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SEXUAL REPRODUCTION bankofbiology.com themselves. | ‘a nT ws FEZ E ll SEXUAL REPRODUCTION Some plants exhibit unusual flowering. E.g. “» Bamboo species flower only once in their lifetime (after 50-100 years), produce large number of fruits and die. “ Strobilanthus kunthiana flowers once in 12 years. “gh-Strobilanthus kunthiana fléwers bankofbiology.com SEXUAL REPRODUCTION SEXUAL REPRODUC Based on breeding season, mammals are Z types: > Seasonal breeders: The mammals (living in natural conditions) exhibiting reproductive cycles only juring favourable seasons. * Continuous breeders: They are reproductively active throughout their reproductive phase. ¢p) j Pre- fertilisation Events/ Stages in sexual reproduction Post- fertilisation bankofbiology.com 1. PRE-FERTILIZATION EVENTS \ \/ ’ | SFR, \ a | - Homogametes (isogametes); fe SY * Heterogametes SEXUA AL REPRODUCTI JON 1. PRE-FERTILIZATION EVENTS | Sexuality (bisexual or unisexual) in organisms Clitetium Unisexual Male and female reproductive structures are present on different individuals. * If male and female flowers are present on papaya & date palm. | * Unisexual : E.g. Cockroach, higher © e animals etc. (a) Bisexual animal (Earthworm) Ss a eerie ee _ ’ ‘Stamen, (b) Unisexual animal (Cockroach) A Fungi may pe homothallic (bisexual) or (c) Monoecious plant (Chara) Wererothc - (unisexual) i (d) Dioecious plant (Marchantia) netert othallic (unisexual). | w (e) Bisexual flower (sweet potato) SEXUAL RE EPRODUCTION ] 1. PRE-FERTILIZATION EVE Cell division dur ing | gamete fe Name of Chromosome number formation O} ree nism In meiocytes (2n) In gametes (n) Human being 46 23 ’ Housefly 12 6 * Many monerans, fungi, algae & Rat 42 Pal bryophytes have haploid parental Dog 78 39 body. They produce haploid gametes Cat 38 19 by mitosis, Fruit fly 8 4 _— ee Ophioglossum 1260 630 * Pteridophytes, gymnosperms, Apple 34 7 angiosperms & animals have diploid Rice 2A 12 parental body. They produce haploid = maize 20 10 gametes by meiosis of meiocytes Potato 48 24 (gamete mother cell). Butterfly 380 190 i J Onion 16 8 bankofbiology.com 1. PRE-FERTILIZATION EVENTS pollen grains id ovule carries the eg SEXUAL REPRODUCT| ION » 1. PRE-FERTILIZATION | b. Gamete Transfer * In bisexual self-fertilizing plants (e.g. peas), | anthers & stigma are close to each other. So transfer of pollen grains is easy. * Incross pollinating plants (including dioecious plants), pollination helps in transfer of p ae | grains. Pollen grains germinate on the stigma and the pollen tubes carrying male gametes reach the ovule and discharge male gametes near the egg. * In dioecious animals, the fertilisation helps for successful transfer and coming together of gametes. Cross pollination 
