Download Natural Variation/Artificial Selection

Chapter
15.3 –
Darwin
Presents
His Case
Darwin’s Book
On The Origin Of Species By Means Of
Natural Selection
– In this book, Darwin presented his ideas of
natural selection (mechanism of evolution)
• Based on the ideas of Alfred Wallace
• Wrote an essay that summarized evolutionary
change
Natural Variation/Artificial
Selection
• Natural variation
differences among
individuals of a species
– Variation is inherited
• Artificial selection/selective
breeding
nature provides the
variation among different
organisms, and humans
select those variations that
they find useful
Struggle For Existence
• Members of each species compete
regularly to obtain food, living space, and
other necessary items for life
key factor in struggle is how well suited an
organism is to its environment
Survival Of The Fittest
Individuals that are better
suited to their
environments survive and
reproduce most
successfully
– Natural selection
• Over time, natural selection
causes a change in the
inherited characteristics of a
population. It directs these
changes in ways that
increase a species’ fitness in
its environment
Fitness and Adaptation
• Fitness –
– The ability of an organism to survive and
reproduce in its environment
 Result of adaptations
• Adaptations –
– Any inherited characteristic that increases an
organism’s chance of survival
can be physical, behavioral, or chemical
Descent With Modification
• Each living species has
descended, with
changes, from other
species over time
– Implies all living things are
related to other
• Common descent all
species, living and
extinct, were derived from
common ancestors
Darwin’s Evidence for
Evolution
Fossils
Anatomy
Embryology and Biochemistry
Genetics
Fossil Evidence
• Fossil trace of an organism living long
ago
– Mold or cast in a rock
• Bones or whole organisms are preserved
– Sand/ clay surrounds the dead organism
• Sediments turn into rock
• Some organisms remain unchanged, while in
others, minerals filter into the body > rock >
petrified
Fossils
The Fossil Record
• Layering gives clues to when organisms
lived.
– Lower layers= older and simpler body
structure
– Upper layers= more recent with complex body
structure
• Shows that strong similarities to existing
organisms
Fossil Layers
Homologous Structures
• Structures that have different mature
forms but develop from the same
embryonic tissue
– Exs: wings, flippers, arms
the more homologous structures shared,
the closer their relationship
Vestigial Organs
• Structures w/ no function
in the living organism,
but may be used in the
ancestors.
may be homologous
with still-used structures
in other related
organisms
Comparative Embryology
• Embryo early stages of a developing
plant or animal
• The study of developing organisms; shows
the relationships not obvious in the fully
grown organism.
Comparative Biochemistry
• The study of organisms on a biochemical
level
• Ex: Structure of hemoglobin- amino acid
sequence reveals relationships
• Provides the most fundamental evidence
for evolution
Genetic Evidence
• Population all organisms within a
breeding group
– Constant change over time due to mutation,
nondisjunction and fertilization.
• Production of new alleles and genetic
recombination could be called the raw
materials of evolution.
Direct Observation
• Change that occurs rapidly on a regular
basis can be observed directly.
• Reaction of penicillin to bacteria
• Evolution causes serious health problems
– Antibiotic/ disease resistance
– Flu
– Pests ( weeds and insects) resist chemicals