Haileybury IGCSE Biology REPRODUCTION Haileybury IGCSE Biology
Learning objectives Distinguish between somatic cells and gametes Outline the process of fertilisation Compare internal and external fertilisation Draw and label the male and female reproductive systems
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
External fertilisation Suitable for animals that mate in water Many eggs The sperm are able to swim through the water to fertilise the eggs The eggs do not have shells
Internal fertilisation Suitable for animals that mate on land Few eggs The sperm are placed inside the female The eggs have shells
External vs Internal External Internal Where is it used? Soft eggs or eggs with shells? Many or a few eggs example
Reproduction Learning objectives Distinguish between asexual and sexual reproduction and give example of both Draw and label the structure of the human male and female reproductive systems State the functions of the organs of the male and female reproductive systems
ASEXUAL REPRODUCTION Asexual reproduction requires just one parent and does not involve the production of gametes
Can human’s reproduce asexually?
SEXUAL REPRODUCTION Sexual reproduction requires two parents and the production of GAMETES
Male Reproductive System Part Function Penis Placement of sperm into the vagina Testes Production of sperm Seminal vesicles Adds fluid to the sperm Prostate Sperm duct Transports sperm to the urethra Urethra Transports sperm to the end of the penis during (ejaculation) Sperm duct
Male Reproductive System Draw and label the diagram above
Male Reproductive System Part Function Placement of sperm into the vagina Testes Adds fluid to the sperm Prostate Transports sperm to the urethra (during ejaculation) Transports sperm to the end of the penis (during ejaculation) Penis Testis (pl. testes) Sperm duct
Sperm cell
Female reproductive system Oviduct Ovary Part Function Oviduct Transport of the ova and the site of fertilisation Ovaries Where ova are stored and released Cervix The entrance to the uterus Vagina Receives the sperm during sexual intercourse Uterus Also known as the womb – where the foetus develops Ovary
Female Reproductive System Draw and label the diagram above
Female reproductive system Part Function Transport of the ova and the site of fertilisation Ovaries The entrance to the uterus Vagina Also known as the womb – where the foetus develops
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