Download Darwin in the Galapagos Islands

Darwin’s Theory of
Evolution
The Origin of Species by Natural
Selection
Who was Charles Darwin?
Journey of the Beagle
• 1831 – 1836
• Darwin was
appointed companion
to the captain, and
self-appointed
naturalist.
• He spent time ashore
collecting plant and
animal specimens
Ideas that shaped Darwin’s thinking
• James Hutton (1788) first suggested that
the Earth is millions (not thousands) of
years old. Geological processes operate
extremely slowly.
• Charles Lyell (1833) added that processes
can be observed today, and must also
explain past events.
• Thomas Malthus (1798) observed that
more organisms are born than can be
supported. Populations are kept in check
by famine, war, and disease
Jean-Baptiste Lamarck
• (1809) theory of the
inheritance of acquired
traits
- parts used or disused
could be changed during an
organism’s lifetime, and
passed on to offspring.
* First to recognize that
organisms change over
time; are adapted to their
environments, and are
descended from common
ancestors
Alfred Wallace
• In 1858 he wrote
to Darwin,
proposing the
same idea of
evolution by
natural selection
• In 1859 Darwin
published his
theory of evolution
by natural selection
Darwin in the
Galapagos Islands: DIVERSITY
DIVERSITY
Darwin’s observations:DIVERSITY
• 68 different
species of
beetles in a
Brazilian
rainforest in
one day
• 13 different species of finches on the
Galapagos Islands = DIVERSITY
Diversity:
• It is estimated that there are more
than 20 million different species on
the Earth today.
• 99.9 % of all species that have ever
lived are now extinct.
• How do we explain such diversity,
and why have so many organisms
disappeared, and so many new ones
appeared?
Adaptation: any inherited
characteristic that increases an
organism’s chances for survival
Adaptions
Camouflage
Adaptions
Mimicry
Fitness: the physical traits and
behaviors that enable organisms to
survive in their environment.
a long neck, a sharp
bill and bright blue
feet.
 elaborate mating
ritual : the male
raises one blue foot
in the air, then the
other, as he struts in
front of the female.

30 years after the voyage, Darwin
published his book (1859): The
Origin of Species by Natural
Selection
Modern organisms were produced by a
process of evolution (change over time)
 All organisms have arisen from preexisting
organisms
 If you look back far enough in time, you
will find common ancestors

Theory of Natural Selection
Variation: genetic variation in a population
 Heritability: genes are inherited
 Overproduction: populations produce
more organisms than can survive
 Reproductive Advantage: Organisms with
traits suited for environment survive and
reproduce more.

SURVIVAL OF THE FITTEST
Artificial Selection
Selective Breeding
Breeder chooses traits and
breeds organisms with
these traits in order to
produce desired
offspring
Domesticated dogs bred
from wolves
Wolves with selected
traits bred together over
generations to produce
different breeds
Evolution of Resistance
Ability to break down certain chemicals (antibiotics,
pesticides) into harmless molecules
 Bacteria have evolved resistance to many antibiotics
due to overusage by humans
 Organisms with genes to be resistant to chemicals
survive and reproduce passing on resistance to their
offspring

The faster an organism
reproduces,
the faster its populations can
evolve
Evidence for evolution:
1. age of the Earth (4.5 bya)
• James Hutton (1788):
natural processes
such as rain, cold,
heat, wind,
volcanoes, operate
slowly, over millions
of years
• Charles Lyell (1830):
forces operating on
the Earth can still be
seen today.
Evidence for evolution:
2. fossils
• Fossils: preserved
remains of ancient
organisms
• Show great
diversity of
organisms that no
longer exist
• Show gradual and
successive
changes
a. Transitional fossils
• Show link between
species; have
features shared by
different species
• Archaeopteryxfeathers of bird; teeth,
bony tails of reptiles
b. Fossil record
• All fossils of living
organisms that have
been found
• Show ancient species
share similarities with
modern species
• Not all organisms
have fossilsincomplete
c. Law of Superposition
–Younger rock layers on top of older
–Sedimentary Rock- fossils form easily
d. (Radioactive dating)
Uranium 238
4.5 billion
years
Potassium 40 1.3 billion
years
Carbon 14
5770
years
• Radioactive elements decay at a steady
rate.
• A half-life is the amount of time needed for
half of the atoms in a sample to decay.
Evidence from living organisms:
3. embryological
vertebrate embryos are similar due to
similar genes, common ancestor
Evidence from living organisms:
4. Morphological Evidence (Anatomical):
a. Homologous Structures
Structures are similar, functions are different
Must have evolved from a common ancestor
Evidence from living organisms:
4. Morphological evidence:
b. vestigial organs
Organs inherited
from ancestors,
but having no
apparent function
 Organs that
appear in the
embryo but are
lost later in
development

Evidence of Evolution:
4. Morphological evidence:
c. Analogous Structures
• Structures with the same function, but different
•
•
structures
Not closely related animals
Environment controls adaptations
Evidence in living organisms:
5. Biochemisty: chemical compounds
 All
living
organisms have
some
compounds in
commmon
 DNA
and ATP
 RNA
 Cytochrome
C
Evidence in living organisms:
6. Geographic Distribution
Organisms in different parts of the world
are very similar
 Due to separation of continents and
organisms evolving adaptations to their
environment

Evidence in living organisms:
6. Geographic Distribution