Transcript Mechanisms of Evolution: Natural Selection

1.
Grab the picture of your favorite candy
2.
And the Charles Darwin Article
◦ Read the Article and summarize each
paragraph off the side
◦ When you are finished answer the questions
on the back
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Be prepared to share your answers
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At your table
In groups of 3
Discuss your answers and accumulate them
into one on a white board.
Make sure to add other students notes to
your own
CSCOPE
Unit:09
Lesson: 01
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Students = Predators
Candy = different populations of organisms
On your white boards describe the traits
(characteristics) your candy has
Differential Reproductive Success
1.
2.
3.
4.
5.
6.
What is variation?
What is genetic variation?
Which candy “population” was most
“fit” for it’s environment?
What do you think will eventually
happen to the skittle population is the
trend continues?
How do I know the more fit “species”
passed on their genes?
Did individual species change? Why or
why not?
In your spirals write this
Variation occurs in all populations and because
of this, some individuals will be more fit to
reproduce than others.
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Answer the following Question.
How does genetic variation lead to
(Differential) reproductive success?
Genetic variation means each individual has unique
traits; some traits will help an individual survive and
reproduce, and some traits do not.
Differential
Reproductive
Success
A
E
D
Reproductive
Success
Natural Selection
B
F
C
Limited
Resources
Fitness
Genetic
Variation
Reproductive
Success
Natural Selection
Organisms
produce more
offspring than
can survive.
Competition
Environmental
Factors
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Natural Selection Lab Sheet
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Do not throw the beads.
THIS IS A LAB.
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ALL LAB BEHAVIOR is required by law.
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Candy = different populations
Students = predators
Answer the Lab Analysis Questions
1.
2.
3.
4.
5.
Was genetic variation was present in the
population? If so, how?
What did this variation lead to in the
population?
How do you know the successful traits are
passed on?
Did my individual species change? Explain.
What changed overtime and how did it
change?
1.
2.
3.
4.
5.
Evolution Foldable Chart
Formula for Natural Selection
Types of Natural Selection
Chart
Glue
Scissors
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Set up the Mechanisms of Evolution Foldable
Complete Formula for Natural Selection
Complete Natural Selection Chart with Graphs
If we have time
Grade Natural Selection Lab and Graphs
Steps:
1. Remove the excess paper from the top and
bottom by cutting along the dotted lines shown
below in red.
2. Fold along the center line shown in red below.
3. Cut along the dotted lines between each box.
Stop cutting where the dotted lines end.
4. Fold along the red dotted lines shown below so
that each box folds open.
5. Glue the section highlighted in yellow below in
your spiral (right side) so that only the tabs will
fold
open.
LEAVE ROOM IN
YOUR SPIRAL
FOR DEFINITIONS!
We are going to study mechanisms that aid in evolution.
Evolution – a change in the more successful inherited
traits within a population over generations
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A species is an organism(s) that can
produce fertile offspring
A population is a group of
2 or more of the SAME organism
Natural
Selection
Mutations
Recombination
Gene Flow
Genetic Drift
Artificial
Selection
Non-Random
Mating
Reproductive
Isolation
1.
2.
3.
4.
ON PAGE 1 Cut out the
graphic organizer
Fold along the middle
line then
Cut the tabs on the
dotted lines.
ON PAGE 2 Cut out the
images, definitions,
and terms that will be
glued onto the
graphic organizer.
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Work with a partner to determine where the
1. terms,
2. definitions, and
3. images
Fit on the graphic organizer.
The images & definitions will go under the
tabs
The terms go in the “formula” on the front.
“Natural Selection” has already been correctly
placed in the “formula”.
 What
is the purpose of using the “formula”
model to help explain natural selection?
The purpose of the formula is to show that Natural Selection
cannot occur without one step causing the next step which
leads to natural selection and causes Evolution.
 What
three things are needed for the process
of natural selection?
For Natural selection to occur Variations + Reproductive Success +
heredity (inheritance) are needed.
 What
sort of things cause variation in a
population?
Reproduction, Meiosis (genetic recombination), & mutations
can cause variations within a population.
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Title notes
Types of Natural Selection and Adaptations
 In
your Spirals write these 2 statements
about Natural Selection and Adaptations
1.
2.
An adaptation is – characteristic common
in a population because it provides an
improved function.
Adaptations are the result of natural
selection. The most successful traits are
passed on to future generations.
Type
Directional
Selection
Disruptive
Selection
Stabilizing
Selection
Definition
Result
Phenotypic Range
According to the graph what is the most common phenotype?
Light?
Medium?
Dark?
Type
Directional
Selection
Disruptive
Selection
Stabilizing
Selection
Definition
Result
Type
Directional
Selection
Disruptive
Selection
Stabilizing
Selection
Definition
A process of natural selection in
which a single phenotype at one
extreme of the phenotypic range is
favored
Result
The population's trait
distribution shifts
toward an extreme.
Type
Definition
Result
Directional
Selection
A process of natural selection in
which a single phenotype at one
extreme of the phenotypic range is
favored
The population's trait
distribution shifts
toward an extreme.
Disruptive
Selection
A process of natural selection that
favors individuals at both extremes
of a phenotypic range
Can cause such
differences among a
species that the
variation leads to new
species (SPECIATION)
Stabilizing
Selection
Type
Definition
Result
Directional
Selection
A process of natural selection in
which a single phenotype at one
extreme of the phenotypic range is
favored
The population's trait
distribution shifts
toward an extreme.
Disruptive
Selection
A process of natural selection that
favors individuals at both extremes
of a phenotypic range
Can cause such
differences among a
species that the
variation leads to new
species (SPECIATION)
Stabilizing
Selection
A process of natural selection that
tends to favor genotypic
combinations that produce an
intermediate phenotype
It reduces phenotypic
variation. Natural
selection tends to
remove the more severe
phenotypes. (minimal or
no change)
In groups of 3
Decide which graph is
1. Disruptive
2. Directional
3. Stabilizing
Natural Selection
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Look back at your graphic organizer. We will be
exploring the following processes and their influence
on population change (evolution):
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Natural Selection
Mutations
Gene flow
Genetic drift
Artificial selection
Non-random mating
We’ll explore recombination and reproductive
isolation later.
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The circles on your boards help distinguish the original
population makeup from what it might look like after
the change and its makeup many, many generations
later.
The dots represent individual organisms within the
population.
Original Population
Instead of thinking about the dots as representing a
single individual, think about them representing a
percentages of individuals.
 For example, in the population shown below, about
half of the individuals are red, a quarter are blue, and a
quarter are green. That means that if 1,000 individuals
made up that population, about 500 would be red,
about 250 blue, and 250 green.
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Original Population
Original Population
After Chemical Spill
Many Generations
Later
Original Population
After Mutation
Many Generations
Later
 Real-World
Examples:
http://evolution.berkeley.edu/evosite/evo10
1/IIIC2aCasestudy.shtml
Neighboring
Population
Original Population
After Migration
Many Generations
Later
 Real-World
Examples:
http://evolution.berkeley.edu/evosite/evo101/IIIC4a
Geneflowdetails.shtml
Original Population
After Lightning
Many Generations
Later
 Real-World
Examples:
http://www.bio.georgiasouthern.edu/biohome/harvey/lect/lectures.html?flnm=nsln&ttl=Popu
lation%20change%20and%20natural%20selection&cco
de=el&mda=scrn
http://highered.mcgrawhill.com/sites/dl/free/0072835125/126997/animati
on45.html
Original Population
Many Generations
Later
 Real-World
Examples:
http://learn.genetics.utah.edu/content/variat
ion/artificial/
Original Population
Blue = BB or Bb
Red = bb
x
Many Generations
Later
 Real-World
Examples:
http://www.bio.georgiasouthern.edu/biohome/harvey/lect/lectures.html?flnm=nsln&tt
l=Population%20change%20and%20natural%2
0selection&ccode=el&mda=scrn
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The models make it seem that these processes happen
separately and exclusively from each other. The fact is that
numerous mechanisms are simultaneously changing and
molding the genetic makeup of a population.
Population numbers in a real ecosystem are much larger than
what we can represent with dots on our desk.
The genetic makeup and allele frequencies in a population are
much more complicated than blue, green, and red colors.
These models are to help you understand the basic
definitions and processes of evolution, but remember, genetic
change on a population scale is MUCH, MUCH, MUCH more
complex than these models can show.
As we learned in the genetics unit, recombination
leads to genetic material being shuffled.
 This shuffling, along with sexual reproduction,
leads to variation within populations. This variation
leads to selection, which ultimately leads to
evolution.
◦ http://evolution.berkeley.edu/evolibrary/article/e
vo_22
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A
new species may form when one population of
a species becomes reproductively isolated from
another population of the same species.
 Over
time, evolutionary mechanisms occur that
alter the gene pool of the isolated population so
that it is no longer reproductively compatible
with the original population.
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A group of individuals that actually or potentially
interbreed in nature. A species is the biggest gene
pool possible under natural conditions.
Scientists group organisms according to their
similarities.
The most similar organisms belong to a species.
Members of the same species can mate and produce
fertile offspring.
Ex: Humans belong to the species Homo sapiens.
 Speciation
is a lineage-splitting event that
produces two or more separate species.
 Since
being a member of one species is
defined by the ability to successfully
reproduce, speciation (the formation of a
different species) must involve an inability to
successfully reproduce.
Two way reproductive isolation occur:
Prezygotic mechanisms
Postzygotic mechanisms
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Temporal Isolation: Species reproduce in different
seasons or at different times of the day.
Geographical Isolation: Physical barriers (e.g., rivers,
oceans, mountains) prevent the mixing of
populations.
Behavioral Isolation: Species differ in their mating
rituals (e.g., differing bird songs, mating colors,
dances, pheromones).
Mechanical Isolation: Body structure prevents mating.
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Hybrid inviability: Embryological Arrest: Hybrid
embryos often do not develop properly; no viable
offspring is created.
Hybrid Sterility: Infertility: Hybrid offspring might
grow to viable adults, but these are infertile and
cannot produce further offspring
 This shuffling, along with sexual reproduction,
leads to variation within populations. This variation
leads to selection, which ultimately leads to
evolution.
◦ (Donkey + Horse = Mule; Mule is sterile.)
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 Cladogenesis
is the splitting of one
species into two.
 How
does this happen?
o Geographical (physical) isolation, which leads
to reproductive isolation. This is also known
as allopatric speciation.
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There are two scientific theories regarding how
evolution occurs.
◦ Punctuated Equilibrium: This theory proposes that
throughout geological time, biological species go
through long periods of little change and then have
brief periods of rapid change.
◦ Gradualism: This theory proposes that throughout
geological time, biological species gradually
undergo changes that leads to speciation.
Mechanisms of Evolution
Evolution - _____________
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