Upload
diane-little
View
225
Download
0
Tags:
Embed Size (px)
Citation preview
Thinking About Darwinian Thinking About Darwinian Evolution:Evolution:
What is evolution?? And what is this finch doing?!?
We owe much of our understanding of EVOLUTION to
CHARLES CHARLES DARWINDARWIN..
Darwin’s Origin of Species (1859):
1. Descent with Modification (Evolution)
2. Natural Selection as a mode of Evolution
Remember: Mendel publishes in 1866…
Darwin’s Natural Selection:Darwin’s Natural Selection:
Observation #1: Individual Variation
Observation #2: Struggle for Existence
Inference: Differential Reproductive Success or Natural Selection
ADAPTATIONSADAPTATIONS are the result of natural selection.
Darwin also proposed that natural selection, over time, could
produce new species from ancestral species.
This was his explanation for the 14
unique species of finches he
observed on the
Galapagos Islands.
Darwin’s Historical Context: The Philosophy of the Time
•Plato (427-347 BC): two worlds: a real (ideal) world, and an illusory world (imperfect) that we perceive with our senses.
•Aristotle (384-322 BC): all living forms can be arranged on a scale or ladder or increasing complexity. (All rungs taken!)
•Judeo-Christian Context: Biology in Europe and America dominated by natural theology- classifying species in order to reveal the steps of the scale of life God created.
The Historical ContextThe Historical Context"Those who which to succeed must ask the right preliminary questions." - Aristotle
FOSSILS: Paleontology (the study of fossils) is developed by Cuvier (1769-1832). He documents the succession of fossil species in the Paris Basin. He advocates catastrophism rather than evolution.
Darwin’s Historical Context: The Philosophy of the Time
GEOLOGICAL THEORIES: Hutton (1726-1797) proposes gradualism (profound change is the result of
slow continuous processes). Lyell (1797-
1875) expands to uniformitarianism
(geologic processes have not changed throughout the Earth’s long history).
Darwin’s Historical Context: The Philosophy of the Time
Other Scientists had suggested EVOLUTION, but none had proposed a MECHANISM!
First Mechanism: Jean Baptiste Lamarck
Lamarck observes several lines of descent in fossils. Suggests that use and disuse results in change in morphology. He
suggests that these acquired characteristics (adaptations!)
could be inherited.
This is wrong, but visionary!
Malthus contends Malthus contends that much of that much of
human suffering is human suffering is the unavoidable the unavoidable
consequence of the consequence of the potential for the potential for the
human population human population to increase faster to increase faster than food supplies than food supplies
and other and other resources.resources.
Darwin is heavily influenced by Darwin is heavily influenced by Thomas Thomas MalthusMalthus’ writings on ’ writings on
human population (1798)human population (1798)
Darwin’s MECHANISM = NATURAL SELECTION
•Natural selection is differential success in reproduction
•Natural selection occurs through an interaction between the environment and the variability inherent among the individual organisms making up a population
•The product of natural selection is the adaptation of populations of organisms to their environment.
Darwin’s ideas remain
unpublished until another scientist, Alfred Wallace, independently develops the
same theory of Natural
Selection.
Darwin publishes second, but in
much more detail.
Darwin illustrates his mechanism with examples from ARTIFICIAL
SELECTION, the breeding of domesticated plants and animals
If artificial selection can change so much in a relatively short time, argues Darwin, then
natural selection should be capable of considerable modifications.
Examples of Natural Selection:
•Insecticide-Resistant Insects
•Antibiotic-Resistant Bacteria
•Drug-Resistance in HIV
Other Evidence of Evolution: HomologyHomology
Similarity in characteristics resulting from common ancestry is known as
HOMOLOGY.
Homology can be:
1. Anatomical (Homologous Structures)
2. Molecular (esp. DNA)
3. Embryological- developmental structures and processes.
Anatomical Homology:Anatomical Homology:
FISH
REPTILEFISH CHICKEN HUMAN
Developmental Developmental Homology:Homology:
MOLECULAMOLECULAR R HOMOLOGYHOMOLOGY::
Some HOMOLOGIES are MISLEADING…Some HOMOLOGIES are MISLEADING…
as they result from as they result from CONVERGENT CONVERGENT EVOLUTIONEVOLUTION..
BIOGEOGRAPHYBIOGEOGRAPHY, or the geographic distribution of species, provides many
clues about their evolution.
Islands are especially good for studying biogeography as they contain many isolated, endemic
species.
The The FOSSIL RECORDFOSSIL RECORD provides the last major provides the last major line of evidence in support of Darwin’s ideas.line of evidence in support of Darwin’s ideas.
The Darwinian view of life predicts the existence of evolutionary transitions.
Bailosaurus
Thus Darwin’s views are supported by multiple, independent lines of
evidence.
Evolutionary patterns of HomologyHomology that match patterns in space
(BiogeographyBiogeography) and time (the Fossil Fossil RecordRecord).