Name _____________________________________________________
Test Date _Fri, 3/4_____
UNIT XII - EVOLUTION
I. THE THEORY OF EVOLUTION (pp. 369-386)
The theory of evolution is one of the most fundamental concepts in Biology. Evolution is defined as
_changes_______ in a _population of organisms_______________________ over time. The scientist
considered to be the founder of modern evolutionary theory is _Charles Darwin__________________.
A. History of Evolutionary Theory – During the 1700s, several scientists began challenging the idea
of a world in which changes did not occur. These scientists and their hypotheses were very important to
Darwin’s work.
1. Gradualism - _Geologists_______ first suggested that the planet was much _older______ than
previously thought; began to find evidence that _changes__________ were slowly, but constantly
taking place.
2. Malthus – Published an essay that had a huge impact on Darwin. Proposed that organisms
_over_____ - reproduce; in other words, reproduce at a _greater_________ rate
than resources can supply.
3. Lamarck
Lamarck was one of the first scientists to propose a mechanism for evolution; that is, the _changes___
in a _population__________ of organisms over _time_____. His major hypotheses included:
 Tendency Toward Perfection – Stated that organisms were continually changing in order to
_live more successfully____________.
 Use and Disuse – Changes in _size______ and/or _shape_________ of a structure in an
organism was a response to use or disuse. Structures used extensively _grew bigger______
and structures used less frequently _got smaller____.
 Inheritance of _Acquired___ Traits
B. Charles Darwin (1809 – 1882)
1. Darwin’s History
Darwin’s data was collected on a 5-year journey around the world on the USS _Beagle___.
He made observations and collected data throughout the journey. He used this data to propose a
_hypothesis__________ to explain the diversity he saw. The area that had the greatest impact on
Darwin was the _Galapagos_____ Islands due to the differences he saw in the same
animals living on different islands.
2. Darwin’s Observations
 Members of a population often vary greatly in their _traits________.
 Traits are inherited from _parents_____ to _offspring_______.
 All species are capable of producing _more____ offspring than _environment can support_______
 Due to a lack of _food______ or other resources, many of the offspring _will not survive_______.
3. Darwin’s Theories – Based on his observations and the hypotheses of other scientists
 Organisms with favorable _traits____ tend to survive and _reproduce_____________________; thereby
leaving more descendents than other individuals
 This will result in an accumulation of these traits in the _offspring____________, changing the original
_genetic________ make-up of the population
4. Darwin’s Legacy
 Did not publish his findings for years
 Alfred Wallace – formed identical _hypotheses_______ based on his research. Sent his manuscript to Darwin,
and finally Darwin was persuaded to publish his own conclusions
 Released “_Origin of Species_______________________________”, still considered one of the greatest
scientific studies ever
II. THE PRINCIPLES OF EVOLUTIONARY THEORY
A. Evolution occurs because of natural selection - a mechanism for change that occurs when organisms
with _favorable______ characteristics for a particular environment _survive____________,
_reproduce________, and pass these characteristics on to _offspring______________.
B. The ability of an organism to survive and reproduce in its environment is known as _fitness___.
C. Fitness is based on _adaptations______. An adaptation is any trait that aids in the
_survival______ and _reproduction____ of an organism. Examples of adaptations are
_thorns on a cactus, camouflage, antibiotic resistance in bacteria_________
D. As organisms _survive__ and adapt, _speciation _____ may occur. Speciation is the formation of
new species - a group of similar organisms that _breed___ with one another and produce
_fertile offspring . . . that is, babies that can make babies!____________.
E. The failure of an organism to _adapt___ to changes in its environment will ultimately lead to its
_extinction______ because of _natural selection___.
III. EVIDENCE FOR EVOLUTION
A. Fossils – Fossils are _ preserved bones and traces of organisms _
Fossils provide a record of earlier life and evidence that evolution has occurred.
B. Biogeography – Variations are seen in the same types of animals based on their _environment_____.
In addition, there are some organisms that live in very different locations but they have similar
characteristics because _ their environments are similar; for example, climate, food sources, etc _.
C. Homologous Structures – Scientists use anatomical studies of different organisms for evidence of
evolutionary relationships. For example, appendages that are very similar in structure, but differ in
function are known as _homologous___ structures. Examples of homologous structures are
_arm of human, flipper of dolphin, wing of bat______.
D. Vestigial Structures - A structure that is reduced in function in a living organism, but may have been used by an
ancestor is known as a _vestigial________ structure. A structure may become vestigial when an organism
changes in form or behavior. Examples are _wings of ostrich, eyes on cave fish, *human appendix*_.
E. Embryology – Similarities in the structures of developing _embryo___ of different organisms are
considered to be proof of a close evolutionary relationship.
F. DNA Sequencing – Scientists use DNA studies to determine the evolutionary relationship between
organisms. The more similar the DNA, _the closer the evolutionary relationship______________
IV. MECHANSIMS FOR EVOLUTION
Evolution does not occur in an individual; instead it refers to _heritable___ _changes______ that
occur in a _population____ over time. There must be mechanisms available for _genetic_______
changes to occur:
A. Mutation – A mutation is a _change in DNA____________. Although mutations are most
often _harmful___________, sometimes the resulting change in _phenotype______ may be
beneficial to an organism under certain conditions. If the change occurs in the _gametes____, this
change will be passed onto the offspring of that organism. A positive mutation that provides a survival
advantage is known as an _adaptation____.
B. Diploidy – Most organisms are diploid, which means _double set of chromosomes_______.
This allows for increased genetic variation in a population.
 Heterozygote Advantage – Seen in _sickle cell allele___ and _malaria_.
 Recombination - Leads to increased genetic variation as a result of _crossing over__ during prophase I_____ of
_meiosis______.
C. Gene Flow – Gene flow occurs when organisms from one community migrate to another. This
introduces new _alleles______ into the _population____ which can lead to a change in the
genetic make-up of the population.
D. Genetic Drift – This describes a situation in which change in a population is magnified because the
population size is very _small_________. Causes of genetic drift include
 Bottleneck effect – large portion of population _destroyed in disaster___
 Founder effect – segment of population moves to new _habitat__________