Evolution
Chapter 15
“A change over time”
The Theory of Evolution


Evolution literally means to change over
time.
A theory is a well supported, testable
explanation that observes observations
from the natural world
Questions that evolution attempts
to answer.


How do species adapt to changes in the
environment?
How do new species develop?
Charles Darwin
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
1809-1882
Studied to be a doctor
and a minister
1831 sailed around the
world as a naturalist on
the HMS Beagle
HMS Beagle
Darwin’s Voyage
Galapagos Islands
Galapagos Islands
15-2 Darwin’s Influences
James Hutton


Geologist
Proposed that the earth was
millions of years old based
on geologic evidence
Sir Charles Lyell

Geologist
 Proposed that geologic
changes occur slowly over long
periods of time.
 Darwin read his book,
Principles of Geology, on the
Beagle
Jean Baptiste Lamarck
French Naturalist
Published his ideas on
evolution in 1809 in
Philosophie zoologique
Lamarck’s Hypothesis
Organisms Strive for Perfection – all
individuals are trying to better themselves
Lamarck’s Hypothesis
Use and Disuse –
If an individual uses a trait it will be more
useful
If an individual does not use a trait it will
decrease in usefulness
Lamarck’s Hypothesis
Inheritance of Acquired characteristics
Analyzing Lamarck’s Hypothesis

There is no evidence to suggest that plants
and animals are trying to improve
themselves
Analyzing Lamarck’s Hypothesis

Use and disuse do not change all
characteristics


Stretching will not make you taller
Reading will not make your eyesight better
Analyzing Lamarck’s Hypothesis

Acquired characteristics are not inherited

A mouse that loses its tail will still produce
offspring with tails
Erasmus Darwin
Charles Darwin’s
Grandfather
Physician and Scientist
'All vegetables and
animals now living
were originally derived
from the smallest
microscopic ones.'
Thomas Malthus –

Economist

Human Population would be
limited
Starvation
 War (Competition)
 Disease

15-3 Darwin Presents His Case
Alfred Wallace

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Developed his own theory
of Natural Selection
Contacted Darwin
This caused Darwin to
finally publish his theory
with Wallace
On Origins of Species

After publishing with
Wallace, Darwin submitted
all of his ideas in a book
titled On Origin of Species,
By Means of Natural
Selection in 1858
Artificial Selection

Darwin was influenced to believe change
was possible because of the humans
selecting for traits in plants and animals.
Darwin’s Theory

Evolution “Change” is driven by natural
selection
Evidence for Evolution

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Fossil Record
Anatomy
Development
Molecular Evidence
Fossil Record


Since most of the “ancestor” species are
extinct, fossils are the only evidence that
can be examined.
Intermediate “missing link” fossils are very
informative
Archaeopterix
A fossil of a bird like creature
Has feathers, teeth and claws in its wings
Whale Ancestors
Anatomy
Structures similarities in body structure
indicates organisms are related
Homologous Structures
Structures that have common function and
design (ancestry)
Vestigial Organs
Structures that have reduced size and or
function
Developmental Evidence

Similarities in embryonic development are
interpreted to mean closer relationships.
Developmental Evidence

Similarities in embryonic development are
interpreted to mean closer relationships.
Molecular Evidence
Organisms are considered to be more closely
related if
DNA sequences in genes are more similar
Amino acid sequences in proteins is more
similar
Molecular Evidence
Organisms are considered to be more closely
related if
DNA sequences in genes are more similar
Amino acid sequences in proteins is more
similar
Summary of Darwin’s Theory
Variation

There are differences within a population

Mutation and Sexual Reproduction
Competition for resources

Not all offspring will survive
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Starvation
Overcrowding
Predation
Fitness

Some of the variants will have an
advantage over the others, they will survive
and produce more offspring
Reproduction and Inheritance

These advantages will be passed on to the
next generations
Descent with Modification

Species alive today are descended with
modification from ancestral species
Tree of Life

All species are connected on a single tree
of life
Modern Theory

Mendel’s discoveries in genetics explained
a great deal in evolution
Strengths of Darwin’s Theory
Many discoveries in Physics, Geology and
Biology have supported and expanded
Darwin’s ideas
Strengths of Darwin’s Theory
Many discoveries in Physics, Geology and
Biology have supported and expanded
Darwin’s ideas
Weaknesses of Darwin’s Theory
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Researchers still debate how new species
arise and how they become extinct.
The origin of life is still very uncertain