DARWIN’S VOYAGE - Piscataway Township Schools

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Transcript DARWIN’S VOYAGE - Piscataway Township Schools

• When people think “EVOLUTION,”
they often think of the phrases
“Only the strong survive” or “survival
of the fittest.”
– Based on your reading for homework,
what do these phrases mean to you?
– How do you think it applies to other
species of animals besides humans?
• Charles Darwin –naturalist
aboard a ship from
England that sailed around
the world.
– his job was to learn about
all the living things that he
saw on the journey.
– His ship, the HMS Beagle,
spent a lot of time on a
chain of islands called the
Galapagos Islands.
• His observations of living things, fossils, and
the characteristics of all the organisms he
saw on the Galapagos islands led to some of
the most basic theories about evolution
• While on the voyage Darwin was
amazed by the variety of living things
he saw.
• Today scientists have identified more
than 1.7 million species of organisms
and not all living things have been
• A species is a group of similar
organisms that can mate with each
other and produce fertile offspring.
Darwin’s Tools Were Simple
•Magnifying glass
•Glass bottom bucket
•Notebook and pencil
•He observed organisms living on the island as
well as studied fossils that were left behind
from long ago.
•Fossil: Preserved remains or traces of
organisms that lived in the past
•Darwin found fossils that were similar to the
bones of sloths living on the island now, except
they were much larger. He wondered what
happened to these giant animals.
• On the Galapagos
Islands Darwin saw
the largest amount
of diversity. He
saw: giant
tortoises, sally
light-foot crab,
blue footed
boobies, seals
covered with fur,
and lizards that
only ate cacti.
Many of the plants and animals on the
islands were similar to organisms Darwin saw
on the mainland of South America.
and plants.
• Darwin inferred
that some species
came to the islands
from the mainland.
• Maybe they were
taken there by the
• Once on the
islands they
There were also important differences between
organisms on the islands and those on the mainland.
• Cormorants on the
mainland could fly,
those on the
islands could not.
• Iguanas on the
islands had large
claws and iguanas
on the mainland
had small ones.
Observe the Claws
Galapagos Islands
There were even differences
between the islands!
• The tortoises on one
island had domeshaped shells, while
on another island they
were saddle-shaped
DO NOW - Discussion
• Some insects look just like sticks. How
could this be an advantage to the insects?
How could this trait have evolved through
natural selection?
• Darwin also noticed
differences in finches
on the islands.
• There beaks were
suited towards their
Adaptation – a trait that
helps an organism survive
and reproduce.
– Which two do you think
were adapted to eat
– Which two do you think
were adapted to eat
• Beak shape is an
example of an
Based on these two
pictures, what adaptations
do you see?
• Darwin studied his
observations for many
years. He thought that the
organisms arrived on the
islands and faced
conditions that were
different from those on
the mainland.
• He concluded that the
species must have gradually
changed over generations
and became better adapted
to their new conditions
• The gradual
change in a species
over time.
How does the environment
select organisms to survive
• Individuals with helpful
variations will allow
them to survive and
reproduce possibly
passing that helpful
allele to their offspring.
• Nature selects the ones
with better variations
while unfavorable
variations disappear.
Natural Selection
• Process by which
individuals that are
better adapted to
their environment
are more likely to
survive and
reproduce than
other members of
the same species.
Darwin Hypothesized That There
are THREE Factors that Can
Effect Natural Selection
Variations in the species
There are many factors that
affect natural selection
• Overproduction –
Most species
produce more
offspring than
could possibly
– Not enough food,
water, or living
There are many factors that
affect natural selection
• Competition – The
offspring must
battle indirectly
with each other to
There are many factors that
affect natural selection
• Variations –
individuals of the
same species.
• HOW do variations
and natural
selection work to
change a species
over time?
Variations acted on by
Natural Selection
• Suppose the
climate in an area
becomes much
drier than it was
before. What
kinds of variations
in the area’s plants
might be acted on
by natural
Can a change in the environment
effect survival of an organism?
• YES!
• An organism more suited for the
environment is “selected” by nature to
survive, reproduce, and pass on its helpful
• When people think “EVOLUTION,” they
often think of the phrases, “Only the strong
survive” or, “Survival of the fittest”. How
do these phrases describe the concept of
natural selection?
• Imagine that Conackamack is one of the
islands that Darwin is observing. What are
some selected traits that would benefit a
student and help them to survive and make
it to the high school and beyond? In other
words, what species of student would be
“strong enough to survive” our educational