Download Influences on Darwin

Homework
• Guided
reading Chapter 5 Section 2
Questions 11-19
Learning Targets
•I
can describe the 5 factors that
influenced Darwin in developing
the theory of natural selection.
The 5 W’s of
Charles Darwin
What influenced Darwin as
he developed his theory of
natural selection?
Jigsaw
•
Get into W groups from yesterday
•
Each group will read about one influence
•
As a group, come up with a brief one or two
bullet summary that could be used for our
notes.
Influences on Darwin in ISN – pg. 79
•
Glue ticket page down
•
Cut out the influence
statements
•
Glue the top tab to each ticket
to make a flap
Galapagos Islands &
Darwin’s Finches
One unique place Darwin visited on his HMS Beagle trip was the Galapagos
Islands. These islands are found 600 miles west of Ecuador in South America. Darwin
noticed that the animals and plants on the Galapagos Islands were a lot like those in
Ecuador. However, they were not exactly the same. The finches of the Galapagos
Islands, for example, were a little different from the finches in Ecuador. Additionally, the
finches on each island differed from the finches on the other islands. Darwin observed
that each different group of finches had different size and shape beaks and each
group had their own unique feeding habits.
After returning to England, Darwin puzzled over the animals of the Galapagos
Islands. He tried to explain why the animals seemed so similar to each other yet had so
many different adaptations. For example, Darwin learned that the 13 different finches
he had studied were each a separate species. Each species was adapted to their
own island habitat. Darwin hypothesized that the island finches were descended from
South American finches. The first finches on the islands may have been blown from
South America by a storm. A few individuals then migrated to neighboring islands
where they became isolated and exposed to a new environment. Over many
generations, the finches may have adapted to different ways of life on the different
islands which included the types of food each species of finch relied on for survival.
Eventually they became a separate species from the finches on neighboring islands.
Galapagos Islands
Galapagos Islands & Darwin’s Finches
Finches with different shape &
size beaks adapted from a
common ancestor
Charles Lyell & Geology
During Darwin’s journey on the H.M.S. Beagle he had an opportunity to
read the first volume of his good friend, Charles Lyell’s newly published book
The Principles of Geology. Lyell proposed in his book that the earth was very
old, that it had been slowly changing for millions of years, and that it was still
changing. These changes were taking place from weathering, erosion and
deposition. Most of the geologists of the time did not think the Earth was old
enough to allow for slow changes.
After Darwin returned home from his voyage, he spent a great deal of
time studying his notes, reading, and conversing with colleagues. He
incorporated the ideas from Lyell’s book about the earth into his own
thoughts on how life changes on earth. Using Lyell’s hypothesis, Darwin
concluded that gradual geologic changes over long periods of time could
cause life to change over that same long period of time.
Charles Lyell (1797-1875)
If the earth is
extremely old
and can
change
slowly
overtime, life
must change
with it.
Holstein
Jersey
Hereford
Selective Breeding
(Artificial Selection)
Darwin also studied the selective breeding of domestic animals and
crops. By selecting parents with the most desirable traits, farmers and
animal breeders can raise more desirable offspring. Breeders, for instance,
select cattle for increased milk production (Holstein), for high-butterfat milk
(Jersey), or for meat (Hereford). Animal breeders and farmers determine
which members of the population shall reproduce and which shall not.
Any domesticated plant or animal bred to produce desirable
characteristics is the result of artificial selection. The striking changes
produced over relatively few generations are powerful proof that species
can evolve. Darwin suspected that a selection process also occurred in
nature. If we can select for useful traits in organisms through selective
breeding; why can’t nature select traits in organisms that make them more
successful to survive.
Selective Breeding (animals)
Selective Breeding (plants)
If humans can select traits in species why can’t nature
Thomas Malthus &
Population Control
Shortly after Darwin returned to England, he read An Essay on the
Principles of Population by the economist Thomas Malthus. Malthus stated
in his essay that the human population was growing so fast that the supply
of resources could not keep up with demand. Malthus reasoned that the
human population tends to increase exponentially. For example, if each
pair of parents produced four children, the new generation would have 4
individuals to replace the 2 that had produced them. The next generation
would have 8, the next 16, and so on. This type of population growth will
eventually exceed its available resources. According to Malthus, when a
population exceeds its resources, disasters such as war, starvation, or
widespread disease limit the population’s growth.
Darwin recognized that Malthus’s principles applied not only to
humans, but to all species. Any species can produce many offspring. He
also knew that the populations of all species are limited by starvation,
disease, competition, and predation. Only a limited number of individuals
survive to reproduce. Darwin reasoned that the offspring of the survivors
inherit traits that help the offspring survive in their environment.
Thomas Malthus (1766-1834)
If humans over
reproduce so do
animals in nature,
but competition
keeps populations
in check
Alfred Wallace &
His Essay
In 1858, Alfred Wallace, a young British naturalist and explorer, wrote
Darwin from Malaysia while he was on an expedition. Wallace was seeking
Darwin’s advice about a theory he had. At the time Darwin was one of the
leading naturalists of England. However, Wallace had no idea of Darwin’s life
work on his theory of natural selection because Darwin had only shared his
ideas with a few close colleagues. Wallace sent Darwin an essay on his
theory and it turned out that Wallace had struck upon the theory of natural
selection that Darwin had been researching for 20 years. Wallace’s short
sketch was far from the massive body of evidence Darwin had collected, but
it’s core ideas were similar.
Darwin and Wallace agreed that Wallace’s essay should be published
along with a summary of Darwin’s theory. A year later, in 1859, Darwin
published his book under the title The Origin of Species. Darwin’s book was
fully supported by examples and 20 years of research and influence. His
theory on how evolution works was eventually accepted around 1865 by
most of the leading scientists of his time. Without Wallace’s prompting,
Darwin might never have published his theory during his lifetime.
Alfred Wallace (1823-1913)
Also came up
with Natural
Selection, but
didn’t have as
much evidence.
Evolution in the Galapagos
•
Watch video and complete
worksheet
•
Completed worksheet will
be collected
Exit Ticket
• Read
each learning target from
this week. For each target, place
a check in the appropriate
category for you based on your
understanding.
• Write
down one question you still
have about Charles Darwin and
his theory of evolution.