Download Review packet for Biology Keystone Exam

NAME:______________________________ DATE:__________ PERIOD: _____
GENETICS VOCABULARY
Studying Genetics (the study of DNA and heredity which is the transmission of traits from one
generation to another) is valuable because we can predict and understand the likelihood of inheriting
particular traits. This helps plant and animal breeders in developing varieties that have more desirable
qualities (artificial selection) and Genetics can also help people explain and predict patterns of
inheritance in family lines.
Definitions – Genetics:
1. Genotype: is the actual code that alleles or genes possess (E.g. Tt or TT or tt). The gene may
2.
3.
4.
5.
6.
7.
or may not be expressed when you observe a living organism.
Phenotype: the observable or detectable characteristics of an individual organism--the
observable expression of a genotype.
Allele: is an alternate form of a gene for one trait. For example, brown and blue eyes are two
different alleles for eye color. We have 2 alleles for any, one trait, one from our mother and one
from our father. They may be the same form of the gene (homozygous) or two different forms
(heterozygous).
Genes: are the smallest chemical parts that form segments of chromosomes. Genes determine
what we look like.
Homozygous: a genotype consisting of two identical alleles of a gene for a particular trait. An
individual may be homozygous dominant (AA) or homozygous recessive (aa). Individuals who are
homozygous for a trait are also referred to as homozygotes.
Heterozygous: a genotype consisting of two different alleles of a gene for a particular trait.
An individual that is heterozygous (Aa) is also referred to as hybrids.
Dominant: observed trait of an organism that mask the recessive allele of a trait
8. Recessive: trait of an organism that can be masked by the dominant form of a trait
9. Punnett Square: a simple graphical method of showing all of the potential combinations of
offspring genotypes that can occur and their probability given the parent genotypes. Developed
by Reginald Punnett in the early 1900’s while working with William Bateson. Both were
instrumental in reintroducing Gregor Mendel’s work. Mendel is considered the Father of
Genetics, was a Catholic priest in the Augustinian order, and published his theories in 1865.
10. Probability: the likelihood that a specific event will occur. Probability is usually expressed as
the ratio of the number of actual occurrences to the number of possible occurrences.
Genetics primer
You have two copies of every gene. One of them came from your mom and one came from your dad.
(They each also had two copies of each gene, but randomly gave one of each to you during your
conception.)
Using the example of brown eyes, if both copies of your brown eye gene say "Make brown eyes," then
your eyes will be brown. On the other hand, if both copies say "Don't make brown eyes," then your eyes
will be some other color (which other color depends on other genes).
What happens if one copy says "Make brown eyes" and the other copy says "Don't make brown eyes"?
You might think that you'd end up with something in between. But that's actually not what happens.
What you end up with is just simply brown eyes. In fact, they will be just as brown as someone who has
BOTH copies saying "Make brown eyes."
Biologists say that brown eyes are "dominant." You can think of it like this. The copy that says "Make
brown eyes" is a really big, powerful gene. Whenever it gets into a cell, it overshadows anything else
that's there and makes sure it gets expressed. On the other hand, the copy that says "Don't make
brown eyes" is a little, quiet gene that allows the "Make brown eyes" gene to be expressed. The only
time it gets heard at all is if there are two copies of it and no one else around to overshadow it.
As a convention, the two copies of a gene are written using letters. Capital letters stand for dominant
genes, so the "Make brown eyes" copy would be written B, and lower case letters stand for "recessive"
(not dominant) genes, so the "Don't make brown eyes" copy would be written b.
Since you have two copies, you get two letters. So an individual who got a B from mom and a B from dad
would be written BB (homozygous dominant), someone who got a b from both parents would be written
bb (homozygous recessive), and someone who got a B from one parent and a b from the other would be
written Bb (heterozygous). Notice that BB and Bb individuals BOTH look exactly the same (they both
have brown eyes), but their genes are different so their children might look different. Also, keep in
mind that the only individuals who do not have brown eyes are bb individuals.
Matching
1. _____ Genotype
a. the segment of DNA that determines a particular trait
2. _____ Phenotype
b. the form of the gene that shows up only when inherited
3. _____ Allele
from both parents
4. _____ Heterozygous
c. Two identical genes for the same trait
5. _____ Homozygous
d. an inherited trait which is present even when inherited
6. _____ Dominant
only from one parent.
7. _____ Recessive
e. one of the hereditary material for a particular trait
8. _____ Punnett Square
f. two different genes for the same trait
9. _____ Probability
g. a tool used to analyze possible breeding outcomes
10: ____ Gene
h. the likelihood of an occurrence
i. the kinds of genes an individual carries
j. the observable expression of a trait
Sentence completion
Complete the sentences using the following words: gene, trait, heredity, dominant, and recessive.
1. The segment of DNA that determines the inheritance of a particular trait is called a
_________.
2. The passing of traits from parents to offspring is called _________________.
3. An inherited characteristic of an organism is called a ___________________.
4. The _________________ gene shows up even when inherited only from one parent.
5. The _________________ gene shows up only when inherited from both parents.
Name _______________________________________________ Date ________________ Class______________
Chapter 6 Test, continued
INTERPRETING GRAPHICS
Examine the diagram below and answer the questions that follow.
Male parent
Female parent
White-fur
alleles (bb)
White-fur
allele
Black-fur
alleles (BB)
White-fur allele
Black-fur allele
Offspring
15. When the cells in the male and female parent divide as illustrated, do they form
body cells or sex cells? Explain.
16. Does the first-generation offspring have the mother’s phenotype or the father’s
phenotype?
24
HOLT SCIENCE AND TECHNOLOGY
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Black-fur
allele
45-48 CM 825477-5 2/4/98 5:56 PM Page 47
(Black plate)
12
Section 12.2 Meiosis
Study the Diagram
Prophase I
Metaphase I
Anaphase I
Telophase I
Meiosis II
Meiosis I
Interphase
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Prophase II
Metaphase II
Anaphase II
Telophase II
Use the diagram to answer the questions.
1. Meiosis I begins with one cell. By the end of Meiosis II how many cells are formed?
__________________________________________________________________________________
2. Name a physical process that occurs more than once during meiosis. Answers will vary. _______
__________________________________________________________________________________
__________________________________________________________________________________
3. Cell division by meiosis is a way to produce gametes that have only half the number of
chromosomes of the parent cell. Why is this important? _________________________________
__________________________________________________________________________________
__________________________________________________________________________________
BIOLOGY: The Dynamics of Life CHAPTER 12
47
Name:_____________________________________ Date:_______________ Period:__________
Flower Structure and Reproduction
Flowers are the plant's reproductive structures. Angiosperms are types of plants that bear fruits and flowers.
Flowers are usually both male and female, and are brightly colored to attract insects to help them carry pollen
used for sexual reproduction. Not all flowers are colorful, though. These flowers usually use the wind for
pollination. Most flowers have certain structures in common that perform similar functions.
Parts of the Flower
The receptacle is the part of the branch on which a flower forms. Color the receptacle (B) brown. Sepals are leaf
like structures that surround and protect the flower before it blooms. Color the sepals (C) green. Petals are the
colorful part of the flower that attracts insects and even other small animals, such as mice, birds, and bats. Color
the petals (D) a bright color of your choice. All flowering plants have flowers, but some are not brightly colored.
The petals of these flowers are reduced or absent and the plant relies on the wind or water for pollination.
The flower has both male and female reproductive parts. The female reproductive structures are called carpels.
In most flowers, the carpels are fused together to form a pistil. Color the pistil (P) pink. The pistil has three parts,
which can be seen, in the box labeled "pistil". The stigma at the top is often sticky and is where the pollen
attaches. Color the stigma (J) purple. The style is the long tube that attaches the stigma to the ovary. Sperm
from the pollen will create a pollen tube that will travel down the style to the ovules in the ovary. The ovules, or
eggs, are stored in the ovary until they are fertilized. Plants can only fertilize eggs of the same species. Special
chemicals prevent sperm from fertilizing the eggs of flowers that are not the same kind. Color the style (K) red,
and the ovary (L) pink. Color the ovules (O) black.
The male reproductive structures are called the stamens. Color the stamens (H) blue. Each stamen consists of
an anther (A), which produces pollen, and a filament (F), which supports the anther. In the box labeled "stamen"
color the anther dark blue, and the filament light blue. Pollen produced by the anther is carried by insects or
other animals to the pistil of another flower where it may fertilize the eggs.
The other flowers in the picture follow the same plan, although they come in many different colors and styles.
Color each of the flowers according to the colors above (blue for stamen, pink for pistil, bright colors for the
petals. etc.). Note that in some of the flowers, not all the structures are visible.
Plant Reproduction
Sexual reproduction in plants occurs when the pollen from an anther is transferred to the stigma. Plants can
fertilize themselves: called self-fertilization. Self-fertilization occurs when the pollen from an anther fertilizes the
eggs on the same flower. Cross-fertilization occurs when the pollen is transferred to the stigma of an entirely
different plant.
When the ovules are fertilized, they will develop into seeds. The petals of the flower fall off leaving only the
ovary behind, which will develop into a fruit. There are many different kinds of fruits, including apples and
oranges and peaches. A fruit is any structure that encloses and protects a seed, so fruits are also "helicopters"
and acorns, and bean pods. When you eat a fruit, you are actually eating the ovary of the flower.
1. What is an angiosperm?
2. The flower attaches to what part of the plant?
3. Why are flowers brightly colored?
4. Name two animals that might pollinate a plant.
5. If the petals of a flower are reduced or absent, how is the plant pollinated?
6. The female reproductive structures are called the__________________________
7. Name the three parts of the pistil:
8. Where are the ovules stored?
9. Name the two parts of the stamen:
10. Describe sexual reproduction in plants.
11. The ovary develops into what structure?
12. Define fruit.
13. Some flowers are not brightly colored at all, but have a very pungent odor that smells like rotting meat. How
do you think these flowers are pollinated?
14. In many flowers, the pistils and stamens reach maturity at different times. Considering what you know about
pollination, why would this be an advantage to the plant?
Legend:
Fill in the blank with the plant structure name and color the square the same color that was
used for coloring the structure
A: _______________
J:_________________
B :_______________
K: ________________
C: _______________
L: ________________
D: _______________
O: ________________
F:________________
P: ________________
H:________________
Biochemistry Test Review
I. Vocabulary: Know the definitions of the following:
a. matter
n. inorganic
z. ionic bond
b. atom
o. organic
aa. covalent bond
c. element
p. polar molecule
bb. activation
d. compound
q. hydrogen bond
energy
e. proton
r. dehydration
cc. endothermic
f. neutron
synthesis
reaction
g. electron
s. hydrolysis
dd. exothermic
h. atomic mass
t. carbohydrates
reaction
i. atomic number
u. monomer
ee. reactants
j. periodic table
v. polymer
ff. products
k. ion
w. protein
gg. ph scale
l. isotopes
x. lipid
hh. acid
m. diatomic element y. nucleic acid
ii. base
II. Questions?
1. Draw an atom of Sodium using the Bohr model.
2. Describe the difference between polar and non-polar molecules. Give
examples of each.
3. What do all organic molecules have in common? all inorganic?
4. Label the following diagrams as straight, branched, ring, saturated,
and/or unsaturated.
5. What are some examples of
a. monosacchrides?
b. disacchrides?
c. polysacchrides?
6. What are the monomers of:
a. carbohydrates—
b. proteins –
c. lipids –
d. nucleic acids –7. What are some of the functions of:
a. carbohydrates?
b. proteins?
c. lipids?
8. What is a solution? solute? solvent?
9. Describe the pH scale and compare the differences in an acid and a base.
10. What are some properties of water that help give it the name “universal
solvent”; creates such a strong surface tension; “cling” to other materials
such as creating a meniscus in a graduated cylinder?
11. In the McMush lab, describe the 4 tests were used to identify what
organic compound was present? (Remember you tested 4 different compounds, so you
need to identify those 4 compounds)
12. What is metabolism?
13. What is the role of an enzyme in a chemical reaction?
14. Create graphs showing how chemical reactions absorb and release energy.
15. Draw a graph of activation energy with and without an enzyme.
15. Identify these reactions as dehydration synthesis or hydrolysis and
identify the basic macromolecules involved (carbohydrates, lipids, proteins,
nucleic acids)
What type of bond does the following diagram represent? ________________
Fill in the “?” from the chart below.
Elements
Monomers
C,H,O
___________? 1:2:1
_________?
Lipids
Glycerol and
C,H,O
Bond Type
Example
Glycosidic
_________?
_________?
Ester
_____?
_________?
Nucleic
Acids
C,H,O, __?
C,H,O,
N, __?
______?
Peptide
Nucleotides
PhosphoDiester
Oils
_________?
Cholesterol
Enzymes
Insulin
Hemoglobin
_______?
RNA
1
Principles of Ecology
Ecology
•
•
•
Study of interactions that take place between organisms and their environments
Living things are affected by nonliving and living parts of the environment
Abiotic factors: nonliving parts of the environment
o
•
Air, temperature, moisture, light, soil
Biotic factors: living organisms in the environment
o
o
o
Producers: Organisms that take in energy from their surroundings to make their own food
(Plants and some bacteria)
Consumers: Organisms that eat (consume) other organisms for energy (animals)
Decomposers: Consumers that eat waste products for energy. Waste products are feces,
urine, fallen leaves, dead animals. (Fungi, some bacteria)
Ecology studies the relationship of organisms and their environment on several levels
• Organism
•
Population: group of organisms, all of the same species, which interbreed and live in the
same area at the same time
o
•
Biological community: group of populations that live in the same area at the same time
o
•
Organisms may compete with each other for resources such as food, water, space, mates, etc.
A change in one population can cause a change in another population
Ecosystem: a biological community and the nonliving things in the community’s environment
o
o
Terrestrial ecosystem: located on land
Aquatic ecosystem: located in water
2
•
Biosphere: portion of the Earth that supports living things
o Air, land, fresh water, salt water
Habitat
• the place where an organism lives out its life
• Niche: all the strategies and adaptations a species uses in its environment
o Includes all its interactions with the biotic and abiotic parts of the environment
o Each type of organism occupies its own niche to avoid competition with other types of
organisms
• Two species can share the same habitat but not the same niche
o Example: Ants and bacteria both live in the dirt (habitat) but have different niches.
Ants eat dead insects and bacteria eat dead leaves, dead logs, and animal waste. So
ants and bacteria don’t compete for resources.
Survival Relationships
•
•
Predator-prey: predators are consumers that hunt and eat other organisms called prey
Symbiosis: relationship in which one species lives on, in, or near another species and
affects its survival
o There are 3 types of symbiosis
1. Mutualism: type of symbiosis in which both species benefit
Ants living in the tropical acacia trees- trees are protected when ants attack
animals that try to feed on the tree and ants receive nectar and shelter from the
tree.
2. Commensalism: type of symbiosis in which one species benefits and the other species
is neither harmed nor benefited
Spanish moss grows on the branches of trees. The moss gets a habitat and the
tree gets nothing.
3. Parasitism: type of symbiosis in which one species benefits and the other species is
harmed
Parasite: organism that harms but does not kill another organism
Host: organism that is harmed by a parasite
Ticks feed on dogs, people, etc. The ticks get food (blood) and the hosts lose
blood and can be infected with disease.
3
Feeding Relationships
•
•
Autotrophs: Organisms that make their own food (plants and some bacteria)
Heterotrophs: Organisms that cannot make their own food and must eat other organisms
o Herbivores: eat plants (cows)
o Carnivores: eat meat (wolves)
o Omnivores: eat plants and meat (humans)
4
Trophic Levels and Food Chains
Trophic level: A feeding level in an ecosystem
Food chain: lineup of organisms that shows who eats who
o Shows how matter and energy move through an ecosystem
Eaten
by
2nd trophic
level: primary
consumer
(eats plants)
Eaten
by
Eaten
by
3rd trophic
level: secondary
consumer (eats
meat)
4th trophic
level: tertiary
consumer (eats
meat)
Eaten
by
Bacteria
1st trophic
level: producers
(make their
own food)
Last trophic
level:
decomposer
(eats dead
animals)
5
Energy Pyramid
Every time an organism eats, it obtains energy from its food
So energy is transferred from the 1st trophic level to the 2nd trophic level to the 3rd
trophic level and so on.
Some of this energy is lost along the way during an organism’s metabolism and as heat
This energy can be measured in kilocalories (kcal)
Energy pyramid: picture showing how much energy is transferred to the different
trophic levels in a food chain
Trophic Level
4th
Tertiary
consumers
rd
3
Secondary
consumers
nd
2
Primary
consumers
st
1
Producers
Energy Available
10 kcal/m2/year
100 kcal/m2/year
1000 kcal/m2/year
10,000
kcal/m2/year
6
Food web
A network of connected food chains
More realistic than a food chain because most organisms feed on more than one
species for food
Cycles in Nature
•
•
•
There is only a limited amount of resources (water, oxygen, nitrogen, carbon) on the earth
In order to keep these resources available to organisms, they must be recycled after they
are used
Cycle: a process that recycles a resource so that you end up with what you started with
Nitrogen Cycle
1. Nitrogen fixation: Bacteria in the
ground change nitrogen from the
atmosphere (N2) to different nitrogen
7
5. Denitrification: Bacteria change the
nitrogen compounds back to N2 and
release it to the atmosphere
4. Bacteria eat the dead animals and animal
waste and take in the nitrogen compounds
2. These bacteria live in plants and transfer the
nitrogen compounds to the plants
3. Animals eat the plants and take in the
nitrogen compounds
Bacteria change nitrogen compounds back
to nitrogen and release it into the
atmosphere
Nitrogen in atmosphere
Bacteria eat
dead animals
Bacteria in roots change
nitrogen to nitrogen
compounds
8
Water Cycle
Seepage: Water
seeps into the
ground and plants
use it
2.
Transpiration:
Plants give off
water to the
atmosphere
3.
Precipitation: Rain and snow fall from
the atmosphere to the earth
1.
Runoff: Extra
water runs off the
land to lower-lying
bodies of water
2.
Evaporation of
water from the
bodies of water
back into the
atmosphere
3.
9
Oxygen-Carbon Cycle
1. Carbon dioxide (CO2)
and
oxygen (O2) are found in
the atmosphere
to make
their own food
(photosynthesis)
2. Plants use CO2
3. During photosynthesis, plants release O2
back into the atmosphere
2. Animals and plants use the O2
to make energy
(respiration)
3. During respiration, animals and plants release
CO2 back
into the atmosphere
Food Chains and Webs --- "What's for dinner?"
Every organism needs to obtain energy in order to live. For
example, plants get energy from the sun, some animals eat plants, and
some animals eat other animals.
A food chain is the sequence of who eats whom in a biological
community (an ecosystem) to obtain nutrition. A food chain starts with
the primary energy source, usually the sun or boiling-hot deep sea
vents. The next link in the chain is an organism that makes its own
food from the primary energy source -- an example is photosynthetic
plants that make their own food from sunlight (using a process called
photosynthesis) and chemosynthetic bacteria that make their food
energy from chemicals in hydrothermal vents. These are called
autotrophs or primary producers.
Next come organisms that eat the autotrophs; these organisms
are called herbivores or primary consumers -- an example is a rabbit
that eats grass. The next link in the chain is animals that eat
1
herbivore - these are called secondary consumers -- an example is a
snake that eats rabbits. In turn, these animals are eaten by larger
predators -- an example is an owl that eats snakes. The tertiary
consumers are eaten by quaternary consumers -- an example is a hawk
that eats owls. Each food chain ends with a top predator and animal
with no natural enemies (like an alligator, hawk, or polar bear).
Food Chain Questions
1. What travels through a food chain or web?
2. What is the ultimate energy for all life on Earth?
3. Food chains start with what?
4. The 1st organism in a food chain must always be what type of organism?
5. Name 2 food making processes.
6. Where do chemosynthetic bacteria get their energy?
7. Define herbivore.
8. Herbivores are also called _________________________.
9. What are animals called that feed on herbivores?
10. Secondary consumers are eaten by larger ________________.
11. _________________ consumers eat secondary consumers.
12. Make a food chain with a producer and 3 consumers.
2
The arrows in a food chain show the
flow of energy, from the sun or
hydrothermal vent to a top predator.
As the energy flows from organism to
organism, energy is lost at each step.
A network of many food chains is
called a food web.
Trophic Levels:
The trophic level of an organism is the position it holds in a food chain.
1. Primary producers (organisms that make their own food from
sunlight and/or chemical energy from deep sea vents) are the
base of every food chain - these organisms are called autotrophs.
2. Primary consumers are animals that eat primary producers; they
are also called herbivores (plant-eaters).
3. Secondary consumers eat primary consumers. They are
carnivores (meat-eaters) and omnivores (animals that eat both
animals and plants).
4. Tertiary consumers eat secondary consumers.
5. Quaternary consumers eat tertiary consumers.
6. Food chains "end" with top predators, animals that have little or
no natural enemies.
When any organism dies, it is eventually eaten by detrivores (like
vultures, worms and crabs) and broken down by decomposers (mostly
bacteria and fungi), and the exchange of energy continues.
Some organisms' position in the food chain can vary as their
diet differs. For example, when a bear eats berries, the bear is
functioning as a primary consumer. When a bear eats a plant-eating
rodent, the bear is functioning as a secondary consumer. When the
bear eats salmon, the bear is functioning as a tertiary consumer (this
is because salmon is a secondary consumer, since salmon eat herring
that eat zooplankton that eat phytoplankton, that make their own
3
energy from sunlight). Think about how people's place in the food
chain varies - often within a single meal!
Food Web Questions
1. What is used to indicate the flow of energy in a food chain or web?
2. What happens to energy as we move from step to step in a chain or web?
3. Define food web.
4. What is meant by trophic levels?
5. Define autotroph.
6. The 1st trophic level consists of _______________ consumers called
_________________.
7. Name the 2nd trophic level (both names).
8. Secondary consumers may be _______________ eating meat or
_______________ that eat both plants and animals.
9. What is the 3rd trophic level called?
10. What is the 4th trophic level called?
11. At the 5th trophic level would be _____________ consumers that eat
_____________ consumers.
12. Give an example of 3 detrivores. On what do they feed?
4
13.
What organism feeds on dead plants and animals and helps recycle them?
14. Both ______________ and ______________act as decomposers
15. Can an organism fill more than one trophic level --- yes or no? Give an
example.
Numbers of Organisms:
In any food web, energy is lost each time one organism eats
another. Because of this, there have to be many more plants than
there are plant-eaters. There are more autotrophs than
heterotrophs, and more plant-eaters than meat-eaters. Each level has
about 10% less energy available to it because some of the energy is
lost as heat at each level. Although there is intense competition
between animals, there is also interdependence. When one species
goes extinct, it can affect an entire chain of other species and have
unpredictable consequences.
1. In food chains and webs, what trophic level must you have more of than
others?
2. Each trophic level has how much LESS energy?
3. What may happen if a species goes extinct?
Equilibrium
As the number of carnivores in a community increases, they eat
more and more of the herbivores, decreasing the herbivore population.
It then becomes harder and harder for the carnivores to find
herbivores to eat, and the population of carnivores decreases. In this
way, the carnivores and herbivores stay in a relatively stable
equilibrium, each limiting the other's population. A similar equilibrium
exists between plants and plant-eaters.
5
Complete the Food Chains Worksheet
Circle the organisms that complete the food chains below.
6
Food Chain Worksheet
Read the passage then answer the questions below.
7
Food Web Worksheet
Read the passage then answer the questions below.
8
Food Chain Quiz - Multiple choice comprehension questions
Color the circle by each correct answer.
9
Food Chain Quiz #2 - Multiple choice comprehension questions
Color the circle by each correct answer.
10
Match each Food Chain Word to its Definition.
11
Food Chain Trophic Levels - Worksheet
12
Have you ever seen a cat with a litter of baby kittens when all the kittens look
different? Each kitten may have different hair colors, markings, or eye colors.
Why? Each kitten received a different combination of genes from its parents.
1
Genes are segments of DNA that carry the instructions for the traits of an
organism from parents to offspring. Genes are located on chromosomes in the
nucleus of a cell. A chromosome is two very tightly coiled strands of DNA
(deoxyribonucleic acid).
2
Each type of organism has a fixed number of chromosomes. Humans have
46 chromosomes in every cell of their bodies, except in the egg and sperm cells.
Each egg and sperm cell has only 23 chromosomes. When an egg and a sperm
cell combine during fertilization, they produce one cell with 46 chromosomes.
3
Whether that offspring will be a boy or a girl is determined by the chromosome given to it by the
father. All egg cells have an X chromosome. All sperm cells have either an X or a Y chromosome. A
female (the mother) can only give an X chromosome. A male (the father) can give either an X or a Y
chromosome. If the father gives an X chromosome, the offspring will be a girl. If the father gives a Y
chromosome, the offspring will be a boy. It's the Y that makes the guy. This is a good way to remember
that males have a Y chromosome.
4
Each chromosome is divided into small sections called genes. Genes are the basic units of heredity.
They carry codes that control the individual traits that the offspring inherit. Traits in humans such as eye
color, height, skin color, face shape, shape of ear lobes, hairlines, and tongue rolling are all inherited
traits. Except for identical twins, each person has a unique arrangement of genes. A chromosome may
contain thousands of genes. Genes control traits. You inherited your genes and the traits they carry from
your parents. You don't look exactly like either parent because you received only some genes from each
parent. These genes combine in new ways during fertilization. Some genes control more than one trait,
and some traits are controlled by more than one gene.
5
People inherit two genes for every characteristic, and they get one gene from each parent.
Sometimes the two genes for one trait contain different codes. This affects how the trait appears in the
child. For example, maybe both parents have brown eyes. Let's say that they each have one gene for
brown eyes (B) and one gene for blue eyes (b). Brown eyes are dominant over blue eyes. That's why
both the parents have brown eyes, even though they carry a gene for blue eyes. The gene for blue eyes
is recessive. A person must have two genes for blue eyes for that person's eyes to be blue. There are
four different ways these two parents can pass the gene for eye color to any children they might have.
The father can give either a B or b gene. The mother can give either a B or a b gene. This results in four
different combinations: Bb, bB, BB, or bb. The chance that a child born to these two parents will have
brown eyes is 75%. Another way to say this is the probability is 3:1 that the child would have brown eyes.
For the four combinations above, in every gene pair that has the gene for brown eyes, shown with a
capital B, the child would have brown eyes. Two of those three children would also carry the gene for
blue eyes and might pass blue eyes to their own children. But the child who has the BB combination will
have only brown-eyed children.
6
Your genes determine your skin color, whether your hair is curly or straight, and whether or not you
can roll your tongue into a U-shape. Each of these three traits is controlled by a gene. Humans have
thousands of different genes. They are located on the 23 pairs of chromosomes in the nuclei of our body
cells. One pair of chromosomes is different from all the others in your cells. This chromosome pair
decides if you are male or female. Females have two X chromosomes (written XX). Males have one X
and one Y chromosome (written XY). The X and Y chromosome pair is the only pair that doesn't match in
size. The X chromosomes are larger than the Y chromosomes.
7
Sometimes genes controlling other traits are located on the X or Y chromosome. They are said to be
a sex-linked trait. One example is the trait for red/green colorblindness. It is a recessive trait found only
on the X chromosome, not the Y. Because males have only one X chromosome, they are more likely to
have colorblindness than females. Another example of a sex-linked trait is the bleeding disorder
8
hemophilia.
Your genes are not exactly the same as that of your parents or your siblings. The only exception is if
you have an identical twin. Identical twins are two individuals that formed from one egg fertilized by one
sperm. Because identical twins form from the same egg and sperm, they have exactly the same genes.
Identical twins are always either both boys or both girls. In science fiction, a clone is a person who has
an exact copy of someone else's DNA.
9
Not all twins are identical. Sometimes a female releases two egg cells at the same time. Each egg
can be fertilized by a different sperm cell and develop into a baby at the same time. This results in
fraternal twins. Unlike identical twins, fraternal twins are no more genetically similar than any other two
children from the same parents. Fraternal twins can be the same sex or different sexes.
10
1. Genes are ______.
2. How many chromosomes are in the skin cells
A Segments of DNA that carry the instructions
of your body?
for the traits of an organism from parents to
A 88
offspring
B 46
B Located on chromosomes in the nucleus of
C 23
a cell
C The basic units of heredity
D All of the above
3. How many chromosomes are in the egg and
sperm cells?
A 46
B 23
C 88
4. Girls have an XX chromosome. What do boys
have?
A BX
B XY
C XX
5. Why don't you look exactly like one of your
parents?
A Because you are not a clone
B Because you got only some genes from
each parent
C Because genes combine in different ways
during fertilization
D All of the above
6. Why are more males colorblind than females?
A Because colorblindness is a sex-linked trait
B Because males' eyes are different from
females' eyes
C Because males can't see as well as females
7. Identical twins can be different sexes.
A False
B True
8. All twins have exactly the same DNA.
A False
B True
Name ____________________________Date _______________ Period ________
Genetics Practice Problems #1
1. For each genotype below, indicate whether it is heterozygous (He) or homozygous (Ho)
AA_____
Ee_____
Ii_____
Mm_____
Pp_____
Bb_____
ff_____
Jj_____
nn_____
LL_____
Cc_____
Gg_____
kk_____
oo_____
HH_____
2. For each of the genotypes below determine what phenotypes would be possible.
Purple flowers are dominant to white flowers
Brown eyes are dominant to blue eyes
PP_____________________________
BB_________________________
Pp_____________________________
Bb_________________________
pp_____________________________
bb_________________________
Round seeds are dominant to wrinkled seeds
Bobtails in cats are recessive
RR_____________________________
TT_________________________
Rr_____________________________
Tt_________________________
rr_____________________________
tt_________________________
3. For each phenotype below, list the possible genotypes (remember to use the letter of the dominant trait)
Straight hair is dominant to curly
Pointed heads are dominant to round heads
__________ Straight
__________ Pointed
__________ Straight
__________ Pointed
__________ Curly
__________ Round
4. Set up the Punnett squares for each of the crosses listed below. Round seeds are
dominant to wrinkled seeds.
Rr x rr
round?_______
What percentage of the offspring will be
RR x rr
round?_______
What percentage of the offspring will be
RR x Rr
round?_______
What percentage of the offspring will be
Rr x Rr
round?______
What percentage of the offspring will be
Practice with Crosses. Show all work!
5. A TT (tall) plant is crossed with a tt (short plant). What percentage of the offspring will be tall? ___________
6. A Tt plant is crossed with a Tt plant. What percentage of the offspring will be short? ______
7. A heterozygous round seeded plant (Rr) is crossed with a homozygous round seeded plant (RR). What
percentage of the offspring will be homozygous (RR)? __________
8. A homozygous round seeded plant is crossed with a homozygous wrinkled seeded plant. What are the genotypes
of the parents? _________ x ________. What percentage of the offspring will also be homozygous?
___________
9. In pea plants purple flowers are dominant to white flowers. If two white flowered plants are cross, what
percentage of their offspring will be white flowered? ______________
10. A white flowered plant is crossed with a plant that is heterozygous for the trait. What percentage of the
offspring will have purple flowers?___________
11. Two plants, both heterozygous for the gene that controls flower color are crossed. What percentage of their
offspring will have purple flowers? ____________ What percentage will have white flowers? ___________
Name _____________________________Date _______________ Period _______
Genetics Practice Problems #2 - Writing Alleles
Directions: Using the data in Table 1, write the genotype that corresponds to the
phenotype descriptions
Table 1: Mendel's Traits and Symbols for Pea Plants
Traits
Dominant Allele
Symbol
Recessive Allele
Seed Shape
Round
R
Wrinkled
Seed Color
Yellow
Y
Green
Seed Coat Color
Colored
C
White
Pod Shape
Smooth
S
Constricted
Pod Color
Green
G
Yellow
Stem Height
Tall
T
Short
Flower Position
Axial
A
Terminal
Phenotype
Genotype
Symbol
r
y
c
s
g
t
a
Phenotype
1. Heterozygous for height
16. Constricted pod
2. Homozygous dominant for seed shape
17. Short height
3. Heterozygous colored seed coat
18. Green seed color
4. Homozygous green pod
19. Terminal flowers
5. Homozygous short
20. Pure wrinkled
6. Homozygous tall
21. Hybrid tall
7. Homozygous axial
22. Pure round
8. Homozygous terminal
23. Yellow seed pod
9. Heterozygous flower position
24. Hybrid smooth
10. Heterozygous seed color
25. Pure smooth pod
11. Homozygous smooth pod
26. Hybrid pod color
12. Homozygous constricted pod
27. White seed coat
13. Homozygous recessive for seed coat color
28. Wrinkled seed
14. Heterozygous for pod color
29. Pure colored seed coat
Genotype
15. Homozygous round seed
30. Hybrid flower position
Name _____________________________Date _______________ Period
________
Genetics Practice Problems #3 - Monohybrid Problems Worksheet 1
Directions: Using the table and rules below, complete Table 2:
If you use a separate sheet of paper to set up and solve your problems, attach work
showing Punnett Squares to receive credit. No Punnett squares – No credit
Rules for writing symbols
1. Dominant alleles are always capitalized usually by using the first letter of the trait as the symbol.
2. The recessive allele is always represented by the small case letter of the symbol for the dominant allele.
EXAMPLE: homozygous recessive for stem length x heterozygous for stem height
Genotypes
Phenotype Traits
Parents (P1) tt x Tt
T = tall stem (dominant allele)
Gametes (G1) t,t (male) T,t (female) t = short stem (recessive allele)
F1
By convention the dominant allele is written first
t
t
T
Tt
Tt
t
tt
tt
F1 = Filial 1 = the probable offsprings of Parents (P1)
Phenotypic Ratio = 2 Tall : 2 Short stems or 2 tall stem:2 short stem
Genotypic Ratio = 2 Tt : 2 tt...oor 1 Tt : 1 tt
Heterozygous for stem height : Homozygous recessive for stem height
.....
Table 1: Mendel's Traits and Symbols for Pea Plants
Traits
Dominant Allele
Symbol Recessive Allele
Symbol
Seed Shape
Round
R
Wrinkled
r
Seed Color
Yellow
Y
Green
y
Seed Coat Color
Colored
C
White
c
Pod Shape
Smooth
S
Constricted
s
Pod Color
Green
G
Yellow
g
Tall
T
Short
t
Axial
A
Terminal
a
Stem Height
Flower Position
Problems
1. Heterozygous for seed color x Homozygous dominant for seed color (Example)
2. Heterozygous for flower position x Heterozygous for flower position
3. Homozygous recessive for seed shape x Heterozygous for seed shape
4. Homozygous dominant for stem height x Homozygous recessive for stem height
6. Heterozygous seed color x Homozygous recessive for seed color
7. Constricted pea pod x Constricted pea pod
Table 2 Answers to monohybrid problems
Parent
Genotypes
1.
2.
3.
4.
5.
6.
7.
Male
Gametes
Female
Gametes
Phenotypic
Genotypic
Ratio
Ratio
Genetics Practice Problems #4
Name:____________________ Period:_____
1. If a black heterozygous guinea pig is crossed with a homozygous white guinea pig with the
genotype bb, what is the probability that the offspring will be white?
2. If two hybrid tall pea plants are crossed, what is the probability that the offspring will have the
tall phenotype?
3. The different forms of a gene are called _________________.
4._______As a result of meiosis, the number of chromosomes
a. is reduced by half in sex cells.
b. stays the same in sex cells.
c. is doubled in sex cells.
d. is quadrupled in sex cells.
5. ________The purpose of mitosis is to______________
a. make sex cells.
b. make gametes.
c. create identical cells.
d. create different cells.
6. Both parents have genotype Rr. What genotype could the offspring have?
7. A true-breeding tall pea plant is crossed with a true breeding short pea plant all the offspring
are tall. What is the most likely genotype of the offspring assuming a single gene trait?
8. If two white guinea pigs with genotype bb are crossed, what is the probability that the
offspring will be white?
9. _____Which of the following statements about DNA is true?
a. DNA is single-stranded.
b. DNA has the sugar ribose.
c. DNA contains uracil.
d. DNA contains thymine.
10. One parent has genotype DD and the other has dd. All of the offspring will be __________.
11. In guinea pigs, the allele for short hair is dominant. What genotype would a heterozygous
short haired guinea pig have? _______What genotype would a purebreeding short haired guinea
pig have? _______ What genotype would a long haired guinea pig have? ________
Genetics Practice Problems #7
Name:_________________________ Period:_____
DIHYBRID CROSSES
1. In pepper plants, green (G) fruit color is dominant to red (g) and round (R) fruit shape is
dominant to square (r) fruit shape. These two genes are located on different chromosomes.
a. What gamete types will be produced by a heterozygous green, round plant?
b. If two such heterozygous plants are crossed, what genotypes and phenotypes will be
seen in the offspring and in what proportions?
Gametes X
Proportion
Genotype
Phenotype
2. About 70% of Americans perceive a bitter taste from the chemical phenylthiocarbamide (PTC).
The ability to taste the chemical results from a dominant allele (T) and not being able to taste
PTC is the result of having two recessive alleles (t). Albinism is also a single locus trait with
normal pigment being dominant (A) and the lack of pigment being recessive (a).
A normally pigmented woman who cannot taste PTC has a father who is an albino taster. She
marries a homozygous, normally pigmented man who is a taster but who has a mother that does
not taste PTC.
a. What are the genotypes of the possible children? Hint: first determine the genotypes of
the parents.
Now that you have the genotypes of the parents, perform a Punnett square to determine what
the F1 offspring would be.
Possible genotypes
Gametes X
b What percentage of the children will be albinos?
c. What percentage of the children will be non-tasters of PTC?
d. If this couple had ten children how many of the children will be non-tasters of PTC.
3. Wolves are sometimes observed to have black coats and blue eyes.
Assume that these traits are controlled by single locus genes and are
located on different chromosomes. Assume further that normal coat
color (N) is dominant to black (n) and brown eyes (B) are dominant to blue
(b). Suppose the alpha male and alpha female of a pack (these are the
dominant individuals who do most of the breeding) are black with blue
eyes and normal colored with brown eyes, respectively. The female is also
heterozygous for both traits. What are the genotypes of the possible
offspring?
Possible genotypes
Gametes X
What percent of the offspring will be normal colored with blue eyes?
4. In the breeding season, male Anole lizards court females by bobbing their heads up and down
while displaying a colorful throat patch. Assume for this
question that both males and females bob their heads and have
throat patches. Assume also, that both traits are controlled
by single locus genes on separate chromosomes. Now, suppose
that anoles prefer to mate with lizards who bob their heads
fast (F) and have red throat patches (R) and that these two
alleles are dominant to their counterparts, slow bobbing and yellow throats.
A male lizard heterozygous for head bobbing and homozygous dominant for the red throat
patch mates with a female that is also heterozygous for head bobbing but is homozygous
recessive for yellow throat patches.
Possible genotypes
Gametes X
a. How many of the F1 offspring have the preferred fast bobbing / red throat phenotype
(assume 16 young)?
(assume 100 young)?
b. What percentage of the offspring will lack mates because they have both slow head bobbing
and yellow throats?
c. What percentage of the offspring will have trouble finding mates because they lack one of
the dominant traits?
5. Carrion beetles lay their eggs in dead animals and then bury them in
the ground until they hatch. Assume that the preference for fresh meat
(F) is dominant to the preference for rotted meat and that the tendency
to bury the meat shallow (S) is dominant to the tendency to bury the
meat deep(s). Suppose a female carrion beetle homozygous dominant for
both traits mates with a male homozygous recessive for both traits.
What will be the genotype of the F1 generation? What will be the
phenotype of the F1 generation?
What will be the phenotypic ratio of the F2 generation if two of the F1 generation mated?
Genotype
Phenotype
Gametes X
What will be the genotypic ratio of the F2 generation?
___FFSS : ___FFSs : ___FFss : ___FfSS : ___FfSs : ___Ffss : ___ffSS : ___ffSs : ___ffss
What will be the phenotypic ratio of the F2 generation?
6. Suppose in a strain of soybeans, high oil (H) content in the seeds is dominant to low oil content
and four seeds (E) in a pod is dominant to two seeds in a pod. A farmer crosses two soybean plants,
both with high oil content and four seeds per pod.
The resulting F1 offspring have a phenotypic ratio of 9:3:3:1 (High oil / four seeds : High oil / two
seeds : Low oil / four seeds : Low oil / two seeds).
a. What genotype were the parent plants?
b. Suppose the farmer chooses two of the high oil / four seed plants and crosses them. The F2
generation have all high oil / four seed phenotypes. What were two of the several possible
genotypes of the plants chosen by the farmer to cross?
c. Which known genotypes might the farmer cross her high oil / four seed plants with to determine
their genotype?
PATTERNS OF INHERITANCE AND MEIOSIS
I. History
Name:________________________________
Date:__________________ Period:_________
A. Gregor Mendel – 1865 Father of Genetics published a scientific paper of his research results
(Darwin had a copy of Mendel's paper, but never opened it)
1. Investigated inheritance using pea plants. Recorded 7 traits, including color and shape of
seeds, flower color, pod color and shape, height and position of flowers
2. Mendel discovered that traits could disappear in one generation, only to reappear in
another generation, e.g. Parents (P1) with pure-breeding strains of red x white flowers
=> all red flowers (F1). Self-pollination of F1 => 3 red + 1 white (F2). This illustrates the
disappearance of the color white flower in F1 generation and reappearance in F2
generation. After many more crosses Mendel suggested that there must be two
heritable factors in each individual, and that these factors (alleles) segregate at random
into gametes prior to mating. This conclusion is known as Mendel's first law: the Law
of Segregation.
3. We can predict Mendel's monohybrid results if CC and Cc all produce colored red flowers
while cc produces white flowers. Then CC (red) x cc (white) = Cc (red). We say that C
and c are alternate alleles at the flower color locus. In this example, red flower color is
dominant, i.e. the heterozygote genotype produces the same phenotype as one of the
homozygote genotypes. If one phenotype is dominant, then the alternate phenotype is
termed recessive. We see segregation of phenotypes in the F2 generation when two
heterozygotes are mated together.
4. A simple way to predict the relative frequencies of each phenotype is to use a Punnett
square, in which rows represent all possible alleles carried by eggs and columns
represent all possible alleles carried by sperm. Then, each cell represents the genotype
of the resulting zygote. Note, that if C and c are equally common in eggs and sperm, then
there will be 3 red genotypes and 1 white genotype, or a 3:1 ratio.
5. Mendel also collected data on crosses between strains which differed in two traits. For
example, he crossed a plant with round yellow seeds with a plant having wrinkled green
seeds.
The resulting F1 dihybrid cross produced approximately 9 round yellow, 3 round green, 3
wrinkled yellow and 1 wrinkled green plant (9:3:3:1 ratio). These ratios are predicted
from a Punnett square in which each gamete carries an allele from two loci. One locus is
for seed shape and the other is for seed color. R is dominant to r and causes round
seeds while G is dominant to g and causes yellow seeds. The tendency for two traits to
be inherited independently is known as Mendel’s second law: the Law of Independent
Assortment.
II. Meiosis causes segregation and independent assortment
A. Mitosis occurs by duplication of chromosomes, followed by one reduction division, thus one
cell turns into two cells that are identical.
B. Meiosis occurs by duplication of chromosomes, but is followed by two reduction divisions.
Thus, one cell turns into four gametes that are not identical, but instead contain ½ the
genetic material as the original cell.
1. Prophase I: homologous chromosomes condense, undergo duplication (forming sister
chromatids) and crossing over, and centrioles move to the poles (opposite side of cell)
2. Metaphase I: microtubules connect from the centrioles to the centromeres, and the
paired chromosomes line up along the equator of the cell
3. Anaphase I: paired homologous chromosomes separate and are pulled to alternate
poles
4. Telophase I: chromosomes relax, nuclear membrane and nucleolus forms, centrioles
move back together
5. Prophase II: chromosomes condense and centrioles move to the poles
6. Metaphase II: microtubules connect from the centrioles to the centromeres, and the
paired chromatids line up along the equator of the cell
7. Anaphase II: paired sister chromatids separate and are pulled to alternate poles
8. Telophase II: chromosomes relax, nuclear membrane and nucleolus forms, centrioles
move back together
III. Consequences of meiosis
A. Gamete formation. Note that meiosis in males (the sex with the smaller gamete)
produces four functional gametes, while meiosis in females (the sex with the larger gamete)
produces one functional gamete and three polar bodies, which disintegrate. This difference
in gamete size is called anisogamy. Some plants are isogamous and do not produce polar
bodies.
B. Meiosis also differs from mitosis because crossing over can occur during Prophase I.
Crossing over is also known as recombination. Recombination together with independent
assortment of chromosomes into gametes is responsible for Mendel’s second law: the Law of
Independent Assortment.
C. Maintains variation: recombination + independent assortment of chromosomes
1. Due to chromosomal segregation -> produces 2^n types of gametes. With 23 pairs
of chromosomes, each human produces 8 million gamete types without crossing over
2. This produces 70 trillion zygote combinations
3. And, each meiosis typically has 30 crossing-over events!
IV. Linkage (exceptions to Mendel's second law)
A. When genes are located near each other on a chromosomal, they do not assort independently.
-
Deduction from nonindependent assortment
Utility for gene mapping
Huntington's chorea.
B. Sex linkage
-
Color blindness and hemophilia
Name _________________________________________
Mrs. Chimento
Living Environment
GENETICS WORKSHEET
1. Label the pictures using the following words: DNA, RNA, bases, backbone, replication
2. The backbone is made up of
A) nitrogen
B) oxygen
C) sugar and phosphate
D) nitrogen and phosphate
3. What are the 4 bases in DNA? _____, _____, _____ and _____
How do the bases pair? _____ with _____ and _____ with _____
4. Fill in the chart below
DNA
RNA
# of strands
Sugar (Deoxyribose or Ribose)
Bases used
5. Label the parts of the diagram about protein synthesis:
(Hint: DNA  RNA)
(Hint: RNA  protein)
Word Bank DNA RNA Protein Translation Transcription Ribosome
6. Label the pictures: cloning, gel electrophoresis, recombinant DNA
______________________
____________________________
7. Fill in the Punnett Squares and answer the questions.
Mother: blue eyes (bb)
Father: brown eyes (Bb)
______ % of the offspring will have brown eyes
______ % of the offspring will have blue eyes
_______________________
Mother: tall (Tt)
Father: tall (Tt)
______ % of the offspring will be tall
______ % of the offspring will be short
8. Define the following words:
Replication: _____________________________________________________________________________
Mutation: _______________________________________________________________________________
Double Helix: ___________________________________________________________________________
9. Proteins are made up of
A) deoxyribose and phosphate
B) amino acids
C) nucleotides
D) bases
10. DNA and RNA are made up of
A) deoxyribose and phosphate
B) amino acids
C) nucleotides
D) bases
11.
Explain how you know the DNA came from 4 different people. _____________________________________________________
_____________________________________________________
_____________________________________________________ 12. Fill in the blanks with the following words:
tRNA radiation nucleus double helix a)
b)
c)
d)
e)
f)
g)
h)
amino acids restriction enzymes ribosomes mutation The DNA is located in the ______________________.
Proteins are made up of _______________________.
____________ carries an amino acid.
______________________ make proteins.
A ____________________ is a change in DNA.
____________________________ cut DNA.
The shape of DNA is called the ______________________________.
One thing that can cause mutations is ______________________________.
13. Label the diagram below:
Word Bank
amino acid base mRNA protein ribosome tRNA transcription translation 1
2
8
6
9
4
5
7
Key Concepts
At the molecular level, both diffusion and osmosis are random processes that result in a
net increase in entropy. (Entropy measures disorder in a system such as a group of
molecules.) In a solution, diffusion results in a net redistribution of molecules from an
area of higher concentration into an area of lower concentration. At dynamic equilibrium,
the molecules will be equally distributed throughout the solution. Osmosis is the
diffusion of water through a semipermeable membrane. Molecules that cannot diffuse
directly across a cell membrane can cross the membrane with the aid of either channel
proteins or transport proteins. Active transport requires energy, whereas passive transport
does not. Vesicle-mediated transport, such as endocytosis and exocytosis, is another
mode of transport and is active. Cells have receptors that receive extracellular signals.
Cells have evolved intracellular pathways to respond appropriately to those signals.
Lesson Objectives
•
•
•
•
•
•
•
Identify two ways that molecules and ions cross the plasma membrane.
Distinguish between diffusion and osmosis.
Identify the role of ion channels in facilitated diffusion.
Compare passive and active transport.
Identify the connection between vesicles and active transport.
Compare endocytosis and exocytosis.
Outline the process of cell communication.
Lesson Vocabulary
Lesson 3.3 Vocabulary
selectively permeable semipermeable
passive transport
diffusion
concentration gradient
equilibrium
hypertonic
hypotonic
isotonic
osmosis
contractile vacuole
facilitated diffusion
transport protein
channel protein
gated channel protein
carrier protein
active transport
sodium potassium pump
endocytosis
exocytosis
phagocytosis
homeostasis
ligand
G-protein linked receptor
second messenger
signal transduction pathway
Check Your Understanding
Recalling Prior Knowledge
Ask students what they already have learned about membranes. Ask: “What
characteristics do membranes have? How could these structural characteristics effect the
functioning of membranes?” These questions will serve as a bridge between Lesson 3.2
and Lesson 3.3. Give students about five minutes to write answers into the science
notebooks. Ask for answers.
Teaching Strategies
Demonstration
The following demonstration is designed to illustrate the concepts of osmosis and
tonicity. Cut two slices of approximately the same shape and size from a potato. (Cut the
slices so that they will easily fit into the bottom of a 250ml beaker.) Record their initial
masses on a scale. Place one slice into a labeled 250ml beaker that contains 75ml distilled
water. Place the other slice into a labeled 250ml beaker containing 75ml of a 15% sodium
chloride solution. Let the potatoes sit for 20 minutes. During this time, ask the students
questions such as those listed below:
1.
2.
3.
4.
What is osmosis?
What is a hypotonic solution? Isotonic? Hypertonic?
Which beaker contains the control for the experiment?
After
in their respective solutions, do you think that the mass of
either potato slice will change? If so, how?
At the end of
, remove the slices from the beakers. Blot very gently and
briefly on the paper towel to remove external water. Record the masses of both slices.
Discuss the actual and predicted results.
[The potato slice incubated in 15% salt solution will lose water by osmosis and will
weigh less at the end of 20 minutes]
Using Visuals: Figure 9
Figure 9 shows exocytosis at a synaptic junction. Reviewing this figure with your
students will reinforce their understanding of the concepts of vesicles, regulated
secretion, ligands (remind students that the word ligand is one of the vocabulary words in
this lesson), receptor proteins and cell-cell communication.
Make photocopies of the figure for groups of 2-4 students. Ask the students to label as
many of the structures in the figure as they can. When the groups are done, discuss as a
class the function of nerve cells [cell-cell communication, specifically transmission of
nervous impulses, refer to Nervous and Endocrine Systems chapter] and how specific
molecules/structures of nerve cells (neurotransmitters and receptors) enable the nerve
cells to accomplish their function.
Mode of exocytosis at a synaptic junction, where two nerve cells meet. Chemical signal
molecules are released from nerve cell A by exocytosis, and move toward receptors in
nerve cell B. Exocytosis is an important part in cell signaling.
Differentiated Instruction: Compare/Contrast Table
Instruct the students to make a table that compares and contrasts active transport and
passive transport across biological membranes. For this activity, students can work in
pairs. Teachers can pair SN, ELL, and LPR students with appropriate partners; one
partner should write down the group’s results in a table, and the other can present the
results to the class. Choose several pairs of students to present their results to the class.
ELL LPR SN
A sample table is below:
Type of
Transport
Energy
Required?
Protein Required?
Passive
No
Sometimes; depends upon the Movement of molecules
size and charge of the molecule down their concentration
being transported.
gradients.
Active
Yes
Yes
Result
Movement of molecules
up their concentration
gradients.
Enrichment: Research
Many topics in cell biology come to life when students can relate them to personal
experiences or to human health. The cell biology and medical aspects of cystic fibrosis
(mentioned in the Sodium-Potassium Pump section of Lesson 3) are quite interesting to
students because they directly link a cell biology topic (chloride channels) to a human
disease (cystic fibrosis). The website of the Cystic Fibrosis Foundation (
http://www.cff.org/AboutCF/Faqs/) provides an appropriate and global introduction of
cystic fibrosis to high school students.
For this enrichment activity, students who need additional challenges can pick one of the
bulleted questions (and its answer) to read, such as “How does CF affect the lungs?”
They then can prepare and deliver a mini-oral presentation that addresses the question. In
doing this project, students will get a jump ahead on the topics of Mendelian and
Molecular Genetics, since cystic fibrosis is an autosomal recessive disease.
Science Inquiry
Asking a Question
Teachers can do this activity as a demonstration or as part of a student laboratory lesson.
•
•
•
The Question: Does dissolving a solute (sugar) have an effect on the final volume
of a solute in which it is dissolved?
Control: Place 80ml water in a 100 ml graduated cylinder. Record the volume.
(80ml)
Treatment A: Dissolve 5g sugar in 80ml water in a 250ml beaker. Use a stirring
rod to speed up the process. When the sugar is dissolved, transfer the solution to a
100 ml graduated cylinder and record the volume.
____ ml
•
Treatment B: Dissolve 20g sugar in 80ml water in a 250ml beaker; use a stirring
rod to speed up the process. When the sugar is dissolved, transfer the solution to a
100ml graduated cylinder and record the volume.
____ ml
The dissolved sugar will increase the volume to over 80ml in both the solutions; discuss
with your class why this might be.