ASEXUAL/SEXUAL REPRODUCTION MITOSIS/MEIOSIS ASEXUAL/SEXUAL REPRODUCTION HUMAN REPRODUCTION

REPRODUCTION The process by which all living organisms perpetuate themselves (production of a new organism) i.e ‘produce more of themselves’ to ensure species continuation

KEY TERMS Diploid cell- Haploid cell - Gamete- somatic cells (normal body cell) with full complement of chromosomes represented as 2n. Humans have 23 pairs/46 chromosomes Haploid cell - cell containing 1/2 the number of chromosomes, represented as ’n’. Found usually in reproductive cells Gamete- reproductive cell (egg/ovum) and (sperm/spermatozoon) formed as a result of meiosis, in which the number of chromosomes is halved

KEY TERMS different forms of the same gene. Zygote- the diploid cell formed when the sperm and egg fuse in fertilization Homologous chromosomes - chromosomes which are similar in length, position of the genes and centromeres. homologous chromosomes carry genes for the same traits or character, even though the alleles may be different. One comes from each parent- mother (egg) and father (sperm) Alleles- different forms of the same gene.

MEIOSIS

MITOSIS

MITOSIS vs MEIOSIS

Asexual Reproduction The production of new individuals from a single parent without the production of gametes the offspring (daughter cell) is genetically identical to the parent cell

Types of asexual reproduction

sexual vs asexual reproduction

Sexual Reproduction Sexual reproduction is the fusion of two haploid gametes, usually a male and a female gamete, to form one diploid cell, the zygote.

The menstrual cycle in women is a recurring process in which the lining of the uterus is prepared for pregnancy, and if pregnancy does not happen, the lining is shed at menstruation. The cycle lasts about 28 days.

Menstruation Usually, one egg is released from an ovary every month. Before the egg is released, the lining of the uterus becomes thick and spongy to prepares for a fertilised egg. It is full of tiny blood vessels, ready to supply the embryo with food and oxygen if it should arrive. If the egg is not fertilised, it is dead by the time it reaches the uterus.

Is does not sink into the spongy wall, but continues onwards, down through the vagina. As the spongy lining is not needed now it gradually disintegrates and is slowly lost through the vagina. This is called menstruation, or period and it last for about 5 days.