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12 Reproduction
#106 Types of reproduction

Reproduction is the process that makes more of the same kind of an
organism
...

1
...

formation of a new organism, without involvement of gametes or
fertilisation
...
Inside an individual bacterium, the
DNA replictates
...
Once the
daughter cells have grown, they can also
reproduce
...

When ripe, the sporangium bursts open
allowing the spores to be dispersed
...

Potatoes
Potatoes are stem tubers
...
Each tuber
contains stored starch, and there are
buds in depressions in the surface known
as eyes
...
Each tuber can
form a new plant
...
Sexual reproduction:


the process involving the fusion of haploid nuclei to form a diploid
zygote and the production of genetically dissimilar offspring
...
youtube
...
youtube
...

Pollination can take place with the help of agents: wind or insects
...


Pollen grains
...
When
animals such as insects carry pollen, they aid pollination
...


Growth of pollen tube and the process of fertilization
Figure below shows a section through a single carpel
...
Germination is triggered by a sugary solution on the stigma, an
involves the growth of a pollen tube from the pollen grain
...
The pollen tube grows down the style, through the
ovary wall, and through the micropyle of the ovule
...
If the
ovary contains a lot of ovules, each will need to be fertilised by a different
pollen nucleus
...
youtube
...
youtube
...


#109 Formation of seed, conditions affecting germination

The fertilised ovule divides by mitosis to form a seed containing the embryo
plant and food stores called cotyledons
...

The ovary wall develops into a fruit, which may be fleshy (e
...
plum)
or a dry pod (e
...
lupin or pea)
...


a) Name the parts labeled A and B

[2 marks]

b) This flower is insect-pollinated
...

[3 marks]
c) After pollination, the ovules develop into seeds
...

c) Four points form:
- pollen grains germinate
- pollen tube grows down the style
- through the micropyle
- into the ovule
- the male nucleus fuses with the female nucleus
- reference to fertilisation

Environmental conditions affecting germination

1
...


2
...
Warmth/temperature: enzymes present in the seed get activated and
work best at optimum temperature (20-400C) which trigger growth in the
baby plant
...
Light intensity: high or very low light intensity does not allow enzymes
to function normally
...


Nutmeg is dispersed by birds
...
unl
...
Wind-dispersed seeds


Fruits contain seeds, and usually have a parachute or a wing to help
them be carried away from the parent plant by the wind
...
The fruit
counterbalances the pappus
...
When the fruit drops off the
tree it spins, slowing down in descent
...


2
...

Succulent fruits attract animals because they are
brightly coloured, juicy and nutritious
...
The faeces provides nutrients
when the seeds germinate
...
Eventually the
seeds drops off, or the animal grooms itself to
remove them
...


Try this
Figure below shows a section through a bean seed
...
i) Name the parts labeled A, B and C
...

[1 mark]
2
...

i)Sketch a seed or fruit that is adapted for dispersal by wind
...
[1
mark]
ii) Suggest how this feature helps in wind dispersal
...

[1 mark]
Answer
1
...

2
...

ii) Two points from:
- description of how the feature catches the wind
- and slows down the descent of the seed or fruit
- so the seed or fruit is carried away from the parent plant
...

https://www
...
com/watch?v=buZV0h4vfmQ

#111 Self-pollination and cross-pollination
Self-pollination - transfer of pollen from the anther to the stigma of the
same flower, or to another flower of the same plant
...

Self-pollination
 ↑ chance of successful pollination à smaller numbers of pollen
 ↑ chance of fertilisation and seed formation
 ↓variation in the offspring
...


Cross-pollination
 ↓ chance of successful pollination à large amounts of pollen
 ↓ chance of fertilisation
 ↑ variation
 ↑ ability to adapt to environmental change
...

Development - increase in complexity

1
...
As the number of cells
increases, they become differentiated (specialized for different tasks)
...

Examples:
- nerve cells are very elongated and can transmit electrical impulses
- xylem cells are elongated and lose their cell contents, with the cell walls
becoming lignified so the cells conduct water efficiently
...
Growth
- due to an increase in cells, produced by mitosis
...

Dry mass






Often used as a measure of growth, because wet mass varies from day
to day (e
...
plant will take up more water on a wet day than on a dry
day, but the water does not all become part of the biomass – living
material of the plant)
...

Many individual have to be germinated at the same time and grown in
the same conditions
...


Example: Changes of dry mass during the growth of a plant from a seed
...

- ↑ when the plumule stars to photosynthesise, and foliage leaves form to
continue the process
...


Try this
1
...


i) What is the role of part A?

[1 mark]

ii) What do parts B and C of the seed develop into after germination? [2
marks]
2
...


i) Why is mass measured as dry mass?

[1 mark]

ii) Explain the changes in dry mass between days X and Y in both sets of
seedling
...

[4 marks]
Answer
1
...

ii) B develops into the shoot (or leaves)
C develops into the root
...
i) Wet mass varies according to the amount of water absorbed of lost
from the plant, or dry mass represents the amount of cytoplasm
...

iii) Four points from:
- set Q increases in dry mass and st P decreases in mass
- set Q is in the light and can photosynthesise
- to make new cytoplasm
- set P is in the dark and can not photosynthesise
- set P uses up remaining food stores through respiration
...

At first, it is just one single cell, which duplicates over
and over until after 9 months…… TA-Dahh! - A baby is
born!

Male reproductive system







Testes: produce sperm and testosterone
Scrotum: a sac that keeps testes cool (outside body)
Sperm ducts: link testis to urethra: allow passage of semen
containing sperm
Prostate gland: produce alkaline fluid ---> semen
Urethra: urinate; pass semen (+sperm) through penis
Penis: become firm, inserted into vagina during sexual intercourse --> transfer sperm

Female reproductive system






Ovaries: contains follicles, produce
and stores eggs, produce oestrogen
Oviducts: carries ovum to uterus; Fallopian tubes = site of
fertilisation
Uterus – where fetus develops
Cervix- a ring of muscles that separate the vagina from the uterus
Vagina: receives sperm from erect penis during intercourse

Comparing male and female gametes

Slide Show: Reproduction from TGES Biology
http://tgesbiology
...
com/uploads/9/0/8/0/9080078/reproduction
...
youtube
...
The cycle lasts about 28 days
...
Menstruation







Usually, one egg is released from an ovary every month
...
It is full of tiny blood vessels, ready to
supply the embryo with food and oxygen if it should arrive
...

Is does not sink into the spongy wall, but continues onwards, down
through the vagina
...

This is called menstruation, or period and it last for about 5 days
...
Ovulation






Ovary
a follicle develops
secretes oestrogen
↑↑ oestrogen in the blood
...


When the follicle is fully developed ---> LH ↑↑↑↑ and FSH ↑↑


follicles rupture and release fully
developed ovarian cells (ovulation)



empty follicle stops secreting
oestrogen
becomes a corpus luteum
secretes progesterone
uterus lining thick, spongy, well
supplied with blood in case a egg is
fertilised
...
One sperm may fertilise the egg to
produce a zygote
...
Very
slowly, the egg travels towards the uterus
...
By
this time, it has only traveled a short way along the oviduct
...


1
...






When stimulated, spongy tissue in the penis filled with blood and
becomes erect
...

Muscles in the wall of the sperm duct help to propel the semen forward
The sperms with their tails swim from the vagina, through the cervix
and uterus, into an oviduct
...
Fertilisation happens in the oviduct



ovum/egg pass down in oviduct
a single sperm penetrates the membrane of ovum by secreting a protease
enzyme; only the head of the sperm goes in, the tail is left outside
...


3
...
As it goes,
it divides by mitosis
...


Egg implanting in uterus
...


Credit: soc
...
edu

#116 The development of the fetus
The blastula develops into an embryo and some of the cells form
a placenta, linking the embryo with the uterus lining
...


Growth of the fetus requires a good supply of nutrients and O2
...
The placenta is soft and dark res, and has fingerlike projections called villi
...


1
...
Placenta
Brings blood supply of fetus close to mother’s






Blood from the fetus passes through the umbilical cord in
the umbilical artery to the placenta
...

transport O2 + nutrients (amino acids, glucose…) from mother --->
fetus
transport CO2 + wastes (urea… ) from fetus --->mother (through
umbilical vein)
...

3
...
Inside the
amnion is a liquid called amniotic fluid
...
Credit: preventdisease
...

Try this

Answer
a) i) A, umbilical cord ; B, vagina
ii) Tree functions from:
- transfers O2 from mother to fetus
- transfers nutrients (of named nutrients) from mother to fetus
- transfers CO2 from fetus to mother
- transfers wastes (or named wastes) from fetus to mother
- allows the transfer of antibodies from mother to fetus
- prevents mixing of the blood of mother and fetus
...


#117 Antenatal care
Ante-natal (before birth) care is a routine care for the healthy pregnant
woman
...
The mother’s diet needs to be balanced so
that’s the fetus receives all the materials needed for healthy growth and
development
...
So her diet should contain plenty of:





amino acids ---> healthy grow and development
calcium ---> development of the skeleton
iron ---> red blood cell formation
energy (carbohydrates/ fats) – help to move mother’s heavier body
...


#118 Process of birth
Birth begins when the strong muscles in the wall of the uterus start
to contract
...

Stages of birth
Stage 1
The muscular walls of the
uterus start to contract,
slowly stretch the opening
of the cervix
...

Contraction gradually
become more frequent,
pushing the baby down
towards the cervix, which become dilated to allow baby to pass through
...


Stage 3

The baby is still attached to the placenta
by the umbilical cord, so this is cut and
tied
...


Try this
Describe, in sequence the main events which occur during birth
...


#119 Sex hormones
Sex hormones (testosterone in
boys and oestrogen in girls) are
responsible for the development
of secondary sexual
characteristics at puberty
...

Secondary sexual characteristics at puberty
Male
Voice becomes much lower (breaks)
Hair start to grow on chest, face,
under arms and in pubic area
Body becomes more muscular
Penis becomes larger
Testers start to produce sperm

Female
Breasts grow, nipples enlarge
Hair develops under arms and in
pubic area
Hip become wider
Uterus and vagina become larger
Ovaries start to release eggs and
period begin (menstruation)

Sites of production of oestrogen and progesterone in the menstrual cycle
and in pregnancy

Hormones
Oestrogen
Progesterone

Site of production
In the menstrual cycle
In pregnancy
Ovaries
Placenta
Corpus luteum (remains of
Placenta
follicle in ovary after ovulation)

Try this

Answer
a) i) Sperm duct labeled correctly between the testes and urethra
...

b) In males the urethra carries urine and semen at different times; in
females the urethra only carries urine
...

ii) Testis (or testes) labeled correctly
...


#120 Method of birth control
There are 4 main groups of birth control methods:
natural, chemical, mechanical and surgical
...
Natural methods

2
...
Mechanical methods

4
...
When
taken on schedule, the pill is highly
effective
...
Like all hormonal
contraceptives, the pill requires a
prescription
...

It comes in the form of foam, jelly,
cream, or film that is placed inside the
vagina before sex
...
It prevents sperm from
entering the woman’s body, protecting
against pregnancy and STDs
...


Female Condom
The female condom is a thin plastic
pouch that lines the vagina and can be
put in place up to 8 hours before sex
...

It's somewhat less effective than the
male condom
...


IUD
IUD stands for intrauterine device, a Tshaped piece of plastic that is placed
inside the uterus by a doctor
...
The hormonal IUD,
Mirena, must be replaced after 5 years
...

Fewer than eight in 1,000 women get
pregnant
...


Vasectomy
Besides condoms, a
vasectomy is the only birth
control option available to
men
...

This prevents the release of
sperm but doesn’t interfere
with ejaculation
...

Even the least effective birth control options
reduce that number considerably
...
webmd
...
For some couples with infertility problems,
insemination can improve the chances of pregnancy
...
The woman can then attend the clinic, and some of the sperms can be
placed into her reproductive tract
...

Concentration is accomplished by selectively choosing highly active, healthy
sperm that are more capable of fertilizing an egg
...

Problems:
- The man has to be able to accept that the child is not biologically his
...
Some people think that the identity of the sperm donor should be given
to the child
...
Many
sperm donors wish to remain anonymous
...
She
is given hormones, including FSH and LH, that cause multiple release of
eggs
...

- If the woman has a problem with blocked oviducts, the eggs are
removed from her ovaries just before they are due to be released, and
placed in a warm liquid in a Petri dish
...
2 or 3 of the
resulting zygotes are placed into her uterus, where they develop in the
usual way
...


IVF
Problems:
- The treatment is quite expensive, and not always successful
...
Other think
that the inability to have children can be so devastating to a couple that they
should receive the treatment free of charge
...


#122 Breast feeding vs formula milk?
This has been a tough question for many years: Which
is better - breast milk or fomula milk? While breast
milk is nutritious, it has its inconveniences
...
What to choose?

Fun fact! Breast milk can naturally and easily remove eye make-up! Plus, it
can cure certain eye diseases!
There are several other things you could do with breast-milk :) Find out
more, just for fun, at:
http://www
...
com/using-breast-milk
...
com
https://www
...
com/watch?v=XPi0odcvegM

#123 HIV/ AIDS - transmission and prevention methods
AIDS (Acquired Immune Deficiency Syndrome) is a
disease caused by the HIV
...
It is an
especially fragile virus - much less tough than the cold
virus
...
You can only become
infected with HIV through direct contact of your body
fluid with those of someone with the virus
...

Lymphocytes produce antibodies ---> attack the antigens on
invading microbes
...

HIV prevents this immunity being retained, so the AIDS sufferer has
no protection against diseases such as tuberculosis (TB) and
pneumonia
...


Video: How is HIV Transmitted?
https://www
...
com/watch?v=z8BwYFlTAGY
Video: How to prevent HIV transmission?
https://www
...
com/watch?v=NXnvP_sKS9k

#124 Gonorrhoea

Gonorrhoea bacteria, Credit: Science photo library

Gonorrhoea is caused by bacteria that can be passed from one person to
another during sexual intercourse
...
It can only survive in moist places, such as tissues lining the tubes in
the productive systems of a man and a woman
...




The first symptoms occurs 2-7 days after infection
...




Woman: the bacteria reproduce mostly in the cervix, although they
can also do so in the vagina ---> many woman do not notice discharge
or suffer a pain as men do
...


Male

Signs and symptoms
- Sores on penis
- Discharge of pus from
penis
- Pain when urinating

Female - Discharge of pus from
vagina, but not always
obvious
- Often no symptoms

Effects
- Damage to urinary
and reproductive
organs
- Sterility
- Blindness in a baby
born to a mother
with the disease
...
g
...

If untreated blindness may result
...
org

#125 Summary of Reproduction
Reproduction is the biological
process by which new "offspring"
individual organisms are produced
from their "parents"
...

Two types of reproduction:
sexual and asexual
...
Bacteria, fungi and potatoes can reproduce
asexually
...
A male gamete fertilises a female gamete, producing a zygote
which is genetically different from its parents
...
During
sexual intercourse, semen containing sperms passes out to the penis
and into a woman’s vagina
...
After
sexual intercourse, sperm swim through the cervix and uterus into
the oviducts, where they may meet an egg
...




The zygote travels to the uterus and implants into the lining,
growing into an embryo attached t the uterus wall via an umbilical
cord and placenta
...




The growing embryo is protected by amniotic fluid produced by the
amnion
...
This
provides it with exactly the correct balance of nutrients, as well as
antibodies which protect it from infectious diseases
...
If it is not
feritlised, the thick lining of the uterus breaks down, in menstruation
...




Birth control helps a couple t avoid having unwanted children
...




Hormones can be used to increase fertility
...


In plants


The flowers are the reproductive organs
...
Female gametes are make
inside ovules produced by ovaries
...




After landing on a suitable stigma, a pollen grain germinates and the
gametes travel down the style to the ovules
...
The zygote develops into an embryo,
and the ovule develops into a seed
...




Fruits are adapted to disperse seeds, using animals or the wind
...




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