Chapters 16 and 17

Natural phenomena that occurred in the past can be explained by ______________________ ____________________________________________________________________________

Rather than learn from experience, we can use _____________to gain insight into the past

Requires “an intellectual leap from the familiar to the unknown”

Millions of asteroids orbit the sun _______________________: created

50,000 years ago by a 330,000-ton asteroid that slammed into the Earth

Geologists examine tons of meteorites and other physical evidence to establish cause and effect for events that occurred before humans were present

a)Barringer craterb)Iridium layerFigure 16.1, page

238

Evidence: ________ rich clay layer buried in the soil

Iridium is not normally found in the Earth’s crust BUT is a common element in asteroids

Under Yucatan Peninsula in Mexico, scientists discovered a crater 274 kilometers across and 1 km deep

Crater provides evidence of ___________________ 40 million times greater than Barringer impact

Large impacts like these influence the history of life on Earth in a major way

Mass extinction occurred ____________ years ago

Fossil evidence from the K-T boundary 65 million years ago points to some global disturbance related to the extinction of dinosaurs

Asteroid impacts 5 million years ago may have influenced human evolution

Aristotle: observations led him to believe that nature was a _________________________________

By the fourteenth century, the ancient view of gradual levels of organization had been formalized into the great ___________________

Spans from lifeless matter to the most complex organisms

Each being had its fixed place in the divine order which had not changed since creation

Species: ____________________________

Observations made by a number of scientists about the natural world did not necessarily fit into the great Chain of Being

Includes questions about:

_____________________: the study of patterns in the geographic distribution of species

Global voyages of the Europeans lead to the discovery of tens of thousands of unusual species not known or found in Europe

Naturalists such as Alfred Wallace began to catalog and name these species

They also began to see patterns in geographic distribution

Noticed intriguing patterns Example: species that are found only on

isolated ocean islands that are similar to other species found thousands of miles away

Large flightless birds on different continents – all occupying similar habitats and exhibiting similar behaviors

Can also find similar patterns in the plant kingdom

Studies of the ______________ ______________ of seemingly unrelated animals led to questions of why certain structures should be so similar Ex: bones in human arm and a porpoise flipper

Some thought that body parts were so perfect at the time of creation that there was no need for any variation

This idea is challenged by the existence of certain bones that are still present without a function ex. coccyx (tail bone) in humans

Geologic studies identified identical sequences of rock layers in different parts of the world

_____________ from rock layers were recognized as evidence of earlier life

Layers revealed increasing levels of complexity as they got closer to the surface

Also challenges the idea of the Chain of Being If all species were perfect, why do we observe

these changes in similar organisms over time? Why are some species extinct?

Georges Cuvier: an anatomist who was trying to reconcile the growing evidence of evolution

_____________: change that occurs in a line of descent

Cuvier’s concept of ___________________ explained the abrupt changes in the fossil record in different rock strata

Global catastrophes shaped the Earth frequently and caused extinction of many species

Survivors were not new species; their ancestors fossils just had not been found

Jean-Baptiste Lamarck: theory of ____________________________________________ Thought offspring inherited characteristics

acquired by a parent __________ their lifetime Idea that simple forms had changed into

more complex ones because of a drive towards perfection from the Chain of Being

Example: giraffe stretching its neck to reach higher branches would result in offspring with longer necks

As a child in the early 1800s, Charles Darwin was curious about nature

In college he studied medicine (and hated it) and then received a degree in theology

When Darwin was 22, botanist John Henslow arranged for Darwin to sail around the world on the ___________ as a ship’s naturalist

Figure 16.5, page 242

Throughout the trip, Darwin studied and collected a variety of plants and animals in addition to a number of fossils – all from different parts of the world

Also reading Lyell’s Principles of Geology, which proposed a __________________________: the notion of a gradual, lengthy molding of the Earth’s geologic structure

Darwin realized this would mean the Earth was millions (rather than thousands) of years old

Theory of Uniformity: _______________________

Darwin returned after five years at sea with thousands of specimens and notes about his findings and travels

In time, he was able to make enough connections to understand how species might evolve

In Argentina, Darwin had observed extinct glyptodonts that bore a large resemblance to living armadillos

Darwin wondered if the present species had evolved from the extinct one

Thomas Malthus: ____________________ Suggested that as a population outgrows its

resources, its members must compete for what is available; some will not make it

Darwin observed that individuals were not alike Also deduced that any population has the

capacity to produce more individuals than the environment can support

Realized that variations in traits can influence an individual’s ability to secure limited resources, and therefore, to survive and reproduce

Galapagos Islands are 900 kilometers from South America (about 560 miles)

Species of finches are unique but share characteristics with mainland finches

Perhaps they all descended from a common ancestor

Species lived in diverse habitats: coastal area, dry lowlands, and in mountain forests

______________ living in different environment had different beak types Beaks were highly adapted to different food

sources Grubs, seeds, insects, leaves… Different beak characteristics were better

for eating different types of food Darwin reasoned that conditions in the

prevailing environment “select” those individuals that are best suited to that environment

The following are put in the context and terms of modern genetics.

Observation: All populations have the reproductive capacity to increase in number over generations

Observation: No population is able to increase indefinitely, because its individuals will run out of food, living space, and other resources

Inference: Sooner or later, individuals will end up ________________________________________

Observation: All individuals have the same genes, which represent a pool of heritable information

Observation: Most genes occur in different molecular forms (alleles), which give rise to differences in phenotypic detail

Inference: Because adaptive traits promote survival and reproduction, they must increase in frequency over the generations, and less adaptive traits must decrease in frequency or disappear

Conclusions: Environmental factors act on the range of variation in traits that are shared by individuals of a population. The differential survival and reproduction of such individual is called _________________________.

Darwin’s theory has been debated, but scientists continue to gather more supporting evidence to this day.