Transcript - Bedford Academy

A Scientific Explanation of How All Living Things Came to
Be
 The Theory of Evolution is the Scientific explanation
for how all of Earth’s living organisms came to be, and
how we grew to be so different.
 This modern theory began around 150 years ago when
a British scientist named Charles Darwin made an
amazing discovery that revealed how creatures adapt
to their environments.
 Since that time the theory has grown in complexity
and strength.
 Before the Theory of Darwin different cultures had many
different ways for explaining the world and all the creatures
in it.
 Many believed that the creatures currently on the planet
were the only creatures that had ever been on the planet.
 However, people began to come across the remains of
bizarre creatures that did not exist anywhere on the planet.
 What they had found was the remains of creatures that
used to live on the planet. That revelation changed our
world view and eventually opened up the way for Darwin’s
ideas.
 Jean Léopold Nicolas Frédéric Cuvier, known as Georges
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Cuvier, was a French naturalist and zoologist.
Often viewed as the man who brought vertebrate
paleontology into existence Cuvier made a ground
breaking discovery while exploring the remains of a
mammoth: the mammoth was not a modern elephant!
In the 1790s he began comparing the remains of
mammoths to those of living elephants.
He soon discovered that not only were the mammoths very
distinct from the living elephants on the planet but that
the mammoth was an extinct species!!
Before then people simply thought they were a hairy
version of the living elephants.
 Mary Anning was a young English girl who would
become one of histories most famous fossil hunters.
 Around 1810, she discovered the first complete
specimen of an extinct ichthyosaur (a marine reptile
with a sharklike body).
 Discoveries like this one, and others made by her and
others, would confirm Cuvier’s idea that some animals
had become extinct.
 However, no one had an accurate Scientific sense of
the Earth’s age or from when in our past these
creatures had died out.
 In the 1800s, geologists began to realize that the layers in
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the Earth’s rocks were actually a record of time; particularly
sedimentary rock.
As new layers of sediment, lava, etc. were deposited on top
of older layers, a stack was created.
People began to realized that in some regions the layered
rock record was many miles thick.
More importantly, certain fossils only ever showed up in
certain layers. So collections of fossils were specific to time
periods.
Lastly, the further back in time you went, the more alien
looking the fossils became. Recent rock layers had
creatures that resembled modern animals but ancient
layers had very strange, unique looking specimens.
 Charles Darwin was a young English naturalist who
volunteered to serve on the Beagle; a ship on a map making
mission around the globe.
 He was to serve as the captain’s company at dinner and to
collect plant and animals species from the various places
they stopped.
 While at the Galapagos Islands, he collected tortoises and
birds.
 Later, when he was back in England, a bird expert noticed
something remarkable about some of the birds from this
region. Though they all looked different from one another,
they were in fact all finches.
 He began to explore how did one island’s finches
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become so different from one island’s finches.
Darwin formed a theory that they were all descended
from a species of mainland finches that had made
their way to the islands.
However, different islands had different food sources
available for the finches.
Therefore, in order to eat, the finches somehow
developed beaks suited to the food sources available.
But how? How could one species turn into several new
species?
 A species is a group of living things that can reproduce
(create new life) with one another but not with other
life-forms.
 E.g. Cobras can breed with other cobras, giraffes with
giraffes, but cobras and giraffes could not breed with
each other. In fact, just because a cobra is a snake does
not mean it can breed with all other snakes.
 So how can a new species be created. Well, that was
the easy part to discover as humans have been creating
new species for thousands of years.
 People have been creating new species of animals for
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thousands of years. The vast variety of dog breeds, cat
breeds and horse breeds are amazing examples of this.
Darwin had a barnyard hobby; he bred pigeons. This was
quite popular in his day.
People would find pigeons with certain traits (e.g. fluffy
feathered feet) and breed them with other pigeons with
that trait.
Some of the pigeons’ offspring would be normal, but some
would have fluffier feet.
Repeat this process for a few generations and you end up
with pigeons with ridiculously feathered feet.
 So if people could change a species in a few
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generations, could this occur naturally.
Darwin began to examine the creatures of the world
and came to the conclusion that it could.
Over a time a species could adapt to survive.
He refined his thoughts into what would become the
Theory of Natural Selection.
Fancy Pigeons
 1) All creatures struggle to survive and reproduce, but
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many fail.
2) Creatures that happen to be born with an
advantageous trait are the most likely to reproduce.
3) Parents can pass on their advantageous traits to
their offspring.
4) From there, all it takes is time.
**Vice versa – creatures born with disadvantageous
traits are less likely to survive and reproduce, so their
traits disappear.
 Darwin knew his ideas would be controversial and had
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difficulties with them himself.
For years he kept his ideas to himself.
However, another English naturalist called Alfred
Wallace made his own discoveries and formed his own
theory similar to Darwin’s theory of natural selection.
When they compared notes and realized that they had
both independently come to the same conclusion they
decided to share their idea.
In 1858 they presented their idea together to the
Scientific society.