Biology Study Guide

Which characteristic must an object show to be considered a living thing?

• It can move and responds to its surroundings quickly
• It is large enough to be seen without a microscope
• It contains water and carbon-based compounds
• It is made of cells and carries out metabolism

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

• contains no genetic material of its own, only protein
• cannot carry out metabolism or reproduce without a host cell
• is too small to be seen even with an electron microscope
• cannot mutate or change over many generations

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?

• Organ, tissue, cell, organism
• Cell, tissue, organ, organism
• Tissue, organism, cell, organ
• Organism, tissue, organ, cell

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

• dependent variable
• control group
• independent variable
• constant

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

• independent variable
• dependent variable
• constant
• hypothesis

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?

• To make the experiment take longer so results are more reliable
• To increase the sample size without changing any condition
• To provide a baseline for comparison with no treatment applied
• To test more than one independent variable at the same time

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

• proven true before testing
• testable and falsifiable
• agreed upon by all scientists
• the same as a theory

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

• an explanation strongly supported by a large body of evidence
• an educated guess that has not yet been tested by experiments
• a law that has been proven true and can never be revised
• the first step of the scientific method before data are gathered

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?

• All the fish in a lake, regardless of species
• All the trout in a single lake
• A single trout
• All the organisms and the water in a lake

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?

• A community includes abiotic factors, but an ecosystem has only living things
• A community is a larger unit that contains many ecosystems within it
• An ecosystem includes the community plus abiotic (non-living) factors
• A community and an ecosystem both include abiotic factors equally

An ecosystem = a community of populations PLUS the abiotic environment they interact with.

Which is a quantitative observation?

• The leaf is dark green
• The solution turned cloudy
• The beaker's temperature is 37°C
• The odor is sweet

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?

• Only the light color given to each group of plants
• Only the amount of water, since plant type does not matter
• Only the type of plant, since water can vary between groups
• Both amount of water and type of plant

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?

• Nothing new is seen, only the field of view gets larger
• Small structures like organelles become visible with more detail
• The whole specimen is seen at once with a wider field of view
• Magnification decreases so the structures appear smaller and clearer

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

• 4x
• 50x
• 400x
• 4000x

Total magnification = ocular × objective = 10 × 40 = 400x.

Which best describes reproduction as a characteristic of life?

• All organisms reproduce sexually
• Organisms produce offspring, either asexually or sexually
• Only animals reproduce
• Reproduction always produces genetically identical offspring

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

• metabolism
• response to stimuli
• homeostasis
• growth

Responding to an environmental stimulus (light) by growing toward it is a response to stimuli.

A scientist records that a plant grew 4 cm in one week. This is an example of:

• Qualitative data
• Quantitative data
• A hypothesis
• A theory

Quantitative data are measurements with numbers and units. Qualitative data describe qualities such as color.

Which is the best example of a testable hypothesis?

• If plants are given more love, then they will be happier
• If plants get more light, then they will grow taller
• If light is harmful to some people, then plants are pretty
• Plants are better to grow than any other living organisms

A testable hypothesis makes a prediction that an experiment can support or reject, often in if-then form.

Why do scientists repeat an experiment many times?

• To make the results more reliable
• To change the hypothesis
• To avoid using a control
• To make the independent variable larger

Repeated trials and larger samples reduce the effect of chance and make results more reliable.

Which is a constant (controlled variable) in an experiment testing how temperature affects bean seed germination?

• The temperature at which each group of seeds is kept
• The number of seeds in each group that germinate
• The height of the seedlings measured after one week
• The amount of water given to each seed

Controlled variables are kept the same so that only the independent variable (temperature) affects the result.

A student graphs the data from an experiment. The independent variable goes on the:

• y-axis
• x-axis
• Title only
• Key

The independent variable is plotted on the horizontal (x) axis and the dependent variable on the vertical (y) axis.

Which characteristic of life is shown when a seed becomes a seedling?

• Homeostasis
• Reproduction only
• Evolution of a species
• Growth and development

Living things grow and develop, following instructions in their DNA.

Which four elements make up about 96% of living tissue by mass?

• Na, Cl, K, Ca
• C, H, O, N
• Fe, Mg, P, S
• C, N, Na, K

Carbon, hydrogen, oxygen, and nitrogen are the 'big four' elements that dominate organic molecules.

Water is described as a polar molecule because

• the oxygen end is slightly positive and hydrogen ends are slightly negative
• the oxygen end is slightly negative and hydrogen ends are slightly positive
• its electrons are shared equally so there is no charge anywhere
• it is made of two oxygen atoms and one hydrogen atom

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

• adhesion
• cohesion
• hydrolysis
• dehydration synthesis

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 sticking to the stem) working with cohesion
• cohesion (water sticking to itself) working alone without any adhesion
• gravity and air pressure pushing water up from the roots
• evaporation in the roots drawing water upward through the stem

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?

• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

Proteins are polymers built from amino acid monomers, folded into specific shapes.

Which best describes an enzyme's role?

• It is a biological catalyst that lowers activation energy without being consumed
• It is a reactant that is permanently changed and used up in the reaction
• It is a molecule that works only at very high temperatures
• It is a type of carbohydrate that stores chemical energy

Enzymes speed up specific reactions by lowering activation energy and are reused, not consumed.

An enzyme exposed to extreme heat may become denatured, meaning

• its shape tightens so it works faster than before
• its amino acids turn into carbohydrates, changing its role
• its substrate unfolds instead while the enzyme stays intact
• its 3-D shape unfolds/changes, destroying its function

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?

• Hydrolysis
• Dehydration synthesis
• Diffusion
• Osmosis

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

• dehydration synthesis
• osmosis
• hydrolysis
• active transport

Hydrolysis adds water to break the bonds in a polymer, releasing individual monomers — this is how digestion works.

Lipids are best described as

• nonpolar molecules used for long-term energy storage and membranes
• polar molecules that dissolve easily in water and carry genetic data
• monomers that join together to form the structure of proteins
• the primary genetic material that stores information in cells

Lipids are hydrophobic (nonpolar), storing energy long-term and forming the cell membrane's phospholipid bilayer.

A disaccharide such as sucrose is formed from

• two monosaccharides joined together
• two amino acids joined together by a peptide bond
• two nucleotides joined together by a phosphate bond
• two fatty acids joined together with a glycerol

Sucrose is a disaccharide made of two joined monosaccharides (glucose + fructose).

Which statement about nucleic acids is correct?

• They are made of nucleotide monomers and store genetic information
• They are made of amino acid monomers and speed up reactions
• They are the main energy-storage molecule used by cells
• They are found only in prokaryotic cells and never in eukaryotes

Nucleic acids (DNA, RNA) are polymers of nucleotides and carry an organism's genetic information.

A saturated fat, compared to an unsaturated fat, typically

• has one or more double bonds between carbons and is liquid at room temperature
• has no double bonds between carbons and is solid at room temperature
• contains no carbon atoms
• is a type of carbohydrate

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?

• Its nonpolar nature allows it to dissolve oils and fats important for life
• It dissolves every substance in existence, including all nonpolar ones
• Its polarity allows it to dissolve many ionic and polar substances important for life
• It is the most chemically reactive molecule found in cells

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?

• An amino acid, a fatty acid, and a nitrogenous base
• Two sugars, a phosphate group, and a lipid chain
• A protein, a sugar, and a glycerol molecule
• A sugar, a phosphate group, and a nitrogenous base

Each nucleotide consists of a sugar, a phosphate group, and one nitrogenous base.

Which best explains why enzymes are considered reusable?

• They are broken down in each reaction and rebuilt by the cell afterward
• They catalyze only a single reaction, then are discarded by the cell
• They become part of the product when the reaction is complete
• They are not chemically changed or consumed by the reaction they catalyze

Enzymes speed up reactions without being permanently altered, so the same enzyme molecule can catalyze many reactions repeatedly.

What is the main function of carbohydrates in living things?

• Provide quick energy
• Store genetic information
• Speed up reactions
• Form the nucleus

Carbohydrates, especially glucose, are the main quick source of energy for cells.

Which elements are always found in proteins?

• Carbon, hydrogen, calcium and phosphorus in every protein
• Carbon, oxygen, iron and sodium in every protein
• Hydrogen, oxygen, phosphorus and potassium in every protein
• Carbon, hydrogen, oxygen and nitrogen

Proteins are made of amino acids that contain carbon, hydrogen, oxygen and nitrogen, and sometimes sulfur.

A solution with a pH of 3 is:

• A base
• An acid
• Neutral
• Pure water

Solutions with pH below 7 are acidic, pH 7 is neutral, and above 7 is basic.

Which macromolecule stores genetic information?

• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

DNA and RNA are nucleic acids that store and use genetic information.

Why does ice float on liquid water?

• Ice is less dense because it contains trapped air bubbles that add buoyancy
• Ice is less dense because its molecules are lighter than liquid water molecules
• Ice is less dense because hydrogen bonds hold molecules in an open lattice
• Ice is less dense because cold molecules move faster and spread out

In ice, hydrogen bonds hold the molecules in a rigid, spread-out structure, so ice is less dense.

Which lipid is a main part of the cell membrane?

• Starch
• Amino acid
• Phospholipid
• Nucleotide

Phospholipids form a double layer with water-loving heads and water-fearing tails.

According to the cell theory, all cells arise from

• spontaneous generation
• pre-existing cells
• non-living matter
• viruses

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?

• Ribosome
• DNA (genetic material)
• Cell membrane
• Cytoplasm

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'?

• Nucleus
• Ribosome
• Mitochondrion
• Golgi apparatus

The mitochondrion converts glucose energy into usable ATP through cellular respiration.

Which organelle packages and ships proteins to their destinations in vesicles?

• Lysosome
• Golgi apparatus
• Vacuole
• Cell wall

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?

• Mitochondrion
• Ribosome
• Cell wall and chloroplast
• Cell membrane

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

• active transport
• diffusion
• exocytosis
• phagocytosis

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

• shrink and shrivel as water moves out of the cell
• stay the same size because the water concentration is equal
• lose all its water as solutes rush into the cell
• swell and possibly burst as water moves in

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

• no energy, since it is a form of passive diffusion down a gradient
• ATP energy, since it works against the gradient (active transport)
• only a rise in temperature, since heat drives movement against gradients
• osmosis only, since water moves toward the higher concentration

Moving substances against their concentration gradient is active transport, which requires ATP.

Which sequence correctly orders the phases of mitosis?

• Metaphase, prophase, anaphase, telophase
• Prophase, metaphase, anaphase, telophase
• Telophase, anaphase, metaphase, prophase
• Anaphase, prophase, telophase, metaphase

Mitosis proceeds: prophase → metaphase → anaphase → telophase.

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

• Prophase
• Metaphase
• Anaphase
• Telophase

In anaphase, sister chromatids are pulled apart toward opposite poles of the cell.

The two daughter cells produced by mitosis are

• haploid and genetically different from each other and the parent
• each containing half the chromosome number of the parent cell
• genetically varied because of crossing-over between homologous chromosomes
• genetically identical to each other and the parent cell

Mitosis produces two genetically identical diploid daughter cells, used for growth and repair.

Which best describes the cell membrane's structure?

• A rigid wall of cellulose with water-loving molecules on both sides
• A single layer of protein with lipids scattered across its surface
• A phospholipid bilayer with hydrophobic tails facing outward and hydrophilic heads facing inward
• A phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward

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?

• Nucleus
• Chloroplast
• Cell membrane and ribosomes
• Mitochondrion

Every cell, prokaryotic or eukaryotic, has a cell membrane, cytoplasm, and ribosomes.

Lysosomes function mainly to

• contain digestive enzymes that break down waste and worn-out organelles
• produce ATP by breaking down glucose using oxygen in the cell
• store the cell's DNA and control the activities of the nucleus
• carry out photosynthesis to capture energy from sunlight in plants

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?

• Prophase
• Anaphase
• Interphase
• Telophase

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

• show no net change in water movement
• swell and burst from water rushing in
• shrivel as water leaves the cytoplasm
• actively expel water via vacuoles

In an isotonic solution, solute concentrations inside and outside are equal, so there is no net movement of water.

Which organelle contains the cell's DNA in a eukaryotic cell?

• Ribosome
• Nucleus
• Vacuole
• Cell wall

The nucleus stores DNA and controls cell activities.

Which organelle makes proteins?

• Lysosome
• Vacuole
• Nucleolus only
• Ribosome

Ribosomes build proteins from amino acids using instructions from mRNA.

A cell placed in a hypertonic solution will most likely:

• Lose water and shrink
• Gain water and burst
• Stay exactly the same
• Make more ATP

Water leaves the cell toward the higher solute concentration outside.

What is the main difference between active and passive transport?

• Passive transport uses ATP to move substances against a gradient
• Active transport moves only water across the cell membrane
• Passive transport moves only large particles through vesicles
• Active transport uses energy to move substances against a gradient

Active transport requires cellular energy and moves substances from low to high concentration.

During which phase of the cell cycle does the cell spend most of its life?

• Prophase
• Interphase
• Anaphase
• Telophase

Interphase includes G1, S and G2 and is when the cell grows and copies its DNA.

What is the function of the cell wall in plant cells?

• Make ATP
• Digest waste
• Control the nucleus
• Support and protection

The rigid cell wall gives plant cells shape and protects them.

ATP releases usable energy when

• the bond to its third (outer) phosphate group is broken, forming ADP
• a third phosphate group is added to ADP, forming ATP
• it is converted into glucose in the cell cytoplasm
• it absorbs light energy directly through its phosphate bonds

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)

• heterotroph
• autotroph
• decomposer only
• consumer

Autotrophs, like plants and algae, produce their own food (commonly via photosynthesis).

Which correctly represents the overall equation for photosynthesis?

• 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
• C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP energy released
• 6O₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6CO₂
• 6CO₂ + 6O₂ + light energy → C₆H₁₂O₆ + 6H₂O

Photosynthesis converts carbon dioxide and water into glucose and oxygen using light energy.

In a leaf cell, photosynthesis takes place in the

• mitochondrion
• nucleus
• chloroplast
• ribosome

Chloroplasts contain chlorophyll and are the site of photosynthesis.

Chlorophyll appears green because it

• absorbs green light while reflecting mainly red and blue light
• absorbs all wavelengths of visible light equally well
• reflects all wavelengths of light but absorbs ultraviolet only
• reflects green light while absorbing mainly red and blue light

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?

• 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
• C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
• C₆H₁₂O₆ → 6O₂ + light
• 6CO₂ + ATP → C₆H₁₂O₆

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?

• Chloroplast
• Ribosome
• Mitochondrion
• Golgi apparatus

Mitochondria are the main site where aerobic respiration converts glucose energy into ATP.

Fermentation (anaerobic respiration) differs from aerobic respiration in that fermentation

• produces much more ATP and does not require oxygen
• requires oxygen but produces much less ATP than aerobic respiration
• produces much less ATP and does not require oxygen
• occurs only in plants and yields far less ATP than aerobic respiration

Fermentation occurs without oxygen and yields far less ATP than aerobic respiration.

Lactic acid buildup in muscles during intense exercise is a result of

• aerobic respiration, occurring when oxygen supply is plentiful
• photosynthesis, occurring when glucose supply is limited
• active transport, occurring when ATP supply is limited
• lactic acid fermentation, occurring when oxygen supply is limited

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?

• They are unrelated, independent processes with no shared molecules
• Only plants perform respiration, while only animals perform photosynthesis
• The reactants of one are generally the same as the reactants of the other
• The products of one are generally the reactants of the other

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

• aerobic respiration
• alcoholic fermentation
• photosynthesis
• active transport

Yeast carries out alcoholic fermentation in the absence of oxygen, producing CO₂ and ethanol.

Which of the following is a heterotroph?

• A tree
• Algae
• A mushroom (fungus)
• Cyanobacteria (a photosynthetic bacterium)

Fungi are heterotrophs — they cannot photosynthesize and must obtain organic molecules from their environment.

The light-dependent reactions of photosynthesis take place in the

• stroma
• thylakoid membranes
• mitochondrial matrix
• cytoplasm

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

• thylakoid membranes
• stroma
• nucleus
• cell wall

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?

• Carbon dioxide
• Nitrogen
• Oxygen
• Hydrogen

Water is split during the light-dependent reactions, releasing oxygen as a byproduct.

Both autotrophs and heterotrophs carry out

• photosynthesis only, to make glucose from carbon dioxide
• cellular respiration to release energy from glucose
• neither respiration nor photosynthesis, relying on fermentation instead
• only fermentation to release energy from glucose without oxygen

All organisms, whether they make their own food or consume it, perform cellular respiration to release usable energy from glucose.

Which organelle captures light energy in a plant cell?

• Chloroplast
• Mitochondrion
• Nucleus
• Golgi apparatus

Chloroplasts contain chlorophyll, which absorbs light for photosynthesis.

Which are the reactants of photosynthesis?

• Glucose and oxygen
• Oxygen and water
• Carbon dioxide and water
• Glucose and carbon dioxide

Plants use carbon dioxide and water, plus light energy, to make glucose and oxygen.

What are the products of aerobic cellular respiration?

• Glucose and oxygen
• Carbon dioxide, water and ATP
• Lactic acid only
• Alcohol and oxygen

Cells break down glucose with oxygen to make carbon dioxide, water and ATP.

Where do the light-dependent reactions occur?

• Stroma
• Mitochondria
• Nucleus
• Thylakoid membranes

The light reactions occur in the thylakoid membranes of the chloroplast.

Why do muscles feel sore after hard exercise?

• Too much oxygen reaches the cells and damages the muscle fibers
• Mitochondria are destroyed during hard exercise and cannot be replaced
• Glucose in the muscles turns into DNA and clogs the cells
• Lactic acid builds up when cells use fermentation

When oxygen is low, muscle cells use fermentation, which makes lactic acid.

Which statement describes the relationship between ATP and ADP?

• ATP releases energy when it loses a phosphate group to become ADP
• ADP releases energy when it gains a phosphate group to become ATP
• ATP is a protein that stores more energy than ADP does
• ADP is a type of sugar that is made only in plants

The bond to the third phosphate is broken to release energy, forming ADP.

In DNA, adenine always pairs with which base?

• Guanine
• Cytosine
• Thymine
• Uracil

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

• chromosome
• gene
• nucleotide
• allele

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?

• 23
• 46
• 69
• 92

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

• homozygous dominant
• homozygous recessive
• heterozygous
• haploid

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?

• Only BB
• Only bb
• BB and Bb
• Only Bb

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?

• 1:1
• 1:2:1
• 3:1 dominant:recessive
• 4:0

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

• the sex of an organism based on its inherited chromosomes
• the exact age of an organism from its inherited genes
• which parent contributed more DNA to the offspring
• whether a dominant-phenotype organism is homozygous or heterozygous

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

• produces 2 identical diploid cells
• produces 4 genetically varied haploid cells
• does not involve chromosome separation
• only occurs in plant cells

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

• duplicating the entire genome so each gamete has two full copies
• destroying chromosomes so that fewer alleles are passed on
• exchanging segments of genetic material between homologous chromosomes
• occurring only in mitosis to copy chromosomes before division

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?

• The same number
• Twice as many
• Half as many
• Four times as many

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

• is single-stranded and uses uracil instead of thymine
• is double-stranded and uses thymine instead of uracil
• contains no nitrogenous bases and uses amino acids instead
• is found only in the nucleus and uses deoxyribose as its sugar

RNA is single-stranded, uses ribose sugar, and substitutes uracil (U) for thymine (T).

Homologous chromosomes are best described as

• identical copies of one chromosome made during mitosis only
• a matching pair, one from each parent, carrying genes for the same traits
• a pair found only in prokaryotic cells, one from each parent
• pairs that always carry identical alleles for the same traits

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?

• 0%
• 25%
• 50%
• 100%

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

• genotype
• phenotype
• allele
• chromosome

Phenotype is the observable/physical trait (e.g., eye color), while genotype is the underlying allele combination.

Fertilization restores the diploid chromosome number by

• combining two haploid gametes (n + n → 2n)
• doubling a single diploid cell
• removing half the chromosomes from a diploid cell
• crossing-over alone

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?

• Gene
• Nucleotide
• Chromosome
• Allele

A chromosome is DNA condensed and organized around proteins so it can be reliably copied and separated during cell division.

If a plant with genotype TT is crossed with tt, what is the genotype of all offspring?

• TT
• Tt
• tt
• Tt and tt

Each parent gives one allele, so every offspring gets T from one parent and t from the other.

What are the base pairing rules in DNA?

• A with G and C with T
• A with C and T with G
• A with U and C with G
• A with T and C with G

Adenine pairs with thymine and cytosine pairs with guanine.

A Punnett square for Bb × Bb predicts what ratio of genotypes?

• 1 BB : 2 Bb : 1 bb
• 3 BB : 1 bb
• 1 : 1
• All Bb

Two heterozygous parents produce 25% BB, 50% Bb and 25% bb.

What is a mutation?

• A copy of a chromosome
• A type of protein
• A change in the DNA sequence
• A trait that is always harmful

Mutations are changes in DNA and may be harmful, helpful or have no effect.

A mutation in which cells can be passed to offspring?

• Skin cells
• Gametes (sex cells)
• Muscle cells
• Bone cells

Only mutations in gametes or the cells that form them can be inherited.

Humans have 46 chromosomes in body cells. How many chromosomes are in a gamete?

• 46
• 92
• 12
• 23

Meiosis halves the chromosome number, so gametes are haploid with 23 chromosomes.

Which best summarizes Darwin's theory of natural selection?

• Individuals with favorable traits are more likely to survive and reproduce, passing those traits on
• All individuals in a population are identical, so the environment changes them
• Traits are inherited equally by all offspring regardless of the environment
• Evolution happens within a single organism's lifetime as it adapts to need

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?

• Overproduction of offspring
• Variation among individuals
• Every individual having identical traits
• Differential survival and reproduction

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

• analogous structures
• homologous structures
• vestigial structures
• convergent structures

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

• homologous structures
• vestigial structures
• analogous structures
• identical structures

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

• homologous structure
• vestigial structure
• analogous structure
• dominant structure

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?

• Comparative embryology
• The fossil record
• DNA sequencing
• Vestigial structures

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

• be unrelated, since DNA similarity says nothing about ancestry
• have identical phenotypes and have evolved independently of each other
• share a more recent common ancestor than less similar species
• share a more distant common ancestor than less similar species

Greater DNA similarity indicates a more recent common ancestor and closer evolutionary relationship.

Biological 'fitness' is best defined as

• an organism's physical strength and speed compared to other individuals
• the overall size and health of an organism during its adult life
• an organism's relative ability to survive and reproduce successfully in its environment
• how long an individual organism lives compared to others of its species

Fitness refers to reproductive success in a given environment, not physical strength alone.

Geographic isolation can lead to speciation because

• a physical barrier prevents any mutations, so the isolated groups stay genetically identical and form separate species
• separated populations can no longer interbreed and accumulate different mutations/adaptations over time
• isolated populations compete for the same resources, so the stronger group eliminates the weaker one over time
• migrating individuals mix genes between the groups, which creates new species by combining their separate traits

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

• live in different locations and have never met each other
• can no longer interbreed and produce fertile offspring
• look physically different from one another in size and color
• have been given different names by scientists after study

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

• a need to use their beaks more often, which made them bigger and was passed to their offspring
• a constant mixing of populations across the islands, which averaged out their beak traits over many generations
• geographic isolation and natural selection favoring beaks suited to different food sources on each island
• sudden mutations caused by volcanic activity on the islands, which created new beak shapes in a single generation

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

• in any environment, since adaptations are always universally beneficial
• in a very different environment, such as a rainforest
• for that same species
• for related species

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 happens when an individual organism changes its traits to match its environment during its lifetime
• Evolution is a gradual process driven by a species' need to improve, so organisms purposely develop helpful traits
• Evolution occurs only when populations split into separate species, never within a single, continuous population
• Evolution is a change in a population's inherited traits over many generations, not within one organism's lifetime

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

• comparing the skeletons of adult organisms across related species
• observing similar patterns of embryonic development among related organisms
• studying fossilized eggs and nests of extinct animals
• comparing the diets of embryos across different species

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

• genetic drift acting only on a small bacterial population by chance
• a vestigial trait that no longer serves any function
• comparative embryology showing shared ancestry between bacteria
• natural selection favoring resistant individuals that survive and reproduce

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?

• Variation has no role, since the environment alone causes the changes
• Without variation, there would be no differing traits for the environment to select among
• Variation matters only for asexual organisms, since they cannot mutate
• Variation prevents selection because every individual would then survive equally

Natural selection requires that individuals differ in traits so that some variants are more favored by the environment than others.

Which is the best example of an adaptation?

• Thick fur that helps an animal survive in cold climates
• An animal losing its tail in an accident during its lifetime
• A person learning to swim after taking lessons
• A plant that grows taller after being watered daily

Adaptations are inherited traits that improve survival and reproduction in a particular environment.

Fossils found in younger layers of rock are usually:

• Older than those below them
• Always extinct
• More similar to modern species
• Made of metal

Younger layers are generally on top and contain fossils more like modern organisms.

What causes genetic variation in a population that natural selection acts on?

• Exercise
• Mutations and sexual reproduction
• Eating different foods
• Learning

New alleles arise by mutation, and sexual reproduction shuffles alleles into new combinations.

Which statement is true about the theory of evolution?

• It is just a guess that has not been tested by scientists
• It claims individuals change during their life to meet their needs
• It says organisms try to become better so they can survive
• It is supported by many lines of evidence such as fossils and DNA

A scientific theory is a well-supported explanation, and evolution is supported by fossils, anatomy, embryos and DNA.

Why are bacteria becoming resistant to antibiotics?

• Bacteria decide to become resistant when antibiotics are present
• Antibiotics make bacteria directly stronger by changing their genes
• Resistant bacteria survive and reproduce more than others
• Humans get used to the medicine so it works less well

This is natural selection: the medicine removes non-resistant bacteria and resistant ones pass on their genes.

Which pair of animals most likely shares the most recent common ancestor?

• Two species that live in the same place
• Two species of similar size
• Two species with very similar DNA
• Two species that eat the same food

More similar DNA sequences indicate a more recent common ancestor.

Sunlight, temperature, and soil pH are all examples of

• biotic factors
• abiotic factors
• producers
• limiting nutrients only

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

• habitat
• niche
• population
• biome

Niche describes an organism's role/job in the ecosystem; habitat is simply where it physically lives.

In a food chain, producers are always

• autotrophs that form the base of the chain
• consumers that eat other organisms at the base of the chain
• decomposers that break down dead matter for the chain
• predators found at the top of the chain

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)

• herbivore
• carnivore
• omnivore
• decomposer

Omnivores consume both producers (plants) and other consumers (animals).

Fungi and bacteria that break down dead organisms and recycle nutrients are classified as

• producers
• consumers
• decomposers
• abiotic factors

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

• shows only one species and its single food source in an ecosystem
• shows the many interconnected, overlapping feeding relationships in an ecosystem
• applies only to aquatic ecosystems and never to land habitats
• never includes decomposers or the recycling of nutrients

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?

• 100%
• 50%
• 10%
• 1%

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?

• Because so much energy is lost as heat at each level that not enough remains to support additional levels
• Because predators at higher levels are too large to be supported by the plants and small animals at the bottom
• Because carbon dioxide and nutrients become too scarce at each level to allow the growth of more organisms
• Because most producers die off before they can be eaten, leaving only a few primary consumers to feed on

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

• limiting factor
• carrying capacity
• niche
• biotic potential

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?

• The population will keep growing indefinitely since food becomes more plentiful
• Resources become scarce, increasing starvation/disease/competition until the population declines
• The carrying capacity will automatically rise to match the larger population
• Nothing will change because the ecosystem adjusts to any population size

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?

• Available food supply
• The color of nearby rocks
• The time of day only
• The name of the species

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

• has no effect on native species because they share the same resources
• helps native species by adding biodiversity and food sources
• can outcompete native species that lack natural defenses against it
• improves the ecosystem's stability because it adds new interactions

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

• decomposers breaking down toxins so they become less concentrated at higher levels
• producers filtering out all toxins so none reach higher trophic levels
• pollution building up in tissues and becoming more concentrated at higher trophic levels
• the 10% rule removing toxins as energy is lost at each level

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

• increasing available habitat and giving species more space to live
• destroying/fragmenting habitat that many species depend on
• increasing the carrying capacity for all species in the area
• having no impact on population sizes of the species living there

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 is only the living populations, with soil, water, and climate counted separately
• An ecosystem is one population of a species together with its predators and parasites
• An ecosystem includes the community of populations PLUS the physical, non-living environment
• An ecosystem includes only producers and decomposers, excluding consumers and the physical environment

An ecosystem combines the biological community with the physical (abiotic) environment they interact with.

Which of the following represents a correct simplified food chain?

• Fox → rabbit → grass
• Grass → rabbit → fox
• Rabbit → grass → fox
• Fox → grass → rabbit

Energy flows from producer (grass) to primary consumer (rabbit) to secondary consumer (fox).

What is the source of energy for most ecosystems?

• Soil
• The sun
• Water
• Decomposers

Producers capture sunlight and make food energy for the rest of the food web.

What does a decomposer do in an ecosystem?

• Makes its own food from sunlight and releases oxygen to the air
• Breaks down dead matter and returns nutrients to the soil
• Eats only plants and returns nutrients through its waste
• Produces oxygen and carbohydrates for the rest of the ecosystem

Decomposers, such as fungi and bacteria, recycle nutrients.

If a food chain starts with grass, which organism is a secondary consumer?

• A rabbit that eats grass and is eaten by a hawk
• A mouse that eats grass and is eaten by a snake
• A snake that eats a mouse that ate grass
• A hawk that eats a snake that ate a mouse

The mouse is the primary consumer, so the snake eating the mouse is a secondary consumer.

Which action most helps conserve biodiversity?

• Introducing invasive species
• Clearing forests
• Protecting habitats
• Polluting rivers

Protecting habitat keeps species and their interactions intact.

The carbon cycle is balanced when carbon released by respiration and burning is:

• Destroyed completely so that it leaves the cycle for good
• Taken up again by photosynthesis and oceans
• Stored only in the air as carbon dioxide gas
• Turned into oxygen by the oceans and soil bacteria

Photosynthesis and the oceans remove carbon dioxide from the air, balancing release.

What happens to a population when it exceeds the carrying capacity?

• It usually declines due to limited resources
• It keeps growing forever because resources adjust to demand
• It stays exactly the same because birth and death rates match
• It stops needing food because it has adapted to the shortage

Resources run out, so death rates rise or birth rates fall until the population drops.

Homeostasis refers to an organism's ability to

• grow larger over time as it takes in nutrients
• maintain a stable internal environment despite external changes
• reproduce sexually to pass genes to its offspring
• evolve within a single generation to match its environment

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

• positive feedback
• negative feedback
• active transport
• fermentation

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?

• Negative feedback
• Positive feedback
• Homeostatic feedback
• Enzyme feedback

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

• veins
• capillaries
• arteries
• alveoli

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

• trachea
• alveoli
• esophagus
• stomach

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

• digest food in the small intestine using enzymes
• produce antibodies that fight pathogens in the blood
• bind to and transport oxygen throughout the body
• filter waste from the blood and form urine

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?

• Stomach
• Esophagus
• Small intestine
• Large intestine

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

• produce stomach acid to break down proteins in food
• store undigested waste before it leaves the body
• break down starch into sugars in the mouth
• increase surface area for efficient nutrient absorption

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

• not part of the digestive system at all, since they only filter blood
• part of the respiratory system that supports gas exchange
• accessory organs that produce digestive substances like bile and enzymes
• involved only in excretion and the removal of nitrogenous waste

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

• synapse
• alveolus
• villus
• nephron

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?

• Digestive system
• Immune system
• Excretory system
• Endocrine system

The immune system defends against disease-causing pathogens using white blood cells and antibodies.

Vaccination works by

• giving the body antibiotics that kill the pathogen directly, so the infection cannot take hold in the future
• passing antibodies from another person's blood into the body, which provides temporary protection against disease
• stimulating the body to produce heat and fever in advance, which prevents the pathogen from multiplying later
• exposing the immune system to a weakened/inactive pathogen so it can 'remember' how to fight it later

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

• digest fats and proteins using enzymes released into the small intestine
• produce hormones only and have no role in filtering the blood
• filter nitrogenous waste and excess water/salts from the blood, forming urine
• exchange oxygen and carbon dioxide between the blood and the air

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

• the endocrine system regulating the body via a hormone in a negative feedback loop
• the nervous system acting alone through fast electrical impulses in neurons
• positive feedback with no endpoint that raises blood glucose even further
• a structural adaptation that changes the shape of the pancreas over time

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

• act more slowly but often have longer-lasting effects
• act faster than nerve impulses and have shorter-lasting effects
• have no real effect on the body unless nerve impulses are present
• regulate only digestion and have no effect on growth or metabolism

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?

• They don't actually interact, since each system works independently
• Homeostasis for the whole organism depends on coordinated function among multiple organ systems
• Only one organ system is needed for survival, so the others are optional
• Organ systems compete against each other for limited resources in the body

Maintaining homeostasis requires organ systems (circulatory, respiratory, nervous, endocrine, etc.) to work together in a coordinated way.

Which system transports nutrients and oxygen around the body?

• Circulatory system
• Skeletal system
• Digestive system
• Excretory system

The heart pumps blood through vessels to deliver oxygen and nutrients.

Which part of the brain controls balance and coordination?

• Cerebrum
• Brain stem only
• Cerebellum
• Spinal cord

The cerebellum coordinates movement and balance.

What is the main role of white blood cells?

• Carry oxygen
• Fight infection
• Clot blood
• Make hormones

White blood cells are part of the immune system and defend against pathogens.

Which organ produces bile that helps digest fats?

• Stomach
• Kidney
• Pancreas
• Liver

The liver makes bile, which is stored in the gallbladder and released into the small intestine.

Insulin and glucagon work together to:

• Keep blood glucose levels stable
• Fight infection
• Digest proteins
• Remove carbon dioxide

Insulin lowers blood glucose and glucagon raises it, an example of negative feedback.

Which pathway does air take into the lungs?

• Mouth, esophagus, stomach, lungs
• Trachea, alveoli, bronchi, nose
• Nose, trachea, bronchi, alveoli
• Nose, esophagus, alveoli, bronchi

Air passes through the nose, trachea and bronchi to the alveoli where gas exchange occurs.

Which statement best describes a scientific theory?

• A tentative guess that has not been tested by any experiment
• The result of a single experiment that has been repeated once
• A personal opinion about how something in nature probably works
• A well-supported explanation based on a large body of evidence

Theories explain many observations and are tested repeatedly.

Homeostasis is:

• The movement of cells toward a source of food or light
• The process of cell division that produces new body cells
• The change of species over many generations of time
• The maintenance of stable internal conditions

Examples include regulating temperature and blood sugar.

Enzymes speed up reactions by:

• Raising the temperature
• Lowering the activation energy
• Changing the products
• Being consumed

They are reusable and specific to their substrates.

Which organelle is the site of protein synthesis?

• Ribosome
• Golgi apparatus
• Lysosome
• Vacuole

Ribosomes translate mRNA into polypeptides.

Osmosis is the diffusion of:

• Solutes across a semipermeable membrane
• Water against its concentration gradient
• Water across a semipermeable membrane
• Gases across a fully permeable membrane

Water moves toward the higher solute concentration.

Most ATP in cellular respiration is produced in the:

• Glycolysis
• Krebs cycle
• Fermentation
• Electron transport chain

Oxidative phosphorylation produces the majority of ATP.

The light reactions of photosynthesis produce:

• Glucose
• Carbon dioxide
• ATP, NADPH and oxygen
• Water only

The Calvin cycle uses ATP and NADPH to build sugar.

What is the probability that two carriers (Aa x Aa) have a child with the recessive trait?

• 1/2
• 3/4
• 1/4
• 1/8

Only the aa genotype shows the trait.

DNA replication is semiconservative, meaning:

• Each new DNA molecule has one original strand and one new strand
• Both strands of each new DNA molecule are newly made
• Only one of the two original strands is copied each time
• The DNA is copied twice before the cell divides

The Meselson-Stahl experiment demonstrated this.

Natural selection requires:

• Heritable variation that affects survival or reproduction
• Acquired traits that individuals gain during life being passed on
• An organism's need for a trait causing that trait to appear
• Equal survival and reproduction for every individual in a population

Individuals with advantageous traits tend to leave more offspring.

Which is evidence for evolution?

• Only the estimated age of the Earth and the oceans
• Fossils, homologous structures and DNA similarities
• A single species that has not changed over time
• A lack of variation among individuals in a population

Multiple independent lines of evidence support common descent.

Carrying capacity is:

• The birth rate of a population in ideal conditions
• The maximum population size an environment can sustain
• The total number of species living in an ecosystem
• The total biomass of all organisms in a habitat

Limited resources prevent unlimited growth.

Producers occupy which trophic level?

• The second
• The third
• The top
• The first trophic level

They capture energy from sunlight or chemicals.

The primary function of the kidneys is to:

• Digest food and absorb nutrients into the blood
• Filter blood and regulate fluid and waste balance
• Produce hormones for growth and control reproduction only
• Pump blood and carry oxygen to the body's tissues

They also help regulate blood pressure and pH.

Insulin, secreted by the pancreas, functions to:

• Raise blood glucose
• Digest fats
• Lower blood glucose
• Increase heart rate

It helps cells take up glucose.