Chapter 13
The Theory of Evolution
The Theory of Evolution by Natural Selection
Section 13.1
a. The idea that life evolves was first proposed by a Roman named __________________________ who
lived about 1,900 years before the modern theory of evolution.
b. The theory of evolution has developed through decades of scientific observation and
______________________________________. The modern theory began to take shape as a result of the
work of ___________________________________________.
c. In 1831, Darwin was asked to voyage on the HMS ________________________ as an unofficial
naturalist. What he found would challenge the traditional belief that species are
unchanging.
I.
What Darwin Saw During His Voyage
a. _________________________________________ – Darwin found signs that species evolve. He was
struck by the fact that the flora (_____________________) and fauna (__________________) of the
islands and those of the nearby coast of South America resembled each other.
b. Darwin proposed that the __________________ of Galapagos species must have migrated to the
islands from South America long ago and changed _________________ they arrived.
II.
Darwin Sought a _______________________________ Explanation for Evolution
a. The key that unlocked Darwin’s thinking was an essay written in 1798 by
_____________________________________________.
b. Malthus pointed out that the human population grew faster than ________________________
(human pop. grew exponentially while food increased arithmetically). If human
reproduction was left __________________________________, people would cover the world.
c. We don’t because of things like disease, war, and famine that will slow population growth.
i. _________________________________ – all the individuals of a species that live together in one
place at one time. Ex. The population of deer in Vancleave, MS.
III.
_________________________________________
a. Darwin realized Malthus’s ideas apply to all species. Every organism has the potential to
produce many offspring during its lifetime. In most cases, only a limited number of those
offspring survive to reproduce.
b. Individuals that have physical or behavioral traits that better suit their environment are more
likely to survive and reproduce than those that do not have such traits.
–Charles Darwin
c. ______________________________________________ – process by which populations change in response
to their environment.
IV.
Darwin suggested that organisms differ from place to place because their habitats present different
challenges to, and opportunities for survival and reproduction.
a. _______________________________ – the changing of a species that results in its being better suited
to its environment
V.
Darwin’s Ideas Have Been _______________________________
a. Best suited to survive and do well in their environment = most offspring with the traits of
the better-suited parents. Certain forms of a trait become more ________________________ in a
pop. because more individuals in the population carry the alleles for those forms. Natural
selection causes the ____________________ of certain alleles to increase or decrease over time.
b. Environments differ from place to place, so populations of the same species living in
different places ten to evolve in different directions.
VI.
Extinction Leads to Species _____________________________
a. Over time, events such as climate changes and natural disasters result in some species
becoming ________________________, which means that they disappear permanently. Species
that are better suited for the new conditions will replace the others.
Evidence of Evolution
Section 13.2
VII.
Darwin’s theory is almost universally accepted. Based on a large body of supporting
__________________________________, most scientists agree on the following major points:
a. Earth is about ___________________________ years old.
b. Organisms have inhabited Earth for most of its history.
c. All organisms living today evolved from earlier, _______________________ life forms.
VIII.
However, the fossil record (and so the record of evolution) is not ______________________. Many species
have lived in environments where _______________________ do not form. Even if an organism does live
in good fossil-making environments, the chances are slim that its dead body will be buried in
sediments before it _____________________.
a. Although the fossil record will never be complete, it presents strong evidence that evolution
has taken place. ______________________________, scientists who study fossils, can determine a
fossil’s age fairly accurately using radiometric dating.
b. __________________________________________ enables paleontologists to arrange fossils in sequence
from oldest to youngest. When this is done, orderly patterns of evolution can be seen.
IX.
Biological Molecules Contain a Record of Evolution
a. If species change over time, then the genes that determine their characteristics should have
also changed (new taller giraffes, no stretched necks).
b. ________________________________________ – species from which two or more species have diverged.
c. Concerning ______________________________: Species that share a recent common ancestor (ex.
Humans and gorillas) have few amino acid sequences (order of amino acids to make
proteins) where species that share a common ancestor more distantly (ex. Humans and
frogs) have many amino acid sequence differences.
d. Concerning ______________________________________: Scientists can directly estimate the # of
nucleotide changes that have happened since two species diverged from a c. ancestor by
comparing the exact nucleotide sequence of genes. Using this, they can make a
_______________________________________________ to show how organisms are related through
evolution (very strong evidence)
X.
Anatomy and Development Suggest Common Ancestry
a. Comparisons of the anatomy (structures) of different types of organisms often reveal basic
similarities in body structures, even though their functions may be very different.
b. ______________________________________ – some structures (like bones) are present in an organism,
but reduced in size and either have no use or have a less important function (ex. Flightless
wings on a cormorant or the appendix on humans)
c. As different vertebrates evolved, particular sets of bones evolved differently, but similar
bone structure can be seen. Homologous structures are structures that share a common
ancestry – a similar structure in two organisms can be found in their common ancestor.
XI.
Does Evolution Occur in Spurts?
a. The model of evolution in which gradual change over a long period of time leads to species
formation is called _________________________________________________.
b. But Gould and Eldredge from America hypothesize that evolution occurs in spurts. This
model of evolution, in which periods of rapid change in species are separated by periods of
little or no change, is called ______________________________________________________________.
Examples of Evolution
Section 13.3
XII.
Industrial Melanism
a. A well-studied example of natural selection in action is __________________________________________,
the darkening of populations of organisms over time in response to industrial pollution.
b. The best-known case involves the European peppered moth, Biston betularia. Among the
members of this species, there are two color variations. Light and dark. The dark was very
rare until about the 1850s when industrialization was occurring in major cities. 100 years
later, almost all of the peppered moths near industrial centers were dark.
XIII.
The Formation of New Species Begins with ________________________________________
a. Species formation occurs in a series of stages. Evolution continuously molds and shapes a
species to improve its “_____________” to its environment.
b. The accumulation of differences between groups is called _____________________________________.
c. Within populations, divergence leads to the formation of new species. Biologists call the
process by which new species form __________________________________________.
XIV.
Forming Ecological _____________________
a. A species often lives in several different kinds of _____________________________________________.
b. If their environment is different enough, local populations can become very
________________________.
c. Over time, populations of the same species that differ __________________________________ because
of adaptations to different living conditions become what biologists call ecological races.
d. They are not different enough to be different species, but they may not be able to interbreed
successfully.
XV.
Maintaining a New Species
a. _______________________________________________ – inability of formerly interbreeding groups to
mate or produce fertile offspring. Could be geographically isolated or may reproduce at
different times.