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Nature of Science
What is Science?
• It uses previous knowledge and
theories to gain new knowledge and
to produce new and better theories
through observations of the natural
world.
What is science?
• Science is a process to build
understanding.
• Example: The earth was once
believed to be flat.
• Do we still think this today? Why?
What science is NOT?
• Is not a system of beliefs
• Does not prove anything! It can
only accept the best explanation at
that time until it is disproved.
What science is NOT?
• Science cannot make decisions
about morals, laws, literature,
visual arts, music, etc.
• It cannot draw conclusions about
things it cannot measure or
manipulate.
Science as moral solution?
• Can science offer a solution to
whether stem cell research is right
or wrong?
• NO! It can offer only information
gained from research and
observations in order for people to
make their decisions.
Hypothesis, Laws, and Theories
• Hypothesis: testable explanation
based on previous observations
• Law: general statement that
describes a natural phenomena
• Theory: explanation of how a law
works
Laws and Theories
• Atomic Theory explains the Law
of Conservation of Mass
• Chromosomal theory of inheritance
explains the Law of Heredity
Science T/F
1. Science is a system of beliefs.
2. Scientists rely heavily on
imagination to carry out their
work.
3. Scientists are totally objective in
their work
Science T/F
4. The scientific method is the
accepted guide for conducting
research.
5. Experiments are carried out to
prove cause-and-effect
relationships.
Science T/F
6. All scientific ideas are discovered
and tested by controlled
experiments.
7. A hypothesis is an educated guess.
8. Scientific ideas are tentative and
can be modified or disproved.
14.1 Darwin Developed a
Theory of Evolution
I. Idea’s From Darwin’s Time
A. Evolution is all of the changes that
have transformed life over time
B. In the mid 1700’s George Buffon
suggested that the Earth is older than
10,000 years old
C. In the early 1800’s Jean Baptiste
Lamarck developed the idea of
Inheritance of Acquired
Characteristics
II. The Voyage of the Beagle
A.
In 1831 The HMS Beagle left England for a
five year voyage around the world
B.Darwin studied the geology, plants, and animals
he encountered
III. Darwin’s Observations
A. Darwin maintained extensive
journals of his observations,
studies and thoughts
B. Darwin noticed the animals
and plants he observed were
uniquely South American
C. Darwin was especially
intrigued by the Galapagos
Islands because of their
diversity
IV. Ideas from Geology
A. Darwin read books from Charles Lyell
that proposed Earth’s features today
could be explained by geological
processes
B. From this Darwin made two conclusions
1. The Earth must be very old
2.Slow and gradual processes occurring over vast
amounts of time could cause tremendous change
V. Darwin Publishes His Theory
A. Over many years after his return,
Darwin developed his theory based on
observations, inferences and ideas
B. In 1844 Darwin wrote a 200 page
essay that outlined his idea
C. In 1859 Darwin released his
findings to the public in the book The
Origin of Species
VI. Darwin’s Two Main Points
A. Darwin’s first point was that the
species of organisms living on Earth
today descended from ancestral
species, Descent with Modification
B. Darwin’s second main point was
that Natural Selection is the
mechanism for evolution
Natural Selection
14.2 Evolution has left much
evidence
I. The Fossil Record
A. Preserved remains or markings left
by organisms that lived in the past are
called fossils
B. The positions of fossils in the rock
strata can reveal relative age
C. The fossil record is this
chronological collection of life’s
remains in the rock layers
Fossil Formation
Fossil Evidence
Basilosaurus
II. Geographic Distribution
A. The differences and similarities
between organisms and different parts
of the world shows how species today
evolved from ancestral forms
B. Geographic distribution gives clues
as to how modern species evolved
III. Similarities in Structure
A. Similar structures in species sharing
a common ancestor are called
homologous structures
B. Vestigial structures are remnants
of structures that may have had
important functions in an ancestral
species, but have no clear function
today
Homologous Structure
IV. Similarities in Development
A. Embryos of closely related
organisms often have similar
stages in development
B. Comparing the development of
organisms supports other evidence
of homologous structures
Embryo
Similarities
V. Molecular Biology
A. The closer two organisms DNA
sequence match, the closer the
relationship
B. DNA and protein analysis are new
tools for testing hypothesis about
evolution
C. There is molecular evidence that
there are common genetic codes
shared by all species
Similar Amino Acids
14.3 Darwin proposed natural
selection as the mechanism of
evolution
I. Darwin’s Theory of Natural
Selection
A. A population is a group of
individuals of the same species in
the same area at the same time
B. Populations in different areas
become more and more different,
leading to new species
II. Observations Lead to A
Question
A. There are 13 species of finches
unique to the Galápagos Islands
B. They most closely resemble one
finch species living on the South
American mainland
III. More Observations Lead to
an Idea
A. Darwin recognized
that all species tend to
produce excessive
numbers of offspring
B. Darwin also
recognized there was
variation among the
individuals of a
population
Stabilizing Selection
Directional Selection
Disruptive Selection
IV. Artificial Selection
A. Artificial selection is the
selective breeding of domesticated
plants and animals to produce
offspring with traits that humans
value
B. You see this change in Dog’s
over the last 500 years
V. Pesticides-Natural Selection
in Action
A. When a new pesticide is sprayed
it will kill about 99% of the insects
targeted
B. As time goes on, more insects
are resistant to the pesticide
Pesticides- natural selection
C. This illustrates two key points
about natural selection
1.natural selection is a “screening” of the traits
available
2.natural selection favors those characteristics in
a varying population that fit the specific
current, local environment
Pesticide Resistance
14.4 Microevolution is a change
in a population’s gene pool
I. Populations and Their Gene
Pools
A. A population is the smallest level
at which evolution can occur
B. The gene pool consists of all the
alleles in all the individuals in a
population
II. Changes in Gene Pools
A. Natural selection is not
random
B. Microevolution is a change
in the frequencies of alleles
from generation to generation
C. The Hardy-Weinberg
Equilibrium is when a
populations gene frequencies
are not changing, i.e. not
evolving
III. Genetic Drift
A.
A change in the gene pool due to chance is
called genetic drift
B.The smaller the population the greater the impact
C.The Bottleneck Effect is when a disaster reduces
the size of a gene pool
D. The Founder Effect is when a few individuals
colonize a new habitat
Bottleneck Effect
Cheetahs
IV. Gene Flow and Mutation
A. The exchange of genes with
another population is called gene
flow
B. A mutation is a change in an
organism’s DNA
V. Natural Selection and
Darwinian Fitness
A. Natural Selection is a blend of
chance and sorting
B. Darwinian Fitness is the
contribution of one individual to
the gene pool compared to others
VII. A Return to the Galapagos
A. Peter and Rosemary Grant have
studied finches on Daphne Major
in the Galapagos
B. Their data has provided clear
evidence of natural selection
Finches
14.5 Evolutionary Biology is
important in health science
I. Natural Selection and Sickle
Cell Disease
A. Sickle Cell disease is a recessive
disorder which affects the shape of
red blood cells at a rate of 1 out of
25 people in some African
populations
Natural Selection and Sickle Cell
Disease
B. Individuals with one copy of the
allele are resistant to developing
malaria
C. Natural Selection has selected
for those individuals which are
resistant even with the negative
affects of the sickle cell allele
Malaria Life Cycle
Distribution of Malaria
II. Evolution of Antibiotic
Resistance in Bacteria
A. Antibiotics kill or slow the growth
of bacteria
B. An antibiotic will kill most of the
bacteria in a population but leave those
which are resistant behind soon a
greater percentage of the bacteria is
resistant to the antibiotic
Antibiotic Resistance in Bacteria
C. In New York City, there are strains
of the bacteria which causes
Tuberculosis which are resistant to all
three antibiotics used to treat the
disease
D. The overuse of antibiotics is the
speeding up the evolution of these
strains
Flesh eating bacteria