Download notes - Humble ISD

Name _____________________________________________________
Test Date _____________________
UNIT XI – EVOLUTION (chapter 15)
I. THE THEORY OF EVOLUTION
The theory of evolution is one of the most fundamental concepts in Biology. Evolution is defined as
_____________ in a ________________________________ 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 - ________________ first suggested that the planet was much _____________ than
previously thought; began to find evidence that ________________ were slowly, but constantly
taking place.
2. Malthus – Published an essay that had a huge impact on Darwin. Proposed that organisms
___________- reproduce; in other words, reproduce at a ____________________ rate
than resources can supply.
3. Lamarck
Lamarck was one of the first scientists to propose a mechanism for evolution; that is, the ______________
in a _______________ of organisms over ___________. His major hypotheses included:
 Tendency Toward Perfection – Stated that organisms were continually changing in order to
_______________________________________________.
 Use and Disuse – Changes in _____________ and/or _____________ of a structure in an
organism was a response to use or disuse. Structures used extensively _____________________
and structures used less frequently __________________.
 Inheritance of ________________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 HMS _________________
He made observations and collected data throughout the journey. He used this data to propose a
________________ to explain the diversity he saw. The area that had the greatest impact on
Darwin was the _______________ Islands due to the differences he saw in the same animals living on different
islands. Ex: _______________________________________________________________________________.
He began to suspect that populations from the mainland changed after reaching the Galapagos.
Upon his returned he talked to animal breeders & called what they did to direct breeding to produce offspring with
the desired traits ________________________, same as what we called selective breeding last unit.
2. Darwin’s 4 Basic Principles (Observations)
 Members of a population often vary greatly in their _______________.
 Variations (traits) can be inherited from __________________ to __________________.
 All species are capable of producing _____________ offspring than _________________________________
 Variations that increase reproductive success will have a greater chance of being passed on than those that do
not increase reproductive success.
3. Darwin’s Theories – Based on his observations and the hypotheses of other scientists
 Organisms with favorable ____________ tend to survive and ______________; thereby leaving more
descendents than other individuals
 This will result in an accumulation of these traits in the ________________, changing the original
_____________ make-up of the population
4. Darwin’s Legacy
 Did not publish his findings for years
 Alfred Wallace – formed identical ___________________ based on his research. Sent his manuscript to
Darwin, and finally Darwin was persuaded to publish his own conclusions
 Released “___________________________________________________” 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 ________________ characteristics for a particular environment __________________,
_______________, and pass these characteristics on to __________________.
B. The ability of an organism to survive and reproduce in its environment is known as _________________.
C. Fitness is based on ___________________. An adaptation is any trait that aids in the
______________ and __________________ of an organism. Examples of adaptations are
_______________________________________________________________________
D. As organisms _______________ and adapt, ________________ may occur. Speciation is the formation of
new species - a group of similar organisms that ________________ with one another and produce
______________________________________________________________________!. For speciation to occur
population must diverge & then be reproductively isolated.
E. Two types of Speciation:
Allopatric speciation: physical barrier divides on population into two or more:
EX: ___________________________________________________________
Sympatric speciation: species evolves into new one without a physical barrier. Seen in insect & plant species.
F. Isolating Mechanisms allow for the gene pools to become _________________ so they can form a new _____________.
Reproductive Isolation-as a new ________________ evolves, populations become ____________________ isolated
from each other.
 Prezygotic –prevents reproduction by making _________________________ because of geographic,
ecological, behavioral, temporal or other differences
EX: __________________________________ have overlapping ranges & are similar in appearance but
use different mating songs & do not interbreed.
EX: Fireflies- similar species but mate at different _______________________________
EX: Trout- different species in same stream but mate diff. time of year
 Postzygotic- when fertilization has occurred but a _______________ offspring _____________________
or reproduce; prevents offspring survival or reproduction
EX: Mule, liger
G. The failure of an organism to __________________to changes in its environment will ultimately lead to its
__________________ because of __________________________.
III. EVIDENCE FOR EVOLUTION
A. Fossils – Fossils are _ _______________________________________________
Fossils provide a record of earlier life and evidence that evolution has occurred.
Fossils also provide evidence about the earth’s _________________, geography, and _________ forms.
Almost _____% of Earth’s history occurred during the __________________ Time. There are two major classes of
Traits when studying transitional fossils:derived traits-newly evolved features such as feathers, that do not appear in
the fossils of common ancestors. Ancestral traits are more primitive features such as teeth & tails, that do appear in
ancestral one
B. Biogeography – Variations are seen in the same types of animals based on their ______________________
In addition, there are some organisms that live in very different locations but they have similar
characteristics because _____________________________________________________________
C. Comparative anatomy – Scientists use anatomical studies of different organisms for evidence of
evolutionary relationships.
1. Homologous structures- For example, appendages that are very _______________ in structure, but differ in
___________________ are known as _____________________ structures.
Examples of homologous structures are __________________________________________________
2. Vestigial Structures - A structure that is ______________ in function in a living organism, but may have been
used by an ancestor is known as a ______________ structure. A structure may become vestigial when an
organism changes in form or behavior. Examples are ______________________________________________
3. Analogous structures- Not all similar features are evidence of common ancestry. Analogous structures can be
used for the ________________ & can be superficially similar in construction but are ________________ from a
common ancestor. They show that functionally similar features can evolve independently in similar environments.
Ex. Wings of birds vs. insects
D. Embryology – Similarities in the structures of developing ___________________ of different organisms are
considered to be proof of a close evolutionary relationship.
E. Comparative biochemistry – Scientists use DNA studies to determine the evolutionary relationship between
organisms. The more similar the DNA, _____________________________________
IV. MECHANSIMS FOR EVOLUTION
Evolution does not occur in an individual; instead it refers to _______________________ that occur in a population over
time. There must be mechanisms available for _____________________ changes to occur:
A. Mutation – A mutation is a _____________________. Although mutations are most often _________________,
sometimes the resulting change in ________________ may be beneficial to an organism under certain conditions. If
the change occurs in the __________________ this change will be passed onto the offspring of that organism. A
positive mutation that provides a survival
advantage is known as an _____________________
B. Diploidy – Most organisms are diploid, which means ___________________________________
This allows for increased genetic variation in a population.
 Heterozygote Advantage – Seen in ________________________ and _______________.
 Recombination - Leads to increased genetic variation as a result of ___________________ during
______________ of ______________.
C. Gene Flow – Gene flow occurs when organisms from one community migrate to another. This
introduces new ________________ into the _______________________ 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 ___________. Causes of genetic drift include:
 Bottleneck effect – large portion of population ______________________________
 Founder effect – segment of population moves to new __________________________
E. Single Gene Traits-Natural selection on ___________________ traits can lead to changes in _________________
frequencies and therefore to evolution. EX: _____________________________________________
F. Polygenic Traits-Natural selection can affect the distributions of phenotypes in 3 ways:
 Directional Selection-Individuals at ______ end of the bell curve have higher fitness than those in the middle or
other end. ____________________________________________________________________________.
 Stabilizing Selection-Individuals in the _________ have the highest fitness causing the curve to narrow.
_______________________________________________________________________________________.
 Disruptive Selection-when individuals at the _______ of the curve have the higher fitness. If lasts long enough
can cause the curve to split and create ______ distinct phenotypes. _________________________________
_______________________________________________________________________________________
V. MACROEVOLUTION- refers to large-scale evolutionary pattern and processes that occur over long periods of time.
A. Extinction-More than ______% of all species that have ever lived are now ___________, which means the species
has died out. Darwin proposed possible reasons with competition for _________________________________________
 ________ extinction has occurred several times, wiping out entire ___________________________
 ________________, volcanic action, and _______________________ movement have been blamed.
 Mass extinctions clear the way for _____________________ of other species. EX:
B. Adaptive radiation or divergent evolution- the process where a __________ species has evolved through
______________________ __________ into diverse forms in short period of time that live in different ways. Often
follows mass extinctions
EX: ___________________________________________________________________________________
C. _______________________________ when unrelated species evolve similar traits even though they live in different
parts of the world because of similar ecology & climate
___________________________________________________________________
D. __________________________ is when a change in one organism leads to a
________________________________change in another organism.
EX: ___________________________________
E. ________________________ Equilibrium is another pattern of evolution. Unlike ____________________________,
punctuated equilibrium is characterized with long periods of ____________________ interrupted by brief periods of
____________________ change. It is controversial but known that evolution does occur at different rates.
1.