Free TEAS 7 Science Practice Test 10 — 30 Questions With Full Explanations

Question 1. Anatomy & Physiology easy

During pregnancy, which structure connects the developing fetus to the wall of the uterus and permits the exchange of oxygen, nutrients, and waste products between maternal and fetal blood?

• A. Umbilical cord
• B. Amniotic sac
• C. Placenta (correct)
• D. Yolk sac

Explanation: The placenta attaches the fetus to the uterine wall and is the site where oxygen, nutrients, and wastes diffuse between maternal and fetal blood. The umbilical cord only carries blood between fetus and placenta, the amniotic sac cushions the fetus, and the yolk sac is a vestigial early structure.

Question 2. Anatomy & Physiology easy

Which skin gland secretes an oily substance called sebum that lubricates the skin and hair and helps inhibit bacterial growth?

• A. Sebaceous gland (correct)
• B. Eccrine gland
• C. Ceruminous gland
• D. Apocrine gland

Explanation: Sebaceous glands are attached to hair follicles and release sebum, an oily mixture that waterproofs and lubricates skin and hair and has mild antibacterial action. Eccrine glands secrete watery sweat for cooling, apocrine glands produce thicker sweat, and ceruminous glands make earwax.

Question 3. Anatomy & Physiology medium

Damage to which region of the brain most characteristically impairs the ability to form new long-term memories while older memories remain intact?

• A. Cerebellum
• B. Thalamus
• C. Medulla oblongata
• D. Hippocampus (correct)

Explanation: The hippocampus, deep in the medial temporal lobe, is essential for consolidating new long-term memories; damage characteristically causes anterograde amnesia in which new memories cannot form. The cerebellum coordinates movement, the thalamus relays sensory information, and the medulla controls vital reflexes such as breathing and heart rate.

Question 4. Anatomy & Physiology medium

Rotational movement of the head is sensed mainly by which fluid-filled structures of the inner ear, which are important for the sense of equilibrium?

• A. Cochlea
• B. Semicircular canals (correct)
• C. Ossicles
• D. Tympanic membrane

Explanation: The three semicircular canals contain endolymph and hair cells that bend as the head rotates, generating signals about rotational equilibrium. The cochlea detects sound, the ossicles transmit vibration across the middle ear, and the tympanic membrane is the eardrum that vibrates with incoming sound waves, so none of them sense rotation.

Question 5. Anatomy & Physiology medium

Which ion is the most abundant positively charged electrolyte inside the intracellular fluid of a typical body cell?

• A. Sodium
• B. Calcium
• C. Magnesium
• D. Potassium (correct)

Explanation: Potassium is the dominant intracellular cation, with a concentration near 140 mEq/L inside cells, while sodium dominates the extracellular fluid. The sodium-potassium pump exports sodium and imports potassium to maintain this gradient, which underlies the resting membrane potential of excitable cells.

Question 6. Anatomy & Physiology medium

During the rising (depolarizing) phase of an action potential in a neuron, which ion moves rapidly into the cell through voltage-gated channels?

• A. Sodium (correct)
• B. Potassium
• C. Chloride
• D. Calcium

Explanation: Voltage-gated sodium channels open first during an action potential, and sodium ions rush into the neuron, making the interior more positive and driving depolarization. Potassium efflux later restores the resting potential, chloride usually stabilizes the membrane, and calcium is not the main ion of the rising phase in neurons.

Question 7. Anatomy & Physiology medium

Which cells of the immune system directly destroy infected or abnormal body cells by releasing perforin and granzymes, and are the main effectors of cell-mediated immunity?

• A. Cytotoxic T lymphocytes (correct)
• B. Plasma cells
• C. Helper T cells
• D. Regulatory T cells

Explanation: Cytotoxic (CD8+) T lymphocytes kill infected and tumor cells by releasing perforin, which forms pores in the target membrane, and granzymes, which trigger apoptosis; this is cell-mediated immunity. Plasma cells secrete antibodies in humoral immunity, helper T cells coordinate other immune cells, and regulatory T cells suppress immune responses.

Question 8. Anatomy & Physiology medium

Which type of cartilage, known for resisting compression and tension, forms the intervertebral discs and the pubic symphysis?

• A. Hyaline cartilage
• B. Elastic cartilage
• C. Articular cartilage
• D. Fibrocartilage (correct)

Explanation: Fibrocartilage contains thick bundles of collagen fibers that give it great tensile strength and compressibility, suiting structures that bear heavy loads such as intervertebral discs and the pubic symphysis. Hyaline cartilage covers joint surfaces and forms the fetal skeleton, while elastic cartilage, found in the ear, is more flexible.

Question 9. Anatomy & Physiology hard

Which microscopic cylindrical unit, containing concentric rings of mineralized matrix around a central canal, is the basic structural unit of compact bone?

• A. Osteon (correct)
• B. Trabecula
• C. Osteocyte
• D. Lacuna

Explanation: Compact bone is organized into osteons (Haversian systems): concentric lamellae of calcified matrix arranged around a central Haversian canal that carries blood vessels and nerves. Trabeculae are the branching struts of spongy bone, osteocytes are mature bone cells, and lacunae are the small cavities that house osteocytes.

Question 10. Anatomy & Physiology hard

The knee-jerk (patellar) reflex, in which tapping the patellar tendon causes the quadriceps muscle to contract, is initiated when which type of receptor is stretched?

• A. Muscle spindle (correct)
• B. Golgi tendon organ
• C. Nociceptor
• D. Pacinian corpuscle

Explanation: Muscle spindles are stretch receptors embedded within skeletal muscle that sense changes in muscle length; tapping the patellar tendon stretches the quadriceps spindles and triggers a monosynaptic stretch reflex that contracts the muscle. Golgi tendon organs sense tension in tendons, nociceptors detect pain, and Pacinian corpuscles sense deep pressure and vibration.

Question 11. Anatomy & Physiology hard

When the atria of the heart are stretched by an increase in blood volume, which hormone is released that promotes sodium and water excretion by the kidneys and thereby lowers blood pressure?

• A. Aldosterone
• B. Antidiuretic hormone (ADH)
• C. Atrial natriuretic peptide (ANP) (correct)
• D. Renin

Explanation: Atrial natriuretic peptide is secreted by atrial muscle cells when stretched by high blood volume; it increases sodium excretion, promotes water loss, inhibits renin and aldosterone, and opposes vasoconstriction, lowering blood pressure. Aldosterone and ADH retain sodium and water and raise pressure, while renin activates the angiotensin pathway that also raises pressure.

Question 12. Anatomy & Physiology medium

Which cranial nerve carries most of the parasympathetic outflow to the thoracic and abdominal organs and, when active, slows the heart rate?

• A. Trigeminal nerve
• B. Vagus nerve (correct)
• C. Facial nerve
• D. Hypoglossal nerve

Explanation: The vagus nerve (cranial nerve X) is the main parasympathetic nerve, supplying the heart, lungs, and digestive organs; its activation slows the sinoatrial node and reduces heart rate, promoting rest-and-digest activity. The trigeminal nerve serves facial sensation and chewing, the facial nerve controls muscles of facial expression, and the hypoglossal nerve moves the tongue.

Question 13. Biology easy

During DNA replication, which enzyme unwinds and separates the two strands of the DNA double helix by breaking the hydrogen bonds between base pairs?

• A. Helicase (correct)
• B. DNA polymerase
• C. Ligase
• D. Primase

Explanation: Helicase untwists the double helix and breaks the hydrogen bonds between complementary bases, creating a replication fork where new strands are built. DNA polymerase synthesizes the new DNA strand, ligase seals nicks between Okazaki fragments on the lagging strand, and primase lays down short RNA primers to begin synthesis.

Question 14. Biology medium

To determine whether an organism that shows a dominant trait is homozygous dominant or heterozygous, a geneticist crosses it with which type of individual?

• A. Homozygous dominant individual
• B. Heterozygous individual with the same trait
• C. Individual of a different species
• D. Homozygous recessive individual (correct)

Explanation: A test cross mates the unknown-dominant organism with a homozygous recessive individual: if any offspring show the recessive phenotype, the parent must be heterozygous, whereas all dominant offspring suggest homozygosity. Crossing with another dominant individual cannot reveal hidden recessive alleles, and a different species cannot produce fertile offspring.

Question 15. Biology medium

When a red-flowered snapdragon (RR) is crossed with a white-flowered snapdragon (rr), all offspring are pink (Rr) because neither allele fully dominates the other. This pattern of inheritance is called

• A. Complete dominance
• B. Incomplete dominance (correct)
• C. Codominance
• D. Sex-linked inheritance

Explanation: In incomplete dominance the heterozygote shows an intermediate phenotype, as in pink snapdragon flowers, because the dominant allele's product is present in reduced amount. Codominance expresses both alleles fully at once, as in AB blood type, complete dominance completely masks one allele, and sex linkage refers to genes carried on sex chromosomes.

Question 16. Biology medium

In a eukaryotic cell, the citric acid (Krebs) cycle takes place in which location?

• A. Cytoplasm
• B. Outer mitochondrial membrane
• C. Inner mitochondrial membrane
• D. Mitochondrial matrix (correct)

Explanation: The citric acid cycle runs in the mitochondrial matrix, where acetyl-CoA is fully oxidized and carbon dioxide, NADH, FADH2, and ATP are produced by enzymes dissolved in the matrix. Glycolysis occurs in the cytoplasm, the electron transport chain is embedded in the inner mitochondrial membrane, and the outer membrane plays little role in respiration.

Question 17. Biology hard

In a dihybrid cross between two pea plants heterozygous for both traits (AaBb x AaBb), what fraction of the offspring is expected to show the dominant phenotype for BOTH traits?

• A. 3/16
• B. 6/16
• C. 9/16 (correct)
• D. 12/16

Explanation: Each gene segregates independently, so the probability of the dominant phenotype for one gene is 3/4; by the product rule the chance of both dominant phenotypes is 3/4 x 3/4 = 9/16. The 3/16 class shows one dominant and one recessive trait, and only 1/16 shows both recessive traits.

Question 18. Biology hard

In a large population at Hardy-Weinberg equilibrium, the frequency of the recessive allele q is 0.2. What is the expected frequency of heterozygous carriers (2pq)?

• A. 0.04
• B. 0.64
• C. 0.32 (correct)
• D. 0.16

Explanation: Because p + q = 1, p = 1 - 0.2 = 0.8. The heterozygote frequency is 2pq = 2 x 0.8 x 0.2 = 0.32. The 0.64 value is p squared, the frequency of dominant homozygotes, and 0.04 is q squared, the frequency of recessive homozygotes, so the three genotype classes sum to 1.

Question 19. Chemistry easy

Which type of nuclear radiation consists of a particle identical to the nucleus of a helium atom, containing two protons and two neutrons?

• A. Alpha particle (correct)
• B. Beta particle
• C. Gamma ray
• D. Neutron emission

Explanation: An alpha particle is a helium nucleus (two protons and two neutrons) ejected during radioactive decay; it is large, doubly charged, and easily stopped by paper or skin. A beta particle is a fast-moving electron, gamma radiation is high-energy electromagnetic waves, and neutron emission releases uncharged particles.

Question 20. Chemistry medium

A chemist dilutes 100 mL of a 6.0 M hydrochloric acid solution by adding water to a final volume of 300 mL. What is the new concentration of the solution?

• A. 1.5 M
• B. 2.0 M (correct)
• C. 3.0 M
• D. 18 M

Explanation: Dilution conserves the number of moles of solute: M1V1 = M2V2, so (6.0 M)(0.100 L) = M2(0.300 L), which gives M2 = 0.60/0.30 = 2.0 M. The volume tripled, so the concentration falls to one third of its original value; 18 M would require concentrating the solution, not diluting it.

Question 21. Chemistry medium

Naturally occurring chlorine is a mixture of about 75% chlorine-35 atoms and 25% chlorine-37 atoms. What is the average atomic mass of chlorine?

• A. 35.0 amu
• B. 36.0 amu
• C. 35.5 amu (correct)
• D. 37.0 amu

Explanation: The weighted average is (0.75 x 35) + (0.25 x 37) = 26.25 + 9.25 = 35.5 amu, which matches the period table value. A simple average of 36.0 would ignore the greater abundance of the lighter isotope, and the endpoint values treat chlorine as if it were a single isotope.

Question 22. Chemistry medium

A radioactive isotope has a half-life of 10 days. What fraction of a sample remains after 30 days?

• A. 1/2
• B. 1/4
• C. 1/16
• D. 1/8 (correct)

Explanation: Thirty days equals exactly three half-lives, so the fraction remaining is (1/2) raised to the third power, which equals 1/8. After one half-life half remains, after two half-lives one quarter remains, and 1/16 would require four half-lives, or 40 days. Each half-life halves the amount present at the start of that period.

Question 23. Chemistry hard

For the equilibrium reaction N2(g) + 3 H2(g) forming 2 NH3(g), what happens to the position of equilibrium when the pressure is increased by compressing the mixture at constant temperature?

• A. It shifts toward reactants
• B. It does not change
• C. It shifts equally in both directions
• D. It shifts toward products (correct)

Explanation: Le Chatelier's principle states that increasing pressure shifts equilibrium toward the side with fewer moles of gas. Here the product side has 2 moles of gas versus 4 moles on the reactant side, so the equilibrium shifts toward ammonia, favoring the forward reaction and relieving the added pressure.

Question 24. Chemistry hard

A titration requires 25.0 mL of 0.10 M sodium hydroxide to exactly neutralize 50.0 mL of a hydrochloric acid solution. What is the concentration of the HCl solution?

• A. 0.025 M
• B. 0.05 M (correct)
• C. 0.10 M
• D. 0.20 M

Explanation: At the equivalence point the moles of H+ equal the moles of OH-: (0.10 M)(0.0250 L) = CHCl(0.0500 L), so CHCl = 0.0025 moles / 0.0500 L = 0.05 M. Because the acid volume is twice the base volume, the acid must be half as concentrated to contain the same number of moles of reactive ions.

Question 25. Scientific Reasoning easy

A student records the number of petals on flowers in a garden: 3, 3, 4, 5, 5, 5, 7. What is the mode of this data set?

• A. 3
• B. 4
• C. 5 (correct)
• D. 7

Explanation: The mode is the value that occurs most frequently in a data set. The number 5 appears three times, while 3 appears twice and 4 and 7 appear once each, so the mode is 5. Note that the mean of the seven values is 32/7, about 4.6, which shows the mode can differ from the mean.

Question 26. Scientific Reasoning easy

A researcher surveys 200 students selected from a high school of 2,000 students to estimate study habits. In this study, the entire group of 2,000 students is called the

• A. Population (correct)
• B. Sample
• C. Variable
• D. Control group

Explanation: The population is the complete set of individuals about whom the researcher wants to draw conclusions, here all 2,000 students. The 200 students who were actually surveyed are the sample, a subset used to estimate population values; a variable is a measured characteristic, and a control group is a comparison group in an experiment.

Question 27. Scientific Reasoning medium

A scientific law is best characterized as which of the following?

• A. A guess about how a phenomenon might work
• B. A concise statement of a consistently observed natural pattern (correct)
• C. A detailed mechanism proposed to explain observations
• D. A conclusion based on a single anecdote

Explanation: A scientific law summarizes an observed, consistent pattern in nature, often as a concise mathematical relationship, such as Boyle's law for gas pressure and volume. A guess about how a phenomenon works is a hypothesis, a detailed explanatory mechanism is a theory, and a single anecdote cannot support a general law.

Question 28. Scientific Reasoning medium

On a scatterplot of two variables, the points cluster along a line that slopes downward from left to right. Which relationship do the variables most likely have?

• A. A strong positive correlation
• B. A negative correlation (correct)
• C. No correlation at all
• D. A causal relationship in both directions

Explanation: A downward-sloping pattern means that as one variable increases, the other tends to decrease, which is a negative (inverse) correlation. An upward slope indicates a positive correlation, random scatter without a trend indicates no correlation, and correlation alone cannot establish causation regardless of the direction or strength of the relationship.

Question 29. Scientific Reasoning hard

In a normal (bell-shaped) distribution, approximately what percentage of the data falls within one standard deviation of the mean?

• A. 68% (correct)
• B. 50%
• C. 95%
• D. 99.7%

Explanation: The empirical rule for a normal distribution states that about 68% of observations lie within one standard deviation of the mean, about 95% lie within two standard deviations, and about 99.7% lie within three. The 50% value is not a fixed percentage for any standard deviation interval in a normal curve.

Question 30. Scientific Reasoning hard

In a distribution of household incomes, most households earn moderate amounts while a small number earn extremely large amounts, producing a long tail on the right. How is this distribution best described?

• A. Symmetric
• B. Negatively skewed
• C. Positively skewed (correct)
• D. Bimodal

Explanation: A distribution with a long tail extending toward high values is positively skewed (right-skewed), and the few extremely large values typically pull the mean above the median. A left-skewed distribution has its long tail on the low end, a symmetric distribution has balanced tails, and a bimodal distribution has two distinct peaks.