Transcript Evolution

Intro
“There is no ‘Great Plan’ out there to
conform with the evolutionary theory,
just organisms struggling to pass their
genes on to the next generation.
That’s it”
Evolution
• Changes in groups of organisms over time
History of Evolution
Important Players
James Hutton
• Published studies in 1785
• Geologist
• Theory of Uniformity- the
earth was created by the
same forces that are in
existence today (plate
tectonics)
• Before Hutton, world was
thought to be 6000 years old
• His research supported that
the Earth is 4.6 billions years
old
Thomas Malthus
• Worked with human
population studies
• Observed that plants and
animals reproduce at a
greater rate than their
ability for survival,
creating competition
within a species
• Important to Wallace and
Darwin’s theory
Jean-Baptiste Lamarck
1809- 1st to develop a
scientific theory of evolution
known as the

Theory of Inheritance of
Acquired Characteristics:
Organisms developed new
organs or modified old ones to
meet environmental challenges

Selective use or disuse would
alter the size or shape of
organs or structures passed to
offspring

Examples Larmarck Observed
• Long Neck giraffes - short neck giraffes that
strained to reach higher branches would
grow longer necks
Lamarck’s Theory
Proven to be False
• Change DNA by usage of the structures (BOGUS!
Mendel was not yet born so little was known
about genetics). Think of body building and
passing that on to your offspring
• No extinction of species, just changed into other
organisms
• Lower order organisms were spontaneously
created to fill the void (nothing was due to
chance).
Alfred Wallace
• 1850’s
• Naturalist
• Developed a theory
similar to Darwin’s
• His essay to Darwin
motivated Darwin to
publish the book, On
the Origin of Species.
Letter from Wallace to Darwin in
1864
“I shall always maintain (the theory
of evolution by natural selection)
to be actually yours and yours
only. You had worked it out in
details I had never thought of
years before I had a ray of light on
the subject”
Charles Darwin
• 1830’s
• Known as the “Father
of Evolution”
• Naturalist on the HMS
Beagle (shipping
vessel) collecting
specimens and created
detailed written
observations
• Inspired by the
biological diversity of
the Galapagos Islands
Voyage of the Beagle
• 5 year voyage began in 1831
• Only 5 weeks spent on the Galapagos Islands
• Saw variations of organisms on the different
islands (thought that this could be
modification due to environment)
– Ex. Finches – beaks shape varied
– Ex. Tortoises – neck length varied
Support for Evolution
1) Fossil Record
2) Comparative Anatomy
3) Comparative Embryology
4) Comparative Biochemistry
5) Geographic Distribution
1) Fossil Record
• Offers some of the most significant evidence
of evolutionary change
• Determines ancestry of organisms
• Reveals patterns of evolution
Whole organism
Cast fossil
Archaeopteryx – earliest bird
(had reptilian and bird –like
characteristics
**It was only 50 centimeters from wingtip to
wingtip (about 19 inches)
2) Comparative Anatomy
• Homologous Structures – same
structure, different function (inherited
from common ancestor)
• Analogous Structures – different
structure, same function (not inherited
from common ancestor)
• Vestigial Structures – reduced forms of
functional structures
Vestigial Organ
3) Comparative Embryology
• Shows evolutionary relationships
4) Comparative Biochemistry
• More similar DNA, more similar the organisms
(remember DNARNAprotein – made of
amino acids)
5) Geographic Distribution
• Animals that live close together are more
closely related than those that are
geographically separated
South American Mara
English Rabbit
How do the following support the
theory of evolution?
1) Fossil Record
2) Comparative Anatomy
3) Comparative Embryology
4) Comparative Biochemistry
5) Geographic Distribution
Adaptation
• While Darwin used all of the previous support
for Evolution (except Biochemistry), the
concept of adaptation is at the heart of his
theory
Adaptation
• Fitness
–The more an organism “fits” into its
environment, the longer it will
survive, the more offspring it will
have, and it’s genes will be passed
on to the following generations
Adaptation
• Camouflage –
blend to environment
Adaptation Can Cause Variation
in a Population
West African giraffe
Reticulated giraffe
Thornicroft’s giraffe
Adaptation
• Mimicry – one species evolves to resemble
another species
Monarch tastes bad
Mechanisms of Evolution
• Population Genetics
Hardy-Weinberg Principle – states
that a population can be in
equilibrium if forces do not cause
the population to change (very rare!)
–The following slides will discuss the
ways a population can change
Genetic Drift
• Any change in a population due to
chance
• Includes:
– Founder Effect
– Bottle Neck
– Gene Flow
– Non-random mating
– Mutation
– Natural Selection
Founder Effect
• When a small group of a
population moves to another area
–These “invaders” rarely have a
complete sample of the genes from
the larger population
–Therefore, the new generation will
have less genetic diversity than the
original population
Dunkers of Eastern Pennsylvania





Protestant sect that fled Germany to avoid
religious persecution
Only married within their sect
In Germany, 45% of people had type A
blood
In the U.S., 40% of people had type A
blood
In the new Dunker population, 60% of
people had type A blood
Bottleneck Effect
• Occurs when populations are
depleted. Even if populations are
restored, they will only have
remnant of the original gene pool.
– Ex. Cheetahs
due to ice age 10,000 yrs ago
– Ex. Elephant seals
due to hunting
Gene Flow
• Movement of individuals in or out of a
population will change the available genes
Nonrandom Mating
• Individuals can only mate with those nearby
• This narrows the gene pool
Mutation
• Random change in DNA causes changes in
traits
• Provides the “catalyst” for natural selection to
occur
Natural Selection
• Process in which organisms with favorable
traits (traits well suited for their environment)
are more likely to survive and reproduce
Survival of the Fittest or the “Sexiest”
Why are brown beetles more
abundant in a population?
• Imagine that green beetles are easier for birds to spot
(and hence, eat).
• Brown beetles are a little more likely to survive to produce
offspring. They pass their genes for brown coloration on to
their offspring.
• So in the next generation, brown beetles are more
common than in the previous generation.
Why?
Show Two Minute Video
“Why Sex?”
http://www.pbs.org/wgbh/evolution/sex/index.html
4 Ways Natural Selection Can Change a
Population
1) Stabilizing Selection – extremes are selected
against, typical in organisms that have
changed little over millions of years
3) Directional Selection – an extreme is selected
Ex. Peppered Moth and industrial revolution
Investigation from Arkive
• Read the handout
Natural selection – the peppered moth
Pale coloured, speckled peppered moth
Natural selection – the peppered moth
Dark coloured peppered moth
Natural selection – the peppered moth
Peppered moths on tree trunk
2) Disruptive selection – selects against
intermediate forms and produces two subpopulations
Ex. White vs. black snails
• White snails will not be easy prey on sand
but easily spotted on rocks or dark algae
• Black snails will not be easy prey on rocks
but easily spotted on sand
• Intermediates (brown) are easy prey in
either area
4) Sexual Selection –
males and females
differ in their
appearance with
males typically more
“flashy” to attract
more females
Speciation
• Sometimes gene changes become so
great that new species are formed
• 2 types:
–Allopatric Speciation – new species are
created due to geographic isolation
–Sympatric Speciation – new species are
created due to changes in behavior
(food source, mating rituals)
Allopatric
Speciation
Patterns of Evolution
1) Adaptive (Divergent)
Radiation
2) Convergent Evolution
3) Coevolution
4) Rate of Speciation
Adaptive (Divergent) Radiation
• New species evolve
from a common
ancestor
• Revealed by
homologous structures
Convergent Evolution
• Process by which
unrelated organisms
come to look a like
because of similar
environment
• Analogous structures
Coevolution
• Two species that evolve together because of
their close interaction
Rate of Speciation
• Gradualism – evolutionary changes
occur steadily over time
• Punctuated Equilibrium – Long
period of time of stasis, short
periods of change
Review
• Describe:
– Founder Effect
– Bottle Neck
– Gene Flow
– Non-random mating
– Mutation
– Natural Selection
(We will go over this orally…..you already
wrote this in your notes)
Review
• Describe the 4 ways that natural
selection can change a population
• Describe the 2 types of speciation
• Describe the 4 patterns of evolution
• Describe the 2 rates of speciation
Animation
• Evolution