Download Darwin and Natural Selection Notes

The Evolution of
Evolution
Historic ideas about organisms and how
they change over time
Aristotle
(384 - 322 B.C.)
● “Ladder of life”
● Nature is ordered from
lower to higher
● No vacant rungs
● No movement up or down
the ladder
● Included living and nonliving things
Jean-Baptiste Lamarck
(1744-1829)
● First scientist to propose
a mechanism for how
organisms change (1809)
● His idea: “Inheritance of
Acquired Traits”
● Greater use of a body
part would change it, and
the change would pass
on to the organism’s
offspring.
Use and Disuse
Organisms could alter
the size or shape of
organs
USE: giraffe stretching
its neck to reach taller
trees
DISUSE: if a bird did not
use its wings, then they
would decrease and
disappear
Lamarck’s Assumptions
1. Organisms have a
desire to change.
They have an
inborn urge to
better themselves
for their
environment.
Ex: Birds tried to fly and
eventually grew wings
because of their
efforts.
Lamarck’s Assumptions
2. Organisms can
change shape by
using or not using
their bodies.
Ex: The wings of a bird that
does not fly would get
smaller from
generation to
generation and the
wings would eventually
disappear.
Lamarck’s Assumptions
3. Organisms can pass on acquired traits to their
offspring.
Ex: If an animal developed muscles from lifting weights
during its lifetime, it could pass those muscles on to its
offspring.
Charles Darwin
(1809-1882)
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English naturalist
Traveled around the world on
the Beagle (1831); famously
stopped in the Galapagos
Islands
Observed many species and
fossils
Particularly studied finches,
tortoises, blue-footed boobies
Galapagos Islands
Small islands of the western coast
of S. America
Close together but different
climates
Smallest/lowest were hot, dry,
barren
Higher ones had more rain and
greater diversity of life
The Galapagos Islands (Ecuador)
Patterns of Diversity
Darwin was puzzled by species and
where they lived
No kangaroos in England
No rabbits in Australia
Collected fossils
 Why did species disappear?
How are they related to living
species?
Wildlife
Tortoises- the shape of the
shell could be used to identify
which island a particular
tortoise inhabited.
Finches – birds on different
island with different beaks
“Darwin’s finches”
● Darwin noticed that
finches were
different on each
Galapagos Island.
● He concluded that
the different finches
had descended
from a common
ancestor and had
changed to be able
to do and eat
different things.
“Descent with Modification”
After his studies, Darwin came up with 4 main ideas…
1. Individuals differ, and some of
this variation can be inherited.
2. Organisms produce more
offspring than can survive; thus
they have to compete for
resources, and only the most fit
will survive and reproduce.
3. The most fit organisms pass on
their heritable traits to their
offspring.
4. Species alive today are
descended with modification
(change) from their ancestors.
DEFINITIONS
 Natural Variation: differences among individuals of
a species
 Artificial selection: humans select those variations
that they find useful (dogs)
 Descent with modification: change in organisms
over time (many generations)
 Natural Selection: pressure the environment puts on
the specific traits that affects their ability to survive
 Evolution: change over time
 Common Descent: All living organisms are related
to one another
 Differential Reproduction: individuals that have
certain traits are more likely to survive and pass on
those traits (they become more frequent)
Therefore we now call Darwin’s idea ‘biological evolution”
Lamarck’s
explanation for
the giraffe’s
long neck:
Darwin’s explanation for
the giraffe’s long neck:
Thomas Malthus
(1766-1834) British clergyman
and scholar
His prediction:
 the human population
would grow faster than the
space and food supplies
needed to sustain it.
 The only checks on the
human population would
be war, famine, and
disease.
Influence of Malthus on Darwin
Malthus’ theory of population growth was
observed by Darwin in other animal
populations as well.
In nature, Darwin saw many organisms that
produced many offspring. Most died.
Darwin wondered, what determines which
individuals survive and reproduce?
James Hutton and Charles Lyell
British Geologists
 Hutton is considered the
“father of modern geology”
 Based on layers found in rock
structures, Lyell proposed that
Earth is millions of years old
 Lyell proposed that geological
features could be built up or
torn down over long periods of
time
Grand Canyon, Arizona
stressed that scientists
must explain past events
in terms of observable
processes (volcanoes,
erosion)
Influence of Geology on Darwin
After reading Lyell’s book,
Darwin was convinced that
Earth was old.
Darwin reasoned that if
geological phenomena could
change the earth, then life on
Earth could change as well.