Transcript Presentation

Descent With
Modification: A
Darwinian View of Life
Big Ideas Explored
in this Unit:
 Big Idea 1: The process of evolution drives the diversity
and unity of life.
 Big Idea 3: Living systems store, receive, transmit, and
respond to information essential to life processes.
Defining Evolution
 Evolution is defined as the
idea that living species are
descendants of ancestral
species that were different
from the present day ones.
 Other ways of saying this
are:
 Change in the genetic
composition of a population
from generation to
generation.
 Descent with modification.
Syncholora aerata as a model
for evolution
 Syncholora aerata (common
names are wavy-lined
emerald moth and
camouflaged looper)
 This illustrates three major
concepts about life:
 The ways in which
organisms are suited for
their environment
 The shared characteristics of
life
 The large diversity of life
Timeline of Historic Events
Why Darwin’s Ideas Appeared
Radical
 At the time the earth was
considered by most to be
relatively young (by
comparison to its actual age)
and Darwin challenged the
preconceived notions of that
time period.
Scala Naturae and
Classification of species
 Greek philosophers were

Many scientists believed that the
organisms that did well in their
environment were designed as such, and
thus used it as evidence for a creator.

One believer of this doctrine, Carolus
Linnaeus, sought to classify these
organism based on their complexity. He
called it “binomial nomenclature.”

Scala naturae was a very linear approach
to increasing complexity, whereas
binomial nomenclature took to more of a
netted approach and classified the
organisms based on similar
characteristics.

It would not be until Darwin argued that
relationships between organisms should
be based on their evolutionary
relationships.
amongst the first to suggest that
life changed over time.
 Aristotle being the most
influential, suggested that
organisms fit into certain “scale
of complexity” which he called
“scala naturae.”
 These ideas were quite
consistent with the Old
Testaments accounts of creation
which all organisms are created
individually by God in an
unchanging world and thus were
perfect.
Ideas about change over time
 Paleontology, which is the
 The first suggestions that
organisms were not static
came in the form of fossils.
 Fossils are typically found in
sedimentary rock, and as the
layers of sedimentary rock
slowly pile atop each other,
they form what are called
strata (stratum singular).
study of fossils, was partly
developed by Georges Cuvier.
 While observing strata in
Paris, Cuvier noticed that the
lower to strata was in the
ground, the more dissimilar
the fossils were from current
species. He also noticed that
some species would
disappear while ones not seen
in older layers suddenly
appeared.
Picking apart Cuvier’s merits and fault
in his explanations
 Cuvier attempted to explain
the sudden appearance and
disappearance of certain
organisms by suggesting that
major cataclysmic events
would wipe out one species,
and then another would
migrate there after that event.
 This is a logical thought
process, but it was contrary to
what other scientists of the
time were suggesting.
 The scientist in particular that
would have clearly rebuked
this suggestion was James
Hutton. Hutton suggested that
processes that occurred that
shaped the different strata
were not sudden, but
gradually changed, like a
valley being formed by a river.
 Incorporating Hutton’s work,
Charles Lyell stated that
processes that occurred in the
past operate at the same
speed then as they do today.
Lamarck’s Hypothesis on
Evolution
 Jeane Baptiste Lamarck,
was one of the first to
attempt to explain the
gradual process by which
organisms changed over
time. He would not be
remember for his
revolutionary thought
process, but rather by the
blunders made in
mechanisms to his approach.
Problems associated with Lamarck’s
Theory of Evolution
 Lamarck had a few major holes in his theory. They are:
 Organisms don’t have the inborn desire to become perfect.
 Evolution does not mean a species becomes better in some
way.
 Evolution does not proceed in a predetermined direction.
 Traits acquired in an organism’s lifetime cannot be passed on
to future generations.