Download Descent with Modification

Descent with
Modification
Chapter 22
Rise of Modern Biology
A.
Pre-Darwin Ideas
Geology
 Larmark

B.
Charles Darwin
Darwin
 Wallace

Evolution: Change over time


A new era of biology began when Charles
Darwin published On the Origin of Species by
Means of Natural Selection
He made two points in The Origin of Species:
 Today’s
organisms descended from ancestral species
 Natural selection provided a mechanism for
evolutionary change in populations


Natural Selection: individuals with certain
heritable traits leave more offspring
EvolutionaryAdaptations : characteristics that
enhance survival
Pre-Darwin Ideas



Aristotle believed that all living forms could be
arranged on a ladder (scala naturae) of
increasing complexity with every rung taken
with perfect, permanent species.
In the 1700’s, the dominant philosophy, natural
theology the Creator had designed each
species for a purpose.
Carolus Linnaeus, a Swedish botanist,
developed taxonomy, a system for naming
species and grouping species into a hierarchy of
increasingly complex categories
Geology and the Gift of Time





Idea that the earth is young
(6000yrs)never go anywhere
Geologists can’t get young earth
Georges Cuvier (1769-1832)
James Hutton (1726-1796)
Charles Lyell (1797-1875)
Georges Cuvier(1769-1832)


Paleontology the study of fossils,
Documented the succession of fossil species in
the Paris Basin
 Recognized
that extinction had been a common
occurrence in the history of life

Catastrophism instead of evolution that
boundaries between strata were due to local
flood or drought that destroyed the species
then present
 Later,
this area would be repopulated by species
immigrating from other unaffected areas
James Hutton (1726-1796)
Scottish geologist
 Proposed that the diversity of land
forms (e.g., canyons) could be explained
by mechanisms currently operating
 A theory of gradualism  profound
change results from slow, continuous
processes

 Same
forces have always been there
erosion
Strata of sedimentary rock at the Grand Canyon
From 1.25 BY to 250my
Charles Lyell (1797-1875)


Scottish, friend of Darwin, good writer
Proposed a Theory of Uniformitarianism
 The
geological processes had not changed throughout
Earth’s history
 Same processes are operating today as in the past
Jeane Baptiste Lamarck (17441829)


1st comprehensive idea of evolution
Came up with the mechanisms for
evolution
Use and Disuse
 Inheritance of Acquired Characteristics
 Stressed adaptation

Influence on Darwin



Hutton’s and Lyell’s observations and theories
had a strong influence on Darwin
First, if geological changes result from slow,
continuous processes, rather than sudden
events, then the Earth must be far older than
the 6000 years
Second, slow and subtle processes persisting
for long periods of time can add up to
substantial change
The historical context of Darwin’s life
and ideas
Charles Darwin






Son of a wealthy physician
Sent to become one
Decided it was not for him
Entered the clergy studied natural theology-imprint
of God in nature
Professor recommends to go on a trip around the world
Journey on the HMS Beagle


Mission was to chart the poorly known stretches of the South
American coastline
He collected thousands of specimens of the exotic and diverse
flora and fauna of South America
Darwin’s Observations







The plants and animals of South America were very distinct from
those of Europe
Organisms from temperate regions of South America were more
similar to those from the tropics of South America than to those
from temperate regions of Europe
South American fossils more closely resembled modern species from
that continent than those from Europe.
While on the Beagle, Darwin read Lyell’s Principles of Geology
 Lead him to doubt the church’s position that the Earth was
static and only a few thousand years old
 He came to the conclusion that the Earth was very old and
constantly changing
By 1840, he had worked out the major features of a theory based on
his observations from his journey
Was hesitant to publish his ideas and was scared of the backlash
that they would cause
It wasn’t until he heard that another scientist, Alfred Russell
Wallace, was developing a theory very similar to his own that he
decided to publish.
Darwin and Wallace


Alfred Wallace
independently
developed a theory
of evolution by
natural selection
Both share the idea
of Natural selection
as a Mechanism of
evolution
“It is not the strongest of the
species that survives, nor the most
intelligent that survives. It is the
one that is the most adaptable to
change.”-Charles Darwin
Information that influenced
Darwin
 Charles
Lyell geologist proposed
that the Earth was very old and had
slowly been changing for millions of
years
 Thomas Malthus  economist  social
problems as a result of the
exponential growth of the human
population
 Artificial selection by breeders
Artificial Selection
Darwin’ Two Main Ideas
Descent with Modification
 Natural Selection and Adaptation

Descent with Modification




All present day organisms are related through
descent from unknown ancestors in the past
Descendents of these ancestors accumulated
diverse modifications or adaptations that fit
them to specific ways of life and habitats
The history of life is like a tree with multiple
branches from a common trunk
Closely related species, the twigs of the tree,
shared the same line of descent until their
recent divergence from a common ancestor
This evolutionary tree of the elephant family
is based on evidence from fossils.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Darwin’s Key Observations
1.
2.
3.
4.
Fossils & fossil records show that
organisms  simpler  complex
Overproduction of offspring
Limited supply of resources in an
environment
Survival in a limited environment
depends in part on features
inherited from parents
Natural Selection
 Individuals
whose inherited
characteristics adapt them best to
their environment are most likely to
survive and reproduce
 Basic
Mechanism of Evolution
Natural Selection
Natural Selection and Adaptation
Variations exist
 Many of these
variations are
heritable

Camouflage Evolutionary
Adaptation

A heritable trait that increases an
organism’s likelihood of surviving and
reproducing in its environment
Evolution by Natural Selection





Natural selection is the differential
reproductive success of among individuals
Variations exist; some represent adaptive
traits that increase reproductive success
Many of these are heritable
Over time, this can increase the adaptation of
organisms to their environment
Environmental changes may result in
adaptation of a species to these new
conditions.
Fitness
 Individual
organisms are
selected
 Populations evolve!
 Remember, individuals live or
die. They do not evolve!
Natural Selection in Action
Biston betularia : peppered
moth
Evolution of Drug Resistant HIV
3TC interferes w/ reverse
transcriptase
Evolution of Drug Resistance


A drug does not create a resistant pathogen
It selects for existing resistant pathogens
And so with evolution:
 Evolution does not create novel life forms
 Nature selects from existing variants
Evidence of Evolution
Evidence of Evolution
1.
2.
3.
4.
5.
Fossil Records
Comparative Anatomy
Embryonic Structures
DNA Homology
Biogeography
Fossils
 Remains,
traces or imprints of an
organism preserved in the earth’s
crust
Imprint
Mold
Cast
Petrified
Fossil Records
1.
2.
Fossils & the order in which they
appear in layers of rocks
Fossil records show that animals &
plants have appeared in a historical
sequence, fossils found in rocks of
different ages differ because life on
Earth has changed through time
Each Layer represents a
particular time period
Comparative Anatomy
The comparison of body structures in
different species
 Homologous Structures
 Analogous Structures
 Vestigial Structures

Ex: common descent evident in anatomical
similarities between species in the same
taxonomic group
Homologous Structures
Structures that are similar & have been
derived from a common ancestor, but
have been adapted to different
functions.
ex: humans, cats, whales, bats all
mammals
Whales’ flipper does not have the same
function as a bat’s wing

Homologous Structures
Analogous Structures
 Body
parts similar in function but
have different structures
Ex: wings of insects and birds
Vestigial Structures
 Body
parts
reduced in
size & appear
to serve no
function
Embryonic Structures
 Embryos
of closely related
organisms often have similar stages
in development
DNA Homology

Comparison of genes and proteins shows
the relationships between species
Biogeography

Closely related species tend to be found in the
same region
 The
geographical distribution of species only makes sense
in light of evolutionary past

What are specific examples?
 Marsupial
Mammals in Australia
 Finches in Galapagos
 Fruit flies in Hawaii
Different geographic regions,
different mammalian “brands”