descent with modification chapter 22. rise of modern biology a. pre-darwin ideas geology larmark b....
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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 processesSame 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 (1744-1829) 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. Fossils & fossil records show that organisms simpler complex
2. Overproduction of offspring3. Limited supply of resources in
an environment4. 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
selectedPopulations 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. Fossil Records2. Comparative Anatomy3. Embryonic Structures4. DNA Homology5. Biogeography
Fossils Remains, traces or imprints of
an organism preserved in the earth’s crustImprintMoldCastPetrified
Fossil Records1. Fossils & the order in which they
appear in layers of rocks2. 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 structuresEx: 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”