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Lower Saxony Zentralabitur Biology study materials
Lower Saxony Zentralabitur Biology study resources

Lower Saxony Zentralabitur Biology practice questions

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Question 1Biological inquiry and interpretation of evidence

A researcher predicts that tomato plants given a nitrogen-enriched fertilizer will produce more fruit than plants given a standard fertilizer. In this study, the amount of fruit produced is best described as which of the following?

  1. The hypothesis
  2. A controlled variable
  3. The dependent variable Correct answer.
  4. The independent variable

Explanation

The dependent variable is the measured outcome that responds to the manipulation, which here is fruit yield. The fertilizer type is the factor the researcher deliberately changes, so it is the independent variable rather than the measured result.

Question 2Biological inquiry and interpretation of evidence

A student measures the mass of the same sample five times and obtains nearly identical values, but the balance was never zeroed and reads 2.0 g too high. How should these measurements be described?

  1. Both accurate and precise
  2. Precise but not accurate Correct answer.
  3. Accurate but not precise
  4. Neither accurate nor precise

Explanation

Precision refers to how closely repeated measurements agree with one another, while accuracy refers to how close they are to the true value. Because the readings cluster tightly but are systematically offset by the unzeroed balance, they are precise but inaccurate.

Question 3Biological inquiry and interpretation of evidence

Which of the following best distinguishes a scientific hypothesis from a scientific theory?

  1. A hypothesis is a testable proposed explanation, while a theory is a well-supported explanatory framework built from extensive evidence Correct answer.
  2. A hypothesis is always correct once tested, while a theory remains an untested guess
  3. A hypothesis is a broad framework, while a theory is a single testable prediction
  4. A hypothesis applies only to biology, while a theory applies only to physics

Explanation

In science, a hypothesis is a testable proposed explanation for a specific observation, whereas a theory is a broad, well-substantiated explanation supported by many lines of evidence. The common usage of theory as a mere guess is incorrect in scientific contexts.

Question 4Biological inquiry and interpretation of evidence

A scientist repeats an experiment several times and obtains consistent results. Which conclusion is most justified?

  1. The findings are reliable and reproducible under the tested conditions Correct answer.
  2. The results now apply to all organisms everywhere
  3. The hypothesis has been proven true beyond any doubt
  4. The experiment has no remaining sources of error

Explanation

Reproducible results indicate reliability, meaning the procedure yields consistent outcomes under the tested conditions. Science does not establish absolute proof, and replication does not eliminate error or guarantee universal applicability.

Question 5Biological inquiry and interpretation of evidence

A graph plots plant height on the y-axis against days of growth on the x-axis. Which statement correctly identifies the placement of these variables?

  1. Days of growth is the independent variable on the x-axis, and height is the dependent variable on the y-axis Correct answer.
  2. Both variables are dependent and should share the x-axis
  3. Days of growth is the dependent variable because it is measured over time
  4. Height is the independent variable on the y-axis, and days of growth is the dependent variable on the x-axis

Explanation

By convention, the independent variable is placed on the x-axis and the dependent variable on the y-axis. Height responds to elapsed time, so time is independent and height is dependent.

Question 6Biological inquiry and interpretation of evidence

A student notices that mold grows on bread left in a warm, humid place but not on bread stored in a dry, cool place. Which of the following is the most appropriate next step in the scientific process?

  1. Formulate a testable hypothesis and design a controlled experiment to test it Correct answer.
  2. Conclude immediately that warmth and moisture cause mold growth
  3. Publish the observation as a confirmed scientific law
  4. Discard the observation because it was not made in a laboratory

Explanation

An observation generates questions that should be framed as a testable hypothesis and examined through a controlled experiment. Reaching a firm causal conclusion from a single uncontrolled observation is premature.

Question 7Biochemistry

Which property of water is most directly responsible for its ability to moderate temperature in living organisms and large bodies of water?

  1. Its low specific heat
  2. Its inability to form hydrogen bonds
  3. Its nonpolar covalent bonds
  4. Its high specific heat Correct answer.

Explanation

Water has a high specific heat because hydrogen bonds must absorb or release substantial energy before water molecules change temperature. This allows water and water-rich organisms to resist large temperature swings, helping maintain homeostasis.

Question 8Cell structure, membranes and division

Which structure is found in a typical plant cell but NOT in a typical animal cell?

  1. Mitochondrion
  2. Nucleus
  3. Ribosome
  4. Cell wall made of cellulose Correct answer.

Explanation

Plant cells have a rigid cell wall composed primarily of cellulose that surrounds the plasma membrane, providing structural support. Animal cells lack a cell wall, relying on the cytoskeleton and extracellular matrix instead.

Question 9Genetics, inheritance and molecular information

Meiosis differs from mitosis in that meiosis produces

  1. Two genetically identical diploid cells
  2. One diploid cell with double the chromosomes
  3. Two haploid cells identical to the parent
  4. Four genetically varied haploid cells Correct answer.

Explanation

Meiosis consists of two divisions that produce four haploid gametes, each with half the chromosome number of the parent. Crossing over and independent assortment generate genetic variation, distinguishing meiosis from the identical-diploid products of mitosis.

Question 10Metabolism

An enzyme lowers the activation energy of a reaction. Which statement best describes how this affects the reaction?

  1. It increases the reaction rate without being consumed in the reaction Correct answer.
  2. It changes the overall free-energy difference between reactants and products
  3. It supplies the energy needed to make an endergonic reaction exergonic
  4. It permanently binds to the product to stop the reaction

Explanation

Enzymes are biological catalysts that lower activation energy, speeding up reactions without being consumed. They do not change the net free-energy difference (delta G) between reactants and products; they only make the reaction reach equilibrium faster.

Question 11Neurobiology

What ionic mechanism is directly responsible for the rapid depolarizing phase of a neuronal action potential once the threshold potential (~ -55 mV) is reached?

  1. Opening of voltage-gated Na+ channels, causing rapid inward influx of Na+ down its electrochemical gradient Correct answer.
  2. Opening of voltage-gated K+ channels, causing rapid outward efflux of K+
  3. Active extrusion of 3 Na+ ions in exchange for 2 K+ ions by the Na+/K+ pump
  4. Opening of ligand-gated Cl- channels, causing hyperpolarizing influx of Cl-

Explanation

When depolarization reaches the threshold potential (~ -55 mV), voltage-gated sodium channels rapidly open. Sodium ions (Na+) rush into the axon down their steep electrical and chemical gradients, depolarizing the membrane potential to approximately +35 to +40 mV.

Question 12Physiology

Which feature allows a steroid hormone to pass directly through the plasma membrane?

  1. Its lipid (hydrophobic) nature lets it dissolve through the phospholipid bilayer Correct answer.
  2. Its large size lets it push proteins aside
  3. Its negative charge attracts it to the membrane interior
  4. Its attachment to a carbohydrate tag opens a channel

Explanation

Steroid hormones are lipid-soluble (hydrophobic), so they can dissolve through the hydrophobic interior of the phospholipid bilayer without a transport protein. Once inside, they typically bind intracellular receptors that act on the DNA to regulate gene expression.

Question 13Ecology

In an energy pyramid, only about 10 percent of the energy at one trophic level is transferred to the next. Most of the remaining energy is

  1. Converted directly into new biomass at the next level
  2. Lost as heat, largely through cellular respiration and metabolic processes Correct answer.
  3. Stored permanently in the soil
  4. Recycled back to producers as light energy

Explanation

At each trophic level, organisms use most of the energy they consume for metabolism and lose much of it as heat through cellular respiration. Only about 10 percent is stored as biomass available to the next level, which limits food chain length.

Question 14Biotechnology

The polymerase chain reaction, or PCR, is mainly used to do what?

  1. Amplify a selected DNA sequence Correct answer.
  2. Destroy all proteins in a sample
  3. Make plant roots bend downward
  4. Measure animal breathing rate directly

Explanation

PCR uses primers, DNA polymerase, nucleotides, and temperature cycling to make many copies of a target DNA region. It is widely used in testing and research.

Question 15Evolution

Which of the following is a necessary condition for natural selection to occur in a population?

  1. All individuals are genetically identical
  2. Heritable variation exists and affects survival or reproduction Correct answer.
  3. The environment never changes
  4. Every individual produces the same number of offspring

Explanation

Natural selection requires heritable variation among individuals and differences in reproductive success linked to that variation. Individuals with advantageous heritable traits leave more offspring, shifting the population's traits over generations.

Question 16Metabolism

In aerobic cellular respiration, where does the citric acid cycle (Krebs cycle) occur in eukaryotic cells?

  1. In the mitochondrial matrix Correct answer.
  2. In the thylakoid lumen only
  3. In the Golgi lumen only
  4. Extracellularly in blood plasma

Explanation

Pyruvate oxidation and the citric acid cycle run in the mitochondrial matrix; the ETC is on the inner membrane.

Question 17Metabolism

Chemiosmotic ATP synthesis in mitochondria depends on:

  1. A proton gradient across the inner mitochondrial membrane driving ATP synthase Correct answer.
  2. Direct phosphorylation of ADP by molecular oxygen in the cytosol
  3. Spontaneous ATP formation without membranes
  4. Only substrate-level phosphorylation in the nucleus

Explanation

Electron transport pumps H⁺ into the intermembrane space; protons flowing back through ATP synthase make ATP (chemiosmosis).

Question 18Metabolism

Which statement about the light-dependent reactions of photosynthesis is accurate?

  1. They occur in the stroma and fix CO₂ into sugar directly
  2. They occur in thylakoid membranes and generate ATP and NADPH (and O₂ from water) Correct answer.
  3. They require no pigments
  4. They only run in mitochondria

Explanation

Photosystems in thylakoid membranes drive electron transport, photophosphorylation, NADPH formation, and O₂ release from H₂O.

Question 19Metabolism

The Calvin cycle (light-independent reactions) primarily:

  1. Splits water in photosystem II
  2. Uses ATP and NADPH to reduce fixed CO₂ into carbohydrates Correct answer.
  3. Oxidizes NADH in the ETC
  4. Produces O₂ as its main carbon product

Explanation

Rubisco fixes CO₂; ATP/NADPH from light reactions drive reduction and regeneration of RuBP, yielding carbohydrate.

Question 20Metabolism

C4 plants reduce photorespiration in hot/dry climates mainly by:

  1. Eliminating all stomata permanently
  2. Concentrating CO₂ at Rubisco via a spatial (or temporal) CO₂ pump using PEP carboxylase Correct answer.
  3. Abandoning photosynthesis entirely at noon
  4. Using only mitochondrial fermentation in leaves

Explanation

C4 anatomy/biochemistry concentrates CO₂ at Rubisco (mesophyll PEP carboxylase → bundle-sheath Calvin cycle), lowering oxygenation.

Question 21Metabolism

Competitive enzyme inhibition is best described as:

  1. Inhibitor binding an allosteric site and always increasing Vmax
  2. Inhibitor competing with substrate for the active site; overcome by high [S] Correct answer.
  3. Permanent destruction of all enzyme molecules by water
  4. Inhibitor removing the need for activation energy

Explanation

Competitive inhibitors resemble substrate and occupy the active site; raising [S] can outcompete them (apparent Km increases).

Question 22Metabolism

Quantitative: If an electron transport chain pumps enough protons for a gradient that yields 2.5 ATP per NADH via oxidative phosphorylation (modern estimate), 10 NADH from complete glucose oxidation would theoretically yield about:

  1. 2.5 ATP total
  2. 25 ATP from those NADH alone (before adding FADH₂ and substrate-level ATP) Correct answer.
  3. 100 ATP from NADH alone
  4. 0 ATP because NADH cannot drive chemiosmosis

Explanation

10 NADH × ~2.5 ATP/NADH ≈ 25 ATP from NADH-linked oxidative phosphorylation (textbook estimate; actual cellular yields vary).

Question 23Metabolism

Oxygen's role in aerobic respiration is best stated as:

  1. The carbon source for glucose synthesis in mitochondria
  2. The terminal electron acceptor of the electron transport chain, forming water Correct answer.
  3. A competitive inhibitor of ATP synthase
  4. A pigment absorbing red light

Explanation

O₂ accepts electrons (and protons) at complex IV, forming H₂O and enabling continued ETC flow.

Question 24Metabolism

Absorption spectra of chlorophyll a show strong peaks in:

  1. Only the green wavelengths, explaining green transmittance/reflection
  2. Blue and red regions, with relatively poor absorption of green Correct answer.
  3. Only infrared
  4. Only UV-C below 200 nm as the sole peak

Explanation

Chlorophyll a absorbs mainly blue and red; green is relatively poorly absorbed, so leaves appear green.

Question 25Metabolism

If a poison blocks ATP synthase but the ETC still runs briefly, what happens to the proton gradient?

  1. It disappears instantly with no pumping
  2. It typically builds up (hyper-energizes) because protons are pumped but cannot re-enter through ATP synthase Correct answer.
  3. ATP concentration rises without limit
  4. Oxygen consumption becomes impossible forever while gradient is zero

Explanation

Blocking synthase traps protons outside; gradient rises and eventually feedback-slows the ETC - classic uncoupler/inhibitor contrast items.

Question 26Metabolism

An uncoupler of oxidative phosphorylation (e.g., classical DNP-type action) typically:

  1. Increases ATP yield per NADH while stopping heat production
  2. Allows protons to leak across the membrane, dissipating the gradient as heat and reducing ATP yield Correct answer.
  3. Is identical to a competitive enzyme inhibitor of hexokinase only
  4. Blocks glycolysis completely in all cells always

Explanation

Uncouplers dissipate ΔpH/Δψ; electron transport may accelerate while ATP synthesis falls and energy is lost as heat.

Question 27Metabolism

Photorespiration is problematic for C3 plants in hot conditions mainly because Rubisco:

  1. Never binds CO₂
  2. Can oxygenate RuBP, wasting carbon and energy without productive carbohydrate gain Correct answer.
  3. Is absent from C3 plants
  4. Functions only in mitochondria

Explanation

Rubisco's oxygenase activity leads to photorespiratory carbon loss, more likely when stomata close and O₂/CO₂ rises.

Question 28Neurobiology

Primary sensory cells that are neurons themselves (e.g., olfactory receptor neurons) differ from secondary sensory cells because they:

  1. Never generate receptor potentials
  2. Can generate action potentials in their own axons toward the CNS Correct answer.
  3. Are always non-excitable epithelial cells only
  4. Lack membrane receptors

Explanation

Primary receptors are sensory neurons; secondary receptors (e.g., hair cells, taste cells) are non-neuronal and synapse onto afferents.

Question 29Neurobiology

The refractory period after an action potential mainly ensures:

  1. Unlimited bidirectional spikes every microsecond
  2. Unidirectional propagation and limits firing frequency (Na⁺ channels inactivated) Correct answer.
  3. That synapses release DNA
  4. That myelin is unnecessary

Explanation

Inactivated Na⁺ channels behind the AP front prevent immediate re-excitation, enforcing directionality and max rate.

Question 30Physiology

Hormones differ from neurotransmitters mainly in that hormones:

  1. Never bind receptors
  2. Typically travel via blood (or longer-range routes) to distant targets, often with slower, longer-lasting effects Correct answer.
  3. Act only inside the synaptic cleft for milliseconds always
  4. Are exclusively DNA molecules

Explanation

Endocrine signalling is blood-borne/systemic; neurotransmission is local and fast - though both use receptor binding.

Question 31Physiology

Steroid hormones typically act by:

  1. Opening ligand-gated Na⁺ channels at the neuromuscular junction exclusively
  2. Crossing membranes and modulating gene transcription via intracellular receptors (classic genomic action) Correct answer.
  3. Being filtered only by Bowman's capsule as neurotransmitters
  4. Binding only to acetylcholine esterase

Explanation

Lipophilic steroids enter cells and alter transcription (non-genomic effects also exist, but Abitur focus is often genomic).

Question 32Physiology

Diabetes mellitus type 1 pathophysiology centers on:

  1. Excessive insulin production destroying glucose
  2. Autoimmune destruction of pancreatic β-cells leading to insulin deficiency Correct answer.
  3. Only dietary fiber deficiency with normal insulin
  4. Complete absence of glucagon receptors only

Explanation

Type 1 involves β-cell loss and insulin deficiency; type 2 is primarily insulin resistance (oversimplified but standard school distinction).

Question 33Ecology

In ecology, a biotope is best defined as:

  1. Only the DNA of one species
  2. The abiotic habitat/space of a community Correct answer.
  3. A single predator individual
  4. A type of hormone

Explanation

Biotop = Lebensraum (abiotic setting); Biozönose = community of organisms; together they form an Ökosystem.

Question 34Genetics, inheritance and molecular information

Epigenetic regulation (e.g., DNA methylation, histone modification) can:

  1. Change DNA base sequence as the only mechanism
  2. Alter gene expression without changing the nucleotide sequence, sometimes heritably through mitosis Correct answer.
  3. Replace natural selection entirely
  4. Eliminate the need for promoters

Explanation

Epigenetics modulates expression; sequence may stay intact - Abi-Boxen NDS explicitly lists Epigenetik under Vielfalt.

Question 35Evolution

Inclusive fitness / kin selection helps explain altruistic behaviour when:

  1. Actors never share genes with recipients
  2. Helping relatives can increase an actor's genetic representation via shared alleles (Hamilton's rule context) Correct answer.
  3. Natural selection never acts on behaviour
  4. Behaviour is unrelated to reproduction

Explanation

rB > C style reasoning links behaviour to fitness - Verhaltensbiologie in Vielfalt des Lebens.

Question 36Evolution

In biology, the fitness of an organism is best defined as its

  1. Relative reproductive success in passing alleles to the next generation Correct answer.
  2. Physical strength and speed
  3. Total lifespan
  4. Body size compared with others

Explanation

Evolutionary fitness measures an organism's relative reproductive success, that is, how many of its alleles are passed to the next generation. An organism that survives and reproduces more effectively has higher fitness, regardless of physical traits like strength.

Question 37Evolution

The widespread occurrence of antibiotic resistance in bacterial populations is best explained as a result of

  1. Bacteria choosing to become resistant when exposed to antibiotics
  2. Natural selection favoring pre-existing resistant variants when antibiotics are present Correct answer.
  3. Antibiotics directly mutating every bacterium to be resistant
  4. Resistance being acquired only through learning

Explanation

Random mutations produce some resistant bacteria before exposure. When antibiotics are applied, susceptible bacteria die while resistant ones survive and reproduce, so resistance increases in the population, a clear case of natural selection.

Question 38Evolution

Which type of selection favors both extreme phenotypes over the intermediate phenotype?

  1. Directional selection
  2. Disruptive selection Correct answer.
  3. Stabilizing selection
  4. Artificial selection

Explanation

Disruptive (diversifying) selection favors individuals at both extremes of a trait range while selecting against intermediates. This can increase variation and, in some cases, contribute to the formation of distinct subpopulations.

Question 39Evolution

A population meeting all Hardy-Weinberg conditions is one in which

  1. Allele frequencies remain constant because the population is not evolving Correct answer.
  2. Allele and genotype frequencies change rapidly each generation
  3. Only the dominant allele increases over time
  4. Natural selection acts strongly on every trait

Explanation

The Hardy-Weinberg principle describes a non-evolving population in which allele and genotype frequencies stay constant. The required conditions include no mutation, random mating, no gene flow, a very large population, and no natural selection.

Question 40Evolution

In a population in Hardy-Weinberg equilibrium, the frequency of the recessive allele (q) is 0.3. What is the expected frequency of homozygous recessive individuals?

  1. 0.09 Correct answer.
  2. 0.30
  3. 0.42
  4. 0.49

Explanation

Homozygous recessive frequency equals q squared. With q = 0.3, q squared = 0.09, so about 9 percent of individuals are homozygous recessive. The Hardy-Weinberg equation p^2 + 2pq + q^2 = 1 gives genotype frequencies.

Question 41Evolution

Genetic drift has the greatest effect on allele frequencies in which type of population?

  1. A very large population
  2. A population under strong directional selection
  3. A small population Correct answer.
  4. A population with high immigration

Explanation

Genetic drift is the random change in allele frequencies due to chance, and its effects are strongest in small populations where random events can dramatically alter frequencies. In large populations, drift has a much smaller relative effect.

Question 42Evolution

The bones in a human arm, a whale flipper, and a bat wing share a similar underlying structure inherited from a common ancestor. These are examples of

  1. Analogous structures
  2. Vestigial structures only
  3. Homologous structures Correct answer.
  4. Convergent structures

Explanation

Homologous structures share a common evolutionary origin and underlying anatomy even when their functions differ. The similar bone arrangement in mammalian forelimbs is strong evidence of descent from a common ancestor.

Question 43Evolution

The wings of insects and the wings of birds perform the same function but evolved independently from different ancestral structures. This is an example of

  1. Convergent evolution producing analogous structures Correct answer.
  2. Homology
  3. Genetic drift
  4. Coevolution

Explanation

Convergent evolution occurs when unrelated organisms independently evolve similar traits in response to similar environmental pressures. Insect and bird wings are analogous structures because they share function but not common ancestry.

Question 44Evolution

The formation of new species when a physical barrier divides a population, leading to reproductive isolation, is called

  1. Sympatric speciation
  2. Artificial selection
  3. Allopatric speciation Correct answer.
  4. Genetic equilibrium

Explanation

Allopatric speciation occurs when a geographic barrier separates populations, preventing gene flow. Over time, the isolated populations accumulate genetic differences and may become reproductively isolated, forming new species.

Question 45Evolution

In a phylogenetic tree, a node where a single lineage splits into two represents

  1. The extinction of a species
  2. A horizontal gene transfer event
  3. A common ancestor giving rise to two descendant lineages Correct answer.
  4. The end of all evolution in that group

Explanation

Each branch point (node) on a phylogenetic tree represents a common ancestor from which two or more descendant lineages diverged. Phylogenetic trees depict hypothesized evolutionary relationships based on shared characteristics and molecular data.

Question 46Evolution

Which line of molecular evidence most strongly supports the idea that all life shares a common ancestor?

  1. The genetic code and basic cellular machinery are nearly universal across organisms Correct answer.
  2. Every species uses a completely different genetic code
  3. Only animals use DNA as their genetic material
  4. Proteins are made from entirely different amino acids in each kingdom

Explanation

The near-universality of the genetic code, the use of DNA and RNA, and shared metabolic pathways across diverse organisms strongly support common ancestry. Such conserved features would be unlikely if life had multiple independent origins.

Question 47Evolution

The Miller-Urey experiment is significant to origin-of-life studies because it demonstrated that

  1. Complete living cells can form spontaneously in days
  2. Life on Earth definitely came from outer space
  3. Organic molecules such as amino acids can form from simpler inorganic compounds under early-Earth-like conditions Correct answer.
  4. DNA can replicate without any enzymes in any condition

Explanation

The Miller-Urey experiment showed that simulating proposed early-Earth conditions, with a mix of gases and electrical discharge, could produce amino acids and other organic molecules from inorganic precursors. It supported the idea that life's building blocks could form abiotically.

Question 48Evolution

Gene flow between two populations tends to

  1. Increase genetic differences between the populations
  2. Reduce genetic differences between the populations by mixing alleles Correct answer.
  3. Have no effect on allele frequencies
  4. Cause immediate speciation

Explanation

Gene flow is the movement of alleles between populations through migration and interbreeding. By introducing alleles from one population into another, it tends to make populations more genetically similar and can counteract divergence.

Question 49Evolution

Why is mutation considered the ultimate source of new genetic variation in a population?

  1. It rearranges existing alleles without creating anything new
  2. It only removes harmful alleles
  3. It introduces entirely new alleles into the gene pool Correct answer.
  4. It guarantees beneficial changes every time

Explanation

Mutation creates new alleles by altering the DNA sequence, providing the raw material on which other evolutionary mechanisms act. While recombination shuffles existing alleles, only mutation introduces genuinely new genetic variants.

Question 50Evolution

A small group of birds is blown to a remote island and starts a new population whose allele frequencies differ from the original population by chance. This illustrates

  1. Artificial selection
  2. Stabilizing selection
  3. Convergent evolution
  4. The founder effect Correct answer.

Explanation

The founder effect occurs when a small number of individuals establishes a new population, carrying only a subset of the original gene pool's alleles. The resulting allele frequencies can differ markedly from the source population due to chance.