Unit X: The Life Process of Reproduction

I. Cell Division Definition: the process by which a cell divides, producing 2 daughter cells identical to the parent cell. A. Nuclear and Cytoplasmic Division 1. Mitosis: process by which the nucleus divides during cell division -when the nucleus divides, each daughter nucleus receives a complete copy of the genetic material 2. Cytokinesis: the cytoplasm and organelles of the old cell are divided between the daughter cells.

B. Structure of the Chromosome 1. Composed of DNA (deoxyribonucleic acid) 2. Chromatin: the material of the chromosomes in the form of long, thin threads, form when the cell is not going to divide 3. Each chromosome contains a number of genes (units of hereditary material)

Cell Division 1. Occurs in cell growth and asexual reproduction 2. Each daughter cell gets an exact copy of the genetic information from the parent cell 3. Daughter cells are clones of the parent cell

D. Chromosome number 1. Diploid (2n) number: the full number of chromosomes characteristic of the species (humans =46) 2. Haploid (n) number: having half the diploid number of chromosomes, also called monoploid (humans=23) 3. Cancer: uncontrolled mitosis of cells

II. Asexual reproduction Definition: a type of reproduction in which there is only one parent and all offspring are genetically identical to the parent (clones) A. Types of Asexual reproduction 1. Binary Fission 2. Budding 3. Regeneration 4. Sporulation 5. Vegetative Propagation

II. Meiosis Definition: formation of a gamete with the haploid (monoploid) number of chromosomes also called reduction division Parent cell will divide twice to yield 4 daughter cells

A Comparison of Mitosis and Meiosis Point of Comparing Mitosis Meiosis # of Divisions One Two Recombination No Yes Number of daughter cells Four Genetic makeup Clones Much different Function Growth and repair Sperm and egg for reproduction

III. Gametogenesis Definition: process by which gametes (sex cells) develop in gonads -gametes: cells that provide the nuclear material for sexual reproduction A. Oogenesis: production of eggs (ovum) in the ovaries -During meiosis, 3 polar bodies and 1 mature ovum (egg) are produced -polar bodies disintegrate and die

B. Spermatogenesis Definition: production of sperm in the testes -in 1 meiotic division, 4 haploid pre-sperm are produced -Pre-sperm then undergo hormonal changes to become flagellated and motile

C. Fertilization Definition: union of egg and sperm -results in a diploid zygote zygote: diploid cell resulting from fertilization, restores the species number of chromosomes

Internal Fertilization Definition: gametes fuse inside the body of a female -limited to terrestrial animals -chances of fertilization of the egg increases -requires specialized sex organs to transfer the sperm into the female’s body -fewer eggs are produced, but still a large number of sperm are released to ensure fertilization

Development Definition: complex series of changes that occur after fertilization and give rise to the adult organism -embryo: organism in the early stages of development A. Cleavage: fertilized egg divides into 2 cells, then 4 and so on -no cell growth during cleavages -converts a single, large fertilized egg into many small cells -cells then undergo a rearrangement into a hollow ball of cells (blastula) or blastocyst

IV: Reproduction in Humans A. Humans 1. Testes are the gonads a) sperm cells (male gametes) are produced in the testes b) secrete testosterone 2. Testes are held in the scrotum a) keeps the temperature of the testes slightly lower than the rest of the body -necessary for normal sperm production 3. Semen: mixture of fluids from glands and sperm

B. Female Reproductive System 1. Ovaries are the gonads a) produce eggs (female gametes) b) secrete estrogen, progesterone 2. Eggs develop in follicles 3. Ovulation: an egg matures in a follicle and is released from the ovary -first occurs at puberty -ends at menopause 4. Oviduct (Fallopian Tube): tube connected to the ovary containing ciliated cells that create a current that draws the released egg down the oviduct -where fertilization occurs

B. female reproductive system 5. Uterus: thick-walled, muscular, pear-shaped organ -where development of the embryo occurs 6. Cervix: narrow neck of the uterus 7. Vagina (birth canal): leads to the outside of the body

II. Stages of the female menstrual cycle (28 days) A. Follicle Stage: 1. FSH is secreted by the pituitary a) causes several follicles in the ovaries to begin developing 2. As the follicle develops, it secretes estrogen which stimulates the uterine lining to thicken with mucus and a rich supply of blood vessels 3. Prepares the body for possible pregnancy

B. Ovulation- high level of estrogen in the blood causes the pituitary to decrease production of FSH and start secreting LH (luteinizing hormone) -the increase in LH causes ovulation C. Corpus Luteum Stage 1. LH causes the ruptured follicle to fill with cells forming a yellow body (corpus luteum) 2. Corpus luteum secretes progesterone which maintains the continued growth of the uterine lining -prevents the development of new follicles by inhibiting the release of FSH

D. Menstruation 1. If fertilization does not occur, the concentration of LH decreases and the corpus luteum breaks down 2. Decrease in the level of progesterone, thickened lining of the uterus breaks down 3. Extra layers of lining, unfertilized egg, and blood pass out of the body through the vagina 4. Estrogen level decreases 5. FSH increases which causes another follicle to start maturing and the cycle starts all over again

Fertilization A. Fertilization normally occurs in the upper end of the oviduct, generally within 24 hours of ovulation. - If Fertilization does not occur, the egg will deteriorate and be shed with the menstrual flow. -- If fertilization is successful, the resulting zygote undergoes the first of several cleavage divisions it will experience over the next 6 to 10 days as it continues down the Oviduct to the Uterus.

Fertilization - If two eggs are fertilized  Fraternal Twins --- When (the Embryo) reaches the Uterus, it implants itself into the blood-vessel rich lining and begins to establish the placental connection. - If two eggs are fertilized  Fraternal Twins --If one egg is fertilized and the zygote separates during cleavage  Identical Twins

Development A. Prenatal Development – All the processes of embryonic development that occur before birth. - Tissues of the embryo and the mother grow together to form the Placenta. This allows nutrients and oxygen to pass from mother to embryo. - The Amnion is a membrane that surrounds the embryo and is filled with Amniotic Fluid (this shields the embryo from mechanical shock).

Development - Umbilical Cord contains blood vessels that carry blood between the Embryo and the Placenta. Nutrients and Oxygen  Embryo Wastes and Carbon Dioxide  Mom

Development B. Birth – Occurs after a period of development known as the Gestation Period. (In humans this is about 9 months) - Strong Contractions of the Uterus force the baby through the Cervix and Birth Canal (Vagina) to the outside of the body. -The baby begins to breath, eat, and excrete waste on its own.