Transcript Changes Over Time

Changes Over Time - Darwin’s Theory
Darwin’s Voyage
Charles Darwin sailed on the Beagle, from England to the
Galápagos Islands.
Changes Over Time - Darwin’s Theory
Overproduction and Variation
Natural selection is the process by which individuals who are
better adapted to their environment are more likely to survive
and reproduce than other members of the same species.
Changes Over Time - Darwin’s Theory
Competition and Selection
Variations among turtles make some of them better able to
survive. Turtles that survive to become adults will be able to
reproduce.
Changes Over Time - Darwin’s Theory
Relating Cause and Effect
In a graphic organizer, identify factors that cause natural
selection.
Causes
Overproduction: More offspring are
produced than can survive.
Variations: Members of the same species
differ.
Competition: Offspring compete for
survival.
Selection: Some variations make
individuals better fit for survival.
Environmental Change: Changes can
affect an individual’s survival.
Genes: Genes that help determine survival
are passed from parent to offspring.
Effect
Natural Selection
Changes Over Time - Evidence of Evolution
Homologous Structures
The structure of the bones in a dolphin’s flipper, a bird’s
wing, and a dog’s leg is similar. Homologous bones are
shown in the same color.
Changes Over Time - Evidence of Evolution
A Branching Tree
This branching tree shows how scientists now think that
raccoons, lesser pandas, giant pandas, and bears are
related.
Changes Over Time - Evidence of Evolution
Kaibab and Abert’s Squirrels
These two kinds of squirrels have
been isolated from one another
for a long time. Eventually this
isolation may result in two
different species.
Changes Over Time - Evidence of Evolution
Identifying Supporting Evidence
Evidence consists of facts that can be confirmed by testing or
observation. As you read, identify the evidence that supports
the theory of evolution. Write the evidence in a graphic
organizer like the one below.
Evidence
Fossils show that organisms that
lived in the past were very different
from organisms alive today.
Theory
Evolution
Patterns of early development
show that some different
organisms look similar during their
early stages.
Similar body
structures in different species
show that the organisms shared
a common ancestor.