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DARWIN’S IDEA OF COMMON DESCENT

Descent with modification A.K.A

EVOLUTION

common ancestor/prototype

Accumulated diverse modifications or adaptations

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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

TAXONOMY: TREE OF LIFE

Carolus Linnaeus Species are fixed Ordered the great diversity of organisms into “groups

subordinate to groups” Kingdom

Phylum Class Order

Family Genus

Species

Reflected the genealogy of the tree of life

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

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.

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

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Rapid evolution may arise: Isolation of small population Migration of small group in a new environment Through mass extinction Because of geological barriers

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

Survival of the Fittest

key factor in the struggle for existence

Fitnessability to survive and reproduceresult of adaptationcentral to the process of evolution by natural selection

LOW FITNESS Either DIE or LEAVE FEW OFFSPRINGS

HIGH FITNESS LEVEL many OFFSPRINGS

referred to as: NATURAL SELECTIONaccumulation of changes that differentiate groups from one another, such that a new species may arise

DARWIN’S MISSING INGREDIENT

Darwin did not understand the genetic basis for variation

variations mutations genetic recombination

mutation as a raw material for evolution

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

DARWINIAN VIEW OF LIFE

Diverse forms have arisenDESCENT WITH MODIFICATION FROM

ANCESTRAL SPECIES Biological diversity

Mechanism of modification NATURAL SELECTION

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

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

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

PATTERNS OF EVOLUTION Coevolution

two species evolve in response to the changes in each other over time

Ex. Fig trees and wasps

PATTERNS OF EVOLUTION

Developmental Genes and Body Plans

Hox genes

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

PROCESS OF SPECIATION Behavioral isolation

Capable of interbreeeding but has different courtship rituals or behavior

Ex. Eastern and western meadowlark

Geographical isolation Two populations are separated by geographic barriers Acted by natural selection Ex. Abert and Kaibab Squirrels

PROCESS OF SPECIATIONBehavioral Geographical

Temporal isolation Two or more species reproduce at the different times

PROCESS OF SPECIATION

DIANE DODD’S EXPERIMENT