Download presentation
Presentation is loading. Please wait.
Published byEustacia Flynn Modified over 6 years ago
1
Charles Darwin: Theory of Evolution as a Mechanistic Process
JRMGUCE 2009
2
Charles Darwin: Theory of Evolution as a Mechanistic Process
Darwin’s Idea of Common Descent Darwin’s Idea of Multiplication of Species Darwin’s Idea of Gradualism Darwin’s Idea of Natural Selection
3
Darwin’s Idea of Common Descent
Descent with modification A.K.A EVOLUTION common ancestor/prototype Accumulated diverse modifications or adaptations
4
The finches posed questions to Darwin:
Did they descend from one mainland ancestor, did islands allow isolated populations to evolve independently, and could present-day species have resulted from changes occurring in each isolated population???
5
Darwin’s Idea of Common Descent
Life history is like a tree Common trunk: multiple branching and re-branching Common ancestor in each fork of branching lineage of common descent Extinct species
6
TAXONOMY: Tree of Life Carolus Linnaeus - Species are fixed
Kingdom Phylum Class Order Family Genus Genus species Carolus Linnaeus - Species are fixed - Ordered the great diversity of organisms into “groups subordinate to groups”
7
Reflected the genealogy of the tree of life
8
Darwin’s Idea of Multiplication of Species
species either split into or bud off other species geographical isolation of a founder species. Founder effect. The frequency of the a allele is low in the initial population, but a small subset, in which one individual is Aa, is removed from the large population and founds a new population. The frequency of a is markedly higher in this new population, due to its relatively high frequency in the founders
10
Darwin’s Idea of Multiplication of Species
different ecological niches provide different ways of living different plants and animals come to fill different niches with different shapes and behaviors
12
Darwin’s Idea of Gradualism
changes through the gradual change of population rather than the sudden production of new individuals species arise: Through gradual accumulation of adaptations to a different environment
14
e.g. Darwin’s finches ADAPTIVE RADIATION
15
Rapid evolution may arise:
Isolation of small population Migration of small group in a new environment Through mass extinction Because of geological barriers
16
Darwin’s Idea of Natural Selection
Compared processes in nature with artificial selection Developed a scientific hypothesis to explain how evolution occurs Struggle for existence (Malthus) Members of each species compete regularly to obtain food and living space and other necessities in life Central to his Theory of Evolution
17
Survival of the Fittest
* key factor in the struggle for existence * Fitness -ability to survive and reproduce -result of adaptation -central to the process of evolution by natural selection
18
referred to as: NATURAL SELECTION
LOW FITNESS Either DIE or LEAVE FEW OFFSPRINGS HIGH FITNESS LEVEL many OFFSPRINGS referred to as: NATURAL SELECTION accumulation of changes that differentiate groups from one another, such that a new species may arise
19
DARWIN’s MISSING INGREDIENT
Darwin did not understand the genetic basis for variation variations mutations genetic recombination mutation as a raw material for evolution
20
OTHER THINGS TO BE CONSIDERED
Natural vs. Artificial selection Importance of population in evolution smallest unit that can evolve Natural selection acts on individuals but INDIVIDUALS DO NOT EVOLVE
21
DESCENT WITH MODIFICATION FROM ANCESTRAL SPECIES
Darwinian View of LIFE Diverse forms have arisen DESCENT WITH MODIFICATION FROM ANCESTRAL SPECIES Biological diversity Mechanism of modification NATURAL SELECTION
22
Patterns of Evolution Mass extinction
99% of the species ever lived are now extinct wiped out whole ecological systems* Cretaceous extinction Large asteroid struck the earth Can be caused by eruptions of many large volcanoes (Permian and Cretaceous) , changing of positions of continents and changing of sea levels * Disrupting energy flows and causing food web to collapse
23
Patterns of Evolution Adaptive Radiation
single species or small group of species has evolved into several different forms that live in different ways Ex. Darwin’s Finches Dinosaurs Mammals
25
Patterns of Evolution Convergent Evolution
unrelated organisms come to resemble one another Natural selection may mold different body structures structures tend to function the same way and look similar Analogous structures same look and function Different embryonic origin
27
Patterns of Evolution Coevolution
two species evolve in response to the changes in each other over time Ex. Fig trees and wasps
28
Patterns of Evolution Developmental Genes and Body Plans Hox genes
29
Process of Speciation Species
group of organisms that can interbreed and produce a fertile offspring Share a common gene pool As new species evolve populations become reproductively isolated from each other Reproductive isolation Can be: Behavioral, Geographical and Temporal
30
Process of Speciation Behavioral isolation Geographical isolation
Capable of interbreeeding but has different courtship rituals or behavior Geographical isolation Two populations are separated by geographic barriers Acted by natural selection Ex. Abert and Kaibab Squirrels
31
Process of Speciation
32
Process of Speciation
33
DIANE DODD’s Experiment
Similar presentations
© 2024 SlidePlayer.com. Inc.
All rights reserved.