Day 18 - Chapter 6 and Final Exam Preparation

Students should prepare for tomorrow's final exam by going over Unit tests and Chapter quizes. Use the website, your text, tests, and previous homework assignments to help you study. You will be allowed one sheet of paper to help you as a "cheat sheet" on tomorrow's final exam. There are 3 sections, and 20 questions (or so) in each section.

You must bring a pencil! The marking machine cannot read anything other than pencil. No one leaves the room for any reason during the final exam. Go to the bathroom and get a drink before class.

Please bring your textbooks for Friday. They will be collected. If you don't bring it in, you will owe us money and the office may not pass you to the next grade without it!

Good Luck!

Here are the answers to yesterday's homework:

p. 215
1. Unique proteins and sugars on the surfaces of
eggs and sperm help in species identification.
2. The method of fertilization for land-dwelling
animals is usually internal fertilization.
3. The method of fertilization for water-dwelling
animals is usually external fertilization.
4. Pollination is the method of internal fertilization
for land-dwelling plants, where sperm is
transferred to the female productive part of
the plant.
5. Within a seed is a plant embryo and stored
food for the embryo.

Pg 223 -

1. For successful sexual reproduction to occur,
two parents of the same species are required,
and two gametes must come together for fertilization.
2. The three stages of sexual reproduction are
mating, where gametes are brought together;
fertilization, which is the union of the egg and
sperm; and development, which is a series of
mitotic and cell divisions of the zygote that
form the embryo and fetus.
3. Answers may vary. Mammals that mate in
water include whales, sea lions, sea otters, dolphins,
and seals.
4. Internal fertilization occurs when the sperm
cells are deposited inside the female’s body
where they meet the egg. Usually only one
sperm can fertilize an egg.
5. External fertilization occurs when a sperm and
egg unite outside the bodies of the parents.
6. When an egg and sperm unite, this restores
the diploid number of chromosomes. If more
than one sperm was able to fertilize the egg,
the fertilized egg would have more than the
diploid number of chromosomes. The fertilized
egg would be unable to undergo any
more cell divisions as the egg would not pass
the checkpoints because of the incorrect number
of chromosomes.

7. Water or water-containing fluid is necessary
for animals that reproduce sexually to prevent
the dehydration of the egg, sperm, and
embryo. This is not a problem in water but
does become a problem on land.
8. In plants, the pollen tube delivers the sperm to
the egg.
9. In flowering plants, the seed is enclosed in a
fruit. In cone-bearing plants, the seed is protected
within the female cone.

Pg. 232 - 233

Checking Concepts
1. Meiosis is necessary for multicellular organisms
so that the chromosome number can be
retained and so that genetic variation can
occur.
2. Meiosis II is very similar to mitosis since in
both processes sister chromatids separate.
3. At the beginning of meiosis, the parent cell is
diploid. At the end of meiosis, there are four
haploid cells.
4. The two events that produce genetic variation
are crossing over, where genetic information is
exchanged between non-sister chromatids, and
independent assortment, where there are two
possibilities for how a chromosome will sort
itself into daughter cells.
5. Crossing over is like shuffling a deck of cards
because there are many, many possibilities of
how the genetic material in a gamete will
order itself. Crossing over can occur multiple
times, like cutting the cards and shuffling a
deck of cards.
6. You are not identical to your parents or siblings
because of the reshuffling from crossing
over and independent assortment. In independent
assortment, the egg contained chromosomes
from your grandparents on your
mother’s side, and the sperm contained genetic
information from your grandparents on your
father’s side. For each chromosome in the egg,
there was a 50% chance that you inherited
your grandmother’s genetic information, 50%
that the genetic information was from your
grandfather on your mother’s side. This is true
for all 23 chromosomes, so this is 223 possibilities
just from the egg, and there would be 223
possibilities for the sperm.
7. A karyotype allows geneticists to determine
whether there has been a chromosomal mutation.
A whole chromosome could have been
deleted or added, or a piece of a chromosome
could have been added, deleted, or moved
onto another chromosome.
8. The syndrome with three chromosomes 21s
is Trisomy 21, commonly known as Down
syndrome.
9. Answers will vary as there are many ways that
students could connect these ideas. Check for
correct associations.
10. (a) Internal fertilization
(b) External fertilization
(c) External fertilization
(d) Both, since this is sexual reproduction
from the union of the egg and sperm
11. (a) The period of rapid growth rate is from
three to six months.
(b) The growth is the slowest between the
sixth and seventh month.

(c) The fastest growth rate shows the steepest
slope on the graph. The slowest growth
rate is shown in the least steep slope.
Understanding Key Ideas
12. The purpose of fertilization is to join the egg
and the sperm, to restore the diploid number
for the offspring.
13. External fertilization is suited to aquatic environments
because the eggs, sperm, and zygote
will not dry out, and the water helps disperse
the eggs and sperm.
14. A single fertilized egg grows into a multicellular
embryo by dividing millions of times by
mitosis. The cells differentiate and become
specialized to perform a particular function.
This means certain genes will now be read and
other genes will no longer be read.
15. Pollen is male sperm and therefore contains
DNA. Each species would have unique DNA
in the pollen that might help in a crime investigation.
16. (a) 1. Ectoderm; 2. mesoderm; 3. endoderm
(b) Answers may vary but should include any
one of each of the following organs.
Ectoderm: skin, nervous system; mesoderm:
kidneys, reproductive organs;
endoderm: lining of digestive system,
lungs, liver
17. Scientists prefer to use embryonic stem cells
because these cells have the potential to
become any type of cell. Teenage or adult stem
cells can become only a few different types of
cells. For example, an adult blood stem cell
could become only blood tissue, not muscle
cells or skin cells.
18. The researcher is looking at a karyotype.
By doing this analysis, the researcher can
determine if the person has a chromosome
mutation.
19. Reproductive technology has an impact on
society because it helps infertile couples to
conceive. However, the technology raises
many ethical and other questions, such as
should these technologies be free and available
to everyone, should we be selecting for
embryos, who are the biological and legal parents
of the child, and what do we do with the
unused embryos.


Chapter 6 Quiz
1. A
2. C
3. D
4. C
5. D
6. B
7. A
8. A
9. D
10. B
11. D
12. E
13. F
14. A
15. B
16. C