Transcript 1 Chapter 21 - Darwin

The process of evolution
drives the diversity and unity
of life
“Nothing in
biology makes
sense except in
the light of
evolution."
-- Theodosius Dobzhansky
March 1973
Genet icist , Columbia U niversit y
(1900-1975)
2006-2007
Darwin: Historical Man of
Mystery
 Plato & Aristotle (427 – 342 B.C.)
 Ideal organisms already adapted
perfectly to environment, so no
evolution
 Natural Theology (1700s)
 Creator specifically designed
all organisms
 Carolus Linnaeus created taxonomic
system to discover God’s order
 Georges Cuvier (1769-1832)
 Succession of fossils in
sedimentary rock – throughout
layers, species appear & disappear
 Believed in
catastrophism –
due to massive
changes of
environment
 James Hutton (1726-1797) –
gradualism – little changes add up
 Jean Baptiste Lamarck (1700s)
 Use & disuse (use creates
strength, disuse creates
weakness)
 Inheritance of acquired
characteristics (pass those
strengths to offspring –
ex:giraffe neck)
 Lamarck’s major contributions –
 Evolution explains fossil record
& current diversity
 Organisms adapt
to environment
The man, the legend, the icon!!
 1809-1882
 22 years old – HMS Beagle – on board
as “conversation companion” to
captain
 Voyage to chart coastline of S.A.
 Darwin interested in geographic
distribution of species, similarities, &
differences on Galapagos islands
Warbler finch
Cactus finch
Woodpecker finch
Sharp-beaked finch
Small insectivorous
tree finch
Small ground
finch
Cactus
eater
Medium
ground finch
Insect eaters
Seed eaters
Bud eater
Large
ground finch
Seed
eaters
Flower
eaters
Insect
eaters
 Finches were studied – very different
from island to island
 Beaks have “adapted” to environment
(food source/location)
 Natural selection – driving force of
evolution (“Descent with
Modification”)
 Biological diversity – product of
evolution
(a) Cactus eater. The long,
sharp beak of the cactus
ground finch (Geospiza
scandens) helps it tear
and eat cactus flowers
and pulp.
(c) Seed eater. The large ground
finch (Geospiza magnirostris)
has a large beak adapted for
cracking seeds that fall from
plants to the ground.
(b) Insect eater. The green warbler
finch (Certhidea olivacea) uses its
narrow, pointed beak to grasp insects.
 Unity of life explained by common
ancestor
 As life progressed, accumulation
of diverse modifications 
diversity of today
 Link to Linnaeus – more
taxonomic levels in common,
more recent shared ancestor
 Differential success in
reproduction
 Interaction between environment
& inherited variety of individuals
within a population
 Product is adaptation of
populations of organisms to their
environment
Differential
Success in
Reproduction
 Environmental interaction
 Ex: Peppered Moth
 Industrial melanism
Prior to Industrial Revolution
After the Industrial Revolution
 Antibiotic/chemical resistance
 Drug Resistant HIV
 Note: in another
environment, these
characteristics
might be considered
detrimental,
but in this environment, they are a
benefit for these organisms.
 Homology - similarity
of characteristics
from common
ancestor
Homologous anatomical structures
- Same structure, different function
 Remember….homologous
(common ancestor) NOT
analogous (similar function,
different structure)
Spines are
homologous
 Remember….homologous
(common ancestor)
NOT analogous
(similar function,
different structure)
 Vestigial structures
can help explain
link between
organisms
 Hip bones -snake
 Pelvic bones –
whales
 Human appendix
 Biogeography (geographic
distribution of species)
Biogeography
of the
Draco lineatus
complex
(the Lined
Flying Lizard)
 Convergent evolution
 Evolutionary change due to
similar environmental
pressures,
not a recent
common
ancestor
marsupial
mammals
placental
mammals
 Convergent evolution
 Fossil Record
550
500
Body size (kg)
450
Equus
400
350
300
250
Merychippus
200
150
Mesohippus
Hyracotherium
100
50
Nannippus
60 55 50 45 40 35 30 25 20 15 10 5 0
Millions of years ago
 Fossils can be dated by variety of
methods
 Age of rocks where fossil is found
 Isotope decay rate (carbon-14)
 Phylogenetic trees
 Mathematical calculations from
chemical properties or
geographical data
 Artificial Selection
 Influencing breeding based on
desired traits