Kelso High School
Biology
Cell Division
and Reproduction
Name…………………….....
Class………..
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Cell Division and Reproduction
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State that cell division increases the number of cells in a
growing organism or replaces damaged cells in an organism
State that mitosis is another name for cell division
Identify the correct sequence of stages in mitosis
Describe what happens during each of the stages of mitosis
State that mitosis produces two genetically identical daughter
cells
Explain why it is important that the daughter cells contain the
same number of chromosomes as the original cell
Explain the role of gametes in sexual reproduction
State the names and functions of the parts of the male and
female reproductive systems
Explain the differences between internal and external
fertilisation
Describe the events that occur during the fertilisation of an
egg and implantation of the embryo in the uterus
Describe the stages of development in human embryos and
the structures relating to the site of development
Describe the structure of the placenta and how materials are
exchanged between mother and foetus
Discuss some of the possible risks to the development of an
embryo
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Cell division
The nucleus of a cell controls all the cell’s activities, including cell division.
The nucleus contains ___chromosomes______ .
___Chromosomes__________ are made up of genes.
Genes are made of ___DNA_________ .
Genes control the size, shape and function (job)
of the cell.
The process of cell division is also called __mitosis_____
.
Mitosis is the way the number of cells is increased in a
plant or animal. This is how we grow and repair damaged
tissues.
Mitosis
When a cell is about to divide, thread-like structures called ____chromosomes__________
appear in the nucleus. Each new cell (daughter cell) made by mitosis has a complete copy
of the DNA in the original cell i.e. it is ___genetically_____ identical to the original cell.
Since the new daughter cells have exactly the same number of chromosomes, the
cells will function normally. The new daughter cells are _genetically___ identical to the
original cell.
The chromosomes are copied before the cell
divides:
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Label the diagram below to show the structure of a cell that is about to divide:
nuclear membrane
chromosome
centriole
Stages of Mitosis
1.
The __chromosomes__ have duplicated. They start to
become visible in the nucleus.
2.
The nuclear membrane breaks down and the _centrioles_
go to the poles of the cell. The chromosomes are now
visible.
3.
The chromosomes move towards the _equator_ of
the cell. The spindle fibres start to form.
4.
The chromosomes have lined up along the equator and
the _spindle_ fibres__ have attached to their
centromeres.
5.
The spindle fibres contract, separating the chromosomes,
pulling them to opposite _poles_ of the cell.
6.
The __cytoplasm__ starts to divide.
7.
Two _genetically___ identical daughter cells are formed.
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Reproduction
All plants and animals reproduce (produce new offspring). If they did not reproduce, the
species would soon become extinct. Most animals reproduce by sexual reproduction,
involving two parents, each producing specialised cells called gametes.
In animals the males produce gametes called
sperm in the testes and the females produce
eggs (ova) in ovaries. [Plants also produce
gametes called ovules and pollen.]
sperm
egg(ovum)
Male Reproductive System
sperm duct
urethra
testis
penis
Structure
Function
testes
Sperm are produced here
urethra
Tube running down the centre of the penis for transport of sperm
sperm duct
Transports sperm from the testes
penis
Passes sperm from male’s body into female’s body during intercourse
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Female Reproductive System
oviduct
ovary
uterus
vagina
Structure
Function
ovaries
Eggs (ova) are stored and produced here
oviduct
(fallopian tube)
Transports the egg (ovum) towards the uterus
uterus
Fertilised egg becomes implanted and embryo develops here
vagina
Penis enters this tube (which leads to the uterus) and deposits
sperm here
External Fertilisation
Water is required to allow the sperm to swim towards the eggs and fertilise them. Fertilisation
can occur outside the organisms body e.g. in fish, where the eggs and sperm are deposited
in a hollow in the gravel on the bottom of the riverbed or ocean. This is known as external_
__fertilisation__.
Fish must produce many more eggs and sperm than
mammals to overcome the following problems:
• Some eggs may not be _fertilised_
• Some eggs/ young may be eaten by predators
• Some _eggs_/ young may become diseased
and die.
By producing high numbers of gametes, these fish
ensure that at least some of the offspring will survive
to adulthood and have offspring of their own.
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Internal Fertilisation
In mammals (e.g. humans), there is no water for the sperm to swim towards the egg, so the
sperm is deposited __inside__ the female. This is known as internal fertilisation.
Internal fertilisation starts with copulation,
when millions of __sperm__ are released into the
vagina, swim up through the uterus and into
the ___oviduct_where fertilisation takes place,
if an egg is present.
_Fertilisation___ occurs when the nucleus of the
sperm fuses with the nucleus of the egg (ovum).
This results in the formation of a single fertilised egg
cell called a zygote. The __zygote_ is the first cell of a
new organism.
Implantation
This cell will begin to divide by __mitosis__ to create a ball of cells called the embryo. The
embryo moves along the oviduct towards the __uterus__, where it becomes implanted.
sperm
egg (ovum)
lining of
uterus
ovary
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Development of Human Embryo
The embryo (now called the foetus) stays inside the mother’s body during its development,
the mother provides everything the foetus needs to grow and develop via the _placenta_ .
placenta
umbilical
cord
foetus
amniotic
fluid
muscular wall
of uterus
amnion
(amniotic sac)
Structure
Function
amnion
Also known as the amniotic sac. Contains
amniotic fluid.
amniotic fluid
Protects the foetus from bumps and damage,
as the mother moves around.
umbilical cord
Contains blood vessels which deliver food
and oxygen to the foetus and carry carbon
dioxide and urea back to the mother
placenta
Where the mother’s and foetus’ blood come
close together (but do not mix) to allow
materials to be exchanged
foetus
Develops into a baby
uterus
The foetus develops here during pregnancy.
Has a muscular wall that contracts during
labour
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Stages of Development of a Foetus
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Exchange of Materials Across the Placenta
_Food__ and ___oxygen__ pass from the mother’s blood to the embryo.
___Carbon__ __dioxide___ and waste materials (e.g. urea) pass from the __foetus_ to the
mother across the placenta.
Risks to the Foetus during Development
It is now known that as well as food and oxygen, many other substances can cross the
placenta during pregnancy and cause harm to the foetus during development.
Use the information from the class presentations to complete the table below, to show the
risks that can occur during development of the foetus:
Risk
Drinking
alcohol
Smoking
Problem caused during
development
•
•
•
Effect on development of foetus
Drinking excessive quantities of
__alcohol__ during pregnancy
can cause the blood vessels in
the umbilical cord to collapse,
preventing ___food__ and
__oxygen__ reaching the foetus
•
•
Lower the amount of oxygen
available to the mother and baby.
Increase the baby's __heart___
rate.
•
•
•
•
Increased chance of _miscarriage__
If a mother drinks heavily during
pregnancy, the baby could develop a
group of problems known as _Foetal__
__Alcohol__ _Syndrome_ (FAS).
Children with this syndrome have:
¾ restricted growth
¾ facial abnormalities
¾ learning and _behavioural__
disorders
Increase the chances of miscarriage
and stillbirth.
Increase the risk that the baby is born
prematurely and/or born with a _low__
birth weight.
Increase the baby's risk of developing
respiratory ( lung) problems
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Use the table below to note any further relevant risks to the development of the foetus that
were discussed during the class presentations:
Other Risks
Problem caused during
development
Effect on development of foetus
As appropriate from class discussion
Methods of Contraception
Complete the table below to show some of the methods of contraception you have
researched and there effectiveness: (data used for this table is taken from NHS website:
http://www.nhs.uk/chq/Pages/825.aspx?CategoryID=117&SubCategoryID=114, Feb
2013)
Method of Contraception
Effectiveness
Male condoms
98% if used correctly
Female condoms
95% if used correctly
Combined contraceptive pill
99% if taken correctly
Contraceptive implants/ injections
99%
Female sterilisation
99%
[End of topic]
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