Transcript Document

NOTES – Evolution
Charles Darwin – the “Father of Evolution”
The Diversity of Life
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Millions of different types of organisms live
on the earth today
They differ in structures, behaviors, and
genes but are also alike in many ways
Where did all of these organisms come
from?
How do scientists explain the differences
and similarities in living things?
The Work of
Darwin
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From 1831 to 1836, British scientist Charles
Darwin sailed around the world as a ship’s
naturalist
He observed many living things and formed
ideas about evolution
In 1859, Darwin published On the Origin of
Species, a book in which he explained his ideas
about evolution and natural selection
Darwin’s work formed the basis for the study of
evolution and his ideas are still influential today
What is a species?
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Species – a group of organisms that are
physically similar and can produce offspring that
are then able to reproduce themselves
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EX. The Eastern
Grey Squirrel (1
of about 280
squirrel species)
What is a species?
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The goal of a species is to survive long
enough to reproduce a lot
A species that does not reproduce enough
is in danger of going extinct (disappearing
from the Earth forever)
The traits of a particular species are
determined by the genes of that species
What is a species?
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Population – a group of organisms of the
same species living in an area
Gene Pool – the combination of all the
versions (alleles) of all the genes in a population
of any species
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Many versions of genes = larger gene pool =
more difference between individuals
Few versions of genes = smaller gene pool =
less difference between individuals
A Population of Squirrels
Where did all the species on
the Earth today come from?
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Remember 2 important statements from the cell
theory:
1. All living things are made of one or more cells
2. All cells come from other cells
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This means that all cells must have come from
some group of original cells in the distant past
How can different species
come from the same cells?
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The simple answer: since the appearance
of the first prokaryotic cells about 3.5
billion years ago, some of those cells have
changed in enough different ways that
they now form all the different living
species
The branch of biology known as evolution
deals with this question
What is evolution?
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Evolution – Change in species over time
(changes in the gene pool of a species
lead to changes in the overall traits of the
species)
This sometimes leads to the formation of
new species (speciation)
Evolution says that species can change
over many generations of reproduction
Evolution happens to a species NOT to
individual organisms
What is the main idea of evolution?
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The main idea of evolution is that all
species are descended from the first living
organisms, which were prokaryotic
bacteria
Species alive today share common
ancestors some time in the past
The more closely related 2 species are,
the more recent their common ancestor
existed
Common ancestor – a species that
existed in the past that split into 2 groups
which eventually became 2 different
species
What is the main idea of evolution?
What is the main idea of evolution?
What is the main idea of evolution?
What is the main idea of evolution?
What is the main idea of evolution?
What is the main idea of evolution?
What is the main idea of evolution?
A few steps in the history of species…
mya = million years ago (1,000,000)
1. 5 mya – common ancestor of
humans and chimpanzees
2. 70 mya – common ancestor of
primates (humans, apes,
monkeys) and grazing animals
(horses, etc.)
3. 250 mya – common ancestor
of mammals and reptiles
4. 450 mya – common ancestor
of vertebrates (animals with a
backbone) and invertebrates
(animals without a backbone)
5. 1,000 mya – common ancestor
of animals and plants
3,500 mya – common ancestor
of all life, the first prokaryotic
cells
A few steps in the history of species…
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4,500 mya – the formation of the
Earth
13,000 mya – the formation of the
Universe
If you compare the history of life on
Earth to one year, the first bacteria
arrive at 12:00 AM on January 1st
and the first humans appear at 11:59
PM on December 31st – 364 days, 23
hours and 59 minutes later – We
haven’t been here very long!