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Darwin wrote up his observations and conclusions (including evidence) in a book, but waited 10 years to publish it
________________ independently arrived at the same conclusions and sent him an essay to read Known as the father of biogeography
Darwin published ____________________the next year, on ___________________________
________________ : an individual’s adaptation to the environment as measured by its relative genetic contribution to future generations
Descent with modification happens when:
___________________________________________
_______________________________________
500 years ago, Leonardo da Vinci questioned the existence of __________________________________
Prevailing belief: deposited by an ancient flood Rocks composed of cake-like layers; some
contained shells while others did not Considered it to be similar to spring flooding of
rivers and the deposition of silt on riverbeds If layers had been deposited over time, vertical
sequence of fossils would be a fossil record of past life
By the 1700s, fossils were accepted as remains or impressions of organisms that lived in the past
Fossil: from translation of Latin word
meaning __________________________ Interpretation of fossils often
influenced by cultural beliefs
Most fossils are remains of __________________ ________________________________________
Trace fossils are indirect evidence obtained from impressions Example: tracks
___________ are fossilized feces
Why are fossils hard parts instead of soft matter?
The ________________ process is very slow Begins when an organism dies and is
covered in ash or sediment Water infiltrates the remains, and metal
ions or other inorganic molecules replace the organic ones in bones or other hard tissues
Soft tissues often decay The pressure increases from additional
sediment deposited on top.
Pressure + mineralization = transformation of the remains into stony fossils
Fossilization is favored when remains are ___________________ and remain ____________ These conditions are rare; therefore,
fossils are rare Also must remain undisturbed
Scavengers and erosion often make this difficult…
Sediment particles (including silt, sand, volcanic ash, and other particles) settle and become compressed
Over time, the layers of sedimentary rock form in varying thickness
___________________ : the formation of layered sedimentary rock
The layers and their chemical/physical properties provide context for the fossils found within them
Figure 16.10, page 247
Currently more than 250,000 species of fossils Fossil record will ___________ be complete Unlikely that a fossil of each species that has
ever lived will be found Favors species with hard parts, dense
populations with wide distribution, and that persisted a long time
________________ (line of descent) of organisms that were remote or lived for brief periods of geologic time are less likely to be represented
Fossil dating became more accurate with the discovery of radioisotope decay
________________ : a form of an element with an unstable nucleus that decays and becomes other elements
Decay not influenced by environmental factors; serves as a predictable and constant clock
Used to date fossils and rocks More recent fossils may be dated using their
ratio of carbon isotopes (carbon dating)
Early geologists counted backward through layers of sedimentary rock to observe transitions in the fossil sequence around the world
Similar transitions were observed in different locations around the world
These became the basis for divisions in
the ___________________________
A chronology of the Earth’s history Boundaries for major intervals can be
determined by transitions in the fossil record Major divisions can be correlated with
macroevolutionary events Includes dates obtained by radiometric
dating
_____________________ : major patterns, trends, and rates of change among lineages
Geologic time clock
Figure 16.13, page 249
Figure 16.12, page 249
Model suggests that all continents were part of a large supercontinent called _______________ Eventually split and drifted apart Gondwana: southern supercontinent
Jigsaw-like fit between the Atlantic Ocean coastlines of South America and Africa
Helped explain why the same fossils appear in sedimentary rocks on both sides of the ocean
This theory is called plate tectonics
Movements of Earth’s tectonic plates on outer layer of rock rafted land masses to new positions
Movements had profound impacts on the directions of life’s evolution
Evidence for plate tectonics theory Distribution of global land masses Global fossil distribution Magnetic rocks found in different places around the
world Seafloor spreading from mid-oceanic ridges (fissures)
Figure 16.13, page 249
d 66 myac 152 myab 237 myaa 420 mya e 14 mya
We now know that continents collide, split, and move vast distances over the surface of the Earth.
Continental drift (plate tectonics) influences life and evolutionary forces on land and in the oceans
________________ _______________ is the study of body forms and structures of major groups of organisms, such as vertebrates and plants
Similarities between species may indicate evidence of descent from a common ancestor
_____________ _____________ : similar body parts shared among related organisms The structures may be used differently, but
the same genes direct their development
In time, isolated populations begin diverging genetically
Over time, differences appear in body form
This macroevolutionary process is called ________________________________
In spite of changes in form, a careful examination reveals common heritage
Example: the four-legged ancestry of land vertebrates
Divergences led to the major vertebrate groups Divergence seen in the five-toed limb
The same five-toed limb has been modified into a human arm, an elephant foot, or bird wing
Although they differ in use, size, and shape, they retain the same structure and positioning of bony elements
Figure 16.16, page 252
• Certain bones were lost over time• Example: digits
numbered 1-5• Bones of
forearms: colored in orange and pink
Stem reptile (a cotylosaur)
4
3
21
pterosaur
Figure 16.16, page 252
3
2
1
chicken
Figure 16.16, page 252
3
2
penguin
Figure 16.16, page 252
Figure 16.16, page 252
543
2
1
porpoise
Figure 16.16, page 252
543
2
1
bat
Figure 16.16, page 252
54
3 2
1
human
Figure 16.16, page 252
5
4
3
21
elephant
Similar body parts are NOT always homologous and do not always share a common lineage
They may have evolved independently in separate lineages
_______________________ look alike in different
lineages but did not evolve in a shared
ancestor
____________________________: evolution of
similar body parts in different lineages
Example: ______________________________ All act in flight but examination of
their structure reveals that they are not homologous
Unique adaptation for flight are evidence that wing surfaces in bats, birds, and insects are analogous
Figure 16.17, page 253
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