Biology Chapter 13 and 14

Biology Chapter 17

Evolution:

The History of Life

More than ______ of all species that have

ever lived on Earth have become extinct.

99.9%

17-1 The Fossil Record

I. Fossils and Ancient Life

A. _______________ are scientists whostudy fossils.

B. The fossil record _________ evidenceabout the history of life on Earth. Italso shows how different _______________________, including species,have changed over time.

Paleontologists

provides

groups of

organisms

II. How Fossils Form

A. For a fossil to form, either the ____________________ or some trace of itspresence must be preserved.

1. A precise _________________ must bepresent to form a fossil.

2. The fossil record provides ________________________ about the history of life.

remains of

the organism

set of conditions

incomplete

information

B. Most fossils are formed in __________________.

1. Sedimentary rock forms from the

_________________________________

2. These particles are carried by ____________________ into lakes or seas, wherethey eventually settle to the bottom.

sedimentary

rock.

erosion of rock into sand, silt, and clay.

streams

and rivers

3.As layers of sediment build up over time,________________________________

_______ and become buried.

4. If conditions are right, the ________ maybe kept intact and free from decay.

5.The sediment gradually _____________

_______

dead organisms may also sink to the

bottom

remains

compresses into

rock.

Water carries small rockparticles to lakes and seas.

Dead organisms are buriedby layers of sediment, whichforms new rock.

The preserved remainsmay later be discoveredand studied.

Section 17-1

Figure 17-2 Formation of a Fossil

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III. Interpreting Fossil Evidence

A. Paleontologists determine the _______________ using two techniques:

1. Relative Dating

a. The age of the fossil is determined by______________________ with that offossils in other layers of rock.

b. Rock layers __________________ aregenerally ________ than those below it.

age offossils

comparing its placement

nearer to the surface

younger

Relative Dating

c. Does not determine the ___________ ofthe rocks or the fossils.

d. Index fossils are used to _______________________________. These fossilsmust be easily recognized and musthave existed for a short period of time.

actual age

compare therelative age of fossils

2. Radioactive Dating

a. Based on the ___________________ ___________________.

b. Radioactive elements decay, ________ ______, at a steady rate which is measured in a unit called half-life.

c. Half-life: the length of time required for __________________________ in a sample to decay.

radioactive decay of

elements in the rocks

or break

down

half of the radioactive atoms

d. Different radioactive elements havedifferent half-lives and thereforeprovide ______________ that “tick” at______________.

Example:

Carbon-14:half-life of about ______________

Potassium-40 : half-life of about _________________

natural clocks

different rates

5,730

years

1.26

billion years

e. Carbon-14 is _________ by living thingswhile ______________. After anorganism dies, the __________ in itsbody begins to decay to form ____________, which escapes into the air.

f.Carbon-14 has a relatively ____________,

it is useful only for dating fossils youngerthan about ____________.

taken up

they are alive

Carbon-14

nitrogen-

short half-life

60,000 years

Carbon-14

Radioactive Decay

B. Most fossils are __________.Paleontologists must reconstruct anextinct species from a few fossil bits---remains of bone, a shell, leaves, orpollen.

not intact

Relative Dating

Can determine

Is performed by

Drawbacks

Absolute Dating

Comparing Relative and Absolute Dating of Fossils

Section 17-1

Compare/Contrast Table

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Imprecision and limitations ofage data

Difficulty of radioassaylaboratory methods

Comparing depth of a fossil’ssource stratum to the positionof a reference fossil or rock

Determining the relativeamounts of a radioactiveisotope and nonradioactiveisotope in a specimen

Age of fossil with respect toanother rock or fossil (that is,older or younger)

Age of a fossil in years

IV. Geologic Time Scale

A. Scientists first developed the ______________________ by studying rock layers andindex fossils worldwide. As geologistsstudied the fossil record, they found _______________ in the fossil animals and plants

_________________________. Thesetimes were used to mark the segments.

geologic

time scale

major

changes

at specific layers in the rock

1. Eras: There are __ eras between the___________________________.

a. ______________

b. ______________ (Age of Dinosaurs)

c. ______________ (Age of Mammals)

2. Periods: Eras are subdivided into ______.

Precambrian and the present

Paleozoic Era

Mesozoic Era

Cenozoic Era

periods

Continental Drift

Plate Boundaries

San Andreas Fault

17-2 Earth’s Early History and17-3 Evolution of Multicellular Life

4.6 bya....*___________________

*many sources of energy: volcanicactivity, lightening, meteorites

*______________ in atmosphere:water vapor (H20), nitrogen (N2),and carbon dioxide (CO2), with onlysmall amounts of hydrogen (H2) andcarbon monoxide. The primitiveatmosphere had little, if any, free_______.

no life forms present

poisonous gases

oxygen

* intense UV (ultraviolet radiation) from sun

* In the presence of so much available energy, theprimitive gases may have reacted with one anotherand produced small organic compounds, such asnucleotides and amino acids.

3.5 bya…*geological disturbances have calmed

*____________________________

_____________ (much like thebacteria of today and well adapted)

bacteria evolve and inhabit most

environments

2.2 bya....*____________________ and form mats in shallow seas. ___________________ to produce oxygen(02) via ______________

cyanobacteria evolve

Firstorganisms

photosynthesis

1 bya....*algae and other water-borne photosynthetic organisms abound in the seas

* __________________ in the seas with many______________________ likesponges, jellyfish and worms.

Green Algae

Red Algae

Brown Algae

animal life abounds

multicellular organisms

A SPECIAL NOTE ON THE EVOLUTION OFOUR ATMOSPHERE:

1.__________________ begins in the seas

2.____________________________ (electricalstorms split atmospheric water moleculesreleasing a single oxygen)

3._______________________________ - (heresingle oxygen and regular oxygen unite to formO3 or ozone)

4.___________________ stratosphere - _____________ most of the ________________. Life onland can now thrive under this protective ______which begins 12-15 miles above the earth’ssurface.

Oxygen saturation

Oxygen moves into atmosphere

Oxygen reaches upper atmosphere

Ozone layer forms in

filtering

out

harmful UV rays

shield

Paleozoic Era

550 mya.... “____________________” - theCambrian Period records ____________________ of life in evolution’s history.Nearly all of the animal groups knowntoday as well as a strange collection ofanimals that cannot be assigned to anyliving group of today appeared in a periodof about 10 million years. This evidence isnot based upon fossils.

the Cambrian Explosion

an unmatched

burst

550 mya.... “the Cambrian Explosion”

Scientists are ________________________________________ of evolution found inthe genes drawn from the living species of16 animal groups. This has allowedscientists to estimate when all animals lastshared a common ancestor with otherforms of life. Although controversial, thisevidence without the fossil “backup” iswidely accepted by many scientists in thefield today. If this finding holds up, theanimal kingdom had _____________________________to develop than the fossilsreveal.

basing this new finding upon

molecular evidence

hundreds of millions of

years longer

410 mya.....the “______________”

Cartilaginous Fishes: Sharks, Skates and Rays

age of the fishes

Bony Fishes

360 mya...... ________________________climb onto the land.

first land-based amphibians

Amphibian: Frog

•300 mya......______________________--the earth is now a large vegetatedlandmass with open plains, swamps andprimitive trees. ____________ flourishedin a tropical climate. Invertebratesflourished in the ocean. From theseforests and swamps, of the so called“_____________” period, came theorganic materials that ultimately formedour___________________.

primitive reptiles appear

Large insects

Carboniferous

fossil fuels of today

Coal Forest“Carboniferous Period” (300 mya)

•240 mya..._________________________________________________________over a 100,000 year period. This waspossibly due to a meteor impact. Thisoccurred at the end of the_____________.

a period of mass extinctions

where perhaps 95% of all life perished

Paleozoic Era

Mesozoic Era: Began 245 myaLasted 180 million years

Reptiles: Lay eggs on land

Bull Snake

•205 mya.....beginning of the dominationof ___________ for 120 mya

•138 mya.....____________________occur on land and the beginnings oftropical rain forests in some areas. Theflowering plants spread and ultimatelydominated the landscape through a periodof 65 million years.

dinosaurs

first flowering plants