Reproduction

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this is a self created file about reproduction and growth..form 5 chapter 4..please feel free to take note

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Reproduction

  1. 1. REPRODUCTION & GROWTH GROUP MEMBERS:1)Sasivarnen 2)Aravinth 3)Mailan 4) Vijay 5)Devindran
  2. 2.  There are two types of reproduction: sexual reproduction and asexual reproduction.  Sexual reproduction is the creation off offspring through the fusion of haploid gametes to form a diploid zygote(fertilised egg).  Asexual reproduction is the reproductive process in which new individuals are produced without the formation of gametes.  Asexual reproduction does not involve the fusion of haploid gamete.
  3. 3. SEXUAL REPRODUCTION ASEXUAL REPRODUCTION The production of new individuals involving sex cells or gametes The production of new individuals without involving sex cells Gametes are formed by meiotic division. The process relies entirely on mitotic division. New individuals inherit genes from both parents through the fusion of the egg and sperm New individuals get their genes from one parent without the fusion of an egg and sperm Present in humans,other mammals,birds,reptiles,amphibians,fish and flowering plants Present in simple organisms like the amoeba,paramecium,hydra,yeast and plants such as mosses and potatoes. Produces offspring that are genetically different from their parents Ensures the survival of the species if the environmental conditions undergo changes constantly Produces offspring that are genetically identical to the parent Ensures that the adaptations of the parent for survival are passed down unchanged to the offspring Is an advantage if the environment is stable
  4. 4. 1. In humans,the male gametes called sperms (spermatozoa) are produced in the male reproductive organs called testes. 2. The female gametes or ova are produced in the female reproductive organs known as ovaries. 3. These two types of gametes are produced through the process of meiosis.The gametes are genetically different from the parent cell 4. During fertilisation,a sperm fuses with an ovum to form a zygote. 5. As the sperm and ovum have haploid number of chromosomes (n=23) each,the zygote formed will have a diploid number of chromosomes (2n=46). 6. During mitosis,the zygote divides mitotically to produce millions of cell,each cell having 46 chromosomes.
  5. 5. The male reproductive system consists of: • Gonads that produce male gametes(sperm cells) and sex hormones. • Accessory glands that secrete fluids essential to sperm movement • Ducts that carry the sperms and secretions • The male reproductivestructures include the testes,scrotum,epididymis,vas deferens (sperm ducts) and penis. • The male reproductive system also includes the seminal vesicles and the prostate gland. • The male gonads (testes) produce both sperms and male sex hormones.It is enclosed in an external sac called the scrotum.The scrotum houses the testes outside the body cavity.Outside the body,the temperature of the testes is about 2-3°C lower than the normal body temperature thus it becomes ideal for sperm to develop. • Each testis has about one thousand seminiferous tubules.These are fine,long coiled tubes arranged compactly.
  6. 6. • The tubules merge to form a tightly coiled tube called the epididymis.The epididymis lies just outside the testes. • Sperms are formed in the seminiferous tubules and mature within the epididymis.The epididymis is connected to the vas deferens or sperm duct which also stores the sperms.The vas deferens leaves the scrotum and enters the abdominal cavity. • The two sperm duct join the urethra which connects the bladder to the penis.The sperm pass from the seminiferous tubules through the epididymis and vas deferens into the urethra.The urethra is the exit route for both sperm and urine. • Accessory gland add secretions for the transport and survival of the sperm:
  7. 7. I. The seminal vesicle secrete thick,clear fluid containing nutrients for the sperm. II. The prostate gland secretes a milky white fluid that activates or increases the mobility of the sperm.The sperm and the secretions from the accessory glands make up the semen.
  8. 8. • Spermatogenesis (spermatozoa formation) takes place in the densly coiled seminiferous tubules. • Two types of cells,the germinal epithelial cells and Sertoli cells,line the seminiferous tubules. • The Sperm cell consists of head,midpiece and a tail.The head contains a large nucleus and a specialised lysosome called the acrosome. • The acrosome contains hydrolytic enzymes that help to digest the protective layers surrounding an ovum an help it to penetrate it during fertilisation. • The midpiece contains a large number of mitochondria which helps to provide energy needed for the movement of the tail.
  9. 9. A section of testis showing the seminiferous tubules,epididymis and vas deferens.
  10. 10. 1)Geminal epithelial cells of a seminiferous tubule divide by mitosis to produce diploid spermatogonia 2)The spermatogonia grow to become primary spermatocytes which are large diploid cells. 3)Each primary spermatocyte undergoes meiosis I to form two haploid secondary spermatocytes. 4)Each secondary spermatocyte divides again during meiosis II to produce two spermatids.This means a total four spermatids are formed for each primary spermatocyte. 5)The spermatids obtain nourishment from nearby nutritive cells (Sertoli cells),develop tails and mature into spermas (spermatozoa) through cell differentiation.
  11. 11. • The female reproductive system consists of a pair of ovaries,the Fallopian tubes (oviducts),uterus,cervix,vagina and the external genital organs which are collectively called the vulva. • The female gonads or the ovaries produce female gametes (ova) and secrete female sex hormones :,oestrogen and progesterone • The Fallopian tubes extend from the ovaries to the uterus.They have finger-like projections called fimbriae which surround the ovaries.The combined action of the fimbriae and the beating of cilia that line the oviducts create a beating of cilia that line the oviducts create a current that sweeps the ovum along. • The uterus is a thick-walled,muscular organ that houses the developing embryo and foetus.
  12. 12. • The ovum in females is produced through oogenesis.. What is Oogenesis??  Oogenesis is the formation of ovum or egg,starts in the ovary of the female foetus before birth. How it occurs??  The germinal epithelial cells near the surface of an ovary multiply by mitosis to form diploid oogonia  The oogonia grow to form primary oocytes (2n)  Each primary oocyte is surrounded by a layer of follicle cells that nourish the developing oocyte and secrete female hormones.The primary oocyte and these accessory cells make up a primary follicle.  As foetal development continues,all primary oocytes undergo meiosis but stop at prophase I of meiosis I.
  13. 13. The secondary oocyte starts meiosis II which progresses until metaphase II.The first polar body may also complete meiosis II to form two polar bodies. At this stage,the secondary oocyte,together with the layers of follicle cells around it,is now called a secondary follicle. The secondary oocyte starts to grow in the follicle.The secondary follicle increases in size ad mature to form Grafiaan follicle. Later the ovarian wall and the Grafiann follicle then rupture,releasing the secondary oocyte or egg into the Fallopian tube.
  14. 14. 1)The germinal epithelial cells divide repeatedly until many diploid oogonia are formed. 2. The oogonia grow to form primary oocytes that surrounded by a layer of follicle cells. 3)The oocytes undergoes the first meiotic division to become a secondary oocyte and a first polar body.(haploid) 4)The follicle cells surrounding the primary focille develop into the secondary follicle. The follicle layer of the secondary oocyte thickens and folds to form the Graafian follicle 5. The secondary oocytes that has complete meiosis II when it is fertilized by a sperm(n).The final product of meiosis II is the ovum and the seond polar body
  15. 15. Visual of how oogenesis happens!
  16. 16. Similarities & Differences between Spermatogenesis and Oogenesis Both processes occur in the reproductive organs. Both involve the process of meiosis. Both produce haploid gametes that are involved in fertilisation Similarities
  17. 17. ASPECT SPERMATOGENESIS OOGENESIS Site of process In the testes In the ovaries Cells produced Sperm Ova or egg. Size of cells Small Big Cell structure Consist of the head , middle pieces and tail Round Number of gamates produced. Four funcional cells One funcional cells and three non-funcional polar bodies. The differences between spermatogenesis and oogenesis
  18. 18. ASPECT SPERMATOGENESIS OOGENSIS Meiosis Occurs continuously Not continues. Stops at meiosis I. Meiosis II occurs only if sperm penetrates the secondary oocyte. Density of organelles Many mitochondria, less cytoplasm. Fewer mitochondria, more cytoplasm. Parent cells Infinite number of cells can become sperm. Limited number of cells can become ova.
  19. 19. THALE NA MASS!

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