C astlehead H igh S chool Factors affecting variety in a species – Reproduction in Mammals and Plants Intermediate 2 Environmental Biology & Genetics

C astlehead H igh S chool Sexual Reproduction A species is when two organisms are able to interbreed and produce fertile offspring Sexual reproduction is the production of new members of a species using sex cells ( gametes ) Fertilisation is the fusion of two gametes to form a new organism

C astlehead H igh S chool Male Reproductive System Penis Testes Sperm duct Urethra Gametes in male mammals are sperm - produced in the testes

C astlehead H igh S chool Female Reproductive System Uterus Vagina Oviduct Ovary Cervix Gametes in female mammals are eggs - produced in the ovaries

C astlehead H igh S chool Fertilisation in mammals The release of an egg from the ovaries is called ovulation Following sexual intercourse sperm swim towards the egg as it is wafted along the oviduct If a sperm meets the egg in the oviduct fertilisation occurs, the nucleus of the sperm and egg fuse and a zygote is formed

C astlehead H igh S chool Fertilisation in mammals During fertilisation one set of chromosomes from the sperm fuses with another set from the egg to form a zygote with 2 sets of 23 chromosomes - 46 in total Sexual reproduction gives the opportunity for genetic material from two different individuals to meet

C astlehead H igh S chool Gamete production in flowering plants Gametes in a flowering plant are: Male – pollen, formed in anthers Female – ovules, formed in ovaries Stigma Style Ovary Anther Ovule Petal

C astlehead H igh S chool Fertilisation – Pollination the transfer of pollen from anther to stigma A pollen grain lands on the STIGMA. A POLLEN TUBE grows down the STYLE towards the OVARY. The MALE NUCLEUS travels down the pollen tube. Where it joins with the OVUM NUCLEUS in the OVARY. This is called FERTILISATION. From this fertilised ovum called a ZYGOTE a SEED will grow. Pollen Stigma Pollen tube Style Ovary Ovum

C astlehead H igh S chool More to do Click on the link Listen and watch lessons 18, 19, 22 and 23 on the female and male reproductive system, sexual intercourse and fertilisation.