Theme: REPRODUCTION

PLAN OF LECTURE

1. THE FORMS OF REPRODUCTION

2. ASEXUAL REPRODUCTION

3. SEXUAL REPRODUCTION

4. GAMETOGENESIS

5. FERTILISATION

STUDENTS' INDEPENDENT STUDY PROGRAM1. Evolution of the forms of reproduction: asexual and

sexual reproduction.2. Asexual reproduction in unicellular and multicellular

organisms. 3. Sexual reproduction in unicellular and multicellular

organisms.4. Spermatogenesis and oogenesis.5. Morphogenetical specialisation of sex cells: a sperm

and an ovum6. Fertilisation: an egg's activation and syngamy.8. Natural and artificial parthenogenesis.9. Biological peculiarities of human reproduction.

Applicable literature materials:

Medical biology / K. L. Lasarev – Simferopol: IAD CSMU, 2002. pp. 58 - 74.

Reproduction is the method by which individuals give rise to other individuals of same type. Reproduction can be asexual and sexual. At an asexual reproduction the genetic information does not vary. In a basis of an asexual reproduction the mitosis lays.

SEXUAL REPRODUCTION

AT SEXUAL REPRODUCTION THE GENETIC INFORMATION VARIES AS A RESULT OF COMBINATION.

IN A BASIS OF SEXUAL REPRODUCTION THE MEIOSIS LAYS AS A SOURCE COMBINATION OF VARIABILITY.

TYPES OF ASEXUAL REPRODUCTION IN SINGLECELLULAR ORGANISMS

1.BINARY FISSION 2.BUDDING3.ENDODIOGENY4.SHIZOGONY (OR MULTIPLE

FISSION)5.SPOROGONY

1.BINARY FISSION – PARENT CELL SPLITS IN TWO

CELLS.

ENDODIOGENY –IN PARENT CELL FORMS ONLY TWO DAUGHTER CELLS BY INTERNAL BUDDING.

BUDDING - AFTER KARYOKINESIS THE SPECIAL REGION IN PARENT CELL RAPID GROWS AND ORGANIZED INTO NEW ORGANISM.

Sporogony - is reproduction by the spores, if its are the result of mitosis.

• Shizogony (or multiple fission) - in parent cell forms a great amount of daughter cells.

THE TYPES OF ASEXUAL REPRODUCTION IN MULTICELLULAR ORGANISMS

The types of asexual reproduction in multicellular organisms are:

1) Vegetative (regeneration) - a group of cells from the parent organism separates and new organism forms from its.

2) Polyembrionya - the production of two or more embrions from the one zygote.

3) Sporogony - is reproduction by the spores, if its are the result of mitosis.

As result of asexual reproduction is that offspring is genetically identical to its parent.

VEGETATIVE (REGENERATION)

POLYEMBRIONYA

The Types of Sexual Reproduction in Single-cellular Organisms

• The types of sexual reproduction in singlecellular organisms are:

1)Conjugation - a cytoplasm bridge forms between two organisms, the nuclei transfer across this bridge and after exchange ones forms a new gene combination but no new offspring.

2)Copulation - two individuals acquire the gametes properties, fuse and form a zygote the life of a new individual begins.

Types of reproduction on the value of gametes

• Isogamy - observes at the first stages of sexual reproduction, in which the gametes morphological differentiation doesn't present.

• Anisogamy - is such period of gamete differentiation in which they become some different from each other by their sizes: some of them are smaller and another are the largest.

• Ovogamy - is the form of anisogamy in which gametes are very different from each other.

Isogamy -

Anisogamy -

Ovogamy -

Conjugation -

The Types of Sexual Reproduction in Multicellular Organisms

• In multicellular organism sexual reproduction may be two forms:

• 1) with fertilisation and • 2) without fertilisation.• Parthenogenesis is the types of

sexual reproduction when development of new organism from an egg without fertilisation.

PARTHENOGENESIS

GAMETOGENESIS (making gametes) –

the development of the male and female sex cells, or gametes

REPRODUCTIVE CELLS OR GAMETES

GAMETES ARE FORMED AFTER COMPLETION OF THE PROCESS OF MEIOSIS, WHICH HALVES THE NUMBER OF CHROMOSOMES. MALE GAMETES ARE MOTILE, WHEREAS FEMALE GAMETES ARE LARGER AND ARE STATIONARY; THE FUNCTION OF THE LATTER IS TO STORE SUPPLIES OF FOOD FOR THE DEVELOPING EMBRYO.

Gametogenesis is divided into four periods: 1) reproduction (multiplication), 2) growing, 3) maturation and 4) formation.

TESTIS

SPERMATOGENESISSPERMATOZOON DEVELOPMENT BEGINS IN SPERMATOGONIA. A DIPLOID SPERMATOGONIUM DIVIDES MITOTICALLY AND BECOMES A PRIMARY SPERMATOCYTE AS IT MOVES TOWARD THE LUMEN OF THE TUBULE. IN MEIOSIS-I, EACH SPERMATOGONIUM HALVES ITS GENETICALLY MATERIAL TO FORM TWO SECONDARY SPERMATOCYTES.

In meiosis II, each secondary spermatocyte divides to yield two equal - sized spermatids. Therefore, each cell undergoing meiosis in male can potentially divide to yield a maximum of four spermatids.

Spermatogenesis

SPERMATOZOON STRUCURE THE HEAD HAS A HAPLOID NUCLEUS. AN ACROSOME - A SMALL BUMP ON THE FRONT END OF THE HEAD CONTAINS ENZYMES THAT HELP THE CELL PENETRATE THE OVUM'S OUTER MEMBRANE. THE BODY OR MIDPIECE HAS MITOCHONDRIA TO PROVIDE THE CELL ENERGY AND CENTRIOLES. A TAIL CONSISTS OF MICROTUBULES FOR MOVING.

EACH SPERMATOZOON CONSISTS OF:

1)A HEAD REGION;

2) A BODY OR MIDPIECE;

3) A TAIL OR FLAGELLUM.

OOGENESIS - (EGG-MAKING) BEGINS IN A DIPLOID OOGONIUM. AN OOGONIUM ACCUMULATES CYTOPLASM AND REPLICATES ITS CHROMOSOMES, BECOMING A PRIMARY OOCYTE. IN MEIOSIS I, THE PRIMARY OOCYTE DIVIDES TO FORM A SMALL POLAR BODY AND A LARGE, HAPLOID SECONDARY OOCYTE.

IN MEIOSIS II, THE SECONDARY OOCYTE DIVIDES TO YIELD ANOTHER SMALL POLAR BODY AND A MATURE OVUM. THEREFORE, EACH CELL UNDERGOING MEIOSIS IN FEMALE CAN POTENTIALLY DIVIDE TO YIELD MAXIMUM OF FOUR CELLS, ONLY ONE OF WHICH WILL BECOME THE OVUM.

Ovary

OOGENESIS

AN OVUM (THE NAME FOR AN EGG CELL AFTER IT LEAVES AN OVARY) IS ENORMOUS IN SIZE. CORONA RADIATA OUTSIDE THE CELL CONSISTS OF THE GREAT AMOUNT OF FOLLICULAR CELLS, WHICH PRODUCE FOLLICULAR FLUID FOR ATTRACTING THE SPERMS.

Corona radiataZona pellucidaNucleusCytoplasm withvarious inclusionbodies, includingmitochondria

REPRESENTATIONOF HUMAN EGG

Ovulation - dischange (going out) of a secondary oocyte from a follicule of the ovary.

FERTILISATION

The fusion of haploid gametes to form a new diploid cell is called fertilisation . During fertilisation two processes take place: 1. EGG'S ACTIVATION 2. SYNGAMY

EGG'S ACTIVATION

EGG'S ACTIVATION - A WAVE OF CHEMICAL REACTIONS SWEEPS ACROSS THE SURFACE OF THE NEWLY AROUSED EGG, CAUSING THAT SURFACE TO HARDEN AND PRESENT A BARRIER TO THE ENTRY OF ANY ADDITIONAL SPERM. THE EGG'S OXYGEN CONSUMPTION SKYROCKETS, AS DOES ITS RATE OF PROTEIN SYNTHESIS.

EGG'S ACTIVATION

FERTILIZATION

SYNGAMY

- MALE AND FEMALE HAPLOID NUCLEI CONVERGE AND FUSE TO FORM THE ZYGOTE'S SINGLE DIPLOID NUCLEUS.

SYNGAMY

SYNGAMY

As a result of a fertilization the zygote will be derivated, the embryo begins to develop.

Toxic exposures such as alcohol, cocaine ets., may change the process of normal gametogenesis resulting in genetic material mutation in sex cells. The alteration of these cells by toxic substances provokes birth defects.

Key words and phrases:

mitosis, asexual and sexual reproduction, generation replacement, cloning, sex cells, gametogenesis, meiosis, biological peculiarities of human reproduction, endogony, shizogony, budding, sporogony, polyembrionya, sexual reproduction, conjugation, copulation, parthenogenesis, oogenesis, polar body, primary oocyte, secondary oocyte, spermatogenesis, primary spermatocyte, secondary spermatocyte, spermatid, ovum, spermatozoon, ovary, ovulation, fertilisation, syngamy, zygote .

THE END