Download In 1831, Charles Darwin sailed to the Galapagos islands aboard the

In 1831, Charles Darwin sailed to the Galapagos islands aboard the HMS Beagle.
He was hired to be the ship's naturalist, and he was required to document the plants
and animals observed on the HMS Beagle's five year journey.
Creationists: Believe God created all things at the same time
Evolutionists: Believe all living things come from a common ancestor having changed
very slowly over timeDarwin's Theory:
Darwin proposed the Theory of Natural Selection.
He proposed that over a very long period of time,
natural selection can lead to changes.
"Survival of the fittest" (competition) is part of this theory.
Those organisms best suited to an environment will
survive.
Helpful variations(mutations) and adaptations(traits
that help an organism survive) may gradually
accumulate in a species while unfavorable ones
may disappear.
Evolution
After Darwin returned to England he kept
thinking about what he had observed during
his five year journey aboard the HMS Beagle.
In the Galapagos Islands, Darwin had
observed adaptations that helped organisms
survive and reproduce in different environments.
Darwin reasoned that organisms that had arrived
on the islands faced conditions that were different
from those on the mainland. Over many generations,
the species became better adapted to the new
conditions.
These ideas came to be known as Darwin's Theory
of Evolution. Evolution is the gradual change in a
species over time. Darwin wrote these ideas in a book
entitled The Origin of Species.
What is Selective Breeding?
The process of selecting a few organisms
with desired traits to serve as parents
of the next generation
Selective breeding was commonly used by farmers
during Darwin's time.
Natural Selection:
What factors affect the process of natural selection?
1. Overproduction
This occurs when species produce many
more offspring than can possibly survive.
Since there is limited food, water, and living
space, offspring struggle to survive. Those
best able to survive will eventually pass on
their genes to their offspring.
2. Competition
Limited resources may create competition
within a species. Survival of the fittest results.
3. Variation
These variations are differences in traits
within a species. Sometimes certain traits
may be more favorable than others. Those
organisms displaying the favored trait will
survive and reproduce.
What evidence supports the theory of evolution?
Since Darwin's time, scientists have found that a great deal of evidence
supports the theory of evolution...
1-Fossil records
2-Embryology
3-Homologous structures
4-DNA
How do fossils form?
Most fossils form in sedimentary rock.
This occurs when animals die and become
buried in sediments.
Eventually the organism's remains
are replaced by minerals.
Vocabulary:
Petrified Fossils-A fossil formed when minerals replace
all or part of an organism. The remains
are actually changed into rock.
Mold-A type of fossil formed when a shell or other hard
part of an organism dissolves, leaving an empty space
in the shape of the part
Cast-A type of fossil that forms when a mold becomes
filled in with minerals that then harden.
Preserved Remains-Remains of organisms that become
preserved in substances such as ice or amber
How can you determine a fossils age?
1-Relative Dating
May be used to determine which of two
fossils is older.
It does not reveal a fossil's actual age.
2-Radioactive Dating
Allows scientists to determine the actual
age of fossils.
This technique measures the amount of radioactive
elements contained in a fossil.
Using the rate of decay for that element(half-life),
scientists can calculate a fossil's age.
What is half-life?
The time it takes for half the atoms of a sample
of a radioactive element to decay, or break down.
What is mass extinction?
When many types of organisms become extinct
at the same time.
What is gradualism?
A theory that evolution occurs slowly but
steadily.
What is punctuated equilibria?
Species evolve quickly over short periods
of time. These periods are separated by
long periods of little or no change.