Animal

Survival

Chapter 7:
Reproduction
 Survival of a species

Living organisms eventually die, so in order for a species to

survive it must produce sufficient young to replace those
that are lost through old age, predation and disease.
 Reproduction in fish
(external fertilisation)

The female lays her eggs first and

the male follow depositing his
sperm adjacent to the eggs.

Stickleback

The sperm swim through the

water to the eggs attracted by a
chemical given off by them
Fish Eggs

Yolk

In fish, eggs are protected by flexible coverings and

that the embryos obtain food from enclosed yolk.
Fish produce a large number of eggs because . . .

•The chance of a
•External fertilisation is sperm meeting an egg
inefficient and wasteful is relatively low

•Those eggs that do become

fertilised receive little or no
parental care
 Care of Young

Young fish emerge from the eggs able to look after

themselves without help from there parents.

After its yolk runs out a young fish begins to catch

its own food and develops into an adult fish
External Fertilization

Outside the animals in

the surrounding
environment
(external fertilisation)

An advantage of external
fertilization is that it results
in the production of a large
number of offspring
What are the advantages of external
fertilisation?
Advantages

Lots of eggs being produced and

more offspring

Disadvantages

The eggs and young can be eaten by other animals

They have to find food and protect themselves

 Internal
Inside the female (internal
fertilisation)

An advantage of internal fertilisation

is that the foetus gets all of the
nutrients it needs
What are the advantages of internal
fertilisation?
Protect the baby
Supply of food and
nutrients

Disadvantages

If the mother has any diseases or toxic

substances in her blood it could pass to the
baby
Only have a few offspring at a time
 Mammals produce far fewer eggs because . . .

•There is a greater
chance of sperm cells
fertilising the egg

•Internal fertilisation
is more efficient

•The eggs are well

protected being
inside the mother
Care of young in mammals

At birth, the young of mammals are dependent on the

adult for care and protection.
Number of young
vs. parental care

The more young an animal has the less

parental care is involved e.g. fish.

And the les young produced the more

parental care is involved e.g. mammals
 Sperm Gametes Egg

Produced in Produced the

Testes: Ovaries:
•Small •Large
•Has tail •own food
•No food •No tail

Reproduction
Fertilisation
Number of young vs.
parental care
Fertilisation occurs when
the sperm and egg fuse The fewer offspring the
together combining their greater the parental care
genetic material.
Gametes

Reproduction occurs via gametes or

sex cells.

Female gametes are

called eggs

and male gametes are

called sperm.
 Sperm

Nucleus
Head

Tail

The male produces large amounts of sperm. Sperm is produced in the Testes, it
is small, it has a tail and it doesn’t carry any food
 The Sperm cell

Taill

Why does
it have a
tail?
 The Sperm cell

Explain
how a
sperm
cell is
adapted
for its
function
 Eggs

Females produce a smaller number of eggs. Eggs are produced in the Ovaries.
Eggs are large, they have their own food and the do not have a tail.
What is an ovum?
What is an ovum?
What is an ovum?
Egg Cell
 Reproduction in
mammals
(internal fertilisation)

In mammals and most land animals there is no water

medium for the sperm to swim through so sperm is
deposited into the body of the female
 Sperm duct

Penis

Testis

Reproductive organs of a mammal

Oviduct
Ovary
Uterus
Vagina
Today we will learn about the male
reproductive system
 The male reproductive system

What do we know?
Can you identify anything on the diagram?

O
The male reproductive system
The male reproductive system
The male reproductive system

Label the diagram

 The male reproductive system Part Function
Penis

Urethra

Sperm
duct

Testicles

Gland

Outcomes:

Use key words to label the male reproductive system

Foreskin
Describe the function of each part of the male reproductive system

Explain how the sperm cell is adapted for its function

 What does each part do?
Write down the function of each part on your
diagram. Use the descriptions on the board to
help you.
This skin
These secrete a surrounds the
liquid to add to the testicles.
sperm. The sperm
and liquid together The sperm is
is called semen. produced here
.
This joins to the The sperm travels up
sperm duct. Semen this tube from the
and urine leave the testicles.
penis through this.
Today we will learn about the female
reproductive system
The female reproductive organ
What do we know?
Can you identify anything on the diagram?
The female reproductive organ
The female reproductive organ
Label the diagram of the reproductive organs
What does each part do?
 The female reproductive system Part Function
Ovary

Fallopian
Tube

Womb/
Uterus

Cervix

Outcomes:

Use key words to label the female reproductive system

Vagina

Describe the function of each part of the female reproductive system

Explain how the female egg cell is adapted for its function
 What does each part do?
Write down the function of each part on your
diagram. Use the descriptions on the board to
help you.
This is the tube that the
This holds the foetus in egg travels down to get
place if the egg has to the womb.
been fertilised. It is a Fertilisation usually
muscle that closes the happens here.
top of the vagina.
These release
This is where the the egg cells
fertilised egg would
implant and develop This is a muscular tube
into a foetus. that opens to the
outside of the body.
 Young mammals • Greater chance of
Sperm transmitted from need a lot of sperm meets egg
penis to vagina swims up parental care
uterus into oviducts • Eggs protected inside
mother

Because no water medium for the • Internal fertilisation is

sperm to swim through Copulation more efficient

Internal Produce
Fertilisation fewer eggs
Mammal
Reproduction
Fertilisation Placenta
Reproductive
organs

•Sperm duct •Oviduct The placenta is an organ which

•Ovary allows substances to move
•Penis from the mother’s blood to
•Testis •Uterus
babies’ blood
•Vagina
The fertilised egg passes
down the oviduct and Provides nourishment, gas
becomes attached to the wall exchange and excretion for the
of the uterus. foetus
 Copulation

During copulation the penis is

?
inserted into the vagina.

Sperm is released from the

penis and they swim up the
uterus and into the oviducts

18/09/2019 41
 Fertilization

For a new individual to be formed by sexual reproduction,

fertilisation must occur.

Once the gametes have

fused the new cell is
called a zygote.
What is fertilisation?

When the
sperm and
the egg FUSE
together.
Fertilisation

The fertilised egg passes

down the oviduct and
becomes attached to the
wall of the uterus.

It develops in fluid of
the amniotic sac and
obtains food from the
maternal circulation
(mothers’ blood)
 Sperm and the egg
What do each of these have?
A nucleus which contains the DNA

The nucleus carries

your DNA.
 Where did you get your DNA
from?
You got half of your DNA from your mum and
half from your dad

Who did you inherit you

eye colour from?

Nose shape?

Hair colour?
Which egg is fertilised?
How do you know?
 What is fertilisation?
Draw this diagram in your notes and
explain what is shows.
What is this process called?
½ the amount
of DNA
EGG CELL

½ the amount
of DNA

SPERM CELL
Total amount of
DNA →
ZYGOTE
What happens to the zygote?

After fertilisation the zygote continues to move

down the fallopian tube/oviduct to the uterus
 What is fertilisation?

The fertilised egg (Zygote) Then divides and

copies itself several times. It then becomes
a ball of cells called an embryo.
 What is fertilisation?

Lining of womb/uterus thickens

ready to receive the embryo
 Implantation?

Embryo attaches itself to the uterus

wall. This is called IMPLANTATION.
Today we will learn about Foetal
development and pregnancy
What happens after fertilisation?
What happens after fertilisation?
The zygote (fertilised egg) divides and
copies itself.
This is called an embryo. The embryo
floats towards the uterus/womb.
Embryo implants in the uterus wall
A placenta starts to develop
 The placenta
Blood vessels from the baby form
finger like projections into the
maternal blood supply so that
diffusion can take place

The placenta is an organ of

nourishment, gaseous exchange
and excretion for the foetus
 3-5 weeks
WEEK 3-5 The embryo’s tiny heart begins to beat by
day twenty-one. Arm and leg buds are visible and
the formation of the eyes, lips, and nose has
begun. The spinal cord grows faster than the rest of
the body giving a tail like appearance which
disappears as the embryo continues to grow. The
placenta begins to provide nourishment for the
embryo.
A placenta starts to develop
Week 7
A placenta starts to develop

Major organs
have all begun
to form. The
embryo has
developed its
own blood
type, unique
from the
mother’s. Hair
follicles and
knees and
elbows are
visible.
WEEK 8-12

The embryo is
reactive to its
environment
inside the
amniotic sac
where it
swims and
moves. Hand
s and feet can
be seen.
Weeks 13-16

The brain is fully

developed and
the foetus can
suck, swallow,
and make
irregular
breathing
sounds. Foetus
can feel pain.
Week 20-24

Foetus has a
hand
and footprints
and fingerprints
are
forming. Foetus
practices
breathing by
inhaling
amniotic fluid
into its
developing
lungs.
Weeks 25 – 28

Rapid brain
development
occurs during
this period and
the nervous
system is able
to control some
bodily
functions. The
foetus’ eyelids
now open and
close. At 25
weeks there is
a 60% chance
of survival if
born.
Weeks 29 –
32

There is a
rapid
increase in
the amount
of body fat
the foetus
has. At this
point there
the survival
rate is above
95% if the
baby is born.
 Task-Pregnancy worksheet
Outcomes:
Write the correct statement next to
Identify the key
stages during
the correct picture.
pregnancy
The embryo is now The foetus is 30cm long
Describe how the called a foetus and has and the brain is very
mother and baby human features active. The foetus sleeps
exchanges
substances and wakes at regular
The foetus has defined intervals
fingers and toes and
begins to grow hair, The foetus is 7 cm long
Keywords
Zygote eyelashes and nails and has all body parts are
Embryo
in place
Umbilical cord The foetus is fully
Foetus
Oxygen
developed and ready to be
Carbon dioxide born, it is about 50 cm
Glucose long and about 3.5kg
 Answers

Week 8 The embryo is now called a foetus and has

human features

Week 10 The foetus is 7 cm long and has all body

parts are in place

The foetus has defined fingers and toes

Week 20 and begins to grow hair, eyelashes and
nails

The foetus is 30cm long and the brain is very

Week 30 active. The foetus sleeps and wakes at regular
intervals

Week 40 The foetus is fully developed and ready to be

born, it is about 50 cm long and about 3.5kg
How does the foetus get oxygen?

Any ideas?
The placenta
 Placenta

Oxygen
Water
Vitamins
Drugs (some)
Viruses (almost all)
Carbon dioxide
Nutrients Water
Waste products
 How does the foetus get the
substances it needs?
Agony Aunt

Dear Agony Aunt,

I am pregnant and I am wondering How my baby gets

all the nutrients and oxygen it needs. Also, If I smoke
will it affect the baby?

From Jenny

Task: Write a response to Jenny to explain how

her baby gets the oxygen and nutrients it needs
and gets rid of the waste products. You should
explain if they baby is affected by smoking.
 What about twins?

Identical Non-Identical
 Twins

Identical Non-Identical
Conjoined twins
Conjoined twins

The copied cells do

not separate properly!
They start to develop
individually even
though they are
joined.
 True or false
1. When a zygote divides into a ball of
cells it is called an embryo.

2. Oxygen passes from the foetus to the

mother

3. Nutrients pass to the foetus from the

mothers blood.

4. Smoking will not harm a baby

5. Alcohol and some other drugs will

harm the baby.
Today we will learn about puberty
What makes these changes happen?

HORMONES
chemicals in the body

Male hormone Female hormone

Testosterone Oestrogen
Who is this? What’s
changed?
Hips widen
Pubic (body) hair grows
Voice breaks
Body Odour
Sperm are produced in the
testicles
Eggs are matured in the ovaries
Penis grows/ Breast grow
Shoulders widen
What makes these changes happen?

Girls usually start

puberty first
Males: Females:
Sperm production begins Hips widen
Penis grows Pubic hair
Hair grows Underarm hair
Body odour Breasts grow
Voice breaks Ovaries begin to release eggs
Shoulders widen Body odour
 There are 8 different changes

Male Both Female

Puberty
 Puberty
Draw the table in the your book and fill in the
table with correct changes
menstrual cycle

pubic and under-arm hair

Female changes Common changes Male changes
sweat glands develop

hips widen

sperm produced
sex organs get larger face and body hair
muscles develop
layers of fat
breasts develop

growth spurt

voice deepens

sex hormones circulate

When a girl goes through puberty one of the changes that
occurs is that she will begin to have periods.

This is the female body’s way of preparing to reproduce

A woman’s reproductive system works on a 28 day cycle

This cycle is known as the

menstrual cycle

The menstrual cycle consists of

A number of stages

In this lesson we will learn what

those stages are.....
Day 1 – 7

- Uterus wall breaks

down
- The woman bleeds
through her vagina
- This is a period
Day 7 - 13

- Around day 7 the blood

flow stops.

- Uterus wall builds up

again

- An egg matures in the

ovaries
Day 14 (The Middle)

- On the 14th day, the

egg is released from
the ovary
Day 14 - 17

- Egg travels down the

oviduct
- It can last for around
3 days
- If it meets a sperm in
the duct, it becomes
fertilised
Day 18 - 28

- If the egg is not

fertilised, the uterus
wall breaks down
The cycle starts over again...

Day 1 – 7

- The cycle then

starts over again
- The unfertilised
egg exits the body
with the uterus
lining
Question True/ false Challenge: Why
1. The menstrual cycle lasts for 28
days
2. The uterus wall builds up at the
start of the cycle
3. Eggs are made in the ovaries

4. The ovaries travel down the

oviducts when released and can last
for 3 days
5. If the eggs is fertilised, the uterus
wall breaks down
6. A period is when the cervix breaks
down and bleeds
7. The place where an egg will meet
a sperm is in the oviduct
8. The best time to get pregnant is
between days 14-17