Reproduction

1. Reproduction

2. Reproduction - Definition • The process by which living organisms give birth to or produce off springs of their own kind.

3. Significance of Reproduction • Continuation of life • Perpetuation of species. • Replacement of the population killed or dead. • Maintenance of the population of infants, young and old. • Introduction of new variations. • Transfer of variations.

4. DNA – The blue Print of life. • It stores all information of the structural and functional organization of each individual. • DNA replicates to form new copies. • Mutations during DNA replication brings variation- such variations lead to evolution of new species.

5. Def: Differences in morphological, physiological and other traits or characteristics of individuals belonging to the same organism, race or family Variation – Its Definition and Importance

6. Variation – Its Importance • Pre-Adaptation – Variations prepare some organisms in a population to adapt to the new environmental condition. Ex: mosquitoes getting pre-adapted to new repellents. • Individuality. • Struggle for Existence • Improvement of Varieties. • Evolution

7. Types of reproduction Asexual Sexual

8. Asexual Reproduction • Single Parent • No gametes or sex cells produced. • All cellular divisions are mitotic. • All the off springs are genetically similar. • It involves rapid multiplication. • It occurs in lower invertebrates, in unicellular organisms

9. Types of Asexual reproduction • Fission • Budding • Fragmentation • Regeneration • Spore formation • Vegetative propagation.

10. Fission • Binary Fission The splitting of an organism into two. Occurs in favorable conditions. Ex: Amoeba, Paramecium

11. Multiple Fission- One unicellular organism divides and splits to form a number of daughter individuals. Ex: Plasmodium Fission

12. Formation of an outgrowth from an organism to form a new individual. Ex: Yeast, Hydra. Budding

13. The process of breaking up of the body of an organism into two or more parts , each of which grows into a complete new individual. Ex: Spirogyra Fragmentation

14. It is the ability to repair the injured parts and replace the ones lost through accident or autotomy (self amputation) Ex: Planaria, tail in wall lizard and arms in star fish) Regeneration (re-again, generare-to beget

15. Spores are tiny unicellular asexual reproductive bodies which get dispersed to form new individuals on germination. Ex: Rhizopus (bread mould) Spore Formation

16. Vegetative Propagation • Def: The process by which plants reproduce asexually through vegetative parts – the stem, leaves and roots. They are of the following kinds:- • Cutting • Layering • Grafting • Budding

17. Cutting

18. Layering • A branch of a plant is buried into soil. The underground stem produces roots

19. Grafting • Grafting a scion having desired characteristics on the stalk.

20. Budding Formation of an outgrowth from an organism to form a new individual. Ex: Yeast, Hydra

21. Sexual Reproduction Bi-parental Cell division include meiosis (reduction division) Gametes are produced. Fertilization- Fusion of male and female reproductive cells. Formation of Zygote Brings about a number of variations

22. Significance of Sexual Reproduction • Variations. • Maintains the vigour and vitality of the individual. • Brings about uniformity in population. • Leads to evolution.

23. Sexual Reproduction in Flowering Plants

24. Structure of a flower

25. Parts of a flower • Sepals-green colored, outside whorl for protection of buds and photosynthesis. • Petals- brilliantly colored, penultimate whorl, helps in pollination.

26. Parts of a flower • Stamens- Male reproductive part of a flower. It has a long filament and anther lobes which contain the male sex cells (gametes) called pollen grains.

27. Parts of a flower • Pistil- The female reproductive part of a flower which contains the female sex cells (gametes) called ovules. The other parts are stigma and style.

28. Pollination • The process of transfer of pollen grains from the anther to the stigma by various pollinating agents.

29. Fertilization- Stages or events • The deposition of pollen on stigma.

30. Fertilization- Stages or events • The exine of the pollen breaks down and the inner thin intine grows into a long tube carrying in it two nuclei- generative and tube nuclei.

31. Fertilization- Stages or events • The pollen tube secretes an enzyme that dissolves its way down the style and reaches the ovary.

32. Fertilization- Stages or events During this time the following changes are observed the ovary: • The embryo sac containing 8 nuclei is formed. The embryo sac contains 2 synergids, 1 egg cell, three antipodal cells and 2 polar nuclei. It gets surrounded by two envelopes called integuments.

33. The pollen tube enters the embryo sac from the micropilar end. One of the male nuclei fuses with the egg to form the zygote. This process is calledSyngamy. The other male nucleus fuses with the 2 polar nuclei to form Endosperm. This process is calledTriple Fusion Syngamy+ Triple Fusion= Double fertilization. Fertilization- Stages or events

34. Seed and Fruit Formation • The embryo takes nourishment from the nutritive tissue called nucellus. • The food inside the seed is stored in the endosperm or the cotyledons. • The two integuments form the coat. • The ovule thus becomes a seed.

35. Seed and Fruit Formation • The ovary around the seed gets either dry or fleshy as it ripens. This ripened ovary is called fruit. • Seed helps in easy dispersal, perennation and delayed germination.

36. Seed Germination • The seed absorb water from the soil. This process is called Imbibition. • The seed coat breaks open and the radicle (forming roots) and plumule (forming shoot) germinate.

37. Sexual Reproduction in Human Beings

38. Puberty- The stage of Sexual Maturity Puberty in Males The following changes are observed in a male with the onset of Puberty. • Hairs in arm pits, chest and genital area, growth of moustache and beards. • Skin becomes oily, pimples develop • Aware of his masculinity. • Low pitched voice begins to develop. • Broadening of shoulders.

39. Puberty- The stage of Sexual Maturity Puberty in Females The following changes are observed in a females with the onset of Puberty. • Hairs in arm pits and genital area. • Skin becomes oily, pimples develop. • Aware of her feminity. • High pitched voice begins to develop. • Onset of Menstrual cycle. • Enlargement of breasts. • Deposition of fat around the hip area.

40. The Male reproductive System

41. The Male reproductive System • The male reproductive system consists of two main parts: • The primary reproductive organs- which are concerned with the production of male sex cells (gamete) called sperms. The Testisis theprimary reproductive organs.

42. The Male reproductive System Testis –Structure • The male gonads which produce sperms and secrete hormone testosterone. • Present in a bag of loose skin called scrotal sac. • The temperature of scrotal sac is 2 deg. Less than the body temperature. This low temperature helps in Spermatogenesis ( the process of producing sperms)

43. Testis –Structure and Function • The sperms are produced in the seminiferous tubules in testis. The sex cells are motile with ahead and a long tail. • The Leydig Cells secrete the hormone Testosterone that influences the process of spermatogenesis. • Mature sperms are stored in the coiled structure called epididymis.

44. Secondary or Accessory Reproductive organs in males • Vas deferens- the sperm duct which carries sperms from the testis. • Vas deferens becomes the sperm duct when it enters the abdominal cavity. • Into the sperm duct secretion from 3 glands – Prostrate, seminal vesicle and Cowper’s gland are drained which provide the medium for sperms to travel freely. The sperms + the secretions from these three glands is a fluid called SEMEN.

45. Secondary or Accessory Reproductive organs in males • The sperm duct also receives the urine from the urinary bladder. Thus the sperm duct has dual function – ejaculation of semen (during copulation) and to excrete urine (during micturition). • Penis- The erectile organ richly supplied with blood vessels (which get filled up with blood during excitation). This structure is used by males to deposit sperms into the female genital tract during copulation ( the process of sexual intercourse)

46. The Female reproductive System

47. The Female reproductive System • The female reproductive system consists of two main parts: • The primary reproductive organs- which are concerned with the production of female sex cells (gamete) called ova. The Ovariesare theprimary reproductive organs.

48. The Female reproductive System Ovaries- Structure • A pair of almond shaped glands present near the kidneys. • Ovaries contain thousands of immature stages of egg called Follicles. • With the onset of pubertyovaries begin to form one mature follicle with ovum every 28 days alternatively. • Each ovary is lined by germinal epithelium which produces ova. • Ovaries also secrete two hormones- estrogen and progesterone.

49. Secondary or Accessory Reproductive organs in Females • Fallopian Tubes: Also called Oviducts these are curved tubular structures lined by ciliated columnar epithelial cells. The proximal end (part close to the ovaries) is funnel shaped (with finger like projections) called the infundibulum. Mature ovum is discharged every 14th day of the reproductive cycle into the fallopian tube. The fallopian tube is the site for fertilization with a sperm.

50. Secondary or Accessory Reproductive organs in Females • Uterus – The muscular thick walled bag like organ where the embryo develops during the time of pregnancy. The inner lining of the uterine wall is called Endometrium. The lower end of the uterus is called the cervix.