Early scientists proposed ideas about evolution.
Evolution is the biological change process by which
descendants come to differ from their ancestors.
Early scientists proposed ideas about evolution.
A species is a group of organisms that can reproduce and
have fertile offspring.
There were many important naturalists in the 18th century.
Carolus Linnaeus: classification system from kingdom to
species
There were many important naturalists in the 18th century.
Jean-Baptiste Lamarck: environmental change leads to use
or disuse of a structure
Theories of geologic change set the stage for Darwin’s
theory.
Catastrophism: natural disasters such as floods and
volcanic eruptions have happened often during Earth’s
long history
Can lead to mass extinctions
Theories of geologic change set the stage for Darwin’s
theory.
Gradualism: the changes observed in landforms
resulted from slow changes over a long period of time
I. Darwin observed differences among island species.
1. Variation is a difference in a physical trait.
I. Darwin observed differences among island species.
1. Variation is a difference in a physical trait.
2. Galápagos tortoises that live in areas with tall plants have
long necks and legs.
I. Darwin observed differences among island species.
1. Variation is a difference in a physical trait.
2. Galápagos tortoises that live in areas with tall plants have
long necks and legs.
3. Galápagos finches that live in areas with hard-shelled nuts
have strong beaks.
1. An adaptation is a feature that allow an organism to better
survive in its environment.
– Species are able to adapt to their
environment.
– Adaptations can lead to genetic
change in a population.
II. Darwin realized species could adapt to their environment.
1. Fossil evidence included:
- Found fossils of extinct animals that resemble modern
animals.
- Found fossil shells high up in the Andes mountains.
III. Darwin observed fossil and geologic evidence supporting
an ancient Earth.
2. Geological evidence included:
- Saw land move from underwater to above sea level due to
an earthquake.
III. Darwin observed fossil and geologic evidence supporting
an ancient Earth.
Several key insights led to Darwin’s idea for natural
selection.
• Artificial selection is the process by which humans
select traits through breeding.
• Darwin noticed a lot of variation in domesticated plants
and animals.
neck feathers
crop
tail feathers
• Heritability is the ability of a trait to be passed down.
Several key insights led to Darwin’s idea for natural
selection.
• There is a struggle for survival due to overpopulation
and limited resources.
Several key insights led to Darwin’s idea for natural
selection.
Natural selection is a mechanism by which individuals that
have inherited beneficial adaptations produce more offspring on
average than do other individuals.
Several key insights led to Darwin’s idea for natural
selection.
Darwin proposed that adaptations arose over many generations.
Variation
The differences among individuals that result from
differences in the genetic material of the organisms
Can be inherited from a parent or occur from a mutation
There are four main principles to the theory of natural
selection.
VARIATION
Overproduction
While having many offspring raises the chance that some
will survive, it also results in competition between offspring
for resources.
There are four main principles to the theory of natural
selection.
OVERPRODUCTION
Adaption
Allows an individual to survive better than other individuals
it competes against in its environment.
There are four main principles to the theory of natural
selection.
ADAPTATION
Descent with Modification
More individuals will have the trait in every following
generation, as long as the environmental conditions
continue to remain beneficial for that trait.
There are four main principles to the theory of natural
selection.
• Natural selection can act only on traits that already exist.
• Structures take on new functions in addition to their
original function.
Natural selection acts on existing variation.
wrist bone
five digits
Evidence for evolution in Darwin’s time came from several
sources.
• Fossils provide evidence of evolution.
• Fossils in older layers are more primitive than
those in upper layers.
• The study of geography provides evidence of evolution.
– island species most closely resemble the nearest
mainland species
– populations can show variation from one island to
another
Evidence for evolution in Darwin’s time came from several
sources.
• The study of anatomy provides evidence of evolution.
Human hand Bat wing Mole foot
– Homologous structures are similar in structure but
different in function.
– Homologous structures are evidence of a common
ancestor.
Evidence for evolution in Darwin’s time came from several
sources.
Human hand
Bat wing
Mole foot
Fly wing
– Analogous structures are not evidence of a common
ancestor.
• The study of anatomy provides evidence of evolution.
– Analogous structures have a similar function.
Evidence for evolution in Darwin’s time came from several
sources.
• Vestigial structures are remnants of organs or structures
that had a function in an early ancestor.
• Ostrich wings are examples of vestigial structures.
Structural patterns are clues to the history of a species.