1 Evolution Diversity of Life. Charles Darwin (1800’s) was an English naturalist who developed the theory of evolution by natural selection. This theory.

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EvolutionDiversity of Life

• Charles Darwin (1800’s) was an English naturalist who developed the theory of evolution by natural selection. This theory states that species change over time in response to changes in their environment.

• Darwin collected most of his data during the voyage of the H.M.S Beagle when they stopped at the Galapagos Islands (off the coast of South America).

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A reconstruction of the HMS Beagle sailing off Patagonia.

Darwin’s Voyage of Discovery

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Darwin Left England in 1831

Darwin returned 5 years later in 1836

• In the Galapagos Islands Darwin observed similar species that had traits that were suited to their particular environment. This is known as an adaptation.

• One adaptation that he observed was the differences among finches. The Galapagos finches resembled the finches on the mainland, but differed in nesting site, beak shape and eating habits. Each finch seemed to acquire a beak shape that catered to its specific eating habits.

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• He noticed the same phenomenon with the various tortoises in the Galapagos. The length of their necks seemed to correlate with the different vegetation of the area.

• This caused him to wonder if they all originated from the same ancestral species.

• Darwin referred to the ability of an organism to survive and reproduce in its environment as fitness.

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• When organisms with specific traits are bred to produce offspring with the same traits it is called artificial selection. Darwin believed there was a force in nature that worked similar to artificial selection. He called this natural selection.

• Twenty years after his findings, Darwin published his ideas in a book called On the Origin of Species. He waited so long because his ideas challenged fundamental scientific beliefs and he was afraid. He decided to publish when Alfred Wallace sent him an essay that was similar to Darwin’s own ideas.

• Wallace and Darwin both read an essay by Thomas Malthus that proposed that human populations outgrow resources so there is a constant struggle for existence

• The tenets of Natural Selection as presented by Darwin:

– Individual organisms in nature differ from one another. Some variation is inherited.

– Organisms in nature produce more offspring than can survive and many that survive do not reproduce.

– Members of each species must compete for limited resources.

• Each organism is unique and has different advantages and disadvantages in the struggle for existence.

• Individuals best suited for their environment survive and reproduce most successfully. Survival of the fittest.

– Species change over time in characteristics such as size and form causing new species to arise and others to disappear.

– Species alive today have descended with adaptations from species that lived in the past. This is called descent with modification. The idea that all things have a common ancestor is known as common descent.

• Evidence that supports the theory of evolution by natural selection:

– Fossils- show a change in species structure over time

– Anatomical studies- indicates evolutionary relationships (analogous, homologous, vestigial structures)

– Homologous structures- indicate that organisms share a common ancestry

• Structures that are similar in arrangement and function but modified for specific organisms (whale flipper, arm, bird wing)

– Analogous structures- indicates independent adaptation to similar ways of life

• Structures with no common ancestry, but similar in function (wings of bat, bird, and butterfly)

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Homologous Structures

– Vestigial structures- indicate changes in an organism’s behavior or environment

• Structures that are present in organisms, but are functionless (appendix, wisdom teeth, coccyx)

– Embryonic similarities- shows developmental similarities among organisms

– Genetic comparisons- indicates evolution from a common ancestor

• All of the different alleles for a trait that are present in a population are called the gene pool. Movement of genes into and out of a population is called genetic drift.

– Time - James Hutton’s and Charles Lyell’s work indicated that the earth is approximately 4.5 billion years old. This allowed plenty of time for evolution to occur.

• Direct evidence that supports the theory at present is:

– Drug resistance of bacteria– Pesticide resistance by flies and weeds– Change in the allele frequencies of peppered

moth population– Camouflage allowing species to blend into

their environment– Mimicry which enables one species to

resemble another

Evolution of drug-resistance in HIV

mimicry.

Yellow jacket waspSyrphid fly

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Evidence for Evolution – Evolution Observed

Selection against small guppies results in an increase in average size

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Microevolution: Short time scale

events (generation-to-generation) that

change the genotypes and phenotypes of

populations

Evolutionary Time Scales

• Natural selection acts on variations. Some variations among species increase or decrease an organism’s survival rate. There are three types of selection that act this way: stabilizing selection, directional selection and disruptive selection.

• In convergent evolution, different species become more and more similar because they are adapting to the same type of environment. Ex. shark and dolphin.

• In divergent evolution, members of the same species become more and more different because they are adapting to different environments. Ex. Galapagos tortoises. This is also called adaptive radiation or speciation.

• Some organisms that are closely connected to one another through ecological interactions evolve together.. The process by which two species evolve in response to one another is called coevolution.

• Lamarck's theory, the Inheritance of Acquired Traits-stated that organisms would gain or lose features if you overused or didn't use them, and you could pass these new traits onto your offspring. This was proven to be wrong!

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Lamarck’s Theory of Evolution

• Inheritance Of Acquired Traits– Traits Acquired During Ones Lifetime Would Be

Passed To Offspring

Clipped ears of dogs could be passed to offspring!

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“Nothing in biology makes

sense EXCEPT in the light of evolution.” Theodosius Dobzhansky

Evolution

Charles Darwin in later years

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Evolution By Natural Selection Concepts

• The Struggle for Existence (compete for food, mates, space, water, etc.)

• Survival of the Fittest (strongest able to survive and reproduce)

• Descent with Modification (new species arise from common ancestor replacing less fit species)

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Survival of the Fittest

• Fitness– Ability of an Individual To Survive &

Reproduce• Adaptation

– Inherited Characteristic That Increases an Organisms Chance for Survival

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Survival of the Fittest

• Adaptations Can Be:–Physical

• Speed, Camouflage, Claws, Quills, etc.–Behavioral

• Solitary, Herds, Packs, Activity, etc.

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Survival of the Fittest

• Fitness Is Central To The Process Of Evolution

• Individuals With Low Fitness– Die– Produce Few Offspring

Survival of the FittestAKA Natural Selection

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Survival of the Fittest

Key ConceptOver Time, Natural Selection Results In

Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment

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Evolution By Natural Selection Concepts

• The Struggle for Existence (compete for food, mates, space, water, etc.)

• Survival of the Fittest (strongest able to survive and reproduce)

• Descent with Modification (new species arise from common ancestor replacing less fit species)

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Survival of the Fittest

• Fitness– Ability of an Individual To Survive &

Reproduce• Adaptation

– Inherited Characteristic That Increases an Organisms Chance for Survival

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Survival of the Fittest

• Adaptations Can Be:–Physical

• Speed, Camouflage, Claws, Quills, etc.–Behavioral

• Solitary, Herds, Packs, Activity, etc.

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Survival of the Fittest

• Fitness Is Central To The Process Of Evolution

• Individuals With Low Fitness– Die– Produce Few Offspring

Survival of the FittestAKA Natural Selection

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Survival of the Fittest

Key ConceptOver Time, Natural Selection Results In

Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment