3.19b)

3.19a)

3.18a) and b)

Genetics

3.2- Fertilisation

Understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo

• The cells in testis and in ovaries have a complete cell of chromosomes and this is called diploid (2n) which is a complete set of chromosomes and for human it is 46
• The cells divide to form cells with half sets of chromosomes, this type of cell division is called meiosis this makes the cell go from a diploid number to a haploid number(n) which is a 1/2 set so in humans it is 23
• During sexual reproduction the two cells are brought together and joined together, so it forms just 1 cell. This process is know as fertilization and it involves the combining of half set of chromosomes and another half set of chromosomes to make a full set of chromosomes (23+23=46)
• This cell is known as a Zygote
• This cell goes through Mitosis in which the cells divide but they all contain 46 chromosomes
• It will be called an embryo when we have sufficient amount of cells

3.9- Reproductive systems

Recall the structure and the function of the male and female reproductive systems


Male reproductive system:

• Bladder
• Stores urine
• Testis 
• Carries out Meiosis which produces the male gamete, sperm cell
• Epididymis
• Store sperm cells
• Vas Deferens 
• Carries sperm cells to the penis
• Prostate
• 20-30% of the volume of the semen, contains sugars. Alkaline solution, to neutralise the acidic secretions within the vagina
• Seminal Vesicals
• Produces 70% of the semen; sugar based and alkaline
• Urethra
• Common tube that joins the left and right Vas deferens, transports semen and urine down the penis
• Penis 
• Carry sperm cells into vagina

Female reproductive system:

• Ovary
• Meiosis occurs to form the female gamete. the egg cell
• Oviduct
• Carry the eggs to the uterus, fertilisation occurs here
• Uterus wall
• the wall of the uterus, made of muscle and stretches to accomadate a pregnancy
• Uterus lining
• accepts and develops the fertilised egg into an embryo and then into a child, the placenta implants into here
• Uterus space
• Where the embryo is developed into an unborn child
• Cervix
• Entrance to uterus
• Vagina
• Collects the sperm from the penis and allows them to pass through the cervix and into the uterus

Before pregnancy the entire uterus structure is no larger than an orange.

3.12- Amniotic fluid

Understand how the developing embryo is protected by the amniotic fluid

• Amniotic fluid surrounds the embryo in the uterus
• The fluid acts protects the embryo as it is mostly water and can't be compressed
• The fluid absorbs the shock of any blow to the outside of the uterus

3.11- Placenta

Describe the role of the placenta in the nutrition of the developing embryo 

• When the child is in the uterus, it is surrounded by amniotic fluid.
• It cannot digest, breath or excrete so it gets it's nutrients from the mother through the placenta. 
• The placenta consists of the the umbilical cord containing the embryo's blood vessels. 
• The placenta grows out of the embryo
• It grows into the wall of the uterus
• Glucose, Amino acids and fats travel through the mother's blood vessel
• These will cross into the child's blood at the placenta
• The placenta has a large surface area and the barrier is really thin to make this process efficient
• Carbon Dioxide and Urea are exchanged back into the maternal blood

Mitosis

Mitosis animations:

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html
• http://cellsalive.com/mitosis.htm

Stages of Mitosis: