10Th Chem M

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machine a device that helps do work by either overcoming a force or changing the direction of the applied force

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machine

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macromolecule a very large organic molecule, usually a polymer, composed of hundreds or thousands of atoms

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macromolecule

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macronucleus in many protozoans, the larger of the two types of cell nuclei

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macronucleus

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macronutrient an element required in relatively large amounts

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macronutrient

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macrophage an immune system cell that engulfs pathogens and other materials

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macrophage

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madreporite the porous structure through which water enters and exits the water-vascular system of echinoderms

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madreporite

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maficdescribes magma or igneous rock that is rich in magnesium and iron and that is generally dark in color

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mafic

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magic numbers the numbers 2, 8, 20, 28, 50, 82, and 126 that represent the number of particles in an extrastable atomic nucleus that has completed shells of protons and neutrons

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magic numbers

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magma liquid rock produced under the Earth's surface; igneous rocks are made of magma

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magma

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magma chamberthe body of molten rock that feeds a volcano

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magma chamber

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magnet any material that attracts iron or materials containing iron

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magma chamber

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magnetic declination the difference between the magnetic north and the true north

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magnetic declination

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magnetic domaina region composed of a group of atoms whose magnetic fields are aligned in the same direction

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magnetic domain

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magnetic field a region where a magnetic force can be detected

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magnetic field

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magnetic forcethe force of attraction or repulsion generated by moving or spinning electric charges

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magnetic force

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magnetic pole one of two points, such as the ends of a magnet, that have opposing magnetic qualities

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magnetic pole

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magnetic quantum number the quantum number that corresponds to the alignment of the angular momentum component with a magnetic field

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magnetic quantum number

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magnetosphere a region of the space surrounding a planet where charged particles are controlled by the planet's magnetic field

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magnetosphere

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magnification the increase of an object's apparent size by using lenses or mirrors

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magnification

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magnitude a measure of the strength of an earthquake

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magnitude

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magnitudean element in the s-block or p-block of the periodic table

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magnitude

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main sequence the location on the H-R diagram where most stars lie; it has a diagonal pattern from the lower right (low temperature and luminosity) to the upper left (high temperature and luminosity)

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main sequence

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malaria an infectious tropical disease caused by a protozoan and transmitted to humans by a mosquito; it produces high fevers, chills, sweating, and anemia

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malaria

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malignant tumor a cancerous mass of cells

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malignant tumor

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malleability the ability of a substance to be hammered or beaten into a sheet

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malleability

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malnutrition a disorder of nutrition that results when a person does not consume enough of each of the nutrients that are needed by the human body

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malnutrition

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Malpighian tubule an excretory tube that opens into the back part of the intestine of most insects and certain arthropods

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Malpighian tubule

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mammary gland a gland that is located in the chest of a female mammal and that secretes milk

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mammary gland

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mandible a type of mouthpart found in some arthropods and used to pierce and suck food; the lower part of the jaw

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mandible

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mangrove swamp a tropical or subtropical marine swamp that is characterized by the abundance of low to tall trees, especially mangrove trees

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mangrove swamp

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mantle in biology, a layer of tissue that covers the body of many invertebrates

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mantle

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mantle in Earth science, the layer of rock between Earth's crust and core

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mantle

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mantle cavity the space between the mantle and body mass in mollusks and brachiopods

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mantle cavity

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map a representation of the Earth’s surface

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map

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map projection a flat map that represents a spherical surface

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map projection

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marea large, dark area of basalt on the moon (plural, maria)

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mare

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maria large, dark areas of basalt on the moon (singular, mare)

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maria

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marine describes an ecosystem in the sea

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marine

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an ecosystem in the sea

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marine ecosystem

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maritime polar a cold air mass that has high humidity as a result of passing over warmer water

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maritime polar

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maritime tropical a warm and humid air mass that typically forms over tropical oceans

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maritime tropical

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marsh a treeless wetland ecosystem where plants such as grasses grow

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marsh

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marsupial a mammal that does not have a placenta and that carries and nourishes its young in a pouch

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marsupial

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mass a measure of the amount of matter in an object; a fundamental property of an object that is not affected by the forces that act on the object, such as the gravitational force

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mass

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mass defect the difference between the mass of an atom and the sum of the masses of the atom's protons, neutrons, and electrons

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mass defect

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mass density the concentration of matter of an object, measured as the mass per unit volume of a substance

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mass density

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mass extinction an episode during which large numbers of species become extinct

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mass extinction

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mass movement the movement of a large mass of sediment or a section of land down a slope

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mass movement

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mass number the sum of the numbers of protons and neutrons in the nucleus of an atom

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mass number

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mastax the muscular pharynx in rotifers

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mastax

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mathematical model one or more equations that represent the way a system or process works

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mathematical model

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matter anything that has mass and takes up space

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matter

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maxilla a type of mouthpart found in most arthropods and located behind the mandible

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maxilla

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maxillaped a thoracic appendage in arthropods that is used to manipulate food and to detect touch and chemicals

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mean the number obtained by adding up the data for a given characteristic and dividing this sum by the number of individuals

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mean

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meander one of the bends, twists, or curves in a low-gradient stream or river

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meander

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mean sea level the average height of the sea surface over a 19-year period

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mean sea level

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measurement a determination of the dimensions of something using a standard unit

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measurement

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mechanical advantage a number that tells how many times a machine multiplies force; it can be calculated by dividing the output force by the input force

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mechanical advantage

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mechanical efficiency the ratio of output to input of energy or of power; it can be calculated by dividing work output by work input

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mechanical efficiency

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mechanical energy the amount of work an object can do because of the object's kinetic and potential energies

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mechanical energy

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mechanical wave a wave that requires a medium through which to travel

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mechanical wave

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mechanical weatheringthe process by which rocks break down into smaller pieces by physical means

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mechanical weathering

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medial moraine a ridge of unsorted glacial material in the middle of a glacier

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medial moraine

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medicineany drug that is used to cure, prevent, or treat illness or discomfort

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medicine

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Mediterranean climate a climate that has long, sunny, hot, and dry summers and rainy winters; found on the coasts and islands of the Mediterranean Sea and in Southern California

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Mediterranean climate

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medium a physical environment in which phenomena occur

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medium

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medulla the innermost portion of an organ, such as the kidney

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medulla

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medulla oblongata in fish, the posterior brain lobes that regulate the internal organs; in humans, the lower portion of the brain stem, which regulates circulation, respiration, and certain special senses

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medulla oblongata

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medusa a free-swimming, jellyfish-like, and often umbrella-shaped sexual stage in the life cycle of a cnidarian; also a jellyfish or a hydra

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medusa

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megagametophyte the female gametophyte of a heterosporus plant

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megagametophyte

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megasporangium a structure that produces megaspores

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megasporangium

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megaspore the larger of the two types of spores produced by heterosporous plants; develops into a female gametophyte

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megaspore

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megaspore mother cell a diploid cell that undergoes meiosis to produce four haploid megaspores

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megaspore mother cell

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meiosis a process in cell division during which the number of chromosomes decreases to half the original number by two divisions of the nucleus, which results in the production of sex cells (gametes or spores)

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meiosis

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melanin a pigment that helps determine skin color

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melanin

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melatonin a hormone that is produced by the pineal gland during the night and that helps regulate certain biorhythms, such as sleep patterns

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melatonin

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melting the change of state in which a solid becomes a liquid by adding heat or changing pressure

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melting

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melting point the temperature and pressure at which a solid becomes a liquid

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melting point

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meltwater water that forms when ice or snow melts, especially glacier ice

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meltwater

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membrane potential the difference in electric potential between the two sides of a cell membrane

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membrane potential

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memory B cella B cell that responds to an antigen more strongly when the body is reinfected with an antigen than it does during its first encounter with the antigen

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memory B cell

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memory cell an immune system B cell or T cell that does not respond the first time that it meets with an antigen or an invading cell but that recognizes and attacks the antigen or invading cell during subsequent infections

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memory cell

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meninges the three protective membranes that cover the brain and spinal cord

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meninges

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meniscus the curve at a liquid's surface by which one measures the volume of the liquid

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meninges

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menopause the termination of the menstrual cycle; occurs between the ages of 45 and 55

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menopause

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menstrual cycle the female reproductive cycle, characterized by a monthly change of the lining of the uterus and the discharge of blood

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menstrual cycle

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menstruation the discharge of blood and discarded tissue from the uterus during the menstrual cycle

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menstruation

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Mercalli scale a 12-step system used for measuring the intensity of an earthquake

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Mercalli scale

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Mercator projection a map projection that is made when the contents of the globe are moved onto a cylinder; the meridians appear as straight, parallel, and evenly spaced lines, and the parallels appear as straight, unevenly spaced lines perpendicular to the meridians

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Mercator projection

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meridian any semicircle that runs north and south around Earth from the geographic North Pole to the geographic South Pole; a line of longitude

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meridian

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meristem a region of undifferentiated plant cells that are capable of dividing and developing into specialized plant tissues

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meristem

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mesa a flat-topped hill that rises steeply from a surrounding plain

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mesa

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mesentery a membrane that attaches the small intestine to the abdominal wall

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mesentery

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mesoderm in an embryo, the middle layer of cells that gives rise to muscles, blood, and various systems

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mesoderm

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mesoglea in cnidarians, the jellylike material located between the ectoderm and the endoderm

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mesoglea

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mesopause the upper boundary of the mesosphere, marked by an increase in temperature

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mesopause

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mesophyll in leaves, the tissue between epidermal layers, where photosynthesis occurs

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mesophyll

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mesosphere literally, the "middle sphere"; the strong, lower part of the mantle between the asthenosphere and the outer core

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mesosphere

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mesospherethe coldest layer of the atmosphere, between the stratosphere and the thermosphere, in which temperature decreases as altitude increases

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mesosphere

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mesothorax the middle segment of an insect's thorax

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mesothorax

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Mesozoic era the geologic era that lasted from 251 million to 65.5 million years ago; also called the Age of Reptiles

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Mesozoic era

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metabolism the sum of all chemical processes that occur in an organism

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metabolism

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metal an element that is shiny and that conducts heat and electricity well

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metal

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metallic bond a bond formed by the attraction between positively charged metal ions and the electrons around them

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metallic bond

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metalloid elements that have properties of both metals and nonmetals; sometimes referred to as semiconductors

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metalloid

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metamorphic rock a rock that forms from other rocks as a result of intense heat, pressure, or chemical processes

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metamorphic rock

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metamorphism the process in which one type of rock changes into metamorphic rock because of chemical processes or changes in temperature and pressure

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metamorphism

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metamorphosis a phase in the life cycle of many animals during which a rapid change from the immature organism to the adult takes place; an example is the change from larva to adult in insects

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metamorphosis

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metamorphosisone of the stages of mitosis and meiosis, during which all of the chromosomes move to the cell's equator

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metamorphosis

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metathorax the third and most posterior segment of an insect's thorax

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metathorax

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meteor a bright streak of light that results when a meteoroid burns up in Earth's atmosphere

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meteor

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meteorite a meteoroid that reaches the Earth's surface without burning up completely

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meteorite

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meteoroid a relatively small, rocky body that travels through space

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meteoroid

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meteorology the scientific study of Earth's atmosphere, especially in relation to weather and climate

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meteorology

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meteor shower a phenomenon that occurs when a group of meteors burn up upon entering the Earth's atmosphere

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meteor shower

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meter the basic unit of length in the SI (symbol, m)

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meter

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methanogen a microorganism that produces methane gas

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methanogen

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microclimate the climate of a small area

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microclimate

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microfilament a fiber found inside eukaryotic cells that is composed mainly of the protein actin and that has a role in cell structure and movement

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microfilament

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micronucleus the smaller, reproductive nucleus found in some protozoans

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micronucleus

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micronutrient a chemical needed in very small amounts for plant growth, such as manganese, iron, and zinc

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micronutrient

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microprocessor a single semiconductor chip that controls and executes a microcomputer's instructions

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microprocessor

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micropyle the small opening in the wall of an ovule through which a pollen tube enters the ovule

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micropyle

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microscope an instrument that produces an enlarged image of an object

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microscope

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microsporangium the structure that produces microspores in plants that produce two types of spores

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microsporangium

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microspore the smaller of the two types of spores produced by most plants that develops into the male gametophyte

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microspore

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microtubule one of the small, tubular fibers composed of the protein tubulin that are found in the cytoplasm of eukaryotic cells, that compose the cytoskeleton, and that play a role in cell structure and movement

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microtubule

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microvillus a fingerlike projection from the surface of certain animal cells, such as the epithelial cells that line the intestine, that increases the cell's surface area for absorption

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microvillus

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mid-Atlantic ridge a long and steep elevation of the sea floor that extends from north to south in the Atlantic Ocean

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mid-Atlantic ridge

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midbrain the section of the brain stem that is between the thalamus and the pons

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midbrain

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middle ear the part of the ear that is between the eardrum and the cochlea; contains the hammer, anvil, and stirrup

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middle ear

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middle-latitude climatea climate that has a maximum average temperature of 8°C in the coldest month and a minimum average temperature of 10°C in the warmest month

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middle-latitude climate

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midgut the main digestive cavity of some invertebrates

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midgut

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mid-latitude cyclonean area of low pressure that is characterized by rotating wind that moves toward the rising air of the central low-pressure region; the motion is counterclockwise in the Northern Hemisphere

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mid-latitude cyclone

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mid-ocean ridge a long, undersea mountain chain that has a steep, narrow valley at its center, that forms as magma rises from the asthenosphere, and that creates new oceanic lithosphere (sea floor) as tectonic plates move apart

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mid-ocean ridge

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migrate to move from one place to another when the seasons change

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migrate

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migration in general, any movement of individuals or populations from one location to another; specifically, a periodic group movement that is characteristic of a given population or species

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migration

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Milankovitch cyclescyclical changes in Earth's orbit and in the tilt of Earth's axis that occur over thousands of years and are thought to cause climatic changes

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Milankovitch cycles

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Milankovitch theory the theory that cyclical changes in Earth's orbit and in the tilt of Earth's axis occur over thousands of years and cause climatic changes

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Milankovitch theory

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millimeter of mercury a unit of pressure

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millimeter of mercury

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mimicry a defense in which one organism resembles another that is dangerous or poisonous

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mimicry

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mineral a natural, usually inorganic solid that has a characteristic chemical composition, an orderly internal structure, and a characteristic set of physical properties

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mineral

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mineralogist a person who examines, analyzes, and classifies minerals

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mineralogist

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mineral resources the valuable mineral deposits of a region

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mineral resources

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miscible describes two or more liquids that can dissolve into each other in various proportions

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miscible

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mistral a strong, cold, northern wind that blows down the Alps toward the Mediterranean Sea

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mistral

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mitochondrial matrix the fluid that is inside the inner membrane of a mitochondrion

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mitochondrial matrix

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mitochondrion in eukaryotic cells, the cell organelle that is surrounded by two membranes and that is the site of cellular respiration, which produces ATP

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mitochondrion

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mitosis in eukaryotic cells, a process of cell division that forms two new nuclei, each of which has the same number of chromosomes

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mitosis

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mitotic spindle a group of microtubules that forms during mitosis and separates the chromatids during nuclear division

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mitotic spindle

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mitral valve one of the four valves of the heart that is located between the left atrium and the left ventricle

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mitral valve

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mixture a combination of two or more substances that are not chemically combined

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mixture

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mitotic spindle a pattern, plan, representation, or description designed to show the structure or workings of an object, system, or concept

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mitotic spindle

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moderator a material that slows the velocity of neutrons so that they may be absorbed by the nuclei

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moderator

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modulate to change a wave's amplitude or frequency in order to send a signal

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modulate

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Moho the Mohorovicic discontinuity, which is the boundary between the Earth's crust and mantle where the speed of seismic waves suddenly changes

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Moho

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Mohs hardness scale the standard scale against which the hardness of minerals is rated

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Mohs hardness scale

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molal boiling-point constant a quantity calculated to represent the boiling-point elevation of a 1-molal solution of a nonvolatile, nonelectrolyte solution

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molal boiling-point constant

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molal freezing-point constant a quantity calculated to represent the freezing-point depression of a 1-molal solution of a nonvolatile, nonelectrolyte solute

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molal freezing-point constant

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molality the concentration of a solution expressed in moles of solute per kilogram of solvent

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molality

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molar a large tooth that is located in the back of the mouth and that is used to grind and crush food

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molar

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molarity a concentration unit of a solution expressed as moles of solute dissolved per liter of solution

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molarity

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molar mass the mass in grams of 1 mol of a substance

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molar mass

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mold in biology, a fungus that looks like wool or cotton

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mold

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mold in geology, a mark or cavity made in a sedimentary surface by a shell or other body

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mold

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mole the SI base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms of carbon in exactly12 g of carbon-12

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mole

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molecular formula a chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms

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molecular formula

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molecular genetics the study of the structure of nucleic acids and the function and regulation of genes

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molecular genetics

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molecule a group of atoms that are held together by chemical forces; a molecule is the smallest unit of matter that can exist by itself and retain all of a substance's chemical properties

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molecule

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mole ratio the relative number of moles of the substances required to produce a given amount of product in a chemical reaction

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mole ratio

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mollusk an invertebrate that has a soft, bilaterally symmetrical body that is often enclosed in a hard shell made of calcium carbonate; examples include snails, clams, octopuses, and squids

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mollusk

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molting the shedding of an exoskeleton, skin, feathers, or hair to be replaced by new parts

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molting

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moment of inertia the tendency of a body that is rotating about a fixed axis to resist a change in this rotating motion

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moment of inertia

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momentum a quantity defined as the product of the mass and velocity of an object

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momentum

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monadnock an isolated hill of rock that has resisted erosion

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monadnock

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monatomic ion an ion that formed from a single atom

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monatomic ion

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monocline a fold in rock layers in which the layers are horizontal on both sides of the fold

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monocline

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monocotamonocotyledonous plant; a plant that produces seeds that have only one cotyledon

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monocot

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monohybrid cross a cross between individuals that involves one pair of contrasting traits

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monohybrid cross

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monomer a simple molecule that can combine with other like or unlike molecules to make a polymer

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monomer

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an acid that can donate only one proton to a base

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monoprotic acid

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monosaccharide a simple sugar that is the basic subunit of a carbohydrate

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monosaccharide

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monosomy a condition in a diploid cell in which one member of a pair of homologous chromosomes is missing

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monosomy

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monotreme a mammal that lays eggs

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monotreme

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monsoon a seasonal wind that blows toward the land in the summer, bringing heavy rains, and that blows away from the land in the winter, bringing dry weather

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monsoon

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month a division of the year that is based on the orbit of the moon around the Earth

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month

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moon a body that revolves around a planet and that has less mass than the planet does

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moon

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morainea landform that is made from unsorted sediments deposited by a glacier

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moraine

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morphogenesis the development of shape in cells, tissues, or the entire embryo

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morphogenesis

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morphology the study of the structure and form of an organism

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morphology

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mortality rate the number of deaths that occur in a given period of time

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mortality rate

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morula a ball of cells that is produced by cleavage of the zygote

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morula

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motion an object’s change in position relative to a reference point

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motion

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motor neuron a nerve cell that conducts nerve impulses from the central nervous system to the muscles and glands

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motor neuron

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mountain range a series of mountains that are closely related in orientation, age, and mode of formation

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mountain range

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M phase the phase of the cell cycle in which the nucleus divides by mitosis

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M phase

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mRNA messenger RNA, a single-stranded RNA molecule that encodes the information to make a protein

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mRNA

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Muav Limestone a rock layer of the Grand Canyon that was deposited during the Cambrian period

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Muav Limestone

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the layer of epithelial tissue that covers internal surfaces of the body and that secretes mucus

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mucous membrane

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mucus the thick, slimy fluid that is secreted by mucous membranes and glands

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mucus

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mud a wet mixture of fine particles of clay and silt

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mud

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mudflow the flow of a mass of mud or rock and soil mixed with a large amount of water

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mudflow

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mud pots a hot spring that discharges boiling mud

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mud pots

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multicellular describes a tissue, organ, or organism that is made of many cells

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multicellular

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multinucleate describes a cell that has more than one nucleus

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multinucleate

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multiple alleles more than two alleles (versions of the gene) for a genetic trait

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multiple alleles

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multiple bond a bond in which the atoms share more than one pair of electrons, such as a double bond or a triple bond

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multiple bond

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municipal solidwastewaste produced by households and businesses

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municipal solid waste

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muscle fiber a multinucleate muscle cell, especially of skeletal or cardiac muscle tissue

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muscle fiber

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muscle tissue the tissue made of cells that can contract and relax to produce movement

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muscle tissue

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muscular system a collection of muscles whose primary function is movement and flexibility

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muscular system

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mutagen a physical or chemical agent that can damage or cause changes (mutations) in DNA

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mutagen

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mutation a change in the nucleotide-base sequence of a gene or DNA molecule

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mutation

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mutual inductance the ability of one circuit to induce an electromotive force in a nearby circuit in the presence of a changing current

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mutual inductance

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mutualism a relationship between two species in which both species benefit

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mutualism

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mycelium the mass of fungal filaments, or hyphae, that forms the body of a fungus

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mycelium

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myceliumthe study of fungi

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mycelium

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mycorrhiza a symbiotic association between fungi and plant roots

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mycorrhiza

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myelin sheath a layer of fatty material that surrounds certain nerve fibers and that acts as an electrical insulator

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myelin sheath

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myofibril a fiber that is found in striated muscle cells and that is responsible for muscle contraction

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myofibril

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myosin the most abundant protein in muscle tissue and the main constituent of the thick filaments of muscle fibers

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myosin

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myriapod an arthropod that has more than three pairs of legs

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myriapod