SAT词汇：以N开头的生物专业词汇

2016-01-22 14:22:39来源：新东方在线论坛　

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SAT考试阅读中的常考词汇有哪些？新东方在线为大家准备了SAT词汇：以N开头的生物专业词汇，希望能够帮助到正在准备SAT考试的考生。　　

NADH

　　An energy-carrying coenzyme produced by glycolysis and the Krebs cycle. NADH carries energy to the electron transport chain, where it is stored in ATP.

　　natural selection(自然选择)

　　The theory, first proposed by Darwin, which holds that organisms produce as many offspring as possible, which compete for limited resources. Organisms’ characteristics vary, and certain characteristics will allow organisms to survive and reproduce more effectively. These adaptive characteristics will be more prevalent in subsequent generations. Natural selection is the engine of evolution, choosing the most fit genes to pass from one generation to the next.

　　Nephridium(肾管)

　　A blood filtration and excretory organ characteristic of segmented worms.

　　Nephron(肾单位) ：肾的解剖与功能单位,包括肾小球等

　　Tiny, tubule structures responsible for the filtering of blood in the kidneys of vertebrates.

　　neritic zone(浅海水层)

　　The medium depth zone of the marine biome. Extends to 600 feet beneath the water’s surface and sits on the continental shelf, hundreds of miles from any shore. Algae, crustaceans, and fish inhabit this region.

　　nervous system(神经系统)

　　Control system of the body that functions by sending impulses through neurons to receive information and spur muscles to action.

　　Neuron(神经元)

　　The functional unit of the nervous system. A neuron is a specialized cell able to carry an action potential and made up of dendrites, a cell body, and an axon. There are three types of neurons: sensory, motor, and interneurons.

　　Niche(生态龛)

　　The unique role a population plays in a community. A niche includes all characteristics that define the way a population exists in a community, from where the members live to what they eat, when they sleep, and how they reproduce.

　　nitrogenous base(含氮碱基)

　　One of the nitrogen-containing bases in DNA and RNA nucleotides. There are five nitrogenous bases in living organisms. DNA is composed of adenine, thymine, guanine, and cytosine. RNA is composed of adenine, uracil, guanine, and cytosine.

　　Nondisjunction(不分离)：细胞分裂时成对的染色体无法分开

　　Occurs when a pair of homologous chromosomes fails to separate during gamete formation. The offspring produced from these gametes have either one too many or one too few of a particular chromosome. Nondisjunction is the cause of genetic disorders such as Down syndrome.

　　Notochord(脊索)

　　A longitudinal rod of cells that forms in the least developed chordates and in embryonic stages of more developed chordates.

　　Nucleolus(核仁)

　　A dense, spherical body inside the nucleus of a cell. The nucleolus makes the RNA that is a structural component of the ribosomes.

　　Nucleotide(核苷酸)

　　The monomer of a nucleic acid. Nucleotides consist of (1) a phosphate group, a group of atoms containing phosphorus; (2) a sugar; and (3) a nitrogenous base, a compound containing nitrogen that removes H+ ions from solution. Nucleotides are grouped into two general classes, depending on the sugar group that they carry: deoxyribonucleic acids (DNA) contain the sugar deoxyribose and ribonucleic acids (RNA) contain the sugar ribose. Nucleotides are further divided by the type of nitrogenous base that they carry. DNA is composed of adenine, thymine, guanine, and cytosine. RNA is composed of adenine, uracil, guanine, and cytosine.

　　Nucleus(细胞核)

　　The large, central organelle of eukaryotes. The nucleus contains the genetic material of the cell and controls cellular activities.

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