Transcript Evolution

Evolution
How does that work
again?
Origins of Life
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Scientists have long
wondered where life
first began.
Fossil and chemical
evidence has led to
the knowledge that
single-celled
organisms were the
first forms of life in an
atmosphere full of
toxic gases.
So what happened after that?
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From that soup, life began and continued.
The early organisms continued to reproduce
and made offspring that looked or acted
different.
We all started using proteins, breaking down
sugar, etc.
Humans, though, still had a lot to learn about
how organisms reproduced to make new ones.
Take a look at how we thought
bees were made
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Weird huh? Yes, we were
that stupid once!
But think about it: we
knew that bees weren’t
human and didn’t
reproduce sexually, so this
was a good replacement.
Experiments by Redi and
Pasteur determined that
organisms must come
from other living
organisms.
Experiments
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Redi proved that flies
do not come from
rotting meat.
Pasteur proved
conclusively that
spontaneous
generation does not
occur.
Natural Selection
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Darwin’s travels led him
around the world. His
most important work was
done in the Galapagos
islands.
In studying the endemic
organisms and comparing
them to those he already
knew, he began to
wonder why they were so
similar.
Natural Selection
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Natural selection is
not evolution in itself.
Natural selection gives the means by which
evolution occurs.
In other words, scientists think that
evolution occurs because of natural
selection. All of the evidence points in
this direction.
Natural Selection
Darwin’s ideas had four basic steps:
1.
Organisms produce more offspring than can
survive.
2.
In any population, individuals have variations.
3.
Individuals with certain useful variations
survive in their environments and pass these
variations on to their children.
4.
Over time, these variations make up most of
the population. These organisms can look
completely different from their ancestors.
So What Does This Mean?
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It means that organisms have developed
special adaptations that are necessary to
survive in their environments according
to natural selection.
Can you think of any organisms that
have special adaptations to help them
survive?
This sounds fishy to me, Bass!
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Remember, evolution is a science and only
presents what we know so far!
By combining what we know about early Earth
and how natural selection works, we can make a
hypothesis about how life got here.
Do we know how life got started – NO! That’s
why I can’t say your religion is wrong!
But we do have some ways to know that we all
came from a similar origin.
Evidence for evolution
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Organisms can
develop metabolic
changes over time.
Bacteria and viruses
often evolve and our
remedies won’t be as
effective.
Artist rendition of
flesh eating disease.
Evidence for Evolution
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What kind
of animal
is this?
Mimicry
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When an organism has
a structural adaptation
that makes it appear
like another organism.
These organisms have
mutations that allow
them to act like other
organisms.
Do you
see an
animal
here?
Here are some more examples
Evidence for Evolution: Coloring
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Camouflage
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When an organism has
an adaptation that lets
them blend in to their
surroundings.
These organisms have
mutations that let
them look like other
things in the
environment.
Where is
the lizard?
Who’s here?
Other Evidence
Fossils are remains of
organisms from long
ago and are found in
different layers of
rock.
Fossils can be any of
these:
C. Trace
A. Cast
B. Imprint
Fossils
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We know that there were
other organisms on Earth
because we have found
their fossils.
We can find their
approximate age by
dating the rock they were
found in.
Each fossil tells us
something about the
organism.
What we’ve learned from fossils
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We know that the oldest living organisms
came from the sea.
We know that there was a period when all
life died out (~ 144 million years ago).
We know where certain organisms lived
and what earlier ancestors looked like.
Anatomy
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There are two types of structures that suggest
evolution.
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Homologous structures:
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Remembering that homologous means same, this is when
organisms have the same or similar body structures. For
example, most animals have hands.
Anatomy
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Analogous structures
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These structures are found in different animals and are not
similar in structure, but have the same function.
Embryology
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Embryology deals with the development of
the embryo. Take a look at the next slide.
What kinds of organisms do you see?
What do you notice about them?
Although the pictures here are
exaggerated and they are no longer used
as proof by itself, there are still many
similarities between the species.
Biochemistry
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Biochemistry evidence for evolution is based on
DNA evidence.
Scientists use electrophoresis to determine
similarities between organisms.
Organisms with similar DNA are more closely
related.
Biologists used this information to create the 6th
Kingdom (Archaebacteria) because they were so
different from other kinds of bacteria.
So why did you make us study
genetics and what does it have to
do with evolution?
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Remember that organisms with useful
variations survive and pass on their genes.
Useful variations are those that help them
hide from predators or get food.
These variations are differences in their
genes.
What do genes have to do with it?
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Each species has a specific group of
characteristics or a gene pool.
As organisms breed, they pass along these
genes. The genotypes don’t change much which
means the phenotypes don’t change much.
If a new genotype (a different phenotype) is
introduced to the population, it could possibly be
bred out of the gene pool if it doesn’t help
survival. If it helps survival, then it may stay in
the gene pool.
So what?
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New variations or phenotypes are caused
by different genotypes that weren’t found
in the gene pool before (either by
mutation or an organism new to the area).
If these new genotypes are popular and
are bred into the population, they will stay
in the gene pool and you’ll begin to see
them more.
I still don’t get it, Ms. Bass!
Family 1
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Okay, what would happen if BB
bb
a group of blond haired
people moved to Asia and
Bb
people thought that blond
hair was cool?
When the parents have
children, they will introduce
blond hair into the gene pool.
(Bb)
If children from these
families have children, there
is a possibility that they could
have blond hair, introducing
the blond phenotype to the
population.
Family 2
BB
bb
Bb
bb