9 class SexualRepro and Plants.ppt
- Количество слайдов: 15
Sexual reproduction is the production of new offsprings from two parents. Sexual reproduction is the combination of one set of genetic material from two organisms of the same species, but opposite sex, resulting in a new organism with new gene combination.
GAMETES • Sexual reproduction occurs by means of gametes. • They are produced in reproductive organs by means of meiotic cell division Gametes have n number of chromosome.
• Organs which produce gametes are called Gonads. • Male gonad is called testes that produce sperm. § Female Gonad is called ovary that produce egg.
Production of Gametes § Production of male or female gametes are called Gametogenesis. § Especially production of sperm is called Spermatogenesis. § Production of egg is called oogenesis.
FERTILIZATION § The union of egg and sperm is called FERTILIZATION. § The cell that is formed from union of an egg and sperm is called ZYGOTE. § Gametes have n number of chromosome and zygote has 2 n number of chromosome.
Steps of Sexual Reproduction testis ovary Meiosis sperms Meiosis fertilization zygote embryo foetus baby eggs (ova)
• Trаnsfer of pollen from anther to stigma is called pollination. • Pollination occurs by means of wind, water, insects and other animals
After pollination; § A pollen tube grows down through the stigma and stylus into the ovary. § The tube nucleus controls the formation of pollen tube. § Then pollen tube enters the ovule through the microphyle § The tube nucleus and generative nucleus pass from pollen grain to
FERTILIZATION § The generative nucleus is divided into two sperm nuclei in the pollen tube. § 2 Sperm nuclei enter the embryo sac. § One sperm fertilizes to egg cell to form ZYGOTE. § Other sperm fuses with pollar nüclei to form triploid (3 n) ENDOSPERM. § This type of fertilization is called Double Fertilization.
SEED AND FRUITS § After the fertilization, each ovule develops to seed. § The ovary develops to fruit.