8 Units · 128 Quiz Questions · 72 Flashcards · Diagnostic · Full Reference Tables · Diagrams · Saved Progress
Based on this guide's real question bank — 128 practice questions across 8 units. Slide to match your situation.
Levels of biological organization, from smallest/simplest to largest/most complex.
The four major organic macromolecules and their monomer building blocks.
Comparison of prokaryotic and eukaryotic cell structure.
Photosynthesis and cellular respiration are complementary, opposite processes.
A monohybrid Punnett square cross (Bb × Bb) showing the 3:1 phenotype ratio.
Natural selection: variation, competition, and differential survival lead to a shift in a population's traits over generations.
An energy pyramid: only about 10% of energy passes to each successive trophic level.
Homeostasis via negative feedback: a change is detected and reversed to restore the normal set point.
Which characteristic must an object show to be considered a living thing?
Living things are made of cells and carry out metabolism, along with growth, reproduction, homeostasis, and response to stimuli. Motion and water content alone don't define life.
A virus is generally NOT considered fully alive because it
Viruses lack the machinery for independent metabolism and reproduction, requiring a host cell to replicate.
Which correctly orders the levels of biological organization from smallest to largest?
The correct order is cell → tissue → organ → organ system → organism.
In an experiment testing whether fertilizer affects plant growth, the amount of fertilizer added is the
The independent variable is the factor the experimenter deliberately changes — here, the amount of fertilizer.
In the same fertilizer experiment, plant height after 4 weeks is the
The dependent (responding) variable is what is measured — plant height, which may change due to fertilizer amount.
Why is a control group included in an experiment?
A control group receives no treatment and serves as the baseline against which the experimental group's results are compared.
A good hypothesis must be
A hypothesis is a proposed explanation that can be tested and potentially shown to be false through experimentation.
A scientific theory is best described as
Unlike the everyday use of 'theory,' a scientific theory is a well-substantiated explanation backed by extensive evidence.
Which is an example of a population?
A population consists of members of the SAME species living in the same area — all the trout in the lake.
Which best distinguishes a community from an ecosystem?
An ecosystem = a community of populations PLUS the abiotic environment they interact with.
Which is a quantitative observation?
Quantitative data are numerical measurements, like a specific temperature reading.
A student wants to test if light color affects plant growth. Which variable should be kept constant across all groups?
To isolate the effect of light color, all other factors (water amount, plant type) must be held constant.
Which organelle-related structure is visible only with a compound light microscope on HIGH power after first focusing on LOW power?
Switching from low to high power increases magnification, revealing finer detail, but narrows the field of view.
If the ocular lens is 10x and the objective lens in use is 40x, the total magnification is
Total magnification = ocular × objective = 10 × 40 = 400x.
Which best describes reproduction as a characteristic of life?
Reproduction can occur asexually (one parent, identical offspring) or sexually (two parents, genetic variation).
A plant bending toward a window to get more sunlight demonstrates the characteristic of life known as
Responding to an environmental stimulus (light) by growing toward it is a response to stimuli.
Which four elements make up about 96% of living tissue by mass?
Carbon, hydrogen, oxygen, and nitrogen are the 'big four' elements that dominate organic molecules.
Water is described as a polar molecule because
Water's uneven electron distribution creates a partial negative charge near O and partial positive charges near the H atoms.
Water molecules sticking to each other via hydrogen bonds, producing surface tension, is called
Cohesion is water sticking to itself; this is responsible for surface tension.
Capillary action, which helps water rise through plant stems, relies mainly on
Adhesion (water to the polar stem walls) combined with cohesion (water to water) pulls water upward against gravity.
Which macromolecule class is made of amino acid monomers?
Proteins are polymers built from amino acid monomers, folded into specific shapes.
Which best describes an enzyme's role?
Enzymes speed up specific reactions by lowering activation energy and are reused, not consumed.
An enzyme exposed to extreme heat may become denatured, meaning
High heat (or extreme pH) can unfold an enzyme's specific shape, which destroys its ability to bind its substrate.
Which reaction joins monomers into a polymer by removing a water molecule at each bond?
Dehydration (condensation) synthesis builds polymers from monomers, releasing water at each new bond formed.
Digestion of food, which breaks polymers into monomers using water, is an example of
Hydrolysis adds water to break the bonds in a polymer, releasing individual monomers — this is how digestion works.
Lipids are best described as
Lipids are hydrophobic (nonpolar), storing energy long-term and forming the cell membrane's phospholipid bilayer.
A disaccharide such as sucrose is formed from
Sucrose is a disaccharide made of two joined monosaccharides (glucose + fructose).
Which statement about nucleic acids is correct?
Nucleic acids (DNA, RNA) are polymers of nucleotides and carry an organism's genetic information.
A saturated fat, compared to an unsaturated fat, typically
Saturated fats lack double bonds between carbons and are generally solid at room temperature (e.g., butter).
Why is water often called the 'universal solvent' in biology?
Water's polarity lets it dissolve a wide range of substances, which is critical for transporting nutrients and enabling reactions in organisms.
A nucleotide is made of which three components?
Each nucleotide consists of a sugar, a phosphate group, and one nitrogenous base.
Which best explains why enzymes are considered reusable?
Enzymes speed up reactions without being permanently altered, so the same enzyme molecule can catalyze many reactions repeatedly.
According to the cell theory, all cells arise from
The cell theory states that all cells come from pre-existing cells through cell division.
Which structure is present in prokaryotic cells but has NO membrane enclosing it?
Prokaryotes lack a membrane-bound nucleus; their circular DNA is free in the cytoplasm.
Which organelle is the site of cellular respiration and is often called the 'powerhouse of the cell'?
The mitochondrion converts glucose energy into usable ATP through cellular respiration.
Which organelle packages and ships proteins to their destinations in vesicles?
The Golgi apparatus modifies, packages, and ships materials, often in vesicles, to their final destination.
Which structure is found in plant cells but NOT in animal cells?
Plant cells uniquely have a rigid cellulose cell wall and chloroplasts for photosynthesis; animal cells lack both.
The movement of particles from an area of high concentration to low concentration, requiring no energy, is called
Diffusion is passive movement down the concentration gradient (high to low), requiring no ATP.
A red blood cell placed in a hypotonic solution will most likely
In a hypotonic solution, water concentration is higher outside relative to solutes, so water moves INTO the cell, potentially causing it to swell/burst.
Moving a substance from an area of LOW concentration to HIGH concentration requires
Moving substances against their concentration gradient is active transport, which requires ATP.
Which sequence correctly orders the phases of mitosis?
Mitosis proceeds: prophase → metaphase → anaphase → telophase.
During which phase of mitosis do sister chromatids separate and move to opposite poles?
In anaphase, sister chromatids are pulled apart toward opposite poles of the cell.
The two daughter cells produced by mitosis are
Mitosis produces two genetically identical diploid daughter cells, used for growth and repair.
Which best describes the cell membrane's structure?
The cell membrane is a phospholipid bilayer, with water-loving heads facing the watery environments and water-fearing tails facing each other in the middle.
Which cell part is present in ALL cells, both prokaryotic and eukaryotic?
Every cell, prokaryotic or eukaryotic, has a cell membrane, cytoplasm, and ribosomes.
Lysosomes function mainly to
Lysosomes contain digestive enzymes used to break down cellular waste, debris, and damaged organelles.
Which phase of the cell cycle involves DNA replication before mitosis begins?
Interphase is when the cell grows, carries out its normal functions, and replicates its DNA before dividing.
A cell placed in an isotonic solution will
In an isotonic solution, solute concentrations inside and outside are equal, so there is no net movement of water.
ATP releases usable energy when
Breaking the bond to ATP's outer phosphate releases energy and produces ADP + phosphate.
An organism that makes its own food from inorganic sources is called a(n)
Autotrophs, like plants and algae, produce their own food (commonly via photosynthesis).
Which correctly represents the overall equation for photosynthesis?
Photosynthesis converts carbon dioxide and water into glucose and oxygen using light energy.
In a leaf cell, photosynthesis takes place in the
Chloroplasts contain chlorophyll and are the site of photosynthesis.
Chlorophyll appears green because it
Chlorophyll absorbs red and blue light for photosynthesis and reflects green light, which is why plants appear green.
Which correctly represents the overall equation for cellular respiration?
Cellular respiration breaks down glucose and oxygen into carbon dioxide, water, and usable ATP energy.
Which organelle is the primary site of aerobic cellular respiration?
Mitochondria are the main site where aerobic respiration converts glucose energy into ATP.
Fermentation (anaerobic respiration) differs from aerobic respiration in that fermentation
Fermentation occurs without oxygen and yields far less ATP than aerobic respiration.
Lactic acid buildup in muscles during intense exercise is a result of
When oxygen is limited during intense exercise, muscle cells rely on lactic acid fermentation for quick energy.
Which statement correctly relates photosynthesis and cellular respiration?
Photosynthesis's products (glucose, O₂) are respiration's reactants, and vice versa — the two are complementary cycles.
Yeast producing carbon dioxide and alcohol without oxygen is an example of
Yeast carries out alcoholic fermentation in the absence of oxygen, producing CO₂ and ethanol.
Which of the following is a heterotroph?
Fungi are heterotrophs — they cannot photosynthesize and must obtain organic molecules from their environment.
The light-dependent reactions of photosynthesis take place in the
Light-dependent reactions occur in the thylakoid membranes, producing ATP and O₂ using light energy and water.
The Calvin cycle (light-independent reactions) of photosynthesis takes place in the
The Calvin cycle occurs in the stroma, using ATP and CO₂ to build glucose.
Which gas is released as a waste product of the light-dependent reactions of photosynthesis?
Water is split during the light-dependent reactions, releasing oxygen as a byproduct.
Both autotrophs and heterotrophs carry out
All organisms, whether they make their own food or consume it, perform cellular respiration to release usable energy from glucose.
In DNA, adenine always pairs with which base?
Complementary base pairing: A pairs with T (and G pairs with C) via hydrogen bonds.
A specific segment of DNA that codes for a particular protein/trait is called a
A gene is a defined segment of DNA coding for a specific trait/protein.
How many chromosomes are found in a typical human body (somatic) cell?
Human body cells are diploid with 46 chromosomes (23 pairs), one set inherited from each parent.
An organism with the genotype Bb for a trait is described as
Bb has two DIFFERENT alleles, making it heterozygous ('hybrid').
In simple dominance, if B is dominant (brown) and b is recessive (blue), which genotype(s) would show the brown phenotype?
Both homozygous dominant (BB) and heterozygous (Bb) genotypes express the dominant brown phenotype.
A cross between two heterozygous parents (Bb × Bb) is expected to produce offspring in what approximate phenotype ratio?
A monohybrid Bb × Bb cross typically yields a 1 BB : 2 Bb : 1 bb genotype ratio, giving a 3:1 dominant:recessive phenotype ratio.
A testcross is used to determine
Crossing an organism of unknown genotype (but dominant phenotype) with a homozygous recessive organism reveals whether it is BB or Bb based on offspring ratios.
Meiosis differs from mitosis in that meiosis
Meiosis produces four haploid gametes that are genetically different from each other and the parent cell, unlike mitosis's two identical diploid cells.
Crossing-over during meiosis increases genetic variation by
Crossing-over shuffles alleles between homologous chromosome pairs, increasing genetic diversity among gametes.
A haploid gamete has how many sets of chromosomes compared to a diploid body cell?
Haploid (n) cells have half the chromosome number of diploid (2n) cells; fertilization (n + n) restores the diploid number.
RNA differs from DNA in that RNA
RNA is single-stranded, uses ribose sugar, and substitutes uracil (U) for thymine (T).
Homologous chromosomes are best described as
Homologous chromosomes are a matched pair (one maternal, one paternal) carrying genes for the same traits at the same locations, though the specific alleles may differ.
If both parents are heterozygous (Aa) for a recessive genetic condition, what is the probability their child will show the recessive phenotype?
An Aa × Aa cross gives a 1:2:1 genotype ratio (AA:Aa:aa), so 25% (aa) show the recessive phenotype.
The physical, observable expression of a genetic trait is called the
Phenotype is the observable/physical trait (e.g., eye color), while genotype is the underlying allele combination.
Fertilization restores the diploid chromosome number by
A haploid sperm (n) fertilizing a haploid egg (n) produces a diploid zygote (2n).
Which structure is a tightly coiled/condensed form of DNA wrapped around proteins?
A chromosome is DNA condensed and organized around proteins so it can be reliably copied and separated during cell division.
Which best summarizes Darwin's theory of natural selection?
Natural selection favors individuals whose inherited traits improve survival and reproduction in a given environment; those traits become more common over generations.
Which condition is NOT required for natural selection to occur?
Natural selection depends on VARIATION among individuals — if all individuals were identical, there would be nothing to select between.
The human arm, whale flipper, and bat wing share a similar bone structure despite different functions. These are examples of
Homologous structures share an underlying structure inherited from a common ancestor, even though their functions differ.
A butterfly wing and a bird wing serve a similar function (flight) but evolved independently with different structures. These are
Analogous structures perform similar functions but arose independently (convergent evolution), not from a shared ancestor.
The human appendix, which has little function today but likely aided digestion in ancestors, is an example of a
Vestigial structures are reduced remnants of structures that had a function in an ancestral species.
Which type of evidence directly shows a gradual change in life forms across successive rock layers over time?
Fossils found in ordered rock layers provide a direct historical record of gradual changes in organisms over time.
Two species with highly similar DNA sequences are inferred to
Greater DNA similarity indicates a more recent common ancestor and closer evolutionary relationship.
Biological 'fitness' is best defined as
Fitness refers to reproductive success in a given environment, not physical strength alone.
Geographic isolation can lead to speciation because
When a physical barrier prevents interbreeding, isolated populations evolve independently and may become reproductively isolated, forming new species.
Two populations are considered separate species when they
The key biological definition of separate species is reproductive isolation — inability to interbreed and produce fertile offspring.
Darwin's finches on the Galápagos Islands developed different beak shapes primarily due to
Isolated on different islands with different available food, finch populations were selected for different beak shapes suited to local resources.
An adaptation that helps an organism survive in a desert environment might NOT be helpful
Adaptations are suited to specific environments; a trait beneficial in a desert may be neutral or harmful in a rainforest.
Which statement about evolution and individual organisms is correct?
Evolution describes change at the population level over generations — an individual's genes do not change because of its own life experiences.
Comparative embryology as evidence for evolution refers to
Related organisms often show strikingly similar stages of embryonic development, suggesting shared ancestry.
Antibiotic resistance becoming more common in a bacterial population after repeated antibiotic exposure is an example of
Bacteria with resistance survive antibiotic exposure and reproduce, making resistance more common in the population — a direct example of natural selection.
Which best explains why variation within a population is essential for evolution by natural selection?
Natural selection requires that individuals differ in traits so that some variants are more favored by the environment than others.
Sunlight, temperature, and soil pH are all examples of
Abiotic factors are non-living components of the environment, such as sunlight, temperature, and soil chemistry.
An organism's specific functional role in its ecosystem, including what it eats and how it interacts with others, is its
Niche describes an organism's role/job in the ecosystem; habitat is simply where it physically lives.
In a food chain, producers are always
Producers (autotrophs, like plants) make their own food and form the foundational base of every food chain.
An organism that eats both plants and animals is called a(n)
Omnivores consume both producers (plants) and other consumers (animals).
Fungi and bacteria that break down dead organisms and recycle nutrients are classified as
Decomposers break down dead organic matter and waste, returning nutrients to the ecosystem for producers to reuse.
A food web differs from a food chain in that a food web
A food web captures the complexity of real ecosystems, where most organisms have multiple feeding relationships, unlike a single linear food chain.
According to the 10% rule, approximately what percentage of energy is transferred from one trophic level to the next?
Only about 10% of energy at one trophic level is available to the next level up; roughly 90% is lost, mostly as heat.
Why do energy pyramids typically support only 4–5 trophic levels?
With ~90% of energy lost at each level, there is eventually too little energy remaining to sustainably support further trophic levels.
The maximum population size an ecosystem's resources can sustainably support is called the
Carrying capacity is the population size an environment can sustain long-term given its available resources.
If a deer population grows well beyond its ecosystem's carrying capacity, which is the most likely outcome?
Exceeding carrying capacity leads to resource scarcity, causing limiting factors (starvation, disease, competition) to reduce the population back down.
Which is an example of a limiting factor for a population?
Food, water, disease, predators, and space are all limiting factors that can restrict population growth.
Introducing a non-native, invasive species into an ecosystem often
Invasive species often outcompete native organisms that have no evolved defenses against them, disrupting the ecosystem.
Bioaccumulation of a toxic pollutant as it moves up a food chain is a concern primarily caused by
Pollutants can accumulate in tissues and become increasingly concentrated (biomagnified) as they move up the food chain to top predators.
Deforestation primarily threatens biodiversity by
Removing forest habitat displaces and endangers species that depend on that ecosystem, reducing biodiversity.
Which best describes the relationship between a community and its abiotic environment that together form an ecosystem?
An ecosystem combines the biological community with the physical (abiotic) environment they interact with.
Which of the following represents a correct simplified food chain?
Energy flows from producer (grass) to primary consumer (rabbit) to secondary consumer (fox).
Homeostasis refers to an organism's ability to
Homeostasis is the maintenance of stable internal conditions (temperature, pH, water balance) regardless of external changes.
Sweating to cool the body down when its temperature rises is an example of
Negative feedback reverses a change (rising temperature) to restore the normal set point — this is the most common regulatory mechanism.
Which feedback mechanism intensifies a change rather than reversing it, such as during childbirth contractions?
Positive feedback amplifies a change and is used for processes with a clear endpoint, unlike the more common negative feedback.
In the circulatory system, blood vessels that carry blood AWAY from the heart are called
Arteries carry blood away from the heart; veins carry it back toward the heart.
Gas exchange between the lungs and blood occurs specifically in the
Alveoli are tiny air sacs where oxygen diffuses into blood and carbon dioxide diffuses out to be exhaled.
Hemoglobin, found in red blood cells, primarily functions to
Hemoglobin is a protein that binds oxygen in the lungs and carries it to tissues throughout the body.
Which organ is the main site of both chemical digestion and nutrient absorption?
The small intestine, aided by enzymes from the pancreas and bile from the liver, is where most digestion and absorption occur.
Villi in the small intestine function to
The many finger-like villi greatly increase the surface area available for absorbing nutrients into the bloodstream.
Although the liver and pancreas assist in digestion, food does NOT pass directly through them because they are
The liver and pancreas are accessory digestive organs — they contribute substances (bile, enzymes) but food does not physically travel through them.
A neuron transmits signals to the next neuron across a small gap called a
A synapse is the junction between neurons where chemical neurotransmitters carry the signal from one neuron to the next.
Which system uses antibodies and white blood cells to defend the body against pathogens?
The immune system defends against disease-causing pathogens using white blood cells and antibodies.
Vaccination works by
Vaccines train the immune system to recognize and quickly respond to a specific pathogen in the future by producing antibodies in advance.
The kidneys' main function in the excretory system is to
Kidneys filter blood to remove urea and excess water/salts, producing urine and helping maintain homeostasis.
The pancreas releasing insulin to lower blood glucose levels is an example of
Insulin is a hormone (endocrine system) that signals cells to absorb glucose, lowering blood sugar — a classic negative feedback example.
Compared to the nervous system, hormone signals from the endocrine system typically
Hormones travel through the bloodstream and generally act more slowly than electrical nerve impulses, but their effects often last longer.
Which best describes why organ systems must work together rather than in isolation?
Maintaining homeostasis requires organ systems (circulatory, respiratory, nervous, endocrine, etc.) to work together in a coordinated way.