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Lesson Six

The Origin and Diversity of Life

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Big bang

Oscillation[]n. 摆动 , 振动Eruption[]n. 爆发 , 喷发，火山灰 , [ 医 ] 出疹

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1948 年伽莫夫建立热大爆炸的观念，宇宙学家们为我们勾画出这样一部宇宙历史：大爆炸开始时 150－ 200亿年前，极小体积，极高密度，极高温度。大爆炸后 10-43秒宇宙从量子背景出现。大爆炸后 10-35秒同一场分解为强力、电弱力和引力。大爆炸后 10-5秒 10万亿度，质子和中子形成。大爆炸后 0.01秒 1000亿度，光子、电子、中微子为主，质子中子仅占 10亿分之一，热平衡态，体系急剧膨胀，温度和密度不断下降。

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大爆炸后 0.1秒后 300亿度，中子质子比从 1.0下降到0.61。大爆炸后 1秒后 100亿度，中微子向外逃逸，正负电子湮没反应出现，核力尚不足束缚中子和质子。大爆炸后 13.8秒后 30亿度，氘、氦类稳定原子核 (化学元素 )形成。大爆炸后 35分钟后 3亿度，核过程停止，尚不能形成中性原子。大爆炸后 30万年后 3000度，化学结合作用使中性原子形成，宇宙主要成分为气态物质，并逐步在自引力作用下凝聚成密度较高的气体云块，直至恒星和恒星系统。

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Krakatau[] ( 喀拉喀托火山 ) Krakatoa 喀拉喀托火山

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Linnaues

binomial system of nomenclature

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The five kingdoms

Kingdom[]n. 界Phylum/division[]/[]n. 门Class 　纲Order 　目Family 　科Genus[]n. 属species[]n. 种

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Clade 　 [] 　进化枝

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coacervate[]n. 团聚体，凝聚层

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Continental drift

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Earth

core

mantle

crust

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Ozone layer

Stratosphere []n. 平流层Troposphere 　 []n.[ 气 ] 对流层

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taxon[]n. 分类单位，分类群hierarchical []adj. 分等级的

taxonomy[]n. 分类法 , 分类学

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Text 1 a home for life: formation of the solar system and planet earth

Primordial []adj. 原始的 ; 基本的，主要的； [ 生物学 ] 原始的，原生的；primordial cells. 原生细胞

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2 the emergence of life: organic and biological molecules on a primitive planet

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Miller & Urey Experiment

S.Miller, the student of H.Urey.

H.Urey, 1893-1981 ， finder of diplogen (D), Nobel laureate 1934.

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– Polymers are formed by condensation

reactions (hydrolysis) that remove H and OH

forming H2O.

Researchers have produced polymers by

dripping solutions of monomers onto hot

sand, clay, or rock.

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– Similar conditions likely existed on

the early Earth when dilute solutions of

monomers splashed onto fresh lava or

at deep-sea vents. This quickly

vaporizes H2O and concentrates the

monomers from which polymers form.

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Sidney Fox made small polypeptides by dripping amino acids onto hot sand = proteinoids

– Add zinc and iron and longer polymers are formed.

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Short polymers of ribonucleotides can be synthesized abiotically in the laboratory.– If these polymers are added to a solution of ribonucleotide monomers, sequences up to 10 baseslong are copied from the template according to the base-pairing rules = self-replication– If zinc is added, the copied sequences may reach 40nucleotides with less than 1% error.

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RNA world

Hypothesis that the first genes were short stra

nds of RNA

– Small RNA molecules can be formed abioti

cally by polymerization of free nucleotides

– RNA molecules can self-replicate

– RNA can fold into 3-D structures that act as

simple enzymes

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RNA world

In the 1980’s Thomas Cech discovered that RNA molecules are important catalysts in modern cells.

These RNA catalysts are called ribozymes.

• Ribozymes also help catalyze the synthesis of new RNA polymers [rRNA, tRNA, mRNA].

• In the pre-biotic world, RNA molecules may have been fully capable of ribozyme-catalyzed replication.

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3 the earliest cells

Aerobic[]adj. 依靠氧气的 , 与需氧菌有关的 , 增氧健身法的

Anaerobic[]adj.[ 微 ] 没 有 空气而能生活的 , 厌氧性的

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3 the earliest cells

Heterotroph[]n.[ 生 ] 异养生物hetero-[] 表示“其他的 , 不同的 ,异”之义 ( 元音之前作 heter-)

Autotroph[]n.[ 生 ] 自养生物 , 靠无机物质生存的生物-trophy suff. （后缀）Nutrition; growth: 表示“营养；增长”：hypertrophy. 肥大

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earliest cell

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The carbon cycle is the biogeochemical cycle by w

hich carbon is exchanged between the biosphere, geo

sphere, hydrosphere,and atmosphere of the Earth.

On land, the major exchange of carbon with the at

mosphere results from photosynthesis and respiration.

In the oceans, carbon dioxide exchange is largely c

ontrolled by sea surface temperatures, circulating cur

rents, and by the biological processes of photosynthe

sis and respiration.

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4 the changing face of planet EarthThe Earth's rocky outer crust solidified billions of

years ago, soon after the Earth formed. This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

The plates are made of rock and drift all over the globe; they move both horizontally (sideways) and vertically (up and down). Over long periods of time, the plates also change in size as their margins are added to, crushed together, or pushed back into the Earth's mantle. These plates are from 50 to 250 miles (80 to 400 km) thick.

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4 the changing face of planet Earth

The map of the Earth is always changing; not only are the underlying plates moving, but the plates change in size. Also, the sea level changes over time (as the temperature on Earth varies and the poles melt or freeze to varied extents), covering or exposing different amounts of crust.

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4 the changing face of planet Earth

glaciation[]n. 冻结成冰 , 冰河作用glacier[]n. 冰河 , 冰川moraine[]n.[ 地 ] 冰碛crevasse[]n. 破口 , 崩溃处 , 裂缝cirque[]n. 圆形山谷 , 圆环 , 盆地谷Neve n.[ 地 ] 粒雪 , 冰原arete[, ]n. 险峭的山脊

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Glaciers

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Extinction

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5 taxonomy: categorizing the variety of living things

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phylogenetic[]adj. 系统发生的 ,

动植物种类史的

cyano- [][ 前缀 ] 表示“蓝色 ,

深蓝色”之义

Monera 原核生物界

Protista 　原生生物界Fungi []n. 真菌界Plantae[:]n. 植物界　Animalia[]n. 动物界 , 动物类

6 the five kingdoms