Theoryofevolution 110815170612-phpapp01

Theory of Evolution
By Nonhlanhla Nkosi

Definiti
on
• Evolution is
the slow ,
gradual
change in a
population of
organisms over
time
2

Isn’t evolution “just a theory”?
In every day usage “theory” often refers to a
hunch or a speculation. When people say, “I
have a theory about what happened,” they are
often drawing a conclusion based on fragmentary
or inconclusive evidence.
The formal scientific definition of “theory” is
quite different from the every day meaning.
It refers to a comprehensive explanation of
some aspect of nature that is supported by a
vast body of evidence.
http://evolution.berkeley.edu/evosite/evohome.htm

Evolution
Pre-Darwin Beliefs
• Earth was only a few thousand years old.
• We now know it is billions of years old.
• Neither the planet nor the species that
inhabited it had changed since the beginning of
time.
• We now know the planet has changed and,
through fossils, discovered organisms have
changed, as well.

THE THEORY OF EVOLUTION
• CHARLES DARWIN
• EVIDENCE FOR EVOLUTION
• MECHANISMS FOR EVOLUTION
• NATURAL SELECTION
• SPECIATION

http://evolution.berkeley.edu/evolibrary/home.php
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

Charles Darwin
the Naturalist

6

• CHARLES DARWIN
• SPECIATION



Voyage of the
Beagle
Charles Darwin
• Born Feb. 12, 1809
• Joined Crew of HMS
Beagle, 1831
• Naturalist
• 5 Year Voyage around world
• Avid Collector of Flora &
Fauna
• Astounded By Variety of
Life
8

Darwin Left England in
1831

Darwin returned 5 years later in 1836
9

EVIDENCE OF EVOLUTION
• STRUCTURAL ADAPTATIONS
• MIMICRY – the insect looks like the leaf
• CAMOUFLAGE – the chameleon can change color to
match its surroundings


http://science.howstuffworks.com/animal-camouflage2.htm


EVIDENCE OF EVOLUTION
• STRUCTURAL ADAPTATIONS
• MIMICRY
• CAMOUFLAGE
• MILLIONS OF YEARS
• PHYSIOLOGICAL ADAPTATIONS
• CHANGE IN A METABOLIC PROCESS
• WHAT DO YOU HEAR ABOUT IN THE NEWS
ABOUT SOME BACTERIA?


The Galapagos
Islands
• Small Group of Islands 1000 km West of South
America

• Very Different Climates
• Animals On Islands Unique
• Tortoises
• Iguanas
• Finches
12

The Galapagos
Islands
• Volcanic islands off the
coast of South America
• Island species varied
from mainland species
& from island-to-island
species
• Each island had long or
short neck tortoises
13

The Galapagos
Islands
• Finches on the islands resembled a mainland finch
• More types of finches appeared on the islands where
the available food was different (seeds, nuts, berries,
insects…)
• Finches had different types of beaks adapted to their
type of food gathering

15

Darwin’s
Observations
• Patterns of Diversity
Patterns of Diversity
were shown

• Unique Adaptations
in organisms
• Species Not Evenly
Distributed
• Australia, Kangaroos,
but No Rabbits
• S. America, Llamas

17

Darwin’s
Observations
• Both Living
Organisms &
Fossils collected
• Fossils included:
•Trilobites
•Giant Ground
Sloth of South
America
This species NO longer existed.

What had happened to them?
18

Evidence for Evolution – The Fossil Record

19

Darwin’s
Observations
• Left unchecked, the number of
organisms of each species will increase
exponentially, generation to generation
• In nature, populations tend to remain
stable in size
• Environmental resources are limited

20

Darwin’s
Observations

• Individuals of a population
vary extensively in their
characteristics with no two
individuals being exactly
alike.
• Much of this variation
between individuals is
inheritable.

21

Darwin’s
Conclusion

• Production of more individuals
than can be supported by the
environment leads to a struggle for
existence among individuals
• Only a fraction of offspring
survive each generation
• Survival of the Fittest

22

Darwin’s
Conclusion
• Individuals who inherit
characteristics most fit
for their environment
are likely to leave more
offspring than less fit
individuals
• Called Natural
Selection

23

OTHER EVIDENCE OF EVOLUTION
• FOSSILS
• ANATOMY
• HOMOLOGOUS STRUCTURES – structures that are
similar because they are inherited from a common ancestor



• FOSSILS
• ANATOMY
• HOMOLOGOUS STRUCTURES
• ANALOGOUS STRUCTURES – structures that are similar because
they serve the same function but do not have a common ancestor.



• FOSSILS
• ANATOMY
• ANALOGOUS STRUCTURES
• VESTIGIAL STRUCTURE – a feature inherited from an ancestor
that is now less elaborate and functional, usually formed when a
population experiences a different environment

WHAT IS
ANOTHER
EXAMPLE OF
VESTIGIAL
STRUCTURES?

These fish live
in the dark and
therefore do not
need functional
eyes.

• FOSSILS
• ANATOMY
• ANALOGOUS STRUCTURES
• VESTIGIAL STRUCTURE
• EMBRYOS



Similarities In Early
Development
• Embryonic Structures Of Different Species Show
Significant Similarities
• Embryo – early stages of vertebrate development

28

MECHANISMS FOR EVOLUTION
• DO POPULATIONS OR INDIVIDUALS EVOLVE?
• WHAT IS A GENE POOL?
• HOW CAN THE GENE POOL CHANGE?
• MUTATION
• GENETIC DRIFT
• GENE FLOW
• WOULD THESE THINGS EFFECT A LARGE
POPULATION OR A SMALL POPULATION MORE?


Any change in an organism’s
DNA

When some organisms
RANDOMLY survive longer than
others and pass on their genes.

The movement of genes from
one population to another
through migration of
individuals.
ALL IMAGES: http://evolution.berkeley.edu/evolibrary/home.php


• CHARLES DARWIN
• SPECIATION



WHAT IS NATURAL SELECTION?
Variation in some traits (color of beetles)
Green beetles tend to get eaten and do not survive
long enough to reproduce

The surviving brown beetles have brown offspring.
Eventually all the green beetles get eaten, leaving only
brown beetles.


Darwin’s Theory
of Evolution
Organisms Change Over Time

35

Common Descent with
Modification
• Darwin proposed that
organisms descended
from common
ancestors
• Idea that organisms
change with time,
diverging from a
common form
• Caused evolution of
new species
36

Natural Selection
• 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)

37

Natural selection
• Fitness
• Ability of an Individual To Survive
& Reproduce

• Adaptation
• Inherited Characteristic That
Increases an Organisms Chance for
Survival
38

Natural selection
• Adaptations Can Be:
• Physical
• Speed, Camouflage, Claws, Quills,
etc.

• Behavioral
• Solitary, Herds, Packs, Activity, etc.

39

Survival of the
Fittest
• Fitness Is Central To The Process Of
Evolution
• Individuals With Low Fitness
• Die
• Produce Few Offspring

Survival of the Fittest
AKA Natural Selection
40

Natural selection
Key Concept
Over Time, Natural Selection
Results In Changes In The
Inherited Characteristics Of A
Population. These Changes
Increase A Species Fitness In Its
Environment
41

IMPORTANT TO REMEMBER !
•POPULATIONS evolve
NOT INDIVIDUALS.

•NATURAL SELECTION only
works on heritable traits.
•A trait that is favorable in one
environment may be useless or
detrimental in another.

WHAT IS SPECIATION?
• GEOGRAPHIC ISOLATION
A barrier, either
physical, like a river
changing course, or
nonphysical, causes
the population to
become separated.



WHAT IS SPECIATION?
• GEOGRAPHIC
ISOLATION
• REPRODUCTIVE
ISOLATION
• for example, what might
occur between fruit flies
raised on different types of
food?
• when allowed to interact,
some would only mate with
the same food preference as
itself


BOTH LIVE IN FOREST ECOSYSTEMS
Adapted to similar
environments, but
evolved independently
from different ancestors.
SUGAR GLIDER
in Australia is a marsupial
more closely related to
Kangaroos than North
American
FLYING SQUIRRELS
because
its ancestors were
marsupials.

WHAT IS SPECIATION?
• REPRODUCTIVE ISOLATION
• PACE OF EVOLUTION:

Gradualism – slow
steady change over a
long time

Punctuated equilibrium – a large
amount of change in a short time
due to a specific event.


WHAT IS SPECIATION?
• REPRODUCTIVE ISOLATION
• GRADUALISM
• PUNCTUATED EQUILIBRIUM
• DIVERGENT EVOLUTION – two species that are now
dissimilar but can be traced back to the same ancestor
• ADAPTIVE RADIATION – adaptations to survive in new
environmental conditions

• CONVERGENT EVOLUTION – species having similar
features in spite of not having the same ancestor

ADAPTIVE RADIATION – AN EXAMPLE
OF DIVERGENT EVOLUTION

http://www.vanderbilt.edu/AnS/english/Clayton/Galapago_finches.gif


CONVERGENT EVOLUTION –EXAMPLE



Lamarck’s Theory
of Evolution
• Jean-Baptiste Lamarck, 1809
• One Of First Scientists To
Understand That Change
Occurs Over Time
• Stated that Changes Are
Adaptations To Environment
acquired in an organism’s
lifetime
• Said acquired changes were
passed to offspring
52

Lamarck’s Theory
of Evolution
• Idea called Law of Use
and Disuse
• If a body part were used,
it got stronger
• If body part NOT used, it
deteriorated

53

Lamarck’s Theory
of Evolution
• Inheritance of Acquired
Characteristics
• Proposed That By Selective Use Or Disuse Of
Organs, Organisms Acquired Or Lost Certain Traits
During Their Lifetime
• These Traits Could Then Be Passed On To Their
Offspring
• Over Time This Led To New Species

54

Lamarck’s Theory
of Evolution
• Use & Disuse - Organisms

Could Change The Size
Or Shape Of Organs By
Using Them Or Not Using
Them

• Blacksmiths & Their Sons
(muscular arms)
• Giraffe’s Necks Longer from
stretching)

55

INHERITANCE OF ACQUIRED CHARACTERISTICS
The male fiddler crab uses its
front claw to attract mates and
ward off predators.
“USE or DISUSE” = Use it or lose it

Through repeated use, the front
claw becomes larger.

The fiddler passes on this
acquired characteristic to its
offspring

http://www.geocities.com/arnold_schwarzenegger_pictures/

What’s wrong with Lamarck’s hypothesis?
Lamarck didn’t know about
genes and how traits are inherited.

Acquired traits are not passed on to
offspring

Or are they? . . .
New field of EPIGENETICS is exploring this

Lamarck’s Theory
of Evolution
• Inheritance Of Acquired Traits
• Traits Acquired During Ones Lifetime Would Be Passed
To Offspring

59

59
Clipped ears of dogs could be passed to offspring!

Publication of “On The
Origin of Species”
• Darwin Knew That His Theory Would Be Extremely
Controversial And Would Be Attacked
• His Theory Challenged Established Religious &
Scientific Beliefs, Particularly About The Creation Of
Man

60

• He Refused To Publish Until
He Received An Essay From
Alfred Wallace
• Fellow Naturalist
• Independently Developed The Same
Theory
• After 25 Years, Someone Else Had
Come To The Same Conclusions
From Their Observations Of Nature

61

Wallace’s
Contribution

• Alfred Russel Wallace
Independently came to same
Conclusion as Darwin that
species changed over time
because of their struggle for
existence
• When Darwin read
Wallace’s essay, he knew he
had to publish his findings

62

• Darwin Presented Wallace’s Essay & Some Of His
Work At A Scientific Conference of the Linnaean
Society in July of 1858
• Then He Started On his book “Origin of Species”
• It Took Darwin 18 Months To Complete The Book

63

Natural Variation and
Artificial Selection
• Abandoned The Idea That Species Were Perfect &
Unchanging
• Observed Significant Variation in All Species Observed
• Observed Farmers Use Variation To Improve Crops &
Livestock
• Called Selective Breeding

64

• Natural Variation
• Differences Among Individuals Of A
Species

• Artificial Selection
• Selective Breeding To Enhance Desired
Traits Among Stock or Crops
65

Key Concept:
In Artificial Selection, Nature
Provided The Variation Among
Different Organisms, And
Humans Selected Those
Variations That They Found
Useful
66

Slide by Kim Foglia@ http://www.explorebiology.com/

Can see Natural selection happen
EX: Changes in disease-causing microbes that
produce new organisms and new diseases.
Bird flu
_______
HIV
___

http://www.hhmi.org/askascientist/images/hiv.gif

Antibiotic-resistant tuberculosis
__________________________

Why does evolution matter now?
http://www.hipusa.com/eTools/webmd/A-Z_Encyclopedia/tuberculosis.jpg

Mutation, Evolution, and
Natural Selection

DNA is found in the nucleus of the cell

• Http://www.youtube.com/watch?v=ZK6YP1Smbxk

Mutation
A mutation is a change in gene sequence.

• A mutation is a change in gene sequence.

• There are many different types of mutations and causes for them.
• Some mutations are harmful, while others can be beneficial.

How does mutations
work?

•

DNA is very accurate when making copies of itself, however, sometimes it makes a mistake.

•

Here’s a DNA sequence

•

AGCCCTTATAGGCTC

•

What are the corresponding base pairs?

•

TCGGGAATATCCGAG

•

Now when it’s being copied it replaces the T with a U. Rewrite the your answer with U’s instead of
T’s.

•

UCGGGAAUAUCCGAG

•

What amino acids will this be coded for?

•

Serine, Glycine, Isoleucine, Serine, Glutamic Acid

The Mutation
• Here’s our original DNA sequence
• AGCCCTTATAGGCTC
• ATCCCTTATAGGCTC we replaced the G with a T
• Now what are the corresponding base pairs?
• TAGGGAATATCCGAG
• Now when it’s being copied it replaces the T with a U. Rewrite the your answer with
U’s instead of T’s.
• UAGGGAAUAUCCGAG
• What amino acids will this be coded for?
• Stop, Glycine, Isoleucine, Serine, Glutamic Acid
• You can see how replacing 1 base will change everything!

References
• This is a mash up of 5 different sources which are:
• Allen, A. (2011). Theory of Evolution.
http://www.slideshare.net/MsAllenBio/theory-of-evolution-8858675
• Zolli. (2012). Evolution and Natural selection- How species change over time .
http://www.slideshare.net/mrzolli/evolution-and-natural-selectionpowerpoint
• Tas11244. (2011). Evolution: diversity of life.
http://www.slideshare.net/tas11244/darwin-evolution-revised-with-turningpoint-qs
• Cinhasler. (2011). Descent with modification- a Darwanian view of life.
http://www.slideshare.net/cinhasler/a-pch22
• Highland. N. (2010). Mutation, Evolution and natural selection.
http://www.slideshare.net/ismscience/mutation-evolution-and-naturalselection

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