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Descent With Modification:A Darwinian View of Life

Chapter 22

Objectives for Chapter: 22

1. Understand the following contributions made by the following as they relate to Darwin’s Theory of evolution.

Aristotle, Plato

Linnaeus

Cuvier

Hutton, Lyell

Lamarck, and Malthus

Alfred Wallace

2. Know the main observations and related inferences that Darwin suggested to explain natural selection as a mechanism for evolutionary change.

3. Know the main steps that make up Darwin’s theory of evolution.

4. Know the main aspects of Darwin’s voyage that influenced his theory: including South American flora and fauna, Galapagos Islands, Finches, tortoises

What is Evolution?

A change in the gene pool of a population in

response to various stimuli exhibited by a

species over time.

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Geologist Theories

Hutton – 1795

Gradualism

Cuvier – 1815

Catastrophism

Lyell – 1830

Uniformitarianism

Catastrophism

Naturalist’s Theories

Carolus Linneaus

1707-1778

Thomas Malthus – 1798

Principles of populations

Alfred Wallace – 1858

Theory of Natural Selection

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Jean Baptist Larmark

Theory of Inheritance of Acquired

Characteristics - 1801

Change is made by what

the organisms wants or need

and then is passed down

to offspring.

WRONG !!!

Why?????

Charles Darwin

1809-1882

English Naturalist

At age 22 set sail on H.M.S. Beagle

for South America – Galapagos

Islands.

Wrote The Origin of Species

Three major findings: Fossils,

Geographical Patterns and

Similarities among the Oceanic

Islands.

The Voyage that Changed Everything

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What leads to the change of

organisms?

Artificial Selection

Man selects the desired traits

Dogs

Horses

Pigeons

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What leads to the change of

organisms?

1. Over reproduction

Many organisms produce

more than the environment

can accommodate.

Carrying Capacity – the #

of individuals a given area

will hold.

What leads to the change of

organisms?

2. Variation among species.

Some due to genetic changes called mutations.

Most due to genetic diversity!

What leads to the change of

organisms?

3. Limited resources

Food

Shelter

Territory

Mates

Water

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What leads to the change of

organisms?

4. Competition

Fast

Strong

Smart

Hide

Bluff

Make noise

What leads to the change of

organisms?

5. Reproductive

Success

Able to make

offspring and pass

their genes on to the

next generation.

The Origin of the Species convinced most

biologists that species are the products of

evolution.

What was missing in Darwin’s explanation was an

understanding of inheritance that could explain

how chance variations arise in a population while

also accounting for the precise transmission of

these variations from parents to offspring.

Although Gregor Mendel and Charles Darwin were

contemporaries, Mendel’s discoveries were

unappreciated at the time, even though his principles of

heredity would have given credibility to natural

selection

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•The finches of the Galapagos Islands diversified after an initial colonization from the mainland to exploit different food sources on different islands.

Theory of Natural Selection

Those individuals that possess superior physical, behavioral, or other attributes are more likely to survive than those that are not so well endowed.

“Survival of the Fittest”

Those best able to reproduce!

Biodiversity

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Pocket Mice

Biological diversity is something to relish and

preserve, but it can also be a bit overwhelming.

Evidence of Evolution

Fossil Record

Earliest 3.5

Billion yrs. Old

Cell type?

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Age of the Earth

Alternatively, we

can view these

episodes with a

clock analogy.

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Comparative Anatomy

Homologous Structures

Same origin, close to same structure with a different function.

Examples

Comparative Anatomy

Analogous

Structures

Same function

different structure.

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Comparative Anatomy

Vestigial Organs

Structures that serve no purpose

Often homologous with other organs useful in other species

Examples- eye on cave fish

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Molecular Biology

*Sequencing of lettering

of DNA

*Biochemical

Cytochrome C

Blood Proteins

Amino Acids

Development

Embryological

Development

Gene Expression

Most embryos develop

almost identically

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