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OpenStem
@openstem · Joined Jul 2026
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Flashcards10 cards
What is photoperiodism?1 / 10
Photoperiodism is a plant's physiological response to the relative length of day versus night. It lets a plant time major events — especially flowering — to the season.
Biology · L3 · Photoperiodism: Sensing Day Length
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Biology · L3 · Photoperiodism: Sensing Day LengthFlashcards10 cards
What is magnetoreception?1 / 10
The ability to sense Earth's magnetic field and use it as a directional compass or even a rough map of location.
Biology · L3 · Navigation Mechanisms in Migrating Animals
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Biology · L3 · Navigation Mechanisms in Migrating AnimalsFlashcards10 cards
What are homologous chromosomes?1 / 10
A matching pair of chromosomes — one inherited from each parent — that carry genes for the same traits at the same locations, though the specific versions (alleles) of those genes can differ. A human body cell has 23 such pairs.
Biology · L3 · Meiosis Vocabulary and Mechanics
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Biology · L3 · Meiosis Vocabulary and MechanicsFlashcards9 cards
How many daughter cells does one round of meiosis produce, compared to one round of mitosis?1 / 9
Meiosis produces four daughter cells from a single starting cell. Mitosis produces two daughter cells.
Biology · L3 · Meiosis vs. Mitosis and Genetic Variation
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Biology · L3 · Meiosis vs. Mitosis and Genetic VariationFlashcards9 cards
What are gibberellins, and what is their main effect on stem growth?1 / 9
Gibberellins are a group of plant hormones best known for promoting stem elongation — they stimulate cell division and cell elongation in stems, making plants grow taller. Plants that lack gibberellins, or can't respond to them, stay short and stubby.
Biology · L3 · Gibberellins and Ethylene
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Biology · L3 · Gibberellins and EthyleneFlashcards9 cards
What is the main role of cytokinins in plant growth?1 / 9
Cytokinins are plant hormones that promote cell division. Wherever cytokinin levels are high, plant tissue is stimulated to actively produce new cells, which is essential for growth in root tips, shoot tips, and developing fruit.
Biology · L3 · Cytokinins and Abscisic Acid
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Biology · L3 · Cytokinins and Abscisic AcidFlashcards9 cards
What is endocytosis?1 / 9
The process by which a cell takes material into itself by engulfing it: a patch of the plasma membrane folds inward (invaginates) around the material and pinches off, forming a vesicle inside the cytoplasm.
Biology · L3 · Endocytosis and Exocytosis Vocabulary
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Biology · L3 · Endocytosis and Exocytosis VocabularyFlashcards9 cards
How does a white blood cell use phagocytosis to fight infection?1 / 9
The white blood cell (such as a macrophage or neutrophil) extends its membrane around a bacterium, engulfing it inside a vesicle called a phagosome. The phagosome then fuses with a lysosome inside the cell, and digestive enzymes break down the trapped bacterium.
Biology · L3 · Bulk Transport in Action: Immunity, Cholesterol, and Signaling
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Biology · L3 · Bulk Transport in Action: Immunity, Cholesterol, and SignalingFlashcards10 cards
Before an antibiotic is ever used against a bacterial population, is there already variation among the bacteria?1 / 10
Yes. Random mutations happen constantly as bacteria reproduce, so even before any drug is introduced, a large population almost always contains a few cells that happen to carry traits — including ones that make them harder for a particular antibiotic to kill.
Biology · L3 · Natural Selection and Antibiotic Resistance
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Biology · L3 · Natural Selection and Antibiotic ResistanceFlashcards8 cards
What does MRSA stand for?1 / 8
Methicillin-resistant Staphylococcus aureus — a strain of a common bacterium that has evolved resistance to methicillin and many related antibiotics.
Biology · L3 · MRSA and Fighting Resistance at the Population Level
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Biology · L3 · MRSA and Fighting Resistance at the Population LevelFlashcards10 cards
Why do living things need nitrogen, and why is atmospheric N2 not directly usable?1 / 10
Nitrogen is a key building block of amino acids (and therefore proteins) and of the nucleotides that make up DNA and RNA. But atmospheric nitrogen gas (N2) is held together by an extremely strong triple bond, so it is chemically unreactive — most organisms have no way to break it apart and must instead absorb nitrogen already in a usable chemical form, such as ammonium or nitrate.
Biology · L3 · Nitrogen Cycle: Fixation to Assimilation
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Biology · L3 · Nitrogen Cycle: Fixation to AssimilationFlashcards9 cards
What is denitrification, and what does it convert?1 / 9
Denitrification is the conversion of nitrate (NO3−) back into nitrogen gas (N2), which is released into the atmosphere. It is carried out by denitrifying bacteria and completes the nitrogen cycle by returning fixed nitrogen to the same unreactive atmospheric form it started in.
Biology · L3 · Nitrogen Cycle: Denitrification and the Full Loop
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Biology · L3 · Nitrogen Cycle: Denitrification and the Full LoopFlashcards10 cards
What is a sensory receptor?1 / 10
A sensory receptor is a specialized cell or nerve ending that detects a specific type of stimulus — such as light, pressure, or a chemical — and converts it into a nerve signal the nervous system can process.
Biology · L3 · Classifying Receptors by Stimulus
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Biology · L3 · Classifying Receptors by StimulusFlashcards10 cards
How do mechanoreceptors inside the cochlea let you hear?1 / 10
Sound waves make fluid inside the cochlea vibrate, bending tiny hair cells that act as mechanoreceptors. That bending is transduction: it converts mechanical vibration into an electrical signal the auditory nerve carries to the brain.
Biology · L3 · Receptor Types in Action
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Biology · L3 · Receptor Types in ActionFlashcards10 cards
What is asexual reproduction?1 / 10
Asexual reproduction is a way of producing offspring from a single parent, with no mate needed. Because there is only one parent, the offspring are genetically identical (or nearly identical) copies of that parent — clones.
Biology · L3 · Asexual Reproduction Strategies
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Biology · L3 · Asexual Reproduction StrategiesFlashcards10 cards
What is sexual reproduction?1 / 10
Sexual reproduction is a way of producing offspring by combining genetic material from two parents, usually through the fusion of a sperm cell and an egg cell. The resulting offspring is a genetic mix of both parents, not a clone of either one.
Biology · L3 · Sexual Reproduction and the Variation Trade-Off
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Biology · L3 · Sexual Reproduction and the Variation Trade-OffFlashcards10 cards
What is an ecological pyramid?1 / 10
A diagram that represents some quantity at each of an ecosystem's trophic levels as a stack of bars, usually widest at the producer level on the bottom and narrowing toward the top consumers. Ecologists draw three different kinds, depending on what quantity is being graphed: energy, biomass, or number of organisms.
Biology · L3 · The Three Types of Ecological Pyramids
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Biology · L3 · The Three Types of Ecological PyramidsFlashcards10 cards
What is a population's 'standing crop'?1 / 10
The total biomass of a population present in an ecosystem at one specific moment, as if every individual could be weighed all at once. It is a snapshot, not a measure of how much biomass that population produces over time.
Biology · L3 · Why Pyramids Invert: The Phytoplankton Example
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Biology · L3 · Why Pyramids Invert: The Phytoplankton ExampleFlashcards10 cards
What is thigmotropism?1 / 10
Thigmotropism is a plant's growth response to touching a solid object. The name comes from the Greek thigma, meaning 'touch'. A pea plant's tendril curling around a fence wire is a classic example.
Biology · L3 · Thigmotropism: How Plants Respond to Touch
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Biology · L3 · Thigmotropism: How Plants Respond to TouchFlashcards10 cards
What is hydrotropism?1 / 10
Hydrotropism is the directional growth of a plant part, usually a root, toward a source of moisture in the soil. It helps roots find water even when that water is not directly below the seed.
Biology · L3 · Hydrotropism: Roots Growing Toward Water
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Biology · L3 · Hydrotropism: Roots Growing Toward WaterFlashcards10 cards
What is an ectotherm?1 / 10
An animal whose body temperature largely matches the temperature of its surroundings, because it does not generate significant heat of its own. Most reptiles, amphibians, fish, and invertebrates are ectotherms.
Biology · L3 · Ectotherms, Endotherms, and Heterotherms
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Biology · L3 · Ectotherms, Endotherms, and HeterothermsFlashcards9 cards
Roughly how much more food energy does an endotherm need compared to an ectotherm of the same body size?1 / 9
About five to ten times more. Generating heat metabolically around the clock is expensive, so a mouse-sized endotherm burns far more calories per day than a similarly sized lizard just to stay warm.
Biology · L3 · Energy Trade-offs of Thermoregulation
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Biology · L3 · Energy Trade-offs of ThermoregulationFlashcards10 cards
What is an allergen?1 / 10
An allergen is a normally harmless substance — such as pollen, peanut protein, pet dander, or dust mite droppings — that triggers an unnecessary immune response in someone who is allergic to it.
Biology · L3 · Allergies: The IgE-Histamine Pathway
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Biology · L3 · Allergies: The IgE-Histamine PathwayFlashcards10 cards
What is an autoimmune disease?1 / 10
An autoimmune disease is a condition in which the immune system fails to recognize some of the body's own healthy cells as "self" and mistakenly attacks them as if they were foreign invaders.
Biology · L3 · Autoimmune Disease: When the Body Attacks Itself
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Biology · L3 · Autoimmune Disease: When the Body Attacks ItselfFlashcards8 cards
What is transpiration, at the scale of a whole tree?1 / 8
Transpiration is the release of water vapor from a plant's leaves into the air, mostly through tiny pores called stomata. At the scale of a whole tree, it is a continuous, large-volume loss of water — not a trickle, but a flow measured in hundreds of liters a day for a large tree.
Biology · L3 · One Tree's Daily Water Budget
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Biology · L3 · One Tree's Daily Water BudgetFlashcards8 cards
What is an 'atmospheric river' or 'flying river' of moisture?1 / 8
It is a long, narrow band of concentrated water vapor moving through the atmosphere, carrying huge volumes of moisture over land — much like a river carries water over the ground, except this river flows through the sky and is fed largely by transpiration and evaporation.
Biology · L3 · Forests, Flying Rivers, and Regional Rainfall
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Biology · L3 · Forests, Flying Rivers, and Regional RainfallFlashcards10 cards
What is CRISPR-Cas9, in simple terms?1 / 10
CRISPR-Cas9 is a gene-editing tool that lets scientists cut DNA at a precise, chosen spot so they can edit it — much like using scissors to cut a document at an exact line so a mistake can be corrected.
Biology · L3 · CRISPR-Cas9: The Molecular Scissors
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Biology · L3 · CRISPR-Cas9: The Molecular ScissorsFlashcards10 cards
What is one medical application scientists are exploring with CRISPR?1 / 10
Potential treatments for genetic diseases — conditions caused by a faulty gene, such as sickle cell disease — by editing the gene responsible for the condition.
Biology · L3 · CRISPR in the Real World
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Biology · L3 · CRISPR in the Real WorldFlashcards6 cards
Define: guide RNA.1 / 6
A short RNA sequence that matches the target DNA and leads Cas9 to the exact spot to cut.
Biology · L3 · CRISPR Quick-Recall Vocabulary
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Biology · L3 · CRISPR Quick-Recall VocabularyFlashcards10 cards
What is a mass extinction?1 / 10
A mass extinction is a relatively short period of geologic time in which a very large share of Earth's species die out — far more, and far faster, than the normal, ongoing background rate of extinction.
Biology · L3 · The Big Five Mass Extinctions
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Biology · L3 · The Big Five Mass Extinctions