Download Natural Selection at Work Factors in Natural Selection

Chapter 12
The Theory of Evolution
Section 1: The Theory of Evolution by
Natural Selection
Section 2: Evidence of Evolution
Section 3: Examples of Evolution
Darwin
Section 1
The Theory of Evolution by Natural Selection
Objectives:
•Identify several observations that led Darwin to
conclude that species evolve.
•Summarize the main points of Darwin's theory of
evolution by natural selection as it is stated today.
•Contrast the gradualism and punctuated equilibrium
models of evolution.
Section 1
The Theory of Evolution by Natural Selection
Darwin Proposed a Mechanism for Evolution
•Science Before Darwin’s Voyage
•Lamarck proposed an incorrect mechanism for how
organisms evolve, but he correctly pointed out that
change in species is linked to an organism’s
environment.
• Lamarck: giraffes stretch their necks and pass this
long neck to their offspring.
•“Acquired Characteristics”
Darwin’s Observations
• animals on the coast of South America that
resembled those on the nearby islands
evolved differences or “descended with
modification”after separating from a
common ancestor.
Section 1
The Theory of Evolution by Natural Selection
Darwin Proposed a Mechanism
for Evolution continued
•Growth of Populations :
•Darwin was influenced by Thomas Malthus, who
wrote that populations tend to grow as much as the
environment allows.
•Darwin’s book The Origin of Species
Section 1
The Theory of Evolution by Natural Selection
Evolution by Natural Selection
•Natural Selection
•Natural selection is differential reproductive success
and natural selection leads to adaptations in a
population.
•Darwin’s Theory
•Darwin proposed that natural selection favors
individuals that are best able to survive and
reproduce and this causes populations to evolve.
Section 1
The Theory of Evolution by Natural Selection
Darwin’s Ideas Updated
•Change Within Populations
•Natural selection causes the frequency of certain
alleles in a population to change over time.
•Species Formation
•Under certain conditions, change within a species
due to reproductive isolation can lead to new species.
Darwin’s Ideas Updated
The Tempo of Evolution
Gradualism is a process of evolution in
which speciation occurs gradually
Punctuated equilibrium is a process in
which speciation occurs rapidly between
periods of little or no change.
Section 2
Evidence of Evolution
Objectives:
•Describe how the fossil record supports evolution.
•Summarize how biological molecules such as
proteins and DNA are used as evidence of evolution.
•Infer how comparing the anatomy and development
of living species provides evidence of evolution.
Section 2
Evidence of Evolution
The Fossil Record
•Formation of Fossils Evidence of orderly change
can be seen when fossils are arranged according to
their age.
Evidence:
Fossils
Section 2
Evidence of Evolution
Anatomy and Development
•Vestigial Structures
•Reduced or nonfunctional vestigial structures, such
as hind limbs in whales
•Homologous Structures
• Homologous structures, structures in different
organism that indicate a shared ancestry, include the
vertebrate forelimb.
Vestigial Structures
Vestigial Structures: Whale legs
Vestigial Structures: Snake legs
Homologous Structures
Embryological Similarities
Vertebrates: animals having a backbone.
Embryological Similarities
Section 2
Evidence of Evolution
Biological Molecules
•Proteins:
• Differences in amino acid sequences are greater
between species that are more distantly related than
between species that are more closely related.
•Nucleic Acids :
•Differences in DNA sequences are greater between
species that are more distantly related than between
species that are more closely related.
Section 3
Examples of Evolution
Objectives:
•Identify four elements in the process of natural
selection.
•Describe how natural selection has affected the
bacteria that cause tuberculosis.
•Relate natural selection to the beak size of finches.
•Summarize the process of species formation.
Section 3
Examples of Evolution
Natural Selection at Work
•Factors in Natural Selection
•Individuals that have traits that enable them to
survive in a given environment can reproduce and
pass those traits to their offspring.
•Evolution of Antibiotic Resistance
•Experiments show that evolution through natural
selection has occurred within populations of
antibiotic-resistant bacteria, such as the bacteria that
cause tuberculosis.
Section 3
Examples of Evolution
Formation of New Species
•Speciation
•Speciation begins as a population adapts to its
environment.
•Forming Subspecies
•Populations of the same species that differ genetically
because of adaptations to different living conditions are
called subspecies.
•Maintaining New Species
•Reproductive isolation through reproductive barriers
keeps species from breeding with one another.
Periodical “Evolution by Design”
Discover, March, 2009
A revolution in biotechnology which
allows scientist to alter genes may bypass
natural evolution.
Sperm and egg cells have been created
from skin cells
Pluripotent stem cells have been created
from skin cells. These can develop into any
type of human cell.
Periodical “Evolution by Design”
Discover, March, 2009
Genetic engineering is changing the human
genome.
Insertion of whole , new chromosomes
may soon be possible.
“Enhancement Evolution” might replace
natural evolution.
“Deliberate Selection” might replace
natural selection.
Video: Evolution
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