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TASC Transdisciplinary Science study materials
TASC Transdisciplinary Science study resources

TASC Transdisciplinary Science practice questions

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Question 1Life Science (Biology)

Which organelle is the primary site of ATP production in eukaryotic cells?

  1. Lysosome
  2. Ribosome
  3. Mitochondrion Correct answer.
  4. Golgi apparatus

Explanation

Mitochondria carry out aerobic cellular respiration, using the electron transport chain and chemiosmosis to generate most of the cell's ATP. Ribosomes build proteins, the Golgi modifies and packages them, and lysosomes handle digestion, so none of those organelles is the main ATP source.

Question 2Life Science (Biology)

During which phase of mitosis do sister chromatids separate and move toward opposite poles?

  1. Anaphase Correct answer.
  2. Telophase
  3. Metaphase
  4. Prophase

Explanation

Anaphase begins when cohesin is cleaved and spindle fibers shorten, pulling each sister chromatid to opposite poles. Prophase involves condensation, metaphase involves alignment at the equator, and telophase involves nuclear envelope reformation.

Question 3Life Science (Biology)

A molecule that speeds up a reaction by lowering activation energy without being consumed is called a(n):

  1. Catalyst Correct answer.
  2. Substrate
  3. Product
  4. Inhibitor

Explanation

A catalyst increases reaction rate by lowering the activation energy barrier and is regenerated unchanged afterward. Substrates are the reactants being converted, products are the results, and inhibitors slow reactions rather than accelerate them.

Question 4Life Science (Biology)

Which molecule carries the amino acid to the ribosome during translation?

  1. mRNA
  2. rRNA
  3. DNA polymerase
  4. tRNA Correct answer.

Explanation

Transfer RNA has an anticodon that base-pairs with the mRNA codon and carries the matching amino acid to the growing polypeptide. Messenger RNA supplies the codon sequence, ribosomal RNA forms the ribosome's core, and DNA polymerase functions in replication.

Question 5Life Science (Biology)

In a population, which condition is required for a trait to be acted on by natural selection?

  1. The trait must be identical in every individual
  2. The trait must be acquired during a single lifetime
  3. The trait must reduce survival in all environments
  4. The trait must be inherited and vary among individuals Correct answer.

Explanation

Natural selection requires heritable variation because only inherited differences that affect survival or reproduction can change allele frequencies across generations. Uniform traits offer nothing to select among, acquired traits are not passed on genetically, and universal harm would not produce adaptation.

Question 6Life Science (Biology)

Which blood vessel type has the thinnest walls to allow exchange of gases and nutrients with tissues?

  1. Artery
  2. Aorta
  3. Capillary Correct answer.
  4. Vein

Explanation

Capillaries are only one cell layer thick, which minimizes diffusion distance so oxygen, nutrients, and wastes can exchange between blood and tissue fluid. Arteries, veins, and the aorta have thicker walls suited to pressure and transport.

Question 7Life Science (Biology)

Which process converts light energy into chemical energy stored in glucose?

  1. Osmosis
  2. Cellular respiration
  3. Fermentation
  4. Photosynthesis Correct answer.

Explanation

Photosynthesis uses light energy to fix carbon dioxide into glucose, storing energy in chemical bonds. Respiration and fermentation release that energy instead, and osmosis is passive water movement unrelated to energy capture.

Question 8Life Science (Biology)

Which level of ecological organization includes all the living organisms in an area together with the nonliving environment?

  1. Population
  2. Ecosystem Correct answer.
  3. Biome
  4. Community

Explanation

An ecosystem consists of all organisms in an area interacting with the physical environment, including sunlight, water, and soil. A population is one species, a community excludes the nonliving factors, and a biome is a large regional category of similar ecosystems.

Question 9Life Science (Biology)

A cell is placed in a hypertonic solution. What will most likely happen to an animal cell?

  1. It will swell and burst
  2. It will actively pump water inward
  3. It will remain unchanged
  4. It will shrink as water leaves Correct answer.

Explanation

In a hypertonic solution the solute concentration outside is higher than inside, so water moves out by osmosis and the cell shrinks. Swelling and bursting occur in a hypotonic solution, and osmosis is passive rather than an inward pump.

Question 10Life Science (Biology)

An enzyme normally works best at pH 7. If the pH drops to 3, what is the most likely result?

  1. The enzyme converts into a substrate
  2. The enzyme becomes a competitive inhibitor
  3. The enzyme denatures and activity falls Correct answer.
  4. The reaction rate increases sharply

Explanation

Extreme pH changes disrupt hydrogen bonds and ionic interactions that maintain an enzyme's tertiary shape, so the active site loses its fit for the substrate and activity drops. Enzymes do not convert into substrates or inhibitors when denatured.

Question 11Life Science (Biology)

A cross between two heterozygous pea plants (Tt x Tt) produces offspring. What fraction is expected to show the recessive phenotype?

  1. 3/4
  2. 1/4 Correct answer.
  3. 1/2
  4. 0

Explanation

A Tt x Tt cross gives genotype ratios of 1 TT : 2 Tt : 1 tt, so one quarter of the offspring are homozygous recessive and display the recessive trait. The other three quarters carry at least one dominant allele and show the dominant phenotype.

Question 12Life Science (Biology)

A mutation changes a DNA codon but the resulting amino acid stays the same. This type of mutation is called:

  1. Silent Correct answer.
  2. Frameshift
  3. Deletion
  4. Nonsense

Explanation

A silent mutation alters a codon but, because the genetic code is degenerate, still specifies the same amino acid. Nonsense mutations create a stop codon, frameshifts shift the reading frame, and deletions remove nucleotides.

Question 13Life Science (Biology)

In a food chain, only about 10 percent of energy at one trophic level is transferred to the next. What happens to most of the remaining energy?

  1. It is converted into additional biomass
  2. It is stored permanently in the top predator
  3. It is lost as heat through metabolism Correct answer.
  4. It returns directly to the sun

Explanation

Organisms use most assimilated energy for respiration, metabolism, and movement, releasing it as heat, with some lost in waste. Only a small fraction becomes new biomass available to the next trophic level.

Question 14Life Science (Biology)

Which statement best describes the role of decomposers in an ecosystem?

  1. They prey on primary consumers
  2. They break down dead matter and recycle nutrients Correct answer.
  3. They convert atmospheric nitrogen into ammonia
  4. They capture sunlight to make glucose

Explanation

Decomposers such as fungi and bacteria break down dead organisms and wastes, releasing nutrients like carbon and nitrogen back into the soil and water for reuse by producers. Nitrogen fixation, photosynthesis, and predation are performed by other groups.

Question 15Life Science (Biology)

A human cell with 46 chromosomes undergoes meiosis. How many chromosomes does each resulting gamete contain?

  1. 23 Correct answer.
  2. 12
  3. 46
  4. 92

Explanation

Meiosis halves the chromosome number so each gamete is haploid, containing one chromosome from each homologous pair. In humans that means 23 chromosomes, restoring 46 at fertilization.

Question 16Life Science (Biology)

Which part of the human nervous system controls involuntary functions such as heart rate and digestion?

  1. Autonomic nervous system Correct answer.
  2. Somatic nervous system
  3. Skeletal muscle system
  4. Sensory receptor system

Explanation

The autonomic nervous system regulates smooth muscle, cardiac muscle, and glands, governing involuntary processes like heartbeat and digestion. The somatic system controls voluntary skeletal muscle movement.

Question 17Life Science (Biology)

A bacterial population is exposed to an antibiotic, and a few cells survive because they already carry a resistance gene. Over generations, the population becomes mostly resistant. This is an example of:

  1. Artificial selection
  2. Stabilizing selection
  3. Directional selection Correct answer.
  4. Genetic drift

Explanation

Directional selection occurs when one extreme phenotype, here resistance, is favored and shifts the population's allele frequencies in that direction. Stabilizing selection favors intermediates, genetic drift is random change, and artificial selection is human-directed breeding.

Question 18Life Science (Biology)

Which property of water allows insects to walk on the surface of a pond?

  1. Surface tension from hydrogen bonding Correct answer.
  2. High specific heat
  3. Its ability to dissolve salts
  4. Its low density as a solid

Explanation

Hydrogen bonds between water molecules create strong cohesive forces at the surface, producing surface tension that can support small insects. High specific heat, solvent ability, and ice density relate to other properties.

Question 19Life Science (Biology)

In a pedigree, a trait appears only in males and is passed from an affected father to all of his sons but none of his daughters. Which inheritance pattern best fits?

  1. Mitochondrial
  2. Autosomal dominant
  3. X-linked recessive
  4. Y-linked Correct answer.

Explanation

A Y-linked trait is carried on the Y chromosome, so it passes from father to son and never to daughters, and only males express it. X-linked traits affect daughters depending on the mother's alleles, autosomal traits affect both sexes, and mitochondrial traits pass through mothers.

Question 20Life Science (Biology)

A student measures the rate of an enzyme reaction at increasing substrate concentrations and finds the rate levels off. What best explains the plateau?

  1. Temperature has fallen to zero
  2. All active sites are occupied by substrate Correct answer.
  3. The enzyme has changed into a product
  4. The substrate has been completely destroyed

Explanation

At high substrate levels the reaction rate plateaus because enzyme active sites become saturated, so adding more substrate cannot increase the rate further. The maximum rate reflects enzyme concentration and turnover number.

Question 21Life Science (Biology)

Two species of birds live in the same forest and eat insects from different heights in the trees. This separation most directly reduces which interaction?

  1. Commensalism
  2. Mutualism
  3. Competition Correct answer.
  4. Parasitism

Explanation

When species use different parts of a resource, they partition the niche and reduce competition for food. Mutualism, parasitism, and commensalism describe other interspecies relationships not resolved by resource partitioning.

Question 22Life Science (Biology)

In a eukaryotic gene, a mutation in a splice site causes an intron to remain in the mature mRNA. What is the most likely consequence?

  1. The gene will be replicated incorrectly
  2. The mRNA will be translated normally
  3. The protein may be truncated or misfolded Correct answer.
  4. The mRNA will become double-stranded DNA

Explanation

A retained intron adds extra nucleotides to the coding sequence, shifting the reading frame or introducing a premature stop codon, which typically yields a truncated or nonfunctional protein. Splicing errors affect mRNA processing, not DNA replication.

Question 23Life Science (Biology)

A cell is treated with a drug that blocks the Krebs cycle. Which outcome is most directly expected?

  1. Oxygen consumption increases
  2. Glycolysis stops immediately
  3. Carbon dioxide production increases
  4. ATP yield from aerobic respiration falls sharply Correct answer.

Explanation

The Krebs cycle supplies NADH and FADH2 to the electron transport chain, so blocking it sharply reduces oxidative ATP production. Glycolysis can continue briefly because it does not require the cycle, and carbon dioxide output would fall rather than rise.

Question 24Life Science (Biology)

A population of lizards on an island has very low genetic diversity after a bottleneck. Which risk is most directly increased?

  1. Higher rate of crossing over
  2. Reduced ability to adapt to a new disease Correct answer.
  3. Increased gene flow from the mainland
  4. Faster mutation rate

Explanation

A bottleneck reduces allele diversity, so if a new pathogen appears the population may lack resistant alleles and adapt more slowly. Mutation rate, crossing over, and migration are not directly increased by a loss of diversity.

Question 25Life Science (Biology)

Two populations of the same species are separated by a mountain range for many generations. Which outcome best illustrates allopatric speciation?

  1. They accumulate genetic differences and become reproductively isolated Correct answer.
  2. They develop identical allele frequencies
  3. They interbreed more frequently each generation
  4. They merge into a single population

Explanation

Geographic separation prevents gene flow, so mutation, drift, and selection cause the populations to diverge until reproductive isolation evolves, which is allopatric speciation. Continued interbreeding or merging would prevent divergence.

Question 26Life Science (Biology)

Which organelle is the main site of ATP production in a eukaryotic cell?

  1. Lysosome
  2. Ribosome
  3. Golgi apparatus
  4. Mitochondrion Correct answer.

Explanation

Mitochondria carry out aerobic respiration, using the electron transport chain to build a proton gradient whose flow drives ATP synthase. Most of a cell's ATP is therefore made in this organelle.

Question 27Life Science (Biology)

Which cell structure controls what enters and leaves the cell?

  1. Cell wall
  2. Cytoskeleton
  3. Plasma membrane Correct answer.
  4. Nucleolus

Explanation

The plasma membrane is a phospholipid bilayer with embedded proteins that regulates the passage of substances. Its selective permeability keeps the internal environment distinct from the surroundings.

Question 28Life Science (Biology)

Which group of organisms converts atmospheric nitrogen into forms plants can use?

  1. Fungi that decompose wood
  2. Primary consumers
  3. Nitrogen-fixing bacteria Correct answer.
  4. Photosynthetic algae

Explanation

Certain bacteria, many living in root nodules, use the enzyme nitrogenase to reduce atmospheric N2 to ammonia. Plants can then absorb this fixed nitrogen to build proteins and nucleic acids.

Question 29Life Science (Biology)

Which type of cell division produces genetically identical daughter cells for growth and repair?

  1. Meiosis
  2. Mitosis Correct answer.
  3. Binary fission
  4. Fertilization

Explanation

Mitosis separates replicated chromosomes so each daughter cell receives an identical diploid set. This supports growth, replacement of damaged tissue, and asexual reproduction in many organisms.

Question 30Life Science (Biology)

Which human body system transports oxygen and nutrients to cells throughout the body?

  1. Endocrine system
  2. Circulatory system Correct answer.
  3. Integumentary system
  4. Skeletal system

Explanation

The circulatory system uses blood vessels and the heart to move blood carrying oxygen, nutrients, and wastes. Blood delivers these materials to tissues and removes carbon dioxide.

Question 31Life Science (Biology)

Which characteristic is shared by all living organisms?

  1. They maintain a stable internal environment. Correct answer.
  2. They move from place to place.
  3. They contain chlorophyll.
  4. They reproduce sexually.

Explanation

Homeostasis, the regulation of internal conditions within tolerable limits, is a universal property of life. It allows cells and organisms to keep functioning despite changes in the surroundings.

Question 32Life Science (Biology)

Which biological molecule is the primary source of quick energy for cells and includes sugars and starches?

  1. Lipids
  2. Carbohydrates Correct answer.
  3. Proteins
  4. Nucleic acids

Explanation

Carbohydrates such as glucose are broken down in respiration to release energy rapidly. Starch and glycogen serve as stored forms of this readily available fuel.

Question 33Life Science (Biology)

A plant is kept in the dark for two days and then a leaf is tested with iodine. What result is most likely?

  1. The leaf turns blue-black because starch is present.
  2. The leaf stays brown because the iodine cannot enter cells.
  3. The leaf turns blue-black because chlorophyll was destroyed.
  4. The leaf stays brown because little starch formed. Correct answer.

Explanation

Without light, photosynthesis cannot produce glucose, so little glucose is converted to starch. Iodine detects starch by turning blue-black, so a starch-poor leaf will not show that color change.

Question 34Life Science (Biology)

A person breathes rapidly during intense exercise. Which change in the blood does this response most directly address?

  1. Decreasing blood pressure
  2. Increasing blood glucose
  3. Rising carbon dioxide levels Correct answer.
  4. Falling body temperature

Explanation

Active muscles produce extra carbon dioxide, which lowers blood pH and stimulates faster breathing. Increased ventilation removes carbon dioxide and helps restore normal pH.

Question 35Life Science (Biology)

A protein is synthesized with one wrong amino acid far from its active site, yet it no longer functions. What best explains this?

  1. The active site sequence was directly altered.
  2. The protein's overall folded shape depends on its full sequence. Correct answer.
  3. The wrong amino acid blocked transcription.
  4. The ribosome stopped translation too early.

Explanation

A protein's function depends on its three-dimensional shape, which is determined by interactions among all its amino acids. A distant substitution can distort folding and thereby change the active site indirectly.

Question 36Life Science (Biology)

In a cross between a homozygous dominant plant and a homozygous recessive plant, all offspring show the dominant trait. What are the offspring's genotypes?

  1. Heterozygous Correct answer.
  2. Homozygous dominant
  3. A 1:1 mix of both homozygotes
  4. Homozygous recessive

Explanation

Each parent contributes one allele, so offspring receive one dominant and one recessive allele. Their genotype is therefore heterozygous, and the dominant allele determines the visible trait.

Question 37Life Science (Biology)

A single-celled organism is placed in distilled water. Which observation best indicates that osmosis is occurring?

  1. Solutes move out until concentrations match.
  2. The cell swells as water enters. Correct answer.
  3. The cell shrinks as water leaves.
  4. The cell wall thickens.

Explanation

Distilled water is hypotonic to the cell's interior, so water moves inward across the membrane by osmosis. The resulting swelling is the visible sign of that net water movement.

Question 38Life Science (Biology)

Two organisms share many physical traits, but DNA analysis shows they are only distantly related. What conclusion is best supported?

  1. The physical traits are homologous structures.
  2. The physical traits arose through convergent evolution. Correct answer.
  3. DNA evidence is unreliable for this pair.
  4. The two organisms are the same species.

Explanation

Similar traits that evolve independently in unrelated lineages are analogous and result from convergent evolution. Molecular data reveal the true evolutionary distance that morphology can obscure.

Question 39Life Science (Biology)

A keystone predator is removed from a rocky shore community. Which outcome is most likely?

  1. A prey species may dominate and reduce species diversity. Correct answer.
  2. Energy transfer to higher trophic levels will increase.
  3. The community becomes more diverse and stable.
  4. All other species will immediately become extinct.

Explanation

Keystone predators keep dominant competitors in check, freeing space and resources for other species. Removing the predator often lets one prey species expand and crowd out others, lowering diversity.

Question 40Life Science (Biology)

A cell's DNA is damaged in many places, and the cell cycle halts before replication. Which checkpoint is most likely responsible?

  1. The telophase checkpoint
  2. The metaphase checkpoint
  3. The cytokinesis checkpoint
  4. The G1 checkpoint Correct answer.

Explanation

The G1 checkpoint assesses cell size, nutrients, and DNA integrity before the cell commits to replication. Damage detected there prevents entry into S phase.

Question 41Life Science (Biology)

A scientist wants to determine whether a trait is influenced more by genes or by environment. Which approach is most informative?

  1. Measuring the trait in a single individual over one day
  2. Counting the number of genes in the genome
  3. Comparing identical twins raised apart Correct answer.
  4. Comparing unrelated individuals raised in different environments

Explanation

Identical twins share the same genes, so differences between twins raised apart point to environmental influence. Similarities despite different environments suggest a strong genetic contribution.

Question 42Life Science (Biology)

A population of insects develops resistance to a pesticide over several generations. Which statement best explains this?

  1. Pre-existing resistant variants survived and reproduced more. Correct answer.
  2. The pesticide was diluted by the insects' bodies over time.
  3. The pesticide caused mutations that made insects resistant.
  4. Insects learned to tolerate the pesticide during their lifetime.

Explanation

Variation in resistance already exists in the population, and the pesticide acts as a selective pressure. Resistant individuals survive, reproduce, and pass their alleles on, so resistance becomes more common.

Question 43Life Science (Biology)

Which statement correctly describes the flow of information in cells?

  1. DNA is copied into RNA, which directs protein synthesis. Correct answer.
  2. DNA directly assembles amino acids into proteins.
  3. RNA is copied into DNA, which then makes proteins.
  4. Proteins are copied into RNA, which then makes DNA.

Explanation

The central dogma states that DNA is transcribed into RNA, and RNA is translated into protein. Information therefore flows from nucleic acid to protein, not in reverse under normal conditions.

Question 44Life Science (Biology)

A cell is treated with a drug that prevents the spindle fibers from attaching to chromosomes. Which stage will the cell most likely fail to complete?

  1. Anaphase Correct answer.
  2. Cytokinesis
  3. Prophase
  4. G1 phase

Explanation

In anaphase, sister chromatids are pulled to opposite poles by spindle fibers attached at the centromere. If attachment fails, the spindle checkpoint blocks the transition and anaphase cannot proceed.

Question 45Life Science (Biology)

In a population at Hardy-Weinberg equilibrium, the frequency of a recessive allele is 0.2. What is the expected frequency of homozygous recessive individuals?

  1. 0.80
  2. 0.04 Correct answer.
  3. 0.16
  4. 0.32

Explanation

Homozygous recessive individuals have genotype frequency q squared, where q is the recessive allele frequency. Squaring 0.2 gives 0.04, so about four percent of the population is expected to be homozygous recessive.

Question 46Life Science (Biology)

A molecule inhibits an enzyme by binding to a site other than the active site and changing the enzyme's shape. This is best described as:

  1. Feedback activation
  2. Competitive inhibition
  3. Denaturation by heat
  4. Noncompetitive inhibition Correct answer.

Explanation

Noncompetitive inhibitors bind at an allosteric site and alter the enzyme's conformation so the active site no longer fits the substrate. Because the inhibitor does not occupy the active site, added substrate cannot easily reverse the effect.

Question 47Life Science (Biology)

In a dihybrid cross of two heterozygous individuals for unlinked genes, what proportion of offspring is expected to show both recessive traits?

  1. 9/16
  2. 1/16 Correct answer.
  3. 3/16
  4. 1/4

Explanation

Each gene independently gives a 1/4 chance of the recessive phenotype in a heterozygote cross. Multiplying the independent probabilities, 1/4 times 1/4 equals 1/16 for both recessive traits together.

Question 48Life Science (Biology)

A freshwater fish's body fluids are saltier than the surrounding water, so water tends to enter its body. Which adaptation best helps it maintain water balance?

  1. Actively excreting salts through gills
  2. Producing large volumes of dilute urine Correct answer.
  3. Reducing gill surface area
  4. Drinking large amounts of water

Explanation

A freshwater fish gains water by osmosis and must expel the excess while conserving salts. Producing copious dilute urine removes water without losing much salt, supporting osmoregulation.

Question 49Life Science (Biology)

A sequence of DNA has the template strand reading 3'-TAC-5'. What mRNA codon is transcribed from it?

  1. 5'-UAC-3'
  2. 5'-ATG-3'
  3. 5'-AUG-3' Correct answer.
  4. 5'-TAC-3'

Explanation

Transcription builds mRNA complementary to the template strand, with uracil replacing thymine. Adenine pairs with the template's thymine, thymine with adenine, and guanine with cytosine, giving AUG.

Question 50Life Science (Biology)

Which process allows a bacterium to transfer DNA to another bacterium through direct cell-to-cell contact?

  1. Transcription
  2. Conjugation Correct answer.
  3. Translation
  4. Transformation

Explanation

Conjugation requires a physical connection, usually a pilus, through which DNA is passed from a donor cell to a recipient cell. Transformation instead takes up free DNA from the environment, while translation and transcription are internal processes for making proteins and RNA.