Transcript of Evolutionary theory is a collection of scientific facts, observations, and hypotheses that helps...
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- Evolutionary theory is a collection of scientific facts,
observations, and hypotheses that helps explain the diversity of
life Evolution (change over time) is the process by which modern
organisms have descended from ancient organisms
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- During his travels Darwin made numerous observations and
collected evidence that led him to propose a revolutionary
hypothesis about the way life changed over time Whenever Darwin
went ashore, he collected animal and plant specimens to add to a
collection these helped support his theory Charles Darwin
contributed greatly to the understanding of evolution Darwin s
observations started when he joined the crew of the H.M.S. Beagle
this allowed him to travel the world
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- Most organisms were well suited for their environment There
were different ways organisms reproduced depending on where they
lived Darwin noticed certain patterns in diversity
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- In some places, the habitat seemed correct for a certain
species, yet they did not live there Even with similar
environments, different areas could house different animals
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- Some fossils looked similar to current living organisms Some
fossils looked nothing like Darwin had seen before what happened to
these species? Darwin also collected fossils which were important
to support his theory Fossils = the preserved remains of ancient
organisms
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- Even though the islands were close together, they had very
different climates Darwin noticed that land tortoises varied in
predictable ways from one island to another and that just by the
shell he could tell which island the tortoise came from While
visiting the Galapagos Islands Darwin was greatly influenced
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- Lonesome George
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- Galapagos Clip
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- The Bishop of Panama documented the officially first visit to
the islands in 1535 After leaving, they sent word to King Carlos V
of Spain, telling of the strange and foolishly tame wildlife and
the numerous galapagos (giant tortoises), and the name stuck. The
islands appeared on the map late in the 16th century as the
"Insulae de los Galopegos". In 1546, a group of insubordinate
soldiers of Pizzaro attempted what might have been South America's
first coup d'etat. With their limited maritime skills, the ruffians
attempted to arrive at the islands by sight. Peering through fog
and carried by currents, they felt as though the islands themselves
were moving, that they were enchanted and named them "Las Islas
Encantadas."
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- Many used the islands into way station and ports of call. The
buccaneers were not the only to use the islands as bases for
operations. In the 1800's, as South America became increasingly
independent of Spanish rule and open to trading, mercantile vessels
such as whaling ships came to the islands, especially Floreana. In
1807, Galapagos received its first resident. Irishman Patrick
Watkins arrived on the island of Floreana marooned at sea. For two
years he lived from growing vegetables, sometimes trading them with
passing whaling ships for rum. Eventually he stole a ship's
longboat, taking some of the sailors with him, however only he
arrived at Guayaquil on the continent. 1959, one hundred years
after the publication of Origin of the Species, Ecuador declared
the islands its first national park, preserving whatever land that
was not already settled for protection.
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- Darwin started to wonder if animals living on different islands
had once been members of the same species? Darwin also collected a
variety of specimens of finches while in the islands, but made no
major conclusions about them initially Darwin observed that the
characteristics of many animals and plants varied noticeably among
the different islands
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- The traditional view at the time was that the Earth and its
creatures were only created a few thousand years ago and nothing
had changed Fossil records started to challenge this view just
before Darwin left for his travels
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- Some scientists then said that there were several periods of
creation, and each one was preceded by a catastrophic event that
killed most living organisms Darwin realized his observations did
not fit into that idea of thinking
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- During Darwin s time, scientists made a new suggestion that the
Earth was very old & changed slowly over time Two scientist,
James Hutton and Charles Lyell helped recognize that Earth is
millions of years old, and the processes from the past are the same
processes that operate now
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- Hutton was a geologist that published work about the geological
forces that shaped the Earth Natural forces (wind, rain, heat &
cold) can all shape the rocks
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- Lyell was also a geologist and said that past events can be
explained by processes that can actually be observed because they
are still occurring Volcanoes, erosions, and earthquakes are the
same now as they were in the past
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- Given this new understanding of geology, Darwin was influenced
in two ways If Earth can change over time, could life change as
well? If Earth s changes are slow, would changes to life be slow
too?
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- The same year Darwin was born, Lamarck published his hypothesis
that by selective use or disuse of organs, organisms acquired or
lost certain traits during their lifetime. These traits could then
be passed on to their offspring. (use it or lose it!) Jean-Baptiste
Lamarck was one of the first scientists to recognize that living
things changed over time and that all species are descended from
other species
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- Part of Lamarck s idea was that organisms tried to move toward
perfection which is why they acquired new traits to make them more
successful Lamarck thought that acquired traits could be passed on
to offspring Ex. If you went tanning and were very tan, you would
have a very tan baby.
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- Malthus said that if the human population continued to grow
unchecked, sooner or later there would be insufficient living space
and food for everyone Darwin was also influenced by the work of an
English economist, Thomas Malthus
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- Darwin realized this reasoning applied to other plants and
animals even more so because they usually produce many more
offspring than humans do
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- Section 15-3: Darwin Presents His Case
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- An essay from Alfred Wallace, another naturalist, summarized
the ideas Darwin had been thinking about for 25 years and helped
push him to publish his work Darwin finally published On the Origin
of Species and proposed that natural selection was a mechanism for
evolution
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- Darwin learned that some of this variety was heritable passed
from parents to offspring An important insight for Darwin was that
members of each species vary from one another in important
ways
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- In artificial selection, nature provided the variation, and
humans selected those variations that they found useful Darwin
argues that this variety was important and that breeders could use
heritable variation to improve livestock & crops
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- Darwin compared artificial selection to nature and developed a
hypothesis to explain how evolution occurs: the struggle for
existence means that members of each species compete regularly to
obtain food, living space, and other resources
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- Adaptations make organisms more suited to their environment and
better able to survive Adaptations can be structural
characteristics, physiological processes, or even behaviors Fitness
= the ability of an individual to survive and reproduce in its
specific environment Fitness seemed to be the result of
adaptations
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- In survival of the fittest, individuals that are better suited
to their environment survive and reproduce most successfully
Natural selection is another term for survival of the fittest
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- Natural selection results in changes in the inherited
characteristics of a population these changes increase a species
fitness in its environment Natural selection cannot be seen
directly just as changes in a population over time
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- Natural selection produces organisms with different structures,
niches, and habitats as the environment changes In decent with
modification, Darwin suggested that each living species has
descended, with changes, from other species over time
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- If you go far enough back, there should be a common ancestor to
all living things this is known as common decent A single tree of
life links all living things This idea implies that all living
organisms are related to each other
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- Darwin argued that living things have been evolving on Earth
for millions of years. Evidence = the fossil record, geographic
distribution, homologous structures, and similarities in
embryology.
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- Arms, wings, legs, and flippers are similar in structure and
function, however they have been adapted in different environments
Another piece of evidence was the anatomical similarities among
body parts of animals with backbones
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- Homologous structures = structures that have different mature
forms but develop from the same embryonic tissues Homologous
structures can help scientists group animals according to how
recently they shared a common ancestor
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- Some homologous structures do not serve important functions and
may even be reduced in size these are known as vestigial organs Ex.
Whales pelvis; Wisdom teeth
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- Some variation is heritable Usually more offspring are produced
than can survive Because more offspring are produced, they compete
for limited resources Organisms best suited to their environment
will survive Natural selection causes change over time Species are
descended with modification from a common ancestor Summarizing
Darwin s Theory