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Mother fish lays her eggs on the ocean floor.
After fertilising them, the father fish, like the mother, swims away and leaves the eggs unguarded.
Many of them will never hatch.
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A mother bird lays her eggs in a nest.
The parents will care for the eggs until they've hatched and then they'll care for the new chicks.
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A mother monkey carries a special fertilised egg in the womb, which is inside the lower part of the body.
The egg will eventually become a baby monkey and be raised in the jungle.
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A human mother also carries a special fertilised egg in her womb.
But she and the coming baby will have the help of doctors, scientists and a great deal of the community through the nine months of her pregnancy.
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And that's the subject for today's program, how we start.
From the time we are a single cell to the time when a new infant enters the world.
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Most animals have two parents, a mother and a father. It takes the two of them to form a new life, which we can see when it's born.
But birth is only the point in time where the new animal enters the world.
It begins to form some time before that, when both the mother and the father each contribute to make one new cell.
We're all made up of cells, microscopic building blocks of life.
They make our bones, our muscles, our skin, everything that we're made of.
But it's the combination of two very special cells called gametes, which create a new life.
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The father's gamete is the sperm cell. It's very tiny and it's found by the million within this part of the father's body.
The mother's gamete is the egg cell. It's very large. Usually only one is released at a time and it's found in this part of the mother's body.
If a new life is to be created, one of the sperm cells must enter the center of the egg cell.
This is conception. We say that this new cell formed by the combined gametes is fertile.
It's now able to divide and grow and form a new human being.
But before we let all this joining and dividing and growing take place, let's go back and have a look at what remarkable cells these gametes are.
You can think of them as a sort of half cell in some ways, and yet they both contain such a vast amount of information which determines what the new baby will be like.
The two gametes which form the complete fertilized cell, the father's sperm cell and the mother's egg cell, each contain 23 chromosomes, which we might think of as a library of information.
One of the bits of information in the father's cell decides the baby's sex, whether it's going to be a boy or a girl.
When these two cells combine to form the new fertilized cell, both sets of information are included in it, giving it 46 chromosomes.
The massive amount of information contained in these chromosomes tells us more about the new person than we could ever hope to list here.
What they say about what a person will look like is only a small part of that information.
And soon our fertilized cell begins to grow and divide, and each new cell that is formed is a complete cell, that is it has 46 chromosomes, and all the information in the original cell is passed on.
It's really incredible when you think about it that such a tiny single cell, which is not quite the size of a pinhead, will eventually grow to be a complete human being.
That this, a single fertile human cell, will become this, an individual with a certain kind of hair growing to a certain height and so on.
Now the growth occurs in two ways. First of all by the cells dividing and by the individual cells growing.
For an example, let's have a look at a rabbit.
It too starts with a single fertilized egg cell.
It soon divides into two.
These two divide to make four. And soon there's a large number of cells all joined together.
And this group of cells is called the embryo. And when it reaches a certain stage, the individual cells begin to grow.
And this process of cell division and cell growth continues up until birth and then right up until maturity.
It's very similar with human beings. The tiny long-tailed sperm cell enters the egg cell making it fertile.
Before long it divides into two cells. And then into four and so on it goes.
Then a cavity forms giving the embryo room to grow.
And it doesn't take long for what seems to be a kind of a jumble of cells to become something which we can begin to recognize.
An embryo with its very large blunt head to the bottom right of the yolk sac and the yolk sac used by the embryo to help get its blood supply going.
Soon the yolk sac begins to disappear and we can see the umbilical cord coming from the mother's tissues into what looks like the embryo's tummy.
All this development has taken place in about five weeks. And although the embryo is only half a centimeter long, it won't be very long until the mother senses something and she'll know what to do.
Well, congratulations, Colin. I've had a look at Carol and I'm happy to tell you that you can expect your baby at about Christmas. Everything seems to be going fine and there's no reason why it shouldn't continue so.
There are twins on my side of the family. Is that a possibility with us?
Oh, yes, sure is. About one in sixty twins. And we can't tell yet whether that's going to be so.
Whether it's one or twins, I think we can be very confident that everything's going to be all right. After all, pregnancy has been very well designed.
Carol works all day standing up as a teacher. How soon should she stop that?
Yes, of course she can go on working and she can go on continuing all her ordinary activity like buying tennis. She shouldn't take up any new activity, but just keep on with what she's doing.
And towards the end, of course, she'll need to rest up a bit more.
Would it be possible for Colin to be with me during labour and at the birth?
It's a very good idea. And from my point of view, I'm keen for husbands to be present. Not only because it'll make your job easier, but because it makes my job easier.
There are some very good books you can read. There's also an excellent organisation called the Childbirth Education Association, which has classes for wives and also for expectant husbands.
And together you can go along and see some of their films.
Well, that's about all for today. Before you go, I'll give you a note to go to the laboratory to get some blood tests and also another note to book into the hospital.
As the mother looks forward to the rest of her pregnancy, the embryo starts growing at an incredible rate. At the end of the fifth week, the body starts to take shape.
Cells cluster together to form short arms and legs, and the human body starts to look like a body. But I think one of the most fascinating parts of the development is the development of the face.
At five weeks, the face is not easily recognisable. The features, which are to be the eyes, are off to the side. A deep cleft sits where the mouth will form.
There are gill-like grooves which eventually disappear when the earlobes become visible.
No sign of a nose yet. Really, the only thing that looks familiar is a kind of a forehead.
But watch what happens in the passage of just three weeks.
From this point, the facial development is much slower. But other things are going on at the same time. The embryo starts growing at a much faster rate.
At six weeks, it's about one centimetre long, half the width of a two cent piece, a plumpish little being with short arms and legs.
At eight weeks, it's almost two centimetres long and contains all the main features it will have as a fully grown baby. Only growth and the development of the detail in the body remains.
In fact, scientists now begin to call it a foetus rather than an embryo.
At ten weeks, the toes and fingers are well developed. There are facial expressions. Our foetus can wrinkle up his forehead and even frown.
At twelve weeks, the foetus can react to its foot being tickled, can close its mouth tightly and swallow. It's now about eight centimetres long.
During the next four weeks, the foetus will triple its length, reaching twenty to twenty-five centimetres long, half the birth height.
To grow at this rate, it must take on tremendous amounts of food, oxygen and water. And this must all come from the mother.
She's bound to feel the result and may feel tired. But at the same time, there are things she can do.
I haven't had to slow down too much yet, though some of my friends have. One friend avoids vacuuming as much as she can because she gets backaches.
You have to be careful with your back. There are right ways to go up and down, sit and so on.
There are exercises which help to prepare for the day of childbirth, to be able to relax and bear down in the best way.
I'm supposed to watch what I eat. Lots of protein, fresh fruit and vegetables. Not too many potatoes or too much bread.
What you wear can change a bit too. It's important to be comfortable and so platforms and high heels are out for the moment. They can make it very hard in the back.
It's nice to stop every now and then and think about the baby inside. He's moving around quite a lot now.
I get strong kicks at times, which my husband can feel too by putting his hand on my tummy, and gentle movements as though he's playing the piano down there.
But in some ways it's hard to imagine that there's a human being inside you with a heart, a brain, toes, ears and everything.
Australians are very fortunate in that we have the facilities and the knowledge to make sure that everything goes along smoothly.
But really we're very lucky because things are not so good in many parts of the world.
Let's come back to our foetus, which we left when it was approximately four and a half months old.
It is now five and a half months old, 25 to 28 centimetres tall.
The eyelashes and fingernails begin to grow and a doctor can clearly hear the heartbeat.
Getting into the sixth month, the foetus grows soft downy hair all over the body.
The hands are able to grasp things better than they can during the first few weeks after the baby is born.
The foetus will even react to loud noises outside the womb.
By the seventh month, the foetus is 35 centimetres long and weighs 1.3 kilograms.
Almost half the weight it will be at birth.
The mother will show this increase in size and weight.
In fact, by the time the ninth month is underway, the mother has had to change the way she stands to balance the three kilograms plus of baby
and may be having some difficulty in moving about.
I have two kids already, so even though it's generally more difficult to get around, I still have to cope.
But you can help yourself in little ways.
The towel behind my back makes the driving easier and I get more help from others, of course.
Even the kids pitch in and help carry things.
You find little things that can be annoying.
I never really noticed that my clothes busker was too low until recently.
But I've managed to fix it up so I don't have to bend.
There are some things I just can't do at the moment.
I can't get right down with the boys in the sandpit anymore.
But they seem to understand and adjust quite well to the new situation.
Instead of having me push them on the swing, they now push each other.
I get quite nervous at times, not having the same control over things that I used to.
But generally we're all managing very well. In some ways I'll be glad when it's all over.
And so, nine months after fertilisation, the foetus, now a fully grown baby, is ready to come into the world.
The mother begins to have regular muscular contractions which will push the baby from her body.
She goes to the hospital to have the baby under her doctor's care, just in case.
The check-up is a big favour on the wax卵and is another important nature in infertility.
Are there wind and parts of that that lead to a planning reaction?
They'll have to pick up a couple regional
This is what everything has been leading to.
Our fetus is now a baby and our baby is just starting life outside the womb.
Let's get started.
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