Why is a water molecule polar?

Oxygen pulls shared electrons more strongly than hydrogen, giving oxygen a partial negative charge and the hydrogens partial positive charges.

Which elements make up most biological molecules?

Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur—often shortened to CHNOPS.

What is the relationship between a monomer and a polymer?

Monomers are small building blocks; polymers are chains or networks made from repeated monomers.

What is a monosaccharide's main role in cells?

It can provide quick energy and serve as a building block for larger carbohydrates.

Why do lipids mix poorly with water?

Most of their bonds are nonpolar, so water cannot form favorable interactions with them.

What three parts make up a nucleotide?

A five-carbon sugar, a phosphate group, and a nitrogenous base.

What parts of an amino acid vary and stay constant?

The amino group, carboxyl group, hydrogen, and central carbon are shared; the side chain, or R group, varies.

What does pH measure?

The negative logarithm of hydrogen-ion concentration; lower pH means more hydrogen ions.

What is a hydrogen bond in liquid water?

A weak attraction between a partially positive hydrogen on one water molecule and a partially negative oxygen on another.

How does an unsaturated fatty acid differ from a saturated one?

An unsaturated fatty acid has at least one carbon–carbon double bond; a saturated fatty acid has none.

What does dehydration synthesis do?

It joins subunits with a covalent bond while removing the elements of water.

How does cohesion help water move through a plant?

Hydrogen bonds keep water molecules linked, helping a continuous column rise through xylem.

How do plants and animals differ in short-term glucose storage?

Plants store glucose mainly as starch; animals store it mainly as glycogen.

How does a cis double bond affect a fatty-acid tail?

It introduces a bend that prevents neighboring tails from packing tightly.

How does adhesion support water transport in narrow tubes?

Water sticks to polar surfaces, helping it resist gravity along cell walls.

Which base pairing distinguishes RNA from DNA?

RNA uses uracil, so adenine pairs with uracil instead of thymine.

What stabilizes common protein secondary structures?

Hydrogen bonds between atoms in the polypeptide backbone.

Why can carbon form so many biological structures?

It has four valence electrons and can form four stable covalent bonds, including chains, branches, and rings.

Why can some insects stand on water?

Cohesion among surface water molecules creates high surface tension.

What does hydrolysis do to a biological polymer?

It adds the elements of water to break a covalent bond between subunits.

Why are fats useful for long-term energy storage?

Their many C–H bonds store substantial chemical energy, and hydrophobic storage adds little water mass.

How does water buffer rapid temperature change?

Breaking and forming many hydrogen bonds absorbs or releases substantial heat, giving water a high specific heat.

What does antiparallel mean for a DNA double helix?

Its two strands run in opposite directions: one 5′→3′ and the other 3′→5′.

What mainly drives a protein's tertiary structure?

Interactions among side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

What is a trace element?

An element an organism needs in very small amounts, such as iron in many electron-transfer proteins.

Why does sweating cool an organism?

The fastest water molecules escape as vapor, carrying heat away from the surface.

A cell builds a polysaccharide from sugars. Is water consumed or released?

Released. Forming each linkage by dehydration removes water.

Why can branching help a storage polysaccharide release glucose quickly?

More branch ends give enzymes more sites to work at once.

What makes a phospholipid amphipathic?

It has a polar, hydrophilic head and nonpolar, hydrophobic tails.

Where is biological information encoded in a nucleic acid?

In the linear sequence of nucleotide bases.

What is quaternary protein structure?

The arrangement of two or more polypeptide subunits into one functional protein.

Why does ice float on liquid water?

Stable hydrogen bonds hold ice molecules in an open lattice, making ice less dense than liquid water.

How does electronegativity affect a covalent bond?

A difference in attraction for electrons makes electron sharing unequal and can create a polar bond.

Why do phospholipids form bilayers in water?

Hydrophilic heads face water while hydrophobic tails cluster away from it.

To which end are nucleotides added during nucleic-acid synthesis?

The 3′ end of the growing strand.

Why can one amino-acid substitution change protein function?

It can alter side-chain interactions, folding, stability, or an active or binding site.

How does a buffer resist a pH change?

It can accept added hydrogen ions or donate them when hydrogen-ion concentration falls.

Why is water a useful solvent for cells?

Its partial charges surround ions and other polar molecules, separating and dispersing them.

Why do functional groups matter in organic molecules?

They give carbon skeletons predictable chemical properties, such as polarity, acidity, or reactivity.

Why can two polymers built from similar monomers have different functions?

Their monomer sequence, branching, length, and three-dimensional shape can differ.

A seedling consumes stored starch. What happens to the starch?

Hydrolysis breaks it into smaller sugars that can enter energy pathways.

What are two biological roles of steroids?

Some act as signaling molecules, and cholesterol helps stabilize animal cell membranes.

What bond forms the backbone of a nucleic-acid strand?

Covalent phosphodiester bonds link the sugar of one nucleotide to the phosphate of the next.

What does denaturation do to a protein?

It disrupts the protein's three-dimensional shape and often its function without usually breaking the primary peptide chain.

An enzyme works best near pH 7 but slows at pH 3. What is a likely explanation?

Extra hydrogen ions changed charges and interactions that maintain the enzyme's active shape.

AP Biology Flashcards: Complete 8-Unit Course Review

Review all 8 AP Biology units with original flashcards for concepts, pathways, experimental design, data interpretation, and FRQ reasoning.

من إعداد Open Study Contributor

حول هذه الرزمة

AP Biology Flashcards: Complete 8-Unit Course Review

The current AP Biology framework covers eight units, from chemistry of life through ecology. This 540-card deck turns that full course into short, original retrieval prompts, with science-practice reasoning mixed into the biology instead of parked in a separate section.

What the cards practice

The cards connect terms to functions, structures to consequences, pathway steps to inputs, outputs, locations, and regulation, and evidence to biological claims. Separate prompts cover useful reverse mappings when they are real study tasks—for example, identifying a process from its location or choosing the inference supported by a result. Short original scenarios also practice describing patterns, explaining mechanisms, predicting changes, justifying claims, setting up calculations, and evaluating evidence.

The deck does not mechanically reverse every definition or pathway. It leaves out copied exam material, scoring language, official figures, exhaustive protocols, broad essay prompts, textbook-specific trivia, and advanced-college details outside the current course boundary.

Learning order

The sequence follows Units 1–8. Within each unit it moves from prerequisites to processes, applications, experiments, data, and FRQ-style reasoning, while spacing close variants apart. Long-term spacing and interleaving are left to the review scheduler.

What still needs practice

Flashcards are useful for recall and small reasoning moves, but they cannot replace laboratory work, graph construction, extended data analysis, or timed multiple-choice and free-response practice. Use the deck beside class labs and full original practice questions.

Scope and provenance

The course boundary was reviewed on September 1, 2026 against the College Board AP Biology course page, the Fall 2025 Course and Exam Description, its current clarifications and corrections, the 2026–27 course-change table, and the current exam page. The selection, prompts, answers, examples, sequence, metadata, and cover are independently created from common biological knowledge and source checks. No exam questions, scoring guidelines, CED text, answer keys, or official figures were copied or transformed.

The Common knowledge · CC0 1.0 label applies to the original wording, organization, metadata, and generated media to the extent applicable rights exist. It does not claim ownership of biological facts, AP or College Board names, or third-party source material.

This independent, unofficial study deck is not affiliated with, endorsed by, or sponsored by College Board. AP and College Board names identify the course and exam only. Official requirements: https://apcentral.collegeboard.org/courses/ap-biology

بطاقات هذه الرزمة

البطاقة ١
السؤال
Why is a water molecule polar?
الإجابة
Oxygen pulls shared electrons more strongly than hydrogen, giving oxygen a partial negative charge and the hydrogens partial positive charges.
البطاقة ٢
السؤال
Which elements make up most biological molecules?
الإجابة
Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur—often shortened to CHNOPS.
البطاقة ٣
السؤال
What is the relationship between a monomer and a polymer?
الإجابة
Monomers are small building blocks; polymers are chains or networks made from repeated monomers.
البطاقة ٤
السؤال
What is a monosaccharide's main role in cells?
الإجابة
It can provide quick energy and serve as a building block for larger carbohydrates.
البطاقة ٥
السؤال
Why do lipids mix poorly with water?
الإجابة
Most of their bonds are nonpolar, so water cannot form favorable interactions with them.
البطاقة ٦
السؤال
What three parts make up a nucleotide?
الإجابة
A five-carbon sugar, a phosphate group, and a nitrogenous base.
البطاقة ٧
السؤال
What parts of an amino acid vary and stay constant?
الإجابة
The amino group, carboxyl group, hydrogen, and central carbon are shared; the side chain, or R group, varies.
البطاقة ٨
السؤال
What does pH measure?
الإجابة
The negative logarithm of hydrogen-ion concentration; lower pH means more hydrogen ions.
البطاقة ٩
السؤال
What is a hydrogen bond in liquid water?
الإجابة
A weak attraction between a partially positive hydrogen on one water molecule and a partially negative oxygen on another.
البطاقة ١٠
السؤال
How does an unsaturated fatty acid differ from a saturated one?
الإجابة
An unsaturated fatty acid has at least one carbon–carbon double bond; a saturated fatty acid has none.
البطاقة ١١
السؤال
What bond links amino acids in a polypeptide?
الإجابة
A peptide bond.
البطاقة ١٢
السؤال
What does dehydration synthesis do?
الإجابة
It joins subunits with a covalent bond while removing the elements of water.
البطاقة ١٣
السؤال
How does cohesion help water move through a plant?
الإجابة
Hydrogen bonds keep water molecules linked, helping a continuous column rise through xylem.
البطاقة ١٤
السؤال
How do plants and animals differ in short-term glucose storage?
الإجابة
Plants store glucose mainly as starch; animals store it mainly as glycogen.
البطاقة ١٥
السؤال
What determines a protein's primary structure?
الإجابة
Its amino-acid sequence.
البطاقة ١٦
السؤال
How does a cis double bond affect a fatty-acid tail?
الإجابة
It introduces a bend that prevents neighboring tails from packing tightly.
البطاقة ١٧
السؤال
How does adhesion support water transport in narrow tubes?
الإجابة
Water sticks to polar surfaces, helping it resist gravity along cell walls.
البطاقة ١٨
السؤال
Which base pairing distinguishes RNA from DNA?
الإجابة
RNA uses uracil, so adenine pairs with uracil instead of thymine.
البطاقة ١٩
السؤال
What stabilizes common protein secondary structures?
الإجابة
Hydrogen bonds between atoms in the polypeptide backbone.
البطاقة ٢٠
السؤال
Why can carbon form so many biological structures?
الإجابة
It has four valence electrons and can form four stable covalent bonds, including chains, branches, and rings.
البطاقة ٢١
السؤال
Why can some insects stand on water?
الإجابة
Cohesion among surface water molecules creates high surface tension.
البطاقة ٢٢
السؤال
What does hydrolysis do to a biological polymer?
الإجابة
It adds the elements of water to break a covalent bond between subunits.
البطاقة ٢٣
السؤال
What carbohydrate strengthens plant cell walls?
الإجابة
Cellulose.
البطاقة ٢٤
السؤال
Why are fats useful for long-term energy storage?
الإجابة
Their many C–H bonds store substantial chemical energy, and hydrophobic storage adds little water mass.
البطاقة ٢٥
السؤال
How does water buffer rapid temperature change?
الإجابة
Breaking and forming many hydrogen bonds absorbs or releases substantial heat, giving water a high specific heat.
البطاقة ٢٦
السؤال
What does antiparallel mean for a DNA double helix?
الإجابة
Its two strands run in opposite directions: one 5′→3′ and the other 3′→5′.
البطاقة ٢٧
السؤال
What mainly drives a protein's tertiary structure?
الإجابة
Interactions among side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.
البطاقة ٢٨
السؤال
What is a trace element?
الإجابة
An element an organism needs in very small amounts, such as iron in many electron-transfer proteins.
البطاقة ٢٩
السؤال
Why does sweating cool an organism?
الإجابة
The fastest water molecules escape as vapor, carrying heat away from the surface.
البطاقة ٣٠
السؤال
A cell builds a polysaccharide from sugars. Is water consumed or released?
الإجابة
Released. Forming each linkage by dehydration removes water.
البطاقة ٣١
السؤال
Why can branching help a storage polysaccharide release glucose quickly?
الإجابة
More branch ends give enzymes more sites to work at once.
البطاقة ٣٢
السؤال
What makes a phospholipid amphipathic?
الإجابة
It has a polar, hydrophilic head and nonpolar, hydrophobic tails.
البطاقة ٣٣
السؤال
Where is biological information encoded in a nucleic acid?
الإجابة
In the linear sequence of nucleotide bases.
البطاقة ٣٤
السؤال
What is quaternary protein structure?
الإجابة
The arrangement of two or more polypeptide subunits into one functional protein.
البطاقة ٣٥
السؤال
Why does ice float on liquid water?
الإجابة
Stable hydrogen bonds hold ice molecules in an open lattice, making ice less dense than liquid water.
البطاقة ٣٦
السؤال
How does electronegativity affect a covalent bond?
الإجابة
A difference in attraction for electrons makes electron sharing unequal and can create a polar bond.
البطاقة ٣٧
السؤال
A digestive reaction adds water while splitting a macromolecule. What reaction is this?
الإجابة
Hydrolysis.
البطاقة ٣٨
السؤال
What links monosaccharides in a polysaccharide?
الإجابة
Glycosidic covalent bonds.
البطاقة ٣٩
السؤال
Why do phospholipids form bilayers in water?
الإجابة
Hydrophilic heads face water while hydrophobic tails cluster away from it.
البطاقة ٤٠
السؤال
To which end are nucleotides added during nucleic-acid synthesis?
الإجابة
The 3′ end of the growing strand.
البطاقة ٤١
السؤال
Why can one amino-acid substitution change protein function?
الإجابة
It can alter side-chain interactions, folding, stability, or an active or binding site.
البطاقة ٤٢
السؤال
How does a buffer resist a pH change?
الإجابة
It can accept added hydrogen ions or donate them when hydrogen-ion concentration falls.
البطاقة ٤٣
السؤال
Why is water a useful solvent for cells?
الإجابة
Its partial charges surround ions and other polar molecules, separating and dispersing them.
البطاقة ٤٤
السؤال
Why do functional groups matter in organic molecules?
الإجابة
They give carbon skeletons predictable chemical properties, such as polarity, acidity, or reactivity.
البطاقة ٤٥
السؤال
Why can two polymers built from similar monomers have different functions?
الإجابة
Their monomer sequence, branching, length, and three-dimensional shape can differ.
البطاقة ٤٦
السؤال
A seedling consumes stored starch. What happens to the starch?
الإجابة
Hydrolysis breaks it into smaller sugars that can enter energy pathways.
البطاقة ٤٧
السؤال
What are two biological roles of steroids?
الإجابة
Some act as signaling molecules, and cholesterol helps stabilize animal cell membranes.
البطاقة ٤٨
السؤال
What bond forms the backbone of a nucleic-acid strand?
الإجابة
Covalent phosphodiester bonds link the sugar of one nucleotide to the phosphate of the next.
البطاقة ٤٩
السؤال
What does denaturation do to a protein?
الإجابة
It disrupts the protein's three-dimensional shape and often its function without usually breaking the primary peptide chain.
البطاقة ٥٠
السؤال
An enzyme works best near pH 7 but slows at pH 3. What is a likely explanation?
الإجابة
Extra hydrogen ions changed charges and interactions that maintain the enzyme's active shape.
البطاقة ٥١
السؤال
What structure encloses every cell?
الإجابة
A plasma membrane.
البطاقة ٥٢
السؤال
What is the nucleus's main function?
الإجابة
It houses most eukaryotic DNA and is a major site of DNA replication and transcription.
البطاقة ٥٣
السؤال
Why does surface-area-to-volume ratio fall as a cell grows?
الإجابة
Volume increases with the cube of length, while surface area increases with the square.
البطاقة ٥٤
السؤال
What does the fluid mosaic model describe?
الإجابة
A dynamic phospholipid bilayer containing mobile proteins, sterols, and carbohydrates.
البطاقة ٥٥
السؤال
What drives simple diffusion?
الإجابة
Random molecular motion produces net movement from higher to lower concentration.
البطاقة ٥٦
السؤال
How does active transport differ from facilitated diffusion?
الإجابة
Active transport moves a substance against its gradient using energy; facilitated diffusion moves it down a gradient.
البطاقة ٥٧
السؤال
Why does compartmentalization increase cellular efficiency?
الإجابة
It concentrates enzymes and substrates and maintains distinct conditions for different reactions.
البطاقة ٥٨
السؤال
When should a light microscope be preferred over an electron microscope?
الإجابة
When observing living cells or dynamic processes at lower resolution.
البطاقة ٥٩
السؤال
What does the nucleolus produce?
الإجابة
Ribosomal RNA and early ribosome subunits.
البطاقة ٦٠
السؤال
Does passive transport require direct cellular energy?
الإجابة
No. It moves substances down an electrochemical or concentration gradient.
البطاقة ٦١
السؤال
What feature separates prokaryotic from eukaryotic cells?
الإجابة
Eukaryotic cells have a membrane-bound nucleus and other membrane-bound organelles; prokaryotic cells do not.
البطاقة ٦٢
السؤال
Which membrane region blocks most ions and polar molecules?
الإجابة
The hydrophobic interior formed by phospholipid tails.
البطاقة ٦٣
السؤال
What happens on rough endoplasmic reticulum?
الإجابة
Bound ribosomes make proteins for secretion, membranes, or the endomembrane system.
البطاقة ٦٤
السؤال
How does facilitated diffusion differ from simple diffusion?
الإجابة
It uses a channel or carrier protein but still moves a substance down its gradient.
البطاقة ٦٥
السؤال
Where is prokaryotic DNA usually located?
الإجابة
In a nucleoid region rather than inside a membrane-bound nucleus.
البطاقة ٦٦
السؤال
How does cholesterol affect an animal membrane?
الإجابة
It buffers fluidity, limiting excess movement when warm and preventing tight packing when cool.
البطاقة ٦٧
السؤال
What does smooth endoplasmic reticulum do?
الإجابة
It synthesizes lipids, detoxifies some compounds, and stores calcium in specialized cells.
البطاقة ٦٨
السؤال
What determines a channel protein's selectivity?
الإجابة
Its pore size, shape, charge, and gating behavior.
البطاقة ٦٩
السؤال
What does the sodium–potassium pump accomplish?
الإجابة
Using ATP, it exports three sodium ions and imports two potassium ions per cycle.
البطاقة ٧٠
السؤال
What do ribosomes do in both prokaryotic and eukaryotic cells?
الإجابة
They translate mRNA into polypeptides.
البطاقة ٧١
السؤال
What is the Golgi apparatus's role?
الإجابة
It modifies, sorts, and packages proteins and lipids arriving from the endoplasmic reticulum.
البطاقة ٧٢
السؤال
What is osmosis?
الإجابة
Net movement of water across a selectively permeable membrane toward lower free-water concentration.
البطاقة ٧٣
السؤال
Why does a high surface-area-to-volume ratio help a cell?
الإجابة
It provides more membrane area per unit of cytoplasm for exchange with the environment.
البطاقة ٧٤
السؤال
How do unsaturated phospholipid tails affect membrane fluidity?
الإجابة
Their bends reduce tight packing, usually increasing fluidity.
البطاقة ٧٥
السؤال
Trace a secreted protein after translation begins.
الإجابة
Rough ER → transport vesicle → Golgi → secretory vesicle → plasma membrane.
البطاقة ٧٦
السؤال
What happens to an animal cell in a hypotonic solution?
الإجابة
Water enters; the cell swells and may lyse.
البطاقة ٧٧
السؤال
What is cotransport?
الإجابة
The downhill movement of one substance powers the uphill transport of another through the same protein.
البطاقة ٧٨
السؤال
What is the main role of a cell wall?
الإجابة
It provides structural support and helps prevent excessive expansion.
البطاقة ٧٩
السؤال
What do lysosomes do?
الإجابة
Their hydrolytic enzymes digest macromolecules and recycle damaged cell parts in an acidic compartment.
البطاقة ٨٠
السؤال
What happens to an animal cell in a hypertonic solution?
الإجابة
Water leaves; the cell shrinks.
البطاقة ٨١
السؤال
How do intestinal microvilli improve absorption?
الإجابة
They increase membrane surface area without greatly increasing cell volume.
البطاقة ٨٢
السؤال
What can an integral membrane protein do?
الإجابة
It can transport substances, receive signals, catalyze reactions, or anchor cell structures.
البطاقة ٨٣
السؤال
What is a central vacuole's major role in a plant cell?
الإجابة
It stores solutes and water and helps maintain turgor pressure.
البطاقة ٨٤
السؤال
What happens to a plant cell in a hypotonic solution?
الإجابة
Water enters and turgor pressure rises; the cell wall helps prevent bursting.
البطاقة ٨٥
السؤال
How can a proton gradient power sucrose uptake in a plant cell?
الإجابة
Protons flow down their gradient through a symporter that carries sucrose uphill.
البطاقة ٨٦
السؤال
What evidence supports the endosymbiotic origin of mitochondria?
الإجابة
They have double membranes, circular DNA, bacterial-like ribosomes, and divide independently by a similar process.
البطاقة ٨٧
السؤال
Which overall energy-conversion pathway mainly occurs in mitochondria?
الإجابة
Most stages of aerobic cellular respiration and ATP production.
البطاقة ٨٨
السؤال
What happens to a plant cell in a hypertonic solution?
الإجابة
Water leaves, turgor falls, and the membrane may pull from the wall during plasmolysis.
البطاقة ٨٩
السؤال
Why can't a standard light microscope resolve a ribosome clearly?
الإجابة
A ribosome is smaller than the microscope's diffraction-limited resolution.
البطاقة ٩٠
السؤال
How do bacterial and plant cell walls differ?
الإجابة
Bacterial walls usually contain peptidoglycan; plant walls contain cellulose.
البطاقة ٩١
السؤال
Which overall energy-conversion pathway occurs in chloroplasts?
الإجابة
Photosynthesis: converting light energy into chemical energy and fixing carbon.
البطاقة ٩٢
السؤال
A cubical cell doubles each side length. How do surface area and volume change?
الإجابة
Surface area increases 4-fold; volume increases 8-fold.
البطاقة ٩٣
السؤال
What is the role of membrane carbohydrates?
الإجابة
They help cells recognize and interact with one another.
البطاقة ٩٤
السؤال
What is water potential?
الإجابة
A measure predicting water movement; water moves from higher to lower water potential.
البطاقة ٩٥
السؤال
How do microtubules support a cell?
الإجابة
They resist compression, form tracks for motors, and build structures such as spindles, cilia, and flagella.
البطاقة ٩٦
السؤال
What is endocytosis?
الإجابة
The plasma membrane folds inward to bring material into the cell in a vesicle.
البطاقة ٩٧
السؤال
What evidence supports the endosymbiotic origin of chloroplasts?
الإجابة
They share bacterial-like DNA, ribosomes, division, and a double membrane consistent with engulfment.
البطاقة ٩٨
السؤال
In a membrane-permeability test, what is the independent variable?
الإجابة
The factor deliberately changed, such as temperature or solute identity.
البطاقة ٩٩
السؤال
How do microfilaments support cell movement?
الإجابة
Actin filaments interact with motor proteins to change cell shape, contract, and move materials.
البطاقة ١٠٠
السؤال
What does the cytosol contain?
الإجابة
Water, ions, small molecules, and proteins where many metabolic reactions occur.
البطاقة ١٠١
السؤال
Why can diffusion limit cell size?
الإجابة
As dimensions grow, molecules must travel farther, while exchange area does not keep pace with metabolic volume.
البطاقة ١٠٢
السؤال
What does selective permeability mean?
الإجابة
The membrane allows some substances to cross more readily than others.
البطاقة ١٠٣
السؤال
What is an intermediate filament's general role?
الإجابة
It provides durable mechanical strength and helps anchor structures.
البطاقة ١٠٤
السؤال
How does adding a nonpenetrating solute affect water potential?
الإجابة
It makes solute potential, and usually total water potential, more negative.
البطاقة ١٠٥
السؤال
What is exocytosis?
الإجابة
A vesicle fuses with the plasma membrane and releases contents outside the cell.
البطاقة ١٠٦
السؤال
Why can lysosomal enzymes digest safely inside a cell?
الإجابة
A membrane isolates the acidic enzymes from most cytosolic components.
البطاقة ١٠٧
السؤال
Why include an untreated membrane sample in an experiment?
الإجابة
It provides a control baseline for judging the treatment's effect.
البطاقة ١٠٨
السؤال
Why doesn't cell size alone identify whether a cell is prokaryotic?
الإجابة
Sizes overlap; the presence or absence of internal membrane-bound structures is stronger evidence.
البطاقة ١٠٩
السؤال
Why are organelle interactions important?
الإجابة
Cell functions often require products to move through several specialized compartments rather than one organelle working alone.
البطاقة ١١٠
السؤال
What graph would show a size constraint clearly?
الإجابة
Plot cell size on the x-axis and surface-area-to-volume ratio on the y-axis; the ratio should decline as size rises.
البطاقة ١١١
السؤال
Which molecules cross a phospholipid bilayer most easily without proteins?
الإجابة
Small nonpolar molecules, such as oxygen and carbon dioxide.
البطاقة ١١٢
السؤال
Two solutions have equal water potential. What is the net water movement?
الإجابة
None, although water molecules still move both ways.
البطاقة ١١٣
السؤال
Why is ATP loss likely to disrupt ion balance?
الإجابة
ATP-powered pumps stop maintaining gradients, so passive leaks move ions toward equilibrium.
البطاقة ١١٤
السؤال
How does folding an internal membrane help an organelle?
الإجابة
It increases surface area for membrane-bound reactions without a matching increase in volume.
البطاقة ١١٥
السؤال
A dye leaves heated cells faster than unheated cells. What conclusion is supported?
الإجابة
Heating increased membrane permeability under the tested conditions; the data alone do not identify the exact molecular damage.
البطاقة ١١٦
السؤال
What does an enzyme change in a reaction?
الإجابة
It lowers activation energy, increasing reaction rate without changing the reaction's overall free-energy change.
البطاقة ١١٧
السؤال
What makes a reaction exergonic?
الإجابة
It releases free energy and has a negative change in free energy under the stated conditions.
البطاقة ١١٨
السؤال
What are the overall inputs and outputs of photosynthesis?
الإجابة
Carbon dioxide and water use light energy to produce carbohydrate and oxygen.
البطاقة ١١٩
السؤال
What are the overall reactants and products of aerobic cellular respiration?
الإجابة
Organic fuel and oxygen are converted mainly to carbon dioxide, water, and ATP, with heat released.
البطاقة ١٢٠
السؤال
How should reaction rate be calculated from product data?
الإجابة
Divide the change in product amount by the elapsed time.
البطاقة ١٢١
السؤال
What makes an enzyme substrate-specific?
الإجابة
The active site's shape and chemical properties favor particular substrates.
البطاقة ١٢٢
السؤال
Where do the light reactions occur?
الإجابة
In the thylakoid membranes of chloroplasts.
البطاقة ١٢٣
السؤال
Where does glycolysis occur?
الإجابة
In the cytosol.
البطاقة ١٢٤
السؤال
What makes a reaction endergonic?
الإجابة
It requires a net input of free energy and has a positive change in free energy.
البطاقة ١٢٥
السؤال
What is induced fit?
الإجابة
Substrate binding shifts the enzyme's shape into a form that better supports catalysis.
البطاقة ١٢٦
السؤال
Where does the Calvin cycle occur?
الإجابة
In the chloroplast stroma.
البطاقة ١٢٧
السؤال
What does glycolysis produce per glucose?
الإجابة
Two pyruvate, a net two ATP, and two NADH.
البطاقة ١٢٨
السؤال
How can cells drive an endergonic reaction?
الإجابة
They couple it to a sufficiently exergonic reaction so the combined free-energy change is negative.
البطاقة ١٢٩
السؤال
Why isn't an enzyme consumed by the reaction it catalyzes?
الإجابة
It returns to a reusable form after products leave the active site.
البطاقة ١٣٠
السؤال
What do photosynthetic pigments do?
الإجابة
They absorb particular wavelengths and transfer excitation energy into the light reactions.
البطاقة ١٣١
السؤال
Does glycolysis require oxygen directly?
الإجابة
No. It can run without oxygen if NAD⁺ is regenerated.
البطاقة ١٣٢
السؤال
What does ATP hydrolysis commonly provide?
الإجابة
Usable free energy and a phosphate group that can change a molecule's reactivity or protein shape.
البطاقة ١٣٣
السؤال
How does substrate concentration affect rate at low concentrations?
الإجابة
Rate usually rises because more substrate molecules collide with available active sites.
البطاقة ١٣٤
السؤال
Why do chlorophyll-containing leaves reflect green light?
الإجابة
Chlorophyll absorbs green wavelengths less strongly than red and blue wavelengths.
البطاقة ١٣٥
السؤال
Where does pyruvate oxidation occur in a eukaryotic cell?
الإجابة
In the mitochondrial matrix.
البطاقة ١٣٦
السؤال
Why is ATP called an energy-coupling molecule?
الإجابة
Its hydrolysis links energy-releasing processes to cellular work.
البطاقة ١٣٧
السؤال
Why does enzyme rate plateau at high substrate concentration?
الإجابة
Most active sites are occupied, so enzyme amount becomes limiting.
البطاقة ١٣٨
السؤال
What is photolysis of water?
الإجابة
Light-driven splitting of water that supplies electrons and protons and releases oxygen.
البطاقة ١٣٩
السؤال
What happens during pyruvate oxidation?
الإجابة
Each pyruvate becomes acetyl-CoA, releasing carbon dioxide and reducing NAD⁺ to NADH.
البطاقة ١٤٠
السؤال
Why measure an initial enzyme rate?
الإجابة
Substrate depletion and product buildup have had less time to distort the rate.
البطاقة ١٤١
السؤال
How can high temperature reduce enzyme activity?
الإجابة
Heat can disrupt interactions that maintain the enzyme's functional shape.
البطاقة ١٤٢
السؤال
What is photosystem II's key contribution?
الإجابة
It excites electrons and replaces them by oxidizing water.
البطاقة ١٤٣
السؤال
Where does the citric acid cycle occur in eukaryotes?
الإجابة
In the mitochondrial matrix.
البطاقة ١٤٤
السؤال
What is oxidation?
الإجابة
Loss of electrons, often accompanied by loss of hydrogen or gain of oxygen.
البطاقة ١٤٥
السؤال
Why does each enzyme have an optimal pH range?
الإجابة
pH changes charges on amino-acid side chains and can alter binding or folding.
البطاقة ١٤٦
السؤال
What does the photosynthetic electron transport chain build?
الإجابة
A proton gradient across the thylakoid membrane.
البطاقة ١٤٧
السؤال
What is the citric acid cycle's main energy role?
الإجابة
It oxidizes acetyl groups and transfers electrons to NADH and FADH₂, making a small amount of ATP.
البطاقة ١٤٨
السؤال
In a photosynthesis experiment, why keep leaf area constant?
الإجابة
Leaf area affects light capture and gas exchange, so changing it could confound the tested factor.
البطاقة ١٤٩
السؤال
How does a competitive inhibitor reduce enzyme activity?
الإجابة
It competes with substrate for the active site.
البطاقة ١٥٠
السؤال
How does chloroplast ATP synthase make ATP?
الإجابة
Protons flow from the thylakoid space to the stroma through ATP synthase, driving phosphorylation of ADP.
البطاقة ١٥١
السؤال
Where is the respiratory electron transport chain located in eukaryotes?
الإجابة
In the inner mitochondrial membrane.
البطاقة ١٥٢
السؤال
What is reduction?
الإجابة
Gain of electrons, often accompanied by gain of hydrogen or loss of oxygen.
البطاقة ١٥٣
السؤال
How can extra substrate weaken competitive inhibition?
الإجابة
More substrate increases the chance that substrate, rather than inhibitor, occupies the active site.
البطاقة ١٥٤
السؤال
What is photosystem I's key contribution?
الإجابة
It re-energizes electrons used to reduce NADP⁺ to NADPH.
البطاقة ١٥٥
السؤال
What is oxygen's role in aerobic respiration?
الإجابة
It is the final electron acceptor and combines with electrons and protons to form water.
البطاقة ١٥٦
السؤال
A respiration graph gets steeper after temperature rises. What does the slope show?
الإجابة
A higher rate of the measured respiratory change, such as oxygen consumption per unit time.
البطاقة ١٥٧
السؤال
How does a noncompetitive inhibitor act?
الإجابة
It binds away from the active site and changes enzyme activity, often by altering shape.
البطاقة ١٥٨
السؤال
What products of the light reactions feed the Calvin cycle?
الإجابة
ATP and NADPH.
البطاقة ١٥٩
السؤال
How does electron transport create a proton gradient?
الإجابة
Released electron energy pumps protons from the matrix to the intermembrane space.
البطاقة ١٦٠
السؤال
What do NADH and FADH₂ carry?
الإجابة
High-energy electrons and associated hydrogen used in energy-transfer pathways.
البطاقة ١٦١
السؤال
What is allosteric regulation?
الإجابة
A regulator binds at one site and changes activity at another site on the protein.
البطاقة ١٦٢
السؤال
What does carbon fixation accomplish?
الإجابة
It incorporates inorganic carbon dioxide into an organic molecule.
البطاقة ١٦٣
السؤال
What is oxidative phosphorylation?
الإجابة
ATP production powered by electron transport and chemiosmosis.
البطاقة ١٦٤
السؤال
Why use multiple biological replicates in a rate experiment?
الإجابة
They reveal natural variation and make the estimated treatment effect more reliable.
البطاقة ١٦٥
السؤال
What is fermentation's central purpose?
الإجابة
It regenerates NAD⁺ so glycolysis can continue without an active electron transport chain.
البطاقة ١٦٦
السؤال
How does feedback inhibition control a pathway?
الإجابة
A pathway's end product inhibits an earlier enzyme, reducing unnecessary production.
البطاقة ١٦٧
السؤال
What enzyme fixes carbon in the Calvin cycle?
الإجابة
Rubisco.
البطاقة ١٦٨
السؤال
How does mitochondrial ATP synthase make ATP?
الإجابة
Protons flow into the matrix through ATP synthase, driving ADP phosphorylation.
البطاقة ١٦٩
السؤال
Why do cells use stepwise electron transfers?
الإجابة
They release energy in manageable increments that can be captured instead of lost mostly as heat.
البطاقة ١٧٠
السؤال
What is a cofactor?
الإجابة
A nonprotein helper, often a metal ion or small organic coenzyme, required for some enzymes to function.
البطاقة ١٧١
السؤال
What are the three broad phases of the Calvin cycle?
الإجابة
Carbon fixation, reduction, and regeneration of the carbon-dioxide acceptor RuBP.
البطاقة ١٧٢
السؤال
How does lactic-acid fermentation regenerate NAD⁺?
الإجابة
NADH reduces pyruvate to lactate, returning electrons to form NAD⁺.
البطاقة ١٧٣
السؤال
What is substrate-level phosphorylation?
الإجابة
An enzyme transfers a phosphate directly from an intermediate to ADP.
البطاقة ١٧٤
السؤال
Error bars overlap broadly between two treatments. What is a careful conclusion?
الإجابة
The graph alone does not show a clear difference; a suitable statistical analysis and design context are still needed.
البطاقة ١٧٥
السؤال
Why run an enzyme assay without enzyme?
الإجابة
It measures the uncatalyzed background change and tests whether enzyme is required.
البطاقة ١٧٦
السؤال
How does alcoholic fermentation regenerate NAD⁺?
الإجابة
Pyruvate loses carbon dioxide, and the remaining compound is reduced to ethanol as NADH becomes NAD⁺.
البطاقة ١٧٧
السؤال
What is G3P's role in photosynthesis?
الإجابة
It is a three-carbon product that can leave the Calvin cycle and help build carbohydrates.
البطاقة ١٧٨
السؤال
Why are mitochondrial cristae useful?
الإجابة
They increase inner-membrane area for electron transport chains and ATP synthase.
البطاقة ١٧٩
السؤال
What does phosphorylation often do to a molecule?
الإجابة
It adds a phosphate group that can increase reactivity or alter a protein's shape and activity.
البطاقة ١٨٠
السؤال
A mutation lowers an enzyme's maximum rate but not substrate binding. What is a plausible effect?
الإجابة
It may impair a catalytic step or reduce the number of functional enzyme molecules.
البطاقة ١٨١
السؤال
Why must the Calvin cycle regenerate RuBP?
الإجابة
RuBP is the carbon-dioxide acceptor needed for another turn of fixation.
البطاقة ١٨٢
السؤال
A chemical lowers oxygen use but not glycolysis. Which stage is most directly implicated?
الإجابة
Aerobic electron transport or a process supplying it, because glycolysis itself does not consume oxygen.
البطاقة ١٨٣
السؤال
How would closed stomata affect photosynthesis?
الإجابة
Carbon dioxide entry falls, which can limit carbon fixation even when light is available.
البطاقة ١٨٤
السؤال
A plant receives green light only. Predict its photosynthetic rate.
الإجابة
It will usually be lower than under equally intense red or blue light because common chlorophylls absorb green poorly.
البطاقة ١٨٥
السؤال
Why does fermentation yield less ATP per glucose than aerobic respiration?
الإجابة
It relies on glycolysis alone and leaves much of glucose's chemical energy in reduced end products.
البطاقة ١٨٦
السؤال
How does low ATP affect respiration pathway activity?
الإجابة
It usually relieves inhibition of key enzymes, increasing fuel oxidation and ATP production.
البطاقة ١٨٧
السؤال
How can oxygen production estimate photosynthetic rate?
الإجابة
Oxygen is a light-reaction product, so its production per unit time can serve as a rate proxy under controlled conditions.
البطاقة ١٨٨
السؤال
What happens to electron transport if oxygen is removed?
الإجابة
The chain backs up because electrons lack a final acceptor; NADH accumulates and oxidative phosphorylation stops.
البطاقة ١٨٩
السؤال
Why does a light-response curve eventually level off?
الإجابة
Another factor, such as carbon dioxide supply, temperature, or enzyme capacity, becomes limiting.
البطاقة ١٩٠
السؤال
An uncoupler lets protons cross the inner mitochondrial membrane. What happens?
الإجابة
The gradient weakens, ATP production falls, and more energy is released as heat even if electron transport continues.
البطاقة ١٩١
السؤال
What is direct-contact signaling?
الإجابة
A membrane-bound molecule or cell junction communicates with an adjacent cell.
البطاقة ١٩٢
السؤال
What are the three broad stages of cell signaling?
الإجابة
Reception, transduction, and response.
البطاقة ١٩٣
السؤال
How can a receptor mutation block a response even when ligand is present?
الإجابة
The receptor may fail to bind ligand, change shape, or activate the first relay protein.
البطاقة ١٩٤
السؤال
What is negative feedback?
الإجابة
A response reduces the original stimulus, helping stabilize a variable near a functional range.
البطاقة ١٩٥
السؤال
What happens during G1 phase?
الإجابة
The cell grows, performs normal functions, and prepares for DNA replication.
البطاقة ١٩٦
السؤال
Cells show response values of 2, 7, and 18 after rising ligand doses. Describe the trend.
الإجابة
The response increases with ligand dose across the tested range.
البطاقة ١٩٧
السؤال
What happens during reception?
الإجابة
A ligand binds its receptor and changes the receptor's activity or shape.
البطاقة ١٩٨
السؤال
What is paracrine signaling?
الإجابة
A cell releases a local regulator that acts on nearby target cells.
البطاقة ١٩٩
السؤال
What happens during S phase?
الإجابة
DNA is replicated, producing sister chromatids for each chromosome.
البطاقة ٢٠٠
السؤال
A response occurs without ligand. What pathway defect is plausible?
الإجابة
A receptor or downstream relay protein may be constitutively active.
البطاقة ٢٠١
السؤال
What happens during signal transduction?
الإجابة
Intracellular steps relay and often amplify information from the activated receptor.
البطاقة ٢٠٢
السؤال
What is synaptic signaling?
الإجابة
A neuron releases neurotransmitter across a short synaptic gap to a target cell.
البطاقة ٢٠٣
السؤال
What happens during G2 phase?
الإجابة
The cell grows, checks replicated DNA, and prepares the machinery for division.
البطاقة ٢٠٤
السؤال
Why compare receptor-positive and receptor-negative cells?
الإجابة
The comparison tests whether the receptor is necessary for the observed response.
البطاقة ٢٠٥
السؤال
What counts as a cellular response?
الإجابة
A change in gene expression, enzyme activity, ion flow, secretion, movement, division, or another cell behavior.
البطاقة ٢٠٦
السؤال
How does insulin participate in negative feedback?
الإجابة
High blood glucose promotes insulin release, which lowers blood glucose and reduces the original stimulus.
البطاقة ٢٠٧
السؤال
What happens during mitosis?
الإجابة
A eukaryotic nucleus separates duplicated chromosomes into two nuclei.
البطاقة ٢٠٨
السؤال
What is endocrine signaling?
الإجابة
Hormones travel through circulatory fluid to target cells that may be far away.
البطاقة ٢٠٩
السؤال
What does a protein kinase do?
الإجابة
It transfers a phosphate from ATP to a target protein.
البطاقة ٢١٠
السؤال
A drug blocks a kinase, and the final response disappears. What is supported?
الإجابة
The kinase is required somewhere in that pathway under the tested conditions.
البطاقة ٢١١
السؤال
What happens during cytokinesis?
الإجابة
The cytoplasm divides to form separate daughter cells.
البطاقة ٢١٢
السؤال
How does glucagon participate in glucose homeostasis?
الإجابة
Low blood glucose promotes glucagon release, which raises blood glucose toward the normal range.
البطاقة ٢١٣
السؤال
What does a protein phosphatase do?
الإجابة
It removes a phosphate group from a target protein.
البطاقة ٢١٤
السؤال
What is a ligand?
الإجابة
A signaling molecule that binds specifically to a receptor.
البطاقة ٢١٥
السؤال
What is the G1 checkpoint's broad role?
الإجابة
It checks size, nutrients, growth signals, and DNA condition before replication.
البطاقة ٢١٦
السؤال
Why can't one inhibitor experiment prove a protein's exact pathway position?
الإجابة
Off-target effects and indirect dependencies can produce the same outcome.
البطاقة ٢١٧
السؤال
Why are phosphorylation cascades reversible?
الإجابة
Kinases add phosphates, while phosphatases remove them and reset pathway components.
البطاقة ٢١٨
السؤال
What is positive feedback?
الإجابة
A response strengthens the initiating stimulus until a separate event stops the loop.
البطاقة ٢١٩
السؤال
What is the G2 checkpoint's broad role?
الإجابة
It checks whether DNA replication is complete and damage is repaired before mitosis.
البطاقة ٢٢٠
السؤال
Why don't all cells respond to the same hormone?
الإجابة
Only cells with a compatible receptor and response machinery can respond.
البطاقة ٢٢١
السؤال
What is a second messenger?
الإجابة
A small intracellular molecule or ion that relays a signal after receptor activation.
البطاقة ٢٢٢
السؤال
How can rescue with an active downstream protein map a pathway?
الإجابة
If the response returns despite an upstream block, the rescued protein likely acts downstream of that block.
البطاقة ٢٢٣
السؤال
What does the spindle checkpoint verify?
الإجابة
Every chromosome is correctly attached to spindle microtubules before sister chromatids separate.
البطاقة ٢٢٤
السؤال
Why is blood clotting a positive-feedback process?
الإجابة
Activated platelets recruit and activate more platelets until the break is sealed.
البطاقة ٢٢٥
السؤال
Name two common second messengers.
الإجابة
Cyclic AMP and calcium ions.
البطاقة ٢٢٦
السؤال
A mutant receptor binds ligand but never becomes phosphorylated. Predict downstream signaling.
الإجابة
It will likely fall or disappear if receptor phosphorylation is required to recruit relay proteins.
البطاقة ٢٢٧
السؤال
How do cyclins regulate the cell cycle?
الإجابة
Their concentrations rise and fall, activating cyclin-dependent kinases at specific stages.
البطاقة ٢٢٨
السؤال
Why must DNA replicate before mitosis?
الإجابة
Each daughter nucleus needs a complete copy of the genome.
البطاقة ٢٢٩
السؤال
Where do receptors for many peptide hormones sit?
الإجابة
In the plasma membrane, because these polar ligands do not readily cross the lipid bilayer.
البطاقة ٢٣٠
السؤال
How can a signaling pathway amplify a weak signal?
الإجابة
One activated component activates many downstream molecules at successive steps.
البطاقة ٢٣١
السؤال
What is the dependent variable in a ligand-dose experiment?
الإجابة
The measured response, such as reporter activity, enzyme phosphorylation, or ion concentration.
البطاقة ٢٣٢
السؤال
What do cyclin-dependent kinases do?
الإجابة
When paired with cyclins, they phosphorylate targets that drive cell-cycle transitions.
البطاقة ٢٣٣
السؤال
Why doesn't positive feedback usually maintain homeostasis by itself?
الإجابة
It drives change away from the starting state and needs an external stop.
البطاقة ٢٣٤
السؤال
What is a G protein's signaling role?
الإجابة
It switches activity when bound to GTP and relays information from certain membrane receptors to effectors.
البطاقة ٢٣٥
السؤال
How would you test whether calcium is required for a response?
الإجابة
Block the calcium rise while keeping other conditions matched, then compare the response with a vehicle control.
البطاقة ٢٣٦
السؤال
What is apoptosis?
الإجابة
Programmed cell death that dismantles a cell in a controlled way.
البطاقة ٢٣٧
السؤال
Where are receptors for many steroid hormones?
الإجابة
Inside the cell, where lipid-soluble hormones can bind after crossing the membrane.
البطاقة ٢٣٨
السؤال
How can an ion-channel receptor create a rapid response?
الإجابة
Ligand binding opens or closes a pore, quickly changing ion movement and membrane conditions.
البطاقة ٢٣٩
السؤال
Why test several ligand concentrations?
الإجابة
A dose–response series can reveal sensitivity, saturation, and whether effects scale with ligand.
البطاقة ٢٤٠
السؤال
Why is apoptosis useful in multicellular organisms?
الإجابة
It removes damaged, infected, or unneeded cells with limited harm to neighbors.
البطاقة ٢٤١
السؤال
A thermostat-like pathway overshoots repeatedly. What defect is plausible?
الإجابة
Delayed sensing or response can make negative feedback correct too late.
البطاقة ٢٤٢
السؤال
How can an intracellular receptor affect gene expression?
الإجابة
The ligand–receptor complex can act directly or indirectly as a transcription regulator.
البطاقة ٢٤٣
السؤال
Cells lacking protein X divide despite DNA damage. Justify a checkpoint claim.
الإجابة
Protein X likely supports a DNA-damage checkpoint because its absence links damage with continued division; rescue or pathway tests would strengthen the claim.
البطاقة ٢٤٤
السؤال
What aligns at the metaphase plate?
الإجابة
Duplicated chromosomes attached to spindle microtubules from opposite poles.
البطاقة ٢٤٥
السؤال
How can failed checkpoints contribute to cancer?
الإجابة
Cells with damage or abnormal signals can keep dividing instead of pausing or dying.
البطاقة ٢٤٦
السؤال
How can gap junctions support communication?
الإجابة
They connect neighboring animal-cell cytoplasms so small molecules and ions can pass directly.
البطاقة ٢٤٧
السؤال
Why can the same ligand trigger different responses in two cell types?
الإجابة
The cells can express different receptors, relay proteins, targets, or genes.
البطاقة ٢٤٨
السؤال
Two pathways share one relay protein. What can happen if that protein is blocked?
الإجابة
Both responses may weaken, showing pathway crosstalk or a shared component.
البطاقة ٢٤٩
السؤال
During which mitotic stage do sister chromatids separate?
الإجابة
Anaphase.
البطاقة ٢٥٠
السؤال
What defines a malignant tumor?
الإجابة
Its cells invade surrounding tissue and may spread to distant sites.
البطاقة ٢٥١
السؤال
How would loss of a feedback inhibitor affect a biosynthetic pathway?
الإجابة
The pathway may stay active and overproduce its end product.
البطاقة ٢٥٢
السؤال
What ends a signaling response?
الإجابة
Ligand removal, receptor inactivation, GTP hydrolysis, messenger breakdown, or dephosphorylation can shut it down.
البطاقة ٢٥٣
السؤال
A pathway diagram shows A activates B, and B inhibits C. Predict C after A activation.
الإجابة
C activity should decrease, assuming the shown links are the relevant controlling interactions.
البطاقة ٢٥٤
السؤال
A phosphatase that normally turns off an activated relay protein is inhibited. Predict the effect on that pathway.
الإجابة
Phosphorylated targets may stay active longer, extending or strengthening the response.
البطاقة ٢٥٥
السؤال
A drug prevents spindle formation. Where should the cycle stop?
الإجابة
At the spindle checkpoint before anaphase, because chromosomes cannot attach correctly.
البطاقة ٢٥٦
السؤال
What is the purpose of meiosis?
الإجابة
It produces haploid cells and reshuffles inherited alleles for sexual reproduction.
البطاقة ٢٥٧
السؤال
What is crossing over?
الإجابة
Exchange of corresponding DNA segments between nonsister chromatids of homologous chromosomes.
البطاقة ٢٥٨
السؤال
What does Mendel's law of segregation describe?
الإجابة
An individual's two alleles for a gene separate into different gametes.
البطاقة ٢٥٩
السؤال
Why do X-linked recessive traits often appear more frequently in XY individuals?
الإجابة
They have only one X chromosome, so one recessive allele on it can determine the phenotype.
البطاقة ٢٦٠
السؤال
What is incomplete dominance?
الإجابة
The heterozygote has a phenotype intermediate between the two homozygotes.
البطاقة ٢٦١
السؤال
What does a chi-square goodness-of-fit test compare?
الإجابة
Observed category counts with counts expected under a stated model.
البطاقة ٢٦٢
السؤال
What is a homologous chromosome pair?
الإجابة
Two chromosomes carrying the same gene locations, one inherited from each parent, possibly with different alleles.
البطاقة ٢٦٣
السؤال
What does Mendel's law of independent assortment describe?
الإجابة
Alleles of genes on different chromosomes, or far apart on one chromosome, assort independently during gamete formation.
البطاقة ٢٦٤
السؤال
What is genetic linkage?
الإجابة
Genes close together on the same chromosome tend to be inherited together.
البطاقة ٢٦٥
السؤال
When does crossing over occur?
الإجابة
During prophase I after homologs pair.
البطاقة ٢٦٦
السؤال
How do sister chromatids differ from homologous chromosomes?
الإجابة
Sister chromatids are replicated copies of one chromosome; homologs are the maternal and paternal versions of the same chromosome type.
البطاقة ٢٦٧
السؤال
For Aa × Aa, what is the expected genotype ratio?
الإجابة
1 AA : 2 Aa : 1 aa.
البطاقة ٢٦٨
السؤال
How can linked genes produce recombinant offspring?
الإجابة
Crossing over can exchange DNA between the gene locations.
البطاقة ٢٦٩
السؤال
What is the usual null hypothesis for a Mendelian chi-square test?
الإجابة
Any difference between observed and expected counts is due to chance sampling under the proposed inheritance model.
البطاقة ٢٧٠
السؤال
What happens to homologous chromosomes in meiosis I?
الإجابة
They pair and then separate into different cells.
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البطاقة ٢٧١
السؤال
For Aa × Aa with complete dominance, what is the expected phenotype ratio?
الإجابة
3 dominant phenotype : 1 recessive phenotype.
البطاقة ٢٧٢
السؤال
How does crossing over increase variation?
الإجابة
It creates chromosomes with new combinations of parental alleles.
البطاقة ٢٧٣
السؤال
What does recombination frequency estimate?
الإجابة
Relative distance between linked genes; higher frequency generally means greater separation, up to the 50% limit.
البطاقة ٢٧٤
السؤال
What happens to sister chromatids in meiosis II?
الإجابة
Their centromeres separate, and the chromatids move into different cells.
البطاقة ٢٧٥
السؤال
What rule finds the probability of either of two mutually exclusive outcomes?
الإجابة
Add their individual probabilities.
البطاقة ٢٧٦
السؤال
What is codominance?
الإجابة
Both alleles contribute distinct, detectable products or traits in the heterozygote.
البطاقة ٢٧٧
السؤال
How is a chi-square contribution calculated for one category?
الإجابة
Subtract expected from observed, square the difference, and divide by expected.
البطاقة ٢٧٨
السؤال
When do homologous chromosomes pair as tetrads?
الإجابة
During prophase I.
البطاقة ٢٧٩
السؤال
What rule finds the probability that independent events both occur?
الإجابة
Multiply their individual probabilities.
البطاقة ٢٨٠
السؤال
What is independent assortment?
الإجابة
Each homologous pair orients independently at metaphase I, producing many maternal–paternal chromosome combinations.
البطاقة ٢٨١
السؤال
Why can't recombination frequency exceed 50%?
الإجابة
At 50%, recombinant and parental combinations are equally common and the genes behave as if unlinked.
البطاقة ٢٨٢
السؤال
What aligns at the metaphase I plate?
الإجابة
Homologous pairs, with each homolog attached toward an opposite pole.
البطاقة ٢٨٣
السؤال
What is a test cross?
الإجابة
Crossing an individual with a dominant phenotype to a homozygous recessive individual to infer the unknown genotype.
البطاقة ٢٨٤
السؤال
How can one gene have multiple alleles?
الإجابة
More than two allele forms can exist in the population, although one diploid individual carries at most two.
البطاقة ٢٨٥
السؤال
How are total chi-square and category contributions related?
الإجابة
Total chi-square is the sum of all category contributions.
البطاقة ٢٨٦
السؤال
What separates during anaphase I?
الإجابة
Homologous chromosomes; sister chromatids remain joined.
البطاقة ٢٨٧
السؤال
How does random fertilization increase variation?
الإجابة
Any one genetically varied gamete from one parent can fuse with any compatible gamete from the other.
البطاقة ٢٨٨
السؤال
A test cross yields about half recessive offspring. What genotype is supported for the unknown parent?
الإجابة
Heterozygous.
البطاقة ٢٨٩
السؤال
What is nondisjunction?
الإجابة
Failure of homologous chromosomes or sister chromatids to separate normally.
البطاقة ٢٩٠
السؤال
What aligns during metaphase II?
الإجابة
Individual duplicated chromosomes in each haploid cell.
البطاقة ٢٩١
السؤال
What is polygenic inheritance?
الإجابة
Multiple genes contribute to one trait, often producing continuous phenotypic variation.
البطاقة ٢٩٢
السؤال
For a simple goodness-of-fit test, how are degrees of freedom found?
الإجابة
Number of categories minus one.
البطاقة ٢٩٣
السؤال
Which meiotic events create variation before fertilization?
الإجابة
Crossing over and independent assortment.
البطاقة ٢٩٤
السؤال
How does ploidy change during meiosis?
الإجابة
Homolog separation reduces diploid cells to haploid cells; meiosis II separates chromatids without another ploidy reduction.
البطاقة ٢٩٥
السؤال
What pedigree pattern often suggests a recessive trait?
الإجابة
Unaffected parents can have an affected child, if both parents carry the allele.
البطاقة ٢٩٦
السؤال
How can meiotic nondisjunction affect gametes?
الإجابة
It can produce gametes with an extra or missing chromosome.
البطاقة ٢٩٧
السؤال
What is pleiotropy?
الإجابة
One gene influences multiple phenotypic traits.
البطاقة ٢٩٨
السؤال
Why is there no second DNA replication before meiosis II?
الإجابة
The goal is to separate existing sister chromatids, not duplicate the genome again.
البطاقة ٢٩٩
السؤال
What does a p-value below the chosen threshold support?
الإجابة
Rejecting the null model because the observed deviation would be unlikely if that model were correct.
البطاقة ٣٠٠
السؤال
Why are siblings genetically different even with the same parents?
الإجابة
They inherit different allele combinations through crossing over, independent assortment, and random fertilization.
البطاقة ٣٠١
السؤال
Why do small families often deviate from expected Mendelian ratios?
الإجابة
Probability ratios describe long-run expectations; random sampling variation is large with few offspring.
البطاقة ٣٠٢
السؤال
A diploid cell has six chromosomes. How many chromosomes should each normal meiotic product have?
الإجابة
Three.
البطاقة ٣٠٣
السؤال
A trisomic zygote forms after fertilization. What meiotic error is a likely cause?
الإجابة
Nondisjunction produced a gamete carrying an extra copy of that chromosome.
البطاقة ٣٠٤
السؤال
Why can identical genotypes show different phenotypes?
الإجابة
Environmental conditions and developmental variation can alter gene expression or trait development.
البطاقة ٣٠٥
السؤال
What does failing to reject a genetic null hypothesis mean?
الإجابة
The data do not show a significant departure from the model; they do not prove the model true.
البطاقة ٣٠٦
السؤال
How do DNA and RNA sugars differ?
الإجابة
DNA contains deoxyribose; RNA contains ribose.
البطاقة ٣٠٧
السؤال
What does semiconservative DNA replication produce?
الإجابة
Each daughter DNA molecule contains one original strand and one newly synthesized strand.
البطاقة ٣٠٨
السؤال
What is transcription?
الإجابة
Synthesis of RNA using DNA as a template.
البطاقة ٣٠٩
السؤال
What is a point mutation?
الإجابة
A change affecting one nucleotide pair.
البطاقة ٣١٠
السؤال
What is an operon?
الإجابة
A group of prokaryotic genes controlled together and transcribed from one promoter.
البطاقة ٣١١
السؤال
Why can muscle and nerve cells differ despite having the same genome?
الإجابة
They express different sets and amounts of genes.
البطاقة ٣١٢
السؤال
What must a virus use from its host?
الإجابة
Host resources and at least some host-cell machinery to copy or express its genome and produce new particles.
البطاقة ٣١٣
السؤال
What does PCR do?
الإجابة
It amplifies a chosen DNA region through repeated cycles of strand separation, primer binding, and extension.
البطاقة ٣١٤
السؤال
What enzyme performs transcription?
الإجابة
RNA polymerase.
البطاقة ٣١٥
السؤال
What does helicase do during replication?
الإجابة
It unwinds the double helix and separates the template strands.
البطاقة ٣١٦
السؤال
How does a repressor reduce transcription?
الإجابة
It binds regulatory DNA and blocks or hinders transcription machinery.
البطاقة ٣١٧
السؤال
What is a silent mutation?
الإجابة
A nucleotide change that does not change the encoded amino acid.
البطاقة ٣١٨
السؤال
What does a promoter do?
الإجابة
It marks where transcription machinery assembles and helps set the transcription start and direction.
البطاقة ٣١٩
السؤال
What does topoisomerase do ahead of a replication fork?
الإجابة
It relieves twisting strain caused by DNA unwinding.
البطاقة ٣٢٠
السؤال
How does an inducer affect an inducible operon?
الإجابة
It disables the repressor or otherwise turns transcription on when the pathway's substrate is present.
البطاقة ٣٢١
السؤال
How do DNA and RNA bases differ?
الإجابة
DNA uses thymine, while RNA uses uracil; both also use adenine, cytosine, and guanine.
البطاقة ٣٢٢
السؤال
Which DNA strand does RNA polymerase read?
الإجابة
The template strand, read 3′→5′ while RNA is built 5′→3′.
البطاقة ٣٢٣
السؤال
Why is an RNA primer needed for DNA replication?
الإجابة
DNA polymerase can extend an existing 3′ end but cannot start a strand from nothing.
البطاقة ٣٢٤
السؤال
How does a corepressor affect a repressible operon?
الإجابة
It activates a repressor, turning off genes when the pathway's end product is abundant.
البطاقة ٣٢٥
السؤال
What is a missense mutation?
الإجابة
A nucleotide change that substitutes one amino acid for another.
البطاقة ٣٢٦
السؤال
How does an mRNA sequence relate to the coding DNA strand?
الإجابة
It matches the coding strand except RNA has uracil in place of thymine.
البطاقة ٣٢٧
السؤال
What does primase do?
الإجابة
It builds short RNA primers.
البطاقة ٣٢٨
السؤال
Why is the lac operon strongly expressed when lactose is present and glucose is scarce?
الإجابة
Lactose relieves repression, while low glucose supports positive activation of transcription.
البطاقة ٣٢٩
السؤال
Why are primers essential in PCR?
الإجابة
They define the target boundaries and provide 3′ ends for DNA polymerase.
البطاقة ٣٣٠
السؤال
What is the primary RNA transcript in a eukaryote?
الإجابة
The initial RNA copy before processing.
البطاقة ٣٣١
السؤال
In which direction does DNA polymerase synthesize DNA?
الإجابة
5′→3′ by adding nucleotides to a 3′ end.
البطاقة ٣٣٢
السؤال
Why is the trp operon usually off when tryptophan is abundant?
الإجابة
Tryptophan acts as a corepressor, enabling repression of biosynthetic genes.
البطاقة ٣٣٣
السؤال
What holds complementary DNA bases together?
الإجابة
Hydrogen bonds: adenine pairs with thymine, and cytosine pairs with guanine.
البطاقة ٣٣٤
السؤال
What happens during RNA splicing?
الإجابة
Introns are removed and exons are joined.
البطاقة ٣٣٥
السؤال
Why is the leading strand synthesized continuously?
الإجابة
Its template orientation lets polymerase follow the replication fork while synthesizing 5′→3′.
البطاقة ٣٣٦
السؤال
How can histone acetylation affect transcription?
الإجابة
It often loosens chromatin and makes DNA more accessible to transcription machinery.
البطاقة ٣٣٧
السؤال
What is a nonsense mutation?
الإجابة
A nucleotide change that creates a premature stop codon.
البطاقة ٣٣٨
السؤال
What do the 5′ cap and poly-A tail help do?
الإجابة
They protect eukaryotic mRNA and support export and translation.
البطاقة ٣٣٩
السؤال
Why is the lagging strand synthesized in fragments?
الإجابة
Its template orientation forces repeated 5′→3′ synthesis away from the moving fork.
البطاقة ٣٤٠
السؤال
How can DNA methylation near a promoter affect transcription?
الإجابة
It often reduces transcription by limiting access or recruiting repressive proteins.
البطاقة ٣٤١
السؤال
How does gel electrophoresis separate DNA fragments?
الإجابة
An electric field pulls negatively charged DNA through a matrix; smaller fragments usually travel farther.
البطاقة ٣٤٢
السؤال
How can alternative splicing increase protein diversity?
الإجابة
Different exon combinations from one transcript can produce different mRNAs and polypeptides.
البطاقة ٣٤٣
السؤال
What are Okazaki fragments?
الإجابة
Short DNA segments made on the lagging strand.
البطاقة ٣٤٤
السؤال
What does a transcription factor do?
الإجابة
It binds regulatory DNA and helps increase or decrease transcription of specific genes.
البطاقة ٣٤٥
السؤال
Why are DNA strands antiparallel?
الإجابة
Their sugar–phosphate backbones run in opposite 5′→3′ directions.
البطاقة ٣٤٦
السؤال
What is translation?
الإجابة
Ribosomes use an mRNA codon sequence to build a polypeptide.
البطاقة ٣٤٧
السؤال
What does DNA ligase do?
الإجابة
It seals breaks in the sugar–phosphate backbone, joining DNA fragments.
البطاقة ٣٤٨
السؤال
What is a frameshift mutation?
الإجابة
An insertion or deletion not in multiples of three that shifts downstream codon grouping.
البطاقة ٣٤٩
السؤال
How can an enhancer influence a distant promoter?
الإجابة
DNA looping brings enhancer-bound activators near the transcription machinery.
البطاقة ٣٥٠
السؤال
What does a codon specify?
الإجابة
An amino acid or a translation stop signal.
البطاقة ٣٥١
السؤال
What do restriction enzymes do?
الإجابة
They cut DNA at particular recognition sequences.
البطاقة ٣٥٢
السؤال
What gives a nucleic-acid strand its 5′ and 3′ ends?
الإجابة
The chemical groups on the sugar: a 5′ phosphate end and a 3′ hydroxyl end.
البطاقة ٣٥٣
السؤال
How does proofreading improve replication accuracy?
الإجابة
DNA polymerases detect and replace many incorrectly paired nucleotides.
البطاقة ٣٥٤
السؤال
What does a tRNA anticodon do?
الإجابة
It base-pairs with an mRNA codon so the attached amino acid is placed correctly.
البطاقة ٣٥٥
السؤال
Why can a promoter mutation affect protein amount?
الإجابة
It can change transcription-factor or RNA-polymerase binding and alter transcription rate.
البطاقة ٣٥٦
السؤال
How can microRNA reduce gene expression?
الإجابة
It base-pairs with target mRNA and promotes degradation or blocks translation.
البطاقة ٣٥٧
السؤال
What maintains a differentiated cell's identity?
الإجابة
Stable regulatory networks and chromatin states keep characteristic genes active or silent.
البطاقة ٣٥٨
السؤال
What are the ribosome's broad roles?
الإجابة
It positions mRNA and tRNAs and catalyzes peptide-bond formation.
البطاقة ٣٥٩
السؤال
How can an RNA virus generate genetic variation quickly?
الإجابة
Many viral RNA polymerases lack strong proofreading, so replication introduces mutations frequently.
البطاقة ٣٦٠
السؤال
What can bacterial transformation demonstrate?
الإجابة
Cells can take up external DNA and express a selectable or observable trait.
البطاقة ٣٦١
السؤال
Why is RNA usually more structurally varied than double-stranded DNA?
الإجابة
A single RNA strand can fold back on itself through internal base pairing.
البطاقة ٣٦٢
السؤال
What usually marks translation initiation?
الإجابة
A start codon positioned with an initiator tRNA and ribosomal subunits.
البطاقة ٣٦٣
السؤال
What problem do telomeres help solve?
الإجابة
They protect chromosome ends from losing essential genes during repeated linear-DNA replication.
البطاقة ٣٦٤
السؤال
Why can an intron splice-site mutation affect protein sequence?
الإجابة
Incorrect splicing can remove exon sequence or retain intron sequence in the mature mRNA.
البطاقة ٣٦٥
السؤال
How can protein degradation regulate a pathway quickly?
الإجابة
Destroying a key protein lowers its activity without waiting for transcription to change.
البطاقة ٣٦٦
السؤال
What happens at a stop codon?
الإجابة
A release factor ends translation and frees the polypeptide.
البطاقة ٣٦٧
السؤال
How can a signal change cell specialization?
الإجابة
It can activate transcription factors that launch a new gene-expression program.
البطاقة ٣٦٨
السؤال
What is a retrovirus's information flow?
الإجابة
Viral RNA is reverse-transcribed into DNA, which can integrate into the host genome.
البطاقة ٣٦٩
السؤال
What does DNA sequencing reveal directly?
الإجابة
The order of nucleotides in the analyzed DNA; biological effects require further interpretation.
البطاقة ٣٧٠
السؤال
Why is the genetic code called redundant?
الإجابة
More than one codon can specify the same amino acid.
البطاقة ٣٧١
السؤال
Where does nucleotide sequence store information?
الإجابة
The order of bases encodes information that can be copied, transcribed, or translated.
البطاقة ٣٧٢
السؤال
Why is replication called bidirectional?
الإجابة
Two forks usually move away from each origin in opposite directions.
البطاقة ٣٧٣
السؤال
Why doesn't every DNA mutation change phenotype?
الإجابة
It may occur outside a functional sequence, be silent, have a mild effect, or be masked by another allele or environment.
البطاقة ٣٧٤
السؤال
How does a free ribosome's product usually differ from a rough-ER ribosome's product?
الإجابة
Free ribosomes often make cytosolic proteins; ER-bound ribosomes make many secreted, membrane, and endomembrane proteins.
البطاقة ٣٧٥
السؤال
Why can one signal coordinate many genes?
الإجابة
A shared transcription regulator or signaling pathway can control multiple target promoters.
البطاقة ٣٧٦
السؤال
Why does cell specialization depend on selective gene expression rather than gene loss?
الإجابة
Most specialized cells retain the genome but use only the genes needed for their role.
البطاقة ٣٧٧
السؤال
Why are viruses not described as independently living cells?
الإجابة
They lack cellular metabolism and cannot reproduce without a host cell.
البطاقة ٣٧٨
السؤال
A coding DNA triplet is 5′-ATG-3′. What is the matching mRNA codon?
الإجابة
5′-AUG-3′.
البطاقة ٣٧٩
السؤال
A PCR band is absent. Why isn't gene absence the only explanation?
الإجابة
Poor DNA quality, wrong primers, inhibitors, or failed reaction conditions can also prevent amplification.
البطاقة ٣٨٠
السؤال
Why can protein function require steps after translation?
الإجابة
The polypeptide may need folding, cleavage, chemical modification, or assembly with other subunits.
البطاقة ٣٨١
السؤال
How do fossils support evolution?
الإجابة
They document organisms and transitions through time, including appearance, change, and extinction.
البطاقة ٣٨٢
السؤال
What conditions are required for natural selection?
الإجابة
Individuals vary, some variation is heritable, and variants differ in survival or reproductive success in that environment.
البطاقة ٣٨٣
السؤال
What is artificial selection?
الإجابة
Humans choose which organisms reproduce based on desired heritable traits.
البطاقة ٣٨٤
السؤال
What does an allele frequency measure?
الإجابة
The fraction of all copies of a gene in a population represented by one allele.
البطاقة ٣٨٥
السؤال
What does a node on a phylogenetic tree represent?
الإجابة
A common ancestor where descendant lineages diverge.
البطاقة ٣٨٦
السؤال
What is biological speciation?
الإجابة
Evolution of reproductive isolation between populations, producing independently evolving lineages.
البطاقة ٣٨٧
السؤال
What is extinction?
الإجابة
Permanent loss of a species when no living members remain.
البطاقة ٣٨٨
السؤال
A pesticide-treated population becomes mostly resistant. What evidence distinguishes selection from acclimation?
الإجابة
Resistance should be heritable and increase across generations through differential reproduction, not just appear temporarily in exposed individuals.
البطاقة ٣٨٩
السؤال
What changes during evolution by natural selection?
الإجابة
Allele frequencies in a population across generations.
البطاقة ٣٩٠
السؤال
For two alleles under Hardy–Weinberg notation, what does p + q equal?
الإجابة
1.
البطاقة ٣٩١
السؤال
What is a clade?
الإجابة
An ancestor and all of its descendants.
البطاقة ٣٩٢
السؤال
What does homologous anatomy suggest?
الإجابة
Similar underlying structures with different functions can indicate inheritance from a common ancestor.
البطاقة ٣٩٣
السؤال
Do individual organisms evolve by natural selection?
الإجابة
No. Individuals are selected; populations evolve as inherited variants change in frequency.
البطاقة ٣٩٤
السؤال
Under Hardy–Weinberg equilibrium, what does p² represent?
الإجابة
Expected frequency of one homozygous genotype.
البطاقة ٣٩٥
السؤال
What is a shared derived character?
الإجابة
A trait that evolved in a common ancestor and helps identify one of its descendant clades.
البطاقة ٣٩٦
السؤال
What is mutation's evolutionary role?
الإجابة
It creates new alleles, the ultimate source of new genetic variation.
البطاقة ٣٩٧
السؤال
What is biological fitness?
الإجابة
Relative contribution of viable, reproducing offspring to the next generation in a particular environment.
البطاقة ٣٩٨
السؤال
Under Hardy–Weinberg equilibrium, what does 2pq represent?
الإجابة
Expected frequency of heterozygotes.
البطاقة ٣٩٩
السؤال
Which two tips on a tree are most closely related?
الإجابة
Those sharing the most recent common ancestor, regardless of how close their names appear on the page.
البطاقة ٤٠٠
السؤال
What is a vestigial structure?
الإجابة
A reduced feature inherited from ancestors that has lost much or all of its earlier function.
البطاقة ٤٠١
السؤال
What is an adaptation?
الإجابة
A heritable trait that became common because it improved fitness in past environments.
البطاقة ٤٠٢
السؤال
Under Hardy–Weinberg equilibrium, what does q² represent?
الإجابة
Expected frequency of the other homozygous genotype.
البطاقة ٤٠٣
السؤال
How does recombination affect evolution?
الإجابة
It reshuffles existing alleles into new combinations but does not itself create new alleles.
البطاقة ٤٠٤
السؤال
Does rotating branches around a node change relationships?
الإجابة
No. The branching pattern stays the same.
البطاقة ٤٠٥
السؤال
Why isn't an adaptation always beneficial in every setting?
الإجابة
Fitness effects depend on the environment and can involve tradeoffs.
البطاقة ٤٠٦
السؤال
What are the Hardy–Weinberg assumptions?
الإجابة
A very large population, random mating, no mutation, no migration, and no natural selection at the locus.
البطاقة ٤٠٧
السؤال
How can embryological similarities support common ancestry?
الإجابة
Shared developmental patterns can reflect inherited developmental genes and pathways.
البطاقة ٤٠٨
السؤال
What is gene flow?
الإجابة
Movement of alleles between populations through migration and reproduction.
البطاقة ٤٠٩
السؤال
Does natural selection create needed mutations?
الإجابة
No. Mutations arise without regard to need; selection changes the frequencies of their inherited effects.
البطاقة ٤١٠
السؤال
Why is Hardy–Weinberg equilibrium useful?
الإجابة
It provides a null model for detecting or reasoning about evolutionary change.
البطاقة ٤١١
السؤال
Does left-to-right tip order show evolutionary progress?
الإجابة
No. Tip order is a drawing choice, not a ranking from primitive to advanced.
البطاقة ٤١٢
السؤال
What is allopatric speciation?
الإجابة
Geographic separation reduces gene flow, allowing populations to diverge.
البطاقة ٤١٣
السؤال
What is directional selection?
الإجابة
Selection favors one end of a phenotypic range, shifting the population mean.
البطاقة ٤١٤
السؤال
If q² = 0.09, what is q?
الإجابة
0.30.
البطاقة ٤١٥
السؤال
Why is DNA sequence similarity evidence for relatedness?
الإجابة
Related lineages inherit sequences from common ancestors, with differences accumulating over time.
البطاقة ٤١٦
السؤال
How does gene flow often affect differences between populations?
الإجابة
It tends to make allele frequencies more similar.
البطاقة ٤١٧
السؤال
What is stabilizing selection?
الإجابة
Selection favors intermediate phenotypes and removes extremes.
البطاقة ٤١٨
السؤال
If q = 0.30, what is p?
الإجابة
0.70.
البطاقة ٤١٩
السؤال
What can branch length mean?
الإجابة
Only what the figure defines—sometimes time or amount of change, and sometimes nothing quantitative.
البطاقة ٤٢٠
السؤال
What is sympatric speciation?
الإجابة
Reproductive isolation evolves without geographic separation, for example through polyploidy or strong niche and mating differences.
البطاقة ٤٢١
السؤال
What is disruptive selection?
الإجابة
Selection favors both extremes over intermediate phenotypes.
البطاقة ٤٢٢
السؤال
If p = 0.70 and q = 0.30, what is 2pq?
الإجابة
0.42.
البطاقة ٤٢٣
السؤال
Why include an untreated population in a selection experiment?
الإجابة
It shows how allele or trait frequencies change without the selective treatment.
البطاقة ٤٢٤
السؤال
Why is the nearly universal genetic code evidence of common ancestry?
الإجابة
A deeply conserved information system is most simply explained by inheritance from early shared ancestors.
البطاقة ٤٢٥
السؤال
What is balancing selection?
الإجابة
Natural selection that maintains two or more alleles in a population, such as through heterozygote advantage or selection that varies across environments.
البطاقة ٤٢٦
السؤال
What is genetic drift?
الإجابة
Random change in allele frequencies caused by chance sampling across generations.
البطاقة ٤٢٧
السؤال
If 16% of a Hardy–Weinberg population shows a recessive phenotype, what is q?
الإجابة
0.40, because q is the square root of 0.16.
البطاقة ٤٢٨
السؤال
Why use an outgroup in tree analysis?
الإجابة
It helps infer which character states are ancestral versus derived in the focal group.
البطاقة ٤٢٩
السؤال
What is a prezygotic barrier?
الإجابة
A barrier that prevents mating or fertilization.
البطاقة ٤٣٠
السؤال
Allele A rises from 0.20 to 0.45. Describe the evolutionary result.
الإجابة
The population evolved at that locus because allele frequency changed.
البطاقة ٤٣١
السؤال
How does biogeography support evolution?
الإجابة
Species distributions often match isolation history, dispersal, and descent from nearby ancestors.
البطاقة ٤٣٢
السؤال
What is sexual selection?
الإجابة
Differences in mating success drive changes in traits that affect mate attraction or competition.
البطاقة ٤٣٣
السؤال
When is genetic drift strongest?
الإجابة
In small populations.
البطاقة ٤٣٤
السؤال
Why can a rare recessive allele persist?
الإجابة
Selection cannot remove copies hidden in heterozygotes as efficiently as copies expressed in homozygotes.
البطاقة ٤٣٥
السؤال
How can molecular data revise a phylogenetic tree?
الإجابة
Sequence comparisons can reveal relationships not obvious from morphology or distinguish convergence from homology.
البطاقة ٤٣٦
السؤال
What is a postzygotic barrier?
الإجابة
A barrier that reduces hybrid survival, fertility, or later-generation success after fertilization.
البطاقة ٤٣٧
السؤال
How can rapid environmental change increase extinction risk?
الإجابة
Populations may lack enough suitable variation or time to adapt or move.
البطاقة ٤٣٨
السؤال
A small island population loses alleles after a storm. Which mechanism is most direct?
الإجابة
Genetic drift through a bottleneck.
البطاقة ٤٣٩
السؤال
What is convergent evolution?
الإجابة
Unrelated lineages independently evolve similar traits under similar selective pressures.
البطاقة ٤٤٠
السؤال
Why can antibiotic resistance spread rapidly?
الإجابة
Treatment strongly favors resistant variants already present or newly introduced, which leave more descendants.
البطاقة ٤٤١
السؤال
What is a bottleneck effect?
الإجابة
A sharp population reduction leaves a random, often less diverse sample of the original gene pool.
البطاقة ٤٤٢
السؤال
How do genotype counts yield allele frequency?
الإجابة
Count two copies from each homozygote and one from each heterozygote, then divide by twice the number of diploid individuals.
البطاقة ٤٤٣
السؤال
What is maximum parsimony in tree building?
الإجابة
Preferring the tree that requires the fewest evolutionary changes under the model.
البطاقة ٤٤٤
السؤال
How can different breeding times isolate populations?
الإجابة
Temporal isolation prevents individuals from mating even when they share a location.
البطاقة ٤٤٥
السؤال
Why can mass extinctions reshape evolution?
الإجابة
They remove many lineages and open ecological opportunities for survivors.
البطاقة ٤٤٦
السؤال
Two similar traits evolved on distant tree branches. What explanation should be evaluated?
الإجابة
Convergent evolution under similar selection, alongside the possibility of an incorrect tree or unrecognized homology.
البطاقة ٤٤٧
السؤال
Why are analogous structures weak evidence of close ancestry?
الإجابة
Their similar function may have evolved independently rather than from the same ancestral structure.
البطاقة ٤٤٨
السؤال
Why doesn't natural selection produce perfection?
الإجابة
It works with existing variation under tradeoffs, historical constraints, chance, and changing environments.
البطاقة ٤٤٩
السؤال
What is a founder effect?
الإجابة
A new population starts from a small, nonrepresentative sample of a source population.
البطاقة ٤٥٠
السؤال
Observed genotypes differ from Hardy–Weinberg expectations. What is supported?
الإجابة
At least one model assumption may not hold, or sampling error may matter; the deviation alone does not identify the cause.
البطاقة ٤٥١
السؤال
Why is a phylogenetic tree a hypothesis?
الإجابة
It is an evidence-based reconstruction that can change when new data or methods appear.
البطاقة ٤٥٢
السؤال
How can behavioral differences cause isolation?
الإجابة
Different courtship signals reduce mating between populations.
البطاقة ٤٥٣
السؤال
What evidence can test origin-of-life hypotheses?
الإجابة
Chemistry experiments, geological records, molecular comparisons, and plausible self-replicating or membrane-forming systems.
البطاقة ٤٥٤
السؤال
How should fitness be compared in an experiment?
الإجابة
Measure relative reproductive contribution, such as viable offspring, under the same environmental conditions.
البطاقة ٤٥٥
السؤال
What does the fossil record not provide?
الإجابة
A complete sample of every organism or every transitional population.
البطاقة ٤٥٦
السؤال
How can a neutral trait change in frequency?
الإجابة
Genetic drift can shift it by chance, especially in small populations.
البطاقة ٤٥٧
السؤال
How can drift reduce adaptive potential?
الإجابة
It can remove alleles and lower genetic diversity needed under future environmental change.
البطاقة ٤٥٨
السؤال
Why does a large population support Hardy–Weinberg stability?
الإجابة
Chance sampling has less effect on allele frequencies, reducing drift.
البطاقة ٤٥٩
السؤال
If A and B share a more recent node with each other than either shares with C, what does that mean?
الإجابة
A and B are sister taxa and share a more recent common ancestor with each other than with C.
البطاقة ٤٦٠
السؤال
What is adaptive radiation?
الإجابة
Rapid diversification of one ancestral lineage into species using different ecological roles.
البطاقة ٤٦١
السؤال
What can experiments producing organic molecules from simple chemicals show?
الإجابة
That some building blocks can form under modeled conditions; they do not recreate or prove the exact origin of life.
البطاقة ٤٦٢
السؤال
A correlation links beak size with survival. Why isn't causation settled?
الإجابة
Other traits or habitats may covary with beak size; controlled or multivariable evidence is needed.
البطاقة ٤٦٣
السؤال
Why does agreement among fossils, anatomy, and molecules strengthen an evolutionary claim?
الإجابة
Independent evidence types pointing to the same history make alternative explanations less plausible.
البطاقة ٤٦٤
السؤال
A drought favors deeper beaks. What must be measured to show selection?
الإجابة
Heritable beak variation and differences in survival or reproduction linked to beak depth.
البطاقة ٤٦٥
السؤال
Why can artificial selection produce unintended traits?
الإجابة
Selected genes may be linked to other alleles, and inbreeding can expose harmful recessive alleles.
البطاقة ٤٦٦
السؤال
What data are needed to test Hardy–Weinberg genotype expectations?
الإجابة
Population genotype counts or reliable genotype frequencies for the locus.
البطاقة ٤٦٧
السؤال
Why doesn't one living species count as the ancestor of another on a typical tree?
الإجابة
Living tips represent lineages that have both evolved since their shared ancestral lineage.
البطاقة ٤٦٨
السؤال
Why can reduced gene flow accelerate divergence?
الإجابة
Populations retain separate mutations, drift independently, and respond to different selective pressures.
البطاقة ٤٦٩
السؤال
Why are ribozymes relevant to early-life hypotheses?
الإجابة
RNA can both store information and catalyze reactions, offering a possible bridge before modern DNA–protein systems.
البطاقة ٤٧٠
السؤال
What makes an evolutionary argument strong?
الإجابة
A clear claim, relevant population-level evidence, and reasoning that connects inheritance and differential reproduction to the observed change.
البطاقة ٤٧١
السؤال
How can a directional response help an organism?
الإجابة
Moving toward resources or away from hazards can improve survival and reproduction.
البطاقة ٤٧٢
السؤال
What is a trophic level?
الإجابة
A feeding position in the flow of energy through an ecosystem.
البطاقة ٤٧٣
السؤال
What processes move carbon into and out of biological molecules?
الإجابة
Photosynthesis fixes carbon; respiration, decomposition, and combustion release carbon dioxide.
البطاقة ٤٧٤
السؤال
What does exponential population growth assume?
الإجابة
Resources are effectively unlimited and the per-capita growth rate stays constant.
البطاقة ٤٧٥
السؤال
What is a density-dependent limiting factor?
الإجابة
Its effect strengthens as population density rises, such as competition, disease, or predation.
البطاقة ٤٧٦
السؤال
What is a keystone species?
الإجابة
A species whose ecological effect is disproportionately large relative to its abundance.
البطاقة ٤٧٧
السؤال
What are three levels of biodiversity?
الإجابة
Genetic diversity, species diversity, and ecosystem diversity.
البطاقة ٤٧٨
السؤال
What is the independent variable in a fertilizer–algae experiment?
الإجابة
The fertilizer amount or nutrient concentration deliberately changed.
البطاقة ٤٧٩
السؤال
What shape represents exponential growth over time?
الإجابة
A J-shaped curve.
البطاقة ٤٨٠
السؤال
What do primary producers do?
الإجابة
They capture external energy and build organic molecules from inorganic carbon.
البطاقة ٤٨١
السؤال
What is a density-independent limiting factor?
الإجابة
Its effect is not primarily set by population density, such as a severe freeze or wildfire.
البطاقة ٤٨٢
السؤال
Why is nitrogen fixation necessary?
الإجابة
Most organisms cannot use atmospheric nitrogen gas directly, so it must be converted to biologically available compounds.
البطاقة ٤٨٣
السؤال
What does logistic growth add to the exponential model?
الإجابة
Growth slows as population size approaches carrying capacity.
البطاقة ٤٨٤
السؤال
What is gross primary productivity?
الإجابة
The total rate at which producers capture energy in organic matter.
البطاقة ٤٨٥
السؤال
What is competition?
الإجابة
An interaction in which organisms using the same limited resource reduce one another's access or fitness.
البطاقة ٤٨٦
السؤال
What is ecological succession?
الإجابة
Change in community composition after new habitat forms or a disturbance alters an existing community.
البطاقة ٤٨٧
السؤال
What shape represents ideal logistic growth?
الإجابة
An S-shaped curve.
البطاقة ٤٨٨
السؤال
What is net primary productivity?
الإجابة
Gross primary productivity minus producers' respiratory energy use.
البطاقة ٤٨٩
السؤال
Why does genetic diversity matter for conservation?
الإجابة
It increases the range of inherited responses available under disease or environmental change.
البطاقة ٤٩٠
السؤال
What organisms perform much biological nitrogen fixation?
الإجابة
Certain prokaryotes, including free-living and symbiotic bacteria.
البطاقة ٤٩١
السؤال
What is carrying capacity?
الإجابة
The population size an environment can sustain over time under current conditions.
البطاقة ٤٩٢
السؤال
Why is net primary productivity important to consumers?
الإجابة
It is the producer biomass and energy available for growth and the next trophic levels.
البطاقة ٤٩٣
السؤال
What is competitive exclusion?
الإجابة
Species with identical limiting-resource niches cannot coexist indefinitely under stable conditions.
البطاقة ٤٩٤
السؤال
How do primary and secondary succession differ?
الإجابة
Primary succession begins without developed soil; secondary succession begins where soil remains.
البطاقة ٤٩٥
السؤال
Why can carrying capacity change?
الإجابة
Resources, habitat, climate, competitors, disease, and disturbance can change.
البطاقة ٤٩٦
السؤال
Why does available energy decline up a food chain?
الإجابة
Organisms use much energy for metabolism and lose it as heat and waste rather than storing it as biomass.
البطاقة ٤٩٧
السؤال
What is an ecosystem service?
الإجابة
A benefit people receive from ecosystems, such as pollination, water purification, soil formation, or climate regulation.
البطاقة ٤٩٨
السؤال
What does nitrification do?
الإجابة
Microbes oxidize ammonium to nitrite and then nitrate.
البطاقة ٤٩٩
السؤال
What does per-capita growth rate measure?
الإجابة
Population change per individual per unit time.
البطاقة ٥٠٠
السؤال
What is ecological efficiency?
الإجابة
The percentage of energy or production transferred from one trophic level to the next.
البطاقة ٥٠١
السؤال
What is resource partitioning?
الإجابة
Competing species use different resources, places, or times, reducing direct overlap.
البطاقة ٥٠٢
السؤال
What is resilience in an ecosystem?
الإجابة
The ability to recover structure or function after disturbance.
البطاقة ٥٠٣
السؤال
How is population growth estimated from births, deaths, immigration, and emigration?
الإجابة
Births + immigration − deaths − emigration.
البطاقة ٥٠٤
السؤال
If producers store 10,000 kJ and primary consumers receive 10%, how much do they receive?
الإجابة
1,000 kJ.
البطاقة ٥٠٥
السؤال
How does habitat fragmentation affect populations?
الإجابة
It shrinks and isolates habitat, reducing movement and gene flow while increasing edge effects.
البطاقة ٥٠٦
السؤال
Why sample several sites within each habitat?
الإجابة
Replication captures spatial variation and reduces the chance that one unusual site drives the result.
البطاقة ٥٠٧
السؤال
A population grows from 200 to 230 in one year. What is its percent growth?
الإجابة
15%, because the increase of 30 divided by 200 is 0.15.
البطاقة ٥٠٨
السؤال
What is a circadian rhythm?
الإجابة
An internal roughly 24-hour cycle that environmental cues can reset.
البطاقة ٥٠٩
السؤال
Why are food webs more realistic than simple food chains?
الإجابة
Most species eat or are eaten by multiple species, creating connected pathways.
البطاقة ٥١٠
السؤال
What does denitrification do?
الإجابة
Microbes convert nitrate to nitrogen gases, returning nitrogen to the atmosphere.
البطاقة ٥١١
السؤال
What characterizes an r-selected life-history strategy?
الإجابة
Many offspring, early reproduction, and relatively low investment per offspring in variable environments.
البطاقة ٥١٢
السؤال
What is mutualism?
الإجابة
An interaction that benefits both species.
البطاقة ٥١٣
السؤال
What is resistance in an ecosystem?
الإجابة
The ability to remain relatively unchanged during disturbance.
البطاقة ٥١٤
السؤال
How can climate change shift species ranges?
الإجابة
Organisms track suitable temperature, moisture, seasons, or interacting species when movement is possible.
البطاقة ٥١٥
السؤال
What characterizes a K-selected life-history strategy?
الإجابة
Fewer offspring, later reproduction, and higher investment per offspring near carrying capacity.
البطاقة ٥١٦
السؤال
A population curve levels near 800. What does the model suggest?
الإجابة
About 800 is the carrying capacity under those measured conditions, not a permanent universal value.
البطاقة ٥١٧
السؤال
How can seasonal cues affect reproduction?
الإجابة
Changes such as day length can trigger hormonal and behavioral shifts timed to favorable conditions.
البطاقة ٥١٨
السؤال
What role do decomposers play?
الإجابة
They break down dead material and waste, returning nutrients to forms other organisms can use.
البطاقة ٥١٩
السؤال
Why can phosphorus limit ecosystems?
الإجابة
It is essential but often released slowly from rocks and lacks a large atmospheric gas phase.
البطاقة ٥٢٠
السؤال
What does a Type I survivorship curve show?
الإجابة
High survival through early and middle life, followed by a steep decline at older ages.
البطاقة ٥٢١
السؤال
What is commensalism?
الإجابة
One species benefits while the other has no clear benefit or harm.
البطاقة ٥٢٢
السؤال
Why can diversity improve ecosystem stability?
الإجابة
Multiple species or response types can keep functions going when one component declines.
البطاقة ٥٢٣
السؤال
Why can overharvesting destabilize a population?
الإجابة
Removal faster than replacement lowers abundance and can alter age structure or genetic diversity.
البطاقة ٥٢٤
السؤال
Predator and prey peaks alternate over time. What can the graph establish?
الإجابة
Their abundances covary with a lag; the graph alone cannot prove the predator caused every prey change.
البطاقة ٥٢٥
السؤال
What is acclimation?
الإجابة
A reversible phenotypic adjustment by an individual to an environmental change.
البطاقة ٥٢٦
السؤال
Does energy cycle through an ecosystem?
الإجابة
No. Energy flows through and is ultimately dissipated as heat; matter cycles.
البطاقة ٥٢٧
السؤال
How does the water cycle connect ecosystems?
الإجابة
Evaporation, transpiration, condensation, precipitation, runoff, and infiltration move water and dissolved materials.
البطاقة ٥٢٨
السؤال
What does a Type II survivorship curve show?
الإجابة
A roughly constant mortality risk across ages.
البطاقة ٥٢٩
السؤال
What is parasitism?
الإجابة
A parasite benefits while reducing its host's fitness.
البطاقة ٥٣٠
السؤال
What is an invasive species?
الإجابة
A nonnative species that spreads and causes ecological, economic, or human-health harm.
البطاقة ٥٣١
السؤال
How can a wildlife corridor help fragmented populations?
الإجابة
It supports movement, recolonization, and gene flow between habitat patches.
البطاقة ٥٣٢
السؤال
How should biodiversity be compared when sample effort differs?
الإجابة
Standardize sampling effort or use a method that accounts for unequal effort before comparing.
البطاقة ٥٣٣
السؤال
How does acclimation differ from adaptation?
الإجابة
Acclimation occurs within an individual; adaptation is an inherited population change across generations.
البطاقة ٥٣٤
السؤال
How can removal of a top predator affect lower trophic levels?
الإجابة
It can trigger a trophic cascade by changing prey abundance and the organisms prey consume.
البطاقة ٥٣٥
السؤال
Why can extra fertilizer cause low oxygen in water?
الإجابة
Nutrient enrichment drives algal growth; decomposition then consumes dissolved oxygen.
البطاقة ٥٣٦
السؤال
What does a Type III survivorship curve show?
الإجابة
High early mortality with much better survival among those reaching later stages.
البطاقة ٥٣٧
السؤال
How can predation maintain diversity?
الإجابة
A predator can prevent one strong competitor from dominating the community.
البطاقة ٥٣٨
السؤال
How can disturbance increase or decrease diversity?
الإجابة
Its effect depends on frequency and intensity; it may create habitat variety or eliminate sensitive species.
البطاقة ٥٣٩
السؤال
Why protect multiple habitats rather than one small reserve?
الإجابة
Different habitats, disturbances, and climate trajectories preserve more species and ecological options.
البطاقة ٥٤٠
السؤال
A restoration site gains species but not nutrient cycling. How should success be evaluated?
الإجابة
Use both composition and ecosystem-function measures; one metric alone gives an incomplete result.

A colorful biology collage links a cell, DNA helix, energy pathways, inherited variation, and an ecosystem.

٥٤٠ بطاقة

AP Biology Flashcards: Complete 8-Unit Course Review

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سيفتح تطبيق Flashcards لتبدأ الدراسة.

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AP Biology Flashcards: Complete 8-Unit Course Review

What the cards practice

Learning order

What still needs practice

Scope and provenance

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