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Unit Plan – Biology Unit 1: Sex, variation and natural selection
Lesson
1
2627/8
Topic
Characteristics
of living things
Why is it all
about SEX?
DNA Molecule,
Genes,
chromosomes,
proteins
2
2829/8
DNA
Gametes
3
1-2/9
Discontinuous
variation
Activity
Go over science skills test.
Characteristics of living
things worksheet and
discussion of how these
characteristics all support
passing on of an
individual’s genes.
DNA – About the molecule
worksheet
Build model of DNA
Monohybrid
crosses
Pre-test (10 minutes)
Lab on PTC tasting
Look at crossing of human
monohybrid traits e.g.
Knowledge and Skills - All students should:
-List, identify and describe the characteristics of living organisms including
reproduction, respiration, nutrition, excretion, growth, sensitivity and movement.
-State that DNA is the chemical which stores the coded instructions.
Self-assessment-check
answers to worksheet.
-Explain that genes are ‘coded instructions’ for making proteins.
-List the components of a DNA nucleotide.
-Describe how nucleotides are joined to create a double stranded DNA molecule.
-Explain complementary base pairing and the bonding within a DNA molecule.
-State that the genetic code is read as triplets and is universal.
-Explain that changes in the genetic code can lead to mutations.
-State that some mutations are responsible for heritable variations in populations
Peer in groups
-Design and build a model which accurately depicts the molecular structure of DNA
-Describe the basic structure of chromosomes and where they are found in eukaryotic
cells.
-State the differences in the number of chromosomes in somatic(body) cells and
gametes (sex cells)
-Define the terms haploid and diploid
-Explain the basic principles of meiosis and gamete formation
-State that fertilization restores the diploid number.
Ppt gametes/animation
gametes and meiosis
Monohybrid crosses
4
3-4/9
Assessment
Formative
-Measure and analyse variation in a population
-Draw a histogram which depicts discontinuous variation.
- Define the terms chromosome, DNA, gene, allele, genotype, phenotype,
homozygous, heterozygous, dominant, recessive, and gamete.
-Determine the frequencies of monohybrid traits in the class and compare them to
theoretical values
continued
5
5-8/9
Continuous
variation
tongue rolling, lobes,
thumbs and mid-digit hair
Lab on variation in bean
sprouts and height
Formative quiz on
monohybrid crosses
Formative-histogram
6
9-11/9
7
1215/9
8
1617/9
9
18/199
Natural
Selection
Natural selection
Introduction to natural
selection
Tooth pick exercise
Peppered moth and bacteria
Summative-graph
Formative dataresponse question
-Explain how animals and plants adapt to specific features in their environment
M & M activity
Ref to Darwin’s finches
Review.
End of Unit
test
-Measure and analyze variation within a population.
-Draw a histogram that depicts variation within a population.
-Explain the differences between continuous and discontinuous variation.
-Discuss that continuous variation is a result of both environmental and genetic
influences
-Explain how continuous variation can lead to normal distribution within a
population.
-Describe how variation in organisms leads to differential survival
-State that natural selection leads to evolution of populations
- Describe examples of how natural selection leads to evolution
Summative
Characteristics of Living Things
There are 7 characteristics of living things:
Movement
Respiration
Sensitivity
Growth
Reproduction
Excretion
Nutrition
a) Match the following statements with each of the characteristics.







Producing offspring
Swimming, running, crawling, opening of flowers
Releasing energy from food
Responding to stimuli
Eating and drinking/feeding
Removing poisonous waste
Increasing in size
b) For each of the diagrams below state which characteristic of living things it shows.
3
4
DNA: Structure and Function
The following program will help you to understand how the DNA molecule carries the chemical code
for inheritance. Answer each question as you go by circling the letters or filling in the blanks.
1. Examine Fig. 1 that is a diagram of a short length of a DNA molecule.
The DNA molecule is long and threadlike or string like. It is composed of two strands, or
threads, that loosely twist about each other. The two long strands are connected by short rod like
structures that are composed of bases. Which letter(s) indicate the long twisting strands? ( a b c
d)
Fig. 1
2. Which letter(s) in Fig. 1 indicate the rod like structures that join the long, twisting strands?
_______
3. If the twisted strands of DNA were untwisted, the model would look something like a ladder (as
shown in Fig. 2). In the untwisted molecule, the long strands (sides of the ladder) are indicated by
the letters
( a b c d ), and the connecting rod-like structures (the rungs of the ladder)
are indicated by the letters ( a b c d ).
Fig. 2
Fig. 3
4. Fig. 3 shows a close up view of one strand of the DNA molecule. Sugar molecules and phosphate
molecules alternate in the strand. Do these groups also alternate in the second strand? (yes / no)
5. The sides of the ladder (the long strands) are made of alternating _________ groups and
____________ groups.
5
6. The structure labeled ______ is a strong chemical bond that joins the sugar and phosphate groups.
7. The rungs of the ladder consist of
.
8. These rungs are connected to the
groups on the sides of the ladder.
9. The structure labeled ______ is a strong chemical bond that joins the base to the sugar group.
10. Given your knowledge of the structure of DNA so far, what is wrong with the following figures?
S
P
S
P
S
P
S
P
S
P
S
P
Fig. 4:
S
S
P
P
S
S
P
P
S
S
P
P
S
S
P
P
Fig. 5:
11. The two rod structures that make up the rungs on the ladder are bases. These bases face each other
in this fashion:
Fig. 6
In this example, one of the bases that makes up a rung is labeled ____;the other is labeled _____.
6
12. While all of the rungs are made of two bases, not all of the rungs are alike. Some of the rungs are
made of two other kinds of bases that called G and C, as shown below.
Fig. 7
13. Examine Fig. 8 .This diagram shows a segment of a DNA molecule with six rungs. They are
numbered 1 to 6. Rung 1 contains two bases. What are they? ________. This is called a base
pair.
Fig.
8
14. Rung 2 contains the base pair_________.
15. Rung 4 contains the base pair_________.
16. Rung 5 contains the base pair_________.
17. In Fig. 8, do any of the rungs contain an A – G base pair? (yes/no) _______
18. Do any of the rungs contain a T – C base pair? (yes/no) _______
19. Therefore,
always base pairs with
and
always base pairs with
.
20. The bases don’t physically join together by covalent bonds. Instead, they are attracted to one
another due to their chemical structures. These attractions are called hydrogen bonds and are
very weak compared to the covalent bonds that hold the sugar and phosphate groups together.
These attractions are very specific and only allow A to form hydrogen bonds with T, and G to
form hydrogen bonds with C. Specifically, A will form 2 hydrogen bonds with T, and G will
form three hydrogen bonds with C.
21. How many total hydrogen bonds will there be in a section of DNA that contains 4 A-T base pairs?
7
22. How many total hydrogen bonds will there be in a section of DNA that contains 2 G-C base pairs?
23. How many total hydrogen bonds will there be in the section of DNA in Fig. 8?
24. DNA molecules control inheritance, and we also know that genes control inheritance. Would you
suspect that there might be some relationship between DNA and genes? (yes/no) ______
25. We also know that only the bases A,T,G,C that comprise the rungs of the ladder control the
differences in heredity. When the order of these bases are changed, it (can affect/cannot affect)
______________ the heredity message that the genes transmit.
26. We know that there are thousands of genes in any one organism such as a human being and only
four bases in the DNA molecule. If there are thousands of genes, and only four bases then one base
(could be / could not be) ________________ one gene.
27. One base cannot be one gene. Then how can four bases be thousands of genes? The following
approach is one explanation of this relationship. Imagine that each base is like a letter in our
alphabet. There are 26 letters in the English alphabet, from A to Z. Most words are made of two or
more letters, such as BAD, POT, PEAL, and POOL. However, other words can be made from the
same letters simply by rearranging them. For example:
BAD - DAB
POT-TOP
PEAL-LEAP
POOL-LOOP
28. Thus, while the letters of the alphabet do not change, one word can be changed into another by
____________________ the letters.
29. A single gene is usually made up of hundreds of bases, and therefore the number of different genes
that can be made using these four bases in almost limitless. For example, if genes were only two
bases long (that is, two rungs on the ladder), you could have the following combinations:
30.
A-T, A-G, A-C, A-A, T-A, T-G, T-C, T-T , G-A, G-C, G-T, G-G , C-A, C-G, C-T, or C-C
or a total of
combinations. This can be determined by the equation: combinations
x
= 4 , where 4 is the number of bases there are and x represents the number of bases in the gene.
In the last example, there are 42 (or 4 x 4) = 16 combinations.
31. If genes were 3 bases long, how many different genes could there be? 43 =
32. How many different genes can be represented from the piece of DNA in Fig. 8?
33. A gene of 100 bases is considered to be a small gene. How many combinations of that gene are
there? Get your calculators out!
. Now consider that an average
size gene is 1000 bases long and it is hardly a wonder that there is so much diversity around!
34. The instructions on a DNA strand are read in groups of three bases. To illustrate this, imagine this
group of letters was a DNA strand.
THEREDDOGATETHEFATCAT
Reading in groups of three, the sentence would be:
8
35. As mentioned earlier, bases in the DNA can change, giving rise to new instructions that alter the
heritable traits. Try changing the 19th letter in the sentence above to an R. Now what does the
sentence say?
. Does it still make sense?
36. Sometimes changes in the DNA can lead to a disaster as far as clear instructions go. Try adding
an E after the O in the sentence and read it in groups of three. Does it make any sense?
Build a DNA Model
In your groups, based on your knowledge of DNA you need to design and build a 3-dimensional
model which accurately represents DNA as a molecule. You can use any materials you wish. Basic
materials available in class will be:
Scissors
Glue
Cellotape
Paper
Your model will be assessed by your peers using the following rubric:
Rubric for 3-D DNA MODEL
Names:
Not at all Partially
Completely
Has two strands each with at least 5
nucleotides shown in each
0
1
2
Each strand shows correct arrangement of
sugar, phosphate and base
0
1
2
Is a double helix (Shows at least 1 twist)
0
1
2
Shows correct complimentary base-pairing
0
1
2
Correct number of hydrogen bonds
between base-pairs
0
1
2
Total /10
9
A Variety of Gametes
Gametes (sex cells) are produced as a result of meiosis in organs called gonads. Gametes are haploid
so that when male and female gametes come together in fertilisation the diploid number is restored.
There are a variety of gametes produced by different organisms. Search the internet to complete the
table below:
Name of
organism
Human
Chicken
Goat
Tomato
Rice
Diploid number of
chromosomes in
somatic cells
46
Haploid number of
chromosomes in
gametes
23
Name of male
gamete
Name of
female gamete
sperm
ovum
Discontinuous Variation
Characteristics showing discontinuous variation fall into a few very distinct (no overlap) classes.
These variations result from genetic factors, usually one or two genes. Environmental factors
generally do not play any part in this type of variation.
The ability to taste an organic chemical PTC (phenylthiocarbamide) is determined be a single gene
with two alleles; non-tasters (t-recessive) and tasters (T-dominant). About 70% of the general
population has the ability to taste PTC.
You will be given a piece of filter paper which has PTC soaked into it. Place it in your mouth and
write down if you taste anything or not on the piece of scrap paper.
 Record the number of people in the class who can/cannot taste PTC.
 Draw a histogram of the results on graph paper.
 What kind of variation does this show?
10
Some definitions you will find helpful in genetics
Allele
One specific form of a gene, differing from other alleles by
one or a few bases only and occupying the same gene
locus/position as other alleles of the gene.
Gene
A heritable (that can be inherited - from parents) factor that
controls a specific characteristic, consisting of a length of
DNA occupying a position on a chromosome known as a
locus.
Genotype
The alleles (versions of genes) possessed by an organism.
Phenotype
All the characteristics of an organism determined by the
genotype and the environment.
Dominant
allele
An allele which has the same effect on the phenotype (you)
whether it is present in the homozygous or heterozygous
state(presents in you if you get dominant allele from either
mom or dad).
Recessive
allele
An allele which only has an effect on the phenotype when
present in the homozygous state (recessive from mom and
recessive from dad).
Homozygous Having two identical alleles of a gene.
Heterozygous Having two different alleles of a gene.
Haploid (n)
The chromosome set having only one member of each
chromosome pair
Diploid (2n)
Individual or cell having two copies of each chromosome pair,
one from the mother and the other from the father.
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Monohybrid Crosses.
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Monohybrid Crosses – Problems
Please answer your questions on a separate piece of paper.
1. In dogs, wire hair (H) is dominant over smooth (h). In a cross of a homozygous
wire-haired dog with a smooth-haired dog, what will be the phenotype of the
puppies?
2. In guinea pigs, black coat color is dominant over white. If a heterozygous blackcoated guinea pig is mated with a white coated guinea pig, how many different
phenotypes with respect to coat color could be expected in the offspring?
3. In Pea plants the alleles for tall plants (T) is dominant over the alleles for short
plants (t). When two pea plants are crossed, 92 tall plants and 31 short plants are
produced. The genotypes of the parent plants are?
4. The ability to curl your tongue up on the sides (R, tongue rolling) is dominant to not
being able to roll your tongue. A woman who can roll her tongue marries a man who
cannot. Their first child has his father's phenotype. What are the genotypes of the
mother, father, and child?
5. Saguaro cacti are very tall cylindrical plants that usually have two L-shaped arms,
one on each side. Suppose you lived in southern Arizona in the United States where
the Saguaro cactus is common and you happen to have one growing in your yard.
Your Saguaro has two arms but one is longer than the other. Now, assume that arm
length in these cacti is controlled by a single gene with arms of the same length (A)
being dominant to arms of different lengths.
a. What is the genotype of your cactus?
b. Is it possible that the parents of your cactus could both have arms of the same
length? If so, what are their genotypes?
c. Suppose you cross your cactus with that of your neighbor which has arms of the
same length. Your great grandchildren (it takes a Saguaro cactus a long time to
mature) find that half of the resulting offspring have arms the same length and
half have arms of different lengths. Use a Punnett square to demonstrate the
genotype of your neighbor's cactus.
14
Genetic Traits Inventory
(from http://gslc.genetics.utah.edu and http://www.woodrow.org)
Traits are observable characteristics. While each of us shares some of our traits with many other
people, the combination of all our individual traits is what makes us unique.
All the traits in your body are determined by bits of DNA called genes. Hundreds of genes together
form chromosomes, which are found in the nucleus of cells. Cells have 2 copies of each gene because
both mother and father give one copy at fertilization.
Most genes have two or more variations. For example, the gene for your earlobe shape has two
versions called alleles – attached or free hanging (see diagram below). These versions, as in many
genes, have a dominant and a recessive alleles. In this example, the free earlobe is dominant to
attached.



If an individual has 2 versions for free hanging lobes (dominant), then their earlobes will be
free.
If an individual has 2 versions for attached lobes (recessive), then their earlobes will be
attached.
But if they have one of each, then they will have free hanging earlobes because it is the
dominant version.
In this investigation you will examine some of the traits you have and compare them with the other
students in the class.
Ear lobe attachment: (See Fig. 1) The ear lobes may either hang free or be attached directly to the
side of the head. The allele for the free or unattached ear lobe trait is dominant (F), while attached
earlobes are caused by having two recessive alleles (ff).
Tongue rolling: (See Fig. 2) Some people have the ability to roll their tongue into a distinct U-shape
when they extend their tongue from their mouth. This ability to roll the tongue is due to a dominant
allele (R). Those who have the two recessive alleles (rr) can only curve their tongue slightly.
Hitchhiker's thumb: (See Fig. 3) People with two recessive alleles (tt) for hitchhiker's thumb can
bend the distal joint of their thumb back so that it forms an angle of almost 45 degrees. This would be
hyperextension of the thumb. People with a dominant allele (T) cannot do this.
Mid-digital hair: (See Fig. 4) The mid-digital hair trait is determined by a dominant allele (D) for
each finger causing hair to grow on the top of that finger. The trait is carried by a set of five alleles and
will cause hair to grow on one finger, two fingers, etc., depending on what allele you inherit. People
who have no hair on the digital part of their fingers carry all recessive alleles (dd).
Gender: Females have two X chromosomes, while males have an X and a Y chromosome. Maleness
is determined by a special region of the Y chromosome. Femaleness results from the lack of this
region.
Handedness: While this may be more complicated than one gene, some scientists thought that righthanded was dominant to left-handed.
Hairline shape (see Fig 5). The shape of the hairline can be a widow’s peak (dominant) or a straight
line (recessive).
Hand clasping: Without thinking about it too much, clasp your hands together. People with a
dominant allele affecting this will have their left thumb on top, while those with both recessive alleles
will have the right thumb on top.
15
Fig 5
1) Complete the following table using the data from the class.
Trait
Yes
No
% Frequency of dominant
trait
Free ear lobes?
Tongue rolling?
Hitchhiker’s thumb?
Mid-digital hair?
Female?
Right-handed?
Widow’s peak?
Left thumb on top?
2) Find the frequency of each trait and enter it into the last column. The frequency of each trait can be
determined using the following formula:
Number of students with the trait X 100 = % frequency.
Number of students in the class
3) Compare the frequency in the class of each gene with the frequency of the traits in the general
population in the table below and calculate % difference with class data. What kind of variation is
shown by each of these traits?
Trait
Free earlobes
Tongue Rolling
Hitchhiker’s
thumb
Mid-digital Hair
Gender
Handedness
Hairline
Hand clasping
Frequencies
Free – 60%; Attached – 40%
Rollers – 70%; Non-rollers – 30%
Straight thumb – 75%; Hitchhiker’s – 25%
With hair – 80%; No hair – 20%
Males – 50%; Females – 50%
Right handed – 93%; Left handed – 7%
Widow’s peak – 90%; No widow’s peak – 10%
Left thumb on top – 55%; Right thumb on top – 44%
16
Variation Lab
Introduction:
Variation is common in all species and is caused by meiosis, mutation and sexual reproduction. Some
variations seem to have no apparent survival advantage or disadvantage, or others may eventually
prove to be advantageous and allow the individual to withstand some environmental change.
When studying variations of a characteristic, a biologist measures each variation and examines the
frequency and the degree to which the variation occurs within a population. In this investigation, you
will determine the mode, which the most commonly occurring measurement found among the
variations in the population being studied. You will then graph your findings by drawing a frequency
distribution curve, a graph that illustrates the range of variations for the trait and shows the number of
individuals that exhibit each variation.
Part A – Bean Sprout Height
1. Collect 20 mung bean sprouts. They have been grown under identical conditions in a dark
moist area for several days.
2. Measure to the nearest millimeter the shoot of each bean from the root tip to the shoot tip.
Record your measurement in the table below. Add uncertainties. Obtain 20 more
measurements from another group.
Sprout Length
(mm)
1
2
3
4
5
6
7
8
9
10
Sprout
Length
(mm)
Sprout
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Length
(mm)
Sprout
Length
(mm)
31
32
33
34
35
36
37
38
39
40
Group the lengths of the sprouts into 5 mm (or other suitable) ranges or bins (46-50 mm, 51-55 mm,
56-60 mm, etc). Construct a frequency table in the space below:
17
Graph your results on graph paper to show a frequency distribution curve (histogram).
Put number of sprouts (frequency) falling in each range or bin on the Y Axis and the ranges (bins) of
the length of sprouts on the X-axis.
Questions:
1. What is the length of the shortest bean sprout?
2. What is the length of the longest bean sprout?
3. What is the range of your measurements?
4. What is the mode (the most common range/bin measurement) for length among your bean
sprouts?
5. In mm what is the difference between the lowest measurement and the mode?
6. What is the difference between the highest measurement and the mode?
7. Which measurement tells you the most about a population with regard to a particular trait; the
lowest measurement, the highest measurement or the mode?
Conclusion and Questions:
1. What shape does a distribution curve generally take?
2. What advantages and disadvantages do you think the longest bean sprouts have for survival?
3. What kind of variation does bean sprout length show? Explain.
4. Identify some factors not related to genetics that might have affected the length of each bean
sprout.
Extension Activity
Height of 9th Graders-see moodle
18
The Peppered Moth: An Evolutionary Example of Adaptation and Survival
One of the most studied examples of adaptation is the dark- and light-colored peppered moth of England. The
peppered moth, Biston betularia, occurs in two color forms: (1) gray with dark flecks, and (2) solid black. Like
most moths, peppered moths are active at night, and rest during the day. Although all their hiding places are not
well known, peppered moths may rest on tree trunks and in the overlying canopy.
In pre-industrial England, most of the peppered moths were speckled gray, much like the trees on which the
peppered moths rested during the day. The black moths were fewer in number. However, with the Industrial
Revolution came factories, which produced huge volumes of polluting, black soot produced by the burning of
coal. In a short time, the black-colored moths dominated the population, and speckled gray moths were fewer
in number.
(A) Pre-Industrial Revolution
(B) During Industrial Revolution
19
Being eaten by a bird is the primary threat to a peppered moth. In industrial areas, the black moths appear to
have avoided being eaten. They survived better, and reproduced more, or had what biologists call a higher
“fitness”. Since more of the black parents lived to reproduce, their population numbers increased. After many
moth generations, almost all of the moths in industrial areas were black. Black coloration is considered to be,
therefore, an adaptation to an environment with black tree trunks. They evolved through natural selection
because black individuals have a higher fitness in areas where the tree trunks are black than do the gray moths.
It is important to note that it is not the individuals who adapted. Peppered moths are black or gray because of
their genetics. It is the result of a population’s fitness within a certain environment that gives them an “edge”
over another population.
With this information in mind, conduct the lab activity. You will see for yourself exactly what happened to the
peppered moth populations, as England became an industrialized nation.
WANT TO KNOW MORE???? Follow these links for more about the peppered moth:
(1) www.utm.edu/~rirwin/moth.htm
(2) www.gen.umn.edu/faculty_staff/hatch/1131/Evolution/peppered_moth.html
(3) http://biocrs.biomed.brown.edu/Elephant%20stuff/Chapters/Ch%2014/Moths/Moth-Update.html
(this last one is complex, but presents some interesting and updates concerning peppered moth research)
20
ACTIVITY: THE PEPPERED MOTH:
How Adaptations Aid Survival and Affect Population Size
The table below represents data from a ten-year study of two varieties of the same species of peppered moth.
The number represents moths captured in traps for ten consecutive years. The traps were located in the same
area each year.
Year
1
2
3
4
5
6
7
8
9
10
Numbers of light
Moths Captured
556
537
484
392
246
225
193
147
84
56
Numbers of dark moths
Captured
64
112
198
210
281
357
412
503
594
638
Using this data provided construct a graph (think of the most suitable way) comparing the numbers of
each variety of peppered moths.
QUESTIONS AND SUMMARY:
1. What preys on the peppered moths?
2. If the bark of the trees is dark and the moths that rest there are light what will happen to the
moths?
3. What could have caused the first moths to change from a light variety to a dark variety?
4. What event caused the tree trunks of many trees in England to turn from light to dark?
5. Which variety of moth increased of the ten-year period?
6. Using the data on the graph, draw a conclusion concerning the population of peppered moths in
the sampled area of England.
7. Explain the reason for the increase in the number of dark colored moths.
8. What means could be used to return the environment of the peppered moth to its original state?
9. What effect would cleaning up the environment have on the moths?
10. What kind of variation is shown by the peppered moths?
21
Darwin’s Finches
Charles Darwin visited the Galapogos Islands in 1835 and gathered data on finches that were living
there. When he returned to London, he looked carefully at his data and came to the conclusion that all
the birds were closely related and it led him to develop his theory of natural selection. A few million
years ago a species of finch migrated to the Galapogos Islands from mainland South or central
America. From this one species came 13-14 other species to exploit particular niches within the
islands through a process known as adaptive radiation. Adaptive radiation occurs when the niche
exerts selection pressures that push populations in particular directions. In this case the finches have
become adapted to eating seeds, insects, flowers, sucking the blood of sea birds and leaves. It is
thought that changes in climate caused a change in the type of food that was available, hence the beak
structure that was best adapted to a particular type of food survived and reproduced while the
remainder died.
[source, accessed June 2008: http://nhsadvancedbiology.blogspot.com/2008/02/darwins-finches-activity.html]
Questions.
Choose two of the species of finch and describe how their beaks are best adapted to the food that they
eat.
22
Activity: Survival of the best beak!
This simulation exercise is designed to demonstrate how the best adapted beak for a particular food
type allows that species to survive and reproduce.
In groups of 10 you are provided a tray of M & M’s and the following “beaks”:
Chop sticks; fork; spoon, forceps, knife, toothpick.
1) Each group member is allocated a type of beak.
2) You are then given 30s to collect as many M & M’s as you can using ONLY your “beak”. Do not
interfere with anyone else.
3) For each beak type record the number M & M’s collected.
4) If you collected 15 you survive and can reproduce; if you did not you die (you then become an
offspring of a surviving beak type)
5) Return the M & M’s to the bowl
6) Repeat steps 2) to 4) three more times.
There has been a change in the climate and the type of food available now is popcorn. Repeat 1) to 6)
above.
Processing your data
a) Graph the number of M & M’s collected against the beak type after the first “feeding”.
b) Graph the number of pieces of popcorn collected against the beak type after the first “feeding”.
c) Graph (on the same set of axes) the number of each type of beak surviving after the third generation
and after the 4th generation.
Questions
i) Which “beak” was best adapted for M & M’s? Explain.
ii) Which “beak” was best adapted for the popcorn? Explain.
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Natural Selection: The Key ideas
Use the list of words below to complete the paragraph.
struggle for survival
least adapted
mutation
change
best suited
sexual reproduction
natural selection
evolve
reproduce
inherited
extinct
competition
meiosis
survival of the fittest
offspring
genes
………………………………………and ……………………(3 things) result in variation in offspring.
Organisms tend to produce more……………… than the environment can support. This leads to
a………………………………..or …………….. Those organisms which
…………………characteristics that are …………………….. to the environment survive and
can………………. And pass on their advantageous ……….. ; those that are …………………….. die
off and may become………………….. This is sometimes referred to as……………………….. The
process of some organisms surviving whilst others die off is known as……………………. Species
can…………….., where the characteristics of a population ……………………to suit the environment
over a long period of time through natural selection. This often occurs in response to environmental
change.
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