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Reproduction in animals
1.
2. Two types of Reproduction
1. Asexual 2. Sexual
Offspring are produced
by a single parent;
No sperm and egg
needed
Involves the fusion
of two cells, one
from a male and the
other from a female
3. Which type of reproduction produces
clones?
Asexual reproduction.
Offspring are genetically identical
4. Fertilisation is the fusion of the
male and female gamete nuclei to
form a zygote
Zygote is the first cell that forms after
fertilisation
6. Fertilisation can be:
a) Internal:
in reptiles, birds & mammals
b) External:
in most fish & amphibians
7. Why is internal fertilisation essential
amongst land animals?
No water in the animal’s immediate environment
to carry the sperm cells to the eggs
8. A cod [fish] lays millions of eggs in one year but
a rabbit produces only a few thousand.
Question
9. External fertilisation in fish:
Not all eggs are fertilised
Young ones are not protected by the mother’s
body
10. Table 1 Comparison of sexual and
asexual reproduction.
ASEXUAL SEXUAL
1) One parent needed
Two parents needed, a male
and a female
2) No gametes required
(sex cells)
Gametes required
3) Offspring are
genetically identical
(clones)
Offspring are not genetically
identical
11. Table 1 Comparison of sexual and
asexual reproduction.
ASEXUAL SEXUAL
4) Only one individual is
needed to colonise a
new area
A male and a female are
needed
5) A fast process A slow process
6) Always increases the
population
Does not always increase the
population
7) Very common among
plants and simple
animals
Almost all animals and
plants
12. ASEXUAL SEXUAL
Advantage:
a good characteristic
shows up in all the
offspring
Advantage:
new varieties are produced,
which may be more able to
adapt to the new
environment
Disadvantage:
a defect in the parent
shows up in all
offspring ; no variation
occurs
Disadvantage:
excellent individuals cannot
give identical offspring
13. Gonads & Gametes
MALE FEMALE
Gonads [sex
organs]
Testes Ovaries
Gametes
[sex cells]
Sperm Ovum / egg
Gametes are produced by a type of cell
division called:
Meiosis
16. The male Excretory & Reproductive
Systems
bladder
ureter
sphincter muscle
prostate gland
urethra
testis
scrotum
penis
sperm duct
17. Functions of the testes:
1. Produce sperms
2. Produce the sex hormone testosterone
18. Function of the epididymis:
Stores sperms for 2-3 months
[6m long but
coiled = 3.8cm]
19. Function of the sperm duct:
Stores sperms
A passageway for
sperms from
epididymis to
urethra
20.
21. Scrotum
holds testes outside the body
temperature of about 1-2C lower than
body temperature
sperms only develop properly inside the
testes at a slightly cooler temperature
heat can cause
infertility
22. ejaculation
is the expulsion of semen from the
urethra
copulation (sexual intercourse / mating)
is when the man's penis is inserted into
the woman's vagina and excited until
orgasm and ejaculation occur
23. Semen = fluids + sperms
Semen from a
bull Semen from
a dog
24. Human semen contains
90-600 million sperms in 3 cm3 of ejaculate
or semen
Normal sperm
count
Low sperm
count
Why are sperms produced in large numbers?
Increase chance
for fertilisation
25. Fluids in semen are released from the:
seminal vesicles
prostate gland
26. semen contains:
alkali
sugars
proteins
Urine is
ACIDIC.
Functions of the fluid:
1. the fluid keeps the sperms alive
2. helps them to swim vigorously
35. Question: JUNE 1998
What are the main differences between a
sperm and an ovum? (4 marks)
SPERM OVUM
1. Small Large
2. Has a tail No tail
3. Has an acrosome No acrosome
4. No food reserves Has food reserves
36. Question: SEP 2006
The female egg and the male sperm are two
specialized cells. Compare the egg and the
sperm in each of the following characteristics:
i) size (2 marks)
ii) numbers produced (2 marks)
iii) movement. (2 marks)
37. Fig. 4 The human female reproductive
system.
Endometrium
(uterus lining)
Uterus
Cervix
Vagina
Ovary
Fallopian tube
(oviduct)
‘womb’ – common
term for uterus
39. Ovulation
the release of an ovum from the ovary
occurs once every 28 days
Developing follicles
Mature follicle
Corpus luteum /yellow body
Ovulation
Graafian follicle
46. Functions of:
Fallopian tubes:
1. Pathway for sperms to reach the ovum
2. Fertilisation occurs inside it
3. Has cilia and is muscular to move
ovum towards uterus
47. Functions of:
Uterus:
1. An embryo attaches to the uterus lining
(becomes implanted)
2. An embryo develops inside it
3. Muscles in uterus contract to give birth
implantation
48. Functions of:
Cervix:
1. To allow menstrual blood to flow into the
vagina
2. To direct the path of sperm into the uterus so
fertilisation may occur
3. Becomes blocked by mucus when pregnant to
avoid infections
49. Functions of:
Vagina:
1. Penis is inserted to deposit semen
2. Passageway for menstrual blood
3. Serves as the birth canal
51. Question: MAY 2012
Describe the role of each of the following in a
female:
i) vagina; (3)
ii) oviduct; (1)
iii) ovary; (3)
iv) uterus. (2)
52. Question: MAY 1999
Trace the path of the male gamete, from its site
of origin until it reaches the female gamete in a
mammal.
Diagrams are not expected, but detail of how
and what helps the male gamete to reach the
female gamete at the site where fertilisation
usually takes place, are important.
(10 marks)
64. Puberty
is the stage of the beginning of sexual maturity
In girls:
12-15 years
In boys:
13-17 years
65. Primary sexual characteristics
appear in the growth and enlargement of the
reproductive organs
In boys:
sperm production
ejaculation starts
In girls:
ovulation starts
81. Control of the menstrual cycle
Hormone Function
FSH Causes ovary follicles to develop
LH
Causes ovulation; Causes corpus
luteum to form from follicle
Oestrogen
Causes repair of the uterus lining
before ovulation
Progesterone
Causes uterus lining to remain thick
after ovulation
84. Changes which occurred in the thickness of the
lining of the uterus of a woman over 84 days.
With reference to the graph :
What took place during days 0 to 5 and days 28 to 33?
Menstruation
90. How is it possible for only ONE sperm
to penetrate the ovum?
a fertilisation membrane forms around the
ovum to act as a barrier soon after a sperm
enters
99. Functions of the Placenta
1. produces the hormones oestrogen and
progesterone which stop menstruation and
prevent further eggs being produced by the
ovaries
2. allows food and oxygen to enter the foetus
3. helps to remove wastes like urea and carbon
dioxide from foetus
101. Question: MAY 2010 IIB
List TWO ways how a sexually transmitted disease
(STD) can be transmitted from a pregnant mother
to the baby. (4)
1. Microbes can cross the placenta and infect the
baby before birth.
2. Microbes can be transmitted from mother to
baby during the delivery as the baby passes
through the birth canal.
3. During breastfeeding as is the case of HIV.
102. List TWO precautions that can reduce the
incidence of STDs. (4)
Use of latex condoms for vaginal, anal and oral sex during
sexual contact/
If you have an STD do not have sex until treated and cured/
Avoid multiple sex partners/avoid casual
encounters/abstain (do not have sex)/ ask partner about
STD/regular check up
Any TWO or equivalent 4 marks
Do not award any mark if students mention contraception
(unless condoms are specifically mentioned)/ more sexual
education.
If students mention protection award 1 mark only.
103. Functions of the amniotic fluid:-
1. acts as a shock-absorber
2. keeps a constant temperature
3. keeps the embryo buoyant and free to grow
8 weeks
106. Question: SEP 2002
Copulation in humans may result in
fertilization. When fertilization occurs, it
may result in the formation of a single
zygote, identical twins, or fraternal twins.
Explain clearly what happens when
fertilisation results in the formation of:
(I) a single zygote; (II) identical twins; and
(III) fraternal twins. (2, 3, 2 marks)
107. Question: MAY 2012
1. List TWO physical changes that can
indicate that a female is pregnant. (2)
a. Breasts enlarge
b. Weight is gained
108. Question: MAY 2012
2. During the ninth month of pregnancy, the
female undergoes shortness of breath. Give
a reason for this observation. (1)
Uterus expands and lungs get compressed.
110. gestation
the period from fertilisation to birth
labour
the uterus begins to undergo occasional
contractions which become steadily
more frequent and powerful
111. oxytocin
a hormone made by the pituitary gland
What causes the uterus to contract?
Uterus between
contractions
Uterus during
contractions
113. Afterbirth
the placenta comes away from the wall of
the uterus and passes out of the vagina
TWINS!!
114. During pregnancy the cervix is
blocked by a mucus plug. Why?
To prevent infection
The mucus plug comes out as the cervix
dilates in labour or shortly before
115. Question: MAY 2011
6a.The following diagram shows the four stages of
the human menstrual cycle.
i) Briefly describe the changes taking place at
each stage 1, 2, 3 and 4. (10)
116. b. During gestation the placenta develops into a
large disc bearing many finger-like villi.
i) Explain how the placenta is joined to the foetus.
(1)
By means of the umbilical cord which contains
blood vessels.
117. ii) Explain why in dizygotic (non-identical) twins
there are two placentas. (3)
Two eggs/ova and two sperms were needed to
produce non-identical twins.
Each egg/ovum was fertilised and two separate
zygotes formed.
Each zygote produced a different individual.
iii)What happens to the placenta after birth? (2)
The uterus contracts to expel the placenta. This
is called afterbirth.
118. Parental Care involves
1. feeding the baby (lactation)
mammary glands secrete milk
2. keeping baby clean
3. warm
119. Breast-feeding
allows close contact between the mother
and her baby, which is good for both of
them, physically and emotionally
120. The mother’s milk is perfect food for
the baby because it contains:
1. all the necessary nutrients
2. the mother’s antibodies which makes the baby
immune from disease during the first few
months of life
121. A newborn baby cannot take in solid
food because:
no teeth to chew
the digestive system cannot deal with
solid food
122. Colostrum:
is produced by the breasts beginning during
pregnancy and continuing through the early
days of breastfeeding
123. Colostrum:
is yellow to orange in colour and thick and sticky
is low in fat, and high in
carbohydrates, protein, and antibodies to help
keep the baby healthy
Colostrum Breast milk
124. Colostrum:
is extremely easy to digest, and is therefore the
perfect first food for the baby
has a mild laxative effect, helping the baby to egest
for the first time
has white blood cells in it to protect baby from
viruses and bacteria
127. Birth control or Contraception
contraception is any procedure which
prevents fertilisation
Three groups:
1. stop sperms reaching the egg
2. stop the eggs being produced
3. stop the fertilised egg from developing in
the uterus [not in syllabus]
128. Birth control methods can be:
Natural e.g.
temperature (thermal) method
the mucus Billings method
Artificial e.g.
use of the:
Condom
Diaphragm
Contraceptive pill
129. None of the contraceptive methods is
100% effective.
130. What is the MOST effective method
of avoiding pregnancy?
134. If pregnant:
no menstruation
the body temperature
remains up
throughout pregnancy
The temperature is low until ovulation, after which it rises
for 10-16 days, and drops back with onset of period.
137. Why is mucus produced at the cervix?
to protect the sperm from the acidity in the
vagina
to allow sperm to move freely through the
cervix
138. Days with & without mucus during
the menstrual cycle
Pre-ovulation:
no mucus
Post-ovulation:
no mucus
139. Pre-Ovulation
Dry at first
Gradually, more mucus will accumulate –
yellow, cloudy, or white in color and sticky to
the touch.
Texture of mucus changes
140. Approaching Ovulation
the cervical mucus will increase
first, there will be a moistness or
stickiness to the mucus, as well as a white
or cream-colored appearance.
141. During Ovulation
mucus = large amount ; resembles “egg
whites”, often semitransparent.
mucus = increasingly slippery and
‘stretchable’. This is the most fertile time.
146. Question: MAY 2010
Compare the cervical mucus in the female
reproductive system at ovulation and after
ovulation. (2)
At ovulation, cervical mucus gets very wet,
stretches between the fingers for an inch or
more, and resembles raw egg white. After
ovulation, cervical mucus becomes sticky and
cloudier and dryness may also result.
147. The sheath (condom)
is worn by the male over the erect penis
forms a barrier to sperms
148. The sheath (condom)
is quite reliable if used properly; best to use it
with a spermicide
disadvantage:
can tear
slip off
149.
150. The cap or diaphragm (fig. 17)
is worn by the female just before sex
a barrier to sperms
disadvantage:
can slip out of place
154. The oral contraceptive pill:
taken by the female to prevent any eggs
being produced in the ovary
it stops ovulation
one tablet is taken
daily throughout the
menstrual cycle except
for about a week
during menstruation
155. The oral contraceptive pill:
contains chemical substances identical to
oestrogen and progesterone
very effective
Disadvantages:
1. can raise blood pressure
2. cause an increase in weight
156. Sterilisation:
the person has an operation which prevents
conception permanently
Vasectomy:
Sterilisation of a man
about 1 in 2,000 men
can become fertile
again after a
vasectomy
157. Tubal ligation:
Sterilisation of a woman
more than 99% effective
1 in 200 women will
become pregnant after
being sterilised
158. there is a slightly higher risk of ectopic
pregnancy after tubal ligation
160. Question: MAY 2012
A young female had a contraceptive implant in
which tubes of progestin (a form of
progesterone) were implanted under the skin.
Name TWO hormones that are not released from
the pituitary gland as a consequence of this. (2)
FSH
LH
161. Question: MAY 2009
Describe each of the following processes and
explain the benefits of each:
vasectomy; (3)
Vasectomy is a form of relatively permanent
birth control method/contraception in males.
The sperm ducts are cut and tied in a surgical
operation to prevent sperms from being
ejaculated.
162. Question: MAY, 2010
1) Explain why a male still continues to have a
deep voice after he undergoes a vasectomy?
A deep voice is due to the effect of testosterone.
This sex hormone is still produced in the body.
2) Explain why after a vasectomy the seminal fluid
contains no sperm. (3)
As the sperm ducts are cut and tied and sperms
cannot move into the urethra.