vaccination the administration of treated microorganisms or material from a pathogen into humans or animals to induce an immune response (966) vagina the female reproductive organ that connects the outside of the body to the uterus and that receives sperm during reproduction (1053) valve a fold of membranes that controls the flow of a fluid (934) variable a factor that changes in an experiment in order to test a hypothesis (937) vas deferens a duct through which sperm move from the epididymis to the ejacula-tory duct at the base of the penis (plural, vasa deferentia) (848, 1050) vascular cambium in a plant, the lateral meristem that produces secondary xylem and phloem (586) vascular plant a plant that has has true roots, stems, and leaves and a vascular system composed of xylem and phloem which are specialized tissues that conduct materials from one part of the plant to another (564) vascular tissue the specialized conducting tissue that is found in higher plants and that is made up mostly of xylem and phloem (564) vector in biology, any agent, such as a plasmid or a virus, that can incorporate foreign DNA and transfer that DNA from one organism to another; an intermediate host that transfers a pathogen or a parasite to another organism (258, 489) vegetable a plant part that is used as food but that is not classified botanically as a fruit (547) vegetative propagation the growth of plants by some means of asexual reproduction (623) vegetative reproduction a type of asexual reproduction in which new plants grow from nonreproductive plant parts (623) vein in plants, a bundle of vascular tissue that transports fluids and nutrients; in animals, a vessel that carries blood to the heart (576, 600, 937) venation the arrangement of veins in a leaf (600)

vent in some animals, the body opening to which the cloaca is connected and through which wastes exit (807) ventral the lower or abdominal part of an organism (655)

ventricle one of the two large muscular chambers that pump blood out of the heart (933) vernalization in plants, the exposure of seeds or seedlings to a period of cold (642)

vertebra one of the 33 bones in the spinal column (backbone) (660, 779) vertebrate an animal that has a backbone; includes mammals, birds, reptiles, amphibians, and fish (651) vesicle a small cavity or sac that contains materials in a eukaryotic cell; forms when part of the cell membrane surrounds the materials to be taken into the cell or transported within the cell (105) vessel in plants, a tubelike structure in the xylem that is composed of connected cells that conduct water and mineral nutrients; in animals, a tube or duct that carries blood or another bodily fluid (585) vessel element in plants, one of the cellular components of a xylem vessel (585) vestigial structure a structure in an organism that is reduced in size and function and that may have been complete and functional in the organism's ancestors (306)

villus one of the many tiny projections from the cells in the lining of the small intestine; increases the surface area of the lining for absorption (plural, villi)

viper a venomous snake that has two large, mobile fangs at the front of the mouth (833) viroid an infectious agent that is made up of a short, circular, single strand of RNA that does not have a capsid; the smallest known particle that is able to replicate (494)

virulent describes a microorganism that causes disease and that is highly infectious; strictly, refers only to viruses that reproduce by the lytic cycle (193, 486) virus a nonliving, infectious particle composed of a nucleic acid and a protein coat; it can invade and destroy a cell (483) visceral mass the central section of a mol-lusk's body that contains the mollusk's organs (706) vitamin an organic compound that participates in biochemical reactions and that builds various molecules in the body; some vitamins are called coenzymes and activate specific enzymes (982) viviparity in amniotes, a reproductive method in which eggs that lack shells are produced and develop inside the body of the mother, who then gives birth to the offspring (829) viviparous an organism whose offspring develop within the mother's body and are born alive (863) voluntary muscle a muscle whose movement can be consciously controlled (917) vulva the external part of the female reproductive organs (1053)

w water cycle the continuous movement of water between the atmosphere, the land, and the oceans (371) water mold a funguslike protist that is composed of branching filaments of cells (514)

water vascular system a system of canals filled with a watery fluid that circulates throughout the body of an echinoderm (762)

wax a type of structural lipid consisting of a long fatty-acid chain that is joined to a long alcohol chain (60) weed undesirable plants that often crowd out crop plants or native plant species (556)

white blood cell a type of cell in the blood that destroys bacteria, viruses, and toxic proteins and helps the body develop immunities (941) withdrawal uncomfortable physical and psychological symptoms produced when a physically dependent drug user stops using drugs (1021) wood secondary xylem produced in gym-

nosperm and dicot stems (594) worker bee a bee that does not reproduce but that works for the community by collecting food and maintaining the hive (752)

Pregnancy And Childbirth

Pregnancy And Childbirth

If Pregnancy Is Something That Frightens You, It's Time To Convert Your Fear Into Joy. Ready To Give Birth To A Child? Is The New Status Hitting Your State Of Mind? Are You Still Scared To Undergo All The Pain That Your Best Friend Underwent Just A Few Days Back? Not Convinced With The Answers Given By The Experts?

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