Transcript Organic Evolution

Tuesday 3/17/15
• AIM: How are species related?
• DO NOW: Why do scientists develop
theories? Are theories facts? Why or why
not?
• HOMEWORK: Text read pages 375377.Reading check pages 375 and 377
Theory
• An explanation to a natural phenomena
• After a hypothesis is tested and yields the
same results theories are developed
• Theories change if scientific results
change
– Ex: abiogenesis: life just appears randomly
– NOT TRUE
Scientific theory of the origin
of life
Francisco Redi:disproved
abiogenesis
Louis Pasteur
Louis Pasteur
• Pasteurization: boils liquids to kill microbes
• He found microscopic organisms live in
the air and water surrounding us
1920’s Alexander Oparin and John
Haldane: postulated conditions of
early earth
Theory of primordial Soup
• Hypothesized the early conditions of earth
• Boiling oceans, volcanic eruptions, lightning
storms
• Atmospheric gases methane (CH4),
ammonia (NH3), hydrogen (H2), and water
(H2O).
• Energy sources electric current through
lightning storms and sun’s UV light
• Early earth’s conditions interacted to form
amino acids and small nucleic acids
Tuesday 5/5/14
• AIM: How were the first cells developed?
• DO NOW: What were the conditions of
early earth? Could you survive in them?
• HW: Textbook read pages 380-381. RC
page381
1953 Stanley Miller and Harold Urey
Miller and Urey
• Actually created a closed system
simulating early earth conditions
• Observed small simple organic
compounds were formed
– Amino acids
– Nucleic
• Supports primordial soup hypothesis
From amino acids to the protocell
• Amino acids
combines to form
proteins
• Proteins evolved into
RNA
• RNA into DNA
• Somehow cell
membranes were
synthesized it is still
unclear how
How did the first types of cells
develop?
• Small organic compounds combine to create
some types of membrane surrounding
molecules and nucleic acid
• This was called a protocell
Wednesday 3/18/15
• AIM: What is the scientific explanation for
the origin of life?
• DO NOW: In your own words explain the
scientific explanation of the origin of life by
primordial soup.
• HOMEWORK: Text read pages 375-377.
Answer the reading check questions on
pages 375 and 377
First cells
• Prokaryotes: no
nucleus
• Most likely
archaebacteria
How then did we go from single
celled prokaryotes to
eukaryotes?
Lynn Margulus: endosymbiont
theory
• 1960’s explains how eukaryotic cells arose
• Eukaryotic cells evolved from symbiotic
relationships with prokaryotic cells
• Evidence is seen in the DNA of both
chloroplasts and mitochondria of
eukaryotes which has more similarities to
prokaryotic DNA and not eukaryotic
Alternative theory of origin of life:
Deep sea vents
• Life originated in the
hydrothermal volcanic
vents in the deep sea
• Chemosynthesis: used
the digestion of living
things to make food
• Photosynthesis uses light
To make food
• Chemosynthesis uses
digested molecules to
make food
Assessment
• In your own words explain the scientific
explanation of the origin of life by
primordial soup
 AIM: What are some pieces of evidence for
evolution?
 DO NOW: In your own words explain the
scientific explanation of the origin of life.
 Homework: Textbook Read pages 423-426
questions 3 and 4 pg 430
Organic Evolution
Organic Evolution
• The central idea of biological evolution is that all life on
Earth shares a common ancestor, just as you and your
cousins share a common grandmother.
• Biological evolution, simply put, is descent with
modification.
• Small-scale evolution (changes in gene frequency in a
population from one generation to the next)
• Basically offspring displays different traits than parents
• Large-scale evolution (the descent of different species
from a common ancestor over many generations).
Organic evolution
• Looks at the mechanism of change
• How does change happen
Thursday 3/19/15
• AIM: How do scientists determine common
ancestry?
• Do NOW: What is descent with modification?
• HOMEWORK: text read 380-381. reading
check on page 381
Darwin’s descent with modification
• Each generation shows a slight variation
from the prior
• Successful variations remain in the gene
pool
• Unsuccessful variations are removed
Organic Evolution
a) Changes in the genetic characteristics
of a population over generations
b) Genetic changes alter:
proteins produced by organism
c) Changes in proteins affect the
physical trait
species
• A group of organsims capable of mating
and producing fertile offspring
Family Tree Diagrams
a) used to show probable
evolutionary
relationships
b) some interpretations
c) multiple species can
evolve from a single
ancestor
d) many species have
become extinct
Evolution
• Change over time
• Natural selection vs Artificial Selection
• Natural selection: environmental
conditions are the selecting agents
• Artificial selection: humans are the
selecting agents
Theory of evolution by Natural
selection
• Nature chooses the physical trait best fit
for survival
Evidence for Evolution
I. Fossils
Evidence of a living thing
show structural changes (skip to slide 48)
II. Comparative Sciences
• result from common ancestry
• the greater the similarity, the closer the
evolutionary relationship and the more
recent the common ancestor
• III. The geological record
• IV. Biogeography (Pangea)
Fossil Formation: law of
superposition
• The relative age of a
fossil is determined by
the layer of rock it is
found in
• Lower layers are older
than top layers
• Older. Simple
organisms(lower layers)
are common ancestors
to more complex (upper
layers)
Comparative Studies looks
for Similarities
Between Species
1.
2.
3.
4.
Cytology
Anatomy (structure)
Development embryology
Biochemistry
Friday 3/20/15
• AIM: what are some pieces of evidence to
change over time?
• DO NOW: explain how the fossil record
can help determine common ancestry
• Comparing fossils in the same layer as
well as to prior layers allows us to
determine relatedness
Cytology
a) cells with similar organelles appear in
virtually all species
b) similarities in cell structure suggest that
all organisms may have evolved from a
single ancestor
Comparative anatomy
• Compares the physical structures of
organisms within different species
– Homologous structures
– Analogous Structures
– Vestigial
Tuesday 3/24/15
• AIM: How can we determine common ancestry
by analyzing physical structures?
• DO NOW: Choice 1: List and describe the
different branches of comparative sciences
• CHOICE 2: 1- Comparative __________
analyzes the developing embryos of different
species.
• 2- _____________ structures are similar in
both structure and function.
• 3- Comparative biochemistry studies ________.
• HOMEWORK: Evidence of evolution analysis
Pair and share
• 1- Which comparative study analyzes
homologous and analogous strutures?
• 2- What information can we get through
the analysis of homologous and analogous
structures?
Comparative anatomy
• Compares the anatomical structures of
different species to try and determine a
common ancestor
Homologous Structures
a) structures in different
species that are truly
similar and develop in
the same way
b) ex: vertebrate
forelimbs
c) result from common
ancestry
d) may now be used for
different purposes
Analogous structures
• Similar in function but not structure
• Gives evolutionary information about the
natural environment the organisms were
exposed to
• Does not give common ancestry
• Ex: wing of butterfly (chitin)
– Wing of bat (bones)
Vestigial Structures
(Vestiges)
a) useless structures “left over” from
ancestors
b) ex: snakes have small leg bones
inherited from their lizard ancestors
c) human vestiges include:
•
appendix
•
coccyx (tail bones)
• tonsils
Comparative Embryology
a) different species go
through similar stages of
early development
Studies the embryological
development of
organisms
• AIM: how is common ancestry
determined?
• DO NOW: explain how the fossil record
can show common ancestry
• Explain what information we get from
analogous structures
ComparativeBiochemistry
a) different species have many of the same
genes (DNA sequences) and produce
similar proteins
b) provide the most precise information for
determining evolutionary relationships
Comparing DNA Sequences
For A Specific Protein
Species #1: ATC CTA GCC TTT AAA
Species #2: ATC CTT GCC TAT AAA
Species #3: ATC CTA GCC TTT AAA
Species #4: ATT CTT GCG TAT AAA
1. Which two species are most closely related?
Answer: #1 and #3
2. Species #3 is _______closely related to
species #4 than it is to species #2
Answer: less
AIM: how is common ancestry
determined
DO NOW: What is the closet
common
ancestor of species I and N?
Which species became extinct?
Biogeography
• Looks at the location of
species and their
environment
• Pangea: the
supercontinent
• Plate tectonics
• Species found in similar
climates all over the
world have similar
characterisitcs
The geological time scale
• Derived from the
examination of fossils
• Explains major
geological and
biological events in
the earths history
Divides into 4 major eras
• Precambrian Era: Life
beginsautotrophic prokaryote
eukaryotes multicellular eukaryotes
• Paleozoic Era: Cambrian explosion:
ancestors of most animal groups.
• Mesozoic Era: Dinosaurs. K-T boundary
• Cenozoic Era: Mammals. Humans
Extinction
• Each era ended with mass extinction
• Extinction: all individuals within a species
dies forever!!!!
– The species is never seen again in
evolutionary history
• If there is not a variant within a species to
survive an extreme change in environment
then the species becomes extinct
So how do new species arise?
Speciation
• The evolution of two or
more species from a
common ancestor
Important example:
the Evolution of Finches
on the Galapagos
islands
Mechanisms for speciation
• This attempts to explain how new species
develop from ancestor species
• Gradualism or Punctuated equilibrium
Gradualism vs Punctuated
equilibrium
• Both processes are referring to the
development of new species caused by
natural selection
• In gradualism slight changes in each
generation lead to a longer, slower speciation
process
• In punctuated equilibrium an extreme
environmental change caused a rapid shift in
the gene pool leading to a quick speciation
• SPECIATION
•
develop of a
new species from
a previously
existing species
Thursday 3/26/15
• AIM: How do fossils provide evidence for
evolution?
• DO NOW: 1- Take out your lab!!!!
• 2-What are homologous structures?
• 3-How do they give evidence to a common
ancestor?
• CHOICE 2: 1-______ are similar in both
structure and function.
• 2- _______ tell us there were similar
environmental stresses but not common
ancestor which led to the development of the
Two Theories About the Rate of
Evolution
1. Gradualism
species evolve slowly and steadily
(traditionalists like Darwin believe in gradualism)
2. Punctuated Equilibrium
species may remain relatively stable for
many
generations and then change
dramatically in a
short period
Both theories may be correct:
some species have evolved gradually while
others may have evolved in abrupt spurts
Fossil Evidence for
Evolution
Fossils are:
• naturally preserved
remains of dead
organisms
• show structural
changes resulting
from evolution
Fossils are found in:
•
•
•
•
•
1. Sedimentary Rock
2. Burgess shale
3. Ice
4. Tar
5. Amber
Types of Fossils
1. Complete organisms Molds and
casts
can be preserved in ice, tar or amber
2. Partial remains (ex: skeleton)
3. Imprints or trace fossils
impressions left by organism
4. Petrified fossils
gradual absorption of minerals turns
the
remains into a stone like
material
Fossil Samples
• Trace fossils
• Mold and cast
• Petrified fossils
• Replacement
• Amber
• Frozen
Fossil Formation
• Sedimentary Rock
• Burgess Shale
• AIM: how does the geological time scale
create a timeline for the origin of life
• DO NOW:In your own words explain how
fossils give us insight to common ancestry.
• HOMEWORK: Textbook pages 441-443
questions 1-8. WRITE OUT THE
QUESTION FOLLOWED BY THE
ANSWER
Determining The Age of
Fossils Relative dating:
1. Rock Layer
Positions
in undisturbed layers of
sedimentary rock
the law of superposition
the deeper the layer,
the older the rock (& the
older & simpler the
fossils)
2. Index Fossils
a) The age of these fossils is known
b) Other fossils found in same layer are the
same age
The fossils found in layer B resemble the fossils found in
layer A. This similarity suggests that
• 1-the fossils in layer B were formed before the fossils in
layer A
• 2-modern forms of life may have evolved from earlier
forms of life
• 3- vertebrate fossils are only found in sediments
• 4-the fossils in layer A must be more complex than those
in layer B
•
• Explanation: These fossils demonstrate
gradualism, the theory on the time frame
of evolution that states that species
gradually change over time. Since the
fossils are found in different layers of
sedimentary rock, the older layer contains
species that evolved into newer species
with some changes in the newer layer of
rock.
3. Radioactive Dating of
Fossils
1. All living organisms maintain small of
amounts of radioisotopes (ex: Carbon 14)
2. After death, radioisotopes change into nonradioactive “decay” products
3. Ratio of decay product to radioisotope
increases over time and can be used to
estimate fossil’s age
4. Half life: the amount of time it takes for half
of the atoms of a radioactive element to
decay
If the half-life of carbon-14 is
5800 years, how old is this
specimen after 3 half lives?
5,800 yrs
11,600 yrs
17,400 yrs
Half Lives
Radioisotope
Decay Products
O
2000 grams
O
1
1000 grams
1000 grams
2
500 grams
1500 grams
3
250 grams
1750 grams
Conclusions Based on
Fossil Record
1. Earth is about 4.5 Billion old
2. First organisms were bacteria and evolved
about 3.2 Billion years ago
3. Biodiversity (the variety of different species)
has increased
4. Organisms have become more complex
5. Most species became extinct
6. Life first evolved in the water, land
organisms evolved more recently
Adaptation to Environment
Because organisms with superior traits
produce more offspring than organisms
with inferior traits the next generation will
have…
a) a higher % of superior characteristics
and a lower % of inferior characteristics
and …
b) be better suited to it’s environment
• AIM: How does an entire new species
evolve from a parent species?
• DO NOW: Handout. Observe the pictures.
Explain what is happening from picture 15. Which individuals survive and explain
WHY.
• Homework: page 453 Reading check
• Exam Friday
If the earth’s history (4.5 Billion
Years) was compressed into 1 day
• 12:00:01 AM - formation of the earth
• 7:00 AM – life begins (prokaryotic
bacteria)
• 2:00 PM –first eukaryotic organisms
• 6:30 PM – first multicellular organisms
• 10:00 PM – first land organisms
• 11:59: 58 PM – humans evolve
• If you were trying to determine the age of
a fossil, would you rather use relative or
radiometric dating? Why or why not?
Monday 3/30/15
• AIM: How does an entire new species
evolve from a parent species?
• DO NOW: What are the different pieces of
evidence for evolution?
• What are the 2 mechanisms of evolution?
• HOMEWORK: Read 386-389. answer
Reading check on page 387 and question
1 on page 389
Review
•
•
•
•
The fossil record
Comparative Sciences
The geological time scale
Biogeography
• How does the biogeographical location of
a species give evidence for evolution?
What is speciation?
Development of a new species
from a pre-existing species
How are physical traits
created?
Genes code for physical traits
Peppered Moths
• 1- Before Industrial
Revolution light
color was best fit for
survival
• After Industrial
Revolution
2. Air pollution caused soot
to accumulate in major
cities
3. In polluted areas, light
colored moths were
more likely to be eaten
by birds
4. Moths evolved from
mostly light to mostly
dark color in a short
period
5. There was a shift in the
Comparing Gene
Frequencies
Why are these gene
frequencies changing?
“A” increases chances of
survival and is more
likely to be passed on
to offspring
Tuesday 3/31/15 DO NOW:
Homework Due Tuesday
4/14/15
• Textbook pages 393-395 questions 1-12.
• On a sheet of loose leaf, write the number
and your answer choice
• EX:
• 1-3
• 2-4
• 3-2
Adaptations
• adaptation in biology is a trait with a
current functional role in the life history of
an organism that is maintained and
evolved by means of natural selection
• Adaptations usually occur because a gene
mutates or changes by accident
• Structural adaptations
• Behavioral adaptations
Mimicry
Mimicry
• One species looks or acts like a different
species in order to increase survival
• Structural adaptation for survival
Camoflauge
• Physical traits
resemble
environmental
surroundings so the
organism can blend in
Behavioral adaptations are the
things organisms do to survive
• Ex: birds migrate south in the winter
Adaptations are changes
• Changes are caused by mutations
– Changes in the gene
– Shift in the gene frequency of the population
– Continuous mutations can lead to speciation
• Development of a new species
3 Steps in Speciation
Geographic Isolation
Adaptive Radiation
Reproductive Isolation
#1-Geographic Isolation
Ancestral species is split up into separate
populations by physical barriers that
prevent interbreeding
Physical Barriers include:
mountains, rivers, deserts, bodies of
water
#2-Adaptive Radiation
Isolated populations begin to evolve in
different directions due to:
A. Natural Selection
(they adapt to different environments)
B. Genetic Drift
(random events)
Genetic Drift
Changes in a population resulting from
random events like:
1. Founder Effect
initial differences between groups founder
population is majority
2. Different Mutations occur in each group
3. Sexual Reproduction produces different
combinations in each group
4. Accidental Deaths
Animations
Genetic drift Founder effect
Genetic drift: Founder Effect
• When a small part of a population moves
to a new locale, or when the population is
reduced to a small size because of some
environmental change,
• the genes of the "founders" are the
majority
• EX: Polydactyl (6 fingers) Amish people
Wednesday 4/1/15
• DO NOW: what is speciation?
• 2- how does speciation happen?
• HOMEWORK: Textbook pages 393-395
questions 1-9,11 and 12.
• On a sheet of loose leaf, write the number
and your answer choice
Genetic drift: bottleneck effect
Genetic drift: bottle neck effect
• There is a shift in the
observable traits due
to some type of event
that eliminates many
individuals within a
species
• The new surviving
population does not
resemble the original
population
Genetic drift: bottle neck effect
• Original population
has a large genetic
diversity
• New population has
small genetic diversity
#3-Reproductive Isolation
a) Groups have become so different that
they can no longer interbreed if
reunited
b) May result from differences in anatomy,
behavior, body chemistry,mating
season, chromosome content
c) Isolated groups are now considered to
be separate species
The graph below shows changes
in the populations of two species
that interact only with each other
over a period of time. In a
complete sentence describes the
two species.
B
A
Monday
• AIM: How does evolution work?
• DO NOW: If you were a hawk looking for
food, which of the rabbits would you dive for
and why?
HOMEWORK
• Read 382-383. RC on 383. Page 385 q 2
• How does competition cause a shift in the
gene pool?
– Variation within a species causes different
methods of competition
– The individuals with successful adaptations
will survive and reproduce passing the
successful trait to offspring
List in order the scientists who
helped develop the scientific
theory of the origin of life
Origin of Life
•
•
•
•
•
•
•
Primordial Soup
Amino acids and small nucleic acids
Protocell
Anaerobic prokaryote
Aerobic prokaryote
Single celled Eukaryote
Multicelled eukaryotes
How are the mitochondria and
chloroplasts similar to
prokaryotes?
Large organelles
Double membranes
Have DNA
Reproduce as needed
Use oxygen
How did the earth become
biodiverse?
• Evolution is the process by which modern
organisms have descended from ancient
ancestors.
• Evolution is responsible for both the
remarkable similarities we see across all
life and the amazing diversity of that life —
but exactly how does it work?
Three Theories of
Evolution
Lamarck
Darwin
Modern Synthesis
Lamarck’s Theory (Use and
Disuse)
1) 1st major theory of evolution
2) Lamarck believed that:
a) evolution occurs in response to “need”
b) acquired characteristics could be passed
on
ex 1) if you learn a lot, you’ll have smarter
kids
ex 2) if you use an organ it will be larger in
offspring, if you don’t it will shrink
3) Experiments showed that Lamarck was
Use and disuse: Giraffe necks are long
because they use them
• AIM: How did the earth become so biodiverse?
• DO NOW: 1- Regents review book read page
144-top of 145. In your own words, what is
organic evolution?
2- Read pages 151-top 152. List and briefly
describe the three modifications to the theory
of evolution.
Homework:Regents Review book page 370
questions 15 and 16. page 382 question 41
Tuesday 4/14/15
• AIM: What are the major concepts that
helped Darwin develop his Theory of
evolution by natural selection?
• DO NOW: List and explain the
mechanisms for evolution.
• OR: In the process of _________ there
are slow changes over a long period of
time
• In the process of punctuated equilibrium
there are long periods of ____ followed by
short periods of _______
HOMEWORK:Text read 382383. Reading check on page
383
Charles Darwin: 1809-1882
• Proposed a mechanism
for biodiversity
• From 1831 to 1836
Darwin served as
naturalist aboard the
H.M.S. Beagle
• Visited places around
the world
• Studied plants and
animals everywhere he
went
Darwins travels
• Concentrated on
the species found
on the Galapagos
islands
• 620 miles off the
coast of Equador
• Observed the
finch bird
• Wrote a book The
origin of species
The Father of Evolution
• I have called this principle, by which
each slight variation, if useful, is
preserved, by the term Natural
Selection.
—Charles Darwin from "The Origin of
Species“
• November 24, 1859
How did Charles Darwin
develop his Theory?
Darwin’s observations
• Specifically he paid close attention to the finch
birds on each island
• He looked at their beaks
• He determined that each finch had a different
beak shaped specifically for the food which was
available to them
• He also noticed that finches on the Galapagos
resembled finches in similar environments in
other parts of the world
Darwin’s observations
•
•
•
•
Overproduction
Competition
Variation
Survival of the fittest
Darwin’s Theory (Natural Selection)
Overproduction
Struggle for
Existence
Competition
Inherited Variation
Natural Selection
•
•
Survival of the
fittest
Wednesday 4/15/15
• AIM: how did Darwin develop his theory of
evolution by natural selection?
• DO NOW: 1- What is evolution?
• 2- What is overproduction?
• 3- What kind of things do individuals within
a population compete for?
• HOMEWORK: Textbook reread page 380381. Is natural selection the same thing
as evolution? EXPLAIN YOUR ANSWER
Thursday 4/16/15
• AIM: How did Charles Darwin develop his
theory of natural selection?
• DO NOW: Choice 1: List and describe the 4
observations Darwin made in his travels
• Choice 2: 1- Within a population, individuals
display ______ or different characteristics.
• 2- Resources within an environment are limited
causing ______ within the population
• HOMEWORK: DUE TOMORROW Text pages
393-394 questions 1-9
Overproduction
• Species produce many more offspring
than environment can support
• Population size is limited by:
space, food supply, disease, predators,
etc.
Variation
• In any sexual reproducing species, there
are differences within individuals
Competition
• Not only do individuals within a population
compete but different species with similar
needs compete
• Intraspecies competition: within ones own
species
• Interspecies competition: between two
different species
Struggle for Existence
• Overproduction of offspring creates
competition for survival between the
members of the species
Survival of the fittest
• Fitness: refers to physical or behavioral
characteristic that helps survival
• The most fit individuals are those capable
of getting the food, shelter, females etc.
Pair and Share
• Using the flow chart that was started,
explain how Darwin developed his
hypothesis of Natural Selection.
Finches
migrate from
South America
to the
galapagos
islands
What
happene
d on the
islands?
How did
this effect
the
observed
traits?
• AIM: How does nature choose fitness?
• Homework: RRB page 373 question 22. Page
369 questions 13 and 14
DO NOW:the cactus
warbler & wood pecker finch
All live on one island.
Which of these finches is least
likely to compete with the
Other two?
• Overproduction causes competition
– There are too many individuals
– The environment cannot maintain
• Individual variation causes different
methods of survival
– The variation with the greatest chance of
survival is said to be the fittest
– These individuals survive and reproduce
passing the fit trait to their offspring
– Over a period of time this shifts the observed
phenotype in the population (evolution)
– NATURE CHOOSES FITNESS
Inherited Variations
• All populations have variations
that can be passed to offspring
• New variations can arise spontaneously
and may be harmful or beneficial
• Weakness in Darwin’s Theory:
failure to account for the sources of
variation
It is important to note
• If Nature drastically changes, the
definition of fitness may change
– Ex: Himalayan Rabbits
Theory of Evolution by Natural
Selection
• In a varied population, Nature chooses
which traits are best fit for survival.
• As Nature changes, new variants become
fit so over a long period of time there is a
shift in observed characteristics of the
population
• Natural selection is the mechanism for
evolution the shift in observed traits
Natural Selection
(Survival of the Fittest)
• In the “struggle for existence” between
members of a species, the ones with
the best “adaptations” for their particular
environment (the “fittest”) are most likely
to survive and reproduce
• “Adaptations” are inherited
characteristics
which improve the
chances of survival
and / or
reproduction
Darwin was afraid of the
skepticism
• Because of the strong religious beliefs of
his time Darwin did not want to use the
word “evolution”
• He called his observations Descent with
modification
– Current day species descended from ancestral
species
– Natural selection is the mechanism for descent
with modification (changes in observed
characterisitcs in a species over a period of
time)
Click on: Watch Darwin Video
• Darwin | American Museum of Natural
History
Why was Darwin’s Theory of
Natural selection incomplete?
Darwin had no idea how variation
occurred
• Gregor Mendel, Hugo deVries and
Thomus Hunt Morgan were all geneticists
who helped figure out the source of
variation.
• Genetic Recombination: crossing over
during gamete formation
• Genetic Mutation: random changes in
gene
Selecting agents
• Factors that choose fitness
– Ex: temperature, predators, pH, habitat, water
availability
Evolution
• Natural selection
– Nature is the
determining factor
• Artificial selection
– Humans are the
selecting factors
Modern (Synthetic) Theory
3 Components
#1. Darwin’s Theory of Natural Selection
( he was correct, but his explanations
were incomplete)
#2. An Explanation of the Sources of
Inherited Variations
Genetic recombination (meiosis) and
mutation
#3. Population Genetics
Sources of Inherited
Variation
#1 Mutations
a) random changes in genes
b) generally harmful and recessive
c) if most mutations are harmful, how
can
they contribute to
improvements in a
species?
d) natural selection preserves good
mutations while eliminating harmful
ones
#2 Genetic Recombination
a) Homologous chromosomes swap
information during Prophase 1 of meiosis
b) refers to inherited variations resulting
from sexual reproduction
b) sexual reproduction creates variety
through:
meiosis, fertilization & crossing over
Genetic Variety and
Extinction
• The greater the genetic variety within a
species the greater the chance that some
can survive in a changed environment.
• If the environment changes, the definition
of fitness may change
• Ex: Peppered moths in Manchester
England
Peppered Moths
• Before Industrial
Revolution
• After Industrial
Revolution
Mechanisms for evolution
• Punctuated
equilibrium
• Gradualism
• AIM: How is evolution in action in current
day species?
• DO NOW: In your own words explain the
greatest chance of variation within a
species
• In your own words explain how fossils
give us insight to common ancestry.
Microevolution vs
Macroevolution
Micorevolution
• Looks at change in
gene pool of a
population
• Shows a shift in the
observed traits within a
specific population
Macroevoultion
• Looks at the major
changes within the
entire history of life
• Studies the origin of life
or new species
developments
• Mostly seen in the fossil
record
Population Genetics
a) The study of changes in the genetic
characteristics of entire populations
b) used to study the rate of evolution
c) Gene Frequency
the % of one particular gene out of all
the genes for one particular trait in a
population
d) Gene pool
all of the genes for all of the
characteristics in a population
Comparing Gene
Frequencies
Why are these gene
frequencies changing?
“A” increases chances of
survival and is more
likely to be passed on
to offspring
Conditions that Conditions that
alter gene %
stabilize gene%
1. Mutations
2. Natural Selection
(unequal survival
rates)
1. No Mutations or
balanced rates of
mutation
2. Equal survival rates for
all genotypes
3. Non-random mating 3. Random mating (equal
(unequal mating
mating opportunities)
opportunities)
4. Small Population Size 4. Large population size
5. Migration (organisms 5. No migration
enter or leave the
Factors that Affect the Rate
of Evolution
#1 Rate of Environmental Change **
if rate of environmental change increases,
rate of evolution must increase
#2 Time Between Generations
as TBG increases, capacity for rapid
evolution decreases
#3 Method of Reproduction
sexual reproduction increases capacity for
rapid evolution
#4 Competition Within Species
as competition increases, evolution rate
increases
Two Theories About the Rate of
Evolution
1. Gradualism
species evolve slowly and steadily
(traditionalists like Darwin believe in gradualism)
2. Punctuated Equilibrium
species may remain relatively stable for
many
generations and then change
dramatically in a
short period
Both theories may be correct:
some species have evolved gradually while
others may have evolved in abrupt spurts
Which type of evolution rate
is represented in each graph?
1. Coevolution
when the evolution of one species is strongly
influenced by the evolution of another
Example: insects and flowering plants
2. Divergent Evolution
when species or populations evolve in different
directions because of adaptation to different
environments
Example: black bear and polar bear
3. Convergent Evolution
when unrelated species evolve similar
characteristics because they are adapting to similar
environments
Example: polar bear and artic fox
Which
pattern of
evolution is
shown by
each
picture?
• AIM: How is evolution in effect today?
• DO NOW: List at least 2 things that would
cause a shift in the gene frequency.
Artificial Selection
When humans have a strong influence on
the evolution of another species
Humans choose fitness
shift gene frequency and may cause
speciation
Selective breeding
• Humans choose organisms with desired
characteristics and breed them
Ex: #1-Antibiotic Resistance in
Bacteria
1) when penicillin was first used it killed over
99%
of bacteria exposed to it
2) some bacteria contain a gene which makes
them resistant to penicillin
3) resistant bacteria survive use of penicillin
and
pass their resistance on to offspring
4) many bacteria are now resistant to penicillin
and other antibiotics
5) antibiotics have been overused
Ex.#2- Industrial Melanism in
Urban Moths
1. Before
industrialization, most
city moths
were
light in color because
dark moths were
more easily seen by
bird predators
Ex.#3-Resistance to DDT
1. When first used, this insecticide killed
almost all exposed insects
2. A small % of insects were genetically
resistant and survived use of DDT
3. Resistant insects reproduced passing
on their resistance to offspring
4. DDT resistance is now widespread
What has caused an increase
in DDT resistant mosquitoes?
HIV drug resistance
• http://www.biocreations.com/animations/e
nglish_HIV/main.swf
Human Immunodeficiency Virus
• Once it enters the body, it infects White
blood cells
• It uses the white blood cell to make more
viruses
• The new viruses then infect more cells
• Certain medications can prevent the HIV
virus from replicating so it cannot infect
any new cells
Resistance
• HIV is a very sophisticated virus
• It has mutated (changed) and created
variation that are resistant to medicine
• AIM: How do scientists classify species?
• DO NOW: If you were a scientist exploring
unchartered land and you came across 2
new “animals” how would you determine
their relatedness?