or fats. Lipids function as the source material for hormones. They enable better absorption of micronutrients, and they also serve as an energy source.

Protein—Proteins are necessary for cellular growth, repair, and transport. They are made up of amino acids, which can be thought of as micronutrients.

Micronutrients

Micronutrients consist of those vitamins and minerals required by the body to function properly. As indicated by the micro- prefix, these nutrients are only required in small amounts; however, they are not insignificant. If adequate amounts of these micronutrients are not acquired, overall health is potentially compromised, and long-term issues may arise.

Vitamins—There are numerous vitamins found throughout the body, all with a different purpose, to allow for normal cellular function. They can be broken down into two groups: fat-soluble vitamins and water-soluble vitamins. Fat-soluble vitamins (such as vitamins A, D, E, and K) are present in foods with fats and do not dissolve in water. Water-soluble vitamins (such as the B vitamins) are dissolved in water and carried around the body but are not stored.

Minerals—Minerals are found in food that we consume and are essential for cells to function properly. Common minerals are magnesium, potassium, sodium, and calcium.

Other Important Substances

There are various other things that your body needs in order for normal cellular function to occur.

Water—Water is an essential molecule needed for all cellular functions and makes up between 60 and 80 percent of our body mass. In its absence, the metabolic reactions that occur in our body would not be able to exist.

Fiber—Fiber is a plant derivative that cannot be broken down by the body and is essential for bowel health and function. It works by bulking up the stool and allowing for easier passage throughout the body. This can be found in foods such as berries, whole grains, and apples, or as an over-the-counter supplement.

Related terms to know: vitamins, minerals, carbohydrates, lipids, proteins

Nutrition-Related Diseases

Nutrition-related diseases are those which arise from either the deficiency or the excess of a micro or macronutrient. Diabetes, hypertension, scurvy, and iron-deficiency anemia are examples of nutrition-related diseases.

The Human Body

Human anatomy is the study of the human body: how it works, what makes up its parts, and what is necessary to keep it functioning well and properly. Human anatomy is included in the General Science section of the ASVAB, requiring students to have a basic knowledge and understanding of the human body and its functions. To prepare, study the basic components of human anatomy, including the bones, muscles, and blood vessels comprising the body, as well as the basic functions of these different systems. Though the questions are not heavy or in-depth due to the “general” nature of the test, you should have some understanding of how the body works and what is required to keep it functioning.

Skeleton and Muscles

The human skeletal system is a collection of bones, composed of a very hard and inflexible phosphate, and cartilage, composed of spongy, flexible collagen. The skeletal system functions as structural support and protection for muscles and organs. It also facilitates locomotion. Blood is created inside of bone marrow.

The muscular system works in conjunction with the skeletal system to facilitate motion. The muscular system is made up of three types of muscle: cardiac muscle, skeletal muscle, and smooth muscle.

The heart is made of cardiac muscle that is involved in regulating contraction and relaxation of the heart.

Skeletal muscles are those connected to bone that enable motion.

Smooth muscle lines organs and aids in digestion.

Related terms to know: bones, cartilage, cardiac, skeletal, smooth

Respiration

Respiration is a process performed by living organisms that allows for the exchanging of gases between one’s internal and external environment. Cells use these gases as a way to obtain energy for cell processes to take place.

Oxygen—Cellular respiration can occur with or without oxygen. In aerobic processes (those that involve oxygen), oxygen is converted into energy in the form of ATP. In human respiration this is the gas that we inhale.

Carbon dioxide—Carbon dioxide is the gas that oxygen is exchanged for in respiration and therefore the gas that we exhale.

Water Vapor—This is the gas phase of water. It occurs as liquid water is evaporated or solid water (ice) undergoes sublimation.

Nose—The nose allows for both inhalation and exhalation of air via respiration.

Nasal cavity—This is the air-filled space behind the nose.

Pharynx—The pharynx (also known as the throat) is the structure behind the nose and the mouth that connects them to the esophagus. Its main function is to receive and allow for the transmission of air to the lungs and food to the stomach.

Epiglottis—This is the flap behind the tongue that ensures that air goes to the lungs and food goes to the stomach. At rest, the epiglottis sits upright and flips over one way or the other, depending whether food or air enters the mouth/nose.

Trachea—The trachea (also known as the windpipe) is a passageway for air to get moist and warm as it makes its way to the lungs.

Bronchi—The trachea branches into the left and right bronchi. The bronchi are responsible for transporting air that has come through the windpipe to the lungs.

Lungs—After air leaves the left and right bronchi, it dumps into the left and right lungs, respectively. The lungs are spongy organs that can be broken down into smaller divisions to allow for gas exchange to occur.

Bronchioles—Also known as “little bronchi”, these are smaller branches that the left and right bronchi divide into.

Alveolus—These are tiny air sacs that branch off from the bronchioles where gas exchange occurs in the lungs.

Capillaries—These are tiny blood vessels that serve as a connection point between arterioles and venules, allowing nutrients to be transferred between blood and tissues

Diaphragm—The diaphragm is a skeletal muscle that sits below the lungs. As you inhale, the diaphragm contracts and flattens to allow your lungs to fill with more air. As you exhale the diaphragm relaxes so air can be pushed out of the lungs.

Blood and Circulation

The circulatory system is responsible for the transport of blood and nutrients throughout the body. It is made up of arteries, veins, capillaries, the lungs, the heart, the brain, and the kidneys.

The heart functions to pump oxygenated blood to the body and deoxygenated blood to the lungs to become oxygenated. Blood flows through the arteries and veins along with other nutrients, while delivering oxygen to cells throughout the body and carbon dioxide to the lungs to be eliminated.

Blood consists of red blood cells, which facilitate oxygenation, white blood cells, which aid in immunologic defense, plasma, which is the liquid medium inside of the circulatory system, and platelets, which also aid in defense.

Other Terms to Know

Atrium/atria—These are the two receiving chambers of the heart. They appear on both the left and right sides of the heart above the ventricles.

Ventricles—These are the two pumping chambers of the heart. They appear on both the left and right sides of the heart below the atria.

Vena cava(e)—There are two vena cavae in the heart: superior and inferior. The superior vena cava drains the upper part of the body while the inferior vena cava drains the lower half of the body. Both of these dump deoxygenated blood into the right atrium.

Pulmonary artery—This is responsible for carrying deoxygenated blood from the heart to the lungs.

Pulmonary vein—This is responsible for carrying oxygenated blood from the lungs to the heart.

Aorta—This is the largest artery in the body. Oxygenated blood will leave the heart through the aorta to be sent throughout the whole body.

Artery—This is a blood vessel that carries blood away from the heart. You can think “A” and “Away”. Arteries typically carry oxygenated blood with the exception of the pulmonary artery, which carries deoxygenated blood.

Arterioles—Also known as “little arteries,” these are small branches off the arteries that connect arteries to capillaries.

Vein—A vein is a blood vessel that carries blood toward the heart. Veins typically carry deoxygenated blood with the exception of the pulmonary vein, which carries oxygenated blood.

Valves—There are four valves of the heart: the bicuspid (mitral) valve, tricuspid valve, aortic valve, and pulmonary valve. The tricuspid and bicuspid valves are also known as the atrioventricular (AV) valves as these are the two valves that separate the atria from the ventricles. The bicuspid (or mitral valve) separates the left atrium from the left ventricle, and the tricuspid valve separates the right atrium from the left atrium. The aortic valve connects the left ventricle to the aorta (hence the name), and the pulmonary valve connects the right ventricle to the lungs.

Diffusion—This is the movement of molecules from an area of high concentration to low concentration.

Venules—Also known as “little veins”, these are small branches off the veins that connect veins to capillaries.

Heart Disease (Cardiovascular Disease)

Heart diseases, also known as cardiovascular diseases, stem from difficulties in pumping blood throughout the body by way of arterial blockage, high blood pressure, and other issues.

Blood Types

There are four main blood types: A, B, AB, and O. These blood types are dependent on the antigens present on one’s red blood cells (also known as erythrocytes). Each blood type is also classified as either positive or negative depending on if the Rhesus (Rh) factor is present or not.

Antigens—These are what the cells recognize as “self”. For example, if someone has a blood type A, they will have A antigens on the surface of their red blood cells. If they have AB blood, then they will have both A and B antigens. O blood is the absence of any antigens.

Rh factor—Rhesus (Rh) factor is an inherited protein that is found on the surface of red blood cells. Presence of this protein makes you Rh positive, and absence of this protein makes you Rh negative.

Universal donor—This is someone who can donate blood to someone with any blood type. The universal blood donor is blood type O since there are no antigens on the surface of its cells.

Universal recipient—This is someone who can receive blood from someone with any blood type. The universal blood recipient is blood type AB since there are both A and B antigens on the surface of its cells.

Digestion and Excretion

The digestive system functions to break food down into usable micro and macronutrients. Upon ingestion of food, the digestive process begins.

The saliva in our mouths contains enzymes that begin breaking down food. Mastication, or chewing, helps reduce the food to a bolus that is easy to swallow.

Smooth muscle in the esophagus undergoes peristalsis to pass the bolus to the stomach where the bolus is treated with strong acids to create chyme, which is then passed onto the small intestine.

The small intestine primarily serves to absorb the nutrients from the chyme before passing it on to the large intestine (colon). In the large intestine, further absorption of nutrients and water takes place, before passing the remaining matter, termed feces, to the rectum where it is excreted through the anus.

The excretory system serves to expel waste, primarily urine, from the body. This system helps maintain homeostasis through the regulation of internal fluids. Its major components are: kidneys, lungs, skin, ureter, urethra, and the urinary bladder.

The kidneys function to remove waste from the bloodstream through a filtration system resulting in the production of urine.

The lungs, in addition to providing oxygenated blood, remove carbon dioxide from the blood.

The skin is the organ through which perspiration (sweat) is released. It plays a minor role in excretion; its primary role is temperature regulation.

The ureter, urethra, and urinary bladder all work in conjunction to remove and expel urine from the body.

Salivary amylase—This is an enzyme found in the mouth that is responsible for the initial breakdown of starches from complex carbohydrates to monosaccharides (simple sugars).

Gastric acids—Gastric acid, also known as stomach acid, is the acidic fluid within the stomach. The pH of the stomach lies between 1 and 3 and is essential for activating digestive enzymes as well as breaking down proteins.

Pepsin—Pepsin is an enzyme found in the stomach that breaks down proteins into polypeptides.

Pancreas—The pancreas is an organ found below the liver. One of its main functions is to produce enzymes that break down food into a usable form for our body. One pancreatic enzyme is lipase, which is responsible for breaking down fats. Another pancreatic enzyme, pancreatic amylase, similar to salivary amylase, is responsible for breaking down starches. Finally, trypsin in the pancreas allows for the digestion of protein.

Liver—The liver is a large organ that is situated on the right side of the abdomen. It serves as producer of bile, metabolizer of nutrients, and an enzyme activator. It also helps with the excretion of drugs and hormones.

Bile—Bile is a green-brown fluid that is produced in the liver and stored in the gallbladder. It functions to carry wastes away and break down fats.

Related term to know: organs

The Nervous System

The nervous system enables communication between cells throughout the body. Its major components are the brain, the spinal cord, and neurons, or nerve cells.

The brain acts as the central information processing unit of the body. It is composed of many billion neurons and it is where information received by the senses is processed. The brain contains two hemispheres (left and right) and three major parts: the cerebrum, the cerebellum, and the brain stem.

The cerebrum, the largest portion of the brain, is responsible for numerous things such as (but not limited to) speech, judgment, problem-solving, and emotions. The cerebellum aids in balance and coordination. The brainstem connects with the spinal cord and regulates involuntary movements such as breathing and digestion.

The neurons that make up the brain contain a nucleus and long branches that extend to other neurons. Chemical signals pass from one neuron to the next to transmit information.

The spinal cord connects the brain to the rest of the body. It is a bundle of nerves that runs vertically through the spine that branches throughout the body. Signals received by the senses travel through the spinal cord to be processed in the brain.

Together, the brain and the spinal cord form the central nervous system. The peripheral nervous system is the collection of nerves residing outside of the central nervous system, coordinating voluntary and involuntary movement.

Related terms to know: neurons, brain, spinal cord, somatic nervous system, autonomic nervous system, medulla, simple reflexes

Reproduction

Reproduction exists in two forms: asexual and sexual. Asexual reproduction requires no partner, and the offspring produced inherits the same genes as the parent. This differs from sexual reproduction, in which there are usually two partners who both contribute equally to the genetic makeup of the offspring.

Asexual Reproduction

Asexual reproduction is the method by which somatic (or body) cells divide. Through mitosis, a cell divides, and both daughter cells possess the exact DNA of the parent cell.

(Human) Sexual Reproduction

During sexual intercourse, sperm is ejaculated into the vagina of a female. The sperm makes its way to the fallopian tubes where it tries to find an egg to fertilize. If fertilization occurs, a zygote will form and the cells will continue dividing as the fertilized egg travels to the uterus with the intention of implanting in the uterine wall to form an embryo.

Meiosis— This is the process by which sex cells divide. This process results in cells that contain genetic material that is partially from one parent cell and partially from a different parent cell.

Ovulation—Ovulation occurs in females when an egg is released from the ovary. This occurs approximately two weeks after a female’s menstruation.

Ovum—The ovum is the mature female reproductive cell.

Oviduct (Fallopian Tube)—Fallopian tubes are responsible for connecting the ovaries to the uterus. This is also where fertilization of the egg occurs.

Uterus—The uterus is an organ found internally in a female that functions to nourish a fetus during pregnancy.

Endometrial lining—This is the lining of a female’s uterus that gets shed once a month during her menstrual cycle.

Penis—This is the external sex organ of a male that allows for the passage of both urine and sperm.

Testes—Testes are responsible for making testosterone and sperm in a male.

Vagina—The vagina is the canal that runs from the uterus to the outside of a woman’s body. It has several functions, including acting as a passageway for a fetus during childbirth and receiving the penis during sexual intercourse.

Zygote—This is another name for a fertilized ovum.

Prolactin—Prolactin is a hormone produced by the pituitary gland inside the brain that causes milk production in postpartum women. However, this hormone is found in both males and females, but in different quantities.

Lactation—Lactation is the release of milk from the mammary glands.

Menstruation—This is also known as a period—when a woman sheds her endometrial lining causing bleeding to occur during the menstrual cycle.

Menstrual cycle—This is a monthly cycle that pre-menopausal/post-pubescent women go through, during which ovulation occurs.

Related terms to know: mitosis, cellular division

Human Pathogens

A pathogen, in general, is anything that can cause a disease. Human pathogens are specifically those that can cause diseases in humans and can either be bacterial, fungal, or viral.

Bacteria—Bacteria are unicellular, prokaryotic microorganisms that can serve to benefit humans or can be pathogenic.

Viruses—Viruses are non-living, pathogenic microorganisms.

Vaccination/Immunization—These are a weakened form of a virus that allows for one to become immune to an infection caused by either a virus or a bacteria.

Genetics

Genetics is the study of genes, the portions of DNA that result in genotypic and phenotypic traits that are passed from one generation to the next. An organism’s genotype is its genetic makeup, which includes both dominant and recessive alleles (or variation of a gene). An organism’s phenotype is the physical expression of its genotype.

Dominant traits are those that are expressed when a person has two types of alleles. Recessive traits are those that go unexpressed unless a person possesses both recessive alleles.

Deoxyribonucleic acid (DNA) is the nucleic acid containing the nucleotides adenine, guanine, thymine, and cytosine that provides the blueprint for cell replication. Variations in DNA account for the different genetic and physical traits of organisms.

Meiosis and mitosis are the processes by which cells replicate. Sex cells undergo meiosis, which combines the genes of two individuals to produce a new genotype. Somatic (body) cells undergo mitosis and create two daughter cells with the same genotype as the parent cell.

Humans have 23 pairs of chromosomes, or tightly wrapped strands of DNA, that provide the instructions for metabolic processes, building cellular and tissue components, as well as other body functions. One pair of chromosomes is linked to sex: females exhibit a homozygous XX chromosome and males exhibit a heterozygous XY chromosome.

A Punnett square can be used to determine the potential genotypes of offspring between two parents. It is a large square with four (or more) squares inside, with the rows and columns corresponding to the alleles of the parents. Two heterozygous parents are shown with a capital letter and a lowercase letter along the left and right columns and down the top and bottom rows. The offspring genotypes are found by filling in the four (or more) boxes with the letters found at the top and to the left of the Punnett square. Heterozygous parents produce two homozygous offspring, one AA, one aa, and two heterozygous offspring, Aa.

An example of a Punnett square is shown above. Notice that you will have one parent’s set of alleles on the top and parent two’s alleles on the left side. This Punnett square shows the female at the top and the male on the side, but that is not always the case. If you are looking at a monohybrid cross, such as the one shown, where only one trait is present, your Punnett square should have four boxes.

To figure out what goes in each of the boxes, you must find what alleles from each parent meet up in that box. For example, if you look at the box on the top left, you see that there is RR inside the box. That means that the R from the female and the R from the male both met up inside that box. This process should be repeated for the other three boxes.

Other Related Terms

In order to have a better understanding of genetics, you should be able to understand and apply the following terms:

Gregor Mendel—Gregor Mendel is considered the “Father of Genetics” as his work with pea plants formed the basic ideas of genetics that we understand today.

Gametes—Gametes are mature, haploid sex cells; in females this would be the egg, while in males this would be sperm.

Diploid—A diploid is two complete sets of chromosomes (one from each parent); in humans, this refers to having 23 pairs of chromosomes.

Haploid—A haploid is a single set of chromosomes found in gametes (ex: egg or sperm).

Genetic code—This is the combination of nucleotides found along a DNA sequence that carries genetic information.

Nucleotides—Nucleotides are compounds that are the structural foundation of DNA. They include adenine, thymine, uracil, cytosine, and guanine.

Double helix—This is the shape that DNA takes as two single strands are connected to one another.

Cells

Cells are the most basic structural unit of life. Prokaryotic cells are those that do not contain a membrane-bound nucleus or organelles; they are single-celled organisms. Bacteria are an example of a prokaryote. Eukaryotic cells are those that contain a membrane-bound nucleus in addition to other organelles; they are single-celled or multi-celled organisms. Humans are eukaryotic.

The genetic material of prokaryotes floats openly throughout its cytoplasm, whereas the genetic material of eukaryotes is found inside of the nucleus. Prokaryotes undergo binary fission to replicate, and eukaryotes undergo meiosis and mitosis to replicate.

Animal cells are different from plant cells in the organelles they contain. Organelles are analogous to organs in humans and perform the tasks necessary to preserve the metabolic function of the cell. Animal cells also contain lysosomes, which are not usually present in plant cells.

Plant cells contain a cell wall, plastids, and chloroplasts, which enable plants to produce energy through photosynthesis. Animal cells and plant cells both contain a nucleus, a cell membrane, a Golgi apparatus, ribosomes, mitochondria, smooth and rough endoplasmic reticulum, cytoplasm, and vacuoles.

Many of the functions performed by the body are also performed by the cell. Cells produce energy in the mitochondria, generate waste through cellular processes, and eliminate this waste with lysosomes. They regulate internal fluids with vacuoles and remain isolated from their environment by way of the cell membrane or wall.

Related terms to know: prokaryote, eukaryote, mitochondria, nucleus, chloroplast

Cell Respiration

During cellular respiration, glucose molecules are ultimately transformed into ATP that our body can utilize for energy. The first step in cellular respiration is glycolysis. During glycolysis, glucose is broken down into two pyruvate molecules, two , and two . The two pyruvates generated undergo pyruvate oxidation. This process turns pyruvate into acetyl and creates and carbon dioxide . The acetyl is used to initiate the Citric Acid Cycle (), also known as the Krebs Cycle. During this process two , one , one , and three are produced per turn of the Krebs Cycle.

Cell Division

Somatic cells (non-sex cells) are divided via a process called mitosis. In mitosis, two identical daughter cells are formed. It is made up of four steps: prophase, metaphase, anaphase, and telophase.

Sex cells, also known as gametes, undergo meiosis to divide. In meiosis, a single cell is going to divide into four different cells, all with half the original amount of chromosomes that started.

Ecology

Ecology is the study of organisms and their interactions with their environment. This includes small interactions, such as microscopic creatures in their environments, as well as large interactions, such as large mammals and their environmental behaviors. To study for this aspect of the General Science section, acquaint yourself with basic ecological functions, ecological systems, and the ways in which ecology is affected by changes in weather patterns, migratory patterns, and the alteration of organisms.

Biosphere—the parts of Earth where life exists; remember that “bio-” refers to life.

Biome—a group of land ecosystems, all which share similar climates and organisms.

Ecosystem—a group of living and nonliving parts that live in the same environment that interact together.

Community—the interaction of all populations in a given area.

Population—a group of organisms that live together and come from the same species.

Ecology Classification Terms

Producers—an organism capable of producing its own food (ex: plants)

Decomposers—organisms that break down dead plants and animals.

Scavengers—organisms that consume dead material.

Consumers—organisms that must eat another organism in order to obtain energy.

• Primary (herbivores)—Herbivores consume only plants.

• Secondary (carnivores)—Carnivores consume only meat.

• Tertiary (top carnivores/omnivores)—capable of eating both plants and meat.

Consumer Hierarchy and a Food Web

To figure out what an animal preys on and who its predators are can be demonstrated using a food web, and it’s representative of an entire ecosystem. Arrows in a food web show the flow of energy from one organism to another. An example is shown below.

Living Thing Classification

Living things are classified according to a taxonomic structure: domain, kingdom, phylum, class, order, family, genus, and species.

Domains are the least specific and include the largest number of organisms. Kingdoms are more specific than domains and include a smaller number of organisms. Movement from a less specific to more specific taxonomic level shows a greater similarity between organisms within the level.

A mnemonic is useful for remembering the taxonomic structure: “King Phillip Came Over For Great Spaghetti”, for example.

Related terms to know: taxonomy

Domains

Eukaryota—This is one of the three domains of life. This domain includes kingdoms such as plants, animals, and fungi. All organisms in this domain are considered eukaryotic, meaning that they have a nucleus in their cells.

Bacteria and Archaea—Organisms in these domains are considered prokaryotes, meaning their cells lack a nucleus or any other membrane-bound organelles such as a mitochondria and ribosomes.

Related terms to know: monera, protista, fungi, plantae, animalia