Life processes in living organism part 2

It is for std 10 science and technology part 2 chapter 3 and covers sexual and asexual reproduction in plants and animals

1. LIFE PROCESSES IN LIVING ORGANISM PART - 2 Reproduction: Asexual and Sexual reproduction Reproduction and modern technology Reproductive health Population explosion

2. Asexual reproduction

3. Asexual reproduction Formation of a new individual from a single parent without fusion of an egg and a sperm No specialized sex cells involved Offspring is genetically identical to the parent

4. Asexual reproduction in unicellular organism 1. Binary Fission 2. Multiple Fission 3. Budding

5. 1. Binary Fission Prokaryotes (Bacteria) , Protists(Amoeba, Paramoecium, Euglena etc.) and eukaryotic cell organelle like mitochondria and chloroplast perform asexual reproduction by binary fission Parent cell divides to form two similar daughter cells. Binary fission occurs either by mitosis or amitosis Binary fission is performed in favorable condition i.e. availability of abundant food material Axis of fission is different in different protist

6. Axis of fission Simple binary fission : Amoeba divides in any plane due to lack of specific shape hence called as simple binary fission

7. Transverse binary fission

8. Longitudinal binary fission

9. 2. Multiple Fission It is performed by amoeba and similar protists. In adverse/unfavorable condition , amoeba stops the formation of pseudopodia and thereby movements. It becomes rounded and forms protective covering around plasma membrane. This is called as a “ Cyst ” Many nuclei are formed by repeated nuclear divisions in the cyst. Then cytoplasmic division takes place and thus many amoebulae are formed They remain encysted till unfavorable condition. During favorable condition the cyst breaks open and many amoebulae are released

10. 3. Budding An outgrowth (bud) from a parent cell, later detached from the parent & is released as an independent individual Eg Cnidarian like Hydra, Obelia, Saccharomyces ( yeast) Yeast cell produces two daughter cell by mitotic division

11. Asexual Reproduction in Multicellular Organism 1. Fragmentation 2. Regeneration 3. Budding 4. Vegetative Propagation 5. Spore Formation

12. 1. Fragmentation The body of the parent organism breaks up into many fragments Each fragments starts to live as an individual new organism Eg. Algae like spirogyra and sponges like sycon

13. 2. Regeneration Planaria breaks up its body into two parts and then each part regenerates remaining part of the body and thus two new planaria are formed. Wall lizard breaks up and discards some part of its tail in emergency. Discarded part is regenerated after a period

14. 3. Budding In Hydra, under favorable conditions, at specific part of its body an outgrowth is formed by repeated division of regenerative cells of body wall. This outgrowth is called as bud. The bud grows and finally forms a small hydra Dermal layers and digestive cavity of the budding hydra are in continuity with those of the parent hydra. Parent hydra supplies nutrition to the budding hydra. The budding hydra seperates from the parent hydra and leads an independent life

15. 4. Vegetative Propagation Reproduction in plants with the help of vegetative parts like root, stem, leaf and bud. In potatoes it is performed with the help of “eyes” present on the tuber. In Bryophyllum it is performed with the help of bud present on the leaf margin In sugarcane and grasses it occurs with the help of buds present on the nodes Plants like carrot and raddish perform vegetative propagation with the help of roots.

16. 5. Spore Formation Fungi like Mucor have filamentous body They have sporangia Once the spores are formed , sporangia burst and spores are released Spores germinate in moist and warm places and new fungal colony is formed

17. SEXUAL REPRODUCTION It occurs with the help of two germ cells i.e. male gamete and the female gamete Two main processes occur in sexual reproduction 1. Gamete formation : Gametes are formed by meiosis thereby chromosomes number are reduced to half i.e. haploid gametes are formed Fertilization: A diploid zygote is formed by the union of haploid male and female gamete. This zygote divides mitotically and embryo is formed. This embryo develops to form a new individual. Due to fusion of male and female gametes the new individual has recombined genes of both the parents therefore shows similarities with both the parents Diversity in organism occurs due to genetic variation which helps them to adjust to the changing environment and help to save themselves from extinction

18. SEXUAL RERODUCTION IN PLANTS A flower is the structural unit of sexual reproduction in plants It has four whorls i.e. calyx, corolla, androecium, gynoecium arranged in sequence from inside to outside Androecium and gynoecium are called as the essential whorls as they carry out the process of reproduction Calyx and corolla are called as the accessory whorls as they are responsible for the protection of inner whorls Members of the calyx are called as sepals Members of corolla are called as petals A flower is called bisexual if both androecium and gynoecium are present in the same flower eg. Hibiscus flower A flower with only androecium is called a male flower A flower with only gynoecium is called a female flower eg. papaya

19. Pollination and Fertilization

20. Sexual reproduction in human being Human male reproductive system

21. Human female reproductive system

22. Reproduction and modern technology Many couples cannot have children due to many reasons but due to advance medical technique it is now possible for the childless couple to have a child Some of these techniques are : In Vitro Fertilization (IVF) Surrogacy Sperm Bank/ semen Bank

23. Twins Two embryos develop simultaneously in the same uterus and thus two offspring are delivered . There a two main types of twins i.e. monozygotic twins and dizygotic twins In monozygotic twins, during early period of development the cells of the embryo divides into two groups Such twins are genetically exactly similar in appearance and their gender is also same If the embryonic cells are divided into two groups 8 days after the zygote formation then there is high risk of formation of conjoined twins

24. Dizygotic twins When two oocytes are released from the ovary of the women and they are fertilized by two separate sperm and thus two zygotes are formed Two embryos are formed from two zygotes and the both the embryo are separately implanted in the uterus. Thus dizygotic twins are delivered after complete development Such twins are genetically different and may be of same or different gender