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Sexual Reproduction

Sexual Reproduction. Ch 19.1 page 513 . Sexual reproduction - A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents . The benefits of sexual reproduction are:

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Sexual Reproduction

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  1. Sexual Reproduction Ch 19.1 page 513

  2. Sexual reproduction - A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents. The benefits of sexual reproduction are: • Natural Variation – evolve to meet new challenges • Production of many different gene combinations • Better combinations tend to survive and reproduce – strengthening the species The disadvantages of sexual reproduction are: • Relies on the sex cells meeting • It takes longer • Normally one is produced at one time.

  3. Somatic cells - Body cells in multicellular organism except an egg or sperm - 46 chromosomes - Diploid (paired) condition - 23 pairs of chromosomes • Gamete cells - Sex cells; ovum (egg) for females and sperm for males; these cells have only 23 single chromosomes each - Haploid (half) condition

  4. Meiotic division - Meiosis is a special method of cell division. It forms gametes cells in the gonads - testes and ovaries. Contain only half of the genetic material of the parent cell – allows for combination of chromosomes in offspring. • Mitotic division - Mitosis occurs in all regular cells. A cell divides to produce two new cells that are genetically identical to the original cell – replaces itself.

  5. Male Reproductive System • Testes - The male gonads, which produce sperm and secrete male sex hormones. Located in the scrotal sac. • Scrotum - skin-covered pouch in the groin divided into two sacs, each containing a testis and an epididymis - regulates the temperature to lower than normal body temperature. • Epididymis - coiled duct on the top and at the side of the testis that stores sperm before emission.

  6. vas Deferens - tube that carries sperm from the epididymis to the urethra • Testosterone - the most important of the male sex hormones. Both males and females have it, but the additional testosterone in males stimulates the growth of the male sex organs in the foetus and the development of the male sex characteristics during puberty • Seminal vesicles secrete sugar solution; providing both a liquid medium for the sperm and nutrients for propulsion • Cowper's gland - secretion cleanses the urethra of urine • Urethra - tube through which semen passes during coitus; transport of urine to exterior

  7. Prostate gland - releases alkaline solution (to neutralise female secretions) and blocks the release of urine during coitus • Erectile tissue - containing blood sinuses - retention of blood in the sinuses causes the spongy tissues to harden and thus the penis to become erect enabling coitus • Penis - the male organ that transfers sperm to a female and that carries urine out of the body. • Glans penis - the conical mass of erectile tissue that forms the head of the penis • Foreskin a retractable double-layered fold of skin and mucous membrane that covers and protects the glans penis

  8. Female Reproductive System • Ovaries - located one on each side of the uterus in the female pelvis, functioning to secrete estrogen and progesterone and to release ova • Fallopian tubes - tubes which carry eggs from the ovaries to the uterus and which provides the place where fertilization occurs - not connected directly to the ovary • Uterus - organ of the female reproductive system in which a fertilized egg can develop

  9. Cervix - neck-like opening to the uterus • Vagina - the lower part of the female reproductive tract, in the human female reproductive system, a canal that leads from the uterus to the outside of the body • Labia - folds of tissue on either side of the vaginal opening; known as the labia majora and labia minora • Clitoris - a female sexual organ homologous to the penis - located anterior to the urethra • Vulva - external female genitalia; includes the labia, hymen, clitoris, and the vaginal orifice

  10. Menstruation/Ovulation • Menstruation - phase of the menstrual cycle during which the lining of the uterus, along with blood and the unfertilized egg, is discharged through the vagina • The first day of the menstrual cycle (28 days) is also the first day of the menstrual period and that is the very first day bright red blood is observed. Brown spotting is not considered a menstrual period • Ovulation- the expulsion of an ovum from the ovary (usually midway in the menstrual cycle – day 14)

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