EvolutionA change in successive generations
of organisms, due to random mutation and changes in the
organisms’ surroundings
Evolution takes place through a set of processes
• including: – mutation– adaptation– natural selection – extinction
Mutation
Genetic mutations & variety produced by sexual reproduction allow for
diversity within a given population.Many factors can cause a change in a
gene over time.
Mutation• Mutations are
important in how populations change over time because they result in genetic changes to the gene pool.
• Mutations are inheritable changes because a mutation is a change in the DNA code
Mutation = change in DNA
Mutations can be: favorable change or adaptation in genetic information that improves a species’ ability to exist in its environment
Mutation = change in DNA
Mutations can be: unfavorable change that does not improve a species’ ability to exist in its environment.
Mutation = change in DNA
Mutations can be: changes in the genetic information that neither harms nor helps the species.
Adaptation
• Adaptations are structures, functions, or behaviors that enable a species to survive.
Adaptation
• Depending on the rate of adaptation, the rate of reproduction, and the environmental factors present, structural adaptations may take millions of years to develop.
Adaptations…Activity: How Handy? The Human Hand
DARWIN’S PHRASE FOR EVOLUTION:“Descent with Modification”
He meant that present-day species arose from a succession of ancestors. Descendents of
ancient ancestors that spread into new environments and accumulated diverse
modifications, or adaptations that allowed them fit into specific ways of life.
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Introduction: Clown, Fool, or Simply Well Adapted?
• What is an adaptation?– Adaptations are behaviors, structures or functions that
enable a species to survive.
Haltere
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CHARLES DARWIN: Father of Evolution
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Jean Baptiste Lamarck: Mechanism of Evolution
– Lamarkians would say:– Use or disuse – Inheritance of acquired
characteristics
– Example…giraffes STRETCH THEIR NECKS BY REACHING and SO THEY HAVE BABIES WITH LONGER NECKS.
– Principles of Geology
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Charles Lyell:
Father
of
Geology
Lynell’s view: Formation of Sedimentary Rock
EARTH is VERY, VERY OLD!
• Darwin realized Earth was very, VERY, VERY, VERY old & that, over time (LOTS OF TIME), present day species have arisen from ancestral species by natural processes
• sedimentary rock is very old – therefore the species that are represented in this rock must also be old.
• Most fossils are found in sedimentary rock.• Older fossils will be found below younger fossils.
NorthAmerica
ATLANTICOCEAN
GreatBritain
Brazil
TheGalápagosIslands
PACIFICOCEANPinta
MarchenaGenovesa
Santiago
Fernandina Pinzón
IsabelaSan
Cristobal
EspañolaFlorenza
DaphneIslands
SantaCruz
SantaFe
40 miles
Equator
40 km0
0
Europe
Africa
SouthAmerica
Ande
s
Argentina
Cape Horn
Cape ofGood Hope
PACIFICOCEAN
Equator
NewZealand
Australia
Tasmania
At the age of 22, Darwin joined a 5 year expedition aboard the HMS Beagle to map the coast of South America…not all who wander are lost!
• Darwin observed that– Organisms vary in many traits– More offspring produced than the environment can support
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Darwin’s Idea of Natural Selection
• Individuals with traits that increase their chance of surviving & reproducing leave more offspring
• As a result, favorable traits accumulate in a population over generations
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13.2 Darwin proposed natural selection as the mechanism of evolution
• Darwin found convincing evidence for his ideas in the results of artificial selection, the selective breeding of domesticated plants and animals
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13.2 Darwin proposed natural selection as the mechanism of evolution
Terminalbud
Lateralbuds
Leaves
Kale
Stem
Brussels sprouts
Cauliflower
Cabbage
Kohlrabi
Wild mustard
Flowerclusters
Flowersand stems
Broccoli
Artificial Selection: Dog Breeding
German shepherd Yorkshire terrier English springerspaniel
Mini-dachshund Golden retriever
Hundreds tothousands of years
of breeding(artificial selection)
Ancestral dog
– In 1859, Darwin published On the Origin of Species by Means of Natural Selection, presenting a strong, logical explanation of descent with modification, evolution by the mechanism of natural selection
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13.1 A sea voyage helped Darwin frame his theory of evolution
• Note these important points – Individuals do not evolve: populations evolve– Natural selection can amplify or diminish only heritable
traits; acquired characteristics cannot be passed on to offspring
– Evolution is not goal directed and does not lead to perfection; favorable traits vary as environments change
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13.2 Darwin proposed natural selection as the mechanism of evolution
• Will natural selection act on variation in hair style in a human population?
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13.2 Darwin proposed natural selection as the mechanism of evolution
• Will natural selection act on tongue rolling in a human population?
(Note: Tongue rolling is an inherited trait, caused by a dominant allele)
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13.2 Darwin proposed natural selection as the mechanism of evolution
• Will natural selection act on eye number in a human population?
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13.2 Darwin proposed natural selection as the mechanism of evolution