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Evolution
Natural Selection
Theory
► What
is a theory?
 A scientific theory is a well-supported testable
explanation of phenomena that have occurred
in the natural world.
► Theory
of evolution
 Evolution is the process by which modern
organisms have descended from ancient
organisms. Species has changed over time.
Charles Darwin
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

Voyage of the Beagle
In 1831, Darwin set sail from England aboard the H.M.S.
Beagle for a voyage around the world.
Darwin returned 5 years later in 1836
Observations
During his travels, Darwin made numerous
observations and collected evidence that led him
to propose a hypothesis about the way life
changes over time.
► He observed many plants and animals were well
suited to the environments they inhabited.
 Darwin was puzzled by where different species
lived and did not live.

Darwin's Observations
Living Organisms and Fossils
Darwin collected the preserved remains of ancient
organisms, called fossils.
Some of those fossils resembled organisms that were
still alive.
Others looked completely unlike any creature he had
ever seen.
Darwin's Observations
The Galápagos Islands
Darwin observed that the Galápagos Islands were
close together but had very different climates.
Copyright Pearson Prentice Hall
The Journey Home
Darwin observed that the characteristics of
many animals and plants varied noticeably
among the different islands of the Galápagos.
Tortoises
The Journey Home
Darwin wondered if animals living on
different islands had once been members of
the same species.
These separate species would have evolved
from an original South American ancestor
species.
Those that helped Darwin’s idea
Hutton and Lyell both geologists (Earth
millions of years old.
► Hutton
 1795 published theory
about geological forces
that have shaped Earth.
 Layers of rock form
slowly.
 Mountains formed from
sea floor
► Lyell
 Gave Darwin book
Principles of geology
 Scientists must explain
past events that have
shaped the earth.
 Made Darwin think if
the earth can change
over time what about
life?
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
13
Lamarck’s Theory of Evolution
► Inheritance
Of Acquired Traits
 Traits Acquired During Ones Lifetime
Would Be Passed To Offspring
14
Clipped ears of dogs could be passed to offspring!
Lamarck’s Mistakes
►Lamarck
Did NOT Know how traits
were inherited (Traits are passed
through genes)
►Genes Are NOT Changed By Activities
In Life
►Change Through Mutation Occurs
Before An Organism Is Born
15
Thomas Malthus
►
What was Malthus' theory of population
growth?
 1798 observed that babies were being born
faster than people were dying.
 Malthus reasoned that if the human population
continued to grow unchecked, sooner or later
there would be insufficient living space and food
for everyone.
Publication of On the Origin of
Species
He shelved his manuscript for years and
told his wife to publish it in case he died.
► In 1858, Alfred Wallace sent an essay to
Darwin for review. Wallace’s ideas
summarized Darwin’s work.
► In 1859, Darwin published his book, On the
Origin of Species.
►
In his book…
Proposed a mechanism for evolution called
natural selection.
► Presented evidence that evolution has been
taking place for millions of years—and
continues in all living things.
► Artificial selection is the selection by
humans for breeding of useful traits from
the natural variation among different
organisms.
►
► https://www.youtube.com/watch?v=xOl0tH
VV6Ck
The Struggle for Existence
►
Darwin realized that high birth rates and a
shortage of life's basic needs would force
organisms to compete for resources.
► How
is natural selection related to a species'
fitness?
Survival of the Fittest
The ability of an individual to survive and
reproduce in its specific environment is
fitness.
► Darwin proposed that fitness is the result of
adaptations.
► An adaptation is any inherited characteristic
that increases an organism's chance of
survival.
►
Natural Selection
Because of its similarities to artificial
selection, Darwin referred to the survival of
the fittest as natural selection.
► In natural selection, the traits being
selected contribute to an organism's fitness
in its environment.
►
Natural Selection
Over time, natural selection results in changes in
the inherited characteristics of a population. These
changes increase a species' fitness in its
environment.
► Natural selection is the process by which
individuals that are better adapted to their
environment are more likely to survive and
reproduce than other members of the same
species.
►
►
Descent with Modification
Natural selection produces organisms that
have different structures, establish different
niches, or occupy different habitats.
► Each living species has descended, with
changes, from other species over time.
► Darwin referred to this principle as
descent with modification.
►
5 parts to natural selection
►Overproduction
►Competition
►Variations
►Adaptations
►Speciation
Overproduction
► Most
species produce far more offspring
than can possibly survive.
► Each year a female sea turtle lays over 100
eggs.
► Why isn’t the sea full of sea turtles?
Competition
► Since
food and other resources are limited,
the offspring must compete with each other
to survive.
► Only a few turtles will survive long enough
to reproduce.
Variation
Crossing-over increases the number of
genotypes that can appear in offspring.
► Sexual reproduction produces different
phenotypes, but it does not change the
relative frequency of alleles in a population.
►
Adaptation
Some organisms are better adapted to their
environment.
► Fitness – the ability of an individual to
survive and reproduce in its environment
due its traits
► Survival in nature – live long enough to
pass genes on to offspring.
► Traits that make organisms successful are
passed to the next generation
►
Speciation
a new species is created when enough time
has passed
► over time, variations that make a species
successful accumulate
► Eventually, the entire species is different
than it was.
►
Evolution of a Population
A population is a group of individuals of the
same species that interbreed.
► A gene pool consists of all genes, including
all the different alleles, that are present in a
population.
► The relative frequency of an allele is the
number of times the allele occurs in a gene
pool, compared with the number of times
other alleles for the same gene occur.
►
Genetic variation
In genetic terms, evolution is any change in
the relative frequency of alleles in a
population.
► The two main sources of genetic variation
are mutations and the genetic shuffling that
results from sexual reproduction.
►
Mutation
►A
mutation is any change in a sequence of
DNA.
► Mutations occur because of mistakes in DNA
replication or as a result of radiation or
chemicals in the environment.
► Mutations do not always affect an
organism’s phenotype.
Populations NOT individuals
Natural selection affects which individuals
survive and reproduce and which do not.
► Evolution is any change over time in the
relative frequencies of alleles in a
population.
► Populations, not individual organisms, can
evolve over time.
►
Peppered Moth
► The
Industrial Revolution began in England
in the late 1700s.
► Smoke from the factories blackened the tree
trunks of trees.
► Light colored moths were no longer
camouflaged.
► What color was more suited for the new
environment?
More on Speciation
► Speciation
is the formation of new species.
► A species is a group of organisms that breed
with one another and produce fertile
offspring.
How do New Species Form?
► Geographic
Isolation
► Continental Drift
► A new species may form when a group of
individuals remains separated from the
rest of its species long enough to evolve
different traits.
 A group is separated from the rest of the
species
Video
► Darwin
Evidence of Evolution
•1. The fossil record
•2. Comparative anatomy
•Homologous structures
•3. Similarities in early
development, or embryology.
Fossil Record
►A
fossil is the preserved remains or traces of
an organism that lived in the past.
► A fossil can be formed from parts of live
organisms, foot prints, or burrows left in
mud.
► Actual age of fossils is determined by
radioactive dating
Fossils
► Ice
preservation
► Tar pit
► Tree sap hardens to
form amber.
► Imprint fossils
► Cast fossils
► Mineralized fossils
video
► Fossil
► https://www.youtube.com/watch?v=lIEoO5
KdPvg
► Most
fossils are found in
sedimentary rock – formed
when water flows over land,
► Carrying
the sediment (and
whatever life form) into a
body of water.
► Over
time pressure turns
the sediment into rock,
preserving what’s inside.
Comparative Anatomy
► Similar
body parts show an evolutionary
relationship
► Homologous Body Structures – same bone
structure but different functions.
► Vestigial Organs – organs or traces of
organs that serve no purpose.
►Example:
Humans: appendix, tailbone, wisdom
teeth, and Goosebumps
Homologous Body Structures – same
bone structure but different functions.
Similarities in early development,
or embryology
► The
study of embryos
and their development
► The similarities
suggest an
evolutionary
relationship among all
vertebrate species.
Speed of evolution
2 theories
► Gradualism-
Described
as a slow ongoing
process by which one
species changes to a
new species
► Punctuated
Equilibrium- One
species suddenly
changes to another.
Graphs showing time frame of Evolution:
►Gradualism:
#
S
P
E
C
I
E
S
► Punctuated
Equilibrium
Time
#
S
P
E
C
I
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S
Time
video
► clip
Relation and common descent
► All
living organisms are related to one
another.
► Common descent – all species – living and
extinct – were derived from common
ancestors.
► Humans did NOT evolve from apes.
► We have a common ancestor that was
neither human nor ape.
► Common
Ancestor: all living organisms have a
common ancestor and all life can be traced back to
one original cell.
► From there life become diverse
► Common ancestor mean that living things can be
traced back to a common relative.
► Example: Humans did not evolve from Apes but had a
common ancestor with them 5 to 8 million years ago.
Branching Trees: Cladograms
►A
branching tree is a diagram that shows
how scientists think different groups of
organisms are related.
Practice questions
►
1. A species of bird known as Bird of Paradise has been
observed in the jungles of New Guinea. The males shake
their bodies and sometimes hang upside down to show off
their bright colors and long feathers to attract females.
Females usually mate with the “flashiest” males. These
observations can be used to support the concept that
►
(1) unusual courtship behaviors lead to extinction
(2) some organisms are better adapted for asexual
reproduction
(3) homeostasis in an organism is influenced by physical
characteristics
(4) behaviors that lead to reproductive success have
evolved
►
►
►
►
2. Agriculturists have developed some varieties of
vegetables from common wild mustard plants, which
reproduce sexually. Which statement best explains the
development of these different varieties of vegetables?
►
(1) Different varieties can develop from a single species as
a result of the recombination of genetic information.
(2) Different species can develop from a single species as a
result of the effect of similar environmental conditions.
(3) Mutations will occur in the genes of a species only if
the environment changes.
(4) Variations in a species will increase when the rate of
mitosis is decreased.
►
►
►
► 3.
Even though identical twins have the same
genetic material, they may develop slightly
different characteristics because
► (1)
each twin receives different chromosomes
from the egg
► (2) one twin may only have genes from the
father
► (3) gene expression may be influenced by
factors that switch genes on and off
► (4) a gene mutation may have occurred before
the zygote divide
►
4. Which statement concerning the evolution of species A,
B, C, D, and E is supported by the diagram below?
►
(1) Species B and C can be found in today’s environments.
(2) Species A and D evolved from E.
(3) Species A and C can still interbreed.
(4) Species A, B, and E all evolved from a common ancestor and all are
successful today.
►
►
►
► 5.
Young birds that have been raised in
isolation from members of their species build
nests characteristic of their species. This
suggests that the nest-building behavior is
► (1)
genetically inherited from parents
► (2) learned by watching members of their
species
► (3) a disadvantage to the survival of the
species
► (4) a direct result of the type of food the bird
eats
► 6.
Which statement provides evidence that
evolution is still occurring at the present time?
► (1)
The extinction rate of species has
decreased in the last 50 years.
► (2) Many bird species and some butterfly
species make annual migrations.
► (3) New varieties of plant species appear more
frequently in regions undergoing climatic
change.
► (4) Through cloning, the genetic makeup of
organisms can be predicted.
► 7.
When a species includes organisms with a
wide variety of traits, it is most likely that
this species will have
► (1)
a high proportion of individuals immune
to genetic diseases
► (2) a greater chance to survive if
environmental conditions suddenly change
► (3) less success competing for resources
► (4) limitless supplies of important resources,
such as food and water
9. Some evolutionary pathways are represented in the diagram below.
An inference that can be made from information in the diagram is that
►
►
►
►
(1) many of the descendants of organism B became extinct
(2) organism B was probably much larger than any of the other
organisms represented
(3) most of the descendants of organism B successfully adapted to their
environment and have survived to the present time