Ch. 19A Darwin S18.pptxjkhklhkhkkhkhkhikh

Ch. 19 Warm-Up
1. What do you remember about Charles
Darwin and his scientific ideas?
2. According to Campbell, what is the
definition of “evolution”?

Chapter 19
Descent with
Modification
Part A: Darwin & Natural
Selection

What you must know:
 Several examples of evidence for evolution
from different scientific disciplines and how
each supports change of populations over
time.
 The difference between structures that are
homologous and those that are analogous,
and how this relates to evolution.
 The role of adaptations, variation, time,
reproductive success, and heritability in
evolution.

Descent with Modification
Theme:
Evolutionary change is based on the
interactions between populations & their
environment which results in adaptations
(inherited characteristics) to increase fitness
Define: Evolution
1. Descent with modification (Darwin)
2. Change over time in the genetic composition
of a population from generation to
generation

Aristotle
 Species are fixed (unchanging)
 Scala naturae: life-forms arranged
on ladder of increasing complexity
Old Testament (Creationism)
 Earth ~6000 years old
 Perfect species individually designed by God for
particular purpose
Aristotle
384-322 BCE

Carolus Linnaeus = founder of taxonomy
 binomial nomenclature: genus,
species
 Domain – Kingdom – Phylum –
Class – Order – Family - Genus –
Species
 Dear King Philip Came Over For
Good Spaghetti
 Classification based on
anatomy & morphology
Carolus Linnaeus
1707-1778

Cuvier:
 Paleontologist – studied
fossils
 Deeper strata (rock layers):
very different fossils from
current life
 Opposed idea of evolution
 Boundaries between strata=
many living species
destroyed by catastrophic
event, then repopulated by
immigrant species
George Cuvier
(1769-1832)

Formation of sedimentary strata with fossils

 Hutton: geologic change results from slow &
gradual, continuous process
 Lyell: Earth’s processes same rate in past &
present  therefore Earth is very old
 Slow & subtle changes in organisms  big
change
Charles Lyell
1797-1875
James Hutton
1726-1797

Lamarck
 Published theory of evolution (1809)
 Use and Disuse: parts of body used 
bigger, stronger (eg. giraffe’s neck)
 Inheritance of Acquired
Characteristics: modifications can be
passed on
 Importance: Recognized that species
evolve, although explanation was
flawed
Jean-Baptiste de Lamarck
1744-1829

Malthus:
 More babies born than deaths
 Consequences of overproducing
within environment = war,
famine, disease (limits of
human pop.)
 Struggle for existence
Thomas Malthus
(1766-1834)

Charles Darwin (1809-1882)
 English naturalist
 1831: joined the HMS
Beagle for a 5-year research
voyage around the world
 Collected and studied plant
and animal specimens,
bones, fossils
 Notable stop: Galapagos
Islands

Darwin’s Finch Collection
The birds were all
about the same size,
but the shape and
size of the beaks of
each species were
different.

17
 Darwin waited 30 years before publishing his
ideas on evolution
 Alfred Russell Wallace – published paper on
natural selection first (1858)
 Charles Darwin (1859): On the Origin of
Species by Means of Natural Selection
 Mechanism for evolution is Natural
Selection
 Darwin didn’t use “evolution”, but rather
“descent with modification”

Descent With Modification
“I think …”
(Darwin’s sketch)
Organisms descended from an ancestor that lived in the
remote past

Natural Selection
Adaptations enhance an organism’s ability to
survive and reproduce in specific
environments
 Eg. Desert fox - large ears, arctic fox - small
ears

Therefore, if humans can create substantial
change over short time, nature can over long
time.
Natural Selection Artificial Selection
Nature decides “Man” decides
Works on individual Selective breeding
Inbreeding occurs
eg. beaks eg. dalmations

Key Ideas of Natural Selection:
 Competition for limited resources results in
differential survival.
 Evolutionary Fitness: Individuals with more
favorable adaptations are more likely to
survive and produce more offspring, and pass
traits to future generations
 If environment changes or individuals move to
new environment, new adaptations and new
species may arise.
 Populations evolve, not individuals.

Discovery Video: Charles Darwin

PBS: What Darwin Never Knew
Video Clip: 20:18 – 31:27

Ch. 19A Darwin S18.pptxjkhklhkhkkhkhkhikh

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