1. Unit X: The Life Process of Reproduction

2. Cell Division Definition: the process by which a cell divides
Nuclear and Cytoplasmic Division
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
Cytokinesis: the cytoplasm and organelles of the old cell are divided between the daughter cells.

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

4. Stages of Cell Division
Interphase:
Phase between divisions
growth of the cell
replication of the DNA

5. Prophase
Thickening of chromatin material in the nucleus to form chromosomes
chromosomes can be seen and are rod-like in shape
nuclear membrane breaks apart
centrioles begin to move towards opposite ends(poles) of the cell
spindle fibers appear and extend between centrioles

6. metaphase Chromosomes line up along the equator (middle) of the cell
Each chromosome is attached to a spindle fiber at the centromere

7. Anaphase Separation of the chromatids from each other
each chromatid moves away from the equator and moves toward the poles

8. Telophase
Tightly coiled chromosomes unfold and lengthen (become chromatin)
2 new nuclear membranes form around chromatids
spindle fibers disappear
Cytokinesis takes place:
-in animals: by pinching in of the cell membrane
-in plants: by the formation of the cell plate

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

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

11. 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

12. 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

13. Stage I Interphase I: the DNA replicates itself Prophase I:
a) fine threads of chromatin shorten and thicken
b) chromosomes appear
c) homologous chromosomes come together in pairs

14. Stage I
since the chromosomes are so close, they can exchange parts (crossing over)
-this leads to variety in the offspring

15. Metaphase I:
chromosome pairs line up down the middle of the cell

16. Stage I
Anaphase I:
2 chromosomes from each tetrad move toward the opposite poles
and separate of a tetrad

17. Stage I
Telophase I:
2 daughter cells are produced with the haploid number of chromosomes

18. stage II No DNA replication, phases are exactly like mitosis
division of the cytoplasm and separation of chromatids of each chromosome
produces 4 daughter cells each with the haploid number of chromosomes (sex cells)

19. More on Meiosis A. occurs in the production of sex cells (gametes)
B. 2 cell divisions
C. daughter cells contain one-half the number of the chromosomes the parent possesses

20. A Comparison of Mitosis and Meiosis
Point of Comparing
Mitosis
Meiosis
# of Divisions
One
Two
Recombination
(crossover) No
Yes
Number of daughter cells
Four
Genetic makeup
Clones
Much different
Function
Growth,repair, & asexual reproduction
Sperm and egg for sexual reproduction

21. Gametogenesis
Definition: process by which gametes (sex cells) develop in gonads
-gametes: cells that provide the nuclear material for sexual reproduction
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

22. 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

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

24. Types of Fertilization
1. External Fertilization: gametes fuse outside the body of the female
-limited to aquatic organisms
-fertilization occurs in the water once each parent has released its sex cells
Many hazards:
-egg and sperm may not meet
-eggs may be eaten
-eggs may die due to a changing environment
-a large number of eggs and sperm are released to overcome these hazards
-example: fish

25. 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

26. 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
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)

27. Types of Development External development in water
-nourishment is provided by the yolk
-oxygen diffuses into the organism
-wastes diffuse from the embryo into the water
-little or no care of the young
-small number of young survive and mature

28. 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

29. 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

30. 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

31. Fertilization
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.

32. 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

33. Development
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).

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

35. Development
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.