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Reproduction in Organisms Explained
- 1. REPRODUTION IN ORGANISMS (CRASH COURSE) NCERT Class 12 Biology ADHILA K.A MSc. Microbiology
- 2. Life Span : Period from birth to natural death of an organism is said to be its life span. Only single celled organisms are immortal
- 3. REPRODUCTION (Process of formation of young ones from an organism) SEXUAL REPRODUCTION ASEXUAL REPRODUCTION Two parents of opposite sex Single parent
- 4. ASEXUAL REPRODUCTION Modes of Asexual Reproduction : •Protist , Monera •Parent cell – Mitosis – 2 new individuals CELL DIVISION •Amoeba , Paramecium •Plant cell 2halves Each half grows into adult BINARY FISSION •Yeast •Small buds are form in parent cell separated grow and mature into adult BUD FORMATION •Plants •Vegetative propagules : RUNNER, RHIZOME, SUCKER, TUBER, OFFSET,BULB VEGETATIVE PROPAGATION •Hydra •Parent body Break into fragments each fragment grow into adult FRAGMENTATION Clone Offsprings in asexual reproduction are genetically and morphologically similar to each other and to their parents. Such genetically and morphologically similar individuals are known as clone.
- 6. ASEXUAL REPRODUCTIVE STRUCTURES IN FUNGI & SIMPLE PLANTS LIKE ALGAE ZOOSPORES: Common, Microscopic motile CONIDIA: Penicillium BUDS: Hydra Gemmules: Sponge
- 7. SEXUAL REPRODUCTION NEW ORGANISM ZYGOTE FUSION OF GAMETES Offsprings are not identical to each other & to parents
- 8. PHASES OF LIFE • Period of growth • In plants known as vegetative phase JUVENILE PHASE • Reproductively active (Attain maturity) • In plants: Flower • In animals: Morphological & physiological changes (Controlled by hormones and environmental factors) REPRODUCTIVE PHASE • End of reproductive phase leads to old age • Slow down metabolism • Leads to death OLD AGE / SENESCENCE Females of placental mammals in reproductive phase shows cyclical changes in their reproductive system: OESTRUS CYCLE MENSTRAUL CYCLE Non primate mammals: Cow, Sheep, Rat etc. Primate mammals: Human, Apes, Monkey SEASONAL BREEDERS CONTINOUS BREEDERS MAMMALS Reproductively active in certain seasons during reproductive phase Reproductively active throughout the reproductive phase Transition between phases of life is controlled by HORMONES
- 9. EVENTS IN SEXUAL REPRODUCTION PRE - FERTILIZATION FERTILIZATION POST - FERTILIZATION • Gametogenesis • Gamete Transfer • Fusion of Gametes • Zygote • Embryogenesis
- 10. PRE - FERTILIZATION GAMETOGENESIS: Formation of male & female gametes Gametes are HAPLOID GAMETES HOMOGAMETES HETEROGAMETES • Both gametes are similar in appearance. • Can’t distinguish between male and female gametes • E.g. Cladophora • Both gametes are morphologically distinct. • Can distinguish between male and female gametes. • Male gamete : ANTHEROZOID/SPERM • Female gamete : EGG/OVUM • E.g. Fucus (An algae) PLANTS UNISEXUAL/DIECIOUS/ HETEROTHALLIC • Male & Female reproductive structures are in different plants. • Male flower: Staminate • Female flower: Pistilate • E.g. Date palm & Papaya BISEXUAL/MONECIOUS /HOMOTHALLIC • Male & Female reproductive structures are in same plant. • E.g. Cucurbits & Coconut
- 11. ANIMALS UNISEXUAL • Cockroach • Human BISEXUAL/HERMAPHRODITES • Sponge • Earthworm • Tapeworm • Leech GAMETE FORMATION HAPLOID ORGANISMS DIPLOID ORGANISMS Mitosis Monera Fungi Algae Bryophite Meosis Pteridophyte Gymnosperm Angiosperm Gamete mother cell : Meocyte
- 12. Gamete transfer Male Gamete • Motile Female Gamete • Non - motile Exception Few fungi & Algae: Both Gametes are motile ANTHER of male flower STIGMA of female flower Male gametes carried by POLLEN GRAINS POLLINATION OVULE of female flower Male gamete carried by POLLEN TUBE Pollen grains germinate Male gametes released near to the eggs GAMETE TRANSFER IN UNISEXUAL PLANTS: KNOWN AS CROSS FERTILIZING PLANTS GAMETE TRANSFER IN BISEXUAL PLANTS: KNOWN AS SELF FERTILIZING PLANTS GAMETE TRANSFER IN ALGAE, BRYOPHYTE, PTERIDOPHYTE: THROUGH WATER
- 13. POST – FERTILIZATION EVENTS ZYGOTE - DIPLOID External fertilization: Zygote formation is outside the body Internal fertilization: Zygote formation is inside the body Further development of zygote Fungi & Algae • Zygote – Cover with a thick wall (to protect from dessication & damage – period of rest – germinate Haploid organisms • Zygote – divide by meosis – Haploid spores – new organisms Vital link that ensure continuity of species between organisms of one generation to the next
- 14. FERTILIZATION / SYNGAMY FUSION OF GAMETES Results in the formation of ZYGOTE PARTHENOGENESIS • Female gamete develop without fertilization • Rotifers • Honey bees • Some lizards • Some birds (Turkey) FERTILIZATION EXTERNAL FERTILIZATION INTERNAL FERTILIZATION • Fertilization occur in external medium (water). • Aquatic organisms: algae, fish, amphibians • Large number of offsprings. • Offsprings are vulnerable to predators. So, difficult to survive until adulthood. • Fertilization occur inside the body • Terrestrial organisms: Fungi, mammals, reptiles, most birds & plants • Motile male gamete – fuse with female gamete inside the female body • Large no. of male gametes ; Less no. of female gametes; Less no. of offsprings
- 15. Embryogenesis NEW ORGANISM MITOSIS & CELL DIFFERENTIATION MITOSIS: Increase number of cells CELL DIFFERENTIATION: Cells undergo modifications to form specialized tissues & organs to form an organisms ZYGOTE
- 16. ANIMALS OVIPAROUS VIVIPAROUS Fertilized egg Cover with hard calcareous shell lay in safe place in environment period of incubation young ones hatch out e.g. Reptiles, Birds Zygote develop into young one inside body Certain stage of growth Delivered out e.g. Mammals Chances of survival is more FLOWERING PLANTS Zygote formed inside ovule Sepals, Petals, Stamens wither & fall off Pistil reamin attached ZYGOTE develop into EMBRYO OVULE develop into SEED OVARY develop into FRUIT Pericarp – Thick wall – Protection Seeds germinate under favourable condition New plants
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