Download Darwin`s Theory of Evolution On the Origin of Species

Darwin’s Theory of Evolution
15.3 Darwin Presents His Case
Thursday, February 14, 2013
The Nora School
Biology
955 Sligo Avenue
Silver Spring, Maryland 20910
Period ________
On the Origin of Species
•
•
Darwin filled
notebooks with his
ideas about species
diversity and the
evolution process.
He shelved his
manuscript for years
and told his wife to
publish it in case he
died.
The Nora School
Biology
955 Sligo Avenue
Silver Spring, Maryland 20910
Period ________
Darwin’s Publication
•
In 1858, Darwin received a
short essay from naturalist
Alfred Wallace.
In 1859, Darwin published his
book, On the Origin of
Species.
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•
•
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Proposed a mechanism for evolution
called natural selection.
Presented evidence that evolution has
been taking place for millions of years—
and continues in all living things.
Biology
Period ________
1
Artificial Selection
•
•
•
Variations were thought to
be unimportant, minor
defects.
Darwin argued that this
variation mattered.
Artificial selection is the
selection by humans for
breeding of useful traits from
the natural variation among
different organisms.
The Nora School
Biology
955 Sligo Avenue
Silver Spring, Maryland 20910
Period ________
Inherited Variation and
Artificial Selection
The Nora School
Biology
955 Sligo Avenue
Silver Spring, Maryland 20910
Period ________
Evolution by Natural Selection
•
The struggle for
existence means
that members of
each species
compete regularly to
obtain:
– Food
– Living space
– Other necessities of life.
•
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
This was central to
Darwin's theory of
evolution.
Biology
Period ________
2
Evolution by Natural Selection
•
•
•
Individuals not well suited to
their environment either die or
leave few offspring.
Individuals better suited to their
environment survive and
reproduce most successfully.
Because of its similarities to
artificial selection, Darwin
referred to the this phenomena
(Survival of the Fittest) as
Natural Selection.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Biology
Period ________
Evolution by Natural Selection
•
Natural selection results in changes in the
inherited characteristics of a population.
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–
•
•
Different structures
Establish different niches
Occupy different habitats.
Each living species has descended, with
changes, from other species over time
(Descent with Modification)
Implies Common Descent from one
ancestor
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Biology
Period ________
Evidence of Evolution
• Darwin argued evolution has been going on
for millions of years and that evidence could
be found in several places.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Biology
Period ________
3
The Fossil Record
•
By comparing fossils from older rock
layers with fossils from younger
layers, scientists could document that
life on Earth has changed over time.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Biology
Period ________
Geographic Distribution
•
•
Darwin decided that all
Galápagos finches could have
descended with modification from
a common mainland ancestor.
Similar species living on different
continents could also descended
from different ancestors.
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–
However, similar ecological conditions,
resulted in exposure to similar
pressures of natural selection.
Therefore, different animals ended up
evolving certain features in common.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Biology
Period ________
Homologous Structures
•
•
Structures that have different mature forms but develop
from the same embryonic tissues are called homologous
structures.
Similarities and differences in homologous structures help
group animals according to how recently they last shared a
common ancestor.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Biology
Period ________
4
Vestigial Organs
•
The organs of many animals are so
reduced in size that they are just vestiges,
or traces, of homologous organs in other
species.
The Nora School
Biology
955 Sligo Avenue
Silver Spring, Maryland 20910
Period ________
Similarities in Embryology
•
•
The early stages, or
embryos, of many animals
with backbones are very
similar.
The same groups of
embryonic cells develop in
the same order and in
similar patterns to produce
the tissues and organs of all
vertebrates.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Biology
Period ________
Summary of Darwin’s Theory
1.
2.
3.
4.
5.
6.
7.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Organisms differ.
Some of this variation is heritable.
Organisms produce more offspring
than can survive.
They compete for limited
resources.
Individuals best suited to their
environment survive and reproduce
most successfully.
Natural selection causes species to
change over time.
All living species are descended
with modification from ancestral
species.
Biology
Period ________
5
Section 15.3 Assessment
1. How is Artificial Selection dependant
on variation in nature?
2. The theory of evolution by natural
selection explains, in scientific terms,
how living things evolve over time.
What is being selected in this
process?
3. What types of evidence did Darwin
use to support his theory of change
over time?
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Biology
Period ________
6