Download Natural Selection at Work Factors in Natural Selection

Chapter 13
The Theory of Evolution
Section 1: The Theory of Evolution by
Natural Selection
Section 2: Evidence of Evolution
Section 3: Examples of Evolution
Section 1
The Theory of Evolution by Natural Selection
Objectives:
•Identify several observations that led Darwin to
conclude that species evolve.
•Relate the process of natural selection to its
outcome.
•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.
•Darwin’s Observations Charles Darwin concluded
that 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.
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.
•Publication of Darwin’s Work Darwin and Wallace
independently came up with a mechanism for
evolution, natural selection, and this prompted
Darwin to publish his work.
•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.
•The Tempo of Evolution Gradualism is a process of
evolution in which speciation occurs gradually, and
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.
Section 2
Evidence of Evolution
Anatomy and Development
•Vestigial Structures Reduced or nonfunctional
vestigial structures, such as hind limbs in whales,
provide evidence of an organism’s evolutionary
history.
•Homologous Structures Homologous structures,
structures in different organism that indicate a shared
ancestry, include the vertebrate forelimb.
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.
•Evolution in Darwin’s Finches Experiments show
that evolution through natural selection has occurred
in beak size in Darwin’s Finches.
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. Newly
formed subspecies are on the road towards speciation.
•Maintaining New Species Reproductive isolation
through reproductive barriers keeps species from
breeding with one another.