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130 Cards in this Set

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  • Back
labia liplike structures, usually referring to fleshy folds located on a female's pubis and at the opening of the vagina
labium an insect mouthpart that functions as a lower lip
labor the process by which the fetus and the placenta come out of the uterus
labrum the upper lip of arthropods
laccolith a body of igneous rock in the shape of a lens that penetrates a layer of sedimentary rocks and produces a structure that has a domed roof and a flat floor
lac operon a gene system whose operator gene and three structural genes control lactose metabolism in E. coli
lac operon
lacteal a tiny lymphatic vessel that absorbs the products of lipid digestion in the villi of the small intestine
the chemical breakdown of carbohydrates that produces lactic acid as the main end product
lactic acid fermentation
lagoon a small body of water separated from the sea by a low, narrow strip of land
landfill an area of land or an excavation where wastes are placed for permanent disposal
landform a physical feature of Earth's surface
landslide the sudden movement of rock and soil down a slope
land-use planning a set of policies and activities related to potential uses of land that is put in place before an area is developed
land-use planning
La Niña the cool phase of the El Niño–Southern Oscillation; a periodic occurrence in the eastern Pacific Ocean in which the surface-water temperature becomes unusually cool
La Niña
lanthanide a member of the rare-earth series of elements, whose atomic numbers range from 58 (cerium) to 71 (lutetium)
lapillus pyroclastic particles between 2 mm and 64 mm in diameter that erupt from a volcano
large intestine the broader and shorter portion of the intestine, where water is removed from the mostly digested food to turn the waste into semisolid feces, or stool
large intestine
larva an independent and immature form of an organism that is morphologically different from the adult form
larynx the area of the throat that contains the vocal cords and produces vocal sounds
laser a device that produces intense light of only one wavelength and color
latent heat the heat energy that is absorbed or released by a substance during a phase change
latent heat
lateral line a faint line visible on both sides of a fish’s body that runs the length of the body and marks the location of sense organs that detect vibrations in water
lateral line
lateral meristem dividing tissue that runs parallel to the long axis of a stem or a root
lateral meristem
lateral meristem an accumulation of rock fragments deposited along the sides of a valley glacier
lateral meristem
laterite a soil residue that is produced because of erosion in tropical climates
the distance north or south from the equator; expressed in degrees
lattice energy the energy associated with constructing a crystal lattice relative to the energy of all constituent atoms separated by infinite distances
lattice energy
the northern landmass that supposedly fragmented millions of years ago to form North America, Greenland, and Eurasia
lava magma that flows onto Earth’s surface; the rock that forms when lava cools and solidifies
lava plateau a wide, flat landform that results from repeated non explosive eruptions of lava that spread over a large area
lava plateau
law a descriptive statement or equation that reliably predicts events under certain conditions
law of conservation of energy the law that states that energy cannot be created or destroyed but can be changed from one form to another
law of conservation of energy
law of conservation of mass the law that states that mass cannot be created or destroyed in ordinary chemical and physical changes
law of conservation of mass
law of crosscutting relationships the principle that a fault or body of rock is younger than any other body of rock that it cuts through
law of crosscutting relationships
law of definite proportions the law that states that a chemical compound always contains the same elements in exactly the same proportions by weight or mass
law of definite proportions
law of electric chargesthe law that states that like charges repel and opposite charges attract
law of electric charges
law of gravitation the law that states that the force of attraction between two objects depends on the masses of the objects and the distance between the objects
law of gravitation
law of independent assortment the law that states that genes separate independently of one another in meiosis
law of independent assortment
law of multipleproportions the law that states that when two elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other is in the ratio of small whole numbers
law of multiple proportions
law of reflection the law that states that the angle of incidence is equal to the angle of reflection
law of reflection
Mende's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete
law of segregation
law of superposition the principle that a sedimentary rock layer is older than the layers above it and younger than the layers below it if the layers are not disturbed
law of superposition
law of supply and demand a law of economics that states that as the demand for a good or service increases, the value of the good or service also increases
law of supply and demand
layering the formation of plant roots from stems or branches that are covered with soil
leachate a liquid that has passed through solid waste and has extracted dissolved or suspended materials from that waste, such as pesticides in the soil
leaching the removal of soluble substances from rock, ore, or layers of soil due to the passing of water
leaflet one segment of a compound leaf
leap year a year in which an extra day is added to the calendar and that occurs every four years
leap year
learned behavior a behavior that has been learned from experience
learned behavior
learning the development of behaviors through experience or practice
countries that have been identified by the United Nations as showing the fewest signs of development in terms of income, human resources, and economic diversification
least developed countries
Le Chatelier's principlethe principle that states that a system in equilibrium will oppose a change in a way that helps eliminate the change
Le Chatelier's principle
legend a list of map symbols and their meanings
legume any plant of the family Leguminosae (Fabaceae), such as a bean, pea, or lentil; the name for the type of fruit produced by members of this family
lengtha measure of the straight-line distance between two points
lens a transparent object that refracts light waves such that they converge or diverge to create an image
lens a convex transparent structure in the eye that focuses light on the retina
lethal dose the minimum amount of a substance that causes death
lethal dose
lethal mutation a gene or chromosomal mutation that influences the development of an organism in such a way that the organism cannot survive
lethal mutation
leukemia a progressive, malignant disease of the blood-forming organs
leukocyte a white blood cell
lever a simple machine that consists of a bar that pivots at a fixed point called a fulcrum; types include first-class, second-class and third-class levers
lever arm the perpendicular distance from the axis of rotation to a line drawn along the direction of the force
lever arm
Lewis acid an atom, ion, or molecule that accepts a pair of electrons
Lewis acid
Lewis base an atom, ion, or molecule that donates a pair of electrons
Lewis base
Lewis structure a structural formula in which electrons are represented by dots; dot pairs or dashes between two atomic symbols represent pairs in covalent bonds
Lewis structure
a mass of fungal and algal cells that grow together in a symbiotic relationship and that are usually found on rocks or trees
life cycle all of the events in the growth and development of an organism until the organism reaches sexual maturity
life cycle
life cyclethe average length of time that an individual is expected to live
life cycle
the study of living things
life science
lift an upward force on an object that moves in a fluid; lift depends on the fluid's density and velocity and on the object's surface area
ligament a type of tissue that holds together the bones in a joint
light microscope a microscope that uses a beam of visible light passing through one or more lenses to magnify an object
light microscope
lightning an electric discharge that takes place between two oppositely charged surfaces, such as between a cloud and the ground, between two clouds, or between two parts of the same cloud
light raya line in space that matches the direction of the flow of radiant energy
light ray
light reactions the initial reactions in photosynthesis, which are triggered by the absorption of light by photosystems I and II and include the passage of electrons along the electron transport chains, the production of NADPH and oxygen gas, and the synthesis of ATP through chemiosmosis
light reactions
light-year the distance that light travels in one year; about 9.46 trillion kilometers
lignite a brown coal
limbic system the portions of the central nervous system that are associated with emotions such as pleasure, fear, and happiness
limbic system
limiting factor an environmental factor that prevents an organism or population from reaching its full potential of distribution or activity
limiting factor
limiting reactant the substance that controls the quantity of product that can form in a chemical reaction
limiting reactant
limiting resources a particular natural resource that, when limited, determines the carrying capacity of an ecosystem for a particular species
limiting resources
limnetic zone the area in a freshwater habitat that is away from the shore but still close to the surface
limnetic zone
linear polarization the amplitude of an electric field that vibrates in a line perpendicular to the direction of the ray of light
linear polarization
line-emission spectrum a diagram or graph that indicates the degree to which a substance emits radiant energy with respect to wavelength
line-emission spectrum
linkage group a group of genes that are located on the same chromosome
linkage group
lipase an enzyme that breaks down fat molecules into fatty acids and glycerol
lipid a type of biochemical that does not dissolve in water, including fats and steroids; lipids store energy and make up cell membranes
lipid bilayer the basic structure of a biological membrane, composed of two layers of phospholipids
lipid bilayer
liquid the state of matter that has a definite volume but not a definite shape
lithosphere the solid, outer layer of Earth that consists of the crust and the rigid upper part of the mantle
littoral zone a shallow zone in a freshwater habitat where light reaches the bottom and nurtures plants
littoral zone
liver the largest organ in the body; it produces bile, stores and filters blood, and converts sugars into glycogen
livestock domesticated animals that are raised to be used on a farm or ranch or to be sold for profit
load the materials carried by a stream
load the mass of rock overlying a geological structure
load a device that uses electrical energy to do work
lobbying an attempt to influence the decisions of lawmakers
lobe-finned fish a fish that has fins whose fleshy bases look like limbs
lobe-finned fish
lode a mineral deposit within a rock formation
loess fine-grained sediments of quartz, feldspar, hornblende, mica, and clay deposited by the wind
logistic growth population growth that starts with a minimum number of individuals and reaches a maximum depending on the carrying capacity of the region; described by an S-shaped curve
logistic growth
logistic model a model of population growth that assumes that finite resource levels limit population growth
logistic model
the intermolecular attraction resulting from the uneven distribution of electrons and the creation of temporary dipoles
London dispersion force
long-day plant a plant that requires a period of exposure to light that exceeds a critical length to blossom
long-day plant
longitude the angular distance east or west from the prime meridian; expressed in degrees
longitudinal wave a wave in which the particles of the medium vibrate parallel to the direction of wave motion
longitudinal wave
long-period comet a comet that has an orbital period of more than 200 years
long-period comet
longshore current a water current that travels near and parallel to the shoreline
longshore current
in the kidney, the long, U-shaped part of a nephron that reabsorbs water and salts from the urine collected by the glomerulus
loop of Henle definite
loudness the extent to which a sound can be heard
low Earth orbit an orbit located below 3,000 km above the Earth's surface (abbreviation, LEO)
low Earth orbit
low-input farming farming that does not use a lot of energy, pesticides, fertilizer, or water
low-input farming
luminous describes objects that produce visible light
lunar cycle the orbit of the moon around the Earth, during which all of the lunar phases occur
lunar cycle
lunar eclipsethe passing of the moon through the Earth's shadow at full moon
lunar eclipse
lunar phases the different appearances of the moon from Earth throughout the month
lunar phases
lung the central organ of the respiratory system in which oxygen from the air is exchanged with carbon dioxide from the blood
luster the way in which a mineral reflects light
luteal phase the menstrual stage in which the corpus luteum develops
luteal phase
luteinizing hormone a hormone that stimulates ovulation and progesterone secretion by the corpus luteum in the female and testosterone secretion in the male (abbreviation, LH)
luteinizing hormone
the fluid that is collected by the lymphatic vessels and nodes
lymph lymphatic system
lymphatic system a collection of organs whose primary function is to collect extracellular fluid and return it to the blood; the organs in this system include the lymph nodes and the lymphatic vessels
lymphatic system
lymph node an organ that filters lymph and that is found along the lymphatic vessels
lymph node
lymphocyte a type of white blood cell that exists in two primary forms, T cells and B cells
lymphoma a tumor in the lymphoid tissues
lysis the disintegration of a cell by disruption of the plasma membrane
lysogenic describes viral replication in which a viral genome is replicated as a provirus without destroying the host cell
lysosome a cell organelle that contains digestive enzymes
lytic ldescribes viral replication that results in the destruction of a host cell and the release of many new virus particles