Haileybury IGCSE Biology REPRODUCTION Haileybury IGCSE Biology

Somatic Cells Most of the cells in our bodies are SOMATIC cells They contain two sets of chromosomes We describe it as being DIPLOID One set from each parent Our cells contain 46 chromosomes 23 from each parent

Gametes Sex cells are called gametes They contain one set of chromosome Our gametes contain 23 chromosomes They will be a mixture of chromosomes from each parent

Gametes Male Female Plants Animals Pollen Ova Sperm Ovum

Fertilisation gamete gamete Somatic cell Gametes are produced by meiosis Meiosis is a type of cell division that halves the chromosome number Fertilisation is a fusion of gametes This restores the chromosome number

Flower Structure

Copy the drawing and complete the table

Pollination

Pollination Pollination is the transfer of pollen from the STAMEN of one flower to the STIGMA of another.

Male Reproductive System Parts not labelled on the diagram Part Function Cowper’s gland Releases fluids prior to ejaculation Epididymis Stores the sperm Erectile tissue Fills with blood during an erection The testicle is better labelled as testis pl. testes. The plural of vas deferens is vasa deferentia. (vas deferens)

Male Reproductive System Draw and label the diagram above

Sperm cell

Female reproductive system Parts not labelled on the diagram Part Function Fallopian tubes Transport of the ova and the site of fertilisation Ovaries Where ova are stored and released Cervix The entrance to the uterus

Female Reproductive System Draw and label the diagram above

Ovum

Sexual Intercourse The biological purpose of sexual intercourse is to place the sperm as close as possible to the ovum to optimise the chance of fertilisation. The ovum is wafted down the fallopian tubes (oviducts) by small hairs called cilia. The sperm have to swim through the cervix, uterus and part of the way up the fallopian tubes. Only a very small proportion of the sperm will reach the ovum. Barrier methods of contraception such as condoms prevent the sperm from reaching the ovum

Fertilisation The membrane of the head of the sperm fuses with that of the ovum. Changes to the zona pallucida prevents the entry of another sperm. The male nucleus containing 23 chromosomes fuses with the female nucleus which also contains 23 chromosomes. The fertilised ovum is now called a zygote and it contains 46 chromosomes. Half the sperm contain a Y chromosome, resulting in a boy and the other half contain an X chromosome resulting in a girl.

Fertilisation to Implantation

Questions Where does fertilisation occur? Define the following words: Zygote Blastocyst Fertilisation How does the ball of cells travel towards the nucleus? Why is it important that it does not take any longer for the blastocyst to implant in the wall of the nucleus?

Hormonal control of the menstrual cycle FSH causes the ripening of (usually one) Graafian follicle. The follicle produces oestrogen that thickens the lining of the uterus. LH release results in ovulation and production of the corpus luteum. The corpus luteum produces progesterone that maintains the uterine wall. FSH and LH are used in fertility treatment. Oestrogen and progesterone are used in the contraceptive pill.

Hormonal control of the menstrual cycle ____ causes the ripening of (usually one) Graafian follicle. The follicle produces ______ that thickens the lining of the uterus. _____ release results in ovulation and production of the corpus luteum. The corpus luteum produces ________ that maintains the uterine wall. FSH and LH are used in _____ treatment. Oestrogen and progesterone are used in the ________ pill. Progesterone LH Contraceptive Fertility Oestrogen FSH

Placenta & Amnion

Learning Objectives State the functions of the amnion Outline the functions of the placenta

Amnion The amnion is a membrane surrounding the foetus. It contains the amniotic fluid. It provides a moist environment and protection from bumps. It ruptures at the onset of birth and the amniotic fluid is released.

The placenta Produces the hormone HCG that leads to morning sickness. Produces Progesterone that maintains the uterine wall. Provides nutrients and oxygen. Removed urea and carbon dioxide. Maternal and foetal blood come close together but do not mix

A closer look…. Chorionic villi increase the surface area for the exchange of substances. Substances pass across the placenta by diffusion. The placental membrane acts as a barrier to pathogens (disease). Antibodies do not pass across the membrane so the first milk or colostrum is important. Alcohol and drugs can pass across the placental membrane

Video clip – An Everyday Miracle A quick look at the placenta! Then: Cambridge IGCSE Combined and Coordinated Sciences page 143 Questions 2&3. You are required to draw any diagrams!