BIOLOGY WORKSHEET CHAPTER 17 HISTORY OF LIFE ON EARTH - NOVAK Ws Ch17HistoryOfLife K1-12.doc

Chapter 12 Section 1 How Did Life Begin

How long ago did the Earth form? ___ FOUR POINT FIVE BILLION

What did the water vapor condense into? ___ OCEANS

Scientist think life has evolved over hundreds of ___ of years? MILLIONS

Evidence of the age of the Earth can be found by measuring the age of ___. ROCKS

___ ___ is the estimation of the age of an object by measuring its content of certain radioactive isotopes. RADIOMETRIC DATING

___ are unstable isotopes that break down and give off energy in the form of charged particles called ___. RADIOISOTOPES AND RADIATION

What is this breakdown called? ___ RADIOACTIVE DECAY

___ ___ is the time it takes for one half of a given amount of a radioisotope to decay. HALF LIFE

Half life from radioactive decay

By measuring the proportions of certain radioisotopes and their products of ___, scientists can compute how many half lives have passed since a rock was formed. DECAY

The half life of uranium is 760 million years. If the age of the earth is 4.2 billion years, then 4.2/.76 = about 6 doublings or about 64 times as much uranium existed on earth at creation as exists now.

Half life from radioactive decay

These chemical reactions produced many different simple ___ molecules. ORGANIC

Energized by the ___ and ___ heat, these simple molecules formed more complex molecules that eventually became the building blocks of the first cells. SUN & VOLCANIC

The hypothesis that many of the organic molecules necessary for life can be made from molecules of ___ matter has been tested and supported by results of lab experiments. NONLIVING

In the 1920s A. I. Oparin and J. B. S In the 1920s A. I. Oparin and J.B.S. Haldane suggest that the early ___ contained large amounts of organic molecules. OCEANS

What did this hypothesis become known as? ___ PRIMORDIAL SOUP MODEL

They also hypothesized the molecules formed spontaneously in chemical reactions activated by ___ radiation, ___ eruptions, and ___. SOLAR AND VOLCANIC AND LIGHTNING

The early Earth’s atmosphere lacked ___ making formation of organic molecules possible. OXYGEN

Name four common compounds in Earth’s early atmosphere NOT including water. ___ ___ ___ ___ ___ NITROGEN GAS AND HYDROGEN GAS AND AMMONIA AND METHANE

In 1953, who tested the primordial soup model? ___ STANLEY MILLER AND HAROLD UREY

According to Figure 2, Miller-Urey heated ___ in a flask. WATER

29. According to Figure 2, Miller-Urey they then added water vapor and what other gases to the tubes? ___ ___ ___ ___ ___ NITROGEN GAS AND HYDROGEN GAS AND AMMONIA AND METHANE

According to Figure 2, Miller-Urey, after the spark and the vapors had been condensed, what did they find in the beaker below? ORGANIC COMPOUNDS

These results support the hypothesis that some basic chemicals of ___ could have formed ___ under conditions like those in the experiment. LIFE AND SPONTANEOUSLY

Recent discoveries have caused scientists to ___ the Miller-Urey experiment. REEVALUATE

Four billion years ago, Earth did not have a protective layer of ___ gas. OZONE

Without ozone, ___ radiation would have destroyed any ammonia or methane in the early atmosphere. ULTRAVIOLET

36. If these gases are absent from the Miller-Urey experiment, ___ biological molecules are NOT made. KEY

If the chemicals needed to form life were not in the atmosphere some scientists argue that the chemicals ere produced within ocean ___ or ocean ___. BUBBLES AND VENTS

In 1986, geophysicist Louis Lerman hypothesized the ___ model of chemical origins. BUBBLE

The bubbles protected the methane and ammonia needed to make amino acids from ___ ___. ULTRAVIOLET RADIATION

Next, the bubbles rose to the surface and burst, releasing simple ___ molecules into the air. ORGANIC

Once in the wind, these simple organic molecules were exposed to ultraviolet radiation which provided ___ for further reactions ENERGY

Scientists ___ about the details of the process that lead to the origin of life. DISAGREE

However, short chains of ___ have been made to form on their own in water. RNA

RNA is the nucleic acid that does what? _________ HELPS CARRY OUT DNA’S INSTRUCTIONS

In The 1980s, Thomas Cech hypothesized that ___ was the first self-replicating information-storage molecule. RNA

Certain lipids, when combined with other molecules, can form a tiny droplet whose surface resembles a ___ ___. CELL MEMBRANE

Short chains of amino acids can gather into tiny droplets called ___. MICROSPHERES

Another type of droplet, called a ___ is composed of molecules of different types, including linked amino acids and sugars. COACERVATES

Why do scientists think microspheres are important? _________ THEY MIGHT HAVE BEEN THE FIRST STEP TOWARD CELLULAR ORGANIZATION

Scientists disagree about the origin of ___. HEREDITY

Many scientists agree that double-stranded DNA evolved after ___. RNA

RNA “___” catalyzed the assembly of the earliest ___. ENZYMES AND PROTEINS

But researchers do not yet understand how DNA, RNA and hereditary mechanisms first ___. DEVELOPED

END of Chapter 12 Section 1