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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 who study fossils.
B. The fossil record _________ evidence about the history of life on Earth. It also shows how different
__________ _____________, including species, have changed over time.
Paleontologists
provides
groups oforganisms
II. How Fossils Form A. For a fossil to form, either the _________
___________ or some trace of its presence must be preserved.
1. A precise _________________ must be present to form a fossil.
2. The fossil record provides ____________ ____________ about the history of life.
remains ofthe organism
set of conditions
incompleteinformation
B. Most fossils are formed in ___________ _______.
1. Sedimentary rock forms from the
_________________________________
2. These particles are carried by _________ ___________ into lakes or seas, where they eventually settle to the bottom.
sedimentary
rock.
erosion of rock into sand, silt, and clay.
streamsand rivers
3. As layers of sediment build up over time, ________________________________
_______ and become buried.
4. If conditions are right, the ________ may be 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 rock particles to lakes and seas.
Dead organisms are buried by layers of sediment, which forms new rock.
The preserved remains may later be discovered and studied.
Section 17-1
Figure 17-2 Formation of a Fossil
Go to Section:
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 of fossils in other layers of rock.
b. Rock layers __________________ are generally ________ than those below it.
age of fossils
comparing its placement
nearer to the surfaceyounger
c. Does not determine the ___________ of the rocks or the fossils.
d. Index fossils are used to ____________ ___________________. These
fossils must be easily recognized and must have existed for a short period of time.
actual age
compare the relative age of fossils
2. Radioactive Datinga. 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 ofelements in the rocks
or breakdown
half of the radioactive atoms
d. Different radioactive elements have different half-lives and therefore provide ______________ that “tick” at ______________.
Example:
Carbon-14: half-life of about ______ ________
Potassium-40 : half-life of about ______ ___________
natural clocksdifferent rates
5,730years
1.26
billion years
e. Carbon-14 is _________ by living things while ______________. After an organism dies, the __________ in its body begins to decay to form _________
___, which escapes into the air.
f. Carbon-14 has a relatively ____________,
it is useful only for dating fossils younger than about ____________.
taken upthey are alive
Carbon-14 nitrogen-
14
short half-life
60,000 years
B. Most fossils are __________. Paleontologists must reconstruct an extinct species from a few fossil bits---remains of bone, a shell, leaves, or pollen.
not intact
http://www.colorado.edu/physics/2000/isotopes/radioactive_decay3.html
Relative Dating
Can determine
Is performed by
Drawbacks
Absolute Dating
Comparing Relative and Absolute Dating of Fossils
Section 17-1
Compare/Contrast Table
Go to Section:
Imprecision and limitations of age data
Difficulty of radio-assay laboratory methods
Comparing depth of a fossil’s source stratum to the position of a reference fossil or rock
Determining the relative amounts of a radioactive isotope and non-radioactive isotope in a specimen
Age of fossil with respect to another 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 and index fossils worldwide. As geologists studied the fossil record, they found _______ ________ in the fossil animals and plants
_________________________. These times were used to mark the segments.
geologictime scale
majorchanges
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 ______.
3Precambrian and the present
Paleozoic Era
Mesozoic EraCenozoic Era
periods
17-2 Earth’s Early History and 17-3 Evolution of Multicellular Life
4.6 bya.... *___________________*many sources of energy: volcanic
activity, lightening, meteorites*______________ in atmosphere:
water vapor (H20), nitrogen (N2), and carbon dioxide (CO2), with only small amounts of hydrogen (H2) and carbon monoxide. The primitive atmosphere 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, the primitive gases may have reacted with one another and produced small organic compounds, such as nucleotides and amino acids.
3.5 bya… *geological disturbances have calmed
*____________________________
_____________ (much like the bacteria of today and well adapted)
bacteria evolve and inhabit mostenvironments
2.2 bya.... *____________________ and form mats in shallow seas. ________ ___________ to produce oxygen (02) via ______________
cyanobacteria evolveFirst
organisms
photosynthesis
1 bya.... *algae and other water-borne photosynthetic organisms abound
in the seas
* __________________ in the seas with many
______________________ like sponges, jellyfish and worms.
Green Algae Red AlgaeBrown Algae
animal life aboundsmulticellular organisms
A SPECIAL NOTE ON THE EVOLUTION OF OUR ATMOSPHERE:
1. __________________ begins in the seas2. ____________________________ (electrical
storms split atmospheric water molecules releasing a single oxygen)
3. _______________________________ - (here single oxygen and regular oxygen unite to form O3 or ozone)
4. ___________________ stratosphere - ________ _____ most of the ________________. Life on land can now thrive under this protective ______ which begins 12-15 miles above the earth’s surface.
Oxygen saturationOxygen moves into atmosphere
Oxygen reaches upper atmosphere
Ozone layer forms in filteringout harmful UV rays
shield
Paleozoic Era
550 mya.... “____________________” - the Cambrian Period records _____________ _______ of life in evolution’s history. Nearly all of the animal groups known today as well as a strange collection of animals that cannot be assigned to any living group of today appeared in a period of about 10 million years. This evidence is not based upon fossils.
the Cambrian Explosion an unmatched
burst
550 mya.... “the Cambrian Explosion”Scientists are ________________________
________________ of evolution found in the genes drawn from the living species of 16 animal groups. This has allowed scientists to estimate when all animals last shared a common ancestor with other forms of life. Although controversial, this evidence without the fossil “backup” is widely accepted by many scientists in the field today. If this finding holds up, the animal kingdom had __________________ ___________to develop than the fossils reveal.
basing this new finding upon molecular evidence
hundreds of millions of years longer
• 300 mya......______________________--the earth is now a large vegetated landmass with open plains, swamps and primitive trees. ____________ flourished in a tropical climate. Invertebrates flourished in the ocean. From these forests and swamps, of the so called “_____________” period, came the organic materials that ultimately formed our___________________.
primitive reptiles appear
Large insects
Carboniferous
fossil fuels of today
• 240 mya..._______________________ __________________________________ over a 100,000 year period. This was possibly due to a meteor impact. This occurred at the end of the_____________.
a period of mass extinctions where perhaps 95% of all life perished
Paleozoic Era
• 205 mya..... beginning of the domination of ___________ for 120 mya
• 138 mya..... ____________________ occur on land and the beginnings of tropical rain forests in some areas. The flowering plants spread and ultimately dominated the landscape through a period of 65 million years.
dinosaurs
first flowering plants
• 65 mya.....
Meteorite activity is one explanation for this extinction. This occurred at the end of the_______________.
an era of mass extinction that ended the dinosaurs as well as 75% of all plant and animal life.
Mesozoic Era
• 100,000-200,00 years ago.......
__________________ Homo sapiens date to about this time. Homo sapiens means “_________ __________” and modern humans are classified in this species.
the earliest fossils of intelligent
human
that are
can undergo can undergo can undergo can undergo can undergo
in underunderform inin
Species
Unrelated Related
Inter-relationshiops
Similar environments
Intense environmental
pressure
Small populations
Different environments
Coevolution Convergent evolution
ExtinctionPunctuated equilibrium
Adaptive radiation
Go to Section:
17-4 overview
Study guide 17-1
1. Paleontologists2. It is information about past life that is based on fossils.3. It provides evidence about the history of life on Earth and how different groups of
organisms, including species, have changed over time.4. Extinct5. False6. B, D7. Sediments settle to the bottom of lakes and seas ad bury dead organisms. The weight of
upper layers of sediment compresses lower layers into rock and turns the dead organisms into fossils.
8. a) Relative dating b) Radioactive dating9. A, B, D10. False11. True12. Half-life13. Radioactive dating14. They measure the amount of remaining radioactive isotopes it contains. The smaller the
amount, the older the sample.15. False16. Cenozoic, Mesozoic, Precambrian time, Tertiary, Jurassic, Carboniferous, Silurian,
Cambrian17. C18. A, B19. Eras and periods20. Mesozoic Era21. Cenozoic Era
Study guide 17-21. a) Hydrogen Cyanide b) Carbon Dioxide c) Carbon Monoxide d) Nitrogen e)
Hydrogen Sulfide f) Water2. False3. Spark simulating lightning storms4. A, B5. They are tiny bubbles, formed of large organic molecules, that have some
characteristics of living cells.6. False7. Experiments show that small sequences of RNA could have formed and replicated on
their own in the conditions present on early Earth.8. DNA is a more stable information-storing molecule than RNA.9. Microfossils10. A11. They produced oxygen, which first removed iron from the oceans and then
accumulated in the atmosphere.12. True13. True14. The first step was the evolution of internal cell membranes.15. It proposes that eukaryotic cells arose from living communities formed by several
organisms.16. A,C,D17. Sexual reproduction shuffles and reshuffles genes in each generation. This increase
in genetic variation greatly increases the chances of evolutionary change due to natural selection.
18. False
Study Guide 17-31. True2. A,B,C3. The animals were al soft-bodied4. Cambrian5. False6. A,B,D7. B8. C9. A10. Devonian11. Vast swampy forests of giant ferns and other plants that grew during that time formed thick
deposits of sediment that changed into coal over million of years.12. Mass extinction13. False14. Triassic, Jurassic, Cretaceous15. Reptiles16. Triassic17. True18. True19. Reptiles20. Their seeds are enclosed in a fruit, which protects the seed and aids in dispersing it to new
locations.21. More than half of all plant and animals groups were wiped out, including all of the dinosaurs.22. True23. Mammals24. They were generally warm and mild.25. First it cooled, causing a series of ice ages. The, it began to warm again.26. False
Study guide17-41. Macroevolution2. a.)extinction b.)Adaptive radiation c.)Convergent evolution d.)Coevolution
e.)Punctuated equilibrium f.)changes in developmental genes3. Possible causes include a huge asteroid striking Earth, many large volcanoes
erupting, continents changing position, and sea levels changing.4. The disappearance of so many species left habitats open. Often, the result was
burst of evolution that produced many new species.5. Adaptive evolution6. The disappearance of the dinosaurs led to the adaptive radiation of mammals.7. Convergent evolution8. B9. Coevolution10. Plats have evolved poisons prevent insects from feeding on them. Insects, in turn,
have evolved ways of inactivating or eliminating the poisons.11. gradualism12. it may occur when a small population becomes isolated or a small group migrates
to a new environment. It may also occur following a mass extinction.13. Punctuated equilibrium14. True15. Homologous hox genes establish body plans in animals that have not shared a
common ancestor in hundreds of millions of years. In addition, major evolutionary changes may be based on hox genes.
16. True
Study guide Vocabulary review
1. C2. D3. A4. C5. B6. In coevolution, two species evolve in response to changes in
each other over time.7. Convergent evolution refers to the process by which unrelated
organisms come to resemble one another as the evolve similar adaptations to similar environments.
8. Mass extinction is the occurrence of many extinctions around the same time.
9. Punctuated equilibrium is a pattern of macroevolution in which long, stable periods are interrupted by brief periods of rapid change.
10. In adaptive radiation, a single species, or a small group of species, evolves into diverse forms that live in different ways.