Download Natural Selection - Los Banos Unified School District

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.
Darwin Proposed a Mechanism for Evolution
Science Before Darwin’s
Voyage

In 1809, Jean Baptiste Lamarck
Frenchman, studied medicine and
Botany,
Wrote many books about biology

In 1801 he suggested
Evolution occurs due to use/disuse
of features.
Acquired traits are passed on the
future generations
Thought evolution was linked to
environmental conditions
Section 1
The Theory of Evolution by Natural Selection
Darwin Proposed a Mechanism for Evolution
Charles Darwin
•Born in England, 1809
•Age 16: Went to Medical School in
Scotland (skipped class to collect
specimens)
•1827, sent to England to become a
minister, received a degree in theology
•1831, Age 22 he went as an unofficial
naturalist on HMS Beagle
•1836 finished survey of South American
coast on HMS Beagle
•Published Origin of Species in 1859
•Died in 1882
Darwin Proposed a Mechanism for Evolution
• Darwin’s Observations
•
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.
Thomas Malthus,
English economist
Section 1
The Theory of Evolution by Natural Selection
•Darwin’s Theory
•proposed that natural selection favors individuals that are
best able to survive and reproduce and this causes
populations to evolve.
•Natural Selection
•Natural selection is differential reproductive success and
natural selection leads to adaptations in a population.
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.
•Certain forms of the traits become more
common because more individuals carry
them.
•Mutations and sexual reproduction
increases variations
Darwin’s Theory Updated
Species Formation


Under certain conditions,
change within a species due to
reproductive isolation can lead
to new species.
Both squirrels have developed
different characteristics over
time
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 :structures in different
organism that indicate a shared ancestry, include
the vertebrate forelimb.
Analogous structures:
Structures of different organisms that have the
same function but not related by ancestry.
Darwin’s Theory Updated
•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
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 in Darwin’s Finches
Experiments show that evolution through natural
selection has occurred in beak size in Darwin’s
Finches.
• 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, MRSA (Methicillin resistant
Staphylococcus Aureus)
Section 3
Examples of Evolution
Formation of New Species
•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.