Transcript Intro to Evolution

Natural Selection and Genetics
in Evolution
Biology 1
Fall 2009
Standards
• B.1.31 - Describe how natural selection provides the following mechanism
for evolution: Some variation in heritable characteristics exists within every
species, and some of these characteristics give individuals an advantage
over others in surviving and reproducing. Understand that the advantaged
offspring, in turn, are more likely than others to survive and reproduce. Also
understand that the proportion of individuals in the population that have
advantageous characteristics will increase.
• B.2.4 - Explain that after the publication of Origin of Species, biological
evolution was supported by the rediscovery of the genetics experiments of
an Austrian monk, Gregor Mendel, by the identification of genes and how
they are sorted in reproduction, and by the discovery that the genetic code
found in DNA is the same for almost all organisms.
• Scientific Thinking – Mathematical and Logical skills
http://dc.doe.in.gov/Standards/AcademicStandards/PrintLibrary/docs-science/2006-sciencebiologyi.doc
Objectives
• Students will be able to explain who Charles
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Darwin is.
Students will be able to explain what Darwin
proposed about Natural Selection.
Students will be able to explain who Gregor
Mendel is.
Students will be able to explain how genetics
can affect evolution.
Students will demonstrate knowledge of
evolution by natural selection through project
presentations.
What is evolution?
• Cumulative genetic changes occurring in a
population over time
• Darwin proposed that evolution occurred
through natural selection
– Natural selection utilizes genetic
variation
http://www.pbs.org/wgbh/evolution/library/faq/cat01.html#Q01
Survival of the Sneakiest
• Comic by the Understanding Evolution team
• "Survival of the fittest" means that the strong
succeed, and the weak fail, right? Well, often
that's how it's portrayed, but the real story is a
bit trickier. Let's take a closer look at what the
crickets do...
• Click here for the Comic (also on the wiki):
http://evolution.berkeley.edu/evolibrary/article/0
_0_0/sneakermales_01
Darwin & Natural Selection
“Man selects only for his own good; Nature only for that of the
being which she tends.” – Charles Darwin
• Darwin postulated…
– that organisms pass on traits to the next generation
– there was competition between members of same
species for resources
– some organisms were more likely to survive long
enough to reproduce based on certain traits
– over time, new species would develop due to
selection for certain traits
Zimmer, C. (2006). Evolution: The Triumph of an Idea. New York: Harper Perennial.
Candy Dish Selection - Activity
• Natural Selection demonstration
• Need a variety of candies (popular and not) and 30 minutes for activity.
1. Pass a candy dish (with a great variety of treats) around the class several times.
2. When more than half of the candy is gone, discuss variation among individuals of
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animal species. Have the students list characteristics that vary in humans by looking
around the room. Ask the students why variation is important (i.e. differential survival
of individuals).
Hold up the candy bowl and remaining candies so the students can see. Count the
remaining candies and write them on the board. Ask students if they remember what
candies were originally in the bowl. Write the original set of candy on the board.
Ask the students to list the traits of the candy they selected (i.e. chocolate, large
size). These are traits that caused certain candies to be removed.
Make another list of the traits of the candies not selected by the students (bad flavor,
small size). These traits allowed the candies to survive.
“So, the fact that there were different candies with different traits resulted in some
candies being eaten and others surviving. This is what natural selection does with
individuals in a population. Each individual has unique traits; some traits will help an
individual survive and some traits do not.”
Tang, Carol. (2003). Candy Dish Selection. UCMP Lessons.
http://www.ucmp.berkeley.edu/education/lessons/candy_dish.html
How Does Natural Selection Work?
• One mechanism of evolution
• How it works:
– Variation in Traits
• Green vs. Brown Beetles
– Differential Reproduction
• Not all individuals survive to reproduce
• Birds eat green more than brown
– Heredity
• Brown beetles have brown offspring
– Results in more beneficial trait becoming
more common in the population (brown
beetles)
http://evolution.berkeley.edu/evosite/evo101/IIIENaturalSelection.shtml
Finch Beak Size & Feeding Activity
• Students draw a card that determines their starting beak size and what type of bean
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they can eat, as well as how many beans they need to survive.
The students pick a "modification card" from a bag.
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A few of the cards include traits that are not suitable for the current "environment" as well
as adaptations that are suitable, while the majority of the cards are neutral and produce no
change.
• The students must follow the card and keep their card a secret.
• Students “feed” by scavenging for beans across the room, only able to pick up one at
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a time (unless their card says differently). The class "feeds" until there isn't any more
food.
Everyone counts up how many beans they have. If the students did not collect
enough beans their card said they needed to survive, they become offspring for the
surviving “birds” and also inherit those birds’ traits.
Before another round of "eating", students pick out another modification card.
The cycle would continue until the students understand that modifications are
random or until the end of the scheduled time.
The students should also come to the conclusion that mutations can be helpful, not
helpful, or neutral through showing that not only good mutations happen to promote
natural selection.
Flashy Fish Activity
• Professor John Endler traveled to Trinidad in the 1970s to study wild guppies. The
guppies live in small streams that flow down the mountains from pool to pool. In this
activity, you will take part in an online simulation of Endler's work. You will collect
data, formulate a hypothesis, and run a series of experiments. You will find out about
the interplay between natural selection and sexual selection in this wild population of
guppies.
1. Print the Flashy Fish: Data form (pdf) and the Flashy Fish: Discussion Questions
(pdf), or get them from your teacher.
2. Launch the Sex and the Single Guppy Web activity.
A. Select "I'm ready to find out."
B. Read the text, and click on the pools to investigate the guppy stream more closely.
C. Then click on "What causes guppy color variation?" Select one of the hypotheses or create
your own, and record it on the data form.
D. Visit the Guppy Gallery. Read about the different types of guppies, their predators, and their
habitats.
E. Click on "simulation." Proceed with the simulation by creating and carrying out a field
experiment to gather data to test your hypothesis. Record your data on the form. (You may
need to alter your hypothesis if the data does not support it.)
3. Answer the questions on the Data form. Think about the Discussion Questions and be
prepared to discuss your hypothesis, your experiment, and your explanations with
the class.
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http://www.pbs.org/wgbh/evolution/educators/lessons/lesson4/act2.html
Genetics & Natural Selection
• Watch the video about
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Geneticist Pardis Sabeti
The class will discuss the following:
– What did Pardis Sabeti figure out?
– Why do you think it was considered a scientific
breakthrough?
– Why do you think she describes her breakthrough as a
"wonderful scavenger hunt"?
– What is meant by the term "resistant" in the context of
disease-causing organisms?
– What does being able to drink milk have to do with natural
selection?
http://www.teachersdomain.org/resource/nsn08.sci.life.evo.pardis/
Video: http://www.teachersdomain.org/asset/nsn08_vid_pardis/
Gregor Mendel’s Experiment
• Mendel used true
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breeding lines and
crossed with opposite
traits (purple vs. white)
1st generation of
offspring were all purple
(dominant trait)
2nd generation had 25%
white (recessive trait)
http://www.rogers.k12.ar.us/users/ehutches/mendel.phtml
Breeding Bunnies
• In this activity, you will examine natural selection in a small
population of wild rabbits. Evolution, on a genetic level, is a change
in the frequency of alleles in a population over a period of time.
Breeders of rabbits have long been familiar with a variety of genetic
traits that affect the survivability of rabbits in the wild, as well as in
breeding populations. One such trait is the trait for furless rabbits
(naked bunnies). This trait was first discovered in England by W.E.
Castle in 1933. The furless rabbit is rarely found in the wild because
the cold English winters are a definite selective force against it.
• Note: In this lab, the dominant allele for normal fur is represented
by F and the recessive allele for no fur is represented by f. Bunnies
that inherit two F alleles or one F and one f allele have fur, while
bunnies that inherit two fs have no fur.
• Procedure found on the Wiki page under Breeding Bunnies.
• http://www.pbs.org/wgbh/evolution/educators/lessons/lesson4/act1.html
What can Natural Selection and
Genetics tell us about Evolution?
• Gregor Mendel discovered the mechanism for heredity
– Gametes contain one factor (allele) for different traits but not
both factors needed to express the traits.
– Characteristics are inherited independently from other
characteristics (i.e. Eye color and height).
– Each inherited trait is determined by two alleles, one from each
parent which determine whether a gene will be dominant or
recessive.
• Evolution & genetics account for variability in a species
– Crossing over of chromosomes
– Dominant and recessive traits
– Independent assortment
http://www.mnsu.edu/emuseum/biology/evolution/genetics/mendelsvariation.html
Class Presentations
• Make a short PowerPoint presentation on one
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example of evolution by natural selection.
Explain how this evolution occurred.
Use your notes on natural selection to assist in
your explanation.
How could Mendel’s ideas on genetics have
played a part in your example?
Cite your references
Possible Project Topics
• Peppered moths in England during the
Industrial Revolution
• Cichlids in Lake Victoria and the ability to
build sand castles
• Finch Beak sizes in the Galapagos islands
• Sickle Cell in Humans
• Or another of your choice, with teacher
approval
References
• http://anthro.palomar.edu/evolve/evolve_2.htm
• http://anthro.palomar.edu/synthetic/synth_4.htm
• http://dc.doe.in.gov/Standards/AcademicStandards/PrintLibrary/docs-science/2006•
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science-biologyi.doc
http://evolution.berkeley.edu/evolibrary/article/0_0_0/sneakermales_01
http://evolution.berkeley.edu/evosite/evo101/IIIENaturalSelection.shtml
http://www.actionbioscience.org/evolution/futuyma.html
http://www.literature.org/authors/darwin-charles/the-origin-of-species/chapter04.html
http://www.mnsu.edu/emuseum/biology/evolution/genetics/mendelsvariation.html
http://www.pbs.org/wgbh/evolution/educators/lessons/lesson4/act1.html
http://www.pbs.org/wgbh/evolution/educators/lessons/lesson4/act2.html
http://www.pbs.org/wgbh/evolution/library/faq/cat01.html#Q01
http://www.rogers.k12.ar.us/users/ehutches/mendel.phtml
http://www.teachersdomain.org/resource/nsn08.sci.life.evo.pardis/
Tang, Carol. (2003). Candy Dish Selection. UCMP Lessons.
http://www.ucmp.berkeley.edu/education/lessons/candy_dish.html
Zimmer, C. (2006). Evolution: The Triumph of an Idea. New York: Harper Perennial.