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OGE Biology practice questions

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Question 1Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

Which method of biological study is used to determine the rate at which a plant stem grows over several weeks?

  1. Modeling of a theoretical ecosystem
  2. Classification of organisms into groups
  3. Observation with measurement over time Correct answer.
  4. Comparison of two unrelated species

Explanation

Studying growth requires recording a measurable change repeatedly, so the method combines observation with measurement over time. Comparison, modeling, and classification do not track a single organism's changing size.

Question 2Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

A scientist places a drop of pond water on a slide and examines it with a light microscope. This technique is best described as:

  1. experimentation
  2. modeling
  3. statistical analysis
  4. microscopy Correct answer.

Explanation

Microscopy is the method of examining objects too small to see with the naked eye using a microscope. It is a means of observation, not a controlled experiment or a model.

Question 3Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

Which feature is common to all living organisms?

  1. Presence of a cell nucleus
  2. Ability to move from place to place
  3. Ability to photosynthesize
  4. Capacity for metabolism and self-reproduction Correct answer.

Explanation

Metabolism and the capacity to reproduce are universal properties of living things. Movement, a nucleus, and photosynthesis are each absent in many organisms.

Question 4Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

The smallest level of organization of life that can carry out all vital processes independently is the:

  1. organ
  2. tissue
  3. population
  4. cell Correct answer.

Explanation

The cell is the basic structural and functional unit of life; a single cell can perform all processes needed to stay alive. Organs and tissues are parts of multicellular bodies, and a population is a group of organisms.

Question 5Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

Which level of organization is represented by a herd of deer living in a forest together with the trees, grasses, and soil of that forest?

  1. Biosphere
  2. Biogeocenosis Correct answer.
  3. Organism
  4. Population

Explanation

A biogeocenosis is a community of interacting organisms together with their abiotic environment in a defined area. The herd alone would be a population, but the whole living-and-nonliving system is the biogeocenosis.

Question 6Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

A researcher wants to test whether light intensity affects the rate of photosynthesis in pondweed. Which design is the most appropriate?

  1. Observe the pondweed under a microscope for an hour
  2. Measure oxygen release once at a single natural light level
  3. Compare oxygen release in two different plant species
  4. Measure oxygen release at several light intensities while keeping temperature and carbon dioxide constant Correct answer.

Explanation

A valid experiment changes one variable, light intensity, while holding other factors constant, and measures the effect. Varying several factors or using different species would not isolate the influence of light.

Question 7Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

Which pair of processes provides evidence that an organism maintains a relatively stable internal environment?

  1. Regulation of body temperature and blood glucose Correct answer.
  2. Growth and development
  3. Irritability and reflex action
  4. Reproduction and heredity

Explanation

Homeostasis is the maintenance of stable internal conditions such as temperature and blood glucose concentration. Growth, irritability, and reproduction are distinct properties of life.

Question 8Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

In an experiment on enzyme activity, a student finds that the reaction rate rises as temperature increases up to 37 °C and then falls sharply. Which conclusion is best supported?

  1. Enzyme activity has an optimum temperature near 37 °C Correct answer.
  2. Enzymes are destroyed by low temperatures only
  3. Temperature has no effect on enzyme activity
  4. Enzymes work fastest at any temperature above 37 °C

Explanation

The peak rate at about 37 °C followed by a decline indicates an optimum temperature for the enzyme. Above the optimum the enzyme's structure is disrupted, reducing activity.

Question 9Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

Which statement correctly describes the relationship between the cellular and organism levels of organization?

  1. Cells are formed by the breakdown of organs
  2. Cells and organisms are unrelated levels of organization
  3. An organism is made of cells whose coordinated activity sustains the whole Correct answer.
  4. The organism level exists only in unicellular forms

Explanation

In multicellular organisms, cells are organized into tissues, organs, and systems whose coordinated activity maintains the organism. The organism level therefore depends on the cellular level.

Question 10Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

A biologist tags individual birds and records how many return to the same nesting site each year. Which method is being used?

  1. Field observation and marking Correct answer.
  2. Laboratory experimentation
  3. Genetic sequencing
  4. Modeling of population growth

Explanation

Marking animals and recording their recapture or return is a field observation method used to study behavior and population dynamics. It does not involve a controlled laboratory setup or a theoretical model.

Question 11Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

Which property of living things is illustrated by a plant bending toward a window?

  1. Metabolism
  2. Reproduction
  3. Heredity
  4. Irritability Correct answer.

Explanation

Irritability is the ability of organisms to respond to stimuli such as light, which explains the bending of the shoot toward the window. Heredity, metabolism, and reproduction concern other vital processes.

Question 12Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

Which sequence correctly orders levels of organization from simpler to more complex?

  1. Tissue → cell → organ → population → organism
  2. Population → organism → organ → tissue → cell
  3. Cell → tissue → organ → organism → population Correct answer.
  4. Organ → cell → tissue → organism → population

Explanation

Life is organized from cells into tissues, organs, organisms, and then populations of organisms. Each level is built from the one before it.

Question 13Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

Two groups of seedlings are grown under identical conditions except that one group receives a nutrient solution and the other receives pure water. After three weeks the stem lengths are compared. Which variable is the independent variable?

  1. Duration of growth
  2. Temperature of the room
  3. Presence of the nutrient solution Correct answer.
  4. Stem length

Explanation

The independent variable is the factor deliberately changed by the researcher, here the presence or absence of the nutrient solution. Stem length is the dependent variable measured as the outcome.

Question 14Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

A student claims that a virus is a living organism because it contains genetic material and can multiply. Which argument best refutes this claim?

  1. Viruses contain nucleic acids, which living things lack
  2. Viruses can cause disease in plants and animals
  3. Viruses multiply only inside a host cell and have no independent metabolism Correct answer.
  4. Viruses are too small to be seen with a light microscope

Explanation

A key criterion of life is independent metabolism and self-reproduction; viruses lack their own metabolism and can reproduce only by using a host cell's machinery. Size and disease-causing ability are not criteria of life.

Question 15Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

In a study, researchers measured the number of mayfly larvae at several points along a river with different oxygen concentrations. They found more larvae where oxygen was higher. Which statement is the most valid interpretation?

  1. Oxygen concentration is caused by the number of larvae
  2. Mayfly larvae produce the oxygen they need
  3. Larval abundance is unrelated to oxygen concentration
  4. High oxygen concentration is associated with greater larval abundance Correct answer.

Explanation

Observational data can show an association between oxygen level and larval numbers, but correlation alone does not prove causation. The data support a relationship, not a claim that larvae generate oxygen.

Question 16Biology as a science; methods of biological study; signs of living organisms; levels of organization of life

Which of the following is an example of the biosphere level of organization?

  1. A single oak tree and the insects feeding on it
  2. All the bacteria living in a single drop of pond water
  3. The living organisms of Earth together with the environments they inhabit Correct answer.
  4. The cells making up the leaf of a plant

Explanation

The biosphere is the highest level of organization, comprising all living organisms on Earth and the environments they interact with. The other options describe smaller, local levels.

Question 17Cellular structure and chemical composition of cells; cell division

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

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

Explanation

Mitochondria carry out aerobic respiration, transferring energy from organic molecules to ATP via the electron transport chain. Ribosomes build proteins, the Golgi modifies and packages them, and lysosomes carry out intracellular digestion.

Question 18Cellular structure and chemical composition of cells; cell division

Which molecule stores the genetic information that is transcribed into messenger RNA in a eukaryotic cell?

  1. Protein
  2. Lipid
  3. Polysaccharide
  4. DNA Correct answer.

Explanation

DNA holds the base sequence that is copied into mRNA during transcription. Proteins, lipids and polysaccharides do not carry the coded hereditary information.

Question 19Cellular structure and chemical composition of cells; cell division

A cell is placed in a solution whose solute concentration is higher than that of the cytoplasm. What is the expected immediate effect on an animal cell?

  1. It loses water and shrinks Correct answer.
  2. It stays exactly the same size
  3. It builds a rigid cell wall
  4. It swells and may burst

Explanation

In a hypertonic solution the external water potential is lower, so water leaves the cell by osmosis. An animal cell without a wall therefore shrinks. Swelling occurs in a hypotonic solution, and animal cells never build walls.

Question 20Cellular structure and chemical composition of cells; cell division

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

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

Explanation

In anaphase the spindle fibres shorten and pull the separated chromatids, now individual chromosomes, to opposite poles. Prophase involves chromosome condensation, metaphase their alignment at the equator, and telophase nuclear reformation.

Question 21Cellular structure and chemical composition of cells; cell division

Which statement correctly describes the outcome of meiosis in a diploid organism?

  1. Two diploid cells identical to the parent
  2. Two haploid cells with doubled chromosome number
  3. Four diploid cells with no genetic variation
  4. Four haploid cells with new allele combinations Correct answer.

Explanation

Meiosis halves the chromosome number and, through crossing over and independent assortment, produces four genetically varied haploid cells. Identical diploid daughter cells are the product of mitosis.

Question 22Cellular structure and chemical composition of cells; cell division

Which chemical bond joins two amino acids together in a polypeptide chain?

  1. Glycosidic bond
  2. Ionic bond
  3. Peptide bond Correct answer.
  4. Hydrogen bond

Explanation

A condensation reaction between the carboxyl group of one amino acid and the amino group of the next forms a peptide bond with the loss of water. Hydrogen bonds stabilise secondary structure, and glycosidic bonds link sugars.

Question 23Cellular structure and chemical composition of cells; cell division

Which property of the phospholipid bilayer allows small non-polar molecules such as oxygen to cross a membrane readily?

  1. Its hydrophobic interior Correct answer.
  2. Its net positive charge
  3. Its rigid cellulose framework
  4. Its high protein content

Explanation

The fatty acid tails create a hydrophobic core through which small non-polar molecules dissolve and diffuse easily. Polar and charged substances need channels or carriers. Membranes contain no cellulose and carry no overall positive charge.

Question 24Cellular structure and chemical composition of cells; cell division

Which enzyme unwinds the DNA double helix and breaks the hydrogen bonds between complementary strands before replication?

  1. Helicase Correct answer.
  2. Amylase
  3. Ligase
  4. DNA polymerase

Explanation

Helicase separates the two strands by disrupting the hydrogen bonds between base pairs, creating the replication fork. DNA polymerase then adds nucleotides, and ligase joins fragments. Amylase digests starch.

Question 25Cellular structure and chemical composition of cells; cell division

A student views a cell and observes a rigid outer layer, a large central vacuole, and green chloroplasts. Which cell type is this most likely to be?

  1. A plant leaf cell Correct answer.
  2. A bacterial cell
  3. A human red blood cell
  4. A nerve cell

Explanation

A rigid wall, a large central vacuole and chloroplasts are characteristic features of plant cells. Animal cells lack walls and chloroplasts, and bacteria have no chloroplasts or large vacuoles.

Question 26Cellular structure and chemical composition of cells; cell division

In a cross, the number of chromosomes in a gamete is 12. What is the diploid chromosome number of the organism?

  1. 48
  2. 24 Correct answer.
  3. 6
  4. 12

Explanation

Gametes are haploid, carrying half the diploid number, so the diploid number is twice the gamete count, 12 × 2 = 24. Halving to 6 would be a further reduction, and 12 is the haploid value itself.

Question 27Cellular structure and chemical composition of cells; cell division

Which stage of the cell cycle is the period during which DNA is replicated?

  1. G2 phase
  2. G1 phase
  3. M phase
  4. S phase Correct answer.

Explanation

DNA synthesis occurs in S phase, between the two gap phases. G1 involves growth and preparation, G2 further growth and checking, and M phase is mitosis and cytokinesis.

Question 28Cellular structure and chemical composition of cells; cell division

Which feature distinguishes prokaryotic cells from eukaryotic cells?

  1. Absence of a membrane-bound nucleus Correct answer.
  2. Presence of ribosomes
  3. Presence of cytoplasm
  4. Presence of a cell membrane

Explanation

Prokaryotes lack a nuclear envelope, so their DNA lies free in the cytoplasm as a nucleoid. Ribosomes, a cell membrane and cytoplasm are found in both cell types.

Question 29Cellular structure and chemical composition of cells; cell division

Which substance is the main structural component of plant cell walls?

  1. Cellulose Correct answer.
  2. Phospholipid
  3. Glycogen
  4. Chitin

Explanation

Plant cell walls are made mainly of cellulose microfibrils that give strength and support. Chitin forms fungal walls and arthropod exoskeletons, glycogen is an animal storage carbohydrate, and phospholipids form membranes.

Question 30Cellular structure and chemical composition of cells; cell division

A mutation changes a single DNA base so that one codon becomes a stop codon. What is the most likely consequence for the protein produced?

  1. The protein sequence is unchanged
  2. The protein is converted into a lipid
  3. The protein gains an extra amino acid at the end
  4. The protein is shortened and may lose function Correct answer.

Explanation

A premature stop codon ends translation early, so the polypeptide is truncated and often non-functional. The sequence is changed, no extra residue is added, and proteins are not converted into lipids by mutation.

Question 31Cellular structure and chemical composition of cells; cell division

Which process requires energy from ATP and moves substances against their concentration gradient?

  1. Simple diffusion
  2. Osmosis
  3. Facilitated diffusion
  4. Active transport Correct answer.

Explanation

Active transport uses carrier proteins and ATP to move substances from low to high concentration. Diffusion, osmosis and facilitated diffusion are passive and follow the concentration gradient.

Question 32Cellular structure and chemical composition of cells; cell division

Which statement best explains why the genetic information in all cells of one organism is the same but their structures differ?

  1. Cells lose genes as they specialise
  2. Different cells contain different genes
  3. Different genes are expressed in different cells Correct answer.
  4. Each cell type has a different genetic code

Explanation

Cell differentiation results from selective gene expression: cells keep the same genome but switch on different genes. Genes are not lost during specialisation, and the genetic code is universal.

Question 33Cellular structure and chemical composition of cells; cell division

Which organelle is responsible for modifying, sorting and packaging proteins for secretion?

  1. Golgi apparatus Correct answer.
  2. Nucleolus
  3. Ribosome
  4. Vacuole

Explanation

The Golgi apparatus receives proteins from the endoplasmic reticulum, modifies them and packages them into vesicles for secretion or delivery. Ribosomes synthesise proteins, and the nucleolus makes ribosomal RNA.

Question 34Cellular structure and chemical composition of cells; cell division

A cell in which 2n = 8 undergoes meiosis. How many chromosomes are present in each daughter cell at the end of the second meiotic division?

  1. 16
  2. 8
  3. 2
  4. 4 Correct answer.

Explanation

Meiosis halves the diploid number, so each haploid product contains 8 ÷ 2 = 4 chromosomes. The second division separates chromatids but does not change the chromosome number further.

Question 35Cellular structure and chemical composition of cells; cell division

Which part of a nucleotide differs between the four types of DNA nucleotide?

  1. The phosphate group
  2. The deoxyribose sugar
  3. The nitrogenous base Correct answer.
  4. The hydrogen bonds

Explanation

DNA nucleotides share the same phosphate and deoxyribose but differ in their nitrogenous base: adenine, thymine, cytosine or guanine. Hydrogen bonds are interactions between bases, not a component of the nucleotide.

Question 36Cellular structure and chemical composition of cells; cell division

Which statement correctly compares the two products of mitosis in a somatic cell?

  1. They are genetically identical to each other and to the parent cell Correct answer.
  2. They are haploid and genetically varied
  3. They contain half the parent's chromosome number
  4. They differ from the parent cell by crossing over

Explanation

Mitosis produces two daughter cells with the same chromosome number and alleles as the parent, supporting growth and repair. Halving of chromosome number and genetic variation arise in meiosis.

Question 37Organisms: bacteria, fungi, plants - structure, life activity, classification

Which structure enables a bacterium to move through a liquid environment?

  1. Cell wall
  2. Flagellum Correct answer.
  3. Ribosome
  4. Capsule

Explanation

The flagellum is a long thread-like appendage that rotates to propel the cell, so it is the organelle of locomotion in bacteria. The other listed structures serve protection, shape, or protein synthesis, not movement.

Question 38Organisms: bacteria, fungi, plants - structure, life activity, classification

What is the main function of the hyphae in a multicellular fungus?

  1. Carrying out photosynthesis
  2. Producing pollen grains
  3. Absorbing nutrients from the substrate Correct answer.
  4. Conducting water to the leaves

Explanation

Fungal hyphae form a branching mycelium with a large surface area that absorbs dissolved organic matter. Fungi are heterotrophs and lack the tissues for photosynthesis or water conduction found in plants.

Question 39Organisms: bacteria, fungi, plants - structure, life activity, classification

Which group of plants reproduces by means of spores and has no true roots, stems or leaves?

  1. Algae Correct answer.
  2. Conifers
  3. Ferns
  4. Flowering plants

Explanation

Algae are the most simply organised plants: their body is a thallus without differentiated roots, stems or leaves, and they reproduce by spores. Ferns already possess true organs, while conifers and flowering plants are seed plants.

Question 40Organisms: bacteria, fungi, plants - structure, life activity, classification

By what process do most bacteria reproduce under favourable conditions?

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

Explanation

Bacteria are prokaryotes and divide by binary fission, in which the circular DNA is copied and the cell splits in two. Mitosis and meiosis are eukaryotic processes, and budding is characteristic of yeasts.

Question 41Organisms: bacteria, fungi, plants - structure, life activity, classification

What is the role of the cap (pileus) of a mushroom?

  1. It protects the fungus from sunlight
  2. It absorbs water from the substratum
  3. It bears the spore-producing structures Correct answer.
  4. It anchors the fungus in the soil

Explanation

The cap carries the gills or pores on which spores are formed, so it is the reproductive part of the fruiting body. Anchoring and absorption are functions of the mycelium in the substrate.

Question 42Organisms: bacteria, fungi, plants - structure, life activity, classification

Which feature distinguishes prokaryotic bacterial cells from the cells of plants and fungi?

  1. Presence of a cell wall
  2. Presence of a plasma membrane
  3. Absence of a membrane-bound nucleus Correct answer.
  4. Presence of ribosomes

Explanation

Bacteria store their genetic material in a nucleoid without a nuclear membrane, which is the defining prokaryotic feature. Cell walls, ribosomes and plasma membranes occur in plants and fungi as well, so they do not distinguish the groups.

Question 43Organisms: bacteria, fungi, plants - structure, life activity, classification

Which plants are classified as spore-bearing vascular plants with true conducting tissues?

  1. Green algae
  2. Mosses
  3. Horsetails Correct answer.
  4. Grasses

Explanation

Horsetails are vascular cryptogams: they have true roots, stems and leaves with conducting tissues and reproduce by spores. Mosses lack true vascular tissue, algae have no organs, and grasses are seed plants.

Question 44Organisms: bacteria, fungi, plants - structure, life activity, classification

Which substance forms the main component of a fungal cell wall?

  1. Lignin
  2. Chitin Correct answer.
  3. Cellulose
  4. Peptidoglycan

Explanation

Fungal walls are built mainly of chitin, a nitrogen-containing polysaccharide. Cellulose is typical of plants, peptidoglycan of bacteria, and lignin is a strengthening material of plant secondary walls.

Question 45Organisms: bacteria, fungi, plants - structure, life activity, classification

A student finds a green filamentous organism in a pond. Under the microscope the filaments contain chloroplasts and each cell has a nucleus. To which group does it most likely belong?

  1. Green algae Correct answer.
  2. Moss
  3. Yeast
  4. Cyanobacteria

Explanation

Green algae are eukaryotic photosynthetic organisms that may form filaments and contain chloroplasts. Cyanobacteria are prokaryotes without a nucleus, yeast is a non-photosynthetic fungus, and mosses are terrestrial leafy plants.

Question 46Organisms: bacteria, fungi, plants - structure, life activity, classification

Why are bacteria able to survive in a wide range of environments, including very harsh ones?

  1. They possess a true nucleus that repairs damage
  2. They can form resistant spores and enter dormancy Correct answer.
  3. They photosynthesise in complete darkness
  4. They exchange genetic material only by meiosis

Explanation

Many bacteria form endospores, highly resistant dormant structures that survive heat, drying and radiation. Bacteria have no nucleus and do not photosynthesise without light; meiosis does not occur in prokaryotes.

Question 47Organisms: bacteria, fungi, plants - structure, life activity, classification

What is the function of the root hairs on a plant root?

  1. Increasing the surface area for water and mineral uptake Correct answer.
  2. Producing new leaves
  3. Conducting sugars to the shoot
  4. Storing starch for the winter

Explanation

Root hairs are thin outgrowths of epidermal cells that greatly enlarge the absorbing surface of the root. Storage, leaf formation and sugar transport are performed by other tissues.

Question 48Organisms: bacteria, fungi, plants - structure, life activity, classification

Which process in yeast is used by humans in baking and brewing?

  1. Aerobic photosynthesis producing oxygen
  2. Binary fission producing spores
  3. Nitrogen fixation in root nodules
  4. Anaerobic fermentation of sugars producing ethanol and carbon dioxide Correct answer.

Explanation

Yeasts ferment sugars anaerobically, releasing ethanol and carbon dioxide; the gas raises dough and the ethanol is the basis of brewing. Yeasts do not photosynthesise, fix nitrogen or reproduce by binary fission.

Question 49Organisms: bacteria, fungi, plants - structure, life activity, classification

Which structure in a flowering plant carries out the transport of water and dissolved minerals from the roots upward?

  1. Cambium
  2. Xylem Correct answer.
  3. Epidermis
  4. Phloem

Explanation

Xylem vessels and tracheids conduct water and minerals upward from the root. Phloem transports sugars, cambium produces new vascular tissue, and epidermis is a protective covering.

Question 50Organisms: bacteria, fungi, plants - structure, life activity, classification

Which characteristic places the mosses among the most primitive land plants?

  1. They have flowers but no fruit
  2. They reproduce by seeds
  3. They lack true roots and true vascular tissue Correct answer.
  4. They have a well-developed root system

Explanation

Mosses have rhizoids instead of true roots and lack specialised conducting tissues, which limits their size and ties them to moist habitats. They reproduce by spores and have neither seeds nor flowers.