Search for Constancy

A.p bio 🧪 UNIT 1 CHEMISTRY OF LIFE — TEST CRAM Q&A 🟣 TOPIC 1: BIOLOGY REVIEW & STATISTICS Experimental Design Q: What is the independent variable? A: The variable the scientist changes/manipulates. Q: What is the dependent variable? A: The variable that is measured/observed. Q: Easy way to remember independent vs. dependent? A: Independent = I change it. Dependent = data I collect. Q: In an experiment, fertilizer concentration is changed and plant height is measured. What is the independent variable? A: Fertilizer concentration. Q: What is the dependent variable? A: Plant height. Q: What are constants? A: Things kept the same for every experimental group. Q: What is a control group? A: A group used as a comparison/baseline. Q: What is a positive control? A: A group that should produce a known positive result. Q: What is a negative control? A: A group that should produce no response/result. ⸻ Data & Statistics Q: What is qualitative data? A: Descriptive data that isn’t measured numerically. Example: color, texture, smell. Q: What is quantitative data? A: Numerical/measurable data. Example: 15 cm, 20°C, 5 grams. Q: What is the mean? A: The average: add all values and divide by the number of values. Q: What is the median? A: The middle value when data is arranged from least to greatest. Q: What is the mode? A: The value that occurs most often. Q: What is the range? A: Highest − lowest. Q: What does standard deviation tell you? A: How spread out the data is around the mean. Q: Small standard deviation means what? A: Data points are close together/consistent. Q: Large standard deviation means what? A: Data points are more spread out/variable. Q: If Group A and Group B have similar means, but Group A has a much smaller standard deviation, what does that mean? A: Group A’s data is more consistent and clustered around the mean. Q: What is SEM? A: Standard error of the mean; it estimates how accurately the sample mean represents the population mean. Q: What does a small SEM mean? A: The mean is more precise/reliable. Q: What do error bars show? A: The amount of variation or uncertainty around a mean, depending on what the graph specifies. Q: What should you look for when reading graphs? A: Specific data points, trends, patterns, increases/decreases, and relationships between variables. ⸻ 💧 TOPIC 2: STRUCTURE OF WATER & HYDROGEN BONDING Q: Why is water polar? A: Oxygen is more electronegative than hydrogen, so oxygen becomes partially negative and hydrogen becomes partially positive. Q: What does δ− mean? A: Partial negative charge. Q: What does δ+ mean? A: Partial positive charge. Q: What type of bond holds the H and O together inside one water molecule? A: Covalent bond. Q: What type of attraction occurs between different water molecules? A: Hydrogen bonds. Q: What causes water’s cohesion? A: Hydrogen bonding between water molecules. Q: What is cohesion? A: Water molecules sticking to other water molecules. Q: What is adhesion? A: Water sticking to other surfaces/materials. Q: What causes surface tension? A: Cohesion/hydrogen bonding between water molecules at the surface. Q: What is capillary action? A: Water moving upward through a narrow space because of cohesion + adhesion. Q: Why can water move upward through plants? A: Hydrogen bonding creates cohesion between water molecules, while adhesion helps water interact with the plant’s xylem walls, allowing capillary action. Q: Which interaction is primarily responsible for water cohesion? A: Hydrogen bonds. Q: What is a solute? A: The substance being dissolved. Q: What is a solvent? A: The substance that does the dissolving. Q: What is a solution? A: A solute + solvent mixture. ⭐ MUST KNOW: Polarity → hydrogen bonding → cohesion/adhesion → capillary action → water movement in plants ⸻ 🧬 TOPIC 2: ELEMENTS OF LIFE Q: Why is carbon so important to life? A: Carbon has 4 valence electrons, allowing it to form four stable covalent bonds and create many different structures. Q: Why can carbon create such a huge diversity of molecules? A: It can bond with itself and many other elements, creating chains, rings, branches, and complex structures. Q: What four major macromolecules are built from carbon? A: Carbohydrates, proteins, lipids, and nucleic acids. Q: What element is especially important in amino acids and nitrogenous bases? A: Nitrogen. Q: What element is found in nucleic acids and certain lipids? A: Phosphorus. Functional Groups Q: What is a functional group? A: A group of atoms that gives an organic molecule specific chemical properties and behaviors. Q: What are the major functional groups you need to know? A: Hydroxyl, carbonyl, carboxyl, amino, and phosphate. Q: What is a hydroxyl group? A: –OH Q: What is a carboxyl group? A: –COOH Q: What is an amino group? A: –NH₂ Q: What is a phosphate group? A: –PO₄ group. Q: What is a carbonyl group? A: A carbon double-bonded to oxygen: C=O. Q: What is a hydrocarbon? A: A molecule made only of carbon and hydrogen. ⸻ 🔗 TOPIC 3: INTRODUCTION TO BIOLOGICAL MACROMOLECULES Q: What is a monomer? A: A small building block that can join with others. Q: What is a polymer? A: A large molecule made from repeating monomers. Q: What are the four major biological macromolecules? A: Carbohydrates, proteins, lipids, nucleic acids. Q: What is dehydration synthesis? A: A process that joins monomers by forming a covalent bond and removing H₂O. Q: What is hydrolysis? A: A process that breaks covalent bonds by adding H₂O. 🧠 REMEMBER: Dehydration = take water OUT → build Hydrolysis = add water → break Q: Which process joins monomers to form a polymer? A: Dehydration synthesis. Q: Which process breaks polymers apart? A: Hydrolysis. Q: What happens to water during dehydration synthesis? A: Water is removed/released. Q: What happens to water during hydrolysis? A: Water is added. ⸻ 🍞 TOPIC 4: PROPERTIES OF BIOLOGICAL MACROMOLECULES Carbohydrates Q: What is a monosaccharide? A: A single sugar monomer. Q: What is a polysaccharide? A: A carbohydrate polymer made of many sugar units. Q: What is starch used for? A: Energy storage in plants. Q: What is glycogen used for? A: Energy storage in animals. Q: What is cellulose used for? A: Structural support in plant cell walls. ⸻ Proteins Q: What are proteins made of? A: Amino acids. Q: What is the monomer of a protein? A: Amino acid. Q: What part of an amino acid varies between amino acids? A: The R group. Q: Why are R groups important? A: Their different properties affect how a protein folds and functions. ⸻ Lipids Q: Are lipids generally polar or nonpolar? A: Mostly nonpolar/hydrophobic. Q: What does hydrophobic mean? A: Water-fearing; doesn’t mix well with water. Q: What does hydrophilic mean? A: Water-loving; interacts with water. Q: What is the difference between saturated and unsaturated fatty acids? A: Saturated = no C=C double bonds. Unsaturated = one or more C=C double bonds. Q: Which fatty acid has more bends/kinks? A: Unsaturated fatty acid. Q: Why do unsaturated fatty acids have kinks? A: Their double bonds bend the carbon chain. ⸻ Phospholipids Q: What two types of regions does a phospholipid have? A: A polar hydrophilic head and nonpolar hydrophobic tails. Q: Why are phospholipids important in cells? A: They form the cell membrane bilayer. Q: Why do phospholipids form a bilayer? A: The hydrophilic heads face the watery environments while the hydrophobic tails face inward away from water. ⸻ Nucleic Acids Q: What do nucleic acids do? A: They store and transmit biological information. Q: What is the monomer of nucleic acids? A: Nucleotide. Q: What are nucleotides made of? A: A 5-carbon sugar + phosphate group + nitrogenous base. ⸻ 🧩 TOPIC 5: STRUCTURE & FUNCTION OF BIOLOGICAL MACROMOLECULES Protein Structure Q: What determines a protein’s primary structure? A: The sequence of amino acids. Q: What is secondary protein structure? A: Local folding into structures such as alpha helices and beta sheets, stabilized by hydrogen bonds. Q: What is tertiary structure? A: The overall 3D shape of one polypeptide. Q: What is quaternary structure? A: Multiple polypeptide chains/subunits working together. ⭐ KNOW THIS ORDER: Primary → Secondary → Tertiary → Quaternary Q: Why can changing one amino acid affect protein function? A: It can change interactions between amino acids, which can change the protein’s shape, potentially changing its function. Q: What is denaturation? A: When a protein loses its normal shape, causing it to lose or reduce its function. Q: What can cause protein denaturation? A: Things such as high temperature or extreme pH. ⸻ DNA Structure Q: What does antiparallel mean? A: The two DNA strands run in opposite directions: one 5’ → 3’ and the other 3’ → 5’. Q: Why is DNA directionality important? A: DNA strands have specific 5’ and 3’ ends, which determines how they are read and copied. ⸻ Carbohydrate Structure Q: Why can two carbohydrates made from similar sugar monomers have different functions? A: Their monomers can have different arrangements, bonding, branching, and structures, which changes their properties and functions. Q: Example of this? A: Starch and cellulose are both made from glucose, but their different bonding/arrangements give them different functions. ⸻ 🧬 TOPIC 6: NUCLEIC ACIDS Q: What are the three parts of a nucleotide? A: 5-carbon sugar + phosphate group + nitrogenous base. Q: What sugar is found in DNA? A: Deoxyribose. Q: What sugar is found in RNA? A: Ribose. Q: What nitrogenous base is found in DNA but not RNA? A: Thymine (T). Q: What nitrogenous base is found in RNA instead of thymine? A: Uracil (U). Q: Is DNA usually single- or double-stranded? A: Double-stranded. Q: Is RNA usually single- or double-stranded? A: Single-stranded. Q: What does DNA store? A: Genetic/biological information. Q: What connects nucleotides together? A: Covalent bonds form the sugar-phosphate backbone. ⸻ 🧬 Base Pairing Q: What does A pair with in DNA? A: T Q: What does T pair with? A: A Q: What does C pair with? A: G Q: What does G pair with? A: C RNA: A ↔ U C ↔ G Q: If one DNA strand is 5’-ACGTAC-3’, what is the complementary strand? A: 3’-TGCATG-5’ Q: Why is it written 3’ → 5’? A: Because DNA strands are antiparallel. ⸻ 🔥 UNIT 1 BIG CONNECTIONS — YOUR TEACHER WILL LOVE THESE Q: Explain the water connection. A: Water’s polarity causes hydrogen bonding, which produces properties like cohesion and adhesion that are important for biological functions such as water movement through plants. Q: Explain the carbon connection. A: Carbon’s four valence electrons allow it to form many covalent bonds, creating the huge diversity of biological molecules. Q: Explain the macromolecule connection. A: Monomers join → polymers/macromolecules form → their structure determines their properties and function. Q: Explain the protein connection. A: Amino acid sequence → protein shape → protein function. Q: Explain the DNA connection. A: Nucleotide sequence → biological/genetic information. Q: Explain the experiment connection. A: Experimental design → data → analysis → evidence → biological conclusion. ⸻ 🚨 15 QUESTIONS YOU SHOULD BE ABLE TO ANSWER WITHOUT LOOKING What is the independent variable? → What you change. What is the dependent variable? → What you measure. Small standard deviation means…? → Data is consistent/close together. Why is water polar? → Oxygen is more electronegative than hydrogen. What causes cohesion? → Hydrogen bonding. What causes capillary action? → Cohesion + adhesion. Why is carbon so versatile? → Four valence electrons. What joins monomers? → Dehydration synthesis. What breaks polymers? → Hydrolysis. Protein monomer? → Amino acid. Nucleic acid monomer? → Nucleotide. Unsaturated fatty acids have what? → Double bonds and kinks. What determines protein shape? → Amino acid sequence/interactions. DNA sugar/base? → Deoxyribose + thymine. DNA strands are…? → Double-stranded and antiparallel. 🧠 LAST-MINUTE MEMORY CHAIN Memorize this exact chain: Water: POLAR → H-BONDS → COHESION/ADHESION → CAPILLARY ACTION Macromolecules: MONOMER → DEHYDRATION → POLYMER Breaking: POLYMER → HYDROLYSIS → MONOMERS Protein: AMINO ACID SEQUENCE → SHAPE → FUNCTION DNA: NUCLEOTIDE SEQUENCE → INFORMATION Experiment: INDEPENDENT → DEPENDENT → DATA → EVIDENCE → CONCLUSION

Exam Review Chapters 1, 2, & 3. Chapter 1 The Science of Psychology Behavior: Everything, we do that can be directly observed. Behavioral approach: an approach to psychology emphasizing the scientific study of observable behavioral responses and their environmental determinants. Biological approach: an approach to psychology focusing on the body, especially the brain and nervous system. Case study or case history: an in-depth look at a single individual. Cognitive approach: an approach to psychology emphasizing the mental processes involved in knowing: how we direct our attention, perceive, remember, think, and solve problems. Control group: The participants in an experiment who are as much like the experimental group as possible and who are treated in every way like the experimental group except for a manipulated factor, the independent variable. Correlational research: research that examines the relationships between variables, whose purpose is to examine whether and how two variables change together. Critical thinking: The process of thinking deeply and actively, asking questions, and evaluating the evidence. Dependent variable: The outcome; the factor that can change in an experiment in response to changes in the independent variable. Double-blind experiment: An experimental design in which neither the experimenter nor the participants are aware of which participants are in the experimental group and which are in the control group until the results are calculated. Evolutionary approach: An approach to psychology centered on evolutionary ideas such as adaptation, reproduction, and natural selection as the basis for explaining specific human behaviors. Experiment: A carefully regulated procedure in which the researcher manipulates one or more variables that are believed to influence some other variable. Experimental group: The participants in an experiment who receive the drug or other treatment under study—that is, those who are exposed to the change that the independent variable represents. Functionalism: James’s approach to mental processes, emphasizing the functions and purposes of the mind and behavior in the individual’s adaptation to the environment. Humanistic approach: An approach to psychology emphasizing a person’s positive qualities, the capacity for positive growth, and the freedom to choose any destiny. Hypothesis: A testable prediction that derives logically from a theory. Independent variable: A manipulated experimental factor; the variable that the experimenter changes to see what its effects are. Longitudinal design: A special kind of systematic observation, used by correlational researchers, that involves obtaining measures of the variables of interest in multiple waves over time. Mental processes: The thoughts, feelings, and motives that people experience privately but that cannot be observed directly. Natural selection: Darwin’s principle of an evolutionary process in which organisms that are best adapted to their environment will survive and produce offspring. Naturalistic observation: The observation of behavior in a real-world setting. Placebo: In a drug study, a harmless substance that has no physiological effect, given to participants in a control group so that they are treated identically to the experimental group except for the active agent. Placebo effect: The situation where participants’ expectations, rather than the experimental treatment, produce an experimental outcome. Population: The entire group about which the researcher wants to draw conclusions. Psychoanalysis: techniques involves an analyst unlocking a person's unconscious conflicts by talking with the individual about his or her childhood memories, dreams, thoughts, and feelings. Psychodynamic approach: an approach to psychology emphasizing unconscious thought, the conflict between biological drives (such as the drive for sex) and society’s demands, and early childhood family experiences. Psychology: The scientific study of behavior and mental processes. Sample: The subset of the population chosen by the investigator for study. Sociocultural approach: an approach to psychology that examines the ways in which social and cultural environments influence behavior. Structuralism: Wundt’s approach to discovering the basic elements, or structures, of mental processes. Theory: A broad idea or set of closely related ideas that attempts to explain observations and to make predictions about future observations. Validity: The soundness of the conclusions that a researcher draws from an experiment. In the realm of testing, the extent to which a test measures what it is intended to measure. Variable: Anything that can change. Wilhelm Wundt is most often regarded the "founding father" of modern psychology. He was also the founder of structuralism. William James was the founder of functionalism. J. B. Watson and B. F. Skinner believed that psychology should focus on an organism's visible interactions with the environment—that is, behaviors. Ethical Guidelines developed by the American Psychological Association include: • informed consent. • confidentiality. • deception. • debriefing. Chapter 2 The Brain and Behavior Action potential: The brief wave of positive electrical charge that sweeps down the axon. Adrenal glands: glands at the top of each kidney that are responsible for regulating moods, energy level, and the ability to cope with stress. Amygdala: An almond-shaped structure within the base of the temporal lobe that is involved in the discrimination of objects that are necessary for the organism’s survival, such as appropriate food, mates, and social rivals. Association cortex: Sometimes called association areas, the region of the cerebral cortex that is the site of the highest intellectual functions, such as thinking and problem solving. Autonomic nervous system: The body system that takes messages to and from the body’s internal organs, monitoring such processes as breathing, heart rate, and digestion. Axon The part of the neuron that carries information away from the cell body toward other cells. Basal ganglia Large neuron clusters located above the thalamus and under the cerebral cortex that work with the cerebellum and the cerebral cortex to control and coordinate voluntary movements. Brain stem The stem like brain area that includes much of the hindbrain (excluding the cerebellum) and the midbrain; connects with the spinal cord at its lower end and then extends upward to encase the reticular formation in the midbrain. Cell body The part of the neuron that contains the nucleus, which directs the manufacture of substances that the neuron needs for growth and maintenance. Central nervous system (CNS): The brain and spinal cord. Cerebral cortex: Part of the forebrain, the outer layer of the brain, responsible for the most complex mental functions, such as thinking and planning. Chromosomes: In the human cell, threadlike structures that come in 23 pairs, one member of each pair originating from each parent, and that contain DNA. Corpus callosum: The large bundle of axons that connects the brain’s two hemispheres, responsible for relaying information between the two sides. Dendrites: Treelike fibers projecting from a neuron, which receive information and orient it toward the neuron’s cell body. Deoxyribonucleic acid (DNA): A complex molecule in the cell’s chromosomes that carries genetic information. Dominant-recessive genes principle: The principle that if one gene of a pair is dominant and one is recessive, the dominant gene overrides the recessive gene. A recessive gene exerts its influence only if both genes of a pair are recessive. Endocrine system: The body system consisting of a set of glands that regulate the activities of certain organs by releasing their chemical products into the bloodstream. Forebrain: The brain’s largest division and its most forward part. Frontal lobes: The portion of the cerebral cortex behind the forehead, involved in personality, intelligence, and the control of voluntary muscles. Genes: The units of hereditary information, consisting of short segments of chromosomes composed of DNA. Genotype: An individual’s genetic heritage; his or her actual genetic material. Glands: Organs or tissues in the body that create chemicals that control many bodily functions. Glial cells: The second of two types of cells in the nervous system; glial cells (also called glia) provide support, nutritional benefits, and other functions and keep neurons running smoothly. Hindbrain: Located at the skull’s rear, the lowest portion of the brain, consisting of the medulla, cerebellum, and pons. Hippocampus: The structure in the limbic system that has a special role in the storage of memories. Hormones: Chemical messengers that are produced by the endocrine glands and carried by the bloodstream to all parts of the body. Hypothalamus: A small forebrain structure, located just below the thalamus, that monitors three pleasurable activities—eating, drinking, and sex—as well as emotion, stress, and reward. Limbic system: A set of subcortical brain structures central to emotion, memory, and reward processing. Midbrain: Located between the hindbrain and forebrain, an area in which many nerve-fiber systems ascend and descend to connect the higher and lower portions of the brain; in particular, the midbrain relays information between the brain and the eyes and ears. Motor cortex: A region in the cerebral cortex, located just behind the frontal lobes, that processes information about voluntary movement. Myelin sheath: A layer of fat cells that encases and insulates most axons. Neocortex: The outermost part of the cerebral cortex, making up 80 percent of the human brain’s cortex. Nervous system: The body’s electrochemical communication circuitry. Neural networks: Networks of nerve cells that integrate sensory input and motor output. Neurons: One of two types of cells in the nervous system; neurons are the nerve cells that handle the information-processing function. Neurotransmitters: Chemical substances that are stored in very tiny sacs within the neuron’s terminal buttons and involved in transmitting information across a synaptic gap to the next neuron. Occipital lobes: Structures located at the back of the head that respond to visual stimuli. Ovaries: Sex-related endocrine glands that produce hormones involved in women’s sexual development and reproduction. Pancreas: A dual-purpose gland under the stomach that performs both digestive and endocrine functions. Parasympathetic nervous system: The part of the autonomic nervous system that calms the body. Parietal lobes: Structures at the top and toward the rear of the head that are involved in registering spatial location, attention, and motor control. Peripheral nervous system (PNS): The network of nerves that connects the brain and spinal cord to other parts of the body. Phenotype: An individual’s observable characteristics. Pituitary gland: A pea-sized gland just beneath the hypothalamus that controls growth and regulates other glands. Plasticity: The brain’s special capacity for change. Prefrontal cortex: an important part of the frontal lobes that is involved in higher cognitive functions such as planning, reasoning, and self-control. Resting potential, The stable, negative charge of an inactive neuron. Reticular formation: A system in the midbrain comprising a diffuse collection of neurons involved in stereotyped patterns of behavior such as walking, sleeping, and turning to attend to a sudden noise. Somatic nervous system: The body system consisting of the sensory nerves, whose function is to convey information from the skin and muscles to the central nervous system about conditions such as pain and temperature, and the motor nerves, whose function is to tell muscles what to do. Somatosensory cortex: A region in the cerebral cortex that processes information about body sensations, located at the front of the parietal lobes. Stem cells: Unique primitive cells that have the capacity to develop into most types of human cells. Stress: The responses of individuals to environmental stressors. Stressors: Circumstances and events that threaten individuals and tax their coping abilities and that cause physiological changes to ready the body to handle the assault of stress. Sympathetic nervous system: The part of the autonomic nervous system that arouses the body to mobilize it for action and thus is involved in the experience of stress. Synapses: Tiny spaces between neurons; the gaps between neurons are referred to as synaptic gaps. Temporal lobes: Structures in the cerebral cortex that are located just above the ears and are involved in hearing, language processing, and memory. Testes: Sex-related endocrine glands in the scrotum that produce hormones involved in men’s sexual development and reproduction. Thalamus: The forebrain structure that sits at the top of the brain stem in the brain’s central core and serves as an important relay station. Left Hemisphere • verbal processing, speech, grammar Right Hemisphere • spatial perception • visual recognition • emotion Chapter 3 Sensation and Perception Absolute threshold: The minimum amount of stimulus energy that a person can detect. Apparent movement: The perception that a stationary object is moving. Auditory nerve: The nerve structure that receives information about sound from the hair cells of the inner ear and carries these neural impulses to the brain’s auditory areas. Binding: In the sense of vision, the bringing together and integration of what is processed by different neural pathways or cells. Binocular cues: Depth cues that depend on the combination of the images in the left and right eyes and on the way the two eyes work together. Bottom-up processing: The operation in sensation and perception in which sensory receptors register information about the external environment and send it up to the brain for interpretation. Cones: The receptor cells in the retina that allow for color perception. Convergence: A binocular cue to depth and distance in which the muscle movements in an individual’s two eyes provide information about how deep and/or far away something is. Depth perception: The ability to perceive objects three-dimensionally. Difference threshold: The degree of difference that must exist between two stimuli before the difference is detected. Feature detectors: Neurons in the brain’s visual system that respond to particular features of a stimulus. Figure-ground relationship: The principle by which we organize the perceptual field into stimuli that stand out (figure) and those that are left over (ground). Frequency theory: Theory on how the inner ear registers the frequency of sound, stating that the perception of a sound’s frequency depends on how often the auditory nerve fires. Gestalt psychology A school of thought interested in how people naturally organize their perceptions according to certain patterns. Inner ear: The part of the ear that includes the oval window, cochlea, and basilar membrane and whose function is to convert sound waves into neural impulses and send them to the brain. Kinesthetic senses: Senses that provide information about movement, posture, and orientation. Middle ear: The part of the ear that channels and amplifies sound through the eardrum, hammer, anvil, and stirrup to the inner ear. Monocular cues: Powerful depth cues available from the image in one eye, either the right or the left. Noise: Irrelevant and competing stimuli—not only sounds but also any distracting stimuli for the senses. Olfactory epithelium: The lining of the roof of the nasal cavity, containing a sheet of receptor cells for smell. Opponent-process theory: Theory stating that cells in the visual system respond to complementary pairs of red-green and blue-yellow colors; a given cell might be excited by red and inhibited by green, whereas another cell might be excited by yellow and inhibited by blue. Optic nerve: The structure at the back of the eye, made up of axons of the ganglion cells, that carries visual information to the brain for further processing. Outer ear: The outermost part of the ear, consisting of the pinna and the external auditory canal. Pain: The sensation that warns an individual of damage to the body. Papillae: Rounded bumps above the tongue’s surface that contain the taste buds, the receptors for taste. parallel processing: The simultaneous distribution of information across different neural pathways. Perception: The process of organizing and interpreting sensory information so that it makes sense. perceptual constancy: The recognition that objects are constant and unchanging even though sensory input about them is changing. perceptual set A predisposition or readiness to perceive something in a particular way. place theory: Theory on how the inner ear registers the frequency of sound, stating that each frequency produces vibrations at a particular spot on the basilar membrane. retina The multilayered light-sensitive surface in the eye that records electromagnetic energy and converts it to neural impulses for processing in the brain. Rods: The receptor cells in the retina that are sensitive to light but not very useful for color vision. selective attention: The act of focusing on a specific aspect of experience while ignoring others. semicircular canals: Three fluid-filled circular tubes in the inner ear containing the sensory receptors that detect head motion caused when an individual tilts or moves the head and/or the body. Sensation: The process of receiving stimulus energies from the external environment and transforming those energies into neural energy. sensory adaptation: A change in the responsiveness of the sensory system based on the average level of surrounding stimulation. sensory receptors: Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and the brain. signal detection theory: An approach to perception that focuses on decision making about stimuli in the presence of uncertainty. subliminal perception The detection of information below the level of conscious awareness. Thermoreceptors: Sensory nerve endings under the skin that respond to changes in temperature at or near the skin and provide input to keep the body’s temperature at 98.6 degrees Fahrenheit. top-down processing The operation in sensation and perception, launched by cognitive processing at the brain’s higher levels, that allows the organism to sense what is happening and to apply that framework to information from the world. trichromatic theory: Theory stating that color perception is produced by three types of cone receptors in the retina that are particularly sensitive to different, but overlapping, ranges of wavelengths. vestibular sense: Sense that provides information about balance and movement. visual cortex: Located in the occipital lobe, the part of the cerebral cortex involved in vision. volley principle: Principle addressing limitations of the frequency theory of hearing, stating that a cluster of nerve cells can fire neural impulses in rapid succession, producing a volley of impulses. Weber’s law: The principle that two stimuli must differ by a constant minimum percentage (rather than a constant amount) to be perceived as different.