UNIT 5 EVOLUTION
Scientific evidence is information and facts that
are measurable and observable
An inference is a conclusion (or claim) made using evidence, experience, and
prior knowledge
A theory is a well-tested explanation that unifies a broad range of observations,
inferences, principles, laws and hypotheses
Darwin’s Observations
§ You will compile many over the next few weeks, but the
BIG one is this:
§ The GIANT/IMMENSE diversity of life both past and
Darwin’s Inference
§ Evolution- Change over time
§ Biological Evolution- the process by which organisms
But the BIG question that
Darwin only ever began to
answer
§ HOW???
§ For this, Darwin studied Artificial Selection (You know
From Artificial to Natural
§ If humans could select specific traits in dogs and other
domesticated animals then,
§ Perhaps, nature could select specific traits in all
animals.
§ Adaptation- any heritable characteristic that increases
Natural Selection
Principle #1 § Variation
§ Individuals within a population
Natural Selection
Principle #2 § Heritability
§ Some of these traits can be
Natural Selection
Principle #3 § The Struggle for Existence
§ Many more offspring are born
Natural Selection
Principle #4 § Adaptations and Fitness
(“Survival of the Fittest”)
§ The individuals that survive AND
reproduce are those with the traits best suited to the
The Hunger Games
"The Careers have two pairs. But they've got everything down by the lake," Rue says. "And they're so strong.” "We're strong, too," I say. "Just in a different way.”
"You are. You can shoot," she says. "What can I do?” "You can feed yourself. Can they?" I ask.
"They don't need to. They have all those supplies," Rue says.
"Say they didn't. Say the supplies were gone. How long would they last?" I say. "I mean, it's the Hunger
Natural Selection and
Mutation
§
Evolution by natural selection depends on
heritable variation.
§
Where does this heritable variation come
from?
§
Could a population evolve if there were not
different alleles for every gene?
What Can DNA Tell Us
About Our Ancestors?
§ By studying DNA sequence we can tell how
closely different species are related even if they look very different.
§ In Nature on 8 May 2008, DNA sequencing
revealed both reptilian and mammalian
elements, as well as two genes found previously only in birds, amphibians, and fish. More than 80% of the platypus' genes are common to the other mammals whose genomes have been
What Can Proteins Tell
Us About Our Ancestors?
§ Not only does all life share a common code, but itsometimes codes for the same proteins.
§ For this to happen, the protein must be an adaptation
(improve fitness) across environments and across time!
ú Cytochrome C is a protein in cellular respiration and is used from
yeast to humans.
ú The HOX genes guide development and are very similar in all
vertebrates.
§ BONUS! Because of these similarities, we can learn about
human cellular processes by studying yeast (or many more complex animals)
§ Consider that even different groups of humans don’t share
Where Did All Those Genes Come
From?
§ If life began as a single celled organism with a few genes,
you might wonder where all the genes came from in more complex organisms.
§ Gene duplication: During meiosis, sometimes a
chromosome can end up with two copies of the same gene (1 from mom and 2 from dad)
ú This extra copy can acquire mutations to alter its function, while
the original copy does its original job.
JAN 29 QUIZ
1. Scientific evidence is observable and ___________.
2. Darwin’s idea that “species change” is an example of evidence / inference / theory?
3. T/F “For evolution to be observed in real time, test organisms must be large and easily contained.”
4. Name one person who influenced Darwin’s thinking.
5. Dog breeding is one type of “artificial ___________.”
6. Evolution is the process of “change over ________.”
7. T/F Fitness does not require physical strength.
8. Any trait that improves fitness is called an ________.
9. More organisms are born than can ________.
10. Which of these is not a principle of natural selection: variation, mutation, heritability
EVOLUTION OF POPULATIONS
Alternatives to Natural
Selection
§ Allele frequencies can change without natural selection
ú Bottlenecks: An event that leads to a
significant decrease in population. Genetic diversity is reduced and allele frequency is changed.
ú Example: Hunting the American Bison
drastically reduced its numbers which has resulted in less genetic diversity (a smaller selection of alleles)
ú Example: All cheetahs are so closely related
§
Founder Effect: When a small group
colonizes a new area, the offspring are
limited by the alleles in that small group.
ú Example: A very high percentage of the FLDS
community are the descendents of two men. In this population there is a growing incidence of fumerase deficiency an extremely rare
condition that causes severe mental retardation.
ú Example: In the Amish population there is a
Antibiotic Resistance
§
MRSA Reading
1. First read-through:
a. Circle at least 3 words you don’t know
b. Write at least 2 questions you have (either clarifying or expansion)
2. Second read-through:
a. What does MRSA stand for?
b. What was the selective pressure that caused this strain of bacteria to
become resistant?
c. How can we “change evolution” to avoid this in the future?
d. What type of “translational” research is TGen involved in?
3. With a partner:
a. Write a 4-sentence summary describing the problem, how it relates to
evolution, and a possible solution.
4. At home:
DARWIN’S EVIDENCE FOR
EVOLUTION
Biodiversity
§ Darwin wondered how
to explain the
enormous diversity of life on earth.
§ Make a table in your
notes to record
Geologic Time
§ Unimaginable amounts of time would be
required for the slow process of evolution by natural selection.
§ The geologic time scale is evidence that this
amount of time was available.
§ The exact ages of layers of rock is determined by
radiometric dating
Geologic
Time and
Fossils
§
Earth is
Fossil Record
§ The fossil record contains many species that
The Fossil Record
Darwin saw fossils as a record of the history
of life on Earth.
By comparing fossils from older rock
layers with fossils from younger layers, scientists could document that life on Earth has changed over time
Homologous Body Structures
Structures that have different mature forms but
develop from the same embryonic tissues are called homologous structures.
Similarities and differences in homologous
structures help biologists group animals
Vestigial Organs
§ Not all homologous structures serve important
functions.
§ The organs of many animals are so reduced in size
that they are just vestiges, or traces, of
homologous organs in other species. This shows that unneeded organs are not under selective
pressure.
Vestigial Organs
Embryos
§
Similarities in Embryology
ú The early stages, or embryos, of many animals
with backbones are very similar.
ú The same groups of embryonic cells develop in the
same order and in similar patterns to produce the tissues and organs of all vertebrates.
The Genetic Code
§ All life carries instructions in the DNA molecule using
the same 4 nucleotides.
§ The code for making protein from DNA is nearly
identical in all life, despite how DIFFERENT those life forms are.
Feb 18 QUIZ
1. Darwin’s idea that “species change” is an example of evidence /
inference / theory?
2. T/F Mutations are neither good nor bad.
3. T/F Tiktaalik is an example of a transitional organism.
4. Body patterning genes called __ __ __ genes are found in all complex
organisms and are virtually identical. 5. T/F Humans have more genes than corn.
6. Most of Darwins evidence was collected in the ____________ islands.
7. Many differences in the DNA of organisms are not in the genes but in
the _________ that turn genes on and off.
8. A bat wing and a whale fin are examples of _________ structures.
9. The pelvic bone on a whale is an example of a _________ structure.
10. The earth is 4.5 _______ years old.
11. The name of the ship on which Darwin sailed was the HMS
